JPH09283177A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the lifetime of a battery by regulating inner pressure of a case. SOLUTION: In this battery, the inner pressure of a case 6 is set at 1.0×10<5> Pa or more. Consequently, even in the case where volume of the active material of a positive electrode 1 or a negative electrode 2 is expanded or shrunk, pressurizing force at the same degree with the inner pressure of the case 6 is always applied to the positive electrode 1 and the negative electrode 2. With this structure, pressurizing force to be applied to the positive electrode 1 and the negative electrode 2 can be sufficiently strengthened in comparison with the conventional battery. Consequently, since the appropriate pressurizing force is always applied to the electrodes, even in the case where the volume of the active material is changed at the time of charging and discharging fall of the active material with charging and discharging can be controlled by appropriately adjusting the inner pressure of the case 6, and a battery having a long lifetime is obtained. An upper limit value of the inner pressure depends on the kind and thickness of the case 6, but a high pressure such as several hundreds air pressure can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a battery and a method for manufacturing the battery.

[0002]

2. Description of the Related Art A lead battery, a nickel-cadmium battery, a nickel-hydrogen battery, a lithium-ion battery in which a positive electrode plate and a negative electrode plate are housed in a case having a non-flexible shape such as a cylindrical or prismatic metal case. In a conventional battery such as the one described above, by pressing the positive electrode plate and the negative electrode plate with a case, the active material is prevented from dropping from the positive electrode plate or the negative electrode plate due to charging or discharging, and the reduction in the life of the battery caused thereby. .

However, in the conventional battery, when the volume of the active material of the positive electrode or the negative electrode expands or contracts due to charging or discharging, the volume change of the active material changes the strength of compression of the positive electrode plate and the negative electrode plate due to the case. .

Therefore, there has been a problem that it is not possible to always maintain an appropriate electrode compression strength. In particular, when an active material that is a metal or an alloy is used, the volume expansion or volume contraction of the active material due to charging or discharging is large, and this problem has been remarkable.

Further, in a conventional battery in which the positive electrode plate and the negative electrode plate are housed in a case having a shape such as an aluminum-polyethylene laminate sheet and having flexibility, and the volume in the case can be changed, By accommodating the electrode and the electrolyte and sealing the case while decompressing the inside, the electrode is applied with a pressure approximately equal to the atmospheric pressure. In this conventional battery, even when the active material expands or contracts in volume by charging or discharging, the pressing force applied to the electrodes does not change so much, but the pressing force in that case is almost the same as the atmospheric pressure. However, there is a problem in that it is not possible to sufficiently suppress the fall of the active material from the positive electrode plate or the negative electrode plate due to charging or discharging, and the decrease in battery life caused thereby.

In recent years, with the development of electronic equipment, the appearance of new high-performance batteries is expected. Currently, the main sources of power for electronic devices are manganese dioxide / zinc batteries for primary batteries, and nickel-based batteries such as nickel / cadmium batteries, nickel / zinc batteries, nickel / hydride batteries and lead batteries for secondary batteries. Is used for. An alkaline aqueous solution such as potassium hydroxide or an aqueous solution such as sulfuric acid is used as the electrolytic solution of these batteries. The theoretical decomposition voltage of water is 1.23V, and if the battery system is more than that value, the decomposition of water will occur easily and it will be difficult to store it stably as electric energy. Therefore, the electromotive force is about 2V at most. The thing is only put to practical use. Therefore,
A non-aqueous electrolyte solution is used as an electrolyte solution for a high-voltage battery of 3 V or more. However, most non-aqueous electrolytes are flammable, and batteries using non-aqueous electrolytes have a problem in safety. Therefore, various attempts have been made to improve the safety of the battery by using a solid electrolyte having a chemical reactivity lower than that of the non-aqueous electrolyte solution instead of the non-aqueous electrolyte solution.

