JPH11297312A - Raw material and manufacture for polymer electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance charging and discharging performance in repeated usage. SOLUTION: This raw material for a polymer electrolyte secondary battery has a structure, in which a paste free from a nonaqueous electrolyte is applied to a current collector, and a density of a portion excluding the collector is 90% or higher of the theoretical density. This manufacturing method for the polymer electrolyte secondary battery has a process for applying the paste free from the nonaqueous electrolyte to the collector, a process for heating the resulting applied body, and a process for conducting press working for the applied body, thereby at least one electrode from among a positive electrode and a negative electrode is manufactured according to the manufacturing method. The temperature for the press working is made lower than the heating temperature for the applied body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a material for a polymer electrolyte secondary battery and a method for producing a polymer electrolyte secondary battery.

[0002]

2. Description of the Related Art In recent years, with the development of electronic equipment, there has been a demand for the development of a non-aqueous electrolyte secondary battery that is small, lightweight, has a high energy density, and can be repeatedly charged and discharged. Such a secondary battery includes a negative electrode containing lithium or a lithium alloy as an active material, a positive electrode containing an oxide, sulfide, or selenide such as molybdenum, vanadium, titanium, or niobium as an active material, and a nonaqueous electrolyte. There is known a lithium secondary battery including:

In recent years, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, such as coke, graphite, carbon fiber, a resin fired body, and pyrolytic gas phase carbon, has been used as a negative electrode. The development and commercialization of lithium ion secondary batteries using lithium and lithium manganese oxide-containing batteries are being actively pursued.

Meanwhile, in order to further reduce the weight and size of the secondary battery, for example, US Pat.
As disclosed in US Pat. No. 6,318,318, a polymer electrolyte secondary battery has been developed. This polymer electrolyte secondary battery includes a sheet-shaped positive electrode, a sheet-shaped negative electrode, and an electrolyte layer interposed between the positive electrode and the negative electrode. The secondary battery is manufactured by, for example, a method described below. First, a plasticizer that can be removed later, such as DBP (dibutyl phthalate), and vinylidene fluoride [Vd
F] and a binder such as a copolymer of hexafluoropropylene [HFP] are mixed in the presence of a solvent, and the mixture is formed into a sheet to form an electrolyte layer not impregnated with a non-aqueous electrolyte. On the other hand, an active material that absorbs and releases lithium ions,
The plasticizer and the binder are mixed in the presence of a solvent, molded into a sheet, and the obtained sheet is thermocompressed to a current collector to form a non-aqueous electrolyte unimpregnated positive electrode and negative electrode. Make it. The obtained positive electrode and negative electrode are laminated with an electrolyte layer interposed therebetween, and integrated by, for example, thermocompression bonding. After removing the plasticizer in the laminate,
The battery is manufactured by impregnating with a non-aqueous electrolyte and sealing the obtained power generating element with an exterior material.

However, according to the above-described manufacturing method, since the positive electrode and the negative electrode not impregnated with the non-aqueous electrolyte are produced by thermocompression bonding between the sheet and the current collector, there is a problem that productivity is poor.

For this reason, the positive electrode and the negative electrode not impregnated with the electrolyte are mixed into a paste by mixing an active material, a plasticizer, and a binder in the presence of a solvent, and the obtained paste is applied to a current collector. It is considered to be manufactured by a method. However, since the density of the positive electrode or the negative electrode manufactured by a simple application method is low, there is a problem that the cycle life of the polymer electrolyte secondary battery is shortened.

Further, it has been proposed to produce a positive electrode or a negative electrode not impregnated with an electrolyte by a method such as calendering using a resin roll as performed in a manufacturing process of a magnetic recording tape or the like. However, according to this method, since the densities of the positive electrode and the negative electrode do not become sufficiently high, there is a problem that the cycle life is short as in the above-described coating method.

On the other hand, an active material, a plasticizer and a binder are mixed in the presence of a solvent to form a paste, the obtained paste is applied to a current collector, and the obtained applied body is heated and pressed. Fabrication of a positive electrode or a negative electrode that is not impregnated with an electrolyte has been studied.

[0009]

However, according to the above-mentioned method, the coated body is easily taken up on a roll and easily stretched. To avoid this, if the pressing temperature is lowered or the pressing force is lowered, the density is reduced. There is a problem that the cycle life is shortened because it is not sufficiently increased. Further, the elongation of the coated body during heating and pressurization was remarkable when a porous current collector such as expanded metal was used as the current collector.

