JP2001332302A - Gel electrolyte precursor, nonaqueous secondary cell and method of manufacturing nonaqueous secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary cell improved in reliability and rate characteristics. SOLUTION: For the nonaqueous secondary cell comprising a positive electrode 1, a negative electrode 2 and a gel electrolyte layer 3 arranged between the electrode is 1 and e 2, the gel electrolyte layer 3 is obtained by impregnating a porous gel electrolyte layer precursor containing a first polymer insoluble in a nonaqueous electrolyte and a second polymer having the property of gelling the nonaqueous electrolyte with the nonaqueous electrolyte, and heating and cooling the impregnated electrolyte precursor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gel electrolyte precursor, a non-aqueous secondary battery, and a method for producing a non-aqueous 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 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 using 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. A non-aqueous electrolyte secondary battery having the following is known.

In addition, instead of a negative electrode using lithium or a lithium alloy as an active material, a carbonaceous material (for example, coke, graphite, carbon fiber, resin fired body, and pyrolytic carbon) that absorbs and releases lithium ions is included. A non-aqueous electrolyte secondary battery using a negative electrode has been proposed. According to the secondary battery, deterioration of negative electrode characteristics due to dendritic deposition is improved, and cycle life and safety are increased as compared with a secondary battery including a negative electrode using lithium or a lithium alloy as an active material.

In such a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte is merely impregnated in the electrode group. However, in order to further improve safety, it is easy to reduce the thickness and weight. For this reason, attempts have been made to hold a non-aqueous electrolyte solution in a polymer (for example, see Japanese Patent Application Laid-Open No.
Publication No.).

[0005] However, a non-aqueous electrolyte secondary battery in which a non-aqueous electrolyte is held by a polymer is not sufficient in reliability and rate characteristics.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gel electrolyte precursor capable of improving the reliability and rate characteristics of a non-aqueous secondary battery.

An object of the present invention is to provide a non-aqueous secondary battery with improved reliability and rate characteristics, and a method for manufacturing the non-aqueous secondary battery.

[0008]

The gel electrolyte precursor according to the present invention comprises a first polymer which is hardly soluble in a non-aqueous electrolyte and a second polymer which has a property of gelling the non-aqueous electrolyte. A gel electrolyte precursor for obtaining a gel electrolyte by impregnating a gel electrolyte precursor containing the same with a non-aqueous electrolyte, heating, and then cooling, characterized by having a porous structure.

The gel electrolyte precursor according to the present invention comprises, for example, a first polymer which is hardly soluble in a non-aqueous electrolyte and a second polymer which has a property of gelling the non-aqueous electrolyte. A step of preparing a paste by kneading with a first solvent that is a good solvent for any of the second polymers and a poor solvent for the remaining polymer; and forming a sheet from the paste. Immersing the sheet in a second solvent that is compatible with the first solvent, and wherein the first solvent is a poor solvent for the polymer as a good solvent, thereby forming the first solvent and the second solvent. It is manufactured by a method including a step of replacing the second solvent and a step of evaporating the second solvent in the sheet.
The method for making the porous body is not limited to the above method, and any conventionally used method such as stretching and use of a foaming agent may be used.

A non-aqueous secondary battery according to the present invention is a non-aqueous secondary battery including a positive electrode, a negative electrode, and a gel electrolyte layer disposed between the positive electrode and the negative electrode. Impregnating a non-aqueous electrolyte with a porous gel electrolyte layer precursor containing a first polymer that is hardly soluble in the non-aqueous electrolyte and a second polymer having a property of gelling the non-aqueous electrolyte, and heating Characterized by being cooled.

[0011] The method for producing a non-aqueous secondary battery according to the present invention comprises:
A porous gel electrolyte layer precursor including a first polymer that is hardly soluble in a non-aqueous electrolyte and a second polymer having a property of gelling the non-aqueous electrolyte is interposed between a positive electrode and a negative electrode. A step of producing an electrode group, and a step of impregnating the electrode group with a non-aqueous electrolyte, heating and cooling to obtain a gel electrolyte layer from the gel electrolyte layer precursor. Is what you do.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a non-aqueous secondary battery according to the present invention will be described.

