JP3183270B2 - Manufacturing method of organic electrolyte battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electrolyte battery in which an organic electrolyte is injected into a battery to electrochemically activate the battery. Is what you do.

[0002]

2. Description of the Related Art Along with the tendency of a portable telephone and a notebook personal computer to become smaller, lighter and thinner year by year, a demand for a smaller, lighter and thinner battery used as a power source thereof is increasing. Under these circumstances, the production volume of lithium batteries, especially rechargeable lithium secondary batteries, has been increasing year by year from the viewpoint of high voltage and high energy density, and research and development aimed at improving performance have been actively conducted. I have.

As a method of reducing the thickness of a lithium secondary battery,
The power generation element of the battery is the same as that of a conventional cylindrical lithium-ion battery, and it has been studied to make the battery case square and thin using an aluminum alloy or the like, and some of them have been put to practical use. However, with the current technology, there is a limit to the reduction in thickness as long as a power generation element similar to a conventional cylindrical lithium ion battery is used.

As one of the methods for pursuing a reduction in thickness, a lithium polymer secondary battery using a polymer material that absorbs and retains an electrolytic solution has attracted attention. Particularly, as a polymer material invented and proposed by Bellcore of the United States, a copolymer of vinylidene fluoride (hereinafter, referred to as VDF) and propylene hexafluoride (hereinafter, referred to as HFP) (hereinafter, referred to as P (VDF-H)
(FP)) is expected as a battery system closest to practical use. In this battery system, the same P (V
DF-HFP), and the separator and the positive electrode and the negative electrode are integrated by heat fusion.

[0005] Another major feature of this battery system is that a large amount of a plasticizer is added to the polymer material. After integrating the positive electrode, separator, and negative electrode, the plasticizer in the polymer material is extracted and removed with an appropriate solvent to form fine pores in the polymer layer, and these pores are impregnated with an organic electrolyte to form a battery. Has been activated.

In the above-mentioned battery system, since the organic electrolyte is injected after the electrode portions are laminated and integrated, a conventional lithium-based battery in which the organic electrolyte is absorbed in the polymer portion from the beginning.
It is easier to manufacture than a polymer secondary battery. However, simply by injecting the organic electrolyte solution, the organic electrolyte solution has a higher viscosity than the aqueous electrolyte solution, so that it is difficult for the organic electrolyte solution to penetrate into the fine pores of the separator and the electrode. In addition, most of the permeated organic electrolyte is retained in fine pores formed after the plasticizer is removed, and a small amount of the organic electrolyte is absorbed by the polymer itself. For this reason, the organic electrolyte or lithium ion is supplied only in a limited portion where the fine pores and the active material surface are in contact with each other.
There is a problem that good characteristics cannot be obtained with battery characteristics that have a large effect on the amount of supply movement of lithium ions.

[0007]

SUMMARY OF THE INVENTION PVDF or P (V
In a battery system using a polymer that absorbs and retains an organic electrolyte such as a polymer mainly composed of (DF-HFP) as a separator and a binder, a method of supplying the electrolyte to the entire surface of the active material is required. .

An object of the present invention is to provide an organic electrolyte battery having good battery characteristics by impregnating and absorbing the electrolyte solution not only in the fine pores of the separator and the electrode but also in the polymer itself.

[0009]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides an active material mixture layer containing a polymer that absorbs and retains an organic electrolyte, and a pair of electrodes composed of a current collector that supports the active material mixture layer. A porous separator made of a polymer that absorbs and retains the organic electrolyte is interposed between the electrodes, and the laminated electrode is inserted into the battery container, and then the organic electrolyte is injected and electrochemically activated. A method for producing an organic electrolyte battery, comprising the steps of: heating a battery container after injecting the organic electrolyte solution; and heating the electrolyte solution after the injection to absorb the organic electrolyte solution into the polymer material. It is what promoted.

Furthermore, an organic electrolyte is injected into the separator and the fine pores of the electrode under reduced pressure, and by applying heat, the organic electrolyte can be more effectively absorbed into the polymer material. .

According to these methods, the organic electrolyte can be retained not only in the micropores of the separator and the electrode but also in the polymer itself, so that the electrolyte is supplied to the entire surface of the active material. Good battery characteristics are obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method of absorbing and holding an organic electrolyte between a pair of electrodes comprising an active material mixture layer containing a polymer for absorbing and holding an organic electrolyte and a current collector supporting the active material mixture layer. A porous separator made of a polymer to be arranged is disposed, and a laminated electrode of a laminated and integrated configuration is inserted into a battery container, and then an organic electrolyte solution is injected to electrochemically activate the organic electrolyte battery. By heating the battery container after injecting the organic electrolytic solution, the viscosity of the organic electrolytic solution is reduced, and the organic electrolytic solution is easily penetrated into the separator and the micropores of the electrodes. The electrolyte itself can be absorbed and held by the polymer itself having a property of hardly absorbing the electrolyte.

