JP2010113804A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery capable of further suppressing capacity depression with repeating charge and discharge. <P>SOLUTION: The nonaqueous electrolyte secondary battery includes a cathode, an anode, a separator arranged between the cathode and the anode and including a heat-resistant material, and nonaqueous electrolyte, with a quantity (a volume) of the nonaqueous electrolyte of 0.9 times or more and 1.6 times or less to a total volume of voids of the cathode, the anode and the separator. In the nonaqueous secondary battery, the separator is composed of laminated films of a heat-resistant porous layer and a porous film. The cathode includes a cathode active material capable of doping and dedoping lithium ions applied at least on one side surface of a cathode current collector sheet, and the anode includes an anode active material capable of doping and dedoping lithium ions applied on at least one side surface of an anode current collecting sheet. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  The non-aqueous electrolyte secondary battery is a secondary battery including a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, and as a non-aqueous electrolyte secondary battery A typical lithium secondary battery has already been put into practical use as a power source for a mobile phone, a notebook personal computer, and the like, and has also been tried to be applied to medium and large applications such as automobile use and power storage use.

  As conventional non-aqueous electrolyte secondary batteries, for example, Patent Documents 1 and 2 describe non-aqueous electrolyte secondary batteries using a polyethylene microporous membrane separator.

JP 2002-270225 A JP 2000-294294 A

  However, the non-aqueous electrolyte secondary battery described above still has room for improvement in terms of capacity reduction upon repeated charge / discharge, that is, in terms of cycle characteristics. The objective of this invention is providing the non-aqueous-electrolyte secondary battery which can suppress the capacity | capacitance reduction at the time of repeating charging / discharging more, and is excellent in cycling property.

The inventors of the present invention have intensively studied to solve the above-mentioned problems and have arrived at the present invention. That is, the present invention provides the following inventions.
<1> A positive electrode, a negative electrode, a separator that is disposed between the positive electrode and the negative electrode, contains a heat-resistant material, and a non-aqueous electrolyte solution. A non-aqueous electrolyte secondary battery characterized by being 0.9 to 1.6 times the total volume of voids in the separator.
<2> The positive electrode is a positive electrode in which a positive electrode active material that can be doped / dedoped with lithium ions is applied to at least one surface of a positive electrode current collector sheet, and the negative electrode is doped / dedoped with lithium ions. The nonaqueous electrolyte secondary battery according to <1>, wherein the negative electrode active material that can be doped is a negative electrode that is applied to at least one surface of a negative electrode current collector sheet.
<3> The nonaqueous electrolysis according to <1> or <2>, wherein the separator containing the heat resistant material is a separator formed of a laminated film in which a heat resistant porous layer and a porous film are laminated. Liquid secondary battery.
<4> The nonaqueous electrolyte secondary battery according to <2> or <3>, wherein the heat resistant porous layer is a heat resistant porous layer containing a heat resistant resin.
<5> The nonaqueous electrolyte secondary battery according to <4>, wherein the heat-resistant resin is a nitrogen-containing aromatic polymer.
<6> The nonaqueous electrolyte secondary battery according to <4> or <5>, wherein the heat-resistant resin is an aromatic polyamide.
<7> The nonaqueous electrolyte secondary battery according to any one of <4> to <6>, wherein the heat-resistant porous layer contains a filler.
<8> The nonaqueous electrolyte secondary battery according to <7>, wherein the weight of the filler is 20 or more and 95 or less when the total weight of the heat resistant porous layer is 100.
<9> The heat-resistant porous layer contains two or more fillers, and the first largest value is D among the values obtained by measuring the average particle diameter of the particles constituting each of the two or more fillers. _1. The nonaqueous electrolyte secondary battery according to <7> or <8>, wherein the value of D ₂ / D ₁ is 0.15 or less, where D ₂ is the second largest value.
<10> The nonaqueous electrolyte secondary battery according to any one of <3> to <9>, wherein the heat-resistant porous layer has a thickness of 1 μm to 10 μm.
<11> The nonaqueous electrolyte secondary battery according to any one of <3> to <10>, wherein the porous film is a porous film containing a polyolefin resin.

  According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery that can further suppress a decrease in capacity when charging and discharging are repeated, that is, has excellent cycle characteristics, and the secondary battery of the present invention is In addition, it is extremely useful industrially because it can provide a secondary battery that is extremely excellent in heat resistance and excellent in cycle performance even under high-rate conditions.

  The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, containing a heat-resistant material, and a non-aqueous electrolyte. (Volume) is 0.9 to 1.6 times the total volume of voids in the positive electrode, the negative electrode, and the separator. In the present invention, the total volume of voids in the positive electrode, the negative electrode, and the separator is the sum of the volume of voids in the positive electrode, the volume of voids in the negative electrode, and the volume of voids in the separator.

  In the present invention, the separator containing a heat resistant material is preferably a separator made of a laminated film in which a heat resistant porous layer and a porous film are laminated.

  In the present invention, the volume of the voids in the positive electrode can be determined from the apparent volume of the positive electrode and the weight and true specific gravity of each member constituting the positive electrode. Examples of the member constituting the positive electrode include a positive electrode active material, a conductive agent, a positive electrode binder, and a positive electrode current collector sheet. For example, in this case, as shown in the following formula (1), voids in the positive electrode Can be obtained.

Volume of void in positive electrode = apparent volume of positive electrode − {(weight of positive electrode active material / true specific gravity of positive electrode active material) + (weight of conductive agent / true specific gravity of conductive agent) + (weight of positive electrode binder / positive electrode binder) True specific gravity) + (weight of positive electrode current collector sheet / true specific gravity of positive electrode current collector sheet)} (1)

  In the present invention, the volume of voids in the negative electrode can be determined from the apparent volume of the negative electrode and the weight and true specific gravity of each member constituting the negative electrode. Examples of the member constituting the negative electrode include a negative electrode active material, a conductive agent, a negative electrode binder, and a negative electrode current collector sheet. For example, in this case, the void in the negative electrode is represented by the following formula (2). Can be obtained.

Volume of void in negative electrode = apparent volume of negative electrode − {(weight of negative electrode active material / true specific gravity of negative electrode active material) + (weight of conductive agent / true specific gravity of conductive agent) + (weight of negative electrode binder / negative electrode binder) True specific gravity) + (weight of negative electrode current collector sheet / true specific gravity of negative electrode current collector sheet)} (2)

  In the present invention, the void volume in the separator can be determined from the apparent volume of the separator and the weight and true specific gravity of each member constituting the separator. For example, in the present invention, when the separator is composed of a laminated film in which a heat-resistant porous layer and a porous film are laminated, the apparent volume of the laminated film, the respective weights of the heat-resistant porous layer and the porous film, and From the true specific gravity, the volume of the voids in the separator can be obtained by the following equation (3).

