JP2010244818A - Nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery for suppressing occurrence of a fine short circuit and having boosting charge characteristics and excellent productivity. <P>SOLUTION: The nonaqueous secondary battery includes a cathode, an anode, and nonaqueous electrolyte. The anode includes an anode mixture layer containing a lithium-titanium compound oxide at least on one surface of a current collector, and the anode mixture layer includes a porous layer containing, on a surface of an opposite side to the current collector, 10 vol.% or less of heat resistant particulates both in a ratio of particles of a particle diameter 0.2 μm or less and in a ratio of particles of a particle diameter 2 μm or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-aqueous secondary battery that can suppress the occurrence of a fine short circuit and has good quick charge characteristics and productivity.

  The demand for non-aqueous secondary batteries is rapidly increasing, for example, for use as a power source for portable devices such as mobile phones and laptop computers.

  By the way, in a non-aqueous secondary battery, in general, a positive electrode and a negative electrode are laminated with a separator interposed therebetween to form a laminated electrode body, or further, this is wound into a spiral shape to form a wound electrode body. The structure which accommodated the electrode body in the battery case with the nonaqueous electrolyte solution is employ | adopted. However, since it is necessary to prevent a short circuit due to contact between the positive electrode and the negative electrode in the non-aqueous secondary battery, the positional relationship between the positive electrode, the negative electrode and the separator must be strictly regulated, which lowers the production efficiency of the battery. It was a factor.

  For example, Patent Document 1 discloses a technique for directly forming an insulating layer on the surface of an electrode. By adopting such a technique, it may be possible to avoid the use of a separator, which may prevent a decrease in battery production efficiency due to strict regulation of the positional relationship between the positive and negative electrodes and the separator.

JP-A-9-92280

  However, in the negative electrode using a carbon material widely used in conventional non-aqueous secondary batteries as the negative electrode active material, the operating potential region is close to the deposition region of metallic lithium, so when metallic lithium is deposited during charge / discharge Therefore, a fine short circuit is likely to occur, and there is a possibility that the fine short circuit cannot be sufficiently suppressed only by the insulating layer formed on the surface of the electrode.

  In recent years, non-aqueous secondary batteries are not only used for the power supply of portable devices as described above, but also are being developed for use as industrial power supplies or on-vehicle power supplies. Therefore, for example, an improvement in quick charge characteristics that enables charging in a very short time is also required.

  However, for example, an ordinary separator (polyolefin separator) is also used in order to suppress a fine short circuit when metallic lithium is deposited during charging and discharging while forming the insulating layer on the surface of the electrode. When a battery is configured, the charging characteristics are impaired and rapid charging cannot be supported.

  This invention is made | formed in view of the said situation, The objective is to provide the non-aqueous secondary battery which can suppress generation | occurrence | production of a fine short circuit and has favorable quick charge characteristics and productivity.

  The non-aqueous secondary battery of the present invention that has achieved the above object is a non-aqueous secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the negative electrode contains a lithium titanium composite oxide. A mixture layer is provided on at least one surface of the current collector, and the negative electrode mixture layer has a ratio of particles having a particle diameter of 0.2 μm or less on the surface opposite to the current collector, and particles Each of the particles having a diameter of 2 μm or more has a porous layer containing heat-resistant fine particles having a volume of 10% by volume or less.

  In the non-aqueous secondary battery of the present invention, a porous layer containing heat-resistant fine particles of a specific particle size is formed on the surface of the negative electrode mixture layer opposite to the current collector. Even if a slight misalignment occurs between the negative electrode and the separator, the porous layer can prevent a short circuit due to contact between the positive and negative electrodes, and it is also possible to avoid the use of the separator itself as described later. Therefore, restrictions on the positional relationship between the positive and negative electrodes and the separator during battery manufacture can be relaxed, and the production efficiency can be increased.

  The non-aqueous secondary battery of the present invention uses a lithium-titanium composite oxide as a negative electrode active material that does not generate metallic lithium during charge / discharge due to a high operating voltage and is unlikely to cause a fine short circuit. Therefore, the porous layer formed on the negative electrode surface can be used as a substitute for the separator, and the use of the separator itself can be omitted.

  Furthermore, in the non-aqueous secondary battery of the present invention, since the heat-resistant fine particles having a specific particle size are used for forming the porous layer, for example, a porous layer having good properties can be obtained while being thinned. The rapid charging characteristics can be enhanced by the action of such a porous layer and the lithium titanium composite oxide used for the negative electrode active material.

  The non-aqueous secondary battery of the present invention suppresses the occurrence of fine short-circuits by the above-described actions, thereby improving the quick charge characteristics and the productivity.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of a fine short circuit can be suppressed and a non-aqueous secondary battery with favorable quick charge characteristics and productivity can be provided.

It is a cross-sectional schematic diagram which shows an example of the negative electrode which concerns on the nonaqueous secondary battery of this invention.

  The nonaqueous secondary battery of the present invention has a negative electrode mixture layer containing a lithium titanium composite oxide as an active material on at least one side of a current collector, and the negative electrode mixture layer is opposite to the current collector. The negative electrode which has a porous layer on the surface is provided.

  FIG. 1 is a schematic cross-sectional view showing an example of a negative electrode according to the battery of the present invention. In the negative electrode 1 of FIG. 1, a negative electrode mixture layer 3 containing a lithium titanium composite oxide as an active material is provided on one surface (upper side in the figure) of a current collector 4. The porous layer 2 is provided on the surface opposite to the current collector 4.

  Lithium titanium composite oxide, which is a negative electrode active material, has high thermal stability, and lithium dendrite hardly occurs in a battery having a negative electrode using such an active material. Therefore, even if the charging current value is increased, the reliability and safety of the battery can be ensured, so that the quick charging characteristics are improved.

  In addition, since lithium titanium composite oxide has high thermal stability and is difficult to generate heat, in a battery configured using a negative electrode containing this in an active material, it is not necessary to ensure shutdown characteristics by using a separator. Safety can be secured. Furthermore, the occurrence of a fine short circuit due to lithium dendrite can be suppressed. Therefore, it is also possible to configure a battery using only the porous layer formed on the surface of the negative electrode mixture layer as a separator without separately using a separator for preventing a fine short circuit caused by lithium dendrite.

