Porous membrane and method of its production

FIELD: process engineering.

SUBSTANCE: invention relates to production of porous membrane suitable for use in electrochemical devices such as various storage batteries, capacitors, etc. Porous membrane comprises cellulose fibres including 5 wt % or more of cellulose fibres (per sum of total mass thereof) with diameter of 1 mcm or more and features tensile strength of 50 Nm/g or larger and/or tenacity of 0.40 kN/m or larger.

EFFECT: possibility of use as an electrochemical device separator with low specific IR.

21 cl, 6 ex, 1 tbl

For the present invention claims the priority of application for a patent of Japan No. 2011-226269, filed October 13, 2011, the description of which is incorporated herein by reference.

The technical field to which the invention relates.

The present invention relates to a porous membrane and method of reception. In particular, the present invention relates to a porous membrane obtained from cellulose and suitable for use as a separator in an electrochemical device and to a method for producing such a membrane.

When describing the present invention the electrochemical device should be understood as an electrochemical device provided with a positive electrode, negative electrode and separator. As examples of the specified device can be mentioned, for example, the secondary batteries of different types, such as lithium-ion secondary battery and lithium polymer battery; different types of capacitors such as aluminum electrolytic capacitors, electric double-layer capacitors and lithium ion capacitors; and the like.

The level of technology

Recently, in connection with the environmental problems related to reduction of emissions of CO₂the decrease of fossil fuel resources and the like, have increased presentillustrated as an energy source. So, for example, in the automotive industry is actively developing electric vehicles that use of the secondary battery. In addition, secondary batteries are also known in connection with the effective use of alternative energy sources such as solar or wind energy.

Currently, lithium-ion secondary batteries are typically used as secondary batteries for the propulsion of electric vehicles, due to their dependence between power and specific energy. On the other hand, various companies have focused on developing batteries for the next generation, with high specific energy access, security and the like. Batteries next generation is a region with a high prospect of future growth in the market.

On the other hand, in the secondary battery is different from the lithium-ion secondary batteries, primary batteries, capacitors (tanks), and the like, are used separators consisting of paper, nonwoven fabric, porous film or the like. Characteristics required for separators are usually protection against short circuit between positive and negative electrodes, chemical stability with respect to the electrolytic solution, a small internal specific resistivity is our actions and the like. The above characteristics are universal and are required of all separators, regardless of their type, although their quantitative response may differ depending on the device.

In separators of almost all lithium-ion secondary batteries use a porous membrane made of polymeric organic compounds, such as polypropylene, polyethylene or the like. The above-mentioned porous membrane have certain characteristics, suitable for lithium-ion secondary batteries. For example, we can mention the following characteristics:

(1) Chemical stability in relation to the electrolytic solution and the absence of catastrophic damage due to the separator;

(2) the thickness of the separator can be easily controlled during manufacture, and for this reason can be obtained separators that meet the diverse needs;

(3) you Can get pores of reduced diameter, which leads to excellent shielding characteristics of lithium and the almost complete absence of a short circuit caused by lithium dendrites;

(4) When thermal runaway of lithium-ion secondary battery, at first it can be controlled by the melting of polypropylene or polyethylene and, as a consequence, the reduction of the pore.

However, traditional research is of lithium ion secondary batteries and can't identify the cause, underlying the phenomenon of thermal runaway. Various firms and investigated this phenomenon, and suggested methods of eliminating the risk of thermal runaway for various materials used in the secondary battery, using empirical methods under given conditions. Development of materials suitable for vehicles with enhanced safety, through the prism clarify the principles of the phenomenon of thermal runaway, with a subsequent substantiation General method of evaluation of this phenomenon. It can be expected that in this way the problems related to security, will be overcome.

On the other hand, the second problem, when using secondary batteries in vehicles, is their cost. The separator is a material, which accounts for about 20% of the cost of the battery, and existing conditions require additional cost.

For example, in the field of rechargeable transport units, such as electric vehicles, as well as in the field of portable electronic terminals, such as mobile phones, require device of accumulating electric energy, which has improved the capacity of the accumulated energy per unit volume to ensure device operation over a large period of time even when little is volume. As an example, the above mentioned device accumulation of electric energy can be mentioned electric double layer capacitor, in which the electrolyte is dissolved in the electrolytic solution, is adsorbed on the electrode, and the electric energy is accumulated on the surface of section (electric double layer) formed between the electrolyte and the electrode.

The main purpose of the separators in the electric double-layer capacitors is to protect against short circuit of the electrodes (separation), not impeding the movement of ions in the electrolytic solution (low internal resistance) and the like. However, the above-mentioned porous membrane have a high density and for this reason tend to increase the internal resistivity. On the other hand, it is known that as the separator condenser are also used non-woven materials, but there are problems: when to maintain the characteristics of the separation reduces the fiber diameter or increased fiber density, also increases the internal resistivity. For this reason, it is desirable to develop a separator with a low internal resistivity.

There are two main ways of polymeric porous membranes of the of propylene, polyethylene or the like, namely, the wet process and the dry process. The above methods of obtaining have the appropriate properties. In the wet process, the plasticizer is added to the polymer, such as polyethylene, to obtain a film, and then the film is stretched in two directions, the plasticizer is removed by washing with a solvent and, thus, receive the pores. In this process, there are advantages such as the ability to easily adjust the pore size or film thickness and the ability to perform a variety of requirements for all individual types of batteries. On the other hand, there is a problem, namely that the process of obtaining considerably more complicated, and therefore increases the cost of the resulting membrane. In contrast, in the dry process, the polymer, such as polyolefin, dissolves and then extruded onto the film; a film of polymer is subjected to annealing, the annealed film is first stretched at a low temperature, to form the initial pores; and then stretch at high temperature to obtain a porous product. This process has the advantages that can be laminated polymers having different melting points, and that the process is simple and, as a consequence, you can receive the product with an reasonable cost. On the other hand), which was a problem, associated with the inability to perform fine control of the pore or the thickness of the membrane.

In addition, a separator-based nonwoven fabrics obtained from synthetic fibers, inorganic fibers or a similar material that is different from the porous polymer films. Traditionally, non-woven materials include materials dry and wet types, both of these types of nonwoven materials can be used as separators. It is assumed that the nonwoven materials, dry-type, in which it is impossible to obtain uniform distribution of the fibers have a weak effect isolation of the electrodes, and for this reason they should not be used for lithium-ion secondary batteries. On the other hand, nonwovens wet type has a uniform distribution of fibers in comparison with non-woven materials dry type. In addition, due to the characteristics of the method of obtaining it is possible to achieve a higher porosity compared to the porous film, and for this reason can be obtained sheet material with a reduced impedance. However, non-woven material dry type quite difficult to use batteries with graphite negative electrodes, which are widely used at present in the lithium-ion secondary batteries. This is due to the fact l is the tie-ion secondary battery, which is the formation of lithium dendrites on the negative electrode. The above-mentioned lithium dendrite has such a property that it is easily formed on the surface of the negative electrode, where many lithium ions passes through a separator. For this reason, non-woven materials in which you own the roughness of the formed sheet material is of the order of magnitude of several tens of microns, rough parts easily formed lithium dendrite. As a consequence, in the case of formation of lithium dendrite may deteriorate the characteristics of the screening of a short circuit, compared with the case where the materials of film type.

In order to overcome the above problems provides the control of pore size in a given range, as described in Patent document 1 (unexamined patent application Japan, the number of first publication H11-040130). However, the pore size depends on the diameter of the fibers. For this reason, in order to provide small pore size, it is necessary to reduce the diameter of the fiber. According to the technology of the prior art it is difficult to obtain fibers of the order of nanometer, with an acceptable cost. For this reason, even if you use synthetic fibers, called ultra-slim, almost impossible re wirawati pore size in the range suitable for lithium-ion secondary batteries. Therefore, to improve the characteristics of shielding lithium fails.

In addition, the method for obtaining a nonwoven fabric using the method of electrostatic spinning, described in patent document 2 (Japan patent No. 4425576). However, the aforementioned method does not seem practical, taking into account production efficiency, as well as the fact that obtaining a sheet material, having a thickness of several tens of microns, the existing industrial equipment much more difficult.

