JP5213007B2 - Battery separator and non-aqueous electrolyte battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte battery that is safe even in a high-temperature environment, and a battery separator for constituting the non-aqueous electrolyte battery.

  Lithium ion batteries, which are a type of nonaqueous electrolyte battery, are widely used as power sources for portable devices such as mobile phones and notebook personal computers because of their high energy density. As the performance of portable devices increases, the capacity of lithium ion batteries tends to increase further, and ensuring safety is important.

  In the current lithium ion battery, as a separator interposed between a positive electrode and a negative electrode, for example, a polyolefin-based porous film having a thickness of about 20 to 30 μm is used. In addition, as separator material, the constituent resin of the separator is melted below the thermal runaway temperature of the battery to close the pores, thereby increasing the internal resistance of the battery and improving the safety of the battery in the event of a short circuit. In order to ensure the so-called shutdown effect, polyethylene having a low melting point may be applied.

  By the way, as such a separator, for example, a uniaxially stretched film or a biaxially stretched film is used for increasing the porosity and improving the strength. Since such a separator is supplied as a single film, a certain strength is required in terms of workability and the like, and this is ensured by the above stretching. However, with such a stretched film, the degree of crystallinity has increased, and the shutdown temperature has increased to a temperature close to the thermal runaway temperature of the battery. Therefore, it can be said that the margin for ensuring the safety of the battery is sufficient. hard.

  Further, the film is distorted by the stretching, and there is a problem that when this is exposed to high temperature, shrinkage occurs due to residual stress. The shrinkage temperature is very close to the melting point, ie the shutdown temperature. For this reason, when a polyolefin-based porous film separator is used, when the battery temperature reaches the shutdown temperature in the case of abnormal charging, the current must be immediately decreased to prevent the battery temperature from rising. This is because if the pores are not sufficiently closed and the current cannot be reduced immediately, the battery temperature easily rises to the contraction temperature of the separator, and there is a risk of ignition due to an internal short circuit.

  As a technique for preventing such a short circuit due to thermal contraction of the separator and improving the reliability of the battery, for example, it has a porous substrate with good heat resistance, filler particles, and a resin component for ensuring a shutdown function It has been proposed to configure an electrochemical element with a separator (Patent Document 1).

International Publication No. 2006/62153

  According to the technique disclosed in Patent Document 1, it is possible to provide a battery with excellent safety in which thermal runaway hardly occurs even when abnormal overheating occurs.

  However, the characteristics required for non-aqueous electrolyte batteries such as lithium ion batteries are expected to become more advanced in the future, and separators used in such batteries will be further improved so that these requirements can be fully met. An improvement is required.

  The present invention has been made in view of the above circumstances, and its purpose is to improve the short-circuit resistance while suppressing the decrease in energy density as much as possible, and to further improve the load characteristics and An object of the present invention is to provide a battery separator that can constitute the battery.

The battery separator of the present invention were able to achieve the above object, a porous membrane having a fibrous material that does not substantially deform at least 0.99 ° C., the inorganic fine particles is not substantially deformed at least 0.99 ° C., the inorganic the ratio of the fine particles, and at 33.1% by volume or more, and have contact in the total number of the inorganic fine particles, and the number of particles less than the particle size 0.3μm of 10% or more, the number of particle size 1μm or more of the particles Is 15 % or more.

  The above-mentioned “fibrous matter that does not substantially deform at least at 150 ° C.” and “inorganic fine particles that do not substantially deform at least at 150 ° C.” are recognized as being deformed by visual observation in a state heated to 150 ° C. Meaning no fibrous and inorganic particulates.

  The particle diameters of “particles having a particle diameter of 0.3 μm or less” and “particles having a particle diameter of 1 μm or more” are 20 μm × 15 μm by observing the separator surface at a magnification of 5000 times using a scanning electron microscope (SEM). The ratio of “particles with a particle diameter of 0.3 μm or less” and the ratio of “particles with a particle diameter of 1 μm or more” in the total number of inorganic fine particles measured in the above-mentioned field of view are 20 μm × This is calculated by counting the total number of inorganic fine particles, the number of particles having a particle diameter of 0.3 μm or less, and the number of particles having a particle diameter of 1 μm or more, which are recognized in a 15 μm visual field.

  Moreover, the nonaqueous electrolyte battery which has a positive electrode, a negative electrode, a nonaqueous electrolyte solution, and the battery separator of this invention is also contained in this invention.

  According to the present invention, there are provided a nonaqueous electrolyte battery that improves short-circuit resistance and further improves load characteristics while suppressing a decrease in energy density as much as possible, and a battery separator that can constitute the battery. can do.

  The separator of the present invention comprises a porous film having a fibrous material that does not substantially deform at least 150 ° C. and inorganic fine particles that do not substantially deform at least 150 ° C. The separator of the present invention is formed of a material that hardly heat shrinks as described above, and can be manufactured by a manufacturing method in which distortion at the time of manufacturing unlike the conventional polyolefin porous film separator hardly remains in the separator. Therefore, even when the temperature in the battery rises, the thermal contraction of the separator is suppressed, and a short circuit due to contact between the positive electrode and the negative electrode is prevented. Therefore, even when the inside of the battery is abnormally overheated, the thermal runaway is suppressed, so that the battery is highly safe.

  In the separator of the present invention, even if the separator is thinned, the positive electrode and the negative electrode can be well separated, and in particular, the presence of inorganic fine particles can also prevent a short circuit that may occur when lithium dendrite is generated. Therefore, the separator of this invention can suppress the fall of energy density as much as possible.

  And the separator of this invention can also make the load characteristic of a battery favorable while ensuring the outstanding short circuit resistance by using the inorganic fine particle which has a specific particle size distribution.

  The inorganic fine particles according to the separator of the present invention contain 10% or more, preferably 15% or more, more preferably 20% or more of particles having a particle size of 0.3 μm or less in the total number of inorganic fine particles. When the number of particles having a particle size of 0.3 μm or less is too small, the filling properties of the inorganic fine particles in the separator are lowered, and the short circuit resistance of the separator is lowered. On the other hand, if there are too many particles having a particle size of 0.3 μm or less, the resistance of the battery using this separator tends to increase. Therefore, particles having a particle size of 0.3 μm or less are included in the total number of inorganic fine particles. It is preferably 90% or less, and more preferably 80% or less.

  The particle diameter of the particles having a particle diameter of 0.3 μm or less may be 0.3 μm or less, but is preferably 0.03 μm or more, and more preferably 0.1 μm or more. If the particle diameter is too small, it may be difficult to produce, or it may become an impediment to ionic conduction of the separator.

The inorganic fine particles according to the separator of the present invention has the above particle 1μm particle size, the inorganic fine particles total number, include 1 5% or more. If the number of particles having a particle diameter of 1 μm or less is too small, the resistance of a battery using this separator increases, and the load characteristics may be reduced. On the other hand, if there are too many particles having a particle size of 1 μm or more, the short circuit resistance of the separator may be lowered. Therefore, the particles having a particle size of 1 μm or more are preferably 90% or less in the total number of inorganic fine particles. 80% or less is more preferable.

