JP2000149905A - Solid electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the internal resistance of a battery while keeping its mechanical strength, to extend its charge-discharge cycle life and to improve the productivity in manufacturing it by using, for a separator, a fine porous thin film capable of exerting wettability to a nonaqueous solvent impregnated into a solid electrolyte. SOLUTION: In a rolled electrode body 2, a positive electrode 8 and a negative electrode 9 are laminated through separators 10, gel electrolyte layers 11 are formed between the positive electrode 8 and the separator 10 and between the negative electrode 9 and the separator 10, and they are rolled multiple times in the direction A. The gel electrolyte layers 11 are formed on the positive electrode active material layers on both sides of the positive electrode 8. A fine porous thin film containing polyolefin as a main constituent can be used for the separator 10, for instance, polypropylene, polyethylene or their complex can be used. The film thickness of the separator 10 can be set to around 5-35 μm, but it is preferably set to around 7-20 μm considering the mutual relationship between the mechanical strength of the film and its electrical resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called solid electrolyte battery using a solid or gel electrolyte.

[0002]

2. Description of the Related Art In recent years, there have been remarkable reductions in the size and weight of portable electronic devices, and accordingly, it has been desired that secondary batteries serving as power supplies be further reduced in weight and thickness. I have. Among them, lithium ion secondary batteries are
The average discharge voltage of a single cell is about 3.7 V, and is attracting attention as a secondary battery suitable for such applications.

[0003] By the way, lithium ion secondary batteries include:
A non-aqueous electrolyte is used as an electrolyte, and a metal container is used to prevent the leakage. But,
The use of such a metal container is very disadvantageous in improving the energy density of the battery. Then, in the lithium ion secondary battery, as a method of improving the energy density of the battery, a method of changing the battery container to a polymer film that is lighter than a metal is being studied.

However, in such a secondary battery,
Since a liquid non-aqueous electrolyte is used, liquid leakage is likely to occur when converted to a polymer film, and it has been very difficult to use such a polymer film as an exterior member.

Recently, effective solutions to this problem include solids,
Alternatively, a so-called solid electrolyte battery using a gel electrolyte has been proposed.

Some solid electrolyte batteries use a polymer solid electrolyte consisting of a polymer and an electrolyte salt.
However, since the solid polymer electrolyte has an ionic conductivity of 10 ⁻⁴ S / cm or less at room temperature and has a large temperature dependence, it is necessary to improve the ionic conductivity by at least one digit or more. Has been pointed out.

[0007] Therefore, in a solid electrolyte battery, as a solid electrolyte having improved ionic conductivity, a solid electrolyte battery using a gel electrolyte obtained by impregnating and holding an electrolytic solution in a polymer material has attracted attention. The gel electrolyte is a composite material of a host polymer and an electrolyte forming a network serving as a skeleton of the gel. Since the ionic conduction reaction mainly occurs in the electrolyte solution that is impregnated and held, it exhibits ion conductivity at room temperature as much as the electrolyte solution, and its temperature dependence can be approximated by the Arrhenius equation similar to the electrolyte solution. (Eg, H. Akashi, et al., J. Electrochemical Societ)
y, Vol.145, No.3, P.881 (1998)).

[0008]

In the above-mentioned solid electrolyte battery, when a gel electrolyte in which a polymer is plasticized by an electrolytic solution is used, the mechanical strength of the gel electrolyte is reduced. It tends to be lower than that of the polymer solid electrolyte.

For this reason, in a solid electrolyte battery produced by disposing a gel electrolyte between a positive electrode and a negative electrode, an internal short-circuit due to physical contact between the positive electrode and the negative electrode is likely to occur. As a result, there have been problems such as a decrease in yield at the time of manufacturing the battery and a deterioration in the charge / discharge cycle.

[0010] In the case of a solid electrolyte battery, it has been proposed to use a gel electrolyte reinforced with a microporous thin film such as a polyolefin-based separator to cope with such a lack of mechanical strength. This is to improve the mechanical strength of the entire gel electrolyte by forming a composite of the separator having high mechanical strength and the gel electrolyte.

However, in the solid electrolyte battery reinforced by such a separator, there is a problem that the internal resistance of the battery becomes too large, so that the battery characteristics are significantly deteriorated.

Therefore, the present invention has been proposed in view of such a conventional situation, and has a long charge-discharge cycle life by suppressing the internal resistance of the battery while maintaining the mechanical strength of the solid electrolyte. An object is to provide a solid electrolyte battery having excellent productivity.