As the lithium titanium composite oxide, an oxide typified by a composition such as Li ₄ Ti ₅ O ₁₂ or LiTi ₂ O ₄ can be used, and in particular, one having a spinel structure typified by Li ₄ Ti ₅ O ₁₂ Is preferably used.

A lithium titanium composite oxide having a ramsdellite type crystal structure can also be used. Examples of such lithium-titanium composite oxide include oxides represented by compositions such as Li ₂ Ti ₃ O ₇ and Li ₄ Ti ₅ O _12, and are particularly represented by Li ₂ Ti ₃ O _7. Those are preferably used. In the case of this Li ₂ Ti ₃ O ₇ , the d value of the main peak by the X-ray diffraction method using Cu as a target is 0.445 nm, 0.269 nm, 0.224 nm, and 0.177 nm (each ± 0.0002 nm). Preferably there is.

  In any of the lithium titanium composite oxides, some of the constituent elements are other elements such as Ca, Mg, Sr, Sc, Zr, V, Nb, W, Cr, Mo, Mn, Fe, Co, Ni. , Cu, Zn, Al, Si, Ga, Ge, Sn and the like may be substituted. In this case, the substitution amount with other elements is preferably 10 mol% or less of the element to be substituted.

  In the negative electrode according to the present invention, the active material may be only the lithium titanium composite oxide, or an active material other than the lithium titanium composite oxide (hereinafter referred to as “other active material”) may be used in combination. Other active materials include, for example, carbon materials such as graphite, pyrolytic carbons, cokes, glassy carbons, fired organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers; Si, Sn , Ge, Bi, Sb, In and other elements that can be alloyed with lithium, alloys thereof or oxides thereof. In addition, when using together lithium titanium complex oxide and another active material, it is preferable that the said lithium titanium complex oxide is 80 mass% or more in all the active materials in a negative electrode, and is 100 mass% ( That is, it is more preferable to use only lithium titanium composite oxide.

In addition, the lithium titanium composite oxide in the negative electrode according to the present invention has a specific surface area of preferably 5 m ² / g or more, and more preferably 10 m ² / g or more. By increasing the specific surface area of the lithium-titanium composite oxide as described above, the electrode area can be increased, so that the quick charge characteristics of the battery can be further enhanced, the output characteristics of the battery and long-term reliability. It can also improve sex. The specific surface area of the lithium titanium composite oxide is preferably 20 m ² / g or less.

  The specific surface area of the lithium-titanium composite oxide is a specific surface area of the active material surface and the micropores, as measured and calculated using the BET formula, which is a theoretical formula for multi-layer adsorption. Specifically, it is a value obtained as a BET specific surface area using a specific surface area measuring device (“Macsorb HM model-1201” manufactured by Mounttech) by a nitrogen adsorption method.

  The particle diameter of the lithium titanium composite oxide is preferably 3 to 20 μm as an average particle diameter. With such a fine form of lithium titanium composite oxide, the specific surface area can be increased as described above. Further, when the lithium titanium composite oxide having such a fine form as described above is used, a negative electrode having a thin negative electrode mixture layer can be obtained, and this can also increase the electrode area.

  The average particle diameter of the lithium-titanium composite oxide referred to in this specification means a volume average value measured by a laser diffraction particle size distribution measurement method using “MICROTRAC HRA (model: 9320-X100)” manufactured by Microtrack. ing.

  The negative electrode mixture layer is, for example, a negative electrode mixture-containing composition in which the negative electrode active material, a binder, and, if necessary, a negative electrode mixture containing a conductive auxiliary agent are dispersed in a solvent (the binder is dissolved in the solvent). It may be formed through a step of preparing a current collector, applying it to one or both sides of a current collector, and drying. In addition, you may form a negative mix layer by methods other than the above.

  Examples of the binder used in the negative electrode mixture layer include starch, polyvinyl alcohol, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose and other modified polysaccharides; polyvinyl chloride, polyvinyl pyrrolidone, poly Thermoplastic resins such as tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyamide and their modified products; polyimide; ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR) , Butadiene rubber, polybutadiene, fluororubber, polyethylene oxide and other polymers having rubber-like elasticity and modified products thereof, and the like, Or more can be used species.

  When the conductive additive is contained in the negative electrode mixture layer, examples of the conductive aid include graphite, carbon black, acetylene black, and the like, and one or more of these can be used. It is preferable to use carbon black as a component.

  As a component composition in a negative mix layer, it is preferable that the quantity of a negative electrode active material shall be 90-99 mass%, and the quantity of a binder shall be 1-10 mass%. Moreover, when using a conductive support agent, it is preferable that the quantity of the conductive support agent in a negative mix layer shall be 1-10 mass%.

  By making the thickness of the negative electrode mixture layer thinner, the area of the negative electrode that can be introduced into the battery can be increased, and the quick charge characteristics of the battery can be further improved, and the output and long-term reliability can be improved. Therefore, the thickness per side of the current collector is preferably 40 μm or less, and more preferably 30 μm or less. However, for the reason that it is difficult to form a very thin negative electrode mixture layer, the thickness of the negative electrode mixture layer is preferably 10 μm or more, more preferably 20 μm or more in terms of the thickness per side of the current collector. It is more preferable.

  For the current collector of the negative electrode, a foil made of copper, nickel, stainless steel, aluminum, titanium, etc., a plain weave metal net, an expanded metal, a lath net, a punching metal, or the like can be used. The thickness of the current collector is preferably 30 μm or less, and preferably 10 μm or more.

  The porous layer formed on the surface of the negative electrode mixture layer of the negative electrode (the surface opposite to the current collector) is a layer containing heat-resistant fine particles.

  The heat-resistant fine particles have electrical insulating properties, are electrochemically stable, and are stable to a solvent used for a non-aqueous electrolyte and a porous layer forming composition (composition containing a solvent) described later. There is no particular limitation as long as it does not dissolve in the non-aqueous electrolyte at a high temperature. The “heat resistance” in the heat-resistant fine particles means that no chemical reaction occurs or no phase change (melting) occurs at least at 150 ° C.