On the other hand, offered a variety of separators of the type of cellulose. For example, in patent document 3 (Japan patent No. 4201308) described that, since the hydroxyl groups of cellulose are not electrochemically stable, is processed by acetylation, and thus, hydroxyl groups stabilize and become suitable for lithium-ion secondary batteries. Moreover, a separator consisting mainly of cellulose, was used in the test trials of some lithium-ion secondary batteries. Thus, the electrochemical stability of cellulose per se should not be a problem when used in lithium ion secondary batteries.

In patent document 4 (Japan patent No. 4628764) t is the train offered a separator, using cellulose nanofibres. In fact, in patent document 4 described cellulose fibres, having a thickness of 1000 nm or less obtained in accordance with the method of using bacterial cellulose as described in patent document 4 or the like. However, the method for industrial preparation of cellulosic fibers with the use of bacterial cellulose has not been developed and remains unknown and the cost of such production. Therefore, the aforementioned method cannot be considered an effective method for making sheet material having reasonable cost. In addition, in patent document 4 describes a process using natural cellulose. In the processing of natural pulp with the aim of obtaining fibers of uniform thickness of 1000 nm or less is fibrillarin (education tangle of threads). As a result of this increased water retention, greatly increases the viscosity of the starting material used in paper production, and achieved low efficiency. For this reason, the aforementioned method cannot be considered effective. In addition, in patent document 4 describes that the process can be carried out by a casting method, however, it must be considered that the formation of pores differs from the process of production boom is I. Be that as it may, in patent document 4 is no clear description of the means used for the formation of pores, or a sufficient description of the formation of pores.

In addition, the production of paper is performed using at the stage of formation of the sheet material of the filter material or sieve. According to this method, the surface of the filter material during the process of dehydration is moved, and for this reason, in the floating outer side are formed roughness of several microns in size. Therefore, when such a separator is inserted into the lithium-ion secondary battery, there is poor adhesion between the separator and the electrodes, and the characteristics of the battery may deteriorate. Therefore, this method is not preferred.

In patent document 5 (unexamined patent application Japan, the number of first publication 2010-090486) proposed a sheet material, in which connection hydrocarbon-based emulsify using fine cellulose fibers, and the flow resistance of the air is regulated in a predetermined range. In this way, in which the formation of pores is performed by emulsification connection hydrocarbon-based, as the moisture evaporates at the stage of drying is the destruction of the emulsion, and therefore the sheet material about the course of inhomogeneous large pores, have a size of 1 μm or more. The result is degradation of the shielding lithium, and it could lead to a short circuit caused by lithium dendrites. For this reason, the aforementioned method cannot be used in lithium ion secondary batteries.

The documents of the prior art

Patent document 1: unexamined patent application Japan, the number of first publication H11-040130

Patent document 2: Japan patent No. 4425576

Patent document 3: Japan patent No. 4201308

Patent document 4: Japan patent No. 4628764

Patent document 5: unexamined patent application Japan, the number of first publication 2010-090486.

Disclosure of inventions

The problem solved by the present invention

The present invention was made considering the above circumstances, and the purpose of the invention to provide consisting of cellulose porous membrane having excellent characteristics of the separator, which can be obtained with reasonable cost, has excellent strength characteristics and, accordingly, can be used as a separator in an electrochemical device.

Methods of solving the problem

Through careful research aimed at achieving the above objectives, the authors of the present invention have found that since the flock membrane, formed from cellulose having special physical properties, has excellent characteristics of the separator for electrochemical device. Thus was accomplished the present invention.

The present invention relates to a porous membrane containing cellulose fibers, where

cellulosic fibers include cellulose fibers with a diameter of 1 μm or more in an amount of 5 wt.% or more based on the total weight of cellulose fibers,

and the porous membrane has an ultimate tensile strength of 50 N·m/g or more, and/or has a tensile tearing 0,40 kN/m or more.

Preferably, the porous membrane of the present invention has a porosity in the range from 30 to 70%.

Preferably, the porous membrane of the present invention has a specific volume resistance of 1500 Ohms·cm or less, as measured with alternating current with a frequency of 20 kHz for impregnation of the porous membrane 1-molar solution of LiPF₆in propylene carbonate.

Preferably, the porous membrane of the present invention is obtained from the suspension containing the above-mentioned cellulose fibers with hydrophilic agent steam formation.

The solubility of the above-mentioned hydrophilic agent steam formation in water is preferably 10 wt.% or more.

Preference is sustained fashion, the above-mentioned hydrophilic agent steam formation is a simple ether glycol.

Preferably, the suspension contains a hydrophilic polymer binder in an amount of from 3 to 80 parts by weight per 100 parts by weight of cellulose fibers.

In addition, the present invention relates to a separator for an electrochemical device containing the above-mentioned porous membrane. In addition, the present invention also relates to an electrochemical device, such as a battery, capacitor or the like containing the above-mentioned separator for electrochemical device.

In addition, the present invention also relates to a method for obtaining the above-mentioned porous membrane, comprising the stage of:

applying to the substrate a suspension containing at least a hydrophilic agent steam formation and cellulose fibers, including cellulose fibers with a diameter of 1 μm or more in an amount of 5 wt.% or more per the total mass of cellulose fibres;

drying the above-mentioned suspension with obtaining a sheet material on a substrate; and

the branches of this sheet material from above the substrate with obtaining cellulose porous membrane.

Preferably, the method of obtaining porous membrane of the present invention further is entrusted includes a step of cleaning the above-mentioned sheet material or porous membrane with an organic solvent.

Preferably, the above-mentioned cellulose fibers are pre-processed - microfibrillation processing by passing the pre-purified suspensions of pulp through the grinding of the unit with abrasive blades for grinding several abrasive plate with abrasive grains having a size ranging from No. 16 to No. 120.

Preferably, the above-mentioned cellulose fibers are pre-microfibrillation processing, during which the pre-treated slurry of pulp is treated using a homogenizer high pressure.

The results of the inventions

A porous membrane composed of cellulose according to the present invention shows excellent characteristics of the separator for electrochemical device. As a consequence, using the aforementioned porous membrane formed from cellulose of the present invention, can be obtained separator for electrochemical device having excellent characteristics shielding lithium, which cannot be achieved when using non-woven materials, paper or the like, and at the same time, having a low volume resistivity and having reasonable cost. In addition, the porous member is on the cellulose of the present invention has a higher ultimate tensile strength and/or increased strength of raster, and has excellent strength properties as a separator of an electrochemical device.

In addition, in a method of producing a porous membrane made of cellulose according to the present invention can easily obtain the desired pore size and number of pores in a porous membrane formed from cellulose. Thus, you can get formed from cellulose porous membrane which is suitable for a separator of an electrochemical device, has excellent shielding characteristics of lithium, which cannot be achieved when using non-woven materials, paper or the like, and at the same time has a low impedance or low volume resistivity. In addition, the obtained porous membrane of cellulose has excellent strength properties, and specified the porous membrane of cellulose can be obtained with reasonable cost.

Embodiments of the inventions

The porous membrane of the present invention is a porous membrane containing cellulose fibers, where

cellulosic fibers include cellulose fibers with a diameter of 1 μm or more in an amount of 5 wt.% or more based on the total weight of cellulose fibers,

and the porous membrane has an ultimate tensile strength of 50 N·m/g or more and/or has rocheste on raster 0,40 kN/m or more.

In the present invention is used cellulose fibers are not limited by the type of cellulose, such as cellulose I, cellulose II or the like. Preferred are natural fibers of cellulose I, represented by cotton, cotton lint or wood mass. Fibers of cellulose II, presents regenerated cellulose, have reduced the degree of crystallization as compared with cellulose fibres and I have a tendency to form short fibers during fibrillazione processing. For this reason, cellulose II is not preferred.

In the present invention the cellulose fibers can be microfibrillation. Device for microfibrillation processing cellulose fibers are virtually unlimited. As examples of such devices can be mentioned, for example, a homogenizer, such as a high-pressure homogenizer (for example, dispersing treatment at high pressure using a disperser Manton-Gaulin, homogenizer under pressure of the type Ranie, ultrahomogeneous high pressure, Altimizer (trade mark) (produced by Sugino Machine Co., Ltd.), dispersing device such as a ball mill or a planetary mill, mass colloid grinder (the unit with abrasive blades for grinding, in which there are several who brezovnik plate with abrasive grains, with sizes ranging from No. 16 to No. 120, produced by Masuko Sangyo Co., Ltd.) or the like. In addition, for pre-treatment before conducting microfibrillation processing can be used cleaning device used in the manufacture of paper, such as a cleaning device with dual drives or capturing roller. In addition, can also be used cellulose nanofibers obtained by the formation of nanofibers by using oxidation catalyst TEMPO, although their number in the mixture may be limited. In particular, in the present invention, cellulose fibers preferably are pre-microfibrillation processing by passing the pre-treated pulp suspension through the grinding of the unit with abrasive blades for grinding, which uses several of the abrasive plate with abrasive grains having a size ranging from No. 16 to No. 120; or prior microfibrillation processing by processing pre-purified suspensions of cellulose using high-pressure homogenizer.