An object of the present invention is to provide a material for a polymer electrolyte secondary battery capable of improving charge / discharge performance in repeated use.

Another object of the present invention is to provide a method for producing a polymer electrolyte secondary battery having high productivity and improved charge / discharge performance in repeated use.

[0012]

A material for a polymer electrolyte secondary battery according to the present invention has a structure in which a paste containing no non-aqueous electrolyte is applied to a current collector. The density of the portion is 90% or more of the theoretical density.

The method for producing a polymer electrolyte secondary battery according to the present invention comprises the steps of: applying a paste containing no nonaqueous electrolyte to a current collector; heating the applied body; And forming at least one of a positive electrode and a negative electrode by a method including a step of pressing.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a material for a polymer electrolyte secondary battery according to the present invention and a method for manufacturing the polymer electrolyte secondary battery will be described.

(First Step) A positive electrode material not impregnated with a nonaqueous electrolyte, a negative electrode material not impregnated with a nonaqueous electrolyte, and an electrolyte layer not impregnated with a nonaqueous electrolyte are prepared.

<Material for Positive Electrode> For the material for positive electrode, for example, a paste is prepared by kneading a positive electrode active material, a binder, a plasticizer and, if necessary, a conductive material in the presence of a solvent,
After the paste is applied to a current collector, the paste is heated at least once and then pressed at least once.

Examples of the positive electrode active material include various oxides (eg, lithium manganese composite oxide such as LiMn ₂ O ₄ , manganese dioxide, lithium-containing nickel oxide such as LiNiO _2, and lithium-containing cobalt oxide such as LiCoO _2). Oxide, lithium-containing nickel-cobalt oxide, lithium-containing amorphous vanadium pentoxide and the like, and chalcogen compounds (for example, titanium disulfide and molybdenum disulfide). Among them, it is preferable to use a lithium manganese composite oxide, a lithium-containing cobalt oxide, and a lithium-containing nickel oxide.

The binder has a property of retaining a non-aqueous electrolyte. Examples of such a binder include a polyethylene oxide derivative, a polypropylene oxide derivative, a polymer containing the derivative, polytetrafluoropropylene, a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), and polyvinylidene fluoride ( PVdF) or the like can be used. Among them, a VdF-HFP copolymer is preferred. In the copolymer, VdF contributes to the improvement of the mechanical strength of the sheet at the skeleton of the copolymer, and HFP has an amorphous structure and functions as a lithium ion transmission part. The HF
It is preferable that the copolymerization ratio of P be 12% by weight or less.

The plasticizer has excellent compatibility with the binder, can impart flexibility to the sheet, can lower the melting point of the sheet for improving formability, and is easily removed. Things are good. As the plasticizer,
For example, dibutyl phthalate (DBP), dimethyl phthalate (DMP), ethylphthalylethyl glycolate (E
PEG) and the like.

The positive electrode may include a conductive material from the viewpoint of improving conductivity. Examples of the conductive material include artificial graphite, carbon black (eg, acetylene black), nickel powder, and the like.

Examples of the current collector include those having a porous structure such as expanded metal made of aluminum, mesh made of aluminum, and punched metal made of aluminum, and metal foils such as aluminum foil.

In the positive electrode material, the density of the portion excluding the current collector (the positive electrode layer not impregnated with the nonaqueous electrolyte) is 9% of the theoretical density.
It is preferably 0% or more. Where the theoretical density is
The positive electrode material excluding the solvent (for example, the positive electrode active material,
The density when the binder, the plasticizer, and the conductive material) are regarded as one substance. If the density is less than 90% of the theoretical density, the number of voids in the positive electrode increases,
The cycle life of the secondary battery may be reduced. A more preferable range is 95% or more of the theoretical density.

The heating is performed, for example, by passing between heater blocks. The heating temperature varies depending on the composition of the paste and the like, but is preferably in the range of 110 to 180 ° C, for example.
If the heating temperature is lower than 110 ° C., it may be difficult to increase the density of the non-aqueous electrolyte-unimpregnated positive electrode layer to 90% or more of the theoretical density. On the other hand, when the heating temperature is 18
If the temperature exceeds 0 ° C., there is a possibility that the coated body is elongated. A more preferable range of the heating temperature is 120 to 160 ° C.

