JP2010287470A - Nonaqueous secondary battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery including olivine lithium phosphate as a positive electrode active material, which maintains battery performance such as charge and discharge cyclic characteristics and output characteristics at a high level for a long period and gets rid of varied battery performance in mass production. <P>SOLUTION: In the nonaqueous secondary battery 1 including a flat electrode group 10 formed at a flat shape by winding while intervening a separator between a positive electrode and a negative electrode, a battery case 11, and a nonaqueous electrolyte, the positive electrode includes a positive electrode collector and a positive electrode active material layer, the positive electrode active material layer includes olivine lithium phosphate and a fluorocarbon resin with a crosslinking functional group, and at least a part of the fluorocarbon resin with a crosslinking functional group is constituted to be crosslinked. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-aqueous secondary battery and a method for manufacturing the same. More specifically, the present invention mainly relates to improvement of a positive electrode in a non-aqueous secondary battery containing olivine type lithium phosphate as a positive electrode active material.

  Non-aqueous secondary batteries have a high capacity and a high energy density, and are relatively easy to reduce in size and weight, so that they are widely used as power sources for portable electronic devices, for example. Examples of portable electronic devices include cellular phones, personal digital assistants (PDAs), notebook personal computers, video cameras, and portable game machines. In addition, non-aqueous secondary batteries are expected to be applied to main or auxiliary power sources for driving electric motors in electric vehicles, hybrid vehicles (HEV), plug-in hybrid vehicles (PHEV), etc. It is being done.

A typical non-aqueous secondary battery currently on the market includes a positive electrode containing lithium cobaltate (LiCoO ₂ ), a negative electrode containing a carbon material, and a polyolefin separator. Among these, lithium cobaltate used for the positive electrode active material has difficulty in stable supply and high cost because cobalt is a rare metal. In addition, since lithium cobaltate has high cobalt reactivity, there is a possibility of further promoting heat generation due to overcharge or short circuit inside the battery. In addition, the non-aqueous secondary battery containing lithium cobaltate has high safety, and there is almost no possibility of causing an internal short circuit. However, even in the unlikely event that it is necessary to obtain higher safety.

  As a positive electrode active material that replaces lithium cobaltate, olivine type lithium phosphate has attracted attention. Since olivine-type lithium phosphate contains abundant metals on the earth, stable supply is relatively easy and the cost is low. Moreover, since the reactivity of the metal contained in olivine type lithium phosphate is lower than the reactivity of cobalt, the possibility of promoting heat generation due to overcharge or short circuit is further reduced. Therefore, it is considered that a non-aqueous secondary battery containing olivine type lithium phosphate has higher safety than a non-aqueous secondary battery containing lithium cobaltate.

  However, when olivine type lithium phosphate is used as the positive electrode active material, battery performance such as charge / discharge cycle characteristics and output characteristics of the non-aqueous secondary battery is often insufficient. Also, when non-aqueous secondary batteries containing olivine type lithium phosphate are mass-produced, the battery performance varies greatly.

  In order to improve the battery performance of a non-aqueous secondary battery containing olivine-type lithium phosphate, for example, polyfluoride having a molecular weight of 370,000 to 1,000,000 as a binder and iron phosphate that is a kind of olivine-type lithium phosphate A positive electrode for a non-aqueous secondary battery containing vinylidene has been proposed (for example, see Patent Document 1). However, in the non-aqueous secondary battery including the positive electrode, when the number of charge / discharge cycles is increased, the battery performance is greatly deteriorated, and the problem that the battery performance varies during mass production is not sufficiently solved.

  On the other hand, various techniques for improving a non-aqueous secondary battery in which the positive electrode active material is not limited to olivine type lithium phosphate have been proposed. For example, a technique for adding a pH adjusting agent to an aqueous negative electrode mixture slurry containing a negative electrode active material and a binder has been proposed (see, for example, Patent Document 2). As the binder, a mixture of rubber latex and a water-soluble polymer compound is used. Ammonia water or lithium hydroxide is used as the pH adjuster. By using the pH adjuster, the dispersibility of the negative electrode active material and the binder is improved, the negative electrode active material layer has a dense and uniform structure, and the adhesion between the negative electrode active material layer and the current collector is improved. However, since the technique of Patent Document 2 does not use a binder having a crosslinkable functional group, crosslinking of the binder does not occur even when a pH adjuster is present.

  Moreover, the technique which bridge | crosslinks the binder contained in an active material layer is proposed (for example, refer patent documents 3-5). In Patent Document 3, polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene is thermally crosslinked by an amine group-containing polymer. Thereby, the positive electrode with improved adhesion between the active material layer and the current collector is being obtained. The copolymer used in Patent Document 3 does not have a crosslinkable functional group.

  However, since the amine group is not bonded to the copolymer and decomposes in a high voltage region of 4.0 V or higher, a cross-linked portion via the amine group is easily decomposed in the high voltage region. On the other hand, the non-aqueous secondary battery is generally set so that the maximum charging voltage is 4.0 V or more. Therefore, even if the positive electrode of Patent Document 3 is used for a non-aqueous secondary battery, the adhesion between the active material layer and the current collector cannot be maintained for a long time.

  In Patent Document 4, polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, which is a binder for the positive electrode active material layer, is crosslinked by an electron beam. However, it is difficult to uniformly crosslink the entire active material layer by electron beam irradiation. Moreover, the surface layer of lithium iron olivicate may be damaged by the electron beam irradiation, and the battery capacity may be reduced.

  In Patent Document 5, polyvinylidene fluoride containing a carboxyl group, which is a binder for the negative electrode active material layer, is crosslinked with a crosslinking agent containing two or more epoxy groups. Examples of the crosslinking agent include glycidyl ether, glycidyl ester, glycidyl amine and the like. However, since the epoxy group has a low voltage resistance like the amine group, the adhesion between the active material layer and the current collector cannot be maintained for a long period of time.

JP 2005-302300 A JP 2003-272619 A JP-A-7-296815 Japanese Patent Laid-Open No. 7-296816 JP 2001-283856 A

  It is an object of the present invention to include olivine-type lithium phosphate as a positive electrode active material, to maintain battery performance such as charge / discharge cycle characteristics and output characteristics at a high level for a long period of time, and to maintain non-dispersive battery performance even in mass production. A secondary battery and a manufacturing method thereof are provided.

