JP2003157891A - Method of manufacturing nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a nonaqueous secondary battery superior in liquid leakage resistance, reducing internal resistance, and having high initial capacity and rate characteristic. SOLUTION: This manufacturing method is characterized by having a process of preparing paste including a first solvent being a good solvent to either one solute of a refractory polymer or a gelling agent, a process of forming a gel electrolyte precursor layer by using the paste on at least one electrode of a positive electrode and a negative electrode, a process of substituting at least a part of the first solvent with a second solvent by soaking the gel electrolyte precursor layer in the second solvent being compatible with the first solvent, and being an incompatible solvent to the one solute, a process of volatilizing the second solvent in the gel electrolyte precursor layer, a process of manufacturing an electrode group by using the electrode forming the gel electrolyte precursor layer, and a process of impregnating a nonaqueous electrolyte into the electrode group.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of manufacturing 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 and lightweight, has a high energy density, and can be repeatedly charged and discharged. As such a secondary battery, a negative electrode using lithium or a lithium alloy as an active material, a positive electrode containing an oxide such as molybdenum, vanadium, titanium or niobium, a sulfide or selenide as an active material, and a non-aqueous electrolyte solution. There is known a non-aqueous electrolyte secondary battery including:

Further, in place of the negative electrode using lithium or a lithium alloy as an active material, a carbonaceous material which absorbs and releases lithium ions (for example, coke, graphite, carbon fiber, resin fired body, pyrolysis vapor phase carbon) 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 dendride deposition is improved, and cycle life and safety are higher than those of a secondary battery including a negative electrode containing lithium or a lithium alloy as an active material.

In such a non-aqueous electrolyte secondary battery, the non-aqueous electrolyte is only impregnated in the electrode group, but in order to further improve safety and facilitate thinning and weight reduction. Therefore, it has been attempted to hold the nonaqueous electrolytic solution in the polymer (for example, JP-A-11-67273).
Issue publication). However, the lithium secondary battery disclosed in the above publication has insufficient liquid leakage resistance and rate characteristics.

Further, it has been considered that a separator containing insulating fine particles and a binder is formed on an electrode by coating to make the separator into a thin film (for example, Japanese Unexamined Patent Publication No. 10-223195). However, the one using such a separator is not substantially different from the conventional non-aqueous secondary battery, and there is a problem from the viewpoint of liquid leakage resistance even if it is made thin.

On the other hand, JP-A-2000-149906 discloses a non-electrically conductive powder such as silica, a non-electrically conductive binder such as polyvinylidene fluoride and a solvent such as N-methylpyrrolidone. Prepare a paint containing
A lithium secondary battery in which a coating material is applied onto the positive electrode and / or the negative electrode and dried to form a separator, which is then impregnated with an electrolyte solution containing a non-aqueous electrolyte solution and a gelling agent to gelate the electrolyte solution. A manufacturing method is disclosed.

[0007]

According to such a manufacturing method, although the solvent is volatilized in the drying step for forming the separator to form voids in the separator, the solvent is mixed with the powder and the binder. Since it is a good solvent, it is difficult to volatilize and the size of the voids is small, so that it becomes difficult to sufficiently enhance the permeability of the electrolyte solution in the separator. Moreover, since the electrolytic solution contains a gelling agent, gelation starts during the impregnation of the electrolytic solution into the separator. As a result, since the distribution of the gel electrolyte in the separator is biased, the initial capacity of the secondary battery becomes low.
After that, even if the charge / discharge cycle is repeated, the distribution of the gel electrolyte in the separator remains biased and hardly changes, so that the rate characteristics and other charge / discharge characteristics such as the charge / discharge cycle also become inferior.

It is an object of the present invention to provide a method for manufacturing a non-aqueous secondary battery which has excellent leakage resistance, low internal resistance and high initial capacity and rate characteristics.