Specific examples of the heat-resistant fine particles include, for example, oxide fine particles such as iron oxide, Al ₂ O ₃ (alumina), SiO ₂ (silica), TiO ₂ , BaTiO ₃ , and ZrO ₂ ; nitride such as aluminum nitride and silicon nitride Refractory ion particles such as calcium fluoride, barium fluoride and barium sulfate; covalently bonded crystal particles such as silicon and diamond; clay particles such as talc and montmorillonite; boehmite, zeolite, apatite, kaolin and mullite Inorganic fine particles such as spinel, olivine, sericite, bentonite and other mineral resource-derived substances 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); carbonaceous fine particles such as carbon black and graphite; Fine particles imparted with electrical insulation properties by surface treatment with the above-described materials constituting the heat-resistant fine particles may be used. Among these, at least one fine particle selected from the group consisting of alumina, silica and boehmite is preferable. These heat resistant fine particles may be used alone or in combination of two or more.

The form of the heat-resistant fine particles may be any shape such as a spherical shape, a polyhedral shape, and a plate shape, but the heat-resistant fine particles preferably include plate-like particles, and all of the heat-resistant fine particles are plate-shaped. Shaped particles may be used. Examples of the plate-like particles include various commercially available products such as “Sun Lovely (trade name)” (SiO 2) manufactured by Asahi Glass Stech Co., Ltd. and pulverized products (TiO 2 of “NST-B 1 (trade name)” manufactured by Ishihara Sangyo Co., Ltd. ), Sakai Chemical Industry's plate-like barium sulfate “H series (trade name)”, “HL series (trade name)”, Hayashi Kasei's “Micron White (trade name)” (talc), Hayashi Kasei “Bengels (trade name)” (bentonite), “BMM (trade name)” and “BMT (trade name)” (boehmite) manufactured by Kawai Lime Co., Ltd., “Cerasur BMT-B (trade name)” manufactured by Kawai Lime Co., Ltd. ( Alumina), “Seraph (trade name)” (alumina) manufactured by Kinsei Matec Co., Ltd., “Yodogawa Mica Z-20 (trade name)” (sericite) manufactured by Yodogawa Mining Co., Ltd., and the like are available. In _addition, for the _{SiO 2, Al 2 O 3,} ZrO 2, CeO 2, it can be prepared by the method disclosed in JP-A-2003-206475.

  When the heat-resistant fine particles are plate-like, the heat-resistant fine particles are oriented in the porous layer so that the flat plate surface is almost parallel to the surface of the porous layer, thereby improving the occurrence of short circuits. Can be suppressed. This is because the heat-resistant fine particles are oriented as described above so that the heat-resistant fine particles are arranged so as to overlap each other on a part of the flat plate surface. ) Is formed not in a straight line but in a bent shape (that is, the curvature is increased), which prevents lithium dendrite from penetrating through the porous layer, and thus the occurrence of a short circuit is more likely. It is presumed to be well suppressed.

  For example, the aspect ratio (the ratio of the maximum length in the plate-like particle to the thickness of the plate-like particle) is preferably 5 or more, more preferably 10 or more as the form when the heat-resistant fine particles are plate-like particles. Thus, it is preferably 100 or less, more preferably 50 or less. Moreover, the average value of the ratio of the major axis direction length to the minor axis direction length of the tabular surface of the grain is preferably 0.3 or more, more preferably 0.5 or more (ie, the major axis direction length and The length in the minor axis direction may be the same). When the plate-like heat-resistant fine particles have an aspect ratio as described above or an average value of the ratio of the major axis direction length to the minor axis direction length of the flat plate surface, the above-mentioned short-circuit prevention effect is more effectively exhibited. The

  In addition, when the heat-resistant fine particles are plate-like, the average value of the ratio of the long axis direction length to the short axis direction length of the flat plate surface is, for example, image analysis of an image taken with a scanning electron microscope (SEM) Can be obtained. Further, the aspect ratio in the case where the heat-resistant fine particles are plate-like can also be obtained by image analysis of an image taken by SEM.

The heat-resistant fine particles preferably include fine particles having a secondary particle structure in which primary particles are aggregated, and all of the heat-resistant fine particles may be fine particles having the secondary particle structure. . As the secondary particles, aggregates that are difficult to separate into primary particles in a normal dispersion step, for example, primary particles that form a continuous crystal with each other to form secondary particles can be preferably used. . Examples of such fine particles include “Boehmite C06 (trade name)”, “Boehmite C20 (trade name)” (boehmite) manufactured by Daimei Chemical Co., Ltd., “ED-1 (trade name)” manufactured by Yonesho Lime Industry Co., Ltd. ( CaCO ₃ ), J.M. M.M. Examples include “Zeolex 94HP (trade name)” (clay) manufactured by Huber.

  When fine particles having a secondary particle structure in which primary particles are aggregated are used as heat-resistant fine particles, the aggregated secondary particles prevent fine packing of the particles, so that the pores of the porous layer are further reduced. The non-aqueous secondary battery having such a porous layer can be enlarged, and uses such as electric vehicles, hybrid vehicles, electric motorcycles, electric assist bicycles, electric tools, shavers, etc. that require higher output It is suitable for.

  The heat-resistant fine particles have a ratio of particles having a particle diameter of 0.2 μm or less and a ratio of particles having a particle diameter of 2 μm or more in all particles of 10% by volume or less.

  By using the heat-resistant fine particles having the same particle diameter as described above as the heat-resistant fine particles for constituting the porous layer formed on the surface of the negative electrode mixture layer, for example, a porous layer having good properties even when thinned. Since it can form, the quick charge characteristic and productivity of a battery can be improved. That is, if the proportion of particles having a particle diameter of 2 μm or more contained in the heat-resistant fine particles (ratio of coarse particles) is too large, it becomes difficult to form a thin porous layer having good properties. As will be described in detail later, the porous layer according to the negative electrode of the present invention is prepared by forming a slurry for forming a porous layer in which heat-resistant fine particles and the like are dispersed in a solvent, and this is prepared on the surface of the negative electrode mixture layer or the negative electrode mixture. It is formed through a step of applying to the undried coating surface of the agent-containing composition and drying to remove the solvent, but the proportion of particles having a particle diameter of 0.2 μm or less contained in the heat-resistant fine particles is too large. Then, the heat-resistant fine particles easily aggregate in the slurry for forming the porous layer, and it becomes difficult to form a thin porous layer having good properties.