Fibers having a diameter of 1 μm or more are contained in an amount of 5 wt.% or more, preferably 10 wt.% or more, relative to the total weight of the cellulose fibers used in the present izaberete the AI. In particular, the following production method of the present invention is applied to the substrate by casting, and for this reason it is difficult to prepare and use the suspension, with only a thin cellulose fibers with a fiber diameter less than 1 μm, which can lead to very high viscosity. In addition, to enable the application concentration of the suspension should be reduced, and, consequently, increase the cost of draining the solvent. For this reason, the cost of the membrane may be too high. In addition, if a thin cellulose fibers with reduced fiber diameter are formed under the action of the shearing forces applied to cellulosic fibres in the usual method, then the length of the fiber also tends to decrease. Therefore, the strength of raster obtained sheet material may have a tendency to decrease. Thus, the strength of raster obtained sheet material can be improved due to the presence of fibers having a diameter of 1 μm or more in an amount of 5 wt.% or more. As fibers that are different from the fibers with a diameter of 1 μm or more, can also be used in thin nanofibers with diameter of a few nanometers, as long as you can make application of a viscous suspension with concentric the Yu 1 wt.% or more on a substrate by a casting method.

In addition, the number of fibers having a diameter of 1 μm or more in the total mass of cellulose fibers used in the present invention, is preferably 30 wt.% or less. If fibers having a diameter of 1 μm or more are present in excess of 30 wt.%, the reduced number of contact points of the individual cellulose fibers due to hydrogen bonds. For this reason, the ultimate tensile strength can be greatly reduced, which is undesirable. Setting the number of fibers having a diameter of 1 μm or more in the range of from 5 wt.% or more to 30 wt.% or less, it is possible to obtain acceptable values of ultimate tensile strength, and the strength of raster.

Cellulose fibers can be uniformly dispersed in water due to the hydroxyl groups in the cellulose molecules and the viscosity of the suspension depends on the fiber length and surface area of cellulose fibers. In the case of thinner cellulose fibers increases the surface area of the pulp, and for this reason, the viscosity of the suspension naturally increases. In addition, with increasing length of the fibers increases the interaction between the fibers. I believe that this effect can also give a contribution to the viscosity increase. The increase in viscosity due to you is upomjanutogo interaction is a factor prevent the formation of sheet material with a high concentration. In the case of nanocellulose usually take measures to reduce the concentration.

In addition, the cellulose fibers have the property that during the stage of dehydration fibers are bound by hydrogen bonds due to the hydroxyl groups of cellulose. The specified property is not observed for non-woven materials derived from synthetic fibers, different from regenerated cellulose. In the above-mentioned stages of formation of hydrogen bonds occurs hardening material. On the other hand, during the stage of drying shrinkage of cellulose fibers due to the interaction between the fibers is greater than the shrinkage of the nonwoven materials using synthetic fibers. In particular, when reducing the diameter of the fibers reduces their stiffness. For this reason, the above-mentioned shrinkage becomes much more noticeable. In addition, it is known that the sheet material obtained by using fibers, which largely occurred fibrillation, fiber completely stick together, and for this reason there is transparency. That is difficult to control the diameter of pores or produce porous sheet material only by reducing the fiber diameter (thickness). For this reason, the control UCA is key during drying and inhibition of the formation of hydrogen bonds between the fibers when receiving porous sheet material. Some traditional methods suggest that the raw materials, processed in the sheet material using the methods of paper production or way of casting, dried by replacing the solvent is a hydrophilic solvent, such as acetone, and subsequent replacement of the hydrophilic solvent is more hydrophobic solvent such as a mixture of toluene and acetone.

However, for the above-mentioned methods, there are two problems. The first problem is the replacement of water dispersing solvent acetone. Cellulose fibers have the property of improving the water retention while reducing the diameter of the fibers. For this reason, the replacement operation of the water solvent is very slow and is a factor limiting the performance of industrial production. In addition, the pore diameter depends on the diameter of the fibers, and for this reason, the diameter of pores is largely controlled by the thickness of the fibers. So if you do not use a uniform fiber, it is not possible to obtain the desired pore size. In addition, for the stage of processing cellulose fibers requires time and expense.

The porous membrane formed from cellulose of the present invention, has excellent strength characteristics. More specifically, the limit of the tensile strength then the stand of the membrane, formed from cellulose of the present invention, is 50 N·m/g or more, and/or strength of the membrane on raster is 0,40 kN/m or more. The ultimate tensile strength can be measured in accordance with JIS C2151. The strength of raster can be measured using a "Trouser" test method for raster in accordance with JIS K-1. Preferably the limit of the tensile strength of 55 N·m/g or more, and more preferably 60 N·m/g or more. Preferably the strength of raster is 0.5 kN/m or more, more preferably 0.55 kN/g or more, and even more preferably of 0.6 kN/m or more. In traditional cellulose membrane separator for electrochemical device, it is difficult to simultaneously achieve excellent ultimate tensile strength and excellent durability on raster. On the other hand, in the present invention in the cellulosic fibers are cellulose fibers having a diameter of 1 μm or more, comprising 5 wt.% or more based on the total weight of cellulose fibers in a porous membrane formed from cellulose, and for this reason, can be achieved as an excellent ultimate tensile strength, and excellent durability on raster.

The diameter of pores of the porous membrane formed from cellulose truly izopet the tion, preferably has a maximum value measured by the method of pushing the mercury, which is 1.5 μm or less. The size of the particles of the electrode active material used in an electrochemical device, such as a lithium-ion battery, can be different. For this reason, the diameter of pores do not always have to be small. As a rough criterion: if the diameter of pores is 1/4 the size of the particles used in the battery electrode active material, a short circuit should not happen. On the other hand, in the case of electrochemical device that uses active materials with small particle size, in some cases, the maximum value should be reduced to less than 1.5 μm. When the particle size composition of the sheet material obtained in the present invention, measured using the method of indentation mercury, can also be detected peak to 1.5 μm or more. This is due to the chaotic nature of the surface of the sheet material and does not mean pore diameter of the porous membrane formed from cellulose.

In a porous membrane formed from cellulose of the present invention, the resistance to air flow of 10 μm film thickness preferably ranges from 20 to 600 seconds (100 ml), more preferably changes range from 20 to 450 seconds and more preferably ranges from 30 to 250 seconds. The above-mentioned resistance to air flow can be measured on the basis of the description of JIS P8117. When the above-mentioned resistance to air flow is less than 20 seconds, degradation of shielding lithium, and the use of such membranes in lithium-ion secondary battery may increase the risk of short circuit due to lithium dendrite. Therefore, for security reasons, it is undesirable. On the other hand, when the resistance to air flow exceeds 600 seconds, significantly increases the volume resistivity, and can deteriorate the output characteristics of the electrochemical device. Therefore, it is also undesirable.

The porous membrane formed from cellulose of the present invention, has a specific volume resistance of 1500 Ohms·cm or less, as determined using an alternating current with a frequency of 20 kHz and formed from cellulose porous membrane impregnated with 1-molar solution of LiPF₆in propylene carbonate. The volume resistivity correlates with the above-mentioned resistance to air flow and porosity. In General, decreasing the resistance to air flow and increase the porosity tends to mind is isenia bulk resistivity. The pore size of the porous membrane and the distribution of pores in the membrane also affect the volume resistivity. For this reason, the porous membrane formed from cellulose and having low resistance to air flow and increased porosity, not always has a low volume resistivity. In the present invention, in order to exclude the influence of such electrochemical phenomena, as a reaction on the surface of the electrode section, the measured value of volume resistivity is used alternating current with a frequency of 20 kHz. Thus, the measured value gives the only contribution total resistance measuring device and the ionic conductivity of the porous membrane formed from cellulose. Therefore, the measured value may reflect the influence of pore distribution and pore diameter of the porous membrane formed from cellulose. In particular, the above-mentioned volume resistivity is preferably 1500 Ohm·cm or less, and more preferably 1000 Ω·cm or less. When the volume resistivity exceeds 1500 Ohm·cm, may deteriorate the cyclic characteristic. When the volume resistivity is 1500 Ohm·cm or less is a good cycle characteristic. For this reason, the value specified for the volume in the additional resistance may be suitable for use in the separator for electrochemical device.