[0009]

The method for producing a non-aqueous secondary battery according to the present invention comprises a sparingly soluble polymer which is sparingly soluble in a non-aqueous electrolyte, a gelling agent for gelling the non-aqueous electrolyte, and A step of preparing a paste containing a poorly soluble polymer and a first solvent that is a good solvent for a solute of any one of the gelling agent, and the paste on at least one of the positive electrode and the negative electrode And a step of forming a gel electrolyte precursor layer using the above, and the gel electrolyte precursor layer is immersed in a second solvent that is compatible with the first solvent and is a poor solvent for the one solute. The step of substituting at least a part of the first solvent with the second solvent, the step of volatilizing the second solvent in the gel electrolyte precursor layer, and the gel electrolyte precursor layer being formed. And the process of making an electrode group using the electrodes Impregnating the non-aqueous electrolyte solution in the electrode group, the gel electrolyte precursor layer in the electrode group is characterized in that it comprises the step of a by gelling the gel electrolyte layer.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a method for manufacturing a non-aqueous secondary battery according to the present invention will be described below.

(First step) A polymer which is hardly soluble in the non-aqueous electrolyte, a gelling agent which gelates the non-aqueous electrolyte, and a solute of any one of the poorly soluble polymer and the gelling agent. On the other hand, a paste containing a first solvent which is a good solvent is prepared.

The sparingly soluble polymer can enhance the mechanical strength of the gel electrolyte layer. Examples of such sparingly soluble polymers include polyolefin copolymers such as ethylene-vinyl acetate copolymer, polyvinylidene fluoride (PVdF), and copolymers containing vinylidene fluoride units. As the poorly soluble polymer, one kind or two or more kinds selected from the above-mentioned kinds can be used.

As the gelling agent, a physical gelling agent that gels the non-aqueous electrolytic solution by utilizing physical interaction between polymers, or a gelling agent of the non-aqueous electrolytic solution by utilizing a crosslinking reaction or a polymerization reaction Chemical gelling agents and the like can be used. As the physical gelling agent, for example, polyethylene oxide, polypropylene oxide, a copolymer containing an alkylene oxide unit, polyacrylonitrile, polyvinylidene fluoride, a copolymer containing a vinylidene fluoride unit, a copolymer containing a carbonyl group, etc. Can be mentioned. On the other hand, as the chemical gelling agent, for example,
A monomer, an oligomer, a polymer or the like having a polymerizable or crosslinkable functional group represented by an acryloyl group or an epoxy group can be used, and specific examples thereof include a cyano group-containing copolymer. The type of gelling agent used may be one type or two or more types. It is preferable to use a physical gelling agent because the reactivity of the chemical gelling agent is likely to decrease in the paste and gelation may not easily occur during the gelling step described below.

The volume ratio of the sparingly soluble polymer to the gelling agent is in the range of 0.1 to 5 (where V ₂ is the volume of the gelling agent and V ₁ is the volume of the sparingly soluble polymer, V is ₁ /
Is calculated by V ₂₎ it is preferred. This is due to the following reasons. The skeleton of the gel electrolyte layer is mainly
It is formed from the poorly soluble polymer. Further, the gelling agent mainly contributes to the ionic conduction of the gel electrolyte layer.
Furthermore, the gelling agent can suppress volatilization of the non-aqueous electrolyte. The non-aqueous electrolyte is retained by the sparingly soluble polymer and the gelling agent. When the volume ratio is less than 0.1, the mechanical strength of the gel electrolyte layer is lowered, and an internal short circuit is likely to occur. On the other hand, when the volume ratio exceeds 5, the ionic conductivity of the gel electrolyte layer decreases, the internal impedance of the secondary battery increases, and high rate characteristics may not be obtained. The more preferable range of the volume ratio is 0.4 to
It is 2.5.

The first solvent is preferably a good solvent for the solute of one of the poorly soluble polymer and the gelling agent and a poor solvent for the other solute.
By using such a first solvent, phase separation between the solute and the second solvent can be promoted, so that the impregnation rate of the non-aqueous electrolyte solution in the gel electrolyte layer can be further increased. Also, the first
The solvent is preferably a good solvent for the poorly soluble polymer. When the first solvent is used, the poorly soluble polymer region can be predominantly made porous, so that the impregnation speed of the non-aqueous electrolyte solution in the gel electrolyte layer can be further increased.