The present invention also relates to a polymer for absorbing and holding an organic electrolyte between a pair of electrodes comprising an active material mixture layer containing a polymer for absorbing and holding an organic electrolyte and a current collector supporting the active material mixture layer. A method for producing an organic electrolyte battery, comprising: inserting a laminated electrode having a configuration in which a porous separator composed of layers is arranged and integrated into a battery container; and injecting an organic electrolyte solution to electrochemically activate the battery. By passing through the step of reducing the pressure inside the battery container after injecting the organic electrolyte solution and the step of heating the battery container, it is difficult to impregnate the organic electrolyte solution under atmospheric pressure conditions. The pores can be impregnated with the organic electrolyte, and the polymer itself can be made to absorb the organic electrolyte, so that the impregnation and absorption of the organic electrolyte into the laminated electrode can be improved.

The heating temperature after the injection is preferably 40 to 80 ° C., so that the laminated electrode can be sufficiently impregnated and absorbed with the organic electrolyte without changing the composition of the organic electrolyte containing the volatile organic solvent. it can. Heating time after injection is 20 ~
It is preferably 60 min, and if it is 20 min or less, the impregnation of the organic electrolyte is insufficient, and the impregnation amount of the organic electrolyte is constant without increasing up to 60 min.

After the injection, the reduced pressure atmosphere is -20 to -20 atmosphere pressure.
It is preferable to reduce the pressure at -70 cmHg, so that the laminated electrode can be sufficiently impregnated and absorbed with the electrolytic solution without changing the composition of the organic electrolytic solution containing the volatile organic solvent.

The effect is great when a polymer material containing at least one selected from the group consisting of polyvinylidene fluoride or a copolymer of vinylidene fluoride and propylene hexafluoride is used as the polymer material. This is because even if polyvinylidene fluoride or a copolymer of vinylidene fluoride and propylene hexafluoride having a low property of absorbing an organic electrolytic solution is used, the method of heating according to the present invention, or the method of heating under reduced pressure and heating is sufficient. Liquid can be impregnated and absorbed. According to the method of the present invention, the viscosity of the organic electrolyte is reduced by heating, the organic electrolyte is easily penetrated into the micropores of the separator and the electrode, and the polymer itself having a property of hardly absorbing the organic electrolyte is used. Thus, the organic electrolyte can be sufficiently absorbed and retained.

The effect is large when a mixed solvent containing a chain carbonate as a main component and a cyclic carbonate as a main component is used as a solvent for the organic electrolytic solution. This lowers the viscosity of the organic electrolyte by heating, so that it can sufficiently impregnate and absorb even organic solvents with a low solubility coefficient, such as chain carbonates with low affinity for polyvinylidene fluoride. As a result, good performance can be obtained in battery characteristics such as discharge characteristics. Examples of the chain carbonate include ethyl methyl carbonate, diethyl carbonate, and diethyl carbonate.

Hereinafter, the present invention will be described in detail with reference to the drawings.

(Embodiment 1) The structure of a laminated electrode portion of a battery used in the present invention will be described with reference to FIG.

The positive electrode plate 1 has a structure in which a positive electrode active material layer 1a containing a polymer that absorbs and retains an organic electrolyte and a positive electrode current collector 1b are laminated. Similarly, the negative electrode plate 2 has a structure in which a negative electrode active material layer 2a containing a polymer that absorbs and retains an organic electrolyte and a negative electrode current collector 2b are laminated. The porous separator 3 made of a polymer that absorbs and retains the organic electrolyte is a positive electrode plate 1
And a negative electrode plate 2, and are laminated and integrated with a positive electrode and a negative electrode by a heat fusion method or a casting method.

The positive electrode current collector 1b is made of punched metal or lath metal such as aluminum or a conductive material coated with aluminum, and has acetylene black, ketjen black or carbon fiber as a conductive carbon material on its surface. A mixture of polyvinylidene fluoride as a binder is bound.

The negative electrode current collector 2b is made of a punching metal or a lath metal such as copper, nickel, or a conductive material coated with copper or nickel, and has a conductive carbon material such as acetylene black, ketjen black, or the like. A mixture of carbon fibers and polyvinylidene fluoride as a binder is bound.

As a method of binding the conductive carbon material to the current collector, for example, a material obtained by dispersing acetylene black in an N-methylpyrrolidone solution of polyvinylidene fluoride is applied directly to the current collector, Of N-methylpyrrolidone is removed by drying.