Volume of voids in separator (laminated film) = apparent volume of laminated film − {(weight of heat resistant porous layer / true specific gravity of heat resistant porous layer) + (weight of porous film / true specific gravity of porous film)}. (3)

For example, when the heat resistant porous layer in the laminated film is composed of a heat resistant resin and a filler, (weight of heat resistant porous layer / true specific gravity of heat resistant porous layer) in formula (3) can be obtained as follows. .
(Weight of heat resistant porous layer / true specific gravity of heat resistant porous layer) = (weight of heat resistant resin / true specific gravity of heat resistant resin) + (weight of filler / true specific gravity of filler)

  In the nonaqueous electrolyte secondary battery of the present invention, the amount (volume) of the nonaqueous electrolyte is 0.9 to 1.6 times, preferably 1.1 times the total volume of voids in the positive electrode, the negative electrode, and the separator. From the viewpoint of further improving the cycle performance of the secondary battery under high-rate conditions, it is preferably 1.3 times or more and 1.6 times or less, more preferably 1.48 times or more and 1.59. The even more preferable range is 1.51 times or more and 1.57 times or less. In the present invention, compared with the conventional non-aqueous electrolyte secondary battery, the cycle performance is excellent, and the electrolyte solution can be obtained without increasing the amount of the electrolyte solution or adding an additive for improving the cycle performance. Since depletion and the like can be suppressed, a non-aqueous electrolyte secondary battery excellent in cycle performance and inexpensive can be provided. Moreover, in the non-aqueous electrolyte secondary battery of the present invention, when charging and discharging are repeated, it is possible to suppress a rapid decrease in the discharge capacity of the battery when a certain cycle is exceeded.

  Next, the nonaqueous electrolyte secondary battery of the present invention will be described in more detail. The non-aqueous electrolyte secondary battery of the present invention is obtained by laminating the above-mentioned positive electrode, separator and negative electrode in this order and winding them as necessary, and this electrode group is placed in a battery case such as a battery can. It can be manufactured by storing and impregnating the electrode group with a non-aqueous electrolyte. Examples of the shape of the electrode group include a shape in which a cross section when the electrode group is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, a rectangle with rounded corners, or the like. it can. In addition, examples of the shape of the secondary battery include a paper shape, a coin shape, a cylindrical shape, and a square shape. The volume of the battery case is usually 1.1 times or more and 1.5 times or less with respect to the total apparent volume of the positive electrode, the separator, and the negative electrode, and is preferably 1 in order to further enhance the effect of the present invention. .2 times or more and 1.4 times or less.

  In the present invention, the separator is porous and may contain a heat resistant material. Examples of the heat resistant material include inorganic powder and heat resistant resin described later. As a separator containing a heat-resistant material, for example, a separator made of a heat-resistant resin and / or inorganic powder can be cited, and the heat-resistant resin and / or inorganic powder is thermoplastic such as a polyolefin resin or a thermoplastic polyurethane resin. The thing disperse | distributed to the resin film can also be mentioned. Hereinafter, the separator which consists of a laminated | multilayer film with which the heat resistant porous layer and porous film which are preferable embodiments were laminated | stacked is demonstrated. In the laminated film, the heat resistant porous layer is a layer having higher heat resistance than the porous film, and the heat resistant porous layer may be formed of an inorganic powder or may contain a heat resistant resin. When the heat resistant porous layer contains a heat resistant resin, the heat resistant porous layer can be formed by an easy method such as coating. Examples of the heat resistant resin include polyamide, polyimide, polyamideimide, polycarbonate, polyacetal, polysulfone, polyphenylene sulfide, polyether ketone, aromatic polyester, polyether sulfone, and polyetherimide. Preferred heat resistant resins are polyamide, Polyimide, polyamideimide, polyethersulfone, and polyetherimide are preferable, and polyamide, polyimide, and polyamideimide are more preferable heat resistant resins. Even more preferred heat resistant resins are nitrogen-containing aromatic polymers such as aromatic polyamides (para-oriented aromatic polyamides, meta-oriented aromatic polyamides), aromatic polyimides, aromatic polyamideimides, and particularly preferred heat resistant resins are aromatic. From the viewpoint of being a polyamide and easily usable, a particularly preferred heat resistant resin is a para-oriented aromatic polyamide (hereinafter sometimes referred to as “para-aramid”). Further, examples of the heat resistant resin include poly-4-methylpentene-1 and cyclic olefin polymers. By using these heat resistant resins, the heat resistance of the laminated film, that is, the thermal film breaking temperature of the laminated film is further increased. Among these heat-resistant resins, when using a nitrogen-containing aromatic polymer, because of the polarity in the molecule, compatibility with the electrolyte, that is, the liquid retention in the heat-resistant porous layer may be improved, The rate of impregnation of the electrolyte during production of the non-aqueous electrolyte secondary battery is also high, and the charge / discharge capacity of the non-aqueous electrolyte secondary battery is further increased.

  The thermal film breaking temperature of such a laminated film depends on the type of heat-resistant resin, and is selected and used according to the use scene and purpose of use. More specifically, as the heat resistant resin, the cyclic olefin polymer is used at about 400 ° C. when the nitrogen-containing aromatic polymer is used, and at about 250 ° C. when poly-4-methylpentene-1 is used. When using, the thermal film breaking temperature can be controlled to about 300 ° C., respectively. Moreover, when the heat resistant porous layer is made of an inorganic powder, the thermal film breaking temperature can be controlled to, for example, 500 ° C. or higher.

  The para-aramid is obtained by condensation polymerization of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide, and the amide bond is in the para position of the aromatic ring or an oriented position equivalent thereto (for example, 4,4′- It consists essentially of repeating units bonded at opposite orientations, such as biphenylene, 1,5-naphthalene, 2,6-naphthalene, etc., oriented in the opposite direction coaxially or in parallel. Specifically, poly (paraphenylene terephthalamide), poly (parabenzamide), poly (4,4′-benzanilide terephthalamide), poly (paraphenylene-4,4′-biphenylenedicarboxylic acid amide), poly ( Para-aligned or para-oriented such as paraphenylene-2,6-naphthalenedicarboxylic acid amide), poly (2-chloro-paraphenylene terephthalamide), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer Examples include para-aramid having a structure according to the type.

  The aromatic polyimide is preferably a wholly aromatic polyimide produced by condensation polymerization of an aromatic dianhydride and a diamine. Specific examples of the dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic Examples thereof include acid dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and the like. Specific examples of the diamine include oxydianiline, paraphenylenediamine, benzophenonediamine, 3,3′-methylenedianiline, 3,3′-diaminobenzophenone, 3,3′-diaminodiphenylsulfone, 1,5 '-Naphthalenediamine and the like. Moreover, a polyimide soluble in a solvent can be preferably used. An example of such a polyimide is a polycondensate polyimide of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and an aromatic diamine.

  As the above-mentioned aromatic polyamideimide, those obtained from condensation polymerization using aromatic dicarboxylic acid and aromatic diisocyanate, those obtained from condensation polymerization using aromatic diacid anhydride and aromatic diisocyanate Is mentioned. Specific examples of the aromatic dicarboxylic acid include isophthalic acid and terephthalic acid. Specific examples of the aromatic dianhydride include trimellitic anhydride. Specific examples of the aromatic diisocyanate include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, orthotolylane diisocyanate, m-xylene diisocyanate, and the like.

  In order to further enhance the ion permeability, the heat-resistant porous layer is preferably a thin heat-resistant porous layer having a thickness of 1 μm to 10 μm, more preferably 1 μm to 5 μm, particularly 1 μm to 4 μm. The heat-resistant porous layer has fine pores, and the size (diameter) of the pores is usually 3 μm or less, preferably 1 μm or less.

  In addition, when the heat resistant porous layer contains a heat resistant resin, it can further contain a filler. The filler may be selected from organic powder, inorganic powder, or a mixture thereof as the material thereof. The particles constituting the filler preferably have an average particle size of 0.01 μm or more and 1 μm or less.