This non-aqueous secondary battery includes an exterior material and an electrode group housed in the exterior material. The electrode group includes:
A positive electrode, a negative electrode, and a gel electrolyte layer disposed between the positive electrode and the negative electrode. The gel electrolyte layer is formed by adding a non-aqueous electrolyte to a porous gel electrolyte layer precursor containing a first polymer which is hardly soluble in a non-aqueous electrolyte and a second polymer having a property of gelling the non-aqueous electrolyte. It is impregnated, heated and cooled.

Next, the positive electrode, the negative electrode, the gel electrolyte layer, and the packaging material will be described.

1) Positive Electrode The positive electrode is formed of a current collector in which a positive electrode layer containing an active material and a conductive material is supported.

Examples of the 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 nickel oxide such as LiCoO ₂ , for example). Examples thereof include cobalt oxide, lithium-containing cobalt nickel oxide, amorphous vanadium pentoxide containing lithium, and chalcogen compounds (for example, titanium disulfide, molybdenum disulfide, and the like). Among them, it is preferable to use a lithium manganese composite oxide, a lithium-containing cobalt oxide, and a lithium-containing nickel oxide.

As the current collector, for example, aluminum expanded metal, aluminum foil, aluminum mesh, aluminum punched metal and the like can be used.

Examples of the conductive material include artificial graphite, carbon black (eg, acetylene black), nickel powder, and the like.

The positive electrode is prepared by, for example, preparing a slurry by kneading a positive electrode active material, a conductive material and a binder in the presence of a solvent, applying the slurry to a current collector, drying, and pressing It is produced by performing molding.

Examples of the binder include polyvinylidene fluoride, styrene / butadiene copolymer, carboxymethyl cellulose and derivatives thereof.

Further, a polymer having a binding function and a function of retaining a non-aqueous electrolyte may be added to the positive electrode layer instead of the binder. Examples of such a polymer include a polyethylene oxide derivative, a polypropylene oxide derivative, a polymer containing the derivative, a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), and a polyacrylonitrile derivative.

2) Negative Electrode The negative electrode is formed of a negative electrode layer containing an active material supported on a current collector.

As the active material, for example, a carbonaceous material that stores and releases lithium ions can be used. 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. Above all, it is preferable to use a carbonaceous material obtained by firing the mesophase pitch at a temperature of 500 to 3000 ° C. under normal pressure or reduced pressure.

As the current collector, for example, copper expanded metal, copper foil, copper mesh, copper punched metal and the like can be used.

The negative electrode includes artificial graphite, natural graphite, carbon black, acetylene black,
Ketjen black, nickel powder, conductive materials of polyphenylene derivatives, and fillers such as olefin polymers and carbon fibers are allowed.

The negative electrode is prepared, for example, by preparing a slurry by kneading a negative electrode active material and a binder in the presence of a solvent, applying the slurry to a current collector, drying the slurry, and then press-molding the same. It is produced by

Examples of the binder include those similar to those described above for the positive electrode.

Further, a polymer having a binding function and a function of retaining a non-aqueous electrolyte may be added to the negative electrode layer instead of the binder. Examples of such a polymer include those similar to those described above for the positive electrode.

3) Gel Electrolyte Layer The gel electrolyte layer is a porous gel electrolyte layer containing a first polymer which is hardly soluble in a non-aqueous electrolyte and a second polymer which has a property of gelling the non-aqueous electrolyte. The precursor is impregnated with a non-aqueous electrolyte, the non-aqueous electrolyte is gelled by heating, and then cooled.

The gel electrolyte layer precursor is produced, for example, by the method described below.

First, the first polymer and the second polymer are mixed with a first solvent A which is a good solvent for the first polymer and a poor solvent for the second polymer.
To prepare a paste. A sheet is prepared from the obtained paste by casting. As shown in FIG. 1A, the obtained sheet is a mixture (P ₁ + A) of the first polymer P ₁ and the first solvent A.
Has a configuration in which the _second polymer P ₂ is dispersed.

As shown in the FIG. 1 (b), the sheet, is compatible with the first solvent A, and a second solvent B is a poor solvent for the first polymer P ₁ Immerse.
As a result, the solvent A and the solvent B in the sheet are replaced. No.
Since the solubility of the polymer P ₁ in the solvent B is low, the polymer P ₁ is precipitated as the replacement of the solvent A with the solvent B proceeds.

After the replacement of the solvent A with the solvent B is completed, the solvent B is evaporated. As shown in FIG. 1 (c), because the evaporated portion of the solvent B becomes void C, and the first polymer P ₁ and a second polymer P ₂ as a main component, the first polymer P ₁ region porous A gel electrolyte layer precursor having a porous structure is obtained.