  The particle diameter of the particles having a particle diameter of 1 μm or more may be 1 μm or more, but is preferably 10 μm or less, and more preferably 6 μm or less. If the particle diameter is too large, it may be difficult to adjust the thickness of the separator to be produced.

  The inorganic fine particles according to the present invention are not substantially deformed at 150 ° C., have an electrical insulating property, are electrochemically stable, and are used in the production of a non-aqueous electrolyte and a separator described later. There is no particular limitation as long as it is stable to the solvent used in the liquid composition and does not dissolve in the electrolytic solution at a high temperature. The high temperature state is specifically a temperature of 150 ° C. or higher, and may be a stable particle that does not deform or undergo a chemical composition change in the electrolyte at such a temperature.

Specific examples of such inorganic particles include the following particles, which may be used alone or in combination of two or more. For example, fine oxide particles such as iron oxide, SiO ₂ (silica), Al ₂ O ₃ (alumina), TiO ₂ , BaTiO ₂ , ZrO; nitride fine particles such as aluminum nitride and silicon nitride; calcium fluoride, barium fluoride Poorly soluble ionic crystal particles such as barium sulfate; Covalent crystal particles such as silicon and diamond; Clay particles such as talc and montmorillonite; Boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, Examples include materials derived from mineral resources such as mica or artificial products thereof. Further, the surface of conductive fine particles such as metal fine particles; oxide fine particles such as SnO ₂ and tin-indium oxide (ITO); carbon fine particles such as carbon black and graphite; Fine particles imparted with electrical insulation properties by coating with the above-mentioned material constituting non-electrically conductive inorganic fine particles) may be used. Among these inorganic fine particles, silica, alumina, alumina-silica composite oxide, and boehmite are preferable.

  The shape of the inorganic fine particles may be any of a spherical shape (true spherical shape, substantially spherical shape), a rugby ball shape, a plate shape, and the like, but a plate shape is preferable from the viewpoint of further improving the short circuit resistance of the separator. In the case of plate-like inorganic fine particles, the diameter in the major axis direction of the plate is the particle size.

  As the form of the plate-like particles, it is desirable that the aspect ratio is 5 or more, more preferably 10 or more, and 100 or less, more preferably 50 or less. Further, the average value of the ratio of the length in the major axis direction to the length in the minor axis direction (length in the major axis direction / length in the minor axis direction) of the flat plate surface of the grain is 3 or less, more preferably 2 or less and close to 1. It is desirable to be a value.

  In addition, the average value of the ratio of the length in the major axis direction to the length in the minor axis direction of the flat plate surface in the plate-like particles can be obtained, for example, by image analysis of an image taken with a scanning electron microscope (SEM). it can. Further, the above aspect ratio of the plate-like particles can also be obtained by image analysis of an image taken by SEM.

  Specific examples of these inorganic fine particles include fine-grained alumina “A-43-M (product name)” manufactured by Showa Denko, bulk silica “SQPL2 (product name)” manufactured by Kinsei Matech, and spherical particles manufactured by Admatechs. Alumina "Admafine AO-802 (product name)", Admattex's spherical silica "Admafine SO-E3 (product name)", Kawai Lime's plate-like boehmite "BMM (product name)", Nippon Light Metal Co., Ltd. Alumina “A33F (product name)” and the like are available.

  The fibrous material according to the present invention is not substantially deformed at 150 ° C., has an electrical insulating property, is electrochemically stable, and is used for manufacturing a non-aqueous electrolyte solution and a separator described in detail below. There is no particular limitation as long as the solvent used in the liquid composition used is stable. The “fibrous material” referred to in the present invention means that having an aspect ratio [length in the long direction / width (diameter) in a direction perpendicular to the long direction] of 4 or more. The aspect ratio of the fibrous material according to the present invention is preferably 10 or more.

  Specific constituent materials of the fibrous material include, for example, cellulose, modified cellulose (such as carboxymethyl cellulose), polypropylene (PP), polyester [polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT). And the like], resins such as polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyaramid, polyamideimide, and polyimide; inorganic materials (inorganic oxides) such as glass, alumina, and silica; and the like. The fibrous material may contain one kind of these constituent materials, or may contain two or more kinds. In addition to the above-described constituent materials, the fibrous material may contain various known additives (for example, an antioxidant in the case of a resin) as a constituent component. Absent.

  Although the diameter of a fibrous material should just be below the thickness of a separator, it is preferable that it is 0.01-5 micrometers, for example. If the diameter is too large, the entanglement between the fibrous materials may be insufficient, and the strength of the sheet-like material constituted by these, and consequently the strength of the separator may be reduced, making it difficult to handle. On the other hand, if the diameter is too small, the gap of the separator becomes too small, and the ion permeability tends to be lowered, and the load characteristics of the battery tend to be lowered.

  The separator of the present invention uses a type in which a large number of the above-mentioned fibrous materials are gathered to form a sheet-like material only from these fibrous materials, for example, in the form of woven fabric, nonwoven fabric, paper, A separator having a structure in which inorganic fine particles are contained in the sheet-like material may be used, or a separator having a structure in which fibrous materials and inorganic fine particles are uniformly dispersed may be used. Moreover, it can also be set as the structure which combined both said structure.

  The state of the presence of the fibrous material in the separator is, for example, that the angle of the long axis (long axis) with respect to the separator surface is preferably 30 ° or less on average, and more preferably 20 ° or less. . In particular, when the fibrous material forms a sheet-like material such as a woven fabric or a non-woven fabric, the fibrous material is preferably present in the above-described state.

  In addition, in order to give the separator a shutdown function, hot-melt fine particles that melt at 80 to 130 ° C. or swellable fine particles that can swell in a non-aqueous electrolyte and increase the degree of swelling as the temperature rises are added. Is possible. By constituting the separator using the above-described hot-melt fine particles and swellable fine particles, a so-called shutdown function can be provided in which the permeability of ions in the separator is lowered when exposed to high temperatures.

  The shutdown function in the separator of the present invention can be measured by, for example, an increase in resistance due to the temperature of the model cell. That is, a model cell including a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte is prepared, and the model cell is held in a thermostatic bath, and the internal resistance of the model cell is increased while the temperature is increased at a rate of 5 ° C./min. The temperature at which the measured internal resistance value is 10 times or more that before heating (resistance value measured at room temperature) can be evaluated as the shutdown temperature.

  Heat-melting fine particles that melt at 80 to 130 ° C., that is, heat-melting fine particles having a melting temperature of 80 to 130 ° C. measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121. In the contained separator, when the separator is exposed to 80 to 130 ° C. (or higher temperature), the heat-fusible fine particles are melted to close the voids of the separator. It can be secured more reliably. Therefore, in this case, the temperature at which the void clogging phenomenon occurs in the separator of the present invention evaluated by the above increase in internal resistance (temperature at which the internal resistance value is 5 times or more before heating) is not less than the melting point of the particles and not more than 130 ° C. It becomes.