When polyvinylidene fluoride (PVdF) is used as the sparingly soluble polymer, the first solvent is N-methyl-2-pyrrolidone (NMP), which is a good solvent for PVdF, or N, N-dimethyl. Formamide (D
It is desirable to use MF). On the other hand, when a polyolefin copolymer such as ethylene-vinyl acetate copolymer is used as the poorly soluble polymer, the first solvent is
Toluene, tetrahydrofuran, methyl ethyl ketone, etc., which are good solvents for the polyolefin copolymer, can be used.

From the viewpoint of improving the mechanical strength of the gel electrolyte layer and reducing the short circuit ratio between the positive electrode and the negative electrode, it is desirable to add a reinforcing material to the paste. The stiffener is preferably formed from an electrochemically inert material. Specific examples include inorganic fillers such as silicon oxide, aluminum oxide and titanium oxide, and organic fillers such as polyethylene, polypropylene and polyethylene terephthalate.

(Second Step) A gel electrolyte precursor layer is formed on at least one of the positive electrode and the negative electrode using the paste.

The gel electrolyte precursor layer may be formed by any method as long as the gel electrolyte precursor layer can be directly formed on the electrode, for example, spin coating method, dipping method, cast method. The method, the doctor blade method, the gravure coating method, the roll coating method, the screen printing method, the spray coating method and the like can be adopted. According to the method of applying the paste on the electrode, the polymer component and the gelling agent can be permeated into the voids of the electrode, so that the adhesion between the electrode and the gel electrolyte layer can be improved, and the inside of the secondary battery can be improved. The resistance can be reduced. The gel electrolyte precursor layer may be formed on either the positive electrode or the negative electrode, but is preferably formed on both the positive electrode and the negative electrode from the viewpoint of reducing internal resistance and preventing pinholes.

Next, the positive electrode and the negative electrode will be described.

1) Positive Electrode This positive electrode is formed of a current collector carrying a positive electrode layer containing an active material and a conductive material.

Examples of the active material include various oxides (eg, lithium manganese composite oxides such as LiMn ₂ O ₄ , manganese dioxide, lithium-containing nickel oxides such as LiNiO _2, and lithium-containing oxides such as LiCoO _2). Cobalt oxides, lithium-containing cobalt nickel oxides, lithium-containing amorphous vanadium pentoxide, etc.), chalcogen compounds (eg, titanium disulfide, molybdenum disulfide, etc.) and the like. Above all, it is preferable to use lithium manganese composite oxide, lithium-containing cobalt oxide, and lithium-containing nickel oxide.

As the current collector, for example, aluminum expanded metal, aluminum foil, aluminum mesh, aluminum punched metal or 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, kneading a positive electrode active material, a conductive material and a binder in the presence of a solvent to prepare a slurry, applying the slurry to a current collector, drying and then pressing. It is produced by molding.

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

Further, instead of the binder, a polymer having a binding function and a function of holding the non-aqueous electrolyte may be added to the positive electrode layer. As such a polymer, for example, a polyethylene oxide derivative, a polypropylene oxide derivative, a polymer containing the above derivative, a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), a polyacrylonitrile derivative, or the like can be used.

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

Examples of the active material include a carbonaceous material that absorbs and releases lithium ions. Examples of such carbonaceous materials include those obtained by firing an organic polymer compound (for example, phenol resin, polyacrylonitrile, cellulose, etc.), those obtained by firing coke and mesophase pitch, and artificial graphite. , 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 or the like can be used.

For the negative electrode, artificial graphite, natural graphite, carbon black, acetylene black,
Ketjen black, nickel powder, conductive material of polyphenylene derivative, filler such as olefin polymer and carbon fiber are allowed to be contained.

For the negative electrode, for example, a slurry is prepared by kneading a negative electrode active material and a binder in the presence of a solvent, and the slurry is applied to a current collector, dried, and then press-molded. It is produced by.

As the above-mentioned binder, the same binder as described above for the positive electrode can be mentioned.

Further, instead of the binder, a polymer having a binding function and a function of holding the non-aqueous electrolyte may be added to the negative electrode layer. As such a polymer, the same polymers as those described for the positive electrode can be used.

(Third Step) In a second solvent which is compatible with the first solvent and is a poor solvent for the one solute,
The gel electrolyte precursor layer is immersed, and at least a part of the first solvent is replaced with the second solvent.