When polyvinylidene fluoride (PVdF) is used as the first polymer, N-methyl-2-pyrrolidone (NMP), N,
N-dimethylformamide (DMF) can be used, while the second solvent B can be water, methanol, ethanol, or the like.

When a polyolefin copolymer such as an ethylene-vinyl acetate copolymer is used as the first polymer, toluene, tetrahydrofuran, methyl ethyl ketone or the like can be used as the first solvent A, On the other hand, water, methanol, ethanol, or the like can be used as the second solvent B.

The first polymer and the second polymer are mixed with a first solvent D which is a good solvent for the second polymer and a poor solvent for the first polymer.
A paste is prepared by kneading in the presence of, and a sheet is prepared by casting. Then, the sheet is compatible with the first solvent D, and a second solvent which is a poor solvent for the second polymer. When the solvent E is evaporated after dipping in the solvent E, it is possible to obtain a gel electrolyte layer precursor in which the second polymer region has a porous structure.

The first polymer forms a skeleton in the gel electrolyte layer, and contributes to improving the mechanical strength of the gel electrolyte layer. Further, it is preferable that the first polymer can minimize the inhibition of ionic conductivity. Therefore, it is desirable that the first polymer has a property of swelling in the non-aqueous electrolyte, though it hardly dissolves in the non-aqueous electrolyte. Examples of the first polymer having such properties include a polyolefin copolymer, polyvinylidene fluoride (PVdF), and the like.
As the first polymer, one type or two or more types selected from the types described above can be used.
Examples of the polyolefin copolymer include ethylene-
Examples thereof include a vinyl acetate copolymer, an ethylene-methyl methacrylate copolymer, and an ethylene-ethyl acrylate copolymer. Among them, PVdF is preferable because it has high resistance to an electrolytic solution and has a small barrier for ion transfer.

The first polymer preferably has a swelling degree described below of 30% by mass or less. If the degree of swelling exceeds 30%, the property of being hardly soluble in the non-aqueous electrolyte may be impaired, and the gel electrolyte may not be able to contribute to the improvement of the mechanical strength. In particular, the degree of swelling is preferably in the range of 8 to 20% by mass. By setting the swelling degree in such a range, both the ionic conductivity and the mechanical strength of the gel electrolyte layer can be further improved.

That is, the polymer to be measured is dissolved in a solvent and cast, and the volume is 2 × 2 × 0.1
A test sheet (cm ³ ) is prepared. LiBF ₄ was added to a solvent in which ethylene carbonate and γ-butyrolactone were mixed at a volume ratio of 1: 3, and the concentration of LiBF ₄ was 1.0 m.
ol / l to prepare a test electrolyte solution. The test sheet is immersed in a test electrolyte at 25 ° C. for 24 hours. After immersion, excess electrolyte (free electrolyte) irrelevant to the swelling of the test sheet is wiped off. Then, the weight W ₁ of the test sheets was measured to calculate the following (1) swelling ratio of the polymer from the equation (%).

Swelling ratio (%) of polymer = {(W ₁ −W ₀ ) / W ₁ } × 100 (1) In the equation (1), W ₁ is the weight (g) of the test sheet after the immersion test. , W ₀ represents the weight (g) of the test sheet before the immersion test.

The first polymer is more preferably a thermoplastic resin in addition to the property of swelling in the non-aqueous electrolyte. An application step for forming a gel electrolyte layer by forming the first polymer from a thermoplastic resin;
The rolling process and the stretching process can be easily performed. At the same time, the gel electrolyte layer can be made from a polymer blend. Has the property of swelling in non-aqueous electrolyte,
Examples of the first polymer which is a thermoplastic resin include polyolefin copolymers (eg, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer), polyvinylidene Fluoride (PVdF) and the like can be mentioned. As the first polymer, one type or two or more types selected from the types described above can be used.

The second polymer is, for example, polyethylene oxide (PEO) and its derivatives, polypropylene oxide (PPO) and its derivatives, a copolymer of vinylidene fluoride and hexafluoropropylene (PVdF-HFP), and polyacrylonitrile ( P
AN) and at least one polymer selected from the group consisting of derivatives thereof. In particular,
Polyacrylonitrile (PAN) and its derivatives, which can fix many electrolytes with a small amount of polymer, are desirable. Examples of the PAN derivative include a copolymer containing acrylonitrile as a monomer component. Examples of the copolymer containing acrylonitrile as a monomer component include an acrylonitrile-vinyl acetate copolymer, an acrylonitrile-methyl acrylate copolymer, and an acrylonitrile-ethyl acrylate copolymer. Further, SAN, ABS and the like, which are rubbers containing acrylonitrile, may be mentioned.