The pressing is performed, for example, by a twin roll press or a flat plate press. It is preferable that the temperature of the press be lower than the heating temperature. If the pressing temperature is equal to or higher than the heating temperature, there is a possibility that the coated body will be stretched. The pressing temperature varies depending on the composition of the paste and the like, but is preferably less than 100 ° C. If the press temperature is lower than 50 ° C., the coated body heated in the heating step may be rapidly cooled, and it may be difficult to increase the density. Therefore, the pressing temperature is 50
It is more preferable that the temperature is not lower than 100 ° C and lower than 100 ° C.

The pressing pressure varies depending on the composition of the paste and the like.
It is preferable to set the range to 7 kgf / cm. If the pressing pressure is less than 3 kgf / cm, it may be difficult to increase the density of the positive electrode layer not impregnated with the electrolyte to 90% or more of the theoretical density. On the other hand, when the press pressure is 7 kgf
If it exceeds / cm, the coated body may be stretched.
A more preferable range of the press pressure is 4 to 6 kgf / c.
m.

In the method for producing a polymer electrolyte secondary battery according to the present invention, when the negative electrode is prepared by applying a paste, heating and pressing, the positive electrode is made of a positive electrode active material, a binder,
A paste is prepared by kneading a plasticizer and, if necessary, a conductive material in the presence of a solvent, forming the paste into a sheet shape, and thermocompression-bonding the obtained sheet to a current collector. Tolerate.

<Material for Negative Electrode> For the material for the negative electrode, for example, a paste is prepared by kneading a negative electrode active material, a binder, a plasticizer and, if necessary, a conductive material in the presence of a solvent.
The paste is applied to a current collector, and the obtained applied body is heated and then pressed at least once.

Examples of the negative electrode active material include carbonaceous materials that occlude and release lithium ions. Such carbonaceous materials include, for example, those obtained by firing organic polymer compounds (eg, phenolic resin, polyacrylonitrile, cellulose, etc.), those obtained by firing coke and mesophase pitch, and those made by artificial graphite. And carbonaceous materials represented by natural graphite and the like. Among them, 5
It is preferable to use a carbonaceous material obtained by firing the mesophase pitch at a temperature of 00 ° C to 3000 ° C under normal pressure or reduced pressure.

Examples of the current collector include those having a porous structure such as copper expanded metal, copper mesh, and copper punched metal, and metal foils such as copper foil.

As the binder, the plasticizer, and the conductive material, the same materials as described in the above-described positive electrode are used.

In the negative electrode material, the density of a portion excluding the current collector (a negative electrode layer not impregnated with a non-aqueous electrolyte) has a theoretical density of 9%.
It is preferably 0% or more. Where the theoretical density is
The negative electrode material excluding the solvent (for example, the negative electrode active material,
The density when the binder, the plasticizer, and the conductive material) are regarded as one substance. If the density is less than 90% of the theoretical density, the number of voids in the negative electrode increases,
The cycle life of the secondary battery may be reduced. A more preferable range is 95% or more of the theoretical density.

The heating can be performed by the same method as described for the positive electrode. The heating temperature is
Although it depends on the composition of the paste, etc., 110
It is preferable that the temperature be in the range of 180 to 180 ° C. If the heating temperature is lower than 110 ° C., it may be difficult to increase the density of the non-aqueous electrolyte-unimpregnated negative electrode layer to 90% or more of the theoretical density. On the other hand, if the heating temperature exceeds 180 ° C., there is a possibility that the coated body may be elongated. A more preferable range of the heating temperature is 120 to 160 ° C.

The pressing can be performed by the same method as described for the positive electrode. It is preferable that the temperature of the press be lower than the heating temperature.
If the pressing temperature is equal to or higher than the heating temperature, the coated body may be elongated. Although the pressing temperature varies depending on the composition of the paste and the like,
It is preferable that the temperature is lower than 00 ° C. If the press temperature is lower than 50 ° C., the coated body heated in the heating step may be rapidly cooled, and it may be difficult to increase the density. Therefore, it is more preferable that the pressing temperature is 50 ° C. or higher and lower than 100 ° C.

The pressing pressure varies depending on the composition of the paste and the like.
It is preferable to set the range to 7 kgf / cm. If the pressing pressure is less than 1 kgf / cm, it may be difficult to increase the density of the negative electrode layer not impregnated with the electrolyte to 90% or more of the theoretical density. On the other hand, when the press pressure is 7 kgf
If it exceeds / cm, the coated body may be stretched.
The more preferable range of the press pressure is 2 to 5 kgf / c.
m.