When the one solute is a poorly soluble polymer, water, methanol, ethanol or the like can be used as the second solvent.

(Fourth Step) The second solvent in the gel electrolyte precursor layer is volatilized.

(Fifth Step) An electrode group is prepared using the electrodes on which the gel electrolyte precursor layer is formed.

The electrode group includes a laminate including a positive electrode, a negative electrode, and a gel electrolyte precursor layer disposed between the positive electrode and the negative electrode, and a structure in which the laminate is spirally or flatly wound. Examples thereof include those having a structure in which the laminate is folded, and the like.

(Sixth step) The electrode group is impregnated with at least a non-aqueous electrolyte.

The non-aqueous electrolytic solution contains a non-aqueous solvent and an electrolyte dissolved in the 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,
Examples thereof include dimethyl ether and tetrahydrofuran (THF). The non-aqueous solvent may be used alone or in combination of two or more.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), 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 preferably 0.2 mol / L to 2 mol / L.

When a chemical gelling agent is used as the gelling agent, it is preferable to impregnate the electrode group with a polymerization initiator such as a crosslinkable monomer or a peroxide together with the non-aqueous electrolytic solution.

(Seventh Step) The gel electrolyte precursor layer in the electrode group is gelled.

When a physical gelling agent is used, gelling is
This can be performed by heating the electrode group and then cooling it. On the other hand, when a chemical gelling agent is used, although the polymerization reaction and the crosslinking reaction proceed even at room temperature, it is preferable to subject the electrode group to a heat treatment from the viewpoint of increasing the gelation rate.

It is desirable that the gelation be performed after the electrode group is sealed in the outer package. The outer package can be formed of, for example, a metal such as iron or aluminum, a sheet in which a metal layer is interposed between a thermoplastic resin layer and a resin layer, or the like.

The sheet material will be described below.

The thermoplastic resin layer serves as a heat-sealing surface of the outer package. 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 multi-layer structure composed of a plurality of thermoplastic resins.

The metal layer plays a role of preventing invasion of moisture. The metal layer can be formed of, for example, aluminum, nickel, or stainless.

The resin layer plays a role of protecting the metal layer. The resin layer can be formed from a polyolefin such as polyethylene terephthalate (PET) or polypropylene. The resin layer is
It can be a single layer or a multi-layer structure composed of a plurality of resins.

According to the method for manufacturing a non-aqueous secondary battery according to the present invention described above, first, a polymer that is hardly soluble in a non-aqueous electrolyte, a gelling agent that causes the non-aqueous electrolyte to gel, and the above-mentioned difficulty. After preparing a paste containing a soluble polymer and a first solvent that is a good solvent for one of the solutes of the gelling agent, the paste is used on at least one of the positive electrode and the negative electrode. To form a gel electrolyte precursor layer. This allows the sparingly soluble polymer and the gelling agent to permeate into the electrode, so that the battery resistance can be lowered. Moreover, since the gel electrolyte layer is easily handled, the thickness of the gel electrolyte layer can be reduced, and the energy density of the non-aqueous secondary battery can be improved.

Next, when the gel electrolyte precursor layer is immersed in a second solvent that is compatible with the first solvent and is a poor solvent for the one solute, part or all of the first solvent is removed. Since the solute is replaced with the second solvent, the solute (one solute) which has been dissolved in the first solvent until now is deposited, and the one solute can be phase-separated from the second solvent. When the second solvent in the gel electrolyte precursor layer is volatilized in such a state, the second solvent is rapidly volatilized, so that a large void can be formed in the gel electrolyte precursor layer,
It is possible to improve the permeability of the gel electrolyte precursor layer in the non-aqueous electrolyte solution.

When an electrode group is prepared by using the electrode on which such a gel electrolyte precursor layer is formed, and at least a non-aqueous electrolyte solution is poured into the electrode group, the non-aqueous electrolyte solution is promptly injected into the electrode group. It is possible to permeate and spread the nonaqueous electrolytic solution over the entire electrode group. Then, by gelling the gel electrolyte precursor layer in the electrode group, the gel electrolyte can be uniformly held in the electrode group, and the interface resistance between the electrode and the gel electrolyte layer can be lowered. as a result,
Since the internal resistance of the secondary battery can be lowered, the initial capacity and rate characteristics of the secondary battery can be improved. Moreover, since the gel electrolyte is uniformly held in the electrode group, the liquid leakage resistance can be improved.