Preferably, the first polymer and the second polymer are incompatible and form a sea-island structure in the gel electrolyte layer.

The volume ratio of the first polymer to the second polymer is in the range of 0.1 to 5 (the volume of the second polymer is V ₂ and the volume of the first polymer is V ₁ . In this case, it is preferably calculated as V ₁ / V ₂ ). This is due to the following reasons. The skeleton of the gel electrolyte layer is mainly formed from the first polymer. Also,
The second polymer mainly contributes to the ion conduction of the gel electrolyte layer. Further, the second polymer has a role of suppressing volatilization of the non-aqueous electrolyte. The non-aqueous electrolyte is held by the first polymer and the second polymer. When the volume ratio is less than 0.1, the mechanical strength of the gel electrolyte layer is reduced, and an internal short circuit is likely to occur. Also,
Handling during battery manufacture may be poor. On the other hand, when the volume ratio exceeds 5, the ionic conductivity of the gel electrolyte layer is reduced, the internal impedance of the secondary battery is increased, and a high rate characteristic may not be obtained. A more preferable range of the volume ratio is 0.4 to 2.5.

The volume ratio of the first polymer to the second polymer in the gel electrolyte layer in the non-aqueous secondary battery is measured, for example, by the method described below.

First, the secondary battery is disassembled, and the gel electrolyte layer is taken out. Solvent extraction from this gel electrolyte layer
For example, acetone, ethanol, and water are used) to extract the electrolyte solution and take out the polymer component. The obtained polymer components are separated by utilizing the difference in solubility in a solvent, and the abundance ratio of each component is identified. Thereafter, infrared absorption (IR), nuclear magnetic resonance (NMR), paramagnetic resonance (E
Each polymer component is identified by an analytical instrument such as SR) and differential scanning calorimetry (DSC). From these results, the volume ratio of the first polymer to the second polymer can be determined.

The non-aqueous electrolyte comprises an electrolyte such as a lithium salt dissolved in a non-aqueous solvent.

Examples of the non-aqueous solvent include ethylene carbonate (EC) and propylene carbonate (P
C), butylene carbonate (BC), dimethyl carbonate (DMC), 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 in combination of two or more.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ) and lithium hexafluorophosphate (L
iPF _6), lithium borofluoride (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.

In order to further improve the strength of the gel electrolyte layer, an inorganic filler such as crystalline silica or fused silica, and a core material such as a nonwoven fabric or a microporous film are added when preparing the gel electrolyte layer precursor. You may.

4) Exterior Material Examples of the exterior material include a sheet in which a metal layer is interposed between a thermoplastic resin layer and a resin layer.

The thermoplastic resin layer serves as a heat sealing surface of the exterior material. Examples of the heat-fusible resin include modified polyethylene phthalate, acid-modified polyethylene, acid-modified polypropylene, ionomer, ethylene vinyl acetate (EVA) and the like. The thermoplastic resin layer may have a single layer or a multilayer structure composed of a plurality of thermoplastic resins.

The metal layer plays a role in preventing moisture from entering. The metal layer can be formed from, for example, aluminum, nickel, and stainless steel.

The resin layer has a role of protecting the metal layer. The resin layer can be formed from, for example, polyolefin such as polyethylene terephthalate (PET) and polypropylene. The resin layer,
It can be a single layer or a multilayer structure composed of a plurality of resins.

FIGS. 2 and 3 show an example of the non-aqueous secondary battery according to the present invention.

That is, the non-aqueous secondary battery has an electrode group mainly composed of a positive electrode 1, a negative electrode 2, and a gel electrolyte layer 3 disposed between the positive electrode 1 and the negative electrode 2. Is provided. The positive electrode 1 includes a porous current collector 4 and a positive electrode layer 5 supported on both surfaces of the current collector 4. On the other hand, the negative electrode 2 includes a porous current collector 6 and a negative electrode layer 7 supported on both surfaces of the current collector 6. The band-shaped positive terminal 8 is
The current collector 4 of each positive electrode 1 is extended in a belt shape.
On the other hand, the strip-shaped negative electrode terminal 9 is obtained by extending the current collector 6 of the negative electrode 2 in a strip shape. For example, a positive electrode lead 10 made of a strip-shaped aluminum plate is connected to the two positive electrode terminals 8. For example, the negative electrode lead 11 made of a strip-shaped copper plate
Is connected to the negative electrode terminal 9. The electrode group having such a configuration is hermetically sealed in a state in which the positive electrode lead 10 and the negative electrode lead 11 extend from the exterior material 12 within the exterior material 12.