In the method for producing a polymer electrolyte secondary battery according to the present invention, in the case where the positive electrode is manufactured by applying a paste, heating and pressing, the negative electrode is made of a negative electrode active material, a binder,
A paste is prepared by kneading a plasticizer and, if necessary, a conductive material in the presence of a solvent, forming the paste into a sheet shape, and thermocompression-bonding the obtained sheet to a current collector. Tolerate.

<Electrolyte layer not impregnated with non-aqueous electrolyte> A paste is prepared by kneading a binder and a plasticizer (and, if necessary, organic particles or inorganic particles) in the presence of a solvent to form a film. Thus, the electrolyte layer is produced.

As the binder and the plasticizer, those similar to those described for the above-described positive electrode are used.
In particular, the binder is preferably a VdF-HFP copolymer. The HFP copolymerization ratio of the copolymer is from 8 to
It is preferred that the content be in the range of 20% by weight.

By adding organic particles or inorganic particles such as silicon oxide powder to the paste, the strength of the electrolyte layer can be improved.

(Second Step) The positive electrode material and the negative electrode material are laminated with the electrolyte layer interposed therebetween, and integrated by, for example, thermocompression bonding to obtain a laminate. Alternatively, a paste may be applied to the material for the positive electrode or the material for the negative electrode to form an electrolyte layer not impregnated with the electrolytic solution, and a laminate may be formed by stacking a material having a polarity opposite to that of the material described above. good.

(Third Step) The plasticizer in the laminate is removed.

The removal of the plasticizer is preferably performed by solvent extraction.

In the solvent extraction, it is preferable to apply ultrasonic waves to the solvent or reduce the pressure of the atmosphere. The solvent used is not particularly limited as long as it does not easily damage the battery material and has good compatibility with the plasticizer. For example,
Organic solvents such as alcohols and saturated hydrocarbon compounds are preferred.

(Fourth Step) The laminate is impregnated with a non-aqueous electrolyte.

The non-aqueous electrolyte is prepared by dissolving an electrolyte in a non-aqueous solvent.

Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and dimethyl carbonate (D
MC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (γ-
BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like. The non-aqueous solvents may be used alone or as a mixture of two or more.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ) and lithium hexafluorophosphate (L
iPF _6), boric tetrafluoride lithium (LiBF _4), lithium hexafluoroarsenate (LiAsF _6), lithium salts such as lithium trifluoromethane sulfonate (LiCF ₃ SO ₃₎ may be mentioned.

The amount of the electrolyte dissolved in the non-aqueous solvent is desirably 0.2 mol / l to 2 mol / l.

A polymer electrolyte secondary battery can be obtained by the method including the first to fourth steps.

As described above in detail, the material for a polymer electrolyte secondary battery according to the present invention has a structure in which a paste containing no non-aqueous electrolyte is applied to a current collector, and the current collector is The density of the removed part is 90% or more of the theoretical density. A positive electrode and a negative electrode manufactured using such a material can reduce voids. Therefore, the polymer electrolyte secondary battery including at least one of the positive electrode and the negative electrode can improve charge / discharge performance in repeated use such as cycle life.

The method for producing a polymer electrolyte secondary battery according to the present invention comprises the steps of: applying a paste containing no non-aqueous electrolyte to a current collector; heating the applied body;
Pressing the coated body. According to such a method, even when a porous current collector is used as the current collector, the density of a portion excluding the current collector can be increased without causing a problem such as elongation of the coating body. By producing at least one of the positive electrode and the negative electrode from the obtained electrode material, a polymer electrolyte secondary battery having improved charge / discharge performance in repeated use such as cycle life is produced in a method with excellent productivity. Can be provided. Further, according to the present invention, it is possible to take advantage of the use of a porous current collector, which can remove a plasticizer and impregnate a non-aqueous electrolyte in a short time.

Further, by lowering the temperature of the press as compared with the heating temperature, the density of the electrode material manufactured by the above-described method can be further increased, so that the cycle life can be further improved. it can.

Further, since the paste contains a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP) and a plasticizer, the amount of the nonaqueous electrolyte impregnated in the secondary battery can be increased. Therefore, the cycle life can be significantly improved.