The positive electrode active material layer 1a and the negative electrode active material layer 2a
Is prepared by applying a paste composed of an active material, a conductive material and a polymer solution on a glass plate, and then removing the solvent by drying. Further, the positive electrode active material layer 1a and the positive electrode current collector 1
b, the negative electrode active material layer 2a and the negative electrode current collector 2b are each thermally fused by a heat roller to produce a positive electrode plate 1 and a negative electrode plate 2, and then a separator 3 is sandwiched between the positive electrode plate 1 and the negative electrode plate 2. Is heat-fused with a heat roller to produce a laminated electrode 4 which is laminated and integrated.

After loading the laminated electrode 4 into a battery container made of a laminated sheet, lithium carbonate hexafluoride was added to the battery container at a rate of 1 mol / l with ethylene carbonate and ethyl methyl carbonate in a volume of 1: 3 from the opening of the battery container. The organic electrolyte dissolved in the mixture mixed in the ratio is injected. After the injection, the inside of the battery container was depressurized and heated to sufficiently impregnate the organic electrode into the laminated electrode, and then returned to the atmospheric pressure, and the opening of the electric container was sealed with a heat seal. I got As a laminate sheet, a metal film having a ventilation barrier property is arranged between insulating resin films, and the whole is laminated and integrated. The laminate electrode is surrounded by the pair of laminate sheets, and laminated by sealing the periphery. The electrode is housed in a battery container.

The method for forming each mixture layer on the positive and negative electrode current collectors is to prepare a mixture sheet in advance and bond the current collector and the mixture sheet by heat fusion. There is a method in which the mixture paste is directly applied to the current collector.

As the positive electrode active material, a lithium-containing composite metal oxide such as lithium cobaltate, lithium nickelate or lithium manganate, which can reversibly insert and remove lithium ions by charge and discharge, can be used.

As the negative electrode active material, a carbon material capable of reversibly taking in and out lithium ions by charging and discharging, and among them, granular graphite particles obtained by carbonizing and graphitizing carbonaceous mesofuses are preferable. It is possible to use a material such as a material or a metal nitride which can reversibly insert and remove lithium ions by charge and discharge.

As the electrolyte, a mixture of ethylene carbonate and a chain carbonate, a mixture of ethylene carbonate and propylene carbonate, or the like can be used as a solvent, and LiPF ₆ , LiCF ₃ SO ₃ , LiC
10 ₄ , LiBF ₄ , LiAsF ₆ or LiN (CF ₃
SO ₂ ) can be used.

[0030]

Example 1 28 g of a copolymer of vinylidene fluoride and propylene hexafluoride (P (VDF-HFP), propylene hexafluoride ratio 12% by weight) was mixed with 144 g of acetone.
Dissolved in water and the pore-forming agent di-n-butyl phthalate (DBP)
A mixed solution to which 28 g has been added is prepared. This solution was applied on a glass plate with a coating thickness of 0.5 mm, and acetone was dried and removed to obtain a thickness of 0.08 mm and a size of 40 mm × 70 mm.
mm polymer electrolyte sheet is prepared.

The positive electrode mixture sheet is P (VDF-HFP) 7
1 g dissolved in 1130 g acetone, 1000 g lithium cobaltate, 53 g acetylene black, DB
A paste prepared by mixing 110 g of P was coated on a glass plate at a coating thickness of 0.9 mm, and then acetone was dried and removed to obtain a thickness of 0.3 mm and a size of 30 mm × 60 mm.
Get a sheet.

The negative electrode mixture sheet is P (VDF-HFP) 3
A solution prepared by dissolving 5 g in 321 g of acetone, 245 g of spherical graphite particles (manufactured by Osaka Gas) obtained by carbonizing and graphitizing carbonaceous mesophase spheres, and graphitized vapor-grown carbon fibers (hereinafter referred to as VGCF) (Osaka Gas) 20g, D
A paste prepared by mixing 54 g of BP was applied on a glass plate with a coating thickness of 1.2 mm, and then acetone was dried and removed to obtain a 0.35 mm thick, 30 mm × 60 m size.
m sheets are obtained.

The mixture of the conductive carbon material and the binder to be applied to the current collector is prepared by dispersing and mixing 30 g of acetylene black and an N-methylpyrrolidone solution of polyvinylidene fluoride (12% by weight). This mixture is added to a thickness of 0.0
After coating on a 6 mm aluminum and copper lath plate, 80
A current collector is prepared by drying and removing N-methylpyrrolidone at a temperature of at least ℃.