  Examples of the organic powder include styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, and methyl acrylate, or a copolymer of two or more kinds, polytetrafluoroethylene, 4 fluorine. Examples include fluorine-containing resins such as fluorinated ethylene-6-propylene-propylene copolymer, tetrafluoroethylene-ethylene copolymer, and polyvinylidene fluoride; melamine resin; urea resin; polyolefin; and powders made of organic substances such as polymethacrylate. . The organic powder may be used alone or in combination of two or more. Among these organic powders, polytetrafluoroethylene powder is preferable from the viewpoint of chemical stability.

  Examples of the inorganic powder include powders made of inorganic substances such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates, sulfates, etc. Among these, they are made of inorganic substances having low conductivity. Powder is preferably used. Specific examples include powders made of alumina, silica, titanium dioxide, calcium carbonate, or the like. The inorganic powder may be used alone or in combination of two or more. Among these inorganic powders, alumina powder is preferable from the viewpoint of chemical stability. Here, it is more preferable that all of the particles constituting the filler are alumina particles, and it is even more preferable that all of the particles constituting the filler are alumina particles, and part or all of them are substantially spherical alumina particles. It is embodiment which is. Incidentally, when the heat-resistant porous layer is formed from an inorganic powder, the inorganic powder exemplified above may be used, and may be mixed with a binder as necessary.

  When the heat-resistant porous layer contains a heat-resistant resin, the filler content depends on the specific gravity of the filler material. For example, when the total weight of the heat-resistant porous layer is 100, the filler weight is usually 5 It is 95 or more and it is preferable that it is 20 or more and 95 or less, More preferably, it is 30 or more and 90 or less. These ranges are particularly suitable when all of the particles constituting the filler are alumina particles.

  Examples of the shape of the filler include a substantially spherical shape, a plate shape, a columnar shape, a needle shape, a whisker shape, and a fibrous shape, and any particle can be used. It is preferable that Examples of the substantially spherical particles include particles having a particle aspect ratio (particle major axis / particle minor axis) in the range of 1 to 1.5. The aspect ratio of the particles can be measured by an electron micrograph.

Moreover, the heat resistant porous layer can also contain two or more kinds of fillers. In this case, when the average value of the particles constituting each of the two or more fillers is measured, the first largest value is D ₁ , and the second largest value is D ₂ . it is preferable the value of D ₂ / D ₁ is 0.15 or less. As a result, in the micropores of the heat-resistant porous layer of the laminated film, micropores having a relatively small size and micropores having a relatively large size are generated in a well-balanced manner. The heat resistance of the separator made of a film can be further increased, and the structure of the micropores having a relatively large size increases the lithium ion permeability. In the obtained non-aqueous electrolyte secondary battery, it is higher at a high current rate. It is possible to obtain an output, that is, it is excellent and suitable for high rate characteristics. In the above, the average particle diameter may be a value measured from an electron micrograph. That is, the particles (filler particles) photographed on the scanning electron micrograph of the surface or cross section of the heat-resistant porous layer in the laminated porous film are classified by size, and among the average particle diameter values in each classification, 1 When the first largest value is D ₁ and the second largest value is D ₂ , the value of D ₂ / D ₁ may be 0.15 or less. For the average particle size, 25 particles are arbitrarily extracted in each of the above classifications, the particle size (diameter) is measured for each, and the average value of the 25 particle sizes is defined as the average particle size. In addition, the particle | grains which comprise said filler mean the primary particle | grains which comprise a filler.

  In the laminated film, the porous film preferably has fine pores and usually has a shutdown function. The size (diameter) of the micropores in the porous film is usually 3 μm or less, preferably 1 μm or less. The porosity of the porous film is usually 30 to 80% by volume, preferably 40 to 70% by volume. In the non-aqueous electrolyte secondary battery, when the normal use temperature is exceeded, the micropores can be closed by the deformation and softening of the porous film by the shutdown function.

  In the laminated film, the resin constituting the porous film may be selected from those that do not dissolve in the electrolyte solution in the nonaqueous electrolyte secondary battery. Specific examples include polyolefin resins such as polyethylene and polypropylene, and thermoplastic polyurethane resins, and a mixture of two or more of these may be used. In terms of softening and shutting down at a lower temperature, the porous film preferably contains a polyolefin resin, and more preferably contains polyethylene. Specific examples of polyethylene include polyethylene such as low density polyethylene, high density polyethylene, and linear polyethylene, and also include ultrahigh molecular weight polyethylene. In the sense of further increasing the puncture strength of the porous film, the resin constituting it preferably contains at least ultra high molecular weight polyethylene. Moreover, it may be preferable to contain the wax which consists of polyolefin of a low molecular weight (weight average molecular weight 10,000 or less) in the manufacture surface of a porous film.

  Moreover, the thickness of the porous film in a laminated | multilayer film is 3-30 micrometers normally, Preferably it is 3-25 micrometers. Moreover, as thickness of a laminated film, it is 40 micrometers or less normally, Preferably, it is 20 micrometers or less. Moreover, when the thickness of the heat resistant porous layer is A (μm) and the thickness of the porous film is B (μm), the value of A / B is preferably 0.1 or more and 1 or less.

Next, an example of manufacturing a laminated film will be described.
First, the manufacturing method of a porous film is demonstrated. The production of the porous film is not particularly limited. For example, as described in JP-A-7-29563, a plasticizer is added to a thermoplastic resin to form a film, and then the plasticizer is mixed with an appropriate solvent. As described in JP-A-7-304110, a film made of a thermoplastic resin produced by a known method is used, and a structurally weak amorphous portion of the film is selectively stretched. And a method of forming micropores. For example, when the porous film is formed from a polyolefin resin containing ultrahigh molecular weight polyethylene and a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, it is produced by the following method from the viewpoint of production cost. It is preferable. That is,
(1) A step of kneading 100 parts by weight of ultrahigh molecular weight polyethylene, 5 to 200 parts by weight of a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and 100 to 400 parts by weight of an inorganic filler to obtain a polyolefin resin composition ( 2) Step of forming a sheet using the polyolefin resin composition (3) Step of removing inorganic filler from the sheet obtained in step (2) (4) Stretching of the sheet obtained in step (3) Or a method comprising a step of obtaining a porous film, or (1) 100 parts by weight of ultrahigh molecular weight polyethylene, 5 to 200 parts by weight of a low molecular weight polyolefin having a weight average molecular weight of 10,000 or less, and 100 to 400 parts by weight of an inorganic filler And a step of obtaining a polyolefin resin composition by kneading (2) a step of molding a sheet using the polyolefin resin composition (3) obtained in step (2) From in stretched sheet obtained in the step of stretching the sheet (4) Step (3), the method comprising the step of removing the inorganic filler to obtain a porous film.

  From the viewpoint of the strength and ion permeability of the porous film, the inorganic filler used preferably has an average particle diameter (diameter) of 0.5 μm or less, more preferably 0.2 μm or less. Here, the value measured from an electron micrograph is used for the average particle diameter. Specifically, 50 particles are arbitrarily extracted from the inorganic filler particles photographed in the photograph, the particle diameter is measured, and the average value is used.

  Inorganic fillers include calcium carbonate, magnesium carbonate, barium carbonate, zinc oxide, calcium oxide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium sulfate, silicic acid, zinc oxide, calcium chloride, sodium chloride, magnesium sulfate, etc. Is mentioned. These inorganic fillers can be removed from the sheet or film with an acid or alkaline solution. Calcium carbonate is preferably used from the viewpoints of particle size controllability and selective solubility in acid.