  The present inventor paid attention to the technique of Patent Document 1 in the process of solving the above-mentioned problems and studied the cause of variation in battery performance in the technique of Patent Document 1. As a result, it has been found that the positive electrode active material layer containing olivine-type lithium phosphate and polyvinylidene fluoride has low adhesion to the positive electrode current collector. Furthermore, peeling of the positive electrode active material layer from the positive electrode current collector is likely to occur in the rolling step after the positive electrode material mixture slurry containing olivine type lithium phosphate and polyvinylidene fluoride is applied to the positive electrode current collector and dried. I found out. Furthermore, it has been found that the separation spreads around the charge / discharge cycle. For this reason, the current collecting performance of the positive electrode current collector is lowered, the battery performance is greatly lowered, and it is estimated that the battery performance varies when mass-produced.

  In addition, when the present inventors heat a fluororesin having a crosslinkable functional group in the presence of a crosslinker that is an alkylamine, aromatic amine, lithium hydroxide or sodium carbonate, the withstand voltage is unexpectedly increased. It has been found that a highly crosslinked part can be obtained. This cross-linked portion is stable even in a high voltage region of 4.0 V or higher, and is assumed to be difficult to decompose.

  Based on these findings, the present inventor has further studied. As a result, a configuration is conceived in which the crosslinking agent is added to a positive electrode mixture slurry containing an olivine type lithium phosphate and a fluororesin having a crosslinkable functional group, and crosslinking is performed by heating during drying of the positive electrode active material layer. It came. According to this configuration, the adhesion between the positive electrode active material layer and the positive electrode current collector is improved, and when the positive electrode active material layer is rolled and when the number of charge / discharge cycles is increased, the positive electrode active material layer is separated from the positive electrode current collector. It has been found that peeling is remarkably suppressed. As a result, the present inventors have found that a non-aqueous secondary battery can be obtained in which battery performance is maintained at a high level for a long period of time and variation in battery performance is very small even when mass-produced.

The present invention includes a positive electrode, a negative electrode, a separator disposed so as to be interposed between the positive electrode and the negative electrode, and a lithium ion conductive nonaqueous electrolyte, the positive electrode includes a positive electrode active material layer and a positive electrode current collector, The positive electrode active material layer contains olivine-type lithium phosphate and a fluororesin having a crosslinkable functional group, at least a part of the fluororesin having a crosslinkable functional group is cross-linked, and the negative electrode absorbs lithium ions and Provided is a non-aqueous secondary battery including a negative electrode active material layer containing a releasable negative electrode active material and a negative electrode current collector.
The olivine type lithium phosphate is preferably iron iron phosphate.
The content of the crosslinkable functional group in the fluororesin is preferably 0.1 to 100 mmol per 1 g of the fluororesin.

The fluororesin is preferably polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-vinylidene fluoride copolymer, hexafluoropropylene-vinylidene fluoride. It is at least one selected from the group consisting of a copolymer and polyvinylidene fluoride.
The crosslinkable functional group is preferably a carboxyl group.

  The present invention also includes a positive electrode preparation step, a negative electrode preparation step, an electrode group preparation step, and a battery assembly step. In the positive electrode preparation step, olivine type lithium phosphate and fluorine having a crosslinkable functional group are formed on the surface of the positive electrode collector. A positive electrode mixture slurry containing a resin, a crosslinking agent and an organic solvent is applied and heated to form a positive electrode active material layer, and a positive electrode capable of inserting and extracting lithium ions is prepared. In the electrode group manufacturing process, a separator is interposed between the positive electrode and the negative electrode, and these are stacked or wound to form an electrode group. In the battery assembly process, the electrode group is And a lithium ion conductive non-aqueous electrolyte in a battery case having an opening, and then sealing the battery case opening to provide a non-aqueous secondary battery manufacturing method. To.

The crosslinking agent contained in the positive electrode mixture slurry is preferably at least one selected from the group consisting of alkylamines, aromatic amines, lithium hydroxide, and sodium carbonate.
The content of the crosslinking agent in the positive electrode mixture slurry is preferably 0.003 to 2% by weight of the total amount of the positive electrode mixture slurry.

The heating in the positive electrode manufacturing step is preferably performed at a temperature of 80 ° C to 100 ° C.
Heating in the positive electrode manufacturing step is preferably performed in an atmosphere having a dew point of 0 ° C. or higher.
The oxygen partial pressure in an atmosphere having a dew point of 0 ° C. or higher is preferably 10 ⁻⁵ atm to 10 ⁻² atm.

  The non-aqueous secondary battery of the present invention has higher safety than the non-aqueous secondary battery containing lithium cobaltate and having high safety by containing olivine type lithium phosphate. Further, the non-aqueous secondary battery of the present invention has good adhesion between the positive electrode active material layer and the positive electrode current collector, despite containing olivine type lithium phosphate, Battery performance such as output characteristics is maintained at a high level for a long time. In addition, when mass-produced, there is very little variation in battery performance.

  Further, according to the method for producing a non-aqueous secondary battery of the present invention, the non-aqueous secondary battery of the present invention can be efficiently produced without substantially changing the conventional method for producing a non-aqueous secondary battery. Moreover, since the conventional manufacturing process of the non-aqueous secondary battery can be used as it is, mass production of the non-aqueous secondary battery of the present invention without variation in battery performance becomes possible.

It is a longitudinal cross-sectional view which shows typically the structure of the non-aqueous secondary battery which is one of embodiment of this invention.

  The nonaqueous secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and a lithium ion conductive nonaqueous electrolyte, and is characterized by a positive electrode. The positive electrode is characterized in that the positive electrode active material layer contains an olivine-type lithium phosphate and a fluororesin having a crosslinkable functional group, and at least a part of the fluororesin having a crosslinkable functional group is cross-linked. In the non-aqueous secondary battery of this invention, structures other than a positive electrode can take the structure similar to the conventional non-aqueous secondary battery.