The laminate of the positive electrode mixture sheet and the aluminum current collector is sandwiched between polytetrafluoroethylene sheets (PTFE, thickness 0.05 mm),
Heat fusion is performed by applying heat and pressure through two rollers heated to ° C. PTFE is used to prevent the mixture layer from adhering to the roller, and other materials such as copper foil and aluminum foil may be used.

In the same manner, a negative electrode plate is manufactured using the negative electrode mixture sheet and the copper current collector. Finally, the separator was sandwiched between a positive electrode plate and a negative electrode plate and heated to 120 ° C.
Heat and pressure are applied by this roller to produce a laminated electrode that is heat-sealed and integrated. The integrated laminated electrode is immersed in diethyl ether, DBP is extracted and removed, the polymer portion is provided with porosity, and dried at 50 ° C. under vacuum.

The thus prepared laminated electrode was covered with a laminated film having an aluminum film interposed between insulating resin films and housed as a battery container.

Finally, the integrated battery was combined with an organic electrolyte obtained by dissolving lithium hexafluorophosphate at a ratio of 1.5 mol / l in a mixture of ethylene carbonate and ethyl methyl carbonate at a volume ratio of 1: 3. After immersion, heating is performed at a temperature of 30 ° C., 45 ° C., 80 ° C., 100 ° C., and 20 ° C. (no heating) in a thermostat, and a change in the weight of the laminated electrode in the battery with time at each heating temperature is measured. Then, the absorption amount of the organic electrolyte was determined.

The weight of the laminated electrode before dipping in the organic electrolyte was 2.3 g, and the weight of the laminated electrode after dipping in the organic electrolyte was 2.5 g. That is, even when heating is not performed, there is a liquid absorption of about 10% with respect to the weight of the laminated electrode. FIG. 2 shows the relationship between the heating time and the amount of absorbed organic electrolyte when each layer was heated at each temperature, with the weight of the laminated electrode simply immersed in the organic electrolyte being 100. As is apparent from FIG. 2, the weight of the laminated electrode increases, that is, the liquid absorption increases as the heating temperature increases. In addition, when the heating time is 20 minutes or more, there is almost no increase in weight, and it can be seen that the absorption of the organic electrolyte into the laminated electrode reaches an equilibrium state.

FIG. 3 shows discharge rate characteristics when each of the above-mentioned batteries was discharged to a final voltage of 3.0 V at each discharge rate.
As shown in the figure, the heating temperature of the battery container after injecting the organic electrolyte is 40 ° C
Batteries produced at temperatures between -80 ° C show good discharge rate characteristics, but the characteristics sharply deteriorate when the heating temperature is 30 ° C or lower and when the heating temperature is 100 ° C or higher. When the battery container is heated at a temperature of 30 ° C. or less, the organic electrolyte is not sufficiently impregnated into the polymer, so that the battery characteristics are poor. It is considered that the discharge rate characteristics of the battery deteriorated because the composition of the electrolyte significantly changed due to the dissipation of the organic electrolyte.

(Example 2) A battery fabricated in the same manner as in Example 1 was placed in a vacuum vessel before heating while being immersed in the electrolytic solution, and the pressure was reduced to -50 cmHg.

FIG. 4 shows the relationship between the pressure reduction time and the change in weight of the laminated electrode, that is, the amount of liquid absorption. The dry weight is 100. As apparent from FIG. 4, when the pressure is reduced for 5 minutes or more, the weight of the laminated electrode becomes substantially constant.

FIG. 5 shows that the decompression time is 10 minutes, the pressure in the decompression container and the rate of change of the weight of the laminated electrode (the weight in the dry state is 1%).
00). As the pressure in the container decreases, the weight of the laminated electrode increases, and it can be seen that the electrolyte solution impregnates even the fine pores in the laminated electrode due to the reduced pressure.

FIG. 6 shows pressures of -10 cmHg and -20 cmHg.
g, -30cmHg, -50cmHg, -60cmH
g, at −70 cmHg and atmospheric pressure (0 cmHg) for 10 minutes, and then returned to atmospheric pressure and heated at 45 ° C. for 20 minutes to discharge the battery to a final voltage of 3.0 V at each discharge rate. It is a summary of the discharge rate characteristics of the battery at the time of performing.