However, in a conventional battery in which a positive electrode, a negative electrode and an electrolyte are housed in a case having a non-flexible shape such as a cylindrical or prismatic metal case, when a solid electrolyte is used, charging or discharging may occur. Since the compressive force applied to the positive electrode plate, the negative electrode plate, and the solid electrolyte changes significantly due to the expansion or contraction of the volume of the active material, peeling of the interface between the electrode and the electrolyte easily occurs, and the peeling between the electrode and the solid electrolyte occurs. There has been a problem that the interfacial charge transfer is hindered and the life of the battery is shortened. Moreover, when the positive electrode and the negative electrode are housed in a case having flexibility in shape, such as an aluminum-polyethylene laminate sheet, and a solid electrolyte is used in a conventional battery in which the volume in the case may change, the electrode and the solid The pressing force applied to the electrolyte is not sufficiently strong because it is about the same as atmospheric pressure, and peeling between the electrode and the solid electrolyte easily occurs, which peeling hinders interfacial charge transfer between the electrode and the electrolyte. There is a problem that the life of the battery is reduced.

Particularly, in a secondary battery, peeling of the interface between the electrode and the solid electrolyte is apt to occur due to repeated volume expansion and contraction of the active material due to charge and discharge, so that reduction in cycle life is a very serious problem. It was.

[0009]

Therefore, the present invention has been made in order to solve the above problems of the battery, and the volume of the active material of at least one of the positive electrode and the negative electrode is changed by charging or discharging. Even in a battery that expands or contracts, a suitable pressure is always applied to the positive electrode and the negative electrode, and a battery in which the active material does not fall off due to charge and discharge is provided, and also in a battery having a solid electrolyte, separation of the electrode and the solid electrolyte is achieved. A battery with a long life, which can suppress

[0010]

The present invention provides a laminate having a positive electrode, a negative electrode, and an electrolyte, a flexible outer casing with which the laminate is covered, and a laminate covered with the outer casing. A battery case that is hermetically housed, wherein the internal pressure of the battery case is 1.0 × 10 ⁵ Pa or more, the electrolyte is a solid electrolyte, and the positive electrode, the electrolyte, and the negative electrode The laminated body is characterized by being sandwiched by means for uniform pressing force, and is characterized by combining these.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In a battery according to the present invention, a laminate of a positive electrode, a negative electrode, and an electrolyte is made of a resin sheet, a laminate sheet of a resin sheet and a metal (for example, an aluminum-polyethylene laminate sheet) or a flexible metal foil. Is a battery case b, which has a sealed structure covered with an exterior body a having a property of being sealed and which is covered with the exterior body.
It is characterized in that it is hermetically housed inside and the internal pressure of the battery case b is set to 1.0 × 10 ⁵ Pa or more. Therefore, even if the volume of the active material of at least one of the positive electrode and the negative electrode expands or contracts due to charging or discharging, the positive electrode and the negative electrode are always subjected to the same compressive force as the internal pressure of the sealed case b. Moreover, by setting the internal pressure of the closed case b to 1.0 × 10 ⁵ Pa or more, the compressive force applied to the positive electrode and the negative electrode can be made sufficiently stronger than that of the conventional battery. Therefore, the battery according to the invention is
By adjusting the pressure in the closed case b to an appropriate level,
Even when the volume of the active material changes due to charging or discharging, the battery always has an appropriate pressing force applied to the electrodes, and the active material can be prevented from falling off due to charging and discharging,
The battery has a long life. Although the upper limit of the internal pressure cannot be determined unconditionally, it is greatly influenced by the type of battery case, the wall thickness of the battery case, etc., and can be set to a high pressure of several hundreds of atmospheres depending on the usage. Of course, it goes without saying that values such as several tens and several atmospheres can be taken.

Further, when a solid electrolyte is used, in a conventional battery, the compression force applied to the electrode and the electrolyte is greatly changed by the expansion or contraction of the volume of the active material due to charging or discharging, or the electrode and the electrolyte are affected. Since the compressive force was not sufficiently strong, peeling of the interface between the electrode and the electrolyte was likely to occur, and the peeling hindered the interfacial charge transfer between the electrode and the electrolyte. However, in the battery according to the present invention, even if the volume of the active material expands or contracts due to charging or discharging, an appropriate pressing force is always applied to the electrode and the electrolyte, so that the separation of the interface between the electrode and the solid electrolyte is less likely to occur. . Therefore, the interfacial charge transfer between the electrode and the electrolyte proceeds smoothly and the life of the battery is extended.