In the method for producing a non-aqueous secondary battery according to the present invention, by using a good solvent for the poorly soluble polymer as the first solvent, the good solvent for the gelling agent is used as the first solvent. Compared with the case, it is possible to improve the impregnation rate of the non-aqueous electrolyte solution into the electrode group, further reduce the internal resistance of the secondary battery, and further improve the initial capacity and rate characteristics.

In the method for producing a non-aqueous secondary battery according to the present invention, by using a physical gelling agent as the gelling agent, the stability of the gel electrolyte can be increased.
The liquid leakage resistance can be made higher.

[0058]

EXAMPLES Examples of the present invention will be described in detail below.

Example 1 (Production of Positive Electrode) 88% by mass of LiCoO ₂ , 7% by mass of acetylene black, 5% by mass of polyvinylidene fluoride as a binder resin (binder), and N-methyl A positive electrode active material paste was prepared by dispersing it in 2-pyrrolidone. The resulting paste has a thickness of 20 μm
On the positive electrode current collector made of aluminum foil by the doctor blade method so that the thickness is 100 μm and the width is 150 mm,
A sheet was formed into a positive electrode.

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

(Preparation of Non-Aqueous Electrolyte) LiBF ₄ was added to a non-aqueous solvent prepared by mixing ethylene carbonate (EC) and γ-butyrolactone (BL) in a volume ratio of 1: 3 at a concentration of 1.5 mol / L. To obtain a non-aqueous electrolytic solution.

(Preparation of Gel Electrolyte Layer Precursor) Polyvinylidene fluoride powder (PVd
F) was dissolved in N-methyl-2-pyrrolidone (NMP), which is a good solvent for PVdF and a poor solvent for PAN, in an amount of 12% by weight, and then used as a gelling agent. Acrylonitrile powder (PAN) (PVd
F / PAN) was dispersed so as to have a volume ratio of 1, and colloidal silica having an average particle diameter of 0.005 μm was dispersed as PVdF in the same volume as a filler (reinforcing material) to obtain a paste. The obtained paste was coated on the positive electrode and the negative electrode by a doctor blade method so as to have a thickness of 10 μm.

Thereafter, the paste-coated positive electrode and negative electrode were immersed in ethanol, which is a second solvent having excellent compatibility with NMP and a poor solvent for PVdF, in a wet state, to replace NMP with ethanol. After that, the gel electrolyte precursor layer was made porous by drying at 80 ° C. for 2 hours.

(Assembly of Cell) A positive electrode and a negative electrode on which a gel electrolyte precursor layer was directly formed were stacked in the order of positive electrode / gel electrolyte precursor layer / negative electrode 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, and the positive electrode terminal and the negative electrode terminal were projected outside the bag. Then 80 ° C,
After vacuum drying for 12 hours, it was introduced under an argon atmosphere,
The nonaqueous electrolytic solution was injected, and the opening of the bag was heat-sealed to seal the electrode group in the outer package. Then, remove from the argon atmosphere, heat at 80 ℃ for 1 hour, then 20 ℃
A thin non-aqueous secondary battery having a structure shown in FIGS. 1 and 2 and having a designed capacity of 100 mAh was manufactured by cooling to a gel and performing gelation.

The secondary battery thus obtained had a design capacity of 0.
At a current of 2 CmA, constant voltage-constant voltage charging with a final voltage of 4.2 V was performed for activation.