  In the present invention, a positive electrode mixture slurry is applied to a positive electrode current collector and dried to form a positive electrode active material layer. At this time, the positive electrode mixture slurry contains a specific crosslinking agent together with the olivine-type lithium phosphate that is the positive electrode active material and the fluororesin having a crosslinkable functional group that is the binder. When this positive electrode mixture slurry is heated during drying, it is presumed that at least a part of the fluororesin having a crosslinkable functional group causes crosslinking in the presence of a specific crosslinking agent. Furthermore, it is presumed that some of the functional groups of the fluororesin are also bonded to the surface of the positive electrode current collector. As a result, the adhesion between the positive electrode current collector and the positive electrode active material layer is improved, and it is presumed that there is no variation in battery performance even in mass production.

  Moreover, even if the non-aqueous secondary battery of this invention increases the number of charging / discharging cycles, the rapid fall of battery performance, such as charging / discharging cycling characteristics and an output characteristic, is suppressed. From this, it is assumed that the cross-linked portion of the fluororesin having a cross-linkable functional group is stably present even in a high voltage region exceeding 4.0 V and is hardly decomposed. For this reason, even if the number of charge / discharge cycles increases, the adhesion between the positive electrode current collector and the positive electrode active material layer does not decrease, the decrease in the current collection performance of the positive electrode current collector is suppressed, and the battery performance is high. It is estimated that it will be maintained at

FIG. 1 is a perspective view schematically showing a configuration of a non-aqueous secondary battery 1 which is one embodiment of the present invention. In FIG. 1, in order to show the structure of the principal part of the non-aqueous secondary battery 1, a part is notched.
The nonaqueous secondary battery 1 is a rectangular battery in which a flat electrode group 10 is accommodated in a rectangular battery case 11. The nonaqueous secondary battery 1 includes a flat electrode group 10, a battery case 11, a positive electrode lead 12, a negative electrode lead 13, a sealing plate 14, a negative electrode terminal 15, a gasket 16 and a plug 17.

The flat electrode group 10 includes a positive electrode, a negative electrode, and a separator (not shown).
The positive electrode includes a positive electrode current collector and a positive electrode active material layer. The positive electrode is disposed so as to face the negative electrode with a separator interposed therebetween. Specifically, the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode face each other via a separator.

  The positive electrode current collector is a strip-shaped current collector. For the positive electrode current collector, for example, a metal foil and a porous metal sheet made of stainless steel, aluminum, an aluminum alloy, titanium, or the like can be used. Examples of the porous sheet include a woven fabric, a nonwoven fabric, and a punching sheet. The thickness of the positive electrode current collector is not particularly limited, but is preferably 1 to 500 μm, more preferably 5 to 20 μm.

In the present embodiment, the positive electrode active material layer is formed on both surfaces in the thickness direction of the positive electrode current collector, but is not limited thereto, and may be formed on either surface in the thickness direction.
The positive electrode active material layer includes an olivine-type lithium phosphate that is a positive electrode active material and a fluororesin having a crosslinkable functional group that is a binder. And at least one part of the fluororesin which has a crosslinkable functional group is bridge | crosslinked. That is, the positive electrode active material layer includes a cross-linked portion.

  The formation of the cross-linked moiety can be confirmed, for example, by infrared spectroscopic analysis. When the positive electrode active material layer includes a cross-linked portion, the adhesion between the positive electrode current collector and the positive electrode active material layer is improved as described above. Furthermore, the positive electrode active material layer may contain a conductive agent in addition to the olivine-type lithium phosphate and the fluororesin having a crosslinkable functional group.

Specific examples of the olivine-type lithium phosphate include general formulas LiXPO ₄ and Li ₂ XPO ₄ F (wherein X is at least one selected from the group consisting of Cr, Cu, Ni, Mn, Fe, Zn and Al). For example). Among these, the olivine type lithium phosphate whose code | symbol X is Ni, Mn, or Fe is preferable, and the iron iron phosphate whose code | symbol X is Fe is further more preferable.

  For example, lithium iron phosphate is particularly excellent in terms of stable supply and safety. Iron lithium phosphate is sometimes called lithium iron phosphate, lithium iron phosphate, or the like. In iron lithium phosphate, a part of iron may be replaced with a different metal (hereinafter referred to as “different metal A”). The different metal A is a metal other than iron and lithium, and examples thereof include Mn, Cr, Cu, Ni, Zn, and Al. The substitution ratio of the different metal is not particularly limited, but the ratio of the different metal A in the total amount of iron and the different metal A is preferably 0.5 to 50 mol%.

  The olivine type lithium phosphate can be used alone or in combination of two or more. Moreover, in this invention, well-known positive electrode active materials other than olivine type lithium phosphate can be used together in the range which does not impair the preferable characteristic of olivine type lithium phosphate.

  In the fluororesin having a crosslinkable functional group, as the fluororesin, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-vinylidene fluoride copolymer , Hexafluoropropylene-vinylidene fluoride copolymer, polyvinylidene fluoride, and the like.

Among these, in consideration of the durability of the adhesion between the positive electrode current collector and the positive electrode active material layer, tetrafluoroethylene-vinylidene fluoride copolymer, hexafluoropropylene-vinylidene fluoride copolymer, polyvinylidene fluoride, and the like. Etc. are preferable, and polyvinylidene fluoride is particularly preferable.
The molecular weight of the fluororesin is not particularly limited, but is preferably 200,000 to 1,500,000 as a weight average molecular weight.

  Examples of the crosslinkable functional group possessed by the fluororesin include a carboxyl group, a hydroxyl group, a carbonyl group, an acid anhydride group, an amino group, a cyano group, and a silanol group. Among these, a carboxyl group, a hydroxyl group, a silanol group, and the like are preferable, and a carboxyl group is particularly preferable in consideration of the stability of the cross-linked portion in a high voltage region. One or two or more kinds of crosslinkable functional groups may be substituted with a fluororesin. The crosslinkable functional group is generally substituted with a hydrogen atom or a fluorine atom contained in the fluororesin.

  The amount of the functional group substituted for the fluororesin is not particularly limited, but is preferably 0.1 to 100 mmol per 1 g of the fluororesin, more preferably 0.5 to 10 mmol per 1 g of the fluororesin. If the substitution amount of the functional group is less than 0.1 mmol, the adhesion between the positive electrode current collector and the positive electrode active material layer may be insufficient. On the other hand, when the substitution amount of the functional group exceeds 100 mmol, the ratio of the cross-linked portion in the positive electrode active material layer increases, and the lithium ion conductivity of the positive electrode active material layer may be lowered.