As one aspect of the present invention, since the laminate is sandwiched by means of uniform pressing force such as a stainless plate, even if the volume of the active material expands or contracts due to charge or discharge, the electrode and the electrolyte are pressed uniformly. You can exert your strength.

In the present invention, in particular, a battery using a metal or alloy active material that undergoes a large volume change due to charge and discharge,
Also, in the secondary battery in which the active material undergoes repeated volume expansion and volume contraction due to charge and discharge, the problems of the conventional battery are significantly improved.

That is, as the negative electrode material, in particular, metal lithium, an alloy of Al, Si, Pb, Sn, Zn, Cd or the like with lithium, a transition metal composite oxide such as LiFe ₂ O ₃ or WO _2, or WO _{2 is used.} , Transition metal oxides such as MoO ₂ , carbonaceous materials such as graphite and carbon, Li ₅ (Li ₃
Lithium nitride such as N) or a mixture thereof can be applied.

On the other hand, as the positive electrode material, V ₂ O ₅ is used as a compound capable of inserting and extracting lithium, but the present invention is not limited to this. In addition to this, as the inorganic compound, a composition formula LixMO ₂ or Liy
M ₂ O ₄ (where M is a transition metal, 0 ≦ x ≦ 1, 0 ≦ y
A complex oxide represented by ≦ 2), an oxide having tunnel-shaped vacancies, and a metal chalcogenide having a layered structure can be used. Specific examples thereof include LiCoO ₂ and Li.
NiO ₂ , LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ , MnO
_{2, FeO, V 6 O 13} , TiO 2, TiS 2 and the like. In addition, examples of the organic compound include conductive polymers such as polyaniline. Further, the above-mentioned various active materials may be mixed and used regardless of an inorganic compound or an organic compound.

Further, in sealing the battery case,
For example, in a pressurized atmosphere, sealing may be performed by caulking, caulking, welding or the like, but not limited to this.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to preferred embodiments.

First, the production of the lithium ion conductive polymer film will be described. First, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1 and 1 mol / l of LiPF ₆ was added to prepare an electrolytic solution. A mixture of this electrolytic solution and polyacrylonitrile (PAN) having a molecular weight of about 10,000 at a weight ratio of 7: 1 was applied on a stainless steel plate, and the mixture was heated at 100 ° C. for 30 minutes.
After heating for 1 minute, it was cooled at −20 ° C. for 15 hours to form a gel and a polymer electrolyte having a thickness of 30 μm.

Next, the production of the positive electrode will be described. First, crystalline vanadium pentoxide 70 Wt%, acetylene black 6 wt%, polyvinylidene fluoride 9 wt
%, N-methylpyrrolidone (NMP) 15 wt% mixed, width 18 mm, length 32 mm, thickness 20 μm
Applied on the aluminum foil of and dried at 150 ° C to NM
The P was evaporated. After performing the above operation on both sides of the aluminum foil, pressing was performed to manufacture a positive electrode. The thickness of the positive electrode after pressing was 170 μm.

A copper negative electrode current collector having a thickness of 14 μm has a thickness of 10
A metallic lithium foil of μm was pressure-bonded to obtain a negative electrode plate.

FIG. 1 is a sectional view schematically showing batteries (A) and (B) according to the present invention in Example 1. In the figure, 1 is a positive electrode, 2 is a negative electrode, and 3 is a polymer electrolyte.

Reference numeral 4 denotes a stainless plate which is a means for making the pressing force uniform, and the material is not limited to this, and any material that can make the pressing force uniform is sufficient. Reference numeral 5 is a polyvinyl chloride sheet, 6 is a stainless steel case, and 7 is a heat-sealed portion of the polyvinyl chloride sheet.