[0013]

Means for Solving the Problems In order to achieve this object, the present inventors have conducted intensive studies and as a result, have found that the battery characteristics of a solid electrolyte battery are significantly changed by the wettability of the solid electrolyte to a separator. I found it.

Therefore, in the solid electrolyte battery according to the present invention, which achieves the above-mentioned object, a positive electrode and a negative electrode are joined via a separator, and a solid electrolyte is provided between the positive electrode and the separator and between the negative electrode and the separator. In the solid electrolyte battery provided, a microporous thin film having wettability to a nonaqueous solvent impregnated in the solid electrolyte is used as a separator.

According to the solid electrolyte battery of the present invention configured as described above, it exhibits high wettability with respect to the solid electrolyte, thereby maintaining the mechanical strength of the solid electrolyte.
The internal resistance of the battery can be suppressed.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. A polymer lithium ion secondary battery 1 shown as an embodiment of the present invention has a structure shown in FIG.
As shown in FIG. 2 and FIG. 2, while the positive electrode lead wire 3 and the negative electrode lead wire 4 serving as external connection terminals connected to the spirally wound electrode body 2 are led out, the spirally wound electrode body 2 is Is enclosed by the upper laminated film 6 and the lower laminated film 7.

As shown in FIG. 3, the wound electrode body 2 has a positive electrode 8 and a negative electrode 9 laminated on each other with a separator 10 interposed between the positive electrode 8 and the separator 10 and between the negative electrode 9 and the separator 8. A gel electrolyte layer 11 is formed between them, and a large number is wound in the direction of arrow A in the figure.

As shown in FIG. 4, the positive electrode 8 is formed by forming a positive electrode active material layer 13 on both surfaces of a positive electrode current collector 12. Further, in the positive electrode 8, a gel electrolyte layer 11 is formed on the positive electrode active material layers 13 on both surfaces thereof.

As the positive electrode current collector 12, for example, a metal foil such as an aluminum foil, a nickel foil, and a stainless steel foil can be used. These metal foils are preferably porous metal foils. By making the metal foil a porous metal foil, the adhesive strength between the current collector and the electrode layer can be increased. As such a porous metal foil, in addition to a punching metal and an expanded metal, a metal foil having a large number of openings formed by an etching process can be used.

To form the positive electrode active material layer 13, a metal oxide, a metal sulfide, or a specific polymer material can be used as the positive electrode active material, depending on the type of the intended battery. More preferably, Li _x MO ₂ (M represents one or more transition metals, preferably Co, Ni or Mn, x
Varies depending on the battery charge / discharge state, and 0.05 ≦ x ≦ 1.
Twelve. ) Is preferably used. As a transition metal constituting the lithium composite oxide, Co, Ni, Mn, or the like is preferable. Specific examples of such a lithium composite oxide include:
LiCoO ₂ , LiNiO ₂ , LiNi _y Co _(1-y) O ₂
(However, 0 <y <1), LiMn ₂ O _{4 and the} like. To form the positive electrode active material layer 13, these positive electrode active materials may be used alone or in combination of two or more.

Incidentally, such a lithium composite oxide is as follows:
Lithium compounds and transition metal compounds, for example, lithium transition metal carbonates, nitrates, sulfates, oxides, hydroxides, halogen compounds and the like can be produced as raw materials. For example, a lithium salt raw material and a transition metal raw material are each weighed and mixed sufficiently according to a desired composition, and then heated and fired in an oxygen-containing atmosphere at a temperature range of 600 to 1000 ° C. to produce a lithium composite oxide. can do. In this case, the method of mixing each component is not particularly limited, and the powdery salts may be mixed in a dry state as they are, or the powdery salts may be dissolved in water to form an aqueous solution. May be mixed.

When the positive electrode 8 is prepared from such a positive electrode active material, a powder of the positive electrode active material and, if necessary, a conductive agent such as carbon black or graphite, or a binder resin such as polyvinylidene fluoride are used. By uniformly mixing to prepare a positive electrode mixture, and compression-molding the same, a pellet-shaped positive electrode for a coin-type cell can be produced.
Alternatively, a conductive material and a binder resin are added to the powder of the positive electrode active material, and a solvent such as dimethylformaldehyde or n-methylpyrrolidone is further added to prepare a paste-like positive electrode mixture composition. A positive electrode for a wound cell can be prepared by applying the composition to a body and drying the applied body.