[0053]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described below in detail with reference to the drawings.

Example 1 <Preparation of Material for Positive Electrode> The composition formula of the active material was LiCoO.
56% by weight of lithium-containing cobalt oxide represented by ₂
And 5% by weight of carbon black, and vinylidene fluoride-hexafluoropropylene (Vd
F-HFP) copolymer powder (copolymerization ratio VdF is 8
8% by weight and HFP is 12% by weight) to 17% by weight
And 22% by weight of dibutyl phthalate (DBP) were mixed in acetone to prepare a paste. The obtained paste was applied to both sides of a current collector made of expanded metal made of aluminum having an opening ratio of 70% by a die coater to a width of 50 mm and a width of 1 mm.
About 100 m was applied. After passing the obtained coated body between heater blocks heated to 150 ° C. at 1 m / min,
By repeating the operation of passing between twin rolls set to a press pressure of kgf / cm three times, a positive electrode material having a non-aqueous electrolyte-unimpregnated positive electrode layer density equivalent to 98% of the theoretical density is produced. did. The obtained positive electrode material had no elongation. In addition, the temperature of the applied body at the time of pressing is 7
It was 0 ° C. The theoretical density was calculated from the density of a mixture of a lithium-containing cobalt oxide, carbon black, a copolymer of VdF-HFP, and DBP.

<Preparation of Material for Negative Electrode> Mesophase pitch carbon fiber as active material: 56% by weight, carbon black: 2% by weight, binder: VdF-HFP copolymer powder similar to that described for the positive electrode 17% by weight
And 25% by weight of dibutyl phthalate (DBP) in dimethylformamide to prepare a paste. The obtained paste was applied to both sides of a current collector made of a copper expanded metal having an opening ratio of 70% by a die coater to have a width of 55 mm and a thickness of about 100 m. After passing the obtained coated body between heater blocks heated to 145 ° C. at 1 m / min,
The operation of passing between twin rolls set to a press pressure of 4.5 kgf / cm is repeated three times, whereby the density of the non-aqueous electrolyte-unimpregnated negative electrode layer corresponds to 95% of the theoretical density. Was prepared. The obtained negative electrode material is
There was no elongation. In addition, the temperature of the applied body at the time of pressing was 70 ° C. The theoretical density is mesophase pitch carbon fiber, carbon black, VdF-HF
It was calculated from the density of the mixture consisting of the copolymer of P and DBP.

<Preparation of Electrolyte Layer Not Impregnated with Nonaqueous Electrolyte> 33.3 parts by weight of silicon oxide powder and 22.2 VdF-HFP copolymer powder similar to that described for the positive electrode as a binder were used. Parts by weight and dibutyl phthalate (DBP) 4
4.5 parts by weight were mixed in acetone to form a paste. The obtained paste was applied on a PET film, formed into a sheet, and an electrolyte layer not impregnated with a non-aqueous electrolyte was prepared.

<Preparation of Non-Aqueous Electrolyte> LiPF ₆ as an electrolyte was added to a non-aqueous solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 2: 1 at a concentration of 1 mol / mol. 1 to prepare a non-aqueous electrolyte.

<Assembly of Battery> The obtained positive electrode material and negative electrode material were cut into predetermined dimensions. The material for the positive electrode is 2
Sheets, one sheet of the material for the negative electrode and two sheets of the electrolyte layer not impregnated with the electrolytic solution are prepared, and the material for the positive electrode and the material for the negative electrode are alternately laminated while interposing the electrolyte layer therebetween,
After passing these through a heated heater block, they were passed between twin rolls to produce a laminate containing a plasticizer.

Such a laminate was immersed in methanol and left with stirring with a magnetic stirrer.
This operation was repeated until the concentration of DBP by gas chromatography became 20 ppm or less, thereby removing the plasticizer in the laminate. After drying the laminate, positive and negative electrode leads are connected, impregnated with a non-aqueous electrolyte of the above composition, and sealed with an exterior film to have a structure shown in FIG. 1 and a theoretical capacity of 110 mAh. A polymer electrolyte secondary battery was manufactured.