  The method for producing the polyolefin resin composition is not particularly limited, but a mixing device, such as a roll, a Banbury mixer, a single screw extruder, a twin screw extruder, or the like, is used to mix materials constituting the polyolefin resin composition such as polyolefin resin and inorganic filler. And mixed to obtain a polyolefin resin composition. When mixing the materials, additives such as fatty acid esters, stabilizers, antioxidants, ultraviolet absorbers and flame retardants may be added as necessary.

  The manufacturing method of the sheet | seat which consists of the said polyolefin resin composition is not specifically limited, It can manufacture by sheet | seat shaping | molding methods, such as an inflation process, a calendar process, T-die extrusion process, and a Skyf method. Since a sheet with higher film thickness accuracy can be obtained, it is preferable to produce the sheet by the following method.

  A preferred method for producing a sheet comprising a polyolefin resin composition is a method of rolling a polyolefin resin composition using a pair of rotational molding tools adjusted to a surface temperature higher than the melting point of the polyolefin resin contained in the polyolefin resin composition. It is a method to do. The surface temperature of the rotary forming tool is preferably (melting point + 5) ° C. or higher. The upper limit of the surface temperature is preferably (melting point + 30) ° C. or less, and more preferably (melting point + 20) ° C. or less. Examples of the pair of rotary forming tools include a roll and a belt. The peripheral speeds of the two rotary forming tools do not necessarily have to be exactly the same peripheral speed, and the difference between them may be about ± 5% or less. By producing a porous film using a sheet obtained by such a method, a porous film excellent in strength, ion permeation, air permeability and the like can be obtained. Moreover, you may use what laminated | stacked the sheet | seat of the single layer obtained by the above methods for manufacture of a porous film.

  When the polyolefin resin composition is roll-formed with a pair of rotary molding tools, the polyolefin resin composition discharged in a strand form from an extruder may be directly introduced between the pair of rotary molding tools, and once pelletized polyolefin A resin composition may be used.

  When stretching a sheet made of a polyolefin resin composition or a sheet from which the inorganic filler has been removed, a tenter, a roll, an autograph or the like can be used. From the air permeable side, the draw ratio is preferably 2 to 12 times, more preferably 4 to 10 times. The stretching temperature is usually carried out at a temperature not lower than the softening point of the polyolefin resin and not higher than the melting point, preferably 80 to 115 ° C. If the stretching temperature is too low, film breakage tends to occur during stretching, and if it is too high, the air permeability and ion permeability of the resulting porous film may be lowered. Moreover, it is preferable to heat set after extending | stretching. The heat set temperature is preferably a temperature below the melting point of the polyolefin resin.

  In the present invention, a porous film containing a thermoplastic resin obtained by the method as described above and a heat-resistant porous layer are laminated to obtain a laminated film. The heat resistant porous layer may be provided on one side of the porous film or may be provided on both sides.

As a method of laminating a porous film and a heat-resistant porous layer, a method of separately producing a heat-resistant porous layer and a porous film and laminating each of them, and containing a heat-resistant resin and a filler on at least one surface of the porous film In the present invention, when the heat resistant porous layer is relatively thin, the latter method is preferable from the viewpoint of productivity. Specific examples of a method for forming a heat resistant resin layer by applying a coating solution containing a heat resistant resin and a filler to at least one surface of the porous film include the following steps.
(A) In a polar organic solvent solution containing 100 parts by weight of a heat resistant resin, a slurry-like coating liquid is prepared by dispersing 1 to 1500 parts by weight of a filler with respect to 100 parts by weight of the heat resistant resin.
(B) The coating solution is applied to at least one surface of the porous film to form a coating film.
(C) The heat-resistant resin is deposited from the coating film by means such as humidification, solvent removal, or immersion in a solvent that does not dissolve the heat-resistant resin, and then dried as necessary.
The coating solution is preferably applied continuously by a coating apparatus described in JP-A-2001-316006 and a method described in JP-A-2001-23602.

  When the heat resistant resin is para-aramid in the polar organic solvent solution, a polar amide solvent or a polar urea solvent can be used as the polar organic solvent. Specifically, N, N— Examples include, but are not limited to, dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), and tetramethylurea.

  When para-aramid is used as the heat-resistant resin, it is preferable to add an alkali metal or alkaline earth metal chloride during para-aramid polymerization for the purpose of improving the solubility of para-aramid in a solvent. Specific examples include lithium chloride or calcium chloride, but are not limited thereto. The amount of the chloride added to the polymerization system is preferably in the range of 0.5 to 6.0 mol, more preferably in the range of 1.0 to 4.0 mol, per 1.0 mol of the amide group produced by condensation polymerization. . If the chloride is less than 0.5 mol, the solubility of the resulting para-aramid may be insufficient, and if it exceeds 6.0 mol, the solubility of the chloride in the solvent may be substantially exceeded, which may be undesirable. . In general, if the alkali metal or alkaline earth metal chloride is less than 2% by weight, the solubility of para-aramid may be insufficient. If it exceeds 10% by weight, the alkali metal or alkaline earth metal chloride may be insufficient. May not dissolve in polar organic solvents such as polar amide solvents or polar urea solvents.

  Further, when the heat resistant resin is an aromatic polyimide, the polar organic solvent for dissolving the aromatic polyimide includes those exemplified as the solvent for dissolving the aramid, dimethyl sulfoxide, cresol, o-chlorophenol, etc. Can be suitably used.

  As a method for obtaining a slurry-like coating liquid by dispersing a filler, a pressure disperser (gorin homogenizer, nanomizer) or the like may be used as the apparatus.

  Examples of the method of applying the slurry-like coating liquid include coating methods such as knives, blades, bars, gravure and dies, and coating methods such as bars and knives are simple, but industrially, the solution Is preferably a die coating method having a structure that does not come into contact with the outside air. Moreover, application | coating may be performed twice or more. In this case, it is usual to carry out after depositing the heat-resistant resin in the step (c).

  In the case where the heat resistant porous layer and the porous film are separately manufactured and laminated, it is preferable to fix them by a method using an adhesive, a method using heat fusion, or the like.

  In addition, the positive electrode in the present invention is preferably a positive electrode in which a positive electrode active material capable of doping and dedoping lithium ions is applied to at least one surface of a positive electrode current collector sheet. Such a positive electrode can be manufactured by, for example, applying and drying a positive electrode mixture containing a positive electrode active material, a conductive agent, a positive electrode binder and a solvent on a positive electrode current collector sheet and removing the solvent. it can. In addition, as a method for producing a positive electrode, a sheet obtained by adding a solvent to a positive electrode active material, a positive electrode binder, a conductive agent, and the like, kneading, molding, and drying is added to the positive electrode current collector sheet. After joining via an adhesive or the like, pressing and heat treatment drying, or after forming a mixture comprising a positive electrode active material, a positive electrode binder, a conductive agent and a liquid lubricant on the positive electrode current collector sheet, the liquid lubricant Examples of the method include removing the film and then stretching the obtained sheet-like molded product in a uniaxial or multiaxial direction. The thickness of the positive electrode is usually about 5 to 500 μm.

Examples of the positive electrode active material that can be doped / dedoped with lithium ions include known materials, specifically, at least one selected from V, Mn, Fe, Co, Ni, Cr, and Ti. Examples include lithium composite metal oxides containing various transition metal elements, preferably lithium composite metal oxides having an α-NaFeO ₂ type structure, and more preferably cobalt acid in that the average discharge potential is high. Examples thereof include lithium, lithium nickelate, and lithium composite metal oxides in which part of nickel in lithium nickelate is replaced with other elements such as Mn and Co. In addition, a lithium composite metal oxide having a spinel structure such as lithium manganese spinel can be given.