As shown in FIG. 5, the positive electrode 8 has, at one end in the longitudinal direction, a positive electrode current collector exposed portion 12a in which the positive electrode current collector 12 is exposed according to the width of the positive electrode lead wire 3. I have. The positive electrode lead wire 3 is attached to the positive electrode current collector exposed portion 12a so as to be led out from one end in the width direction.

As shown in FIG. 6, the negative electrode 9 has a structure in which a negative electrode active material layer 15 is formed on both surfaces of a negative electrode current collector 14. In the negative electrode 9, the gel electrolyte layer 11 is formed on the negative electrode active material layers 15 on both surfaces thereof.

As the negative electrode current collector 14, for example, copper foil,
A metal foil such as a nickel foil and a stainless steel foil can be used. These metal foils are preferably porous metal foils. By making the metal foil a porous metal foil, the adhesive strength between the current collector and the electrode layer can be increased. As such a porous metal foil, in addition to a punching metal and an expanded metal, a metal foil having a large number of openings formed by an etching process can be used.

To form the negative electrode active material layer 15, a lithium alloy such as lithium metal, lithium aluminum alloy,
There are materials capable of doping and undoping lithium, for example, graphite, non-graphitizable carbon-based materials, easily graphitic carbon materials, and the like. Examples of such carbon materials include pyrolytic carbons, cokes (eg, pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, and organic polymer compound fired bodies (eg, cellulose, phenolic resin). , Calcined furan resin at an appropriate temperature.), Carbonaceous materials such as carbon fiber and activated carbon, and polymer electrodes such as polyacetylene, polyaniline, polypyrrole, and disulfide-based electrodes. To form the negative electrode active material layer 15, these negative electrode active materials may be used alone or in combination of two or more.

When the negative electrode 9 is manufactured from such a negative electrode active material, the negative electrode can be manufactured by punching a plate-shaped lithium metal or lithium alloy into a desired shape. Also, a carbon powder and a binder resin such as polyvinylidene fluoride are uniformly mixed to prepare a negative electrode mixture, and the resultant mixture is compression-molded to produce a pellet-shaped negative electrode for a coin-type cell. Alternatively, a conductive material and a binder resin are added to the powder of the positive electrode active material, and a solvent such as dimethylformaldehyde or n-methylpyrrolidone is further added to prepare a paste-like positive electrode mixture composition. A negative electrode for a wound cell can be manufactured by applying the composition to a body and drying the applied body.

As shown in FIG. 7, the negative electrode 9 has, at one end in the longitudinal direction, a negative electrode current collector exposed portion 14a in which the negative electrode current collector 14 is exposed according to the width of the negative electrode lead wire 4. I have. The negative electrode lead wire 4 is attached to the negative electrode current collector exposed portion 14a so as to be led out from one end in the width direction.

As the separator 10, a microporous thin film containing polyolefin as a main component can be used. For example, polypropylene, polyethylene, or a composite thereof can be used.

The porosity of the separator 10 is not particularly limited.
% Is preferable. The reason for setting the porosity to 30% or more is that when the porosity is lower than 30%, the output characteristics of the battery are transiently reduced. Further, the porosity is set to 60% or less because if the porosity is higher than 60%, the mechanical strength is reduced. Further, in the separator 10, the pore diameter and the film thickness of the pores are not particularly limited, but the pore diameter of the pores is set to 1 μm in order to prevent an internal short circuit and to exhibit a shutdown effect due to the pore closure.
m or less. As the separator 10, a film having a thickness of about 5 to 35 μm can be used. However, in consideration of the correlation between the mechanical strength and the electric resistance of the film, the thickness is preferably about 7 to 20 μm. preferable.

To form the gel electrolyte layer 11, as a non-aqueous solvent, for example, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyl lactone, γ-valerolactone, diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran , 1,
3-dioxane, methyl acetate, methyl propylene acid, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 2,4-difluoroanisole,
2,6-difluoroanisole, 4-bromoveratrol and the like can be used alone or as a mixed solvent of two or more kinds.

Here, as the non-aqueous solvent, when a moisture-proof soft polymer film is used as the exterior member 5, ethylene carbonate, propylene carbonate, γ-butyl lactone, 2,4-difluoroanisole, It is preferable to use a combination of solvents having a boiling point of 150 ° C. or higher, such as 6-difluoroanisole and 4-bromoveratrol.

In this case, by using such a high boiling point solvent for the gel electrolyte, deformation of the battery shape at high temperature can be prevented.

However, the above-mentioned polyolefin separator such as polyethylene has strong lyophobicity to a high boiling point solvent such as ethylene carbonate, propylene carbonate or γ-butyl lactone, and in a solid electrolyte battery using the same, Since the internal resistance becomes too large, the battery characteristics are significantly deteriorated.