That is, the thin non-aqueous secondary battery has the positive electrode 1
And a negative electrode 2 and a gel electrolyte layer 3 disposed between the positive electrode 1 and the negative electrode 2 are integrated into an electrode group. The positive electrode 1 comprises a porous current collector 4 and a positive electrode layer 5 carried on both surfaces of the current collector 4. On the other hand, the negative electrode 2 comprises a porous current collector 6 and a negative electrode layer 7 carried on both surfaces of the current collector 6. The strip-shaped positive electrode terminal 8 is obtained by extending the current collector 4 of each of the positive electrodes 1 in a strip 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 into a strip shape. For example, the positive electrode lead 10 made of a strip-shaped aluminum plate has the two positive electrode terminals 8
Connected with. The negative electrode lead 11 made of, for example, a strip copper plate is connected to the negative electrode terminal 9. The electrode group having such a configuration is hermetically sealed in the exterior body 12 in a state where the positive electrode lead 10 and the negative electrode lead 11 extend from the exterior body 12.

Examples 2 to 4 Example 1 described above except that the type of gelling agent was changed as shown in Table 1 below.
A thin non-aqueous secondary battery was manufactured in the same manner as in. In addition, Table 1
PEO in represents polyethylene oxide,
PPO stands for polypropylene oxide, PVdF
-HFP copolymer is vinylidene fluoride (VdF)
Represents a copolymer of hexafluoropropylene (HFP).

Comparative Example 1 A thin non-aqueous secondary battery was manufactured in the same manner as in Example 1 except that NMP was not replaced with ethanol, that is, the gel electrolyte layer was not made porous.

(Comparative Example 2) A gel electrolyte paste was prepared in the same manner as described in Example 1, and the obtained paste was applied onto a PET film to have a thickness of 4 by a doctor blade method.
It was coated so as to have a thickness of 0 μm. Immerse the coating film in ethanol in a wet state,
After replacing MP with ethanol, the gel electrolyte precursor layer was made porous by drying at 80 ° C. for 2 hours. The obtained gel electrolyte precursor layer was arranged between the positive electrode and the negative electrode to prepare an electrode group.

A thin non-aqueous secondary battery was manufactured in the same manner as in Example 1 except that this electrode group was used.

Comparative Example 3 A gel electrolyte paste was prepared in the same manner as described in Example 1, and the obtained paste was applied onto a PET film to have a thickness of 2 by a doctor blade method.
It was coated so as to have a thickness of 0 μm. Since this coating film could not be handled, a secondary battery could not be manufactured.

Comparative Example 4 (Preparation of Gel Electrolyte Precursor) Polyvinylidene fluoride powder (PVdF) as a poorly soluble polymer was dissolved in N-methyl-2-pyrrolidone (NMP) in an amount of 12% by weight, and then a filler was further added. (Reinforcement material) average particle size 0.00
A 5 μm colloidal silica was dispersed in the same volume as PVdF to obtain a paste. The obtained paste was coated on the positive electrode and the negative electrode by a doctor blade method so as to have a thickness of 10 μm, and then dried at 80 ° C. for 2 hours.

(Preparation of Non-Aqueous Electrolyte with Gelling Agent) Ethylene carbonate (EC) and γ-butyrolactone (B
L) in a non-aqueous solvent in which the volume ratio is 1: 3, and Li
BF ₄ was dissolved to a concentration of 1.5 mol / L to prepare a non-aqueous electrolytic solution. Polyacrylonitrile powder (PAN) was added as a gelling agent to the non-aqueous electrolyte (P
VdF / PAN) was dispersed at a volume ratio of 1.

(Assembly of Cell) A positive electrode and a negative electrode on which a gel electrolyte precursor layer was directly formed were stacked in the order of positive electrode / gel electrolyte precursor layer / negative electrode 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, and the positive electrode terminal and the negative electrode terminal were projected outside the bag. Then 80 ° C,
After vacuum drying for 12 hours, it was introduced under an argon atmosphere,
The non-aqueous electrolyte solution to which the gelling agent had been added was injected, and the opening of the bag was heat-sealed to seal the electrode group in the outer package. After that, it was taken out from under an argon atmosphere, heated at 80 ° C. for 1 hour, then cooled to 20 ° C. to perform gelation,
It has the structure shown in FIGS. 1 and 2 and has a design capacity of 1
A thin non-aqueous secondary battery of 00 mAh was manufactured.

The obtained secondary battery was activated under the same conditions as described in Example 1 above.

(Measurement of Impedance of Cell) For each of the obtained secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 4, 20
AC impedance at 1KHz at 4.2 ℃
The measurement was performed with the battery charged to V, and the results are shown in Table 2 below.