  The proportion of particles having a particle size of 0.2 μm or less in the heat-resistant fine particles is more preferably 0% by volume. The ratio of particles having a particle diameter of 2 μm or more in the heat-resistant fine particles is more preferably 0% by volume.

  Further, the heat-resistant fine particles preferably have an average particle size of 1 μm or less, and more preferably 0.8 μm or less. If the average particle size of the heat-resistant fine particles is too large, it becomes difficult to form a thin porous layer. In addition, the path length of the pores inside the porous layer becomes long, which becomes an obstacle when Li ions pass through the porous layer, and the load characteristics of the battery are likely to deteriorate. On the other hand, if the heat-resistant fine particles are too small, the surface area becomes large, so that the dispersibility of the heat-resistant fine particles in the porous layer decreases or the amount of water adhering to the heat-resistant fine particles increases, resulting in the amount of water in the battery. It may be difficult to control. If the amount of water in the battery increases, the battery characteristics may deteriorate. Therefore, it is preferable that the average particle diameter of the heat-resistant fine particles is 1 μm or more from the viewpoint of suppressing the occurrence of such problems and configuring a battery having better characteristics.

  The average particle size of the heat-resistant fine particles referred to in this specification is a medium that does not swell or dissolve the fine particles using a laser scattering particle size distribution meter (for example, “MT-3000” manufactured by Nikkiso Co., Ltd.). The particle size (median diameter: d50) at 50% of the volume-based integrated fraction measured by dispersing in a dispersion medium used in the slurry for forming a porous layer of the above. Further, the ratio of particles having a particle diameter of 0.2 μm or less in the heat-resistant fine particles and the ratio of particles having a particle diameter of 2 μm or more can also be determined by the particle size distribution measurement when determining the average particle diameter.

  The porous layer preferably contains a binder for the purpose of binding the heat-resistant fine particles to each other or binding the porous layer and the negative electrode mixture layer. The type of the binder is not particularly limited as long as it is electrochemically stable inside the non-aqueous secondary battery and stable with respect to the non-aqueous electrolyte of the non-aqueous secondary battery.

  Specific examples of the binder include, for example, an ethylene-vinyl acetate copolymer (EVA, having a structural unit derived from vinyl acetate of 20 to 35 mol%); an ethylene-ethyl acrylate copolymer, an ethylene-ethyl methacrylate copolymer. (Meth) acrylic acid copolymer such as: fluorinated rubber; styrene-butadiene rubber (SBR); polyvinyl alcohol (PVA); polyvinyl butyral (PVB); polyvinyl pyrrolidone (PVP); poly N-vinylacetamide; Polyurethane, epoxy resin, etc. are used. These binders may be used individually by 1 type, and may use 2 or more types together.

  Among the binders exemplified above, a heat-resistant binder (heat-resistant resin) is preferable. The “heat resistance” of the binder here means that no chemical reaction occurs or does not flow at least at 150 ° C. By using such a heat-resistant binder, the heat resistance of the porous layer can be further increased, so that a battery with higher safety can be obtained.

  Among the heat-resistant binders, highly flexible binders such as ethylene-acrylic acid copolymer, fluorine-based rubber, and SBR are particularly preferable. Specific examples include “Evaflex series (EVA, trade name)” manufactured by Mitsui DuPont Polychemical Co., Ltd., EVA manufactured by Nihon Unicar Co., Ltd., and “Evaflex-EEA Series (ethylene-acrylic) manufactured by Mitsui DuPont Polychemical Co., Ltd. Acid copolymer, trade name) ", EEA made by Nihon Unicar," Daiel Latex Series (fluoro rubber, trade name) "by Daikin Industries," TRD-2001 (SBR, trade name) by JSR "EM-400B (SBR, trade name)" manufactured by Zeon Corporation. Further, a low glass transition temperature cross-linked acrylic resin [self-crosslinkable (meth) acrylic acid copolymer] having a structure in which (meth) acrylic acid as a main component of a monomer and cross-linking this is also preferable.

  Among these, a (meth) acrylic acid copolymer having a crosslinked structure is more preferable, and a (meth) acrylic acid copolymer having a crosslinked structure and having a glass transition temperature (Tg) of −20 ° C. or lower is further preferable. . As a specific example of the compound having Tg, a terminal of the side chain ester group is preferably an alkyl group having 2 to 10 carbon atoms, and more specifically, the main terminal of the side chain ester group is More preferably, the copolymer is an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group or an n-hexyl group. If the carbon number of the terminal alkyl group of the side chain ester group is too small, the Tg of the binder becomes higher and the flexibility is lowered. Moreover, when there are too many carbon atoms of the terminal alkyl group of a side chain ester group, side chains will crystallize and the flexibility of a binder will fall on the contrary.

  In addition, by using a self-crosslinkable (meth) acrylic acid copolymer as a binder, the resistance of the formed porous layer to the non-aqueous electrolyte is further improved compared to the case where a binder having no crosslinked structure is used. Can be made.

  In order to obtain a self-crosslinking (meth) acrylic acid copolymer, a (meth) acrylic acid copolymer can be obtained by a conventionally known method, for example, using a monomer capable of imparting self-crosslinking property according to a conventional method. A polymer may be synthesized. Examples of monomers capable of imparting self-crosslinkability include, for example, unsaturated monomers having self-crosslinkable functional groups; monomers having functional groups such as hydroxyl groups and carboxyl groups [including acrylates and methacrylates] And a combination of a functional monomer having a functional group that reacts with a hydroxyl group or a carboxyl group.

  Examples of unsaturated monomers having a self-crosslinkable functional group include methylol group-containing monomers such as N-methylol methacrylamide, N-methylol acrylamide, N-butyrol methacrylamide, and N-butyrol acrylamide; Epoxy group-containing monomers such as allyl glycidyl ether and glycidyl (meth) acrylate; alkoxyalkyl groups such as methoxymethyl (meth) acrylate, ethoxymethyl (meth) acrylate, methoxyethyl (meth) acrylate, and butoxyethyl (meth) acrylate Containing monomer; acetoacetoxyalkyl (meth) acrylate such as 2-acetoacetoxyethyl (meth) acrylate, 3-acetoacetoxypropyl (meth) acrylate, 4-acetoacetoxybutyl (meth) acrylate Conductor; vinyl monomer having hydrolyzed silyl group such as vinyltrimethoxysilane, vinylmethoxydimethylsilane, vinyltrichlorosilane, allyltrichlorosilane; aziridinyl group-containing single monomer such as 2- (1-aziridinyl) ethyl (meth) acrylate [In the present specification, “(meth) acrylate” means both acrylate and methacrylate. ].