In a solid electrolyte battery, it is conceivable to mix a linear ester compound having a relatively low boiling point such as dimethyl carbonate as a solvent having good wettability with a polyolefin separator. It is difficult to use such a solvent in order to prevent the deformation of the battery shape at high temperatures.

Therefore, as the separator 10, a microporous thin film having wettability with respect to the non-aqueous solvent impregnated in the solid electrolyte is used.

The surface of the separator 10 has been subjected to a surface active treatment in order to exhibit good wettability with respect to the nonaqueous solvent impregnated in the solid electrolyte. The method for surface-active treatment of the microporous thin film is not limited to a wide variety of specific methods such as lyophilic treatment with a surfactant, plasma treatment, corona discharge treatment, and the like.

As the lyophilic treatment method, a method of applying a chemical substance having a high lyophilic property onto a microporous thin film, or a liquid substance, which is previously added to an electrolytic solution, can be used.

As the surfactant used, for example, hexanol, heptanol, n-octanol, n-decanol, cyclohexanol, phenylethyl alcohol, benzyl alcohol and the like can be used, and these can be used alone or in combination of two or more. Can be used. Further, as a surfactant, polyimide, polyacetanol, polyalkylene sulfide, polyalkylene oxide, cellulose ester, polyvinyl alcohol,
Polybenzimidazole, polybenzothiazole, silicon glycol, vinyl acetate, acrylic acid, methacrylic acid, polyether-modified siloxane, polyethylene oxide, amide compound, amine compound, phosphoric acid compound, etc. alone or in combination of two or more Can be used. Of course, there is no limitation as long as the above-mentioned rules are satisfied.

The lyophilic treatment method of the microporous thin film by the plasma treatment may be performed by a general-purpose method described in, for example, Chapter 2 of “Plasma Polymerization” (by Nagata, Tokyo Chemical Dojin, 1986). it can. Similarly, the atmospheric corona discharge treatment method can be performed by a general-purpose method.
Of course, there is no particular limitation as long as the above conditions are satisfied.

The wettability of the microporous thin film having the surface serving as the separator 10 subjected to the surface active treatment was evaluated by the following method.

First, as shown in FIG. 8, after preparing a solvent in which ethylene carbonate and propylene carbonate are mixed at a volume ratio of 1: 1 in advance, this mixed solution is fixed on a separator 10 fixed without wrinkles. To form a hemispherical liquid 20. At this time, the contact angle θ was recorded, and after further leaving for 1 minute, if a decrease was observed in the contact angle θ, a microporous thin film suitable for use in the present invention was obtained.

The contact angle θ was measured by the method described in (New Experimental Chemistry Course, Chemical Society of Japan, Maruzen). Since the contact angle θ after one minute differs depending on the porosity and pore diameter of the test sample, it is difficult to show a unique value, but ideally it is preferably closer to 0 °.

[0044] To form the gel electrolyte layer 11 is, as an electrolyte salt, e.g., LiPF _6, LiAsF _6, LiB
F ₄ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ S
Lithium salts such as O ₂ ) ₂ N and LiC ₄ F ₉ SO ₃ can be used alone or in combination of two or more. In addition,
The addition amount of the electrolyte salt is preferably adjusted so that the molar concentration in the nonaqueous electrolyte in the gel electrolyte is 0.8 to 2.0 mol / l so that good ion conductivity is obtained.

To form the gel electrolyte layer 11, polyvinylidene fluoride and a copolymer of polyvinylidene fluoride can be used as the polymer material used for the gel electrolyte. , Hexafluoropropylene and tetrafluoroethylene.

As the polymer material used for the gel electrolyte, for example, polyacrylonitrile and a copolymer of polyacrylonitrile can be used. Examples of the copolymerizable monomer (vinyl-based monomer) include, for example,
Examples thereof include vinyl acetate, methyl methacrylate, butyl methacrylate, methyl acrylate, butyl acrylate, itaconic acid, methyl acrylate hydride, ethyl acrylate, acrylamide, vinyl chloride, vinylidene fluoride, and vinylidene chloride. further,
Acrylonitrile butadiene rubber, acrylonitrile butadiene styrene resin, acrylonitrile chloride polyethylene propylene diene styrene resin, acrylonitrile vinyl chloride resin, acrylonitrile methacrylate resin, acrylonitrile acrylate resin and the like can be used.