  Examples of the conductive agent used for the positive electrode include carbon materials such as natural graphite, artificial graphite, cokes, and carbon black.

  As said positive electrode binder, the polymer of a fluorine compound is mentioned, for example. Examples of the fluorine compound include fluorinated alkyl (C1-18) (meth) acrylate, perfluoroalkyl (meth) acrylate [for example, perfluorododecyl (meth) acrylate, perfluoro n-octyl (meth) acrylate, Perfluoro n-butyl (meth) acrylate], perfluoroalkyl-substituted alkyl (meth) acrylate [for example, perfluorohexylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate], perfluorooxyalkyl (meth) acrylate [ For example, perfluorododecyloxyethyl (meth) acrylate and perfluorodecyloxyethyl (meth) acrylate, etc.], fluorinated alkyl (C1-C18) crotonate, fluorinated alkyl (carbon Number 1-18) Malate and fumarate, fluorinated alkyl (carbon number 1-18) itaconate, fluorinated alkyl-substituted olefin (about 2-10 carbon atoms, about 1-17 fluorine atoms) such as perfluorohexylethylene, carbon Examples thereof include fluorinated olefins, tetrafluoroethylene, trifluoroethylene, vinylidene fluoride, hexafluoropropylene and the like in which fluorine atoms are bonded to double bond carbons of about 2 to 10 and about 1 to 20 fluorine atoms.

Moreover, as a positive electrode binder, the addition polymer of the monomer containing the ethylenic double bond which does not contain a fluorine atom can also be mentioned. Examples of such monomers include (cyclo) alkyl (C1-22) (meth) acrylate [for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (Meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, octadecyl (meth) acrylate, etc.]; aromatic ring-containing (meth) acrylate [for example, benzyl (Meth) acrylate, phenylethyl (meth) acrylate, etc.]; mono (meth) acrylate of alkylene glycol or dialkylene glycol (alkylene group having 2 to 4 carbon atoms) [for example, 2-hydroxyethyl (meth) acrylate, 2- Hi Roxypropyl (meth) acrylate, diethylene glycol mono (meth) acrylate]; (poly) glycerin (degree of polymerization 1 to 4) mono (meth) acrylate; polyfunctional (meth) acrylate [for example, (poly) ethylene glycol (degree of polymerization 1) ~ 100) di (meth) acrylate, (poly) propylene glycol (degree of polymerization 1-100) di (meth) acrylate, 2,2-bis (4-hydroxyethylphenyl) propane di (meth) acrylate, trimethylolpropane tri ( (Meth) acrylate monomers such as (meth) acrylate]; (meth) acrylamide (meth) acrylamide, (meth) acrylamide derivatives [eg, N-methylol (meth) acrylamide, diacetone acrylamide, etc.] Acrylamide monomer; ) Cyano group-containing monomers such as acrylonitrile, 2-cyanoethyl (meth) acrylate, 2-cyanoethylacrylamide; styrene and styrene derivatives having 7 to 18 carbon atoms [for example, α-methylstyrene, vinyltoluene, p-hydroxystyrene and Styrene monomers such as divinylbenzene] Diene monomers such as alkadienes having 4 to 12 carbon atoms [for example, butadiene, isoprene, chloroprene, etc.]; Carboxylic acid (2 to 12 carbon atoms) vinyl esters [for example, , Vinyl acetate, vinyl propionate, vinyl butyrate and vinyl octoate, etc.], carboxylic acid (2 to 12 carbon atoms) (meth) allyl ester [for example, (meth) allyl acetate, (meth) allyl propionate and octanoic acid ( Alkenyl ester monomers such as (meth) allyl etc.]; Epoxy group-containing monomers such as zir (meth) acrylate and (meth) allyl glycidyl ether; monoolefins having 2 to 12 carbon atoms [for example, ethylene, propylene, 1-butene, 1-octene and 1-dodecene, etc.] Monoolefins; chlorine, bromine or iodine atom-containing monomers, halogen atom-containing monomers other than fluorine such as vinyl chloride and vinylidene chloride; (meth) acrylic acid such as acrylic acid and methacrylic acid; butadiene, isoprene, etc. Examples thereof include a conjugated double bond-containing monomer.
The addition polymer may be a copolymer such as an ethylene / vinyl acetate copolymer, a styrene / butadiene copolymer, or an ethylene / propylene copolymer. The carboxylic acid vinyl ester polymer may be partially or completely saponified, such as polyvinyl alcohol. The positive electrode binder may be a copolymer of a fluorine compound and a monomer containing an ethylenic double bond not containing a fluorine atom.

  Further, as the positive electrode binder, for example, polysaccharides such as starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylhydroxyethylcellulose, nitrocellulose, and derivatives thereof; phenol resin; melamine resin; polyurethane resin; Resin; Polyamide resin; Polyimide resin; Polyamideimide resin; Petroleum pitch;

  Among these examples, the positive electrode binder is particularly preferably a polymer of a fluorine compound, and particularly preferably polytetrafluoroethylene which is a polymer of tetrafluoroethylene. Moreover, you may use multiple types of said thing as a positive electrode binder. Further, when the positive electrode mixture thickens, a plasticizer may be used to facilitate application to the positive electrode current collector sheet.

  Examples of the solvent used for the positive electrode include aprotic polar solvents such as N-methyl-2-pyrrolidone, alcohols such as isopropyl alcohol, ethyl alcohol or methyl alcohol, ethers such as propylene glycol dimethyl ether, acetone, and methyl ethyl ketone. Or ketones, such as methyl isobutyl ketone, are mentioned. Moreover, water can also be used as a solvent.

  The conductive adhesive may be a mixture of a conductive agent and a binder. In particular, if a mixture of carbon black and polyvinyl alcohol is used, it is not necessary to use a solvent, and preparation is easy. It may be excellent in preservability.

  Moreover, in the positive electrode mixture, the blending amount of the constituent material may be set as appropriate, but the blending amount of the positive electrode binder is usually about 0.5 to 30 parts by weight with respect to 100 parts by weight of the positive electrode active material, Preferably, it is about 2 to 30 parts by weight, and the blending amount of the conductive agent is usually about 1 to 50 parts by weight, preferably about 1 to 30 parts by weight with respect to 100 parts by weight of the positive electrode active material. As a compounding quantity, it is about 50-500 weight part normally with respect to 100 weight part of positive electrode active materials, Preferably it is about 100-200 weight part.

  Examples of the positive electrode current collector sheet include metals such as nickel, aluminum, titanium, copper, gold, silver, platinum, aluminum alloy, and stainless steel, such as carbon materials, activated carbon fibers, nickel, aluminum, zinc, copper, A conductive film in which a conductive agent is dispersed in a resin such as rubber or styrene-ethylene-butylene-styrene copolymer (SEBS) formed by plasma spraying or arc spraying of tin, lead or an alloy thereof. Etc. In particular, aluminum, nickel, stainless steel, and the like are preferable. In particular, aluminum is preferable because it can be easily processed into a thin film and is inexpensive. Examples of the shape of the positive electrode current collector sheet include a foil shape, a flat plate shape, a mesh shape, a net shape, a lath shape, a punching metal shape, an embossed shape, or a combination thereof (for example, a mesh flat plate). Etc. Moreover, you may form an unevenness | corrugation by performing an etching process etc. about the positive electrode collector sheet surface.