(Measurement of Initial Capacity of Cell) Each of the obtained secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 4 was charged at 20 ° C. with a current of 0.2 CmA for 10 hours. Then, the discharge capacity (initial capacity) when discharged with a current of 1 CmA was measured, and the results are shown in Table 2 below.

(Evaluation of Cell Rate Characteristics) Regarding the secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 4, 0.2 CmA, 0.5 CmA, 1.0 CmA, 2.0 C at 20 ° C.
The discharge capacity when discharged to a final voltage of 3.0 V with a current of mA was measured. The discharge capacity at 0.5C, 1.0C, and 2.0C is represented by setting the discharge capacity at 0.2C as 100%, and the results are also shown in Table 2 below.

(Determination of Liquid Leakage) Examples 1 to 4 and Comparative Examples 1 to 1
Regarding the secondary battery of No. 4, the end of the outer casing was cut off from the charged non-aqueous secondary battery, a pressure of 100 kg / cm ² was applied, and it was investigated whether or not liquid leakage occurred at this time, and the change The absence was designated as A, and the leakage was designated as B, and the results are shown in Table 2 below.

[0080]

[Table 1]

[0081]

[Table 2]

As is apparent from Tables 1 and 2, Examples 1 to 1
It can be seen that the secondary battery of No. 4 has a low battery resistance, a high initial capacity, can suppress the decrease of the discharge capacity when the discharge rate is increased, and is excellent in the retention of the non-aqueous electrolyte.

On the other hand, the secondary battery of Comparative Example 1 obtained by the method in which the first solvent and the second solvent were not replaced had a large battery resistance as compared with Examples 1 to 4, It can be seen that the capacity and rate characteristics are inferior. Also,
The secondary battery of Comparative Example 2 obtained by the method without directly forming the gel electrolyte precursor layer on the positive electrode and the negative electrode was obtained by
It can be seen that the battery resistance is higher than that of No. 4. Furthermore, the thickness of the gel electrolyte precursor layer in Comparative Example 2 was set to 20.
When the thickness was as thin as μm, the battery could not be manufactured. Meanwhile, the gelling agent is added to the non-aqueous electrolyte solution,
It can be seen that the secondary battery of Comparative Example 4 obtained by the method of not performing the solvent substitution treatment of No. 1 has a lower initial capacity and a larger battery resistance than those of Examples 1 to 4.

[0084]

As described above in detail, according to the present invention, there is provided a method for manufacturing a non-aqueous secondary battery having excellent liquid leakage resistance, low internal resistance, high initial capacity, rate characteristics and capacity density. be able to.

[Brief description of drawings]

FIG. 1 is a plan view showing a thin non-aqueous secondary battery of Example 1.

FIG. 2 is a cross-sectional view showing the thin non-aqueous secondary battery of FIG.

[Explanation of symbols]

1 ... Positive electrode, 2 ... Negative electrode, 3 ... gel electrolyte layer, 4 ... Positive electrode current collector, 5 ... Positive electrode layer, 6 ... Negative electrode current collector, 7 ... Negative electrode layer, 12 ... Exterior body.

Claims (2)

[Claims] 1. A sparingly soluble polymer that is sparingly soluble in a non-aqueous electrolytic solution, a gelling agent that gelates the non-aqueous electrolytic solution, and a solute of any one of the sparingly soluble polymer and the gelling agent. And a step of forming a gel electrolyte precursor layer using the paste on at least one electrode of a positive electrode and a negative electrode; The gel electrolyte precursor layer is immersed in a second solvent that is compatible with the solvent and is a poor solvent for the one solute, and at least a part of the first solvent is used as the second solvent. A step of substituting, a step of volatilizing the second solvent in the gel electrolyte precursor layer, a step of forming an electrode group using the electrode on which the gel electrolyte precursor layer is formed, and the electrode group A step of impregnating a non-aqueous electrolytic solution into the And a step of gelling the gel electrolyte precursor layer in the pole group to form a gel electrolyte layer. 2. The method for producing a non-aqueous secondary battery according to claim 1, wherein the one solute is the hardly soluble polymer.