As the polymer material used for the gel electrolyte, polyethylene oxide and a copolymer of polyethylene oxide can be used. Examples of the copolymerizable monomer include polypropylene oxide, methyl methacrylate, butyl methacrylate, methyl acrylate, butyl acrylate, and the like.

In addition, as the polymer material used for the gel electrolyte, a polyether-modified siloxane and a copolymer thereof can be used.

As the polymer material used for the gel electrolyte, these can be used alone or in combination of two or more.

In the gel electrolyte layer 11, a gel electrolyte was used as a solid electrolyte.
The solid electrolyte is not limited to a gel solid electrolyte as long as it has an ion conductivity of / cm or more. For example, a polymer solid electrolyte composed of the above-described polymer and an electrolyte salt may be used. As the polymer material used for the polymer solid electrolyte, for example, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane, and the like can be used.

Here, in the gel electrolyte layer 11,
The gel electrolyte is preferably formed using a gel electrolyte made of polyacrylonitrile or a copolymer containing polyacrylonitrile. Thereby, a gel electrolyte having higher mechanical strength can be obtained.

In the gel electrolyte layer 11, when polyvinylidene fluoride is used as the gel electrolyte, the gel electrolyte made of a multi-component polymer obtained by copolymerizing polyhexafluoropropylene, polytetrafluoroethylene or the like is used. It is preferably formed using an electrolyte. More preferably, it is preferably formed using a gel electrolyte made of a copolymer of polyvinylidene fluoride and polyhexafluoropropylene. Thereby, a gel electrolyte having higher mechanical strength can be obtained.

The gel electrolyte layer 11 is made of a copolymer of polyvinylidene fluoride and polyhexafluoropropylene. The copolymer of polyvinylidene fluoride and polyhexafluoropropylene is copolymerized with polyvinylidene fluoride. It is more preferable that the ratio be 0.9 or less in order to increase the mechanical strength.

When the copolymerization ratio of polyvinylidene fluoride is 0.9
The reason for the following is that the effect of improving the solvent holding capacity by copolymerizing polyhexafluoropropylene is insufficient,
This is because a sufficient amount of the solvent cannot be held.

In the gel electrolyte layer 11, in order to obtain a good gel electrolyte, the amount of the polymer material to be added is, for example, about 5 to 50% of the weight of the electrolyte. Is preferred.

The positive electrode lead wire 3 and the negative electrode lead wire 4 can be made of a metal material such as aluminum, copper, nickel, and stainless steel, and are processed into, for example, a thin plate or a mesh. The positive electrode lead wire 3 and the negative electrode lead wire 4 are attached to the positive electrode current collector exposed portion 12a and the negative electrode exposed portion 14a, respectively, using a method such as resistance welding or ultrasonic welding.

As shown in FIG. 9, the exterior member 5 only needs to have a moisture-proof property. For example, a nylon film 16a having a thickness of 25 μm, a polyethylene film 17a having a thickness of 20 μm, and an aluminum foil 18 having a thickness of 15 μm are provided. , 25 μm thick nylon film 16b, and 80 μm thick
m of polyethylene film 17b in this order. As shown in FIGS. 1 and 2, the outer member 5 has a shape in which the upper laminate film 6 has a bulge except for an outer edge portion 6 a serving as a fusion portion in order to accommodate the wound electrode body 2. It has been.

In the exterior member 5, when the wound electrode body 2 is sealed, the upper laminated film 6 and the lower laminated film 7 are connected to the outer edge portion 6 a of the upper laminated film 6 with the polyethylene film 17 b side as the inner surface. The lower laminate film 7 is bonded to the lower laminate film 7 by heat fusion, and is sealed under reduced pressure. At this time, the exterior member 5
The wound electrode body 2 is sealed while the positive electrode lead wire 3 and the negative electrode lead wire 4 are led out from the exterior member 5.

The exterior member 5 is not limited to such a configuration. For example, the exterior member 5 may have a configuration in which the wound electrode body 2 is sealed by a substantially bag-shaped laminated film. In this case, after the spirally wound electrode body 2 is housed inside the exterior member 5, the positive electrode lead wire 3 and the negative electrode lead wire 4 are drawn out from the housing holes and sealed under reduced pressure.

Here, when enclosing the wound electrode body 2 in the exterior member 5, as shown in FIGS. 1, 2 and 10,
Two upper and lower fusion films 19 made of a polyolefin resin are provided on the contact portions between the exterior member 5 and the positive electrode lead wires 3 and the negative electrode lead wires 4.
Is provided so as to sandwich it.