  The fluororesin having a crosslinkable functional group used in the present invention can be synthesized, for example, by copolymerizing a fluororesin monomer having a crosslinkable functional group and a fluororesin monomer having no functional group. Examples of the fluororesin monomer having no functional group include tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride.

  In the present invention, a commercially available fluororesin having a crosslinkable functional group can also be used, and examples thereof include trade name: KF polymer 9210, manufactured by Kureha Corporation.

The fluororesin which has a crosslinkable functional group can be used individually by 1 type or in combination of 2 or more types.
In this invention, the binder conventionally used in this field | area can be used together in the range which does not impair the preferable characteristic of the fluororesin which has a crosslinkable functional group.

  Examples of the conductive agent include natural graphite, artificial graphite graphite, carbon materials such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. A conductive agent can be used individually by 1 type or in combination of 2 or more types.

The positive electrode active material layer can be formed, for example, by applying a positive electrode mixture slurry to the surface of the positive electrode current collector, drying, and rolling.
The positive electrode mixture slurry can be prepared, for example, by dissolving or dispersing an olivine type lithium phosphate, a fluororesin having a crosslinkable functional group, and a crosslinker in an organic solvent. As the organic solvent, for example, N-methyl-2-pyrrolidone, tetrahydrofuran, dimethylformamide and the like can be used. The positive electrode mixture paste may further contain a positive electrode active material for non-aqueous secondary batteries other than olivine-type lithium phosphate, a binder other than a fluororesin having a crosslinkable functional group, a conductive agent, and the like.

  As the crosslinking agent, at least one selected from the group consisting of alkylamines, aromatic amines, lithium hydroxide and sodium carbonate is used. By including these specific crosslinking agents in the positive electrode mixture slurry, at least a part of the fluororesin having a crosslinkable functional group is crosslinked, and a stable crosslinked portion is generated even in a high voltage region of 4.0 V or higher. Moreover, these crosslinking agents act as an alkali even in an aqueous solution or a slurry using an organic solvent such as a positive electrode mixture slurry as a matrix. However, it is presumed that the behavior in an aqueous solution and the behavior in the slurry are different.

  Examples of the alkylamine include ethylamine, propylamine, isopropylamine, butylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, tripropylamine, triisopropylamine, and tributylamine. Examples thereof include alkylamines in which 1 to 3 linear or branched alkyl groups of ˜4 are substituted. Aromatic amines include aniline, N-methylaniline, N, N-dimethylaniline, benzylamine, dibenzylamine, N-methylbenzylamine and the like. Among these, diethylamine, N-methylaniline and the like are preferable.

  The amount of the crosslinking agent to be used is not particularly limited, but is preferably 0.003 to 2% by weight, more preferably 0.1 to 1% by weight, based on the total amount of the positive electrode mixture slurry. When the amount of the crosslinking agent used is less than 0.003% by weight, the crosslinking of the fluororesin having a crosslinkable functional group does not sufficiently proceed, and the adhesion between the positive electrode current collector and the positive electrode active material layer may be insufficient. There is. On the other hand, when the amount of the crosslinking agent used exceeds 2% by weight, the crosslinking of the fluororesin having a crosslinkable functional group proceeds excessively, and the lithium ion conductivity of the positive electrode active material layer is lowered, and battery performance may be impaired. There is.

  The positive electrode mixture slurry for determining the amount of the crosslinking agent used is usually 50 to 90 parts by weight of an olivine type lithium phosphate, 0.5 to 7 parts by weight of a fluororesin having a crosslinkable functional group and a conductive agent 0. It is a positive electrode mixture slurry in which 5 to 20 parts by weight are dissolved or dispersed in 100 to 300 parts by weight of an organic solvent.

  The method of applying the positive electrode mixture slurry to the surface of the positive electrode current collector is not particularly limited. For example, reverse roll method, direct roll method, blade method, knife method, extrusion method, curtain method, gravure method, bar method, casting Method, dip method, squeeze method, etc. can be used.

  Drying is performed by heating the positive electrode mixture slurry applied to the surface of the positive electrode current collector. Heating is performed at a temperature of 80 ° C. to 100 ° C. and is completed in about 5 to 20 minutes. By heating in the presence of the crosslinking agent, at least a part of the fluororesin having a crosslinkable functional group is crosslinked, and a chemically stable crosslinked portion is generated in a high voltage region of 4.0 V or higher. As a result, the adhesion between the positive electrode current collector and the positive electrode active material layer is improved, and the battery performance of the non-aqueous secondary battery 1 is maintained at a high level for a long time.

  When the heating temperature is less than 80 ° C., the crosslinking of the fluororesin having a crosslinkable functional group does not proceed sufficiently, and the adhesion between the positive electrode current collector and the positive electrode active material layer may be insufficient. On the other hand, when the heating temperature exceeds 100 ° C., the crosslinking of the fluororesin having a crosslinkable functional group proceeds excessively, the lithium ion conductivity of the positive electrode active material layer is lowered, and the battery performance may be impaired. Moreover, there is a possibility that alteration of the olivine type lithium phosphate and the fluororesin having a crosslinkable functional group may occur.

  Heating is preferably performed in an atmosphere having a dew point of 0 ° C. or higher. Usually, the heating of the positive electrode mixture slurry in the production process of the nonaqueous secondary battery is performed in an atmosphere having a dew point of about -25 ° C. On the other hand, in the present invention, drying is preferably performed in an atmosphere having a higher dew point temperature than usual. Thereby, partial cross-linking of the fluororesin having a cross-linkable functional group surely proceeds, and a cross-linked portion having high stability in the high voltage region is reliably generated in the positive electrode active material layer. Further, since lithium is eluted from the olivine-type lithium phosphate and a cross-linked site is generated, there is an advantage that the amount of the cross-linking agent can be reduced.

The oxygen content in an atmosphere having a dew point of 0 ° C. or higher is preferably 10 ⁻⁵ atm to 10 ⁻² atm in terms of oxygen partial pressure. Thereby, the oxidation of olivine-type lithium phosphate is suppressed, and a reduction in battery capacity can be prevented. This is particularly noticeable when lithium iron phosphate is used among olivine-type lithium phosphates. At present, it is technically difficult to make the oxygen partial pressure less than 10 ⁻⁵ atm, and the cost becomes high. On the other hand, if the oxygen partial pressure exceeds 10 ⁻² atm, at least a part of the olivine-type lithium phosphate is oxidized, and the battery capacity may be reduced.