Between the positive electrode 1, the polymer electrolyte 3 and the negative electrode 2 prepared as described above, between the positive electrode 1 and the negative electrode 2 so that the positive electrode 1 has three layers, the negative electrode 2 has four layers, and the negative electrode 2 has both ends. The three positive electrode current collectors and four negative electrode current collectors were electrically connected to each other with the polymer electrolyte 3 interposed therebetween. The positive electrode 1, the negative electrode 2 and the polymer electrolyte 3
The laminated body of 2 is sandwiched from both sides by a stainless plate 4 having a width of 20 mm, a length of 34 mm and a thickness of 0.5 mm, and further covered with a polyvinyl chloride sheet 5, and the inside of the sheet 5 is depressurized to surround the periphery of the sheet 5. Sheet 5 by heat fusion
The inside of was sealed.

The battery manufactured in this manner is used at a height of 40
mm, width 22.2 mm, and thickness 5 mm.
By sealing in a high-pressure atmosphere of × 10 ⁵ Pa and 2.0 × 10 ⁵ Pa, the internal pressure of the stainless steel case is 1.5 × 10 ⁵ Pa and 2.0 × 10 ⁵ Pa, respectively, and the capacity is 61 mAh. Batteries (A) and (B) according to the present invention were produced.

The batteries (A) and (B) according to the present invention are
Since the positive electrode, the negative electrode, and the electrolyte are sandwiched by the stainless steel plate 4 which does not have flexibility in shape, even if the volume of the active material expands or contracts due to charging or discharging, a uniform pressing force is applied to the entire electrode and the electrolyte. You can Further, since the positive electrode and the negative electrode are laminated in the sheet 5, the decrease in the capacity density of the battery due to the use of the stainless plate 4 and the sheet 5 can be suppressed, and the positive electrode and the negative electrode in the sheet 5 can be reduced. It is also possible to further improve the capacity density by further stacking the above.

As Comparative Example 1, the internal pressure of the stainless steel case 6 was atmospheric pressure (1.
A conventionally known comparative battery (C) having a capacity of 61 mAh was produced in the same manner as the batteries (A) and (B) according to the present invention, except that the stainless steel case 6 was sealed while keeping 0 × 10 ⁵ Pa).

As Comparative Example 2, instead of covering with the sheet 5, a stainless plate having a width of 20 mm, a length of 34 mm, and a thickness of 1 mm was inserted into the stainless case 6 as a spacer to press the electrodes. Has a capacity of 61 mAh in the same manner as the conventionally known battery (C).
A conventionally known comparative battery (D) was manufactured.

The above-mentioned batteries (A) and (B) according to the present invention and conventionally known batteries (C) and (D).
6mA until the battery voltage drops to 1.8V
Constant current discharge and 30 minutes rest after discharging, 6mA constant current charging until battery voltage reaches 3.8V, 2 hours 3.8V constant voltage charging, 30 minutes rest after charging 1
A cycle charge / discharge test was performed at room temperature.

FIG. 2 shows the effect of the number of cycles on the battery capacity in the charge / discharge test of these batteries. From the figure, it is understood that the batteries (A) and (B) according to the present invention exhibit a cycle life superior to those of the conventionally known batteries (C) and (D). Further, the battery (B) according to the present invention has a better cycle life than the battery (A) according to the present invention, and the higher the internal pressure of the stainless steel case 6, the better the cycle life. It is considered that the cycle life of the battery according to the present invention is further improved by optimizing the internal pressure by making the internal pressure of the stainless steel case 6 higher than 2.0 × 10 ⁵ Pa.

The battery in the above embodiment is a lithium battery, but the present invention is not limited to a lithium battery, and a lead battery, a nickel cadmium battery, a nickel hydride battery, a lithium ion battery, and silver or zinc as an active material. The present invention is applicable to all batteries in which the volume of at least one of the positive electrode and the negative electrode active material expands or contracts by charging or discharging, such as a battery using.

Further, although the polymer electrolyte is used in the above-mentioned embodiments, the present invention is not limited to the polymer electrolyte battery, and a battery using an inorganic solid electrolyte or a liquid electrolyte may be used, The liquid electrolyte may be aqueous or non-aqueous. In other words, it goes without saying that an electrolytic solution may be used as the electrolyte, and in this case, a separator is required. And, as the polymer that is the polymer electrolyte, although polyacrylonitrile is used, it is not limited to this, polyethylene oxide, polyether such as polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride, polyvinylidene chloride. , Polymethylmethacrylate, polymethylacrylate, polyvinyl alcohol, polymethacrylonitrile, polyvinyl acetate, polyvinylpyrrolidone, polyethyleneimine, polybutadiene, polystyrene, polyisoprene, or derivatives thereof may be used alone or in combination. Moreover, you may use the high molecule | numerator which copolymerized the various monomer which comprises the said polymer.