  Examples of the monomer having a functional group such as a hydroxyl group or a carboxyl group include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, β-hydroxyethyl (meth) acrylate, β -Hydroxypropyl (meth) acrylate, (beta) -hydroxyethyl vinyl ether, etc. are mentioned. Examples of the functional monomer having a functional group that reacts with a hydroxyl group or a carboxyl group include N-methylol group-containing monomers such as N-methylolacrylamide and N-butoxymethylacrylamide; dimethylaminoethyl (meth) acrylate And amino group-containing monomers such as dimethylaminopropylacrylamide; epoxy group-containing monomers such as glycidyl (meth) acrylate;

  Among self-crosslinking (meth) acrylic acid copolymers, a low Tg acrylic acid copolymer obtained by using butyl acrylate as a main component of a monomer is particularly preferable.

  In addition to the specific examples of the binder, an amine compound or a polyacrylic resin is mixed with a known resin to increase flexibility, lower Tg, or a known plasticizer (phthalate) as a flexibility-imparting additive. For example, an acid ester or the like may be blended to improve the elongation at break. Moreover, the adhesiveness of a binder can also be improved by introduce | transducing a carboxyl group. In order to increase the Tg of the resin, a known method such as introducing a cross-linked structure to increase its cross-link density or introducing a rigid molecular structure (such as an aryl group) can be employed. In order to lower, a known method such as introduction of a crosslinked structure having a low crosslinking density or introduction of a long side chain can be employed.

  The content of the binder in the porous layer is preferably 1 or more in terms of a volume ratio when the volume of the heat-resistant fine particles is 100, from the viewpoint of more effectively exerting the action due to the use of the binder. More preferably, it is more preferably 10 or more. In addition, if the amount of the binder in the porous layer is too large, pores are filled in the formed porous layer, and the ion permeability is lowered, which may adversely affect the characteristics of the nonaqueous secondary battery. For this reason, the content is preferably 30 or less, more preferably 20 or less, as a volume ratio when the volume of the heat-resistant fine particles is 100.

  The thickness of the porous layer is preferably 5 μm or more, and more preferably 10 μm or more, from the viewpoint of ensuring the above-described effect due to the formation of the porous layer. However, if the porous layer is too thick, the effect of improving the rapid charge characteristics of the battery may be reduced. Therefore, the thickness is preferably 30 μm or less, and more preferably 20 μm or less.

The porosity of the porous layer is preferably 20% or more and preferably 30% or more in the dried state in order to secure the liquid retention amount of the non-aqueous electrolyte and improve the ion permeability. It is more preferable. On the other hand, from the viewpoint of preventing internal short circuit, the porosity of the porous layer is preferably 70% or less, and more preferably 60% or less in a dry state. The porosity of the porous layer: P (%) can be calculated by calculating the sum of each component i from the thickness of the porous layer, the mass per area, and the density of the constituent components using the following equation. .
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 the porous layer (g / cm ²⁾ ), T: thickness of the porous layer (cm).

  As described above, the porous layer is prepared by dispersing a slurry for forming a porous layer prepared by dispersing heat-resistant fine particles, a binder or the like in a solvent (the binder may be dissolved in the solvent) or the surface of the negative electrode mixture layer or It forms through the process of apply | coating to the undried coating film surface of the composition for negative mix layer formation, and drying. According to such a forming method, the layer can be made porous.

  As the dispersion medium for the slurry for forming the porous layer, water-based materials and organic solvents (aromatic hydrocarbons such as toluene; furans such as tetrahydrofuran; ketones such as methyl ethyl ketone and methyl isobutyl ketone; etc.) are used. Although mentioned, what has water as a main component is preferable. The “dispersion medium” as used in the present invention refers to the remaining part of the slurry for forming a porous layer, excluding the solid content remaining upon drying during the formation of the porous layer. Further, “having water as the main component” means that 70% by mass or more of water is contained among the constituent components in the dispersion medium. Examples of the other dispersion medium in the case of containing water as a main component include the following alcohols added for controlling the interfacial tension of the slurry for forming a porous layer. From the viewpoint of environmental protection, it is particularly preferable to use only water as a dispersion medium.

  It is preferable to use a thickener in the slurry for forming the porous layer. By using a thickener, the viscosity of the slurry for forming the porous layer is adjusted to a suitable range, the dispersion of the heat-resistant fine particles is made uniform, and an excellent dispersion state can be stably maintained.

  The thickener may be any thickener that can adjust the slurry to the required viscosity without causing side effects such as aggregation of heat-resistant fine particles in the slurry for forming the porous layer. Those having a viscous action are preferred. Moreover, it is preferable that a thickener can melt | dissolve or disperse | distribute favorably with respect to the dispersion medium used for a slurry. When a large number of undissolved parts and aggregates are present in the slurry, the dispersion of the heat-resistant fine particles becomes uneven, and in the porous layer formed by applying the slurry to a substrate or the like and drying, There is a risk of non-uniform distribution. Therefore, there is a possibility that the heat resistance of the porous layer is lowered, and as a result, the reliability and heat resistance of the battery may be lowered.

  In addition, as a standard of the undissolved content of the thickener remaining in the slurry for forming the porous layer and the content of aggregates, when the slurry is passed through a mesh filter having an opening of 30 μm, the residue remaining on the filter The number is preferably 1 or less per 1 L of slurry, and more preferably 1 or less per 5 L of slurry.

  Specific examples of thickeners include synthetic polymers such as polyethylene glycol, polyacrylic acid, polyvinyl alcohol, vinyl methyl ether-maleic anhydride copolymer; cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose; xanthan gum Natural polysaccharides such as welan gum, gellan gum, guar gum and carrageenan, starches such as dextrin and pregelatinized starch; clay minerals such as montmorillonite and hectorite; inorganic oxides such as fumed silica, fumed alumina and fumed titania And so on. These may be used alone or in combination of two or more. In the case of the above clay minerals and inorganic oxides, it is preferable to use those whose primary particles are smaller than the heat-resistant fine particles (for example, about several nm to several tens of nm). Those having a structure structure in which many are connected (such as fumed silica) are preferable.