The positive electrode active material layer after drying is subjected to a rolling treatment as necessary. In the present invention, adhesion between the positive electrode current collector and the positive electrode active material layer is improved by partial crosslinking of the fluororesin having a crosslinkable functional group. Therefore, even if a rolling process is performed, peeling of the positive electrode active material layer from the positive electrode current collector hardly occurs. The thickness of the positive electrode active material layer thus obtained is not particularly limited, but is preferably 50 μm to 200 μm.
The step of forming a positive electrode active material layer on the surface of the positive electrode current collector to produce a positive electrode corresponds to the positive electrode production step in the method for producing a nonaqueous secondary battery of the present invention.

The negative electrode includes a negative electrode current collector and a negative electrode active material layer.
The negative electrode current collector is a strip-shaped current collector, like the positive electrode current collector. For the negative electrode current collector, for example, a metal foil and a porous metal sheet made of stainless steel, nickel, copper, copper alloy, or the like can be used. Examples of the porous sheet include a woven fabric, a nonwoven fabric, and a punching sheet. The thickness of the negative electrode current collector is not particularly limited, but is preferably 1 to 500 μm, more preferably 5 to 20 μm.

  In the present embodiment, the negative electrode active material layer is formed on both surfaces in the thickness direction of the negative electrode current collector, but is not limited thereto, and may be formed on one surface in the thickness direction. The negative electrode active material layer contains a negative electrode active material, and contains a binder, a conductive agent, a thickener and the like as necessary.

  Examples of the negative electrode active material include a carbon material, an alloy-based negative electrode active material, and a lithium alloy. Examples of the carbon material include natural graphite, artificial graphite, coke, graphitized carbon, carbon fiber, spherical carbon, and amorphous carbon. The alloy-based negative electrode active material is a material that occludes lithium ions by alloying with lithium and reversibly occludes and releases lithium ions under a negative electrode potential. The alloy-based negative electrode active material includes an alloy-based negative electrode active material containing silicon and an alloy-based negative electrode active material containing tin.

The alloy-based negative electrode active material containing silicon includes silicon, silicon oxide represented by the formula: SiO _a (0.05 <a <1.95), formula: SiN _b (0 <b <4/3) There are silicon nitrides, silicon alloys, silicon compounds, and the like. Silicon alloys include alloys containing silicon and elements other than silicon. As an element other than silicon, one or more elements selected from the group consisting of Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti can be used.

  Examples of the silicon compound include compounds in which part of silicon contained in silicon, silicon oxide, silicon nitride, or silicon alloy is substituted with another element. Other elements here include, for example, B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Nb, Ta, V, W, Zn, C, N, and Sn. One or more elements selected from the group can be used.

The alloy-based negative electrode active material containing tin includes tin, tin oxide, tin alloy, tin compound, and the like. Examples of the tin oxide include SnO ₂ and silicon oxide represented by the formula: SnO _d (0 <d <2). Examples of the tin alloy include a Ni—Sn alloy, a Mg—Sn alloy, a Fe—Sn alloy, a Cu—Sn alloy, and a Ti—Sn alloy. Examples of the tin compound include SnSiO ₃ , Ni ₂ Sn ₄ , and Mg ₂ Sn.
A negative electrode active material can be used individually by 1 type or in combination of 2 or more types.

  Examples of the binder include polyethylene, polypropylene, polyvinyl acetate, polymethyl methacrylate, nitrocellulose, fluororesin, and rubber particles. Examples of the fluororesin include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and vinylidene fluoride-hexafluoropropylene copolymer. Examples of rubber particles include styrene-butadiene rubber particles and acrylonitrile rubber particles. A binder can be used individually by 1 type or in combination of 2 or more types. Thickeners include carboxymethyl cellulose.

  The negative electrode active material layer can be formed, for example, by applying a negative electrode mixture paste to the surface of the negative electrode current collector, drying, and rolling as necessary. The negative electrode mixture paste can be prepared, for example, by mixing the negative electrode active material in an organic solvent or water together with a binder, a conductive agent, a thickener, and the like as necessary. As the organic solvent, for example, N-methyl-2-pyrrolidone (NMP), tetrahydrofuran, dimethylformamide and the like can be used. The thickness of the negative electrode active material layer is not particularly limited, but is preferably 50 to 200 μm.

When an alloy-based negative electrode active material is used as the negative electrode active material, a negative electrode active material layer made of an alloy-based negative electrode active material may be formed by a vapor phase method. Examples of the vapor phase method include a vapor deposition method, a sputtering method, and a chemical vapor deposition method.
The step of forming a negative electrode active material layer on the surface of the negative electrode current collector to produce a negative electrode corresponds to the negative electrode production step in the method for producing a nonaqueous secondary battery of the present invention.

  The separator is disposed so as to be interposed between the positive electrode and the negative electrode, insulates the positive electrode from the negative electrode, and has lithium ion permeability. Examples of the separator include a porous sheet having pores therein, a resin fiber nonwoven fabric, and a woven fabric. The porous sheet and the resin fiber are made of a synthetic resin. Synthetic resins include, for example, polyolefins such as polyethylene and polypropylene, polyamide, and polyamideimide. Among these, a porous sheet is preferable. The pore diameter of the porous sheet is preferably 0.05 to 0.15 μm. The thickness of the porous sheet is preferably 5 to 30 μm.

  The flat electrode group 10 can be produced, for example, by pressurizing the wound electrode group and forming it into a flat shape. A wound electrode group is formed by winding an electrode having a separator interposed between a positive electrode and a negative electrode with one end portion (one end portion in the longitudinal direction) along the width direction as a winding axis. Produced. At this time, a positive electrode current collector exposed portion (not shown) is provided at a predetermined position of the positive electrode, and one end of the positive electrode lead 12 is connected. A current collector exposed portion (not shown) is provided at a predetermined position of the negative electrode, and one end of the negative electrode lead 13 is connected. Further, the wound electrode group is pressed by, for example, press pressing.