Since the discharge capacity of the battery subjected to reduced pressure and heating is greatly different from that of the battery subjected to heating only, a fine hole in the laminated electrode into which the organic electrolyte cannot enter under the atmospheric pressure is formed.
It can be seen that the organic electrolyte was impregnated by the reduced pressure. If the degree of pressure reduction is −10 cmHg, the impregnation with the organic electrolyte is insufficient, so that the area where the organic electrolyte and the electrode active material come into contact is small, and good discharge characteristics cannot be obtained. The degree of decompression is -7.
If it is as large as 0 cmHg, the absorption can be performed in a short time, but if the time is not strictly adjusted, the volatile component in the electrolyte dissipates and the viscosity becomes high, so that the composition of the electrolyte changes and the discharge rate characteristics are reduced. Sometimes it gets worse. From this, it is understood that the degree of pressure reduction is preferably in the range of −20 cmHg to −70 cmHg.

[0045]

As described above, by heating after injecting the liquid, or by heating after injecting the liquid and reducing the pressure, the organic material can be easily applied to the separator and the fine pores of the electrode and the polymer material itself which are difficult to absorb the organic electrolytic solution. The electrolyte solution can be permeated, and excellent discharge rate characteristics can be realized. This method is particularly effective for high-rate discharge.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the configuration of a laminated electrode according to the present invention.

FIG. 2 is a diagram showing a weight change rate of a laminated electrode with respect to a change in a heating time for each heating temperature

FIG. 3 is a diagram showing discharge rate characteristics according to heating temperature.

FIG. 4 is a diagram showing a weight change rate of the laminated electrode with respect to a change in decompression time.

FIG. 5 is a diagram showing a weight change rate of the laminated electrode with respect to a change in the degree of pressure reduction.

FIG. 6 is a graph showing discharge rate characteristics at different heating temperatures after pressure reduction.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 positive electrode plate 1a positive electrode mixture layer 1b positive electrode current collector 2 negative electrode plate 2a negative electrode mixture layer 2b negative electrode current collector 3 separator 4 laminated electrode

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazunari Kinoshita 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Nobuo Eda 1006 Kadoma Kadoma Kadoma, Osaka Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-9-22731 (JP, A) JP-A-5-47418 (JP, A) JP-A-10-284121 (JP, A) (58) Fields studied (Int. . ^7, DB name) H01M 10/40 H01M 4/02 - 4/04

Claims (8)

(57) [Claims] 1. A laminated electrode having a structure in which a separator containing a polymer that absorbs and retains an organic electrolyte is disposed between a positive electrode and a negative electrode, and a stacked electrode is inserted into a battery container. A method for producing an organic electrolyte battery which is chemically activated, comprising a step of injecting the organic electrolytic solution and then heating a battery container. 2. A laminated electrode having a structure in which a separator containing a polymer that absorbs and retains an organic electrolyte is disposed between a positive electrode and a negative electrode, and a laminated electrode is inserted into a battery container. A method for producing a chemically activated organic electrolyte battery, comprising: a step of reducing the pressure inside a battery container after injecting the organic electrolytic solution; and a step of heating the battery container. Law. 3. A porous material comprising a polymer capable of absorbing and holding an organic electrolyte, between a pair of electrodes comprising an active material mixture layer containing a polymer capable of absorbing and holding an organic electrolyte and a current collector supporting the active material mixture layer. A method for producing an organic electrolyte battery in which a laminated electrode having a configuration in which a separator is arranged and laminated and integrated is inserted into a battery container, and an organic electrolyte is injected to electrochemically activate the organic electrolyte battery. A method for producing an organic electrolyte battery, comprising a step of heating a battery container after injecting a liquid. 4. A porous material comprising a polymer capable of absorbing and holding an organic electrolyte between a pair of electrodes comprising an active material mixture layer containing a polymer capable of absorbing and holding an organic electrolyte and a current collector supporting the active material mixture layer. A method for producing an organic electrolyte battery in which a laminated electrode having a configuration in which a separator is arranged and laminated and integrated is inserted into a battery container, and an organic electrolyte is injected to electrochemically activate the organic electrolyte battery. A method for manufacturing an organic electrolyte battery, comprising: a step of reducing the pressure inside a battery container after injecting a liquid; and a step of heating the battery container. 5. The method for producing an organic electrolyte battery according to claim 1, wherein a heating temperature after the injection is 40 to 80 ° C. 6. The method for producing an organic electrolyte battery according to claim 2, wherein the reduced pressure atmosphere after the liquid injection is reduced at −20 to −70 cmHg with respect to the atmospheric pressure. 7. The polymer material according to claim 3, wherein the main component is at least one selected from the group consisting of polyvinylidene fluoride or a copolymer of vinylidene fluoride and propylene hexafluoride.
7. The method for producing an organic electrolyte battery according to any one of items 1 to 6. 8. The method for producing an organic electrolyte battery according to claim 1, wherein the solvent of the electrolytic solution is a mixed solvent containing a chain carbonate as a main component and a cyclic carbonate therein.