In the present invention the measurement of the volumetric specific resistance using an alternating current with a frequency of 20 kHz can be carried out in accordance with the following procedures: first, the porous membrane formed from cellulose, 20 mm in diameter, dried for 24 hours or more at 150°C. Then five dried porous membrane formed from cellulose, place, putting them in a stack in the holder solid sample model SH2-Z (produced by Toyo Corporation), and sufficiently impregnated with the electrolytic solution LiPF₆in propylene carbonate at a concentration of 1 mol/L. in Addition, after removal of air remaining inside formed from cellulose porous membrane at a pressure reduced to 0.8 MPa, formed from cellulose porous membrane is preferably set between two electrodes with gold-plated surface and measure the impedance (Ohms) AC with frequency analyzer VSP (produced by Bio-Logic), in which the potentiometer/galvanostat combined under conditions of oscillating frequency range from 100 MHz to 1 MHz and amplitude of 10 mV. The resistance per unit volume (specific volume resistance) calculated from the above values and the measured thickness of the porous membrane formed from the cellulite, tighten the PS. Preferably, was also measured (or excluded) component of the resistance of the measuring device, to eliminate its influence on the measurement results.

Preferably, the porosity of the porous membrane formed from cellulose of the present invention, ranges from 30% to 70%. The porous membrane formed from cellulose of the present invention, retains porosity in the range from 30% to 70%, and thus, the porous membrane formed from cellulose can be conveniently used in an electrochemical device. Electrochemical device with a porous membrane formed from cellulose, can be used, even if the porosity is less than 30%, however, in this case, the output is reduced due to the high resistance values. Therefore, adequate characteristics of the electrochemical device in this case can not be achieved. On the other hand, if the porosity exceeds 70%, increasing fashion of pore size distribution and reduced resistance due to the porous membrane formed from cellulose. As a result, improves the performance output of the electrochemical device and cyclic characteristics. However, when used in lithium ion secondary batteries deteriorate the characteristics of the shielding lithium and may in Tractate the risk of short circuit due to lithium dendrite. Therefore, it is also undesirable from a security point of view.

In the present invention, the porosity can be calculated using the mass of solvent absorbed formed from cellulose porous membrane after impregnation of the porous membrane formed from cellulose, a solvent in which the cellulose fibers do not swell. More specifically, a specimen prepared by cutting the separator into pieces with a size of 50 mm × 50 mm, hydrate for 1 day at ambient conditions of 23°C and 50% relative humidity and then measure the thickness of the sample. In addition, measure the mass of the sample using scales with an accuracy of up to 4-th or 5-th character. After weighing the sample impregnated with the solvent for 1 minute. Then the excess solvent on the surface of the sample, remove the absorbent paper, and the sample is weighed again. The value obtained by subtracting the mass of the sample before impregnation solvent from the mass of the sample after impregnation solvent, divided by the density of the solvent. Thus you can calculate the volume of the solvent. The obtained value of the volume divided by total volume, calculated from the thickness, and then multiplied by 100 (%). The obtained value determines the porosity. Therefore, in this case, the porosity can be calculated from the following equation:

Porosity (%)=100×((mA the sa of the sheet material after impregnation solvent)-(weight of sheet material prior to impregnation solvent))/((density of the solvent, used for impregnation)×5×5×(thickness) (cm)).

The solvent which can be used in the measurement of porosity in the present invention is a solvent in which the cellulose does not swell. For this reason, preferably used an organic solvent having a low polarity. In addition, the solvent must be chosen from among those which do not evaporate within a short time interval measurements. As examples of particularly preferred solvents may be mentioned propylene glycol, which is commonly used in the electrolytic solution or the solvent of petroleum origin having a high boiling point, such as kerosene, and the like.

The surface roughness Ra, as on the obverse and on the reverse side formed from cellulose porous membrane for electrochemical device obtained in accordance with the present invention, preferably 1.5 or less. It is known that the surface roughness affects the impedance to AC current flow through the contact resistance of the separator and the positive electrode during Assembly of the electrochemical device. The above contact resistance can be calculated from the difference between the value of the impedance when the AC is current with a frequency of 0.1 Hz and a value of impedance of the alternating current with a frequency of 20000 Hz, where both values are measured with the help of such electrochemical devices, such as layered element or battery coin type. When the value of the surface roughness Ra increases, the difference between the value of impedance of the alternating current with a frequency of 0.1 Hz and a value of impedance at the AC frequency of 20000 Hz increases. The value of the impedance when alternating current is inversely proportional to the square of the outer surface, in accordance with Ohm's law. When the outer surface is increased, the measured resistance value is reduced. For this reason, the measured value is typically affected by measurement error, and decreasing the frequency components of the resistance of the positive electrode and the negative electrode is also included in the value of the impedance at the AC. Therefore, these values cannot be attributed only to differences in the separator. If you use a battery with the same electrodes, the same electrolytic solution and the same dimensions, we can observe differences caused by the influence of the surface characteristics of the separators. For example, the value of impedance of the alternating current and the value of Ra, equal to 1.5, is about 1 Ohm in the case of layered element having the surface 15 cm^{2 and obtained using the original materials used in conventional lithium ion secondary batteries, for example, the positive electrode on the basis of CoLiO₂, a negative electrode, graphite based, and the electrolytic solution LiPF₆. Since it is preferable to lower the contact resistance of the battery, preferred are the conditions under which the value of Ra is small as possible. When the battery was manufactured and measured the impedance of the alternating current, it is preferable to measure the impedance was carried out after 3-5 cycles of charge-discharge with low intensity, and in the subsequent charging is performed up to the setpoint voltage.}

^{The surface roughness Ra is changed in accordance with the influence of the size of the source materials, the dispersion conditions of the fibers and the surface characteristics of the substrate. In particular, the surface roughness Ra is more significantly affected by the outer surface of the transfer substrate of the separator, in comparison with the size of the source materials or the dispersion conditions of the fibers. For this reason, the above-mentioned outer surface, it is expedient to use from the positive electrode. In the case of a filtering material or wire sediv the method of production of paper, wire mesh is not suitable, since the outer surface of the transfer of the filter material is shown as it is, and it is impossible to control the value of Ra at low levels.}

^{The porous membrane formed from cellulose of the present invention, preferably obtained from a suspension containing hydrophilic agent steam formation with cellulose fibers having a diameter of 1 μm or more and present in an amount of 5 wt.% or more based on the total weight of cellulose fibers.}

^{Preferably, the porous membrane formed from cellulose of the present invention, can be obtained in a method that includes the steps:}

^{applying to the substrate a suspension comprising as essential components, a hydrophilic agent steam formation and cellulose fibers, including cellulose fibers having a diameter of 1 μm or more, in number, in the range from 5 wt.% or more preferably to 30 wt.% or less based on the total weight of cellulose fibers;}

^{drying the above-mentioned suspension with obtaining a sheet material on a substrate; and}

^{the separation of the sheet material from above the substrate with obtaining cellulose porous membrane containing the above-mentioned sheet material.}

^{In the way of getting this and the finding as a means of imparting porosity of the sheet material, formed from cellulose fibers, is applied to the substrate suspension containing hydrophilic agent steam formation, followed by drying. Thus can be substantially improved production efficiency. In addition, in the present invention can adjust the solubility of the hydrophilic agent steam formation in water and, thus, to regulate the pore size of the sheet material. In addition, in the present invention can adjust the amount of added hydrophilic agent steam formation and, thus, to regulate the porosity. For example, in the present invention the hydrophilic agent steam formation can be used in a quantity preferably ranges from 50 to 600 parts by weight, more preferably in the range from 80 to 400 parts by weight, and more preferably in the range from 100 to 300 parts by weight per 100 parts by weight of cellulose fibers.}