  The production of the wound electrode group and the flat electrode group 10 corresponds to an electrode group production step in the production method of the present invention. In the present embodiment, the wound electrode group is manufactured in the electrode group manufacturing step, but a stacked electrode group in which a separator is interposed between the positive electrode and the negative electrode may be manufactured.

The flat electrode group 10 is impregnated with a nonaqueous electrolyte. In the present embodiment, a liquid nonaqueous electrolyte is used as the nonaqueous electrolyte. The liquid non-aqueous electrolyte contains a solute (supporting salt) and a non-aqueous solvent, and further contains various additives as necessary.
Solutes include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiB ₁₀ Cl ₁₀ , lithium lower aliphatic carboxylate, LiCl, LiBr, LiI, chloroborane lithium, borates, imide salts and the like can be used.

Examples of borates include lithium bis (1,2-benzenediolate (2-)-O, O ') borate, bis (2,3-naphthalenedioleate (2-)-O, O') boric acid. Lithium, bis (2,2′-biphenyldiolate (2-)-O, O ′) lithium borate, bis (5-fluoro-2-olate-1-benzenesulfonic acid-O, O ′) lithium borate and so on. Examples of the imide salts include NLi (SO ₂ CF ₃ ) ₂ , NLi (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), and NLi (SO ₂ C ₂ F ₅ ) ₂ . Solutes can be used alone or in combination of two or more. The solute is preferably added at a ratio of 0.5 to 2 moles per liter of the nonaqueous solvent.

  Nonaqueous solvents include cyclic carbonates, chain carbonates, and cyclic carboxylic acid esters. Examples of the cyclic carbonate include propylene carbonate (PC) and ethylene carbonate (EC). Examples of the chain carbonate include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Examples of cyclic carboxylic acid esters include γ-butyrolactone (GBL) and γ-valerolactone (GVL). A non-aqueous solvent can be used individually by 1 type or in combination of 2 or more types.

  Examples of the additive include vinylene carbonate compounds (hereinafter referred to as “VC compounds”), benzene compounds, and the like. The VC compound improves, for example, the charge / discharge efficiency of the battery. Examples of the VC compound include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and divinyl ethylene carbonate. The VC compound may contain a fluorine atom. The benzene compound inactivates the battery during overcharge, for example. Examples of the benzene compound include cyclohexylbenzene, biphenyl, diphenyl ether and the like. The benzene compound is preferably used at a ratio of 10 parts by volume or less with respect to 100 parts by volume of the non-aqueous solvent.

  One end of the positive electrode lead 12 is connected to the positive electrode current collector of the positive electrode, and the other end is connected to the lower surface of the sealing plate 14. An aluminum lead or the like can be used for the positive electrode lead 12. The negative electrode lead 13 has one end connected to the negative electrode current collector of the negative electrode and the other end connected to the negative electrode terminal 15. A nickel lead or the like can be used for the negative electrode lead 13.

The sealing plate 14 is connected to the opening of the battery case 11 having a square shape. A negative electrode terminal 15 is disposed on the sealing plate 14 and a liquid injection hole (not shown) is provided. In the present embodiment, the sealing plate 14 is a positive electrode terminal. The gasket 16 is disposed around the negative electrode terminal 15 and insulates the sealing plate 14 from the negative electrode terminal 15. A nonaqueous electrolyte is injected into the battery case 11 from the injection hole. After the liquid injection, a plug 17 is attached to the liquid injection hole and sealed.
As described above, the non-aqueous secondary battery 1 is assembled using the electrode group 10, the battery case 11, the positive electrode lead 12, the negative electrode lead 13, the sealing plate 14, the negative electrode terminal 15, the gasket 16, and the plug 17. This corresponds to the battery assembly step in the method for manufacturing a non-aqueous secondary battery.

  In the present embodiment, a non-aqueous secondary battery 1 having a square shape is described. However, the nonaqueous secondary battery of the present invention is not limited to a prismatic battery. The non-aqueous secondary battery of the present invention includes a cylindrical battery including a wound electrode group, a wound electrode group, a flat electrode group, a laminate pack battery including a stacked electrode group, and a coin including a stacked electrode group. It can be formed into various types of batteries such as a type battery.

Hereinafter, the present invention will be specifically described with reference to Examples, Comparative Examples, and Test Examples.
Example 1
(1) Preparation of positive electrode 100 parts by weight of lithium iron phosphate (LiFePO ₄ , positive electrode active material), 2 parts by weight of acetylene black (conductive agent), polyvinylidene fluoride having a carboxyl group (trade name: KF polymer 9210, weight average molecular weight) (500,000, manufactured by Kureha Co., Ltd.) 5 parts by weight and 200 parts by weight of N-methyl-2-pyrrolidone are mixed with a double-arm kneader. The mixture was further mixed with a machine to prepare a positive electrode mixture slurry.

This positive electrode mixture slurry was applied to both surfaces of a strip-shaped aluminum foil (positive electrode current collector, 35 mm × 400 mm) having a thickness of 15 μm. The positive electrode mixture slurry on the surface of the strip-shaped aluminum foil was heated at 90 ° C. for 10 minutes in an air / nitrogen mixed atmosphere having a dew point of 0 ° C. and an oxygen partial pressure of 10 ⁻⁴ atm to form a positive electrode active material layer. . Subsequently, the positive electrode active material layer was rolled to produce a positive electrode. The total thickness of the positive electrode active material layers on both sides and the positive electrode current collector was 100 μm. Thereafter, the positive electrode was cut into a predetermined size to obtain a belt-like positive electrode plate.

  When the cross section of the cut piece was observed with a scanning electron microscope, a portion where the positive electrode active material layer was peeled off was not observed between the aluminum foil and the positive electrode active material layer. In addition, when the infrared ray spectroscopic analysis was performed on the positive electrode active material layer of the cut piece and the intensity of the absorption due to the carboxyl group was measured, a cross-linked portion of polyvinylidene fluoride having a carboxyl group was present in the positive electrode active material layer. It was confirmed.