  Among the thickeners exemplified above, natural polysaccharides having high solubility in water as a dispersion medium suitable for the slurry for forming a porous layer and high thickening effect in a small amount are more preferable, xanthan gum, welan gum, gellan gum. Is more preferable, and xanthan gum is particularly preferable. Moreover, when providing thixotropy to the slurry for forming a porous layer, it is preferable to add inorganic oxides such as fumed silica, fumed alumina, fumed titania and the like.

  The content of the thickener in the slurry for forming the porous layer varies depending on the viscosity of the slurry for forming the porous layer to be set. For example, a thickener that does not volatilize in the drying step after slurry application is used. In some cases, it remains in the porous layer, so it is not preferable to use a large amount. Specifically, in the entire volume of solids in the slurry (components excluding the dispersion medium; the same applies hereinafter). It is preferably 10% by volume or less, more preferably 5% by volume or less, and still more preferably 1% by volume or less. Moreover, it is preferable that content of the thickener in the slurry for porous layer formation is 0.1 volume% or more in the total volume of the solid content in a slurry.

  Moreover, it is preferable to use a dispersing agent for the slurry for forming a porous layer. By using the dispersant, for example, the dispersant adheres to the surface of the heat-resistant fine particles, so that the dispersibility of the heat-resistant fine particles in the slurry for forming the porous layer is further improved, and the aggregation of the heat-resistant fine particles is caused. This prevents the heat resistant fine particles from being dispersed more stably.

  Furthermore, for example, when the heat-resistant fine particles are plate-like particles, depending on the production method, the particles may be obtained in a state where the plate surfaces of the particles are overlapped (for example, plate-like boehmite). When the porous layer is formed using the slurry for forming a porous layer in which each particle is present in a laminated state as described above, the above-mentioned effect due to the use of plate-like particles may not be sufficiently obtained. If a slurry for forming a porous layer is prepared using a dispersing agent together with the aggregated particles, individual particles can be separated and uniformly dispersed in the slurry. Therefore, according to the slurry for forming a porous layer using a dispersing agent, even when plate-like particles are used, it is possible to form a porous layer that exhibits its effect better.

  Specific examples of the dispersant include various anionic, cationic, and nonionic surfactants such as polycarboxylic acid, polyacrylic acid, polymethacrylic acid, polycarboxylate, polyacrylate, and polymethacrylate. Polymeric dispersants; etc. can be used. More specifically, ADEKA “Adekator (trade name) series”, “Adekanol (trade name) series”, San Nopco “SN Dispersant (trade name) series”, Lion “Politi (trade name)” "Series", "Armin (trade name) series", "Duomin (trade name) series", "Homogenol (trade name) series", "Leodoll (trade name) series", "Amate (trade name) series" , “Falback (trade name) series”, “Ceramisole (trade name) series”, “Polystar (trade name) series” manufactured by NOF Corporation, “Ajisper (trade name) series” manufactured by Ajinomoto Fine Techno Co., Ltd., Toagosei Co., Ltd. "Aron Dispersant (trade name) series" manufactured by the company. As the dispersant, those exemplified above may be used alone or in combination of two or more.

  Among these dispersants, since the action of dispersing fine particles is strong, ion dissociable acid groups (carboxyl group, sulfonic acid group, amino acid group, maleic acid group, etc.) or ion dissociable acid bases (carboxylate bases) , Sulfonate groups, maleate groups, etc.) are preferred, and polycarboxylates, polyacrylates and polymethacrylates are more preferred. When the polymer dispersant is a salt (having an acid base), an ammonium salt is preferable.

  The content of the dispersant in the slurry for forming the porous layer is preferably 0.1 parts by mass or more with respect to 100 parts by mass of the heat-resistant fine particles, from the viewpoint of more effectively exerting the action. More preferably, it is at least part by mass. If the amount of the dispersant in the slurry for forming the porous layer is excessively increased, not only the effect is saturated, but also the ratio of other components in the porous layer may be reduced, and the effect of them may be reduced. is there. Therefore, the content of the dispersant in the slurry for forming the porous layer is preferably 5 parts by mass or less, and more preferably 1 part by mass or less with respect to 100 parts by mass of the heat-resistant fine particles.

  To the slurry for forming the porous layer, additives can be appropriately added for the purpose of controlling the interfacial tension. As the additive, when the dispersion medium is an organic solvent, alcohol (ethylene glycol, propylene glycol, etc.) or various propylene oxide glycol ethers such as monomethyl acetate can be used. When the dispersion medium is water Alternatively, the interfacial tension can be controlled by using alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, etc.).

  When plate-like particles are used as the heat-resistant fine particles, in order to increase the orientation of the plate-like particles contained in the porous layer and to make the function work more effectively, it is for porous formation containing the plate-like particles. A method of applying a shear or a magnetic field to the slurry after applying the slurry to the surface of the negative electrode mixture layer may be used. For example, after applying a slurry for forming a porous layer containing plate-like particles to the surface of the negative electrode mixture layer, the slurry can be sheared by passing through a certain gap.

  The non-aqueous secondary battery of the present invention only needs to have the above-described negative electrode, and there is no particular limitation on the other configuration and structure, and the configuration adopted in conventionally known non-aqueous secondary batteries And can adopt structure.

  The positive electrode according to the nonaqueous secondary battery of the present invention has, for example, a positive electrode mixture layer containing a positive electrode active material, a conductive additive, a binder and the like. Those formed on one side or both sides are mentioned.

  As the positive electrode active material, conventionally known positive electrode active materials used in non-aqueous secondary batteries can be used. Specific examples include lithium manganate, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt manganese composite oxide, vanadium oxide, and molybdenum oxide. In addition, two or more kinds may be used in combination. When vanadium oxide or molybdenum oxide is used as the positive electrode active material, it is necessary to introduce lithium used for charging / discharging the battery. This lithium can be introduced, for example, by attaching a lithium foil to the surface of the positive electrode or the negative electrode.