In addition, in the lithium ion conductive polymer film in the above-mentioned embodiment, a mixed solution of EC and DEC is used as the organic electrolyte contained in the polymer, but the organic electrolyte is not limited to this. , Ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyl A polar solvent such as tetrahydrofuran, dioxolane or methyl acetate, or a mixed solvent thereof may be used. When the polymer electrolyte has ion conductivity without these organic electrolytes, the organic electrolyte may not be used. Although the polymer electrolyte used in the above examples is non-porous, a porous polymer electrolyte having an organic electrolyte solution contained in the pores may be used, and by using the porous polymer electrolyte, charging at a high rate is possible. The polymer electrolyte battery can be discharged.

Further, in the above-mentioned embodiment, LiPF ₆ is used as the lithium salt contained in the lithium ion conductive polymer film.
F ₄ , LiAsF ₆ , LiClO ₄ , LiSCN, Li
I, LiCF ₃ SO ₃ , LiCl, LiBr, LiCF
A lithium salt such as ₃ CO ₂ or a mixture thereof may be used.

A polyvinyl chloride sheet was used in the examples as the material for the exterior body covering the electrode composed of the laminated body of the positive electrode, the negative electrode and the electrolyte, but the material is not limited to this, and an aluminum-polyethylene laminate is used. It may be a sheet or the like. The battery case is not limited to the rectangular shape, but may be a cylindrical shape or the like. Also, the material is not limited to metal, and may be resin.

The battery case in the present invention means only the battery case body and the lid for sealing or the battery case body. When only the main body is used, the main body also serves as a lid for sealing.

[0037]

The present invention comprises a laminate having a positive electrode, a negative electrode and an electrolyte, an exterior body covering the laminate, and a battery case in which the laminate covered with the exterior body is hermetically housed. It is characterized in that the internal pressure of the battery case is 1.0 × 10 ⁵ Pa or more, the electrolyte is a solid electrolyte, and the laminate of the positive electrode, the electrolyte and the negative electrode is a means for uniform pressing force. It is characterized by being sandwiched by, and characterized by combining these.

As a result, even if the volume of the active material of at least one of the positive electrode and the negative electrode expands or contracts due to charging or discharging, the positive electrode and the negative electrode are always subjected to the same compressive force as the internal pressure of the battery case. become. Then, the compression force can be made appropriate by adjusting the internal pressure of the battery case.

Therefore, the battery according to the present invention can prevent the active material from falling off due to charge / discharge and peeling between the electrode and the solid electrolyte in the battery having the solid electrolyte, and thus can be a long-life battery. .

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing batteries (A) and (B) according to the present invention in Examples.

FIG. 2 is a diagram showing the relationship between the number of charge / discharge cycles and the discharge capacity of the battery of the present invention and a conventional battery in Examples.

[Explanation of symbols]

 1 Positive Electrode 2 Negative Electrode Plate 3 Polymer Electrolyte 4 Stainless Steel Plate 5 Polyvinyl Chloride Sheet 6 Stainless Steel Case 7 Thermal Bonding Portion of Polyvinyl Chloride Sheet

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[Procedure amendment]

[Submission date] July 31, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG. 1 is a schematic sectional view of a battery according to the present invention in this example.

Claims (3)

[Claims] 1. A laminated body having a positive electrode, a negative electrode, and an electrolyte, a flexible outer casing covering the laminated body, and a battery case in which the laminated body covered with the outer casing is hermetically housed. A battery characterized in that the internal pressure of the battery case is 1.0 × 10 ⁵ Pa or more. 2. The battery according to claim 1, wherein the electrolyte is a solid electrolyte. 3. The battery according to claim 1, wherein the laminated body of the positive electrode, the electrolyte and the negative electrode is sandwiched by means for compressing force uniformly.