  Specific examples of the constituent material of the heat-meltable fine particles include polyethylene (PE), copolymerized polyolefin having a structural unit derived from ethylene of 85 mol% or more, polypropylene (PP), polyolefin derivative (chlorinated polyethylene, chlorinated polypropylene, etc.) Polyolefin wax, petroleum wax, carnauba wax and the like. Examples of the copolymer polyolefin include an ethylene-vinyl monomer copolymer, more specifically, an ethylene-vinyl acetate copolymer (EVA), an ethylene-methyl acrylate copolymer, or an ethylene-ethyl acrylate copolymer. it can. Moreover, polycycloolefin etc. can also be used. The heat-fusible particles may have only one kind of these constituent materials, or may have two or more kinds. Among these, PE, polyolefin wax, or EVA having a structural unit derived from ethylene of 85 mol% or more is preferable. Further, the heat-meltable fine particles may contain various known additives (for example, antioxidants) added to the resin as necessary, in addition to the above-described constituent materials. Absent.

  The heat-meltable fine particles are not only contained in the separator, but also can be provided with a shutdown function by being present on the positive electrode side surface, the negative electrode side surface, or both surfaces of the separator.

  The particle size of the heat-meltable fine particles [number average particle diameter measured using a laser scattering particle size distribution diameter (“LA-920” manufactured by HORIBA)] is, for example, 0.001 μm or more, more preferably 0.1 μm. It is recommended that the thickness be 15 μm or less, more preferably 1 μm or less.

  Specific examples of these heat-meltable fine particles include PE emulsion “CHEMIPARL (product name)” manufactured by Mitsui Chemicals, PE emulsion “K143 (product name)” manufactured by Chukyo Yushi Co., Ltd., PE wax manufactured by Gifu Shellac Co., Ltd. Emulsions, PE “Flow beads (product name)” manufactured by Sumitomo Seika Co., Ltd., wax emulsion “Aqua Petro (product name)” manufactured by Toyo Petrolite Co., Ltd., etc. are available.

  When the separator has swellable fine particles that can swell in a non-aqueous electrolyte and increase in degree of swelling as the temperature rises, the non-aqueous electrolysis is caused by swelling of the swellable fine particles when exposed to high temperatures in the battery. By absorbing the liquid and expanding greatly (hereinafter, the function of increasing the degree of swelling with increasing temperature in the swellable fine particles is called “thermal swelling”), the conductivity of Li (lithium) ions in the separator is increased. Since it is significantly reduced, the internal resistance of the battery is increased, and the above-described shutdown function can be reliably ensured. As the swellable fine particles, those having a temperature of 75 to 125 ° C. exhibiting the above heat swellability are preferable.

  Examples of such swellable fine particles having thermal swellability include crosslinked polystyrene (PS), crosslinked acrylic resin [for example, crosslinked polymethyl methacrylate (PMMA)], and crosslinked fluororesin [for example, crosslinked polyvinylidene fluoride (PVDF). ] Is preferred, and cross-linked PMMA is particularly preferred.

  The particle size of the swellable fine particles is a number average particle size measured by dispersing the fine particles in a non-swelling medium (for example, water) using a laser scattering particle size distribution meter (for example, “LA-920” manufactured by HORIBA). It is preferable that it is 1-20 micrometers.

  As specific examples of the swellable fine particles, cross-linked PMMA “Gantz Pearl (product name)” manufactured by Gantz Kasei Co., Ltd., and cross-linked PMMA “RSP1079 (product name)” manufactured by Toyo Ink Co., Ltd. are available.

  In the separator of this invention, when ensuring a shutdown function, either the said heat-meltable microparticles | fine-particles or the said swellable microparticles | fine-particles may be contained, and both may be contained. Furthermore, the shutdown function may be ensured by adding a composite containing the heat-meltable fine particles and the heat-swellable fine particles to the separator.

  In the separator of the present invention, for the purpose of binding inorganic fine particles to each other, or binding the fibrous material with inorganic fine particles and other various particles (such as the above-mentioned heat-meltable fine particles and swellable fine particles). A binder may be used.

  Any binder may be used as long as it is electrochemically stable and stable with respect to the non-aqueous electrolyte, and can be satisfactorily bonded. For example, EVA (having 20 to 35 mol% of a structural unit derived from vinyl acetate) , Ethylene-acrylate copolymers such as ethylene-ethyl acrylate copolymer, various rubbers and derivatives thereof [styrene-butadiene rubber (SBR), fluororubber, urethane rubber, ethylene-propylene-diene rubber (EPDM), etc.], cellulose derivatives [Carboxymethylcellulose (CMC), hydroxyethylcellulose, hydroxypropylcellulose, etc.], polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), polyurethane, epoxy resin, PVDF, vinylidene fluoride-hexafluo Propylene copolymer (PVDF-HFP), and acrylic resins. May be used these alone, or in combination of two or more. In addition, when using these binders, it can be used in the form of the emulsion which melt | dissolved or disperse | distributed to the solvent of the liquid composition for separator formation mentioned later.

  As specific examples of these binders, SBR “TRD2001 (product name)” manufactured by JSR, SBR “BM400B (product name)” manufactured by Zeon Corporation, and the like are available.

  The separator of the present invention may have a form of an independent porous film, or may have a form integrated with at least one of a positive electrode and a negative electrode used in a battery.

  The thickness of the separator is 3 μm or more, more preferably 5 μm or more, and is preferably 50 μm or less, more preferably 30 μm or less. If the separator is too thin, the short-circuit prevention effect may be reduced, or the separator may have insufficient strength and may be difficult to handle. On the other hand, if it is too thick, the energy density of the battery tends to be reduced.

Further, the porosity of the separator is preferably 15% or more, more preferably 20% or more, and 70% or less, more preferably 60% or less in a dry state. If the porosity of the separator is too small, the ion permeability may be reduced, and if the porosity is too large, the strength of the separator may be insufficient. The porosity of the separator: P (%) can be calculated by calculating the sum of each component i from the thickness of the separator, the mass per area, and the density of the constituent components using the following formula.
P = Σa _i ρ _i / (m / t)
Here, in the above formula, a _i : ratio of component i expressed by mass%, ρ _i : density of component i (g / cm ³ ), m: mass per unit area of separator (g / cm ² ), t: thickness of separator (cm).

Furthermore, the air permeability of the separator, which is performed by a method in accordance with JIS P 8117 and indicated by a Gurley value indicated by the number of seconds in which 100 ml of air passes through the membrane under a pressure of 0.879 g / mm ² , is 10 to 10. It is desirable to be 300 sec. If the air permeability is too high, the ion permeability is reduced, whereas if it is too low, the strength of the separator may be reduced. When the separator is an independent film, the strength is preferably 50 g or more in terms of puncture strength using a needle having a diameter of 1 mm. If the piercing strength is too low, a short circuit may occur due to the breakthrough of the separator when lithium dendrite crystals are generated.

Inorganic fine particles in the separator, the total volume of the components of the separator, Ru der least 33.1% by volume. By making the volume ratio of the inorganic fine particles as described above, the effect of using the inorganic fine particles can be more effectively exhibited.

  On the other hand, the upper limit of the volume ratio of the inorganic fine particles in the separator is preferably 80% by volume, for example, in the total volume of the constituent components of the separator. When the volume ratio of the inorganic fine particles exceeds the above upper limit, it is difficult to make the separator have a configuration that can sufficiently secure the shutdown function while sufficiently securing the short-circuit prevention function. In addition, when it is set as the structure which does not provide a shutdown function to a separator, there will be no problem if the volume ratio of the inorganic fine particles in the whole volume of the component of a separator is a still higher ratio, for example, 95 volume% or less.