The fusion film 19 may be any film having adhesiveness to the positive electrode lead wire 3 and the negative electrode lead wire 4. For example, as the polyolefin resin, polyethylene, polypropylene, modified polyethylene, modified polypropylene, and these polyolefin resins may be used. Copolymers and the like can be mentioned. In addition, it is preferable that the thickness of the fusion film 19 before thermal fusion is in the range of 20 to 200 μm.
The reason why the thickness before the heat fusion is set to 20 or more is that if the thickness is smaller than this, the handleability becomes poor. Conversely, the reason for setting the thickness before the heat fusion to 200 μm or less is that if the thickness is larger than this, moisture easily permeates and it becomes difficult to maintain the airtightness inside the battery.

Therefore, when enclosing the wound electrode body 2 in the exterior member 5, the fusion film 19 is melted by heat fusion, so that the positive electrode lead wire 3 and the negative electrode lead wire 4 and the exterior member 5 are adhered to each other. Properties can be further improved.

According to the polymer lithium ion secondary battery 1 of the present invention having the above-described structure, by using the separator 10 having wettability with respect to the nonaqueous solvent impregnated in the solid electrolyte, The internal resistance of the battery can be suppressed while maintaining the mechanical strength of the solid electrolyte, and the charge / discharge cycle characteristics can be improved.

Further, the yield during battery production can be improved, and a solid electrolyte battery having excellent productivity can be provided.

The shape of the solid electrolyte battery according to the present invention is not particularly limited, and may be various shapes such as a cylindrical shape, a square shape, a coin shape, and a button shape. From the viewpoint of improving the weight energy density, it is preferable to use a moisture-proof laminated film instead of a metal battery can. Further, the electrode body housed inside the battery is not particularly limited, and in addition to the above-described wound structure, a folded structure folded in a zigzag shape, or a stacked structure in which a large number of positive and negative electrodes are sequentially stacked. It may be.

The solid electrolyte battery according to the present invention is not limited to a secondary battery, but may be a primary battery, but is preferably a lithium ion battery or a lithium metal battery.

[0067]

EXAMPLES Examples in which a polymer lithium ion secondary battery according to the present invention was actually manufactured will be described below. Further, a comparative example manufactured for comparison with these examples will be described.

Example 1 In Example 1, to produce a positive electrode, first, an average particle size of 5
A positive electrode mixture was prepared by mixing 91% by weight of LiCoO ₂ of μm, 6% by weight of carbon black as a conductive agent, and 3% by weight of polyvinylidene fluoride as a binder. Then, this positive electrode mixture is dispersed in n-methylpyrrolidone to form a slurry (paste). Next, the obtained positive electrode mixture slurry was uniformly applied to both sides of a 20 μm-thick aluminum foil serving as a positive electrode current collector, dried, and then compression-molded with a roller press to produce a belt-shaped positive electrode. At this time, the size of the positive electrode was 55 mm long and 400 mm wide.

To produce a negative electrode, first, an average particle diameter of 20
A negative electrode mixture was prepared by mixing 90% by weight of μm graphite and 10% by weight of polyvinylidene fluoride as a binder. And
This negative electrode mixture is dispersed in n-methylpyrrolidone to form a slurry (paste). Next, the obtained negative electrode mixture slurry was uniformly applied to both surfaces of a 15 μm-thick copper foil serving as a negative electrode current collector, dried, and then compression-molded with a roller press to prepare a belt-shaped negative electrode. . At this time, the size of the negative electrode was 55 mm in length and 430 mm in width.

A positive electrode lead wire made of reticulated aluminum was spot-welded to the positive electrode, and a negative electrode lead wire made of reticulated copper was spot-welded to the negative electrode to form external connection terminals.

To form the gel electrolyte layer, first, 10 parts by weight of polyacrylonitrile were mixed with 50 parts by weight of ethylene carbonate, 8 parts by weight of propylene carbonate, and γ.
After dispersing 40 parts by weight of -butyllactone in a mixed solution, the mixture was stirred while being heated to 100 ° C. with a homogenizer. When a colorless and transparent polymer solution was obtained, the heating was once stopped, and 15 parts by weight of LiPF ₆ was added to the mixed solution, followed by heating and stirring again for 5 minutes. This was uniformly applied to both surfaces of the above-described positive electrode and negative electrode using a doctor blade, and then placed in a drying oven prepared at 70 ° C. for 3 minutes, so that the surface of each of the positive electrode and the negative electrode had a thickness of about 25 μm. The resulting gel electrolyte layer was formed.