The non-aqueous secondary battery according to the present invention described above includes a positive electrode, a negative electrode, and a gel electrolyte layer disposed between the positive electrode and the negative electrode. The gel electrolyte layer is formed by adding a non-aqueous electrolyte to a porous gel electrolyte layer precursor containing a first polymer which is hardly soluble in a non-aqueous electrolyte and a second polymer having a property of gelling the non-aqueous electrolyte. It is impregnated, heated and cooled.

According to such a secondary battery, the amount of the non-aqueous electrolyte impregnated in the gel electrolyte layer precursor can be increased, so that the ionic conductivity of the gel electrolyte layer can be improved and the internal resistance can be improved. Can be lowered. For this reason, it is possible to suppress a decrease in capacity at the time of discharging at a high rate, and to improve the charge and discharge efficiency and improve the cycle life. Further, since the gel electrolyte layer contains the first polymer, mechanical strength can be improved,
Internal short circuit can be suppressed, and the reliability of the secondary battery can be improved. Further, according to the present invention, the electrode group can be prepared by interposing the non-aqueous electrolyte-free gel electrolyte layer precursor between the positive electrode and the negative electrode. When handling, there is no need to control the moisture in the atmosphere, and the manufacture of the secondary battery can be simplified.

In the secondary battery according to the present invention, by forming the first polymer region of the gel electrolyte layer precursor to have a porous structure, the first polymer region is formed in the gap as compared with the case where the second polymer region is made porous. Since the non-aqueous electrolyte is easily held, the amount of the non-aqueous electrolyte held by the precursor can be increased. As a result, the rate characteristics of the secondary battery can be further improved.

In the secondary battery according to the present invention, the second battery
The volume ratio of the first polymer to the polymer is 0.1.
By setting it within the range of 1 to 5, the balance between the mechanical strength and the ionic conductivity of the gel electrolyte layer can be optimized. As a result, the rate characteristics and cycle life of the secondary battery can be further improved, and the internal short-circuit occurrence rate can be reduced to further improve the reliability of the secondary battery. Further, handling during the battery manufacturing process can be improved.

[0062]

Embodiments of the present invention will be described below in detail.

(Example 1) (Preparation of positive electrode) N-methyl-2-pyrrolidone was composed of 88% by mass of LiCoO ₂ , 7% by mass of acetylene black, and 5% by mass of polyvinylidene fluoride as a binder. A paste was prepared by dispersing. The obtained paste was applied to a current collector made of aluminum foil having a thickness of 20 μm by a doctor blade method to have a thickness of 100 μm and a width of 150 mm.
Was applied to form a sheet, and cut into a length of 150 mm to produce a positive electrode.

(Preparation of Negative Electrode) A paste was prepared by dispersing 95% by mass of mesophase pitch carbon fiber and 5% by mass of polyvinylidene fluoride as a binder in N-methyl-2-pyrrolidone. The obtained paste was applied to a current collector made of a copper foil having a thickness of 12 μm by a doctor blade method so as to have a thickness of 100 μm and a width of 150 mm, formed into a sheet, and cut into a length of 160 mm to produce a negative electrode. .

(Preparation of Gel Electrolyte Layer Precursor) Polyvinylidene fluoride powder (PVd
F) and a mixed powder composed of polyacrylonitrile powder (PAN) as the second polymer {the volume ratio (volume ratio of the first polymer to the second polymer) is 2}, and a solvent composed of N-methyl-2-pyrrolidone A was prepared by mixing A. A sheet was obtained from the obtained paste by casting.

After the sheet is immersed in a solvent B composed of water to replace the solvent A with the solvent B, the solvent B is evaporated to form a gel electrolyte layer precursor having a porous PVdF region. Produced.