  As the conductive additive for the positive electrode, graphite, carbon black, acetylene black, or the like can be used, but it is more preferable to use carbon black as the main component.

  As the binder for the positive electrode, polytetrafluoroethylene (PTFE) dispersion, powdered PTFE, rubber binder, polyvinylidene fluoride (PVDF), or the like can be used, but PVDF is more preferable.

  As the positive electrode current collector, a foil made of aluminum, titanium or the like, a plain weave metal net, an expanded metal, a lath net, a punching metal, or the like can be used, but an aluminum foil is more preferable. The thickness of the current collector is preferably 10 to 20 μm.

  For the positive electrode, for example, a positive electrode mixture-containing composition is prepared by dispersing the positive electrode mixture composed of the above-described positive electrode active material, conductive additive, binder, and the like in a solvent such as N-methyl-2-pyrrolidone (NMP). (The binder may be dissolved in a solvent), which is applied to one or both sides of the current collector, dried, and subjected to press treatment as necessary to form a positive electrode mixture layer. it can. In addition, the manufacturing method of the positive electrode which concerns on this invention is not necessarily limited to the said manufacturing method, You may manufacture by another manufacturing method.

  In the positive electrode mixture layer related to the positive electrode, the content of the positive electrode active material is 95 to 99% by mass, the content of the conductive auxiliary agent is 0.5 to 2% by mass, and the content of the binder is 0.5 to 3% by mass. It is preferable that Moreover, it is preferable that the thickness of a positive mix layer is 40-100 micrometers per single side | surface of a positive electrode electrical power collector.

  In the battery of the present invention, a laminated electrode body in which a positive electrode (a plate-like positive electrode) and a negative electrode (a plate-like negative electrode) are laminated, and a spirally wound electrode body obtained by winding this in a spiral shape together with a non-aqueous electrolyte It can be accommodated in a battery container.

  In the battery of the present invention, the negative electrode has a porous layer on the surface of the negative electrode mixture layer, which can act as a separator. Therefore, in constituting the electrode body, a separator may be interposed between the positive electrode and the negative electrode, but the positive electrode and the negative electrode may be opposed to each other without the separator.

  However, in particular, when the positive electrode and the negative electrode are opposed to each other without using a separator, the above-described wound electrode body deteriorates battery characteristics due to cracks in the porous layer on the surface of the negative electrode mixture layer. Since there is concern, it is preferable to use a laminated electrode body.

  When using a separator, conventionally used separators for non-aqueous secondary batteries, for example, microporous films made of polyolefin such as PE and PP, non-woven fabric, polyester such as PET and PBT, etc. Alternatively, a microporous film or a non-woven fabric made of a highly heat-resistant resin such as PPS can be used. The thickness of the separator is preferably 10 to 20 μm, for example.

As the non-aqueous electrolyte, a non-aqueous electrolyte used in a conventionally known non-aqueous secondary battery, for example, a solution in which a lithium salt is dissolved in an organic solvent is used. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , and LiN (CF ₃ SO ₂ ) ₂ . Examples of the organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, dimethoxyethane, dioxolane and the like. The lithium salt concentration in the nonaqueous electrolytic solution is preferably 0.2 to 1.5 mol / l, for example.

  The battery container (exterior body) consists of a battery container made of aluminum or stainless steel with a bottomed cylindrical shape (cylindrical shape or rectangular tube shape) or a metal laminate film with a metal foil (such as aluminum foil) as the core. A laminated outer package can be used.

  In addition, it is good also as a structure which can ensure the safety | security when a battery internal pressure rises rapidly by providing the vent which consists of a thin part in the battery lid for sealing the opening part of a battery container, or the bottom of a battery container. .

  The non-aqueous secondary battery of the present invention is applied to conventionally known non-aqueous secondary batteries such as industrial machine power supplies, in-vehicle power supplies, and various portable electronic devices. It can be applied to various uses.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention. In the following examples, the volume-based particle size distribution of the heat-resistant fine particles was measured by the above method, and the median diameter (d50), the cumulative distribution 10% value (d10), and the cumulative distribution 30% value (d30). Then, a value (d90) of the cumulative distribution 90% was obtained (the average particle diameter was the median diameter as described above). Also, from d10, it is confirmed that the proportion of particles having a particle size of 0.2 μm or less is 10% by volume or less, and from d90, the proportion of particles having a particle size of 2 μm or more is confirmed to be 10% by volume or less. did.

Example 1
<Preparation of slurry for forming porous layer>
To 1000 g of plate boehmite having an aspect ratio of 10, 1000 g of water and 1 part by mass of ammonium polyacrylate (dispersant) with respect to 100 parts by mass of boehmite were added and dispersed for 6 days by a table-top ball mill. The boehmite d10, d30, d50 and d90 in the resulting dispersion are 0.40 μm, 0.68 μm, 0.98 μm and 1.86 μm, respectively, the average particle size is 0.98 μm, and the particle size is It was confirmed that the ratio of particles having a particle diameter of 0.2 μm or less and the ratio of particles having a particle diameter of 2 μm or more were both 10% by volume or less.

  In the dispersion, an emulsion of a self-crosslinkable acrylic acid copolymer obtained by using butyl acrylate as a main component of a monomer as a binder is used in an amount of 3 parts by weight of the copolymer with respect to 100 parts by weight of boehmite. Furthermore, 2 g of xanthan gum was added as a thickener, and the mixture was stirred and dispersed with a three-one motor for 1 hour to obtain a uniform slurry for forming a porous layer.

<Preparation of positive electrode>
Positive electrode active material (lithium manganate): 94% by mass, carbon black: 3% by mass, and PVDF: 3% by mass, a suitable amount of NMP is added to the positive electrode mixture, and mixed well, and the positive electrode mixture-containing slurry Was prepared. This slurry is applied to one surface of an aluminum foil having a thickness of 15 μm at a constant thickness, dried at 110 ± 10 ° C., and then subjected to a press treatment to form a positive electrode mixture layer having a thickness of 30 μm. The positive electrode was obtained by cutting so that the area of the layer was 30 mm × 50 mm. The amount of the positive electrode active material in the positive electrode after cutting was 0.11 g.