That is, the power generating element 1 includes the negative electrode 4 having a structure in which the negative electrode layer 2 is supported on both surfaces of the porous current collector 3.
The two positive electrodes 5 are stacked on both surfaces of the negative electrode 4 with an electrolyte layer 6 interposed therebetween. Each positive electrode 5 has a structure in which a positive electrode layer 7 is supported on both surfaces of a porous current collector 8. The current collector 3 of the negative electrode 4 has a strip-shaped negative electrode terminal 9 in a portion located on the near side in FIG. The current collector 8 of each of the positive electrodes 5 has a band-shaped positive terminal 10 at a position where the current collector 8 does not overlap with the negative terminal 9 (for example, a portion located on the back side in FIG. 1). The negative electrode terminal 9 is connected to a strip-shaped negative electrode lead 11. On the other hand, the two positive electrode terminals 10 are connected to a belt-like positive electrode lead (not shown). Such a power generation element 1 is covered with an exterior film 12 having a barrier function against moisture, air, and the like so that the positive electrode lead and the negative electrode lead 11 extend from the film 12. The opening of the film 12 is sealed by heat-sealing a heat-fusible resin disposed on the inner surface thereof.

(Example 2) <Preparation of positive electrode material> A paste obtained in the same manner as in Example 1 was applied to both surfaces of a current collector similar to that described in Example 1 in the same manner as in Example 1. did. The obtained coated body was cut into a predetermined size, and sandwiched between 100 mm square brass plates.
After passing through the heater block heated to 0 ° C. at a rate of 1 m / min, the operation of applying a pressure of 8 × 10 ⁴ Pa by a flat plate press is repeated three times, so that the positive electrode layer not impregnated with the nonaqueous electrolytic solution is obtained. Of a positive electrode having a density of 96% of the theoretical density. The obtained positive electrode material had no elongation. In addition, the temperature of the applied body at the time of pressing was 70 ° C.

<Preparation of Material for Negative Electrode> A paste obtained in the same manner as in Example 1 was applied to both surfaces of a current collector similar to that described in Example 1 in the same manner as in Example 1. The obtained coated body was cut out into a predetermined size, sandwiched between 100 mm square brass plates, passed between heater blocks heated to 160 ° C. at 1 m / min, and then pressed with a flat plate press at 8 × 10 ⁴ Pa. By repeating the operation of applying pressure three times, a negative electrode material having a density of the non-aqueous electrolyte-unimpregnated negative electrode layer corresponding to 96% of the theoretical density was produced. The obtained negative electrode material had no elongation. In addition, the temperature of the applied body at the time of pressing was 70 ° C.

<Assembly of Battery> Two positive electrode materials and one negative electrode material and two electrolyte layers similar to those described in Example 1 were prepared, and the positive electrode material and the negative electrode material were prepared. After alternately laminating the materials with the electrolyte layer interposed therebetween, and after passing them through the heater block heated,
By passing between twin rolls, a laminate containing a plasticizer was prepared.

The plasticizer was removed from such a laminate in the same manner as described in Example 1. After drying the laminate, the positive and negative electrode leads are connected, impregnated with a non-aqueous electrolyte having the same composition as in Example 1, and sealed with an exterior film to obtain the structure shown in FIG. 1 described above. Then, a polymer electrolyte secondary battery having a theoretical capacity of 110 mAh was manufactured.

(Comparative Example 1) <Preparation of Material for Positive Electrode> A paste obtained in the same manner as in Example 1 was applied to both surfaces of a current collector similar to that described in Example 1 in the same manner as in Example 1. Then, a positive electrode material was prepared in which the density of the positive electrode layer not impregnated with the nonaqueous electrolyte solution was 83% of the theoretical density.

<Preparation of Material for Negative Electrode> A paste obtained in the same manner as in Example 1 was applied to both surfaces of a current collector similar to that described in Example 1 in the same manner as in Example 1, and then subjected to non-aqueous electrolysis. A negative electrode material was prepared in which the density of the liquid-impregnated negative electrode layer was 74% of the theoretical density.

The obtained positive electrode material and negative electrode material were cut into predetermined dimensions. Two positive electrode materials, one negative electrode material, and two electrolyte layers similar to those in Example 1 were prepared, and the positive electrode material and the negative electrode material were alternately arranged with the electrolyte layer interposed therebetween. After passing these through a heater block heated, they were passed between twin rolls to produce a laminate containing a plasticizer.

The plasticizer was removed from such a laminate in the same manner as described in Example 1. After drying the laminate, the positive and negative electrode leads are connected, impregnated with a non-aqueous electrolyte having the same composition as in Example 1, and sealed with an exterior film to obtain the structure shown in FIG. 1 described above. Then, a polymer electrolyte secondary battery having a theoretical capacity of 110 mAh was manufactured.