  In addition, the negative electrode in the present invention is preferably a negative electrode in which a negative electrode active material capable of doping and dedoping lithium ions is applied to at least one surface of a negative electrode current collector sheet. Such a negative electrode, for example, by applying and drying a negative electrode active material, a negative electrode binder, a solvent and, if necessary, a negative electrode mixture containing a conductive agent on a negative electrode current collector sheet and removing the solvent, Can be manufactured. In addition, as a method for producing a negative electrode, a negative electrode current collector is prepared by adding a solvent to a negative electrode active material, a negative electrode binder, and a conductive agent used as necessary, kneading, molding, and drying. A method of pressing and heat-treating after bonding to a body sheet via a conductive adhesive or the like, or a mixture comprising a negative electrode active material, a negative electrode binder, a liquid lubricant, and a conductive agent used as necessary, is used as a negative electrode current collector sheet Examples of the method include a method in which the liquid lubricant is removed after the molding, and then the obtained sheet-shaped molding is stretched in a uniaxial or multiaxial direction. The thickness of the negative electrode is usually about 5 to 500 μm.

  As the negative electrode active material that can be doped / dedoped with lithium ions, carbon materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds are used. be able to. A non-graphitizable carbon material can also be used. The shape of the carbon material may be any of a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder.

  Moreover, as a negative electrode active material that can be doped / undoped with lithium ions, other than the above carbon materials, for example, chalcogen compounds (oxides, sulfides, etc.), nitrides, metals or alloys, which are lower than the positive electrode Examples thereof include materials that can be doped / undoped with lithium ions at a potential.

As the oxide, specifically, an oxide of silicon represented by the formula SiO _x (where x is a positive real number) such as SiO ₂ and SiO, a formula TiO _x such as TiO ₂ and TiO (where x is x) Is a positive oxide of titanium, V ₂ O ₅ , VO _2, etc., and VO _x (where x is a positive real number), vanadium oxide, Fe ₃ O ₄ , Fe ₂ O ₃ , FeO and the like FeO _x (where x is a positive real number) Iron oxide, SnO ₂ , SnO and the like SnO _x (where x is a positive real number) Tin oxide, WO ₃ , WO _{2 and} other tungsten oxides represented by the general formula WO _x (where x is a positive real number), Li ₄ Ti ₅ O ₁₂ , LiVO ₂ (for example Li _1.1 V _0.9 O and the like containing mixed metal oxide for the ₂₎ and lithium such as titanium and / or vanadium Door can be. Specific examples of the sulfide include titanium sulfides represented by the formula TiS _x (where x is a positive real number) such as Ti ₂ S ₃ , TiS ₂ , and TiS, V ₃ S ₄ , VS _2, VS and other formulas VS _x (where x is a positive real number), vanadium sulfide, Fe ₃ S ₄ , FeS ₂ , FeS and other formulas FeS _x (where x is a positive real number) Iron sulfide, Mo ₂ S ₃ , MoS _{2 and the} like MoS _x (where x is a positive real number) molybdenum sulfide, SnS _2, SnS and other formula SnS _x (where x is Tin sulfide represented by positive real number), WS _{2 and} other formulas WS _x (where x is a positive real number), tungsten sulfide represented by SbS _x such as Sb ₂ S ₃ (where, x is antimony represented by a positive real _{number), Se 5 S 3, SeS} 2, SeS formula SeS _x (wherein such, Mention may be made of such sulfides selenium represented by a positive real number). Specific examples of the nitride include lithium-containing nitrides such as Li ₃ N, Li _3-x A _x N (where A is Ni and / or Co, and 0 <x <3). Can be mentioned. These negative electrode active materials may be used in combination, and may be crystalline or amorphous.

Specific examples of the metal include lithium metal, silicon metal, and tin metal. Examples of the alloy include lithium alloys such as Li—Al, Li—Ni, and Li—Si, silicon alloys such as Si—Zn, Sn—Mn, Sn—Co, Sn—Ni, Sn—Cu, and Sn—La. In addition to tin alloys such as Cu ₂ Sb, La ₃ Ni ₂ Sn _{7 and the} like can also be mentioned. These metals and alloys can be used alone as a negative electrode, for example, in the form of a foil.

  The negative electrode binder can be the same as the positive electrode binder. Moreover, the same thing as what is used with a positive electrode can also be used for the electrically conductive agent and solvent in a negative electrode, and a carbon material may play a role as a electrically conductive agent in a negative electrode.

  Examples of the negative electrode current collector sheet include copper, nickel, and stainless steel. Copper is preferred because it is difficult to form an alloy with lithium and it can be easily processed into a thin film. Examples of the shape of the negative electrode current collector sheet include a foil shape, a flat plate shape, a mesh shape, a net shape, a lath shape, a punching metal shape, an embossed shape, or a combination thereof (for example, a mesh flat plate). Etc. Moreover, you may form an unevenness | corrugation by performing an etching process etc. about the negative electrode collector sheet surface.

  Further, in the nonaqueous electrolyte secondary battery of the present invention, the positive electrode is a positive electrode formed by applying a positive electrode active material capable of doping and dedoping lithium ions to at least one surface of the positive electrode current collector sheet, and More preferably, the negative electrode is a negative electrode in which a negative electrode active material capable of doping and dedoping lithium ions is applied to at least one surface of a negative electrode current collector sheet.

In addition, the nonaqueous electrolytic solution in the present invention is usually obtained by dissolving an electrolyte in an organic solvent. Examples of the electrolyte include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LIBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (COCF ₃ ), Li (C ₄ F ₉ SO ₃ ), LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , LiBOB (where BOB is bis (oxalato) borate). ), Lithium salts such as lower aliphatic carboxylic acid lithium salts and LiAlCl ₄ , and two or more of these lithium salts may be used. Among these electrolytes, they were selected from the group consisting of LiPF ₆ containing fluorine, LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ and LiC (SO ₂ CF ₃ ) ₃ . It is preferable to use at least one electrolyte.

  Examples of the organic solvent in the non-aqueous electrolyte include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, isopropyl methyl carbonate, vinylene carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, Carbonates such as 1,2-di (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether , Ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; N Amides such as N-dimethylformamide and N, N-dimethylacetamide; Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propane sultone; What further introduce | transduced the fluorine substituent into the solvent can be used. Two or more of these may be mixed and used as the organic solvent.

  The concentration of the electrolyte in the nonaqueous electrolytic solution is usually about 0.1 mol / L to 2 mol / L, and preferably about 0.3 mol / L to 1.5 mol / L.

  Next, the present invention will be described in more detail using examples. The evaluation of the non-aqueous electrolyte secondary battery was based on the following test method.

<Test method for non-aqueous electrolyte secondary battery>
About the non-aqueous-electrolyte secondary battery, the cycle test was done using the charging / discharging conditions of the following (1), (2-1), (2-2).

(1) Initial charge / discharge The initial current value was 50 mA, the current value was increased stepwise by 50 mA every 30 minutes, charged to 4.2 V, and then discharged to 3 V.

(2-1) Cycle test charge / discharge condition 1
After the initial charge / discharge, the first cycle charge was performed under the condition of CC-CV (constant current constant voltage) at 1 A up to 4.2 V, and the discharge was CC discharged at 6.67 W and cut off at a voltage of 3 V. . The rest period between charging and discharging was 5 minutes, and charging / discharging after the next cycle was performed at the same speed as in the charging, and cut off at a charging voltage of 4.2 V and a discharging voltage of 3 V. This charging / discharging was repeated 500 times in a thermostat set to 20 ° C.