  Moreover, it is preferable that the fibrous material in a separator is 20 volume% or more in the whole volume of the component of a separator, and it is more preferable that it is 30 volume% or more. By making the volume ratio of the fibrous material as described above, the effect of using the fibrous material can be more effectively exhibited.

  On the other hand, if the volume ratio of the fibrous material in the separator is too large, the ratio of inorganic fine particles and other particles (such as heat-meltable fine particles and swellable fine particles) becomes small, and the effects of these cannot be fully exhibited. Since there exists a possibility, it is preferable that the volume ratio of the fibrous material in the whole volume of the structural component of a separator is 70 volume% or less, and it is more preferable that it is 60 volume% or less.

  Further, in the separator, the total volume of the heat-meltable fine particles and the swellable fine particles is preferably 10 to 50% by volume in the total volume of the constituent components of the separator. By including the heat-meltable fine particles and the swellable fine particles in the above range, a good shutdown function can be ensured without impairing the action of the inorganic fine particles and the fibrous material. Moreover, it is preferable that a binder is 1-10 volume% in the whole volume of the structural component of a separator.

  As the method for producing the separator of the present invention, for example, the following methods (I), (II) and (III) can be employed. The method (I) is a production method in which a liquid composition (slurry or the like) containing inorganic fine particles is applied to or impregnated into an ion-permeable sheet material and then dried at a predetermined temperature.

  The “sheet-like material” referred to in the method (I) corresponds to the above-described sheet-like materials composed of fibrous materials (various, woven fabric, non-woven fabric, etc.). That is, a porous sheet such as a non-woven fabric having a structure in which each of the above-exemplified materials is composed of at least one kind of fibrous material, and the fibrous materials are entangled with each other. More specifically, non-woven fabrics such as paper, PP non-woven fabric, polyester non-woven fabric (PET non-woven fabric, PEN non-woven fabric, PBT non-woven fabric, etc.), PAN non-woven fabric, and PVA non-woven fabric can be exemplified.

The thickness of the woven or non-woven fabric used for the separator is preferably 20 μm or less, and more preferably 10 μm or less. As the basis weight of the woven or nonwoven fabric, more preferably preferably at 15 g / ^{m 2} or less, 10 g / ^{m 2} or less. Incidentally, the woven fabric or nonwoven fabric thickness is preferably 5μm or more, the basis weight is preferably 2 g / m ² or more. As a method for producing a woven fabric or a non-woven fabric, a conventionally known method can be used. For example, for a non-woven fabric, methods such as wet, dry, melt blow, spun bond, and charge melt spinning can be used.

  The liquid composition for forming the separator of the present invention contains inorganic fine particles and, if necessary, a binder, hot-melt fine particles, etc., and these are dispersed in a solvent (including a dispersion medium, hereinafter the same). It has been dissolved. The solvent used in the liquid composition may be any solvent that can uniformly disperse inorganic fine particles, heat-meltable fine particles, and the like, and can uniformly dissolve or disperse the binder. For example, aromatic hydrocarbons such as toluene Organic solvents such as furans such as tetrahydrofuran; ketones such as methyl ethyl ketone and methyl isobutyl ketone; In addition, for the purpose of controlling the interfacial tension, alcohols (ethylene glycol, propylene glycol, etc.) or various propylene oxide glycol ethers such as monomethyl acetate may be appropriately added to these solvents. In addition, when the binder is water-soluble or used as an emulsion, water may be used as a solvent. In this case, an alcohol (methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, etc.) is added as appropriate to the interface. The tension can also be controlled.

  In the liquid composition, the solid content including inorganic fine particles, heat-meltable fine particles, binder, and the like is preferably 10 to 80% by mass, and more preferably 20 to 70% by mass.

  In addition, when a hot-melt fine particle has adhesiveness independently, these can also serve as a binder.

  In the case of the separator having the sheet-like material, it is preferable that part or all of the fine particles such as inorganic fine particles, heat-meltable fine particles, and swellable fine particles exist in the voids of the sheet-like material. When the separator has such a structure, the action of the contained fine particles is more effectively exhibited. In addition, the sheet-like material is composed of a fibrous material, such as a nonwoven fabric such as paper, PP nonwoven fabric, and polyester nonwoven fabric, and particularly when the opening diameter of the void is relatively large (for example, the void This is likely to cause a short circuit of the battery. Therefore, particularly in this case, it is preferable to have a structure in which some or all of the fine particles to be mixed are present in the voids of the sheet-like material.

  In order to make various fine particles such as inorganic fine particles exist in the voids of the sheet-like material, for example, after impregnating the above liquid composition into the sheet, passing through a certain gap, and removing the excess liquid composition, A process such as drying may be used.

  When using plate-like particles as the inorganic fine particles, the orientation of the plate-like particles in the separator is enhanced, and the plate-like particles are oriented parallel or substantially parallel to the separator surface, thereby preventing the penetration of the separator by dendrites. Therefore, the occurrence of a short circuit can be satisfactorily suppressed. In order to increase the orientation of the plate-like particles in the separator and to make the function work effectively, a method in which a shear or magnetic field is applied to the liquid composition in the substrate impregnated with the liquid composition is used. That's fine. For example, as described above, the liquid composition can be sheared by impregnating the liquid composition into a sheet and then passing through a certain gap.

  The separator (II) is produced by adding a fibrous material to the liquid composition, coating the substrate on a substrate such as a film or a metal foil, and drying at a predetermined temperature. It is a method of peeling. That is, it is a method of simultaneously performing the operation of forming a sheet of fibrous material and containing inorganic fine particles. The liquid composition used in the method (II) is the same as the liquid composition used in the method (I) except that it is essential to contain a fibrous material. Moreover, it is desirable that the separator obtained by the method (II) also has a structure in which some or all of the inorganic fine particles are present in the voids of the sheet-like material formed of the fibrous material.

  The method for producing the separator (III) is, for example, a slurry in which the above-described inorganic fine particles and fibrous materials are further dispersed in water or a suitable solvent using hot-melt fine particles or a binder as necessary. This is a method of preparing a liquid composition, applying the liquid composition on an electrode (positive electrode or negative electrode) using a conventionally known coating apparatus such as a blade coater, a roll coater, a die coater, or a spray coater, and drying it. . Thereby, the separator of the structure integrated with the electrode can be obtained. As the liquid composition, for example, the same liquid composition as described for the production method of (I) or (II) can be used.

  In addition, the separator of this invention is not limited to said structure. For example, the inorganic fine particles may not be present independently of each other, and may be partially fused to each other or to a fibrous material.

  The separator produced by the methods (I) to (III) is preferably subjected to a heat treatment after drying to remove volatile components such as moisture and a solvent (dispersion medium) contained in the separator. By removing these volatile components, in the nonaqueous electrolyte battery, it is possible to suppress deterioration of battery characteristics when charging and discharging are repeated, so that it is possible to provide a nonaqueous electrolyte battery having excellent long-term reliability. The residual amount of moisture and solvent is desirably 100 ppm or less with respect to the separator.