^{In the present invention the hydrophilic agent steam formation does not particularly limited as long as he is a hydrophilic substance, which forms pores in a sheet material formed of cellulose fibers. Preferably, the boiling point of the hydrophilic agent steam formation is 180°C or higher. It is known that hydrogen bonds between bolognabeliever material are formed, when in the course of drying, the moisture content of the sheet is in the range from 10 to 20 wt.%. At the time of formation of the above-mentioned hydrogen bonds agent of steam formation is present in the sheet material, and the formation of hydrogen bonds between the fibers is prevented. Thus, it can be obtained porous sheet material. In the case of the agent of steam formation, having a boiling point of below 180°C, the steam formation agent evaporates at the stage of drying, even if you use an increased amount of it, and cannot be obtained sufficiently porous sheet material. For this reason, it is preferable to use the agent of steam formation, having a boiling point of 180°C or higher. Preferably, the steam formation agent has a boiling point of 200°C or higher. The primary alcohol or the like, having a value of molecular weight less than hexanol, is a material with a solubility in water, and hydrophobic properties. At the stage of drying the material evaporates more easily than water, and for this reason the formation of hydrogen bonds cannot be suppressed sufficiently effectively. Therefore, this material may not be used in the present invention. In the case of using the method of drying in special conditions that differ from the normal drying conditions, when the loud air drying of saturated vapors of steam formation agent, or using a multi-stage drying solvent having a lower vapor pressure than water, the agent of steam formation is not required to have a boiling point of 180°C or higher.}

^{The hydrophilic agent is steam formation used in the present invention has a solubility with respect to water, which is preferably 20 wt.% or more, and more preferably 30 wt.% or more. In the case of the use of steam formation agent with a solubility in water of less than 20 wt.%, the number of added agent of steam formation is limited. For this reason, it may be difficult to adjust the desired porosity only due to the quantity of the agent of steam formation. In addition, in the drying process, the amount of solvent is reduced, and as a result, the agent of steam formation, which can no longer be in the solution falls out of the mix. For this reason, it may be difficult to achieve a uniform formation of pores in the plane of the outer surface and in the direction of thickness of the sheet material. The above-mentioned hydrophobic agent steam formation can emulgirovanija an emulsifier or the like, and thus can be achieved to some extent uniform formation of pores. However, C is trunilina to control the diameter of pores. On the other hand, in the case of the use of steam formation agent with a solubility in water 20 wt.% or more, the steam formation agent can uniformly be dispergirujutsja in suspension, and because of its high solubility in water at the stage of drying will be his loss. For this reason, due to an even prevent the formation of hydrogen bonds possibly even the formation of pores.}

^{Used in the present invention the hydrophilic agent steam formation preferably has at 25°C vapor pressure less than 0.1 kPa, more preferably less than 0,09 kPa, and even more preferably less than 0.08 kPa. Hydrophilic steam formation agent having a vapor pressure of 0.1 kPa or more, has a high volatility. For this reason specified hydrophilic agent steam formation has an increased tendency to evaporation before he has time to contribute to the formation of pores in the cellulose membrane. In the production of porous cellulose membranes can be difficult.}

^{Used in the present invention the hydrophilic agent steam formation preferably has a distribution coefficient in a mixture of water-octanol (logPow) in the range from to 1.2 to 0.8, more preferably in the range of -1,1 up to 0.8 and even more preferably in the range of-0.7 to 0.4. As mentioned above octanol preferred which is n-octanol. If you are using hydrophilic agent steam formation with a distribution coefficient less -1,2, you can increase the value of the overall resistance of the obtained porous membrane formed from cellulose.}

^{As examples of hydrophilic agents of steam formation, which can be used in the present invention, may be mentioned, for example, higher alcohols such as 1,5-pentanediol, 1-methylamino-2,3-propandiol or the like; lactones such as ε-caprolactone, α-acetyl-γ-butyrolactone or the like; glycols, such as diethylene glycol, 1,3-butyleneglycol, propylene glycol or the like; and ethers of glycols, such as dimethyl ether of triethylene glycol, dimethyl ether of tripropyleneglycol, monobutyl ether of diethylene glycol, onomatology ether of triethylene glycol, butyl methyl ether of triethylene glycol, dimethyl ether of tetraethyleneglycol, monotropy ether diethylenglycol, monotropy ether of diethylene glycol, monobutyl ether of triethylene glycol, monobutyl broadcast tetraethyleneglycol, onomatology broadcast dipropyleneglycol, onomatology ether of diethylene glycol, monoisopropylamine ether of diethylene glycol, monoisobutyl ether of ethylene glycol, onomatology broadcast tripropyleneglycol, metaliteracy ether of diethylene glycol, diethyl ether of diethylene glycol or of podobn is e, as well as glycerin; propylene carbonate; N-organic; or the like. Examples of agents are not limited to these. Among them ethers of glycols have a low vapor pressure and are most preferred for use in the production method of the present invention.}

^{Preferably used in the present invention, the slurry contains, in addition to cellulose fibers and hydrophilic agent steam formation, hydrophilic polymer acting as a binder for fibers in an amount of from 3 to 80 parts by weight, preferably in the range of from 5 to 50 parts by weight per 100 parts by weight of the above-mentioned cellulose fibers. The hydrophilic polymer binder may also improve the dispersion characteristics of cellulose, in addition to the function of the binder material. In order to achieve uniform distribution then it is necessary that the fibers were uniformly dispersed in the suspension. Hydrophilic polymeric binding agent attached to the surface of cellulose fibres, playing the role of a protective colloid. As a result, improves the dispersion properties. If the mixing amount of the binder is less than 3 parts by weight, the strength of the sheet material can be reduced, and the dispersion properties of cellulose is s fibers may deteriorate. For this reason, it is difficult to obtain a uniform pores. On the other hand, if the specified amount exceeds 80 parts by weight, the binder fills the pores and increases the volumetric resistivity of the porous membrane formed from cellulose. Therefore, these options are not preferred.}

^{As the above-mentioned hydrophilic polymer binder may be used cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hypromellose, hydroxyethylcellulose or the like; derivatives of polysaccharide, such as starch phosphate, cationically starch, corn starch or the like; or binder such as aqueous emulsion of a copolymer of butadiene and styrene, polyvinylidene fluoride or the like, known as binders for electrodes.}

^{The substrate used in the present invention does not particularly limited, and can be used a polymer film, glass plate, metal plate, loose paper or the like. As the substrate, it is preferable to use one in which the hydrophilic agent steam formation does not fall out of suspension on the rear surface, such as a wire, filter the Cagnes, a paper filter or the like. In the production method of the present invention, the pores are formed using hydrophilic agent steam formation. For this reason, if the hydrophilic agent steam formation falls from the rear surface of the substrate during a stage of drying, the sheet material can not form a sufficient number of pores. In addition, the dried sheet material has such surface properties possessed by the substrate. For this reason, the surface of the substrate is preferably as smooth as possible. Whereas the above description, a film of polyethylene terephthalate, stretched in two directions, has the property of elasticity and has a relatively high melting point. As a result, may decrease the effects of stretching or shrinkage during drying. In addition, the film of polyethylene terephthalate, stretched in two directions, has a high polarity, compared with a polypropylene film. For this reason, this tape is easy to apply, even in the composition of the aqueous suspension, and can appropriately be used in the present invention.}

^{In the production method of the present invention as a method of applying to the substrate a suspension containing cellulosic fibers and hydrophilic agent steam formation, can be used the Vanir any means, until the suspension can be applied evenly so that the film thickness in the deposited layer is in a predetermined range of values. For example, the application may be implemented using pre-adjusted device for coating, such as a device with slotted Villeroy, a device for coating irrigation, or the like, or even devices with subsequent dosing, such as the MB device for coating, MB reversing device, the device "knife on top of the roll or the like.}

^{In the present invention, if necessary, the suspension can as an additive to add surface-active substance. Nonionic surfactant represented by acetylene glycol and used as antifoaming additive, or a leveling agent may be used in amounts that do not affect the characteristics of the electrochemical device. Preferably, the ionic surfactant is not used, as these substances can affect the properties of the electrochemical device.}

^{In suspension comprising cellulosic fibers and hydrophilic agent steam formation, in addition to the above binder and surfactants, can is to hold the filler. For example, there can be used inorganic fillers such as particles of silicon dioxide or aluminum oxide, and organic fillers such as silicon powders and the like. These particles may be added in amounts that do not affect the pores of the porous membrane formed from cellulose. Preferred are particles having an average size less than 2 microns. If the average particle size is 2 μm or more, due to the space between the particles are formed pores with a larger diameter, and for this reason this option is not preferred. The above-mentioned fillers have an impact on the decrease in viscosity. For this reason, the concentration of the coating material can be increased, which is suitable for increasing the efficiency of production. On the other hand, if applied an excessive amount of filler, reduced strength. For this reason, the addition of filler in the amount of more than 100 parts by weight per 100 parts by weight of cellulose fibers is not preferred.}