(2) Production of Negative Electrode Scale-like artificial graphite was pulverized and classified to adjust the volume average particle diameter to 20 μm to obtain a negative electrode active material. 100 parts by weight of the negative electrode active material, 1 part by weight of styrene butadiene rubber (binder), and 100 parts by weight of a 1% by weight aqueous solution of carboxymethyl cellulose were mixed with a double-arm kneader to prepare a negative electrode mixture paste. . The negative electrode mixture paste was applied to both sides of a 10 μm thick copper foil (negative electrode current collector), dried, and then rolled to prepare a negative electrode. The total thickness of the negative electrode active material layers on both sides and the negative electrode current collector was 90 μm. Thereafter, the negative electrode was cut into a predetermined size to obtain a strip-shaped negative electrode plate.

(3) Preparation of nonaqueous electrolyte 1 part by weight of vinylene carbonate was added to 99 parts by weight of a mixed solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 3 to obtain a mixed solution. Thereafter, LiPF ₆ was dissolved in the mixed solution so that the concentration became 1.0 mol / L to prepare a non-aqueous electrolyte.

(4) Production of electrode group Using the obtained positive electrode plate, negative electrode plate and non-aqueous electrolyte, an electrode group 10 was produced as follows.
One end of the aluminum positive electrode lead 12 was connected to the positive electrode current collector. One end of the nickel negative electrode lead 13 was connected to the negative electrode current collector. These were wound by interposing a porous sheet made of polyethylene (separator, trade name: Hypore, manufactured by Asahi Kasei Co., Ltd.) having a thickness of 16 μm between the positive electrode plate and the negative electrode plate. The obtained wound electrode group was pressed under an environment of 25 ° C. to produce a flat electrode group 10. The press pressure was 0.5 MPa.

(5) Battery Assembly The obtained flat electrode group 10 was inserted into the square battery case 11. A resin frame (not shown) was mounted on the upper part of the electrode group 10. The resin frame body separates the electrode group 10 and the sealing plate 14 and prevents the positive electrode lead 12 or the negative electrode lead 13 and the battery case 11 from contacting each other. The other end of the positive electrode lead 12 was connected to the lower surface of the sealing plate 14. The other end of the negative electrode lead 13 was connected to the negative electrode terminal 15. The negative electrode terminal 15 was disposed on the sealing plate 14 through a resin gasket 16. The sealing plate 14 was placed in the opening of the battery case 11 and welded. A predetermined amount of nonaqueous electrolyte was injected into the battery case 11 from the injection hole of the sealing plate 14. Then, the non-aqueous secondary battery 1 of the present invention was produced by closing the liquid injection port with a plug 17.

(Example 2)
A nonaqueous secondary battery 1 of the present invention was produced in the same manner as in Example 1 except that 0.5 part by weight of aniline was used instead of 0.5 part by weight of trimethylamine.
When the cross section of the cut piece of the positive electrode plate was observed with a scanning electron microscope in the same manner as in Example 1, no portion where the positive electrode active material layer was peeled from the aluminum foil was found. Further, when the positive electrode active material layer of the cut piece was subjected to infrared spectroscopic analysis in the same manner as in Example 1, the presence of a crosslinked portion was confirmed.

(Example 3)
A nonaqueous secondary battery 1 of the present invention was produced in the same manner as in Example 1 except that 1 part by weight of lithium hydroxide was used instead of 0.5 part by weight of trimethylamine.
When the cross section of the cut piece of the positive electrode plate was observed with a scanning electron microscope in the same manner as in Example 1, no portion where the positive electrode active material layer was peeled from the aluminum foil was found. Further, when the positive electrode active material layer of the cut piece was subjected to infrared spectroscopic analysis in the same manner as in Example 1, the presence of a crosslinked portion was confirmed.

Example 4
A nonaqueous secondary battery 1 of the present invention was produced in the same manner as in Example 1 except that 1 part by weight of sodium carbonate was used instead of 0.5 part by weight of trimethylamine.
When the cross section of the cut piece of the positive electrode plate was observed with a scanning electron microscope in the same manner as in Example 1, no portion where the positive electrode active material layer was peeled from the aluminum foil was found. Further, when the positive electrode active material layer of the cut piece was subjected to infrared spectroscopic analysis in the same manner as in Example 1, the presence of a crosslinked portion was confirmed.

(Example 5)
A nonaqueous secondary battery was produced in the same manner as in Example 1 except that the amount of trimethylamine added was changed from 0.5 parts by weight to 0.002 parts by weight.
When the cross section of the cut piece of the positive electrode plate was observed with a scanning electron microscope in the same manner as in Example 1, a portion where the positive electrode active material layer was peeled from the aluminum foil was slightly observed. Moreover, when the positive electrode active material layer of the cut piece was subjected to infrared spectroscopic analysis in the same manner as in Example 1, the presence of fewer cross-linked portions than in Examples 1 to 6 was confirmed.

(Example 6)
A nonaqueous secondary battery was produced in the same manner as in Example 1 except that the amount of trimethylamine added was changed from 0.5 parts by weight to 2.5 parts by weight.
When the cross section of the cut piece of the positive electrode plate was observed with a scanning electron microscope in the same manner as in Example 1, no portion where the positive electrode active material layer was peeled from the aluminum foil was found. Further, when the positive electrode active material layer of the cut piece was subjected to infrared spectroscopic analysis in the same manner as in Example 1, the presence of a crosslinked portion was confirmed.

(Comparative Example 1)
A nonaqueous secondary battery was produced in the same manner as in Example 1 except that the positive electrode produced as described below was used.

[Positive electrode preparation]
100 parts by weight of lithium iron phosphate (LiFePO ₄ , positive electrode active material), 2 parts by weight of acetylene black (conductive agent), 3 parts by weight of polyvinylidene fluoride (PVDF, binder) in N-methyl-2-pyrrolidone The dissolved solution was mixed with a double-arm kneader to prepare a positive electrode mixture paste. A positive electrode mixture paste was applied to both sides of a strip-shaped aluminum foil (positive electrode current collector, 35 mm × 400 mm) having a thickness of 15 μm, dried, and then rolled to produce a positive electrode. The total thickness of the positive electrode active material layers on both sides and the positive electrode current collector was 150 μm. Thereafter, the positive electrode was cut into a predetermined size to obtain a belt-like positive electrode plate. The polyvinylidene fluoride here does not have a functional group such as a carboxyl group.