The negative electrode and the positive electrode produced as described above were used as separators, and were subjected to a surface active treatment to give a 25 μm-thick microporous propylene thin film (trade name: Celgard 350).
1, manufactured by Separation Products Japan Co., Ltd.) and wound many times to produce a wound electrode body. The wound electrode body thus obtained was sealed under reduced pressure in a laminate film while leading the negative electrode lead and the positive electrode lead to the outside, to produce a polymer lithium ion secondary battery.

Example 2 Example 2 was the same as Example 1 except that a polymer material obtained by block copolymerization of polyvinylidene fluoride and hexafluoropropylene in a weight ratio of 93: 7 was used as the gel electrolyte. It was produced.

In order to form this gel electrolyte layer, first, dimethyl carbonate 80 parts by weight, γ-butyl lactone 42 parts by weight, ethylene carbonate 50 parts by weight, propylene carbonate 8 parts by weight, and LiPF ₆ 18 parts by weight were used. After 10 parts by weight of a copolymer of polyvinylidene fluoride and hexafluoropropylene was uniformly dispersed in the mixed solution with a homogenizer, the mixture was heated and stirred at 75 ° C. Then, when the mixture changes to a colorless and transparent state, the stirring is stopped, and the mixture is uniformly applied to both surfaces of the positive electrode and the negative electrode using a doctor blade. After placing for about minutes, a gel electrolyte layer having a thickness of about 25 μm was formed on the surfaces of the positive electrode and the negative electrode.

Example 3 In Example 3, a gel electrolyte in which polyacrylonitrile and a copolymer of polyvinylidene fluoride and hexafluoropropylene were mixed at a weight ratio of 1: 2 was used as the gel electrolyte. Except for the above, it was manufactured in the same manner as in Example 1.

COMPARATIVE EXAMPLE 1 Comparative Example 1 was produced in the same manner as in Example 1 except that no separator was provided between the negative electrode and the positive electrode.

Comparative Example 2 Comparative Example 2 was made in the same manner as in Example 2 except that no separator was provided between the negative electrode and the positive electrode.

Comparative Example 3 Comparative Example 3 was made in the same manner as in Example 3 except that no separator was provided between the negative electrode and the positive electrode.

Comparative Example 4 In Comparative Example 4, a 25 μm-thick propylene microporous thin film (trade name: Celgard 3501, manufactured by Separation Products Japan Co., Ltd.) having no surface active treatment applied between the negative electrode and the positive electrode was used. Except for providing, it was produced in the same manner as in Example 1.

Comparative Example 5 In Comparative Example 5, a 25 μm-thick microporous propylene thin film (trade name: Celgard 3501, manufactured by Separation Products Japan) in which no surface active treatment was applied between the negative electrode and the positive electrode was used. Except for providing, it was produced in the same manner as in Example 2.

Comparative Example 6 In Comparative Example 6, a microporous propylene thin film (trade name: Celgard 3501, manufactured by Separation Products Japan) having a thickness of 25 μm in which no surface active treatment was applied between the negative electrode and the positive electrode was used. Except for providing, it was produced in the same manner as in Example 3.

Characteristic Evaluation Test The polymer lithium ion secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 6 manufactured as described above were charged by a constant current and constant voltage method using a potentiogalvanostat. Discharge was performed to determine the short-circuit occurrence rate.

The measuring method is as follows.

First, charging is started with a current value of 200 mA, and is switched to constant voltage charging when the closed circuit voltage reaches 4.2 V. The charging was completed 8 hours after the start of the test. Subsequently, discharging was performed under a constant current condition of 200 mA, and the discharging was terminated when the closed circuit voltage reached 3.0 V.
The short-circuit occurrence rate was evaluated by calculating the ratio of the number of batteries whose initial charge / discharge efficiency was less than 70% to the number of prototype batteries.

Table 1 shows the evaluation results.

[0086]

[Table 1]

As is clear from Table 1, in each of the batteries of Examples 1 to 3, the occurrence rate of short circuit was 1% or less. On the other hand, in the batteries of Comparative Examples 1 to 3, since the separator was not provided between the positive electrode and the negative electrode, the occurrence rate of short circuit was relatively high regardless of the material composition of the gel electrolyte. I understand. The batteries of Comparative Examples 4 to 6 had almost the same short-circuit occurrence rate as the batteries of Examples 1 to 3.

Next, the batteries that had undergone the above-described initial charge test were charged and discharged by the same constant current and constant voltage method, and the discharge capacity required to determine the capacity ratio and energy density was measured.