^{As the solvent used in the present invention, basically the water is taken. To improve drying efficiency can be added to the solvent with a higher vapor pressure than water, such as alcohol, for example meta is ol, ethanol or tert-butyl alcohol, a ketone, for example acetone or methyl ethyl ketone, simple ether, for example diethyl ether or utilmately ether, or the like, in an amount up to 50 wt.% from the total quantity of solvent. If the above solvent is added in a quantity of 50 wt.% or more, the dispersion characteristics of cellulose fibers deteriorate, and violated the uniformity of pore distribution. For this reason, this option is not preferred.}

^{In the production method of the present invention the above-mentioned deposited on a substrate, the slurry may be dried to obtain a sheet material. Method of drying does not particularly limited. In particular, can be used to traditionally used methods of drying, such as any one or both of the method of drying with hot air and drying method using radiation in the far infrared region. For example, the temperature of hot air can be in the range from 30°C to 150°C, and preferably from 60°C to 120°C. it is Necessary to adjust the temperature of hot air, the amount of hot air, conditions of radiation in the far infrared region or the like to the structure in the direction of thickness of the sheet material was dried under conditions of hot air temperature, the amount of hot air and the temperature of the radiation in the far is infrakrasnoi area evenly as possible. In addition, to improve drying efficiency can also be used to heat the ultra high frequency currents.}

^{Preferably, the thickness of the sheet material in the present invention ranges from 10 to 40 μm. The thickness of the porous membrane formed from cellulose, is a factor that can significantly alter the characteristics of the electrochemical device. If the thickness is less than 10 μm, it is impossible to provide adequate shielding characteristics lithium and security may not be sufficient. On the other hand, if the thickness exceeds 40 μm, it increases the volume resistivity of the porous membrane formed from cellulose, and may deteriorate the output characteristics of the electrochemical device. For this reason, both of these options are not preferred. Especially preferred is a sheet material having a thickness in the range from 15 to 30 μm, in connection with balanced characteristics shielding lithium and bulk resistivity.}

^{In the production method of the present invention the sheet material formed as described above, on the substrate, separated, and thus can be obtained a porous membrane formed from cellulose, consisting of the above-mentioned sheet material. The way the Department is placed a porous membrane, formed from the substrate, does not specifically limited.}

^{Furthermore, the method of receiving according to the present invention can include a purification step of the above-mentioned sheet material with an organic solvent, in addition to stages:}

^{applying to the substrate a suspension comprising at least hydrophilic agent steam formation and cellulose fibers, including fibers with a diameter of 1 μm or more in an amount of 5 wt.% or more and preferably 30 wt.% or less based on the total weight of cellulose fibers;}

^{drying the suspension to obtain a sheet material on a substrate; and}

^{Department of the sheet material from the substrate in order to obtain a porous membrane formed from cellulose and containing the above-mentioned sheet material.}

^{The above purification step carried out in order to remove components, inhibiting characteristics of the electrochemical device in case of using a surfactant, if necessary, and freely to carry out the separation of the above-mentioned sheet material from the substrate. The organic solvent is not limited, subject only to the condition that this organic solvent can be used at the stage of purification. It is preferable hydrophobic solvent with low solubility in water to eliminate the build effects of shrinkage of the sheet material due to the movement of residual moisture in the organic solvent.}

^{As for the above-mentioned organic solvent may be used, for example, one, two or more types of organic solvents with a relatively high evaporation rate, such as acetone, methyl ethyl ketone, ethyl acetate, n-hexane, toluene or propanol, once or in several separate operations. Method of using an organic solvent in the invention is not limited. In order to remove residual agent of steam formation, preferred is a solvent having high compatibility with water, such as ethanol or methanol. However, the moisture in the sheet material moves to the solvent or in the atmosphere, which affects the physical properties of the porous membrane formed from cellulose or from sheet material. For this reason, specified the solvent to be used in conditions in which a controlled amount of moisture. Solvents with high hydrophobicity, such as n-hexane or toluene, show low efficiency in the purification of the hydrophilic agent steam formation, but cannot easily absorb moisture. For this reason it is preferable to use these solvents. For the above reasons, it is preferable, for example, a method in which cleaning is sequentially carried out with several will dissolve the representatives, for example, acetone, toluene and n-hexane, gradually increasing the hydrophobicity of the solvent, and to replace the solvent, purification was repeated once more.}

^{The porous membrane formed from cellulose of the present invention, can be used as a component element separator for electrochemical device, or can be used as a separator for electrochemical device as such.}

^{Separator for electrochemical device of the present invention can be used, for example, in the battery, such as lithium-ion secondary battery or a lithium polymer battery, and also as a capacitor, such as aluminum electrolytic capacitors, electric double-layer capacitor or a lithium-ion capacitor.}

^{The composition of the aforementioned electrochemical devices can be exactly the same as the composition of traditional electrochemical devices, except for use as a separator of the above-mentioned separator for electrochemical device of the present invention. The cell structure of the electrochemical device does not particularly limited. As examples can be mentioned structure of the layered type, cylindrical type, square type, coin type, and so on is one.}

^{For example, a lithium-ion secondary battery as the electrochemical device containing the separator of the present invention has a positive electrode and a negative electrode, between which is located above the separator for electrochemical device, and the specified separator for electrochemical device impregnated with the electrolytic solution.}

^{The above positive and negative electrodes contain active electrode materials. As the active material of the positive electrode can be used traditionally known materials. As examples of such materials may be mentioned, for example, oxide of lithium and transition metal, such as LiCoO₂, LiNiO₂or LiMnO₄; phosphate lithium and another metal, such as LiFePO₄; and the like. As the active material of the negative electrode can be used traditionally known materials. As examples of such materials may be mentioned, for example, a carbon material such as graphite; a lithium alloy; and the like. In addition, if necessary, the electrodes can be added traditionally known auxiliary conductive materials or binders.}

^{To obtain a lithium ion secondary battery, first, traditionally known what's collectors independently apply the mixture to the positive electrode, containing the active material of the positive electrode and, if necessary, traditionally known auxiliary conductive material and/or traditionally known conductive binder, and the mixture of the negative electrode containing the active material of the negative electrode and, if necessary, traditionally known auxiliary conductive material and/or traditionally known conductive binder. As a collector of positive electrode using, for example, aluminum or the like, and as a collector of the negative electrode using copper, Nickel or the like. After applying the positive electrode mixture and the negative electrode to the collector of the latter is dried and subjected to thermal pneumoperitoneum. Thus can be obtained positive and negative electrodes, in which the layer of active material is formed on the collector.}

^{Then, the obtained positive and negative electrodes and the separator for electrochemical device of the present invention laminated or wound in order to construct a device of the positive electrode, the separator for electrochemical device and the negative electrode. After that, the aforementioned device is inserted into the external enclosure m the material, the reservoir is connected to the external electrodes and impregnated with traditionally known electrolytic solution. Then the outer seal material. Thus can be obtained lithium ion secondary battery.}

^{In addition, the electrochemical device may be an electric double-layer capacitor containing the separator of the present invention and having a positive electrode and a negative electrode, between which is located a separator for electrochemical device of the present invention, and the above-mentioned separator for electrochemical device impregnated with the electrolytic solution.}

^{The above positive and negative electrodes can be obtained, for example, by applying the electrode mixture, which contains a powder of activated carbon and is traditionally known auxiliary conductive material and/or traditionally known conductive binder, traditionally known collector, which is dried and subjected to thermal pneumoperitoneum. As a collector is used, for example, aluminum or the like.}

^{Electric double-layer capacitor can be obtained as follows: the positive and negative electrodes and the separator for electrochemical device according to the present izaberete the July laminated or wound, to construct the device of the positive electrode, the separator for electrochemical device and the negative electrode. Then the above-mentioned device is inserted into the housing exterior material, the reservoir is connected to the external electrodes and impregnated with traditionally known electrolytic solution. After the seal material.}

^Examples

^{Further, the present invention is described in detail with reference to Examples and Comparative examples. It should be understood that the scope of the present invention is not limited to the given examples.}