  The temperature of the heat treatment is set to a temperature lower than the shutdown temperature of the porous layer when the meltable fine particles are contained in the separator. When heat treatment is performed at a temperature equal to or higher than the shutdown temperature, the pores of the porous layer are blocked, so that the characteristics of the nonaqueous electrolyte battery using such an electrode are inferior. In the case of a separator that does not contain hot-melt fine particles and has a shutdown function due to the use of swellable fine particles, even if the separator is heated and exposed to high temperatures, the swellable fine particles are heated if cooled afterwards. Since it returns to the previous state, the characteristics of the separator (such as ion permeability) are not impaired. Therefore, in the separator having swellable fine particles, the heat treatment temperature is not particularly limited as long as the temperature is equal to or lower than the thermal decomposition temperature of the resin constituting the swellable fine particles and the fibrous material. Moreover, the heat processing temperature should just be below the thermal decomposition temperature of a fibrous material also about the separator which does not use a thermomeltable microparticle and does not provide the shutdown function, for example.

  The specific heat treatment temperature is, for example, 70 to 140 ° C., and the heat treatment time is, for example, 1 hour or more, more preferably 3 hours or more, and 72 hours or less, more preferably 24 hours or less. It is desirable to do. Such heat treatment can be performed, for example, in a warm air circulation type thermostatic bath. Moreover, you may dry under reduced pressure using a vacuum dryer as needed.

  The separator thus obtained can have a thermal shrinkage rate of, for example, less than 5% at 150 ° C., and heat shrinkage at high temperatures is unlikely to occur. The occurrence of a short circuit can be suppressed by separating the negative electrode well. The “150 ° C. heat shrinkage rate” of the separator refers to the size of the separator before putting the separator in a thermostatic bath, raising the temperature to 150 ° C. and leaving it for 30 minutes, and then putting it in the thermostatic bath. The reduction ratio of the dimension calculated | required by this is expressed in percentage.

  The nonaqueous electrolyte battery of the present invention is not particularly limited as long as it has the separator of the present invention, and a conventionally known configuration and structure can be adopted. In addition, although the primary battery and the secondary battery are contained in the nonaqueous electrolyte battery of this invention, the structure of the secondary battery which is especially main uses is illustrated below.

  Examples of the form of the nonaqueous electrolyte battery include a cylindrical shape (such as a rectangular tube shape or a cylindrical shape) using a steel can, an aluminum can, or the like as an outer can. Moreover, it can also be set as the soft package battery which used the laminated film which vapor-deposited the metal as an exterior body.

The positive electrode is not particularly limited as long as it is a positive electrode used in a conventionally known nonaqueous electrolyte battery. For example, as an active material, lithium-containing transition metal oxide represented by Li _{1 + x} MO ₂ (−0.1 <x <0.1, M: Co, Ni, Mn, etc.); lithium manganese such as LiMn ₂ O ₄ Oxide; LiMn _x M _(1-x) O _{2 in} which part of Mn of LiMn ₂ O ₄ is substituted with another element; olivine type LiMPO ₄ (M: Co, Ni, Mn, Fe); LiMn _0.5 Ni _0.5 O ₂ ; Li _{(1 + a)} Mn _x Ni _y Co _(1-xy) O ₂ (−0.1 <a <0.1, 0 <x <0.5, 0 <y <0. 5); can be applied, and a positive electrode mixture in which a known conductive additive (carbon material such as carbon black) or a binder such as PVDF is appropriately added to these positive electrode active materials, Using a current collector as a core material and forming a molded body That.

  As the current collector of the positive electrode, a metal foil such as aluminum, a punching metal, a net, an expanded metal, or the like can be used. Usually, an aluminum foil having a thickness of 10 to 30 μm is preferably used.

  The lead portion on the positive electrode side is normally provided by leaving the exposed portion of the current collector without forming the positive electrode mixture layer on a part of the current collector and forming the lead portion at the time of producing the positive electrode. However, the lead portion is not necessarily integrated with the current collector from the beginning, and may be provided by connecting an aluminum foil or the like to the current collector later.

  The negative electrode is not particularly limited as long as it is a negative electrode used in a conventionally known nonaqueous electrolyte battery. For example, carbon that can occlude and release lithium, such as graphite, pyrolytic carbons, cokes, glassy carbons, fired organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers as active materials One type or a mixture of two or more types of system materials is used. In addition, elements such as Si, Sn, Ge, Bi, Sb and In and alloys thereof, lithium-containing nitrides, oxides and other compounds that can be charged and discharged at a low voltage close to lithium metal, or lithium metals and lithium / aluminum alloys Can also be used as a negative electrode active material. A negative electrode mixture prepared by appropriately adding a conductive additive (carbon material such as carbon black) or a binder such as PVDF to these negative electrode active materials and using a current collector as a core material is used. In addition, the above-mentioned various alloys and lithium metal foils may be used alone or formed on a current collector.

  When a current collector is used for the negative electrode, a copper or nickel foil, a punching metal, a net, an expanded metal, or the like can be used as the current collector, but a copper foil is usually used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is preferably 5 μm.

  Similarly to the lead portion on the positive electrode side, the negative electrode lead portion is usually exposed to the current collector without forming a negative electrode agent layer (a layer having a negative electrode active material) on a part of the current collector during negative electrode fabrication. It is provided by leaving a part and using it as a lead part. However, the lead portion on the negative electrode side is not necessarily integrated with the current collector from the beginning, and may be provided by connecting a copper foil or the like to the current collector later.

  The electrode can be used in the form of a laminate in which the above positive electrode and the above negative electrode are laminated via the separator of the present invention, or a wound electrode body in which this is wound. In addition, in the wound electrode body, defects such as cracks and dropping off of fine particles such as inorganic fine particles are likely to occur in the separator. In addition, in the case of using a laminate film exterior body or a rectangular exterior can, Since the flattened shape is used, a separator defect is particularly likely to occur. In a battery configured using a wound electrode body in which the above-described defects are generated in the separator, the characteristics are inferior. However, in the separator of the present invention, even if the flat wound electrode body as described above is configured, the above-described defects are not easily generated, and thus a non-aqueous electrolyte battery excellent in reliability can be configured.

Examples of the non-aqueous electrolyte include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propionate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, ethylene glycol sulfite, 1,2-dimethoxyethane, 1, 3-dioxolane, tetrahydrofuran, 2-methyl - tetrahydrofuran, one composed of only an organic solvent such as diethyl ether or a mixture of two or more solvents, for _{example, LiClO 4, LiPF 6, LiBF} 4, LiAsF 6, LiSbF 6, _{LiCF 3 SO 3, LiCF 3 CO} 2, Li 2 C 2 F 4 (SO 3) 2, LiN (CF 3 SO 2) 2, LiC (CF 3 SO 2) 3, LiC n F 2n + 1 SO 3 (n ≧ ), LiN (RfOSO ₂₎ those ₂ [here Rf of fluoroalkyl group] was prepared by dissolving at least one selected from lithium salts such as are used. The concentration of the lithium salt in the electrolytic solution is preferably 0.5 to 1.5 mol / l, and more preferably 0.9 to 1.25 mol / l.