(Comparative Example 2) A positive electrode paste obtained in the same manner as in Example 1 was applied to both surfaces of the same positive electrode current collector as described in Example 1, and then applied at 110 ° C. When the mixture was heated and heated and passed between twin rolls set at a press pressure of 5 kgf / cm, the coated body was taken up by the upper and lower rolls, and elongation occurred, so that a positive electrode material could not be obtained.

On the other hand, as for the material for the negative electrode, the paste obtained in the same manner as in Example 1 was applied to both surfaces of the current collector similar to that described in Example 1, and thereafter,
When the mixture was heated to 10 ° C. and passed between twin rolls set at a pressing pressure of 3 kgf / cm, the coated body was taken up by the upper and lower rolls, elongation occurred, and a negative electrode material could not be obtained. .

(Comparative Example 3) <Preparation of Material for Positive Electrode> A paste obtained in the same manner as in Example 1 was applied to both surfaces of a current collector similar to that described in Example 1 in the same manner as in Example 1. After that, the mixture was passed between twin rolls heated to 100 ° C. and set to a pressing pressure of 5 kgf / cm, and the density of the non-aqueous electrolyte-unimpregnated positive electrode layer was 86% of the theoretical density. The material was made.

<Preparation of Material for Negative Electrode> A paste obtained in the same manner as in Example 1 was applied to both surfaces of a current collector similar to that described in Example 1 in the same manner as in Example 1, and then heated to 100 ° C. And passed through a twin roll set at a press pressure of 3 kgf / cm to produce a negative electrode material in which the density of the non-aqueous electrolyte-unimpregnated negative electrode layer was 83% of the theoretical density.

The obtained positive electrode material and negative electrode material were cut into predetermined dimensions. Two positive electrode materials, one negative electrode material, and two electrolyte layers similar to those in Example 1 were prepared, and the positive electrode material and the negative electrode material were alternately arranged with the electrolyte layer interposed therebetween. After passing these through a heater block heated, they were passed between twin rolls to produce a laminate containing a plasticizer.

The plasticizer was removed from such a laminate in the same manner as described in Example 1. After drying the laminate, the positive and negative electrode leads are connected, impregnated with a non-aqueous electrolyte having the same composition as in Example 1, and sealed with an exterior film to obtain the structure shown in FIG. 1 described above. Then, a polymer electrolyte secondary battery having a theoretical capacity of 110 mAh was manufactured.

Regarding the obtained secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 3, a constant current of 1 C (110 mAh),
A charge / discharge cycle test in which a constant voltage charge of 4.2 V and a constant current discharge of 1 C (110 mAh) is performed at 20 ° C.
Was measured, and the results are shown in Table 1 below. The cycle life is indicated by the number of cycles when the capacity is reduced to 80% of the initial capacity.

[0076]

[Table 1]

As is apparent from Table 1, the secondary batteries of Examples 1 and 2 have a longer cycle life than the secondary batteries of Comparative Examples 1 and 3. Further, as shown in Comparative Example 2, when the application body is heated and pressed at 110 ° C. without previously heating, the application body is taken up by the upper and lower rolls, and the application body is elongated.

[0078]

As described above in detail, according to the material for a polymer electrolyte secondary battery and the method for producing a polymer electrolyte secondary battery according to the present invention, the stability of battery characteristics in repeated use can be improved. Has a remarkable effect.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a polymer electrolyte secondary battery manufactured by a method according to an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Power generation element, 4 ... Negative electrode, 5 ... Positive electrode, 6 ... Electrolyte layer, 12 ... Exterior film.

Claims (4)

[Claims] 1. A structure in which a paste containing no non-aqueous electrolyte is applied to a current collector, and a density of a portion excluding the current collector is 90% or more of a theoretical density. For polymer electrolyte secondary batteries. 2. A method comprising: applying a paste containing no non-aqueous electrolyte to a current collector; heating the applied body; and pressing the applied body. A method for producing a polymer electrolyte secondary battery, wherein at least one of the negative electrodes is produced. 3. The method according to claim 2, wherein a temperature at which the pressing is performed is lower than a temperature at which the coated body is heated. 4. The method for producing a polymer electrolyte secondary battery according to claim 2, wherein the paste contains a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP) and a plasticizer.