(2-2) Cycle test charge / discharge condition 2 (high rate condition)
After the initial charge / discharge, the first cycle charge was performed under the condition of CC-CV (constant current constant voltage) at 3C up to 4.2V, and the discharge was CC-discharged at 2C and cut off at a voltage of 3V. The rest period between charging and discharging was 5 minutes, and charging / discharging after the next cycle was performed at the same speed as in the charging, and cut off at a charging voltage of 4.2 V and a discharging voltage of 3 V. This charging / discharging was repeated 500 times in a thermostat set to 20 ° C.

Production Example 1 (Production of laminated film)
(1) Production of coating solution After 272.7 g of calcium chloride was dissolved in 4200 g of NMP, 132.9 g of paraphenylenediamine was added and completely dissolved. To the obtained solution, 243.3 g of terephthalic acid dichloride (hereinafter abbreviated as TPC) was gradually added and polymerized to obtain para-aramid, which was further diluted with NMP to obtain a para-aramid solution having a concentration of 2.0% by weight ( A) was obtained. To 100 g of the obtained para-aramid solution, 2 g of alumina powder (a) (manufactured by Nippon Aerosil Co., Ltd., Alumina C, average particle diameter 0.02 μm (corresponding to D ₂ ), particles are substantially spherical, and the aspect ratio of the particles is 1) Add 4 g of filler as a filler of 2 g of alumina powder (b) (Sumitomo Chemical Co., Ltd. Sumiko Random, AA03, average particle size 0.3 μm (corresponding to D ₁ ), particles are approximately spherical, and the aspect ratio of the particles is 1). Then, the mixture was treated three times with a nanomizer, further filtered through a 1000 mesh wire net, and degassed under reduced pressure to produce a slurry-like coating liquid (B). The weight of alumina powder (filler) with respect to the total weight of para-aramid and alumina powder is 67% by weight. Further, D ₂ / D ₁ is 0.07.

(2) Production and Evaluation of Laminated Film As the porous film, a polyethylene porous film (film thickness 12 μm, air permeability 140 seconds / 100 cc, average pore diameter 0.1 μm, porosity 50%) was used. The polyethylene porous film was fixed on a PET film having a thickness of 100 μm, and the slurry-like coating liquid (B) was applied onto the porous film by a bar coater manufactured by Tester Sangyo Co., Ltd. The coated porous film on the PET film is integrated into a poor solvent and immersed in water to precipitate a para-aramid porous film (heat resistant porous layer), and then the solvent is dried to form a heat resistant porous film. A laminated film 1 in which a layer and a porous film were laminated was obtained. In addition, about the obtained laminated | multilayer film, the width | variety was 60 mm. The thickness of the laminated film 1 was 16 μm, and the thickness of the para-aramid porous film (heat resistant porous layer) was 4 μm. The air permeability of the laminated film 1 was 180 seconds / 100 cc, and the porosity was 50%. When the cross section of the heat-resistant porous layer in the laminated film 1 was observed with a scanning electron microscope (SEM), a relatively small micropore of about 0.03 μm to 0.06 μm and a relatively large micropore of about 0.1 μm to 1 μm. It was found to have The laminated film was evaluated by the following method.

<Evaluation of laminated film>
(A) Thickness measurement The thickness of the laminated film and the thickness of the porous film were measured in accordance with JIS standards (K7130-1992). Moreover, as the thickness of the heat resistant porous layer, a value obtained by subtracting the thickness of the porous film from the thickness of the laminated film was used.
(B) Measurement of air permeability by Gurley method The air permeability of the laminated film was measured by a digital timer type Gurley type densometer manufactured by Yasuda Seiki Seisakusho Co., Ltd. based on JIS P8117.
(C) Porosity A sample of the obtained laminated film was cut into a 10 cm long square and the weight W (g) and thickness D (cm) were measured. Obtain the weight (Wi (g)) of each layer in the sample, and obtain the volume of each layer from Wi and the true specific gravity (true specific gravity i (g / cm ³ )) of the material of each layer, The porosity (volume%) was determined from the following formula.
Porosity (volume%) = 100 × {1− (W1 / true specific gravity 1 + W2 / true specific gravity 2 +. + Wn / true specific gravity n) / (10 × 10 × D)}

Production Example 2 (Production of positive electrode)
Using the following positive electrode active material, conductive agent, binder 1, binder 2 and water, positive electrode active material (Cellseed C-10N (manufactured by Nippon Chemical Industry Co., Ltd.), LiCoO ₂ , true specific gravity 4.8 g / cm ³ ): Conductive agent (acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.), true specific gravity 2.2 g / cm ³ ): binder 1 (PTFE31-JR (manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.), true specific gravity 2.2 g / cm ³ ): Composition in which the mixing ratio of binder 2 (Serogen 4H (Daiichi Kogyo Seiyaku Co., Ltd., true specific gravity 1.4 g / cm ³ )) is 92: 2.7: 4.55: 0.75 (weight ratio). A certain amount of water was put into a kneader to dissolve the binder 2, and then the positive electrode active material, the conductive agent and the binder 1 were added and kneaded so that the viscosity was 2700 ± 1000 cp. , A positive electrode mixture was obtained by adding water and applied to a predetermined portion of both surfaces of an Al foil having a thickness of 20 μm, which is a positive electrode current collector sheet, and dried, followed by a roll press. Thus, the thickness of the coating film was rolled to 140 μm (apparent density 3.5 g / cm ³ ) to obtain the positive electrode 1 having a width of 54 mm.

Production Example 3 (Manufacture of negative electrode)
Using the following negative electrode active material 1, negative electrode active material 2, binder, and water, negative electrode active material 1 (BF15SP (manufactured by Chuetsu Graphite Industries), true specific gravity 2.2 g / cm ³ ): negative electrode active material 2 (MH− 1 (manufactured by Nippon Steel Co., Ltd.) true specific gravity 2.2 g / cm ³ ): The mixing ratio of binder (Serogen 4H (Daiichi Kogyo Seiyaku Co., Ltd.) true specific gravity: 1.4 g / cm ³ ) is 58.8. : 39.2: 2 (weight ratio), respectively, was weighed. After a certain amount of water is put into a kneader and the binder is dissolved, the negative electrode active material 1 and the negative electrode active material 2 are added and kneaded, and water is added again to adjust the viscosity to 2100 ± 500 cp. A negative electrode mixture was obtained. The negative electrode mixture was applied to a predetermined portion on both sides of a Cu foil having a thickness of 12 μm and no voids as a negative electrode current collector sheet, dried, and then roll-pressed to form a coating film having a thickness of 140 μm (apparent density 1.45 g / cm ³ ) to obtain a negative electrode 1 having a width of 56 mm.

Example 1 (nonaqueous electrolyte secondary battery)
Positive electrode 1 (width 54 mm, length 560 mm), negative electrode tab (nickel) in Production Example 2 in which the laminated film (width 60 mm, length 700 mm) in Production Example 1 was used as a separator and a positive electrode tab (aluminum) was welded. Using the negative electrode 1 (width 56 mm, length 600 mm) in the production example 3 in which was welded, the positive electrode 1, the separator, and the negative electrode were laminated and wound in this order. The obtained electrode group was put into a battery can for 18650 cylindrical batteries, necked with a desktop lathe, and the bottom of the negative electrode tab and the positive electrode tab were welded to the lid, followed by vacuum drying. Thereafter, 5 g (positive electrode, negative electrode and negative electrode) of a non-aqueous electrolyte (made by Kishida Chemical, specific gravity: 1.21 g / cm ³ ) containing 1.3 mol / L of LiPF ₆ salt in a carbonate solvent in a glove box under an argon gas atmosphere Non-aqueous electrolyte secondary battery 1 (18650 cylindrical battery) was manufactured by injecting into a battery can, and caulking.