  When the cross section of the cut piece of the positive electrode plate was observed with a scanning electron microscope in the same manner as in Example 1, a portion where the positive electrode active material layer was separated from the aluminum foil was observed. Further, when the cut positive electrode active material layer was subjected to infrared spectroscopic analysis in the same manner as in Example 1, the presence of a crosslinked portion was not confirmed.

(Test Example 1)
The nonaqueous secondary batteries obtained in Examples 1 to 6 and Comparative Example 1 were subjected to the following evaluation. The results are shown in Table 1.

[Battery capacity evaluation]
For the non-aqueous secondary batteries of Examples 1 to 6 and Comparative Example 1, the charge / discharge cycle was repeated three times under the following conditions, and the third discharge capacity was obtained to obtain the battery capacity. The results are shown in Table 1.
Constant current charging: 200 mA, final voltage 4.2V.
Constant voltage charging: end current 20 mA, rest time 20 minutes.
Constant current discharge: current 200 mA, final voltage 2.5 V, rest time 20 minutes.

[Cycle life evaluation]
The batteries of Examples 1 to 6 and Comparative Example 1 were repeatedly charged and discharged at 45 ° C. under the following conditions. The cycle life was defined as the number of cycles where the discharge capacity of the battery was half the discharge capacity of the first cycle. The results are shown in Table 1.
Constant current charging: Charging current value 500 mA / end-of-charge voltage 4.2 V
Constant voltage charging: Charging voltage value 4.2V / end-of-charge current 100mA
Constant current discharge: discharge current value 500 mA / discharge end voltage 3 V

  From Table 1, it is clear that the batteries of Examples 1 to 4 have little decrease in discharge capacity even after repeated charge and discharge cycles, and can maintain battery performance at a high level for a long period. This is considered to be because the adhesiveness between the positive electrode current collector and the positive electrode active material layer is improved by crosslinking a part of the polyvinylidene fluoride having a carboxyl group as a binder.

  In addition, in the cycle life evaluation, the batteries of Examples 1 to 4 have a cycle life despite constant current charging at a charge end voltage of 4.2 V and constant voltage charging at a charge voltage value of 4.2 V. Excellent characteristics. This is presumably because the cross-linked portion of polyvinylidene fluoride having a carboxyl group in the positive electrode active material layer is stable even in a high voltage region of 4.0 V or higher and is not easily decomposed.

  The non-aqueous secondary battery of the present invention can be used in the same applications as conventional non-aqueous secondary batteries, and is particularly useful as a power source for portable electronic devices. Examples of portable electronic devices include personal computers, mobile phones, mobile devices, personal digital assistants (PDAs), portable game devices, and video cameras. The non-aqueous secondary battery of the present invention is a main power source or auxiliary power source for driving an electric motor in a hybrid electric vehicle, a fuel cell vehicle, a plug-in HEV, etc., a driving power source for a power tool, a vacuum cleaner, a robot, etc. Is expected to be used.

DESCRIPTION OF SYMBOLS 1 Non-aqueous secondary battery 10 Flat electrode group 11 Battery case 12 Positive electrode lead 13 Negative electrode lead 14 Sealing plate 15 Negative electrode terminal 16 Gasket 17 Sealing

Claims (11)

A positive electrode, a negative electrode, a separator disposed so as to be interposed between the positive electrode and the negative electrode, and a lithium ion conductive nonaqueous electrolyte,
The positive electrode includes a positive electrode active material layer and a positive electrode current collector, the positive electrode active material layer contains olivine type lithium phosphate and a fluororesin having a crosslinkable functional group, and the fluorine having the crosslinkable functional group. A non-aqueous secondary battery in which at least a part of a resin is crosslinked and the negative electrode includes a negative electrode active material layer containing a negative electrode active material capable of occluding and releasing lithium ions and a negative electrode current collector.   The non-aqueous secondary battery according to claim 1, wherein the olivine type lithium phosphate is iron lithium phosphate.   The non-aqueous secondary battery according to claim 1 or 2, wherein the content of the functional group in the fluororesin is 0.1 to 100 mmol per 1 g of the fluororesin.   The fluororesin is polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-vinylidene fluoride copolymer, hexafluoropropylene-vinylidene fluoride copolymer The nonaqueous secondary battery according to any one of claims 1 to 3, which is at least one selected from the group consisting of a coalescence and polyvinylidene fluoride.   The non-aqueous secondary battery according to claim 1, wherein the crosslinkable functional group is a carboxyl group. Including a positive electrode manufacturing process, a negative electrode manufacturing process, an electrode group manufacturing process and a battery assembly process,
In the positive electrode preparation step, a positive electrode mixture slurry containing an olivine type lithium phosphate, a fluororesin having a crosslinkable functional group, a crosslinker and an organic solvent is applied to the surface of the positive electrode current collector, heated, and positive electrode An active material layer is formed, and a positive electrode capable of inserting and extracting lithium ions is produced.
In the negative electrode preparation step, a negative electrode capable of inserting and extracting lithium ions is prepared,
In the electrode group production step, a separator is interposed between the positive electrode and the negative electrode, and these are laminated or wound to produce an electrode group. In the battery assembly step, the electrode group is made of lithium ion conductive material. A non-aqueous secondary battery manufacturing method for obtaining a non-aqueous secondary battery by housing the battery case in an open battery case together with the non-aqueous electrolyte and then sealing the opening of the battery case.   The non-aqueous secondary battery according to claim 6, wherein the crosslinking agent contained in the positive electrode mixture slurry is at least one selected from the group consisting of alkylamines, aromatic amines, lithium hydroxide, and sodium carbonate. Production method.   The method for producing a nonaqueous secondary battery according to claim 6 or 7, wherein the content of the crosslinking agent in the positive electrode mixture slurry is 0.003 to 2 wt% of the total amount of the positive electrode mixture slurry.   The method for manufacturing a non-aqueous secondary battery according to claim 6, wherein the heating in the positive electrode manufacturing step is performed at a temperature of 80 ° C. to 100 ° C.   The method of manufacturing a non-aqueous secondary battery according to claim 6, wherein the heating in the positive electrode manufacturing step is performed in an atmosphere having a dew point of 0 ° C. or higher. The method for producing a non-aqueous secondary battery according to claim 10, wherein an oxygen partial pressure in an atmosphere having a dew point of 0 ° C. or higher is 10 ⁻⁵ atm to 10 ⁻² atm.

Images