  In addition, instead of the above organic solvent, melting at room temperature such as ethyl-methylimidazolium trifluoromethylsulfonium imide, heptyl-trimethylammonium trifluoromethylsulfonium imide, pyridinium trifluoromethylsulfonium imide, guanidinium trifluoromethylsulfonium imide A salt can also be used.

  Furthermore, PVDF, PVDF-HEP, PAN, polyethylene oxide, polypropylene oxide, an ethylene oxide-propylene oxide copolymer, a crosslinked polymer containing an ethylene oxide chain in the main chain or side chain, and a crosslinked poly (meta) An electrolyte gelled using a known host polymer capable of forming a gel electrolyte such as an acrylate ester can also be used.

  The nonaqueous electrolyte battery of the present invention can be applied to the same uses as various uses in which conventionally known nonaqueous electrolyte batteries are used.

Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention. Of the examples described later, Examples 1 and 3 correspond to Examples of the present invention.

Example 1
1000 g of water, 1000 g of silica pulverized product as inorganic fine particles, and SBR latex (3 parts by mass of SBR solid content with respect to 100 parts by mass of inorganic fine particles) as a binder are put in a container and dispersed by stirring for 1 hour with a three-one motor. A slurry was obtained. The particle size distribution of the silica pulverized product was D ₁₀ = 0.284 μm, D ₅₀ = 0.589 μm, and D ₉₀ = 1.343 μm. A nonwoven fabric made of PET having a thickness of 15 μm was passed through the slurry, and the slurry was applied by pulling up and then dried to produce a separator having a thickness of 20 μm.

  The manufactured separator surface was observed by SEM at a magnification of 5000 times. At this time, the ratio of the inorganic fine particles having a particle diameter of 0.3 μm or less and the inorganic fine particles having a particle diameter of 1 μm or more that can be confirmed in a visual field of 20 μm × 15 μm to the total number of inorganic fine particles was 20% and 15%, respectively.

For the above separator, the volume content of the inorganic fine particles calculated with the specific gravity of silica being inorganic fine particles being 2.2 g / cm ³ , the specific gravity of the binder being 1 g / cm ³ , and the specific gravity of PET being 1.38 g / cm ³ is 33.8%.

Example 2
The inorganic fine particles were mixed with 500 g of plate boehmite having a large particle diameter (D ₁₀ = 0.393 μm, D ₅₀ = 0.959 μm, D ₉₀ = 1.767 μm, aspect ratio 10), and plate boehmite having a small particle diameter (D ₁₀ = 0.132 µm, D ₅₀ = 0.355 µm, D ₉₀ = 1.030 µm, aspect ratio 20) A separator was prepared in the same manner as in Example 1 except that the mixture was changed to 500 g. SEM observation confirmed that the plate-like boehmite having a large particle diameter and the plate-like boehmite having a small particle diameter were plate-like.

  For the above separator, the ratio of the inorganic fine particles having a particle diameter of 0.3 μm or less and the inorganic fine particles having a particle diameter of 1 μm or more determined by SEM observation under the same conditions as in Example 1 to the total number of inorganic fine particles was 13 respectively. %, 31%.

For the above separator, the volume content of the inorganic fine particles calculated by setting the specific gravity of boehmite, which is inorganic fine particles, as 3.0 g / cm ³ , the specific gravity of the binder as 1 g / cm ³ , and the specific gravity of PET as 1.38 g / cm ³ , 32.6%.

Example 3
The inorganic fine particles were obtained by adding 800 g of plate-like boehmite having a large particle diameter (D ₁₀ = 0.393 μm, D ₅₀ = 0.959 μm, D ₉₀ = 1.767 μm, aspect ratio 10) and plate-like boehmite having a small particle diameter (D ₁₀ = 0.132 µm, D ₅₀ = 0.355 µm, D ₉₀ = 1.030 µm, aspect ratio 20) A separator was prepared in the same manner as in Example 1 except that the mixture was changed to 500 g.

  For the above separator, the ratio of the inorganic fine particles having a particle diameter of 0.3 μm or less and the inorganic fine particles having a particle diameter of 1 μm or more determined by SEM observation under the same conditions as in Example 1 to the total number of inorganic fine particles is 11%, 42%.

In addition, with respect to the separator described above, the volume content of the inorganic fine particles calculated by setting the specific gravity of boehmite, which is inorganic fine particles, as 3.0 g / cm ³ , the specific gravity of the binder as 1 g / cm ³ , and the specific gravity of PET as 1.38 g / cm ^3. Is 33.1%.

Example 4
200 g of inorganic fine particles and plate boehmite (D ₁₀ = 0.393 μm, D ₅₀ = 0.959 μm, D ₉₀ = 1.767 μm, aspect ratio 10) with large particle diameter and plate boehmite with small particle diameter (D ₁₀ = 0.132 µm, D ₅₀ = 0.355 µm, D ₉₀ = 1.030 µm, aspect ratio 20) A separator was prepared in the same manner as in Example 1 except that 800 g was mixed.

  For the above separator, the ratio of the inorganic fine particles having a particle diameter of 0.3 μm or less and the inorganic fine particles having a particle diameter of 1 μm or more determined by SEM observation under the same conditions as in Example 1 is 20%, 28%.

In addition, with respect to the separator described above, the volume content of the inorganic fine particles calculated by setting the specific gravity of boehmite, which is inorganic fine particles, as 3.0 g / cm ³ , the specific gravity of the binder as 1 g / cm ³ , and the specific gravity of PET as 1.38 g / cm ^3. Is 31.3%.

Example 5
570 g of plate-like alumina (D ₁₀ = 0.426 μm, D ₅₀ = 1.412 μm, D ₉₀ = 2.107 μm, aspect ratio 25) and inorganic boehmite (D ₁₀ = 0.132 μm). , D ₅₀ = 0.355 μm, D ₉₀ = 1.030 μm, aspect ratio 20) A separator was produced in the same manner as in Example 1 except that the mixture was changed to 430 g.

  For the above separator, the ratio of the inorganic fine particles having a particle diameter of 0.3 μm or less and the inorganic fine particles having a particle diameter of 1 μm or more determined by SEM observation under the same conditions as in Example 1 to the total number of inorganic fine particles is 11%, 56%.

Further, for the above separator, an inorganic fine particle α-alumina specific gravity 3.98 g / cm ^3, and a specific gravity of boehmite 3.0 g / cm ^3, the specific gravity of the specific gravity of the binder 1g ^/ cm 3, PET 1.38g The volume content of plate alumina calculated as / cm ³ is 25.6%, the volume content of plate boehmite is 6.4%, and the volume content of all inorganic fine particles is 32.0%. .

Example 6
249 g of spherical fine particles (D ₁₀ = 0.242 μm, D ₅₀ = 0.487 μm, D ₉₀ = 1.06 μm) and inorganic boehmite (D ₁₀ = 0.393 μm, D ₅₀ = 0) A separator was produced in the same manner as in Example 1 except that the mixture was changed to a mixture of .959 μm, D ₉₀ = 1.767 μm, and aspect ratio 10) 751 g.

  For the above separator, the ratio of the inorganic fine particles having a particle diameter of 0.3 μm or less and the inorganic fine particles having a particle diameter of 1 μm or more determined by SEM observation under the same conditions as in Example 1 to the total number of inorganic fine particles is 11%, 40%.