  As a result of performing a cycle test on each of the obtained two non-aqueous electrolyte secondary batteries 1 by the test method of the non-aqueous electrolyte secondary battery described above, the first cycle discharge in the cycle test charge / discharge condition 1 was performed. The discharge capacity (discharge capacity retention rate) at the 500th cycle relative to the capacity was as good as 84%, and neither swelling nor liquid leakage could be confirmed for the battery after the test. In addition, the discharge capacity at 500th cycle (discharge capacity retention rate) with respect to the discharge capacity at 1st cycle under cycle test charge / discharge condition 2 is as good as 60% or more. Was not.

Example 2
A nonaqueous electrolyte secondary battery 2 was produced in the same manner as in Example 1 except that 7 g of nonaqueous electrolyte (corresponding to 1.52 times the total volume of voids in the positive electrode, the negative electrode, and the separator) was injected. . As a result of performing a cycle test on each of the obtained two non-aqueous electrolyte secondary batteries 2 by the test method for the non-aqueous electrolyte secondary battery described above, the first cycle discharge in the cycle test charge / discharge condition 1 was performed. The discharge capacity (discharge capacity retention rate) at the 500th cycle with respect to the capacity was 87% to 88%, both of which were favorable, and neither swelling nor liquid leakage could be confirmed for the battery for which the test was completed. In addition, the discharge capacity (discharge capacity retention rate) of the 500th cycle with respect to the discharge capacity of the first cycle under the cycle test charge / discharge condition 2 is very good at 65% or more. It was not confirmed.

Example 3
A nonaqueous electrolyte secondary battery 3 was prepared in the same manner as in Example 1 except that 4.5 g of nonaqueous electrolyte (corresponding to 0.98 times the total volume of voids in the positive electrode, negative electrode, and separator) was injected. Manufactured. As a result of performing a cycle test on each of the obtained two nonaqueous electrolyte secondary batteries 3 by the test method of the nonaqueous electrolyte secondary battery described above, the first cycle discharge in the cycle test charge / discharge condition 1 was performed. The discharge capacity (discharge capacity retention ratio) at the 500th cycle relative to the capacity was 79.7% in all cases. Further, no swelling or liquid leakage was confirmed for the battery that had been tested.
In addition, the discharge capacity at 500th cycle (discharge capacity retention rate) with respect to the discharge capacity at 1st cycle in cycle test charge / discharge condition 2 is 54% or more, and no swelling or liquid leakage was confirmed for the battery after the test. It was.

Example 4
A nonaqueous electrolyte secondary battery 4 was produced in the same manner as in Example 1, except that 6 g of nonaqueous electrolyte (corresponding to 1.32 times the total volume of voids in the positive electrode, the negative electrode, and the separator) was injected. . About each of the obtained two non-aqueous electrolyte secondary batteries 4, a cycle test was performed by the test method for the non-aqueous electrolyte secondary battery described above. As a result, the first cycle discharge in the cycle test charge / discharge condition 1 was performed. The discharge capacity (discharge capacity retention rate) at the 500th cycle with respect to the capacity was 87% to 88%, both of which were favorable, and neither swelling nor liquid leakage could be confirmed for the battery for which the test was completed. In addition, the discharge capacity (discharge capacity retention rate) of the 500th cycle with respect to the discharge capacity of the first cycle under the cycle test charge / discharge condition 2 is very good at 65% or more. It was not confirmed.

Comparative Example 1
A comparative secondary battery 1 was produced in the same manner as in Example 3 except that a separator made of a polyethylene porous membrane having a thickness of 16 μm was used (the volume of the electrolyte is the volume of the voids in the positive electrode, the negative electrode, and the separator). It was set to 0.98 times the total volume.) The obtained comparative secondary battery 1 was subjected to a cycle test by the above-described test method for a non-aqueous electrolyte secondary battery. As a result, in cycle test charge / discharge condition 1, the 500th cycle relative to the first cycle discharge capacity was obtained. The discharge capacity (discharge capacity maintenance rate) was 77%, which was not sufficient. Furthermore, in charge / discharge test condition 2, the discharge capacity at 500th cycle (discharge capacity retention rate) with respect to the discharge capacity at 1st cycle was less than 40%. Batteries and liquid leakage were not confirmed for the batteries that had been tested.

Comparative Example 2
A comparative secondary battery 2 was produced in the same manner as in Example 1 except that 8 g of non-aqueous electrolyte (corresponding to 1.7 times the total volume of voids in the positive electrode, negative electrode, and separator) was injected. Each of the obtained two comparative secondary batteries 2 was subjected to a cycle test by the above-described test method for a non-aqueous electrolyte secondary battery. As a result, the discharge capacity of the first cycle in the cycle test charge / discharge condition 1 was 500. The discharge capacity (discharge capacity retention rate) at the cycle was 75%, which was not sufficient. Moreover, about the battery which completed the test, the slight swelling was confirmed by the battery can bottom. This swelling is presumed to be due to gas generation from the electrolyte solution, and it is presumed that this swelling caused distortion in the electrode group, and lithium precipitated in the electrode group, leading to a decrease in the discharge capacity retention rate.

Claims (11)

  A positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, containing a heat-resistant material, and a non-aqueous electrolyte, and the amount (volume) of the non-aqueous electrolyte is a gap in the positive electrode, the negative electrode, and the separator A non-aqueous electrolyte secondary battery characterized by having a total volume of 0.9 times or more and 1.6 times or less.   The positive electrode is a positive electrode in which a positive electrode active material that can be doped / undoped with lithium ions is applied to at least one surface of a positive electrode current collector sheet, and the negative electrode is doped / dedoped with lithium ions. The non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material is a negative electrode formed by applying at least one surface of a negative electrode current collector sheet.   The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the separator containing the heat-resistant material is a separator made of a laminated film in which a heat-resistant porous layer and a porous film are laminated.   4. The nonaqueous electrolyte secondary battery according to claim 2, wherein the heat resistant porous layer is a heat resistant porous layer containing a heat resistant resin.   The nonaqueous electrolyte secondary battery according to claim 4, wherein the heat resistant resin is a nitrogen-containing aromatic polymer.   The nonaqueous electrolyte secondary battery according to claim 4 or 5, wherein the heat resistant resin is an aromatic polyamide.   The nonaqueous electrolyte secondary battery according to claim 4, wherein the heat resistant porous layer contains a filler.   The nonaqueous electrolyte secondary battery according to claim 7, wherein a weight of the filler is 20 or more and 95 or less, where 100 is a total weight of the heat resistant porous layer. The heat-resistant porous layer contains two or more fillers, and among the values obtained by measuring the average particle diameter of the particles constituting each of the two or more fillers, the first largest value is D ₁ , 2 9. The nonaqueous electrolyte secondary battery according to claim 7, wherein a value of D ₂ / D ₁ is 0.15 or less when the _second largest value is D ₂ .   The nonaqueous electrolyte secondary battery according to claim 3, wherein the heat-resistant porous layer has a thickness of 1 μm or more and 10 μm or less.   The non-aqueous electrolyte secondary battery according to claim 3, wherein the porous film is a porous film containing a polyolefin resin.