^{(1) Measurement of the fiber length}

^{Srednekamennogo the length of the fiber is measured using an instrument for measuring fiber length, FIBER TESTER (produced by L & W).}

^{(2) measurement of the number of fibers having a diameter of 1 μm or more in the sample}

^{Use the following calculation method. Data of x-ray diffraction obtained using x-ray analyzer, CT) set at the threshold level, where you can watch a fiber diameter of 1 μm or more. Fragments of fibres extracted and counting the number of fibers in their degree of inclusion in the total number of fibers. The sample is cut into pieces having a width of approximately 1 mm Cut sample having a width of approx is Ino 1 mm, fix by means of the device for mounting the sample and subjected to CT-scanning device TDM 1000H-Sµ. Measurement of the number of fibers is carried out by allocating any space 27,89 μm × 448,70 μm × 432,26 μm in the Central part, to completely eliminate the ingress of air from the outer boundary of the sample.}

^{(3) Measurement of thickness}

^{The thickness of the sample separator size of 50 mm × 50 mm measured in any 5 points by means of measuring the thickness of TM (produced by Kumagai Riki Kogyo Co., Ltd.). The average value obtained from the above-mentioned 5 measured values of the thickness, is used as the thickness of the membrane.}

^{(4) Measurement of ultimate tensile strength}

^{Ultimate tensile strength is measured using a method in accordance with JIS C2151.}

^{(5) measurement of the strength of raster}

^{The strength of raster measured using the "official" method of tear in accordance with JIS K7128-1.}

^{(6) Measurement of impedance at the AC frequency of 20 kHz and the definition of specific volume resistance}

^{As a cell for measuring the total resistance is used, the holder solid sample model SH2-Z (produced by Toyo Corporation). The fragment separator 20 mm in diameter and dried for 24 hours or more at a temperature of 150°C. Then five dried separators made the Ute in the cell in a stack and then fully impregnated with 1-molar electrolytic solution LiPF ₆in propylene carbonate. After removal of air remaining between the separators, under reduced pressure up to 0.8 MPa, the separator is fixed between two electrodes with gold-plated surface, and measure the impedance (Ohms) AC with frequency analyzer VSP (produced by Bio-Logic), in which the potentiometer/galvanostat combined under conditions of oscillating frequency range from 100 MHz to 1 MHz and amplitude of 10 mV. Temperature measurement is 25°C. the Resistance per unit volume (specific volume resistance) calculated from the above values and the measured thickness, as described above in (3).}

^{(7) Measurement of porosity}

^{The sample obtained by cutting the separator into pieces with a size of 50 mm × 50 mm, hydrate for 1 day at ambient conditions of 23°C and 50% relative humidity, and then measure the thickness and the mass of the sample by weighing on scales accurate to 4-th or 5-th character. After weighing the sample impregnated with kerosene for 1 minute. Then the excess solvent on the surface of the sample, remove the absorbent paper, and the sample is weighed again. Porosity calculated using the above equation.}

^{Example 1}

^{Kraft pulp NBKP (Northern bleached Kraft pulp) was dispersed in dionisiou the Noi water, to obtain the concentration of cellulose 2 wt.%. This dispersion is subjected to purifying cyclic processing in such conditions, to srednedlinny fiber length was 1.0 mm or less, using cleaning devices with double disc. Dispersion of cellulose fibers, in which srednedlinny fiber length is 1.0 mm or less, process 10 times using high-pressure homogenizer (manufactured item LAB-1000) at a pressure of 800 bar. Thus, get the source material 1 microfibrillated cellulose fibers. In the same way as described above, receive the source material 2 microfibrillated cellulose fibers, by conducting a three-time processing by high-pressure homogenizer. The above starting materials 1 and 2 are subjected to independent processing using a centrifuge device for fibers, for 5 minutes with a speed of 10,000 rpm to obtain a concentration of about 10 wt.%.}

^{The source material was obtained by mixing cellulose fibers of the above-mentioned starting material 1 in the amount of 90 wt.% in the calculation of the solid substance and the cellulose fibers of the above-mentioned starting material 2 in the amount of 10 wt.% in the calculation of the solids relative to the total amount of cellulose fibers. To 100 parts by weight of the above-mentioned source is about material added 250 parts by weight butyl methyl ether of triethylene glycol, having a boiling point of 261°C and having unlimited solubility in water, acting as the hydrophilic agent steam formation, and 20 parts by weight of carboxymethyl cellulose as a binder (product name: MAC-500 LC, produced by Nippon Paper Industries Co., Ltd., Chemical Division), dissolved in deionized water to obtain a concentration of 1 wt.%, and add in the mixture of water so that the final concentration of solids in the mixture was 1.5 wt%. Thus obtained coating material. The specified coating material is subjected to dispersing treatment using a ball mill with beads of Zirconia size 3 µm, until the mixture is evenly mixed up.}

^{The prepared coating material is applied on a film of polyethylene terephthalate (PET) with a thickness of 100 μm using an applicator so that the thickness of the WET sheet material was 1.0 mm, and then dried for 12 minutes with hot air at 80°C and an infrared heater. Prepared sheet material of the coating is separated from the PET film in toluene, and then the toluene is evaporated from the material. Thus obtained sheet material (the porous membrane formed from cellulose) with sheet thickness of 20 μm.}

^{Example 2}

^{Sheet material with a thickness of 20 μm get in the same way as in point is the iMER 1, except for using 80 wt.% in the calculation of the solid cellulose fibers of the above-mentioned starting material 1 and 20 wt.% in the calculation of the solid cellulose fibers of the above-mentioned starting material 2.}

^{Example 3}

^{Sheet material of a thickness of 21 μm receive the same manner as in example 1, except for using 50 wt.% in the calculation of the solid cellulose fibers of the above-mentioned starting material 1 and 50 wt.% in the calculation of the solid cellulose fibers of the above-mentioned starting material 2.}

^{Example 4}

^{Kraft pulp NBKP was dispersed in deionized water to obtain a concentration of cellulose 2 wt.%. This dispersion is subjected to cyclic cleansing treatment under such conditions that srednedlinny fiber length was 1.0 mm or less, using cleaning devices with dual drives. Dispersion of cellulose fibres, in which srednedlinny the length of the fibers is 1.0 mm or less, treated three times with bulk colloid mill (produced by Masuko Sangyo Co., Ltd.). So get your source material 3 microfibrillated cellulose fibers. Then the sheet material of a thickness of 21 μm receive the same manner as in example 1, except for using 50 wt.% in the calculation of the solid substance cellulo the different fibers of the above-mentioned starting material 3 and 50 wt.% in the calculation of the solid cellulose fibers of the above-mentioned starting material 2.}

^{Comparative example 1}

^{Sheet material of a thickness of 23 μm receive the same manner as in example 1, except for using 40 wt.% in the calculation of the solid cellulose fibers of the above-mentioned starting material 1 and 60 wt.% in the calculation of the solid cellulose fibers of the above-mentioned starting material 2.}

^{Comparative example 2}

^{Kraft pulp NBKP was dispersed in deionized water to obtain a concentration of cellulose 2 wt.%. This dispersion is subjected to purifying cyclic processing in such conditions, to srednedlinny fiber length was 1.0 mm or less, using cleaning devices with dual drives. Dispersion of cellulose fibers, in which srednedlinny fiber length is 1.0 mm or less, process 10 times using high-pressure homogenizer (manufactured item LAB-1000) at a pressure of 800 bar. So get your source material 4 microfibrillated cellulose fibers. The above starting material 4 is subjected to processing using a centrifuge device for fibers, for 5 minutes with a speed of 10,000 rpm to obtain a concentration of about 6 wt.%. Sheet material thickness of 19 μm is obtained by processing formed from cellulose porous membrane in the same manner as in example 1, except the receiving using the above-mentioned starting material 4 microfibrillated cellulose fibers.}

^{Comparative example 3}

^{Sheet material with a thickness of 20 μm receive the same manner as in example 1 except for using 95 wt.% in the calculation of the solid cellulose fibers of the above-mentioned starting material 1 and 5 wt.% in the calculation of the solid cellulose fibers of the above-mentioned starting material 2.}

^{Physical properties formed from cellulose sheet materials, which were obtained in examples 1-4 and Comparative examples 1-3 are presented in table 1.}