<Production of negative electrode>
Lithium-titanium composite oxide _(Li 4 _Ti 5 _O 12 having a spinel structure): 88 wt%, carbon black: 6 wt%, PVDF: a negative electrode mixture of 6 wt%, was added an appropriate amount of NMP, thoroughly mixed Thus, a negative electrode mixture-containing slurry was prepared. This slurry is applied to one side of a copper foil having a thickness of 10 μm at a constant thickness, dried at 110 ± 10 ° C., and then subjected to a press treatment to form a negative electrode mixture layer having a thickness of 35 μm. The negative electrode was obtained by cutting so that the area of the layer was 33 mm × 53 mm. The amount of the negative electrode active material in the negative electrode after cutting was 0.08 g.

  The porous layer forming slurry was applied to the surface of the negative electrode mixture layer of the negative electrode and dried to form a porous layer having a thickness of 10 μm.

<Battery assembly>
The above positive electrode and negative electrode are opposed to each other so that the porous layer related to the negative electrode is in contact with the positive electrode to form a laminated electrode body, and this laminated electrode body is accommodated in an aluminum laminate sheet outer package of 50 mm × 110 mm, and is subjected to non-aqueous electrolysis. After injecting a liquid (a solution obtained by dissolving LiPF ₆ at a concentration of 1.0 M in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 1: 2), the exterior body was sealed, and the theoretical capacity was 10 mAh. A laminated non-aqueous secondary battery was obtained.

Example 2
A laminated nonaqueous secondary battery was produced in the same manner as in Example 1 except that polyhedral alumina was used instead of plate boehmite. In the preparation of the slurry for forming the porous layer, the alumina in the dispersion obtained by dispersing polyhedral alumina in water has d10, d30, d50 and d90 of 0.4 μm, 0.47 μm,. 54 μm and 1.15 μm, the average particle size is 0.54 μm, the proportion of particles having a particle size of 0.2 μm or less and the proportion of particles having a particle size of 2 μm or more are both 10% by volume or less. confirmed.

Example 3
A laminated nonaqueous secondary battery was produced in the same manner as in Example 1 except that plate-like alumina having an aspect ratio of 25 was used instead of plate-like boehmite. In the preparation of the slurry for forming the porous layer, the alumina in the dispersion obtained by dispersing plate-like alumina in water has d10, d30, d50 and d90 of 0.43 μm, 0.78 μm and 1.05 μm, respectively. And 1.20 μm, the average particle size is 1.05 μm, the proportion of particles having a particle size of 0.2 μm or less and the proportion of particles having a particle size of 2 μm or more are both confirmed to be 10% by volume or less. It was done.

Example 4
A laminated nonaqueous secondary battery was produced in the same manner as in Example 1 except that boehmite having a secondary particle structure was used instead of plate-like boehmite. The boehmite in a dispersion obtained by dispersing boehmite having a secondary particle structure in water when preparing the slurry for forming the porous layer has d10, d30, d50 and d90 of 0.34 μm, 0.48 μm, 0.71 μm and 1.24 μm, the average particle size is 0.71 μm, the proportion of particles having a particle size of 0.2 μm or less and the proportion of particles having a particle size of 2 μm or more are both 10% by volume or less. It was confirmed.

Comparative Example 1
A laminated nonaqueous secondary battery was produced in the same manner as in Example 1 except that natural graphite was used as the negative electrode active material instead of lithium titanate and the amount of the negative electrode active material in the cut negative electrode was 0.04 g.

  The laminated nonaqueous secondary batteries of Example 1 and Comparative Example 1 were charged under the conditions shown in Table 1. The current value at each charge corresponds to 0.2 C at 2 mA, 6 C at 60 mA, 12 C at 120 mA, and 20 C at 200 mA. Each battery charged under each condition was discharged at a current value of 2 mA, and the discharge capacity was measured. In addition, since the battery of Example 1 and the battery of Comparative Example 1 have different potentials of the active material used for the negative electrode, the battery of Example 1 has a final voltage of 1V, and the battery of Comparative Example 1 has a final voltage of 3V. As described above, the above discharge was performed. These results are shown in Table 1.

  As is apparent from Table 1, the battery of Example 1 has a relatively small decrease in discharge capacity even when the charging current is increased, and is excellent in rapid charging characteristics. On the other hand, in the battery of Comparative Example 1, a decrease in current value was observed during charging, and it was recognized that a slight short circuit occurred during charging.

  In addition, the batteries of Examples 2 to 4 were subjected to the same charge / discharge test as that of the battery of Example 1. As with the battery of Example 1, the occurrence of fine short-circuiting was suppressed, and the battery had good quick charge characteristics. Turned out to be.

  Furthermore, in the batteries of Examples 1 to 4, there was no complication at the time of production accompanying the position regulation between the separator and the electrode as in a normal battery, and the productivity was good.

DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Porous layer 3 Negative mix layer 4 Current collector

Claims (8)

A non-aqueous secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
The negative electrode has a negative electrode mixture layer containing a lithium titanium composite oxide on at least one surface of the current collector,
In the negative electrode mixture layer, the ratio of particles having a particle diameter of 0.2 μm or less and the ratio of particles having a particle diameter of 2 μm or more on the surface opposite to the current collector are both 10% by volume or less. A non-aqueous secondary battery comprising a porous layer containing heat-resistant fine particles.   The non-aqueous secondary battery according to claim 1, wherein the porous layer further contains a heat-resistant binder.   The nonaqueous secondary battery according to claim 1 or 2, wherein the heat-resistant fine particles contained in the porous layer are inorganic fine particles.   The nonaqueous secondary battery according to claim 3, wherein the inorganic fine particles contained in the porous layer are alumina and / or boehmite.   The nonaqueous secondary battery according to claim 3 or 4, wherein at least a part of the inorganic fine particles contained in the porous layer is a plate-like particle.   The nonaqueous secondary battery according to claim 1, wherein the heat-resistant fine particles contained in the porous layer have an average particle diameter of 1 μm or less.   The nonaqueous secondary battery according to any one of claims 1 to 6, wherein the positive electrode and the negative electrode face each other without a separator.   The nonaqueous secondary battery according to any one of claims 1 to 7, which has a laminated electrode body in which flat positive electrodes and flat negative electrodes are alternately laminated.

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