Further, for the above separator, alumina specific gravity 3.98 g / cm ³ of an inorganic fine particle, the specific gravity of boehmite 3.0 g / cm ^3, the specific gravity of the specific gravity of the binder 1g ^/ cm 3, PET 1.38g ^/ The volume content of spherical alumina calculated as cm ³ is 6.2%, the volume content of plate boehmite is 24.9%, and the volume content of all inorganic fine particles is 31.1%.

Example 7
406 g of spherical fine particles (D ₁₀ = 0.242 μm, D ₅₀ = 0.487 μm, D ₉₀ = 1.06 μm) and bulk silica (D ₁₀ = 0.284 μm, D ₅₀ = 0.589 μm, D ₉₀₎ = 1.343 μm) A separator was produced in the same manner as in Example 1 except that the mixture was changed to a mixture of 594 g.

  For the above separator, the ratio of the inorganic fine particles having a particle size of 0.3 μm or less and the inorganic fine particles having a particle size of 1 μm or more determined by SEM observation under the same conditions as in Example 1 was 18%, 11%.

Further, for the above separator, alumina specific gravity 3.98 g / cm ³ of an inorganic fine particle, the specific gravity of silica 2.2 g / cm ^3, the specific gravity of the specific gravity of the binder 1g ^/ cm 3, PET 1.38g ^/ The volume content of spherical alumina calculated as cm ³ is 6.6%, the volume content of silica is 26.5%, and the volume content of all inorganic fine particles is 33.1%.

Examples 8-14
Separators were produced in the same manner as in Examples 1 to 7, except that 250 g of PE fine particles (average particle size 0.6 μm, melting point 118 ° C.) were further added as heat-meltable fine particles during slurry preparation.

For the separators of Examples 8 to 14, the ratio of the inorganic fine particles having a particle diameter of 0.3 μm or less and the inorganic fine particles having a particle diameter of 1 μm or more determined by SEM observation under the same conditions as in Example 1 to the total number of inorganic fine particles, Table 1 shows. In addition, with respect to the separators of Examples 8 to 14, the volume content of inorganic fine particles obtained in the same manner as in the separators of Examples 1 to 7 except that the specific gravity of the PE fine particles was 1 g / cm ³ is also shown in Table 1. To do.

Comparative Example 1
1000 g of water, 1000 g of spherical silica as inorganic fine particles, and SBR latex (3 parts by mass of SBR solid content with respect to 100 parts by mass of inorganic fine particles) as a binder are placed in a container and dispersed by stirring for 1 hour with a three-one motor. Got. The particle size distribution of the spherical silica was D ₁₀ = 0.396 μm, D ₅₀ = 0.874 μm, D ₉₀ = 1.205 μm. Moreover, SEM observation of the spherical silica confirmed that the shape was spherical.

  A non-woven fabric made of PET having a thickness of 15 μm was passed through the slurry, and the slurry was applied by pulling up and then dried to prepare a separator having a thickness of 20 μm.

  For the above separator, the ratio of the inorganic fine particles having a particle diameter of 0.3 μm or less and the inorganic fine particles having a particle diameter of 1 μm or more determined by SEM observation under the same conditions as in Example 1 to the total number of inorganic fine particles was 7%. 28%.

For the above separator, the volume content of the inorganic fine particles calculated with the specific gravity of silica being inorganic fine particles being 2.2 g / cm ³ , the specific gravity of the binder being 1 g / cm ³ , and the specific gravity of PET being 1.38 g / cm ³ is 28.5%.

Comparative Example 2
A separator was produced in the same manner as in Comparative Example 1 except that the inorganic fine particles were changed to 1000 g of spherical alumina (D ₁₀ = 0.242 μm, D ₅₀ = 0.487 μm, D ₉₀ = 1.06 μm).

  For the above separator, the ratio of the inorganic fine particles having a particle diameter of 0.3 μm or less and the inorganic fine particles having a particle diameter of 1 μm or more determined by SEM observation under the same conditions as in Example 1 to the total number of inorganic fine particles is 13%, It was 8%.

In addition, with respect to the separator described above, the volume content of the inorganic fine particles calculated by setting the specific gravity of alumina as inorganic fine particles to 4.0 g / cm ³ , the specific gravity of the binder as 1 g / cm ³ , and the specific gravity of PET as 1.38 g / cm ^3. Is 28.2%.

Comparative Example 3
1000 g of fine inorganic particles separated from the pulverized silica used in Example 1 by sedimentation separation (D ₁₀ = 0.487 μm, D ₅₀ = 0.959 μm, D ₉₀ = 1.587 μm, aspect ratio 10) A separator was produced in the same manner as in Comparative Example 1 except that the above was changed.

  For the above separator, the proportion of the inorganic fine particles having a particle diameter of 0.3 μm or less and the inorganic fine particles having a particle diameter of 1 μm or more determined by SEM observation under the same conditions as in Example 1 is 3%, respectively. 53%.

In addition, for the separator described above, the volume content of the inorganic fine particles calculated with the specific gravity of silica being inorganic fine particles being 2.2 g / cm ³ , the specific gravity of the binder being 1 g / cm ³ , and the specific gravity of PET being 1.38 g / cm ^3. Is 28.6%.

  In Table 1, the structure of the separator of Examples 1-14 and Comparative Examples 1-3 is shown. Moreover, about the separator of Examples 1-14 and Comparative Examples 1-3, an air permeability was measured with the following method, and also about the separator of Examples 8-14 containing the heat-meltable fine particle, the following shutdown was carried out. Characterization was performed. These results are shown in Table 2 together with the porosity of the separator.

<Air permeability of separator>
The air permeability of the separator was evaluated by a Gurley value measured by a method according to JIS P 8117 and indicated by the Gurley value indicated by the number of seconds for 100 ml of air to pass through the membrane under a pressure of 0.879 g / mm ² .

<Separator shutdown characteristics>
Each separator piece cut to a size of 4 cm x 4 cm is sandwiched between two stainless steel plates with terminals, inserted into a bag of aluminum laminate film, injected with a non-aqueous electrolyte, and then the tip of the terminal is placed outside the bag. The bag was sealed in the state where it was taken out, and it was set as the sample for a test. Here, as the non-aqueous electrolyte, a solution in which LiPF ₆ was dissolved at a concentration of 1.2 mol / l in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2 was used. The sample was placed in a thermostat, heated by increasing the temperature from room temperature at a rate of 1 ° C. per minute while measuring the resistance when a 1 kHz alternating current was applied to the terminal with a contact resistance meter. The temperature change was determined. The temperature at which the resistance value was 10 times or more the value at room temperature was taken as the shutdown temperature of the separator.

  Furthermore, about the separator of Examples 1-14 and Comparative Examples 1-3, the short circuit resistance was evaluated by the following method. These results are shown in Table 3.