The swelling ratio of the first polymer was measured by the method described below. 20 parts by mass of PVdF powder was N-
It is dissolved in 80 parts by mass of a solvent composed of methyl-2-pyrrolidone and cast, and the volume is 2 × 2 × 0.1 (c
m ³ ) was prepared. The obtained test sheet was immersed in the above-mentioned test electrolyte at 25 ° C. for 24 hours. After immersion, excess electrolyte (free electrolyte) irrelevant to the swelling of the test sheet was wiped off. Next, the weight W _{1 of the} test sheet was measured, and the swelling ratio (%) of the polymer was obtained from the above-described formula (1).
As a result, the swelling ratio was 16%.

(Preparation of Non-Aqueous Electrolyte Solution) LiBF ₄ has a concentration of 1 mol / L in a non-aqueous solvent obtained by mixing ethylene carbonate (EC) and γ-butyrolactone (BL) at a volume ratio of 1: 3. To prepare a non-aqueous electrolyte solution.

(Assembly and Activation of Battery) The obtained positive electrode and negative electrode were laminated with a gel electrolyte layer precursor interposed therebetween to prepare an electrode group. The obtained electrode group was inserted into a bag made of a laminate film composed of a thermoplastic resin layer / aluminum foil / resin layer, dried under vacuum at 80 ° C. for 12 hours, and then injected with the nonaqueous electrolyte under an argon atmosphere. . Subsequently, the positive electrode terminal and the negative electrode terminal were sealed by heating and pressure bonding in a state of protruding outside the bag. The assembled non-aqueous electrolyte is gelled by sandwiching the assembled secondary battery between metal plates at 100 ° C. for 3 minutes, then cooled at −20 ° C. for 2 hours and returned to room temperature to release the sea-island from the gel electrolyte layer precursor. A gel electrolyte layer having a structure was obtained, and a non-aqueous secondary battery having a designed capacity of 100 mAh was manufactured.

The obtained secondary battery has a capacity of 0.
Activation was performed by applying a constant current-constant voltage charge at a current of 2 CmA and a final voltage of 4.2 V.

(Examples 2 to 6) The first example, the second polymer, and the examples described above, except that the volume ratio of the first polymer to the second polymer was changed as shown in Table 1 below A non-aqueous secondary battery was produced in the same manner as in Example 1.

(Comparative Example 1) In a dry environment in an argon atmosphere, polyacrylonitrile powder (PAN) as a second polymer was dissolved in the same nonaqueous electrolyte solution as in Example 1 described above, and this was cooled to form a gel. An electrolyte was prepared.

In the dry environment, the same positive electrode and negative electrode as described in Example 1 were laminated with the non-aqueous electrolyte layer interposed therebetween to prepare an electrode group. After inserting the obtained electrode group into a bag made of the same laminated film as described in Example 1, the positive electrode terminal and the negative electrode terminal were sealed by heating and pressing in a state of protruding outside the bag,
A non-aqueous secondary battery having a designed capacity of 100 mAh was manufactured.

(Comparative Example 2) In a dry environment in an argon atmosphere, polyvinylidene fluoride powder (PVdF) as a first polymer was dissolved in the same nonaqueous electrolyte solution as in Example 1 described above, and this was cooled. To prepare a gel electrolyte.

In the dry environment, the same positive electrode and negative electrode as described in Example 1 were laminated with the non-aqueous electrolyte layer interposed therebetween to produce an electrode group. After inserting the obtained electrode group into a bag made of the same laminated film as described in Example 1, the positive electrode terminal and the negative electrode terminal were sealed by heating and pressing in a state of protruding outside the bag,
A non-aqueous secondary battery having a designed capacity of 100 mAh was manufactured.

With respect to the obtained secondary batteries of Examples 1 to 6 and Comparative Examples 1 and 2, the number of internal short-circuits generated when 100 secondary batteries were assembled was measured. The results are shown in Table 2 below.

The internal resistance of the secondary batteries of Examples 1 to 6 and Comparative Examples 1 and 2 was measured at 1 kHz, and the results are shown in Table 2 below.

Further, with respect to the secondary batteries of Examples 1 to 6 and Comparative Examples 1 and 2, 0.2 CmA at 20.degree.
The discharge capacity at the time of discharging to a final voltage of 3.0 V at a current of 0 CmA and 2.0 CmA was measured. The discharge capacity at 1.0 C and 2.0 C is represented by setting the discharge capacity at 0.2 C as 100%, and the results are also shown in Table 2 below.