^{The results obtained in examples 1-4 show that using the original materials microfibrillated cellulose fibers obtained what omashu homogenizer high pressure or device with abrasive blades for grinding, when specified within a certain range the proportion of thick fibers having a diameter of 1 μm or more, you can get formed from cellulose porous membrane suitable for electrochemical separators, which have a limit of tensile strength 50 N·m/g or more and a strength of raster 0,40 kN/m or more.}

^{On the other hand, Comparative example 1 shows that in case of exceeding a certain percentage of thick fibers having a diameter of 1 μm or more, the limit of the tensile strength is significantly reduced. In addition, the data of Comparative example 2 and Comparative example 3 show that in case of reduction of a certain percentage of thick fibers having a diameter of 1 μm or more, significantly reduced the strength of raster.}

^{As an example of electrochemical devices have been studied the characteristics of lithium-ion secondary battery.}

^{Example 5. Obtaining a lithium-ion secondary battery}

^{The positive electrode is obtained by preparation of a composition obtained by blending LiCoO₂, acetylene black and a solution of polyvinylidene fluoride in N-organic (Pvdf-NMP) at a mass ratio of solids 89:6:5, applying the specified composition on aluminum foil, drying and molding the composition under pressure and subsequent heat treatment of the composition. Negative electr which d is obtained by preparation of the composition, obtained by blending mesopartner microspheres graphite, acetylene black and a solution of Pvdf-NMP when the mass ratio of solids of 90:5:5, applying the specified composition on a copper foil, drying and molding the composition under pressure and subsequent heat treatment of the composition.}

^{Lithium-ion secondary battery item size: 30×50 mm, capacity: 180 mA·h) is obtained using formed from cellulose porous membrane prepared in example 1 as a separator, where the above-mentioned separator is placed between the negative electrode and the positive electrode with getting groups of electrodes, followed by placement in an aluminum casing above-mentioned groups of electrodes and 1 mol/l non-aqueous electrolytic solution obtained by dissolving LiPF₆in a mixture solvent prepared by mixing ethylene carbonate resulting and diethylmalonate in a volume ratio 3:7.}

^{The definition of quality lithium-ion secondary battery}

^{As for the lithium-ion secondary batteries obtained in example 5, it determines the internal resistance of the battery by measuring impedance to alternating current. Impedance to alternating current (Ohms) measured by the frequency analyzer model 1260 (produced by Solartron Metrology) in cacaus is the action scene in the frequency range from 10 MHz to 500 kHz and amplitude of 5 mV. The above values of the measurements are in the coordinates of equation Cole-Cole, and the real part is determined when the value of the imaginary part equal to 0. Reading reading is used as the internal resistivity (Ohms). The value of the internal resistivity of 0.125 Ohms.}

^{As an example of the electrochemical device, different from the lithium-ion secondary battery, confirmed the characteristics of the electric double-layer capacitor.}

^{Example 6. Obtaining an electric double-layer capacitor}

^{The electrode is obtained by preparation of a composition obtained by blending a mixture of activated carbon, acetylene black and tetrafluoroethylene at a mass ratio of solids of 10:1:1, followed by the application of specified composition on aluminum foil, drying and molding the composition under pressure and subsequent heat treatment of the composition.}

^{Formed from cellulose porous membrane obtained in example 1 is used as a separator, and the separator is cut into pieces, the size of which is approximately 0.5 mm larger than the size of the electrode. The electrode is formed so that the outer surface was 15 cm2. The separator is inserted between two electrodes and fill it with solution (1 mol/l) salt tetrafluoroborate tetr is ethylamine (organic electrolyte) in propylene carbonate. Thus obtained electric double-layer capacitor.}

The definition of quality electric double-layer capacitor

Define the characteristics of the electric double layer capacitor obtained in example 6. The internal resistance of the battery is determined by measuring the impedance to alternating current. Impedance to alternating current (Ohms) measured by the frequency analyzer model 1260 (produced by Solartron Metrology) in terms oscillating at frequency range from 10 MHz to 500 kHz at an amplitude of 5 mV. The above values of the measurements are in the coordinates of equation Cole-Cole, and the real part is determined when the value of the imaginary part equal to 0. Reading reading is used as the internal resistivity (Ohms). The value of the internal resistivity is 0,058 Ohms.

As described above, from the results of example 5 and example 6, you can see that the battery and the capacitor, equipped with a porous membrane formed from cellulose of the present invention, have low internal resistivity and, therefore, can be used as a battery or capacitor.

1. A porous membrane containing cellulose fibers, in which
cellulose fibers contain cellulose is fiber, having a diameter of 1 μm or more in an amount of 5 wt.% or more, based on the total weight of cellulose fibers, and
the porous membrane has an ultimate tensile strength of 50 N·m/g or more and/or has the strength to raster 0,40 kN/m or more.

2. The porous membrane under item 1, having a porosity in the range from 30 to 70%.

3. The porous membrane under item 1, in which the cellulose fibers having a diameter of 1 μm or more are contained in an amount of 5 wt.% or more and 30 wt.% or less, based on the total weight of cellulose fibers.

4. The porous membrane under item 2, in which the cellulose fibers having a diameter of 1 μm or more are contained in an amount of 5 wt.% or more and 30 wt.% or less, based on the total weight of cellulose fibers.

5. Porous membrane according to any one of paragraphs.1-4, which is obtained from a suspension containing together with the above cellulose fibers hydrophilic agent steam formation.

6. The porous membrane under item 5, in which the solubility of the specified hydrophilic agent steam formation in water is 10 wt.% or more.

7. The porous membrane under item 5, in which the specified hydrophilic agent steam formation is a simple ether glycol.

8. The porous membrane under item 6, in which the specified hydrophilic agent steam formation is a simple ether glycol.

9. Porous m is mbrane under item 5, in which the suspension contains a hydrophilic polymer binder in an amount of from 3 to 80 parts by weight per 100 parts by weight of the above cellulose fibers.

10. Porous membrane according to any one of paragraphs.6-8, in which the suspension contains a hydrophilic polymer binder in an amount of from 3 to 80 parts by weight per 100 parts by weight of the above cellulose fibers.

11. Porous membrane according to any one of paragraphs.1-4 or 6-9, having a specific volume resistance of 1500 Ohms·cm or less, as determined using an alternating current with a frequency of 20 kHz and impregnated with 1-molar solution of LiPF₆in propylene carbonate porous membrane.

12. The porous membrane under item 5, having a specific volume resistance of 1500 Ohms·cm or less, as determined using an alternating current with a frequency of 20 kHz and impregnated with 1-molar solution of LiPF₆in propylene carbonate porous membrane.

13. The porous membrane under item 10, having a specific volume resistance of 1500 Ohms·cm or less, as determined using an alternating current with a frequency of 20 kHz and impregnated with 1-molar solution of LiPF₆in propylene carbonate porous membrane.

14. Separator for electrochemical device containing the porous membrane according to any one of paragraphs.1-13.

15. Electrochemical device containing the separator for power is imicheskogo device under item 14.

16. Electrochemical device according to p. 15, which is a battery or a capacitor.

17. The method of obtaining porous membrane according to any one of paragraphs.1-3, includes stage:
applying to the substrate a suspension containing at least a hydrophilic agent steam formation and cellulose fibers containing cellulose fibers with a diameter of 1 μm or more in an amount of 5 wt.% or more per the total mass of cellulose fibres;
drying the specified suspension with obtaining a sheet material on a substrate; and
Department of the sheet material of this substrate with obtaining cellulose porous membrane.

18. The method of obtaining porous membrane under item 17, further comprising a purification step of a specified sheet material or porous membrane with an organic solvent.

19. The method of obtaining porous membrane under item 17 in which these fibers are pre microfibrillation processing by passing the pre-treated pulp suspension through the grinding of the unit with abrasive blades for grinding, in which there are several abrasive plate with abrasive grains having a size ranging from No. 16 to No. 120.

20. The method of obtaining porous membrane under item 18 in which these cellulose fibers are subjected to prewar the positive microfibrillation processing by passing the pre-treated pulp suspension through the grinding of the unit with abrasive blades for grinding, where there are several abrasive plate with abrasive grains having a size ranging from No. 16 to No. 120.

21. The method of obtaining porous membrane according to any one of paragraphs.18-20, in which these fibers are pre microfibrillation processing, during which the pre-treated slurry of pulp processed using high-pressure homogenizer.