<Short-circuit resistance>
The separators of Examples 1 to 14 or Comparative Examples 1 to 3 were punched into a circle with a diameter of 23 mm, and the separator pieces were punched into a metal lithium side of a stainless steel plate to which metal lithium punched into a circle of 18 mm was attached and a circle of 18 mm. It was sandwiched with copper foil and placed in the center of a stainless steel cell. Here, as a nonaqueous electrolyte solution, a solution in which LiPF ₆ was dissolved at a concentration of 1.2 mol / l was poured into a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 2 as a non-aqueous electrolyte. The lid was completely covered with a uniform weight applied from the top of the plate with a winding spring. In addition, about this cell, the copper foil side and the metal lithium side were in the state electrically insulated, The terminal was connected to each using the metal lithium side as the positive electrode and the copper foil side as the negative electrode.

  For the model cell created in this way, the upper limit of the current value is set to 60 mA, Li electrodeposition is performed on the copper foil while increasing at a rate of 0 mA to 6 mA / 6 min, and the current when the short circuit is confirmed is the short circuit current. It was. That is, it can be said that the larger the short circuit current, the better the short circuit resistance of the separator.

Example 15
<Production of negative electrode>
A negative electrode mixture-containing paste was prepared by mixing 95 parts by mass of graphite as a negative electrode active material and 5 parts by mass of PVDF as a binder so as to be uniform using NMP as a solvent. This negative electrode mixture-containing paste was intermittently applied to both sides of a 10 μm thick current collector made of copper foil so that the active material application length was 320 mm on the front surface and 260 mm on the back surface, dried, and then subjected to calendar treatment. The thickness of the negative electrode mixture was adjusted so that the total thickness was 142 μm, and the negative electrode mixture was cut to have a width of 45 mm to produce a negative electrode having a length of 330 mm and a width of 45 mm. Further, a tab was welded to the exposed portion of the copper foil of the negative electrode to form a lead portion.

<Preparation of positive electrode>
LiPoO _{2 as a} positive electrode active material: 85 parts by mass, 10 parts by mass of acetylene black as a conductive additive, and 5 parts by mass of PVDF as a binder are mixed so as to be uniform using NMP as a solvent, and a positive electrode mixture The containing paste was adjusted. This paste is intermittently applied to both sides of a 15 μm thick aluminum foil serving as a current collector so that the active material application length is 320 mm on the front surface and 260 mm on the back surface, dried, and then subjected to a calendar treatment to obtain a total thickness. The thickness of the positive electrode mixture layer was adjusted to 150 μm and then cut to produce a positive electrode having a length of 330 mm and a width of 43 mm. Further, a tab was welded to the exposed portion of the aluminum foil of the positive electrode to form a lead portion.

<Battery assembly>
The positive electrode and the negative electrode obtained as described above were spirally wound through the separator of Example 1 slit to a width of 47 mm to obtain a wound electrode body. The wound electrode body is crushed into a flat shape, loaded in a laminate film exterior material, and an electrolyte solution (LiPF ₆ in a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 1: 2 is 1 mol / l. A solution dissolved at a concentration) was injected, and vacuum sealing was performed to prepare a nonaqueous electrolyte battery.

Examples 16 to 28 and Comparative Examples 4 to 6
A nonaqueous electrolyte battery was produced in the same manner as in Example 15 except that the separator was changed to those in Examples 2 to 14 or Comparative Examples 1 to 3.

  The non-aqueous electrolyte batteries of Examples 15 to 28 and Comparative Examples 4 to 6 were subjected to the following charge / discharge efficiency evaluation, load characteristic evaluation, and short circuit resistance evaluation. The results are shown in Table 3.

<Charge / discharge efficiency>
About the nonaqueous electrolyte batteries of Examples 15 to 28 and Comparative Examples 4 to 6, constant current charging at 0.2 C (up to 4.2 V) and charging by constant voltage charging at 4.2 V (constant current charging and constant voltage) After a total charge time of 15 hours, the battery was discharged at 0.2 C up to 3.0 V, and charge / discharge efficiency (percentage of discharge capacity with respect to charge capacity) was determined. In addition, charging / discharging efficiency was calculated | required as an average value of 10 batteries, respectively.

<Load characteristics>
After constant current charging at 0.2C (up to 4.2V) and constant voltage charging at 4.2V (total time of constant current charging and constant voltage charging for 15 hours), up to 3.0V at a predetermined current value Discharge was performed, and the load capacity of the battery was evaluated by expressing the discharge capacity divided by the discharge capacity at 0.2 C discharge obtained at the time of charge / discharge efficiency evaluation as a percentage. In addition, the electric current value at the time of discharge was set to 1C and 2C.

  Table 3 shows the following. In the nonaqueous electrolyte batteries of Examples 15 to 28, all of the load characteristics had a discharge capacity at 2C as high as 85 to 92% of the discharge capacity at 0.2C, and these nonaqueous electrolyte batteries had The used separators (separators of Examples 1 to 14) all have a short-circuit current exceeding 60 mA, and it was confirmed that they have high short-circuit resistance.

  In addition, in the separator of Examples 1-14, as above-mentioned, although a short circuit current exceeds 60 mA, from these results, the nonaqueous electrolyte battery using the separator of Examples 1-14 (for example, Example 15) In the case of a non-aqueous electrolyte battery of ~ 28), it is estimated that no short circuit occurs even if charging is performed at a current value of 10C.

  In addition, the nonaqueous electrolyte batteries of Examples 15 to 28 have a spirally wound electrode body in which the positive electrode, the negative electrode, and the separator are overlapped, wound in a spiral shape, and further flattened. In the non-aqueous electrolyte batteries of 15 to 28, charge / discharge efficiency and load characteristics can be evaluated satisfactorily, and even a wound electrode body having the above-described form does not cause a short circuit due to a separator defect. Therefore, it can be seen that the separator of the present invention can ensure excellent reliability even when used in a battery having a wound electrode body (particularly a flat wound electrode body).

  On the other hand, in the nonaqueous electrolyte batteries of Comparative Examples 4 to 6, the discharge capacity at 2C was 87 to 91% of the discharge capacity at 0.2C and the load characteristics were good, but the separator used for these batteries (The separator of Comparative Examples 1 to 3) has a short circuit current as low as 18 to 30 mA, and the battery having such a separator is also inferior in short circuit resistance compared to the batteries of Examples 1 to 14; The characteristics and short circuit resistance are not well balanced.

Claims (7)

Comprising a porous film having a fibrous material that does not substantially deform at least at 150 ° C. and inorganic fine particles that do not substantially deform at least at 150 ° C .;
The ratio of the inorganic fine particles is 33.1% by volume or more,
And have you in the total number of the inorganic fine particles, and the particle size 0.3μm or less of the number of particles of 10% or more, a battery separator, wherein the number of particle size 1μm or more of the particles is not less than 15% .   The battery separator according to claim 1, wherein the inorganic fine particles are silica, boehmite, or alumina.   The battery separator according to claim 1 or 2, wherein a part or all of the inorganic fine particles are present in the voids of the sheet-like material composed of the fibrous material.   The battery separator according to claim 3, wherein the sheet-like material composed of the fibrous material is a woven fabric or a non-woven fabric.   The battery separator according to any one of claims 1 to 4, further comprising particles that melt at 80 to 130 ° C.   A nonaqueous electrolyte battery comprising a positive electrode, a negative electrode, a nonaqueous electrolyte, and the battery separator according to claim 1. The nonaqueous electrolyte battery according to claim 6, wherein the battery separator is integrated with at least one of the positive electrode and the negative electrode.