[0079]

[Table 1]

[0080]

[Table 2]

As is clear from Tables 1 and 2, a porous gel electrolyte layer precursor containing a first polymer which is hardly soluble in a non-aqueous electrolyte and a second polymer which has a property of gelling the non-aqueous electrolyte. The non-aqueous electrolyte is impregnated in the body, the non-aqueous electrolyte is gelled by heating, and the secondary batteries of Examples 1 to 6 including the cooled gel electrolyte layer can prevent an internal short circuit during assembly. It can be seen that the internal resistance can be reduced, and the decrease in discharge capacity when discharging at a high rate can be suppressed. Further, by comparing the secondary batteries of Examples 1 to 3, it can be seen that as the volume ratio of the first polymer to the second polymer increases, the internal resistance increases and the rate characteristics decrease.

On the other hand, the secondary battery of Comparative Example 1 provided with the non-aqueous electrolyte layer prepared from the second polymer and the non-aqueous electrolyte solution has the internal short-circuit occurrence number of the secondary batteries of Examples 1 to 6. It turns out that there are many compared with. On the other hand, the secondary battery of Comparative Example 2 including the nonaqueous electrolyte layer prepared from the first polymer and the nonaqueous electrolyte has higher internal resistance than the secondary batteries of Examples 1 to 6, and furthermore It can be seen that the discharge capacity decreases when discharging at a high rate. Furthermore, according to Comparative Examples 1 and 2, since the non-aqueous electrolyte layer already containing the non-aqueous electrolyte layer is interposed between the positive electrode and the negative electrode to form an electrode group, handling of the non-aqueous electrolyte layer is complicated. In addition, the atmosphere for forming the electrode group must be a dry atmosphere.

[0083]

As described above in detail, according to the present invention, it is possible to provide a gel electrolyte precursor capable of improving the reliability, rate characteristics and cycle life of a non-aqueous secondary battery. Further, according to the present invention, it is possible to provide a non-aqueous secondary battery and a method of manufacturing a non-aqueous secondary battery with improved reliability, rate characteristics, and cycle life.

[Brief description of the drawings]

FIG. 1 is a schematic view for explaining a method for producing a gel electrolyte precursor according to the present invention.

FIG. 2 is a plan view showing an example of a non-aqueous secondary battery according to the present invention.

FIG. 3 is a sectional view showing the non-aqueous secondary battery of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Positive electrode, 2 ... Negative electrode, 3 ... Gel electrolyte layer, 4 ... Positive electrode collector, 5 ... Positive electrode layer, 6 ... Negative electrode current collector, 7 ... Negative electrode layer, 12 ... Exterior material.

Continued on front page (72) Inventor Koji Kano 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation F-term (reference) 4F074 AA17 AA22 AA38 AA49 AA76 CB44 CB45 CC04Y CC22Y CC29Z DA49 5H029 AJ02 AJ14 AK03 AL07 AL08 AM03 AM04 AM05 AM07 AM16 CJ02 CJ13 EJ12

Claims (5)

[Claims] 1. A gel electrolyte precursor containing a first polymer which is hardly soluble in a non-aqueous electrolyte and a second polymer having a property of gelling the non-aqueous electrolyte is impregnated with the non-aqueous electrolyte. A gel electrolyte precursor for obtaining a gel electrolyte by heating and then cooling, wherein the gel electrolyte precursor has a porous structure. 2. The gel electrolyte precursor according to claim 1, wherein the first polymer region has a porous structure. 3. The gel electrolyte precursor according to claim 1, wherein a volume ratio of the first polymer to the second polymer is in a range of 0.1 to 5. 4. A non-aqueous secondary battery including a positive electrode, a negative electrode, and a gel electrolyte layer disposed between the positive electrode and the negative electrode, wherein the gel electrolyte layer has poor solubility in a non-aqueous electrolyte. A porous gel electrolyte layer precursor containing the first polymer and the second polymer having a property of gelling the non-aqueous electrolyte is impregnated with the non-aqueous electrolyte, heated and cooled. Non-aqueous secondary battery. 5. A porous gel electrolyte layer precursor containing a first polymer that is hardly soluble in a non-aqueous electrolyte and a second polymer having a property of gelling the non-aqueous electrolyte is used as a positive electrode and a negative electrode. A step of preparing an electrode group by interposing the electrode group therebetween; and a step of impregnating the electrode group with a non-aqueous electrolyte, heating and cooling to obtain a gel electrolyte layer from the gel electrolyte layer precursor. A method for producing a non-aqueous secondary battery.