The measuring method is as follows.

First, charging is started with a current value of 500 mA, and is switched to constant voltage charging when the closed circuit voltage reaches 4.2 V. The charging was completed 3 hours after the start of the test. Subsequently, discharge is performed under a constant current condition of 3000 mA,
Discharge was terminated when the closed circuit voltage reached 3.0 V, and the discharge capacity at this point was determined. Subsequently, by repeating this operation, the discharge capacity of each time was obtained. The capacity ratio was evaluated by obtaining the ratio of the discharge capacity in each cycle to the discharge capacity in the second cycle. This capacity ratio is 10
The closer to 0%, the better the charge / discharge cycle characteristics of the battery.

FIG. 11 shows the evaluation results.

As is apparent from FIG. 11, the batteries of Examples 1 to 3 all exhibited excellent charge / discharge cycle characteristics because the capacity ratio at the 200th cycle was 80% or more. I understand.

On the other hand, in the batteries of Comparative Examples 1 to 3, it can be seen that the capacity ratio at the 200th cycle is 70% or less. This is presumably because an internal short circuit occurred between the positive electrode and the negative electrode during the charge / discharge reaction.

Further, in the batteries of Comparative Examples 4 to 6,
It can be seen that the deterioration of the charge / discharge cycle characteristics has progressed from the initial stage of the cycle. This is because the wettability of the gel electrolyte to the used microporous thin film is extremely low,
It is presumed that the internal resistance of the battery increased.

As described above, using a microporous thin film which has been subjected to a surface active treatment in advance so as to exhibit wettability with respect to a non-aqueous solvent contained in a solid electrolyte, as a separator, requires a battery for the solid electrolyte. It is clear that this is effective in suppressing the internal resistance of the.

[0096]

As described in detail above, according to the solid electrolyte battery of the present invention, a microporous thin film having wettability to a nonaqueous solvent impregnated in the solid electrolyte is used as a separator. Therefore, the internal resistance of the battery can be suppressed while maintaining the mechanical strength of the solid electrolyte, and a solid electrolyte battery having a long charge / discharge cycle life and excellent productivity can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view for explaining a configuration of a polymer lithium ion secondary battery according to the present invention.

FIG. 2 is a perspective view for explaining a configuration of the polymer lithium ion secondary battery.

FIG. 3 is a diagram schematically illustrating a wound electrode body constituting the polymer lithium ion secondary battery.

FIG. 4 is a fragmentary cross-sectional view for explaining the configuration of a positive electrode of the polymer lithium ion secondary battery.

FIG. 5 is a plan view illustrating a configuration of a positive electrode of the polymer lithium ion secondary battery.

FIG. 6 is a fragmentary cross-sectional view for explaining the configuration of the negative electrode of the polymer lithium ion secondary battery.

FIG. 7 is a plan view for explaining a configuration of a negative electrode of the polymer lithium ion secondary battery.

FIG. 8 is a diagram for schematically explaining a method of measuring a contact angle.

FIG. 9 is a cross-sectional view of a main part for describing a configuration of a laminate film of the polymer lithium ion secondary battery according to the present invention.

FIG. 10 is a diagram of the polymer lithium ion secondary battery.
It is the principal part side view seen from arrow B inside.

FIG. 11 is a characteristic diagram showing a relationship between the number of cycles and a capacity ratio.

[Explanation of symbols]

Reference Signs List 1 polymer lithium ion secondary battery, 2 wound electrode body, 3 positive electrode lead wire, 4 negative electrode lead wire, 5 exterior member, 6 upper laminated film, 7 lower laminated film, 8 positive electrode, 9 negative electrode, 10 separator, 1
Reference Signs List 1 gel electrolyte layer, 12 positive electrode current collector, 13 positive electrode active material layer, 14 negative electrode current collector, 15 negative electrode active material layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Goro Shibamoto 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference) 5H021 AA06 BB12 CC00 EE04 EE27 HH01 HH03 5H024 AA00 AA02 AA09 AA12 BB08 DD09 EE09 FF21 GG01 HH01 HH13 5H029 AJ05 AJ06 AJ11 AK03 AK18 AL06 AL07 AL12 AL16 AL18 AM00 AM02 AM03 AM04 AM05 AM07 AM16 BJ04 BJ13 CJ08 DJ04 DJ13 EJ12 EJ14 HJ02 HJ04

Claims (9)

[Claims] 1. A solid electrolyte battery in which a positive electrode and a negative electrode are joined via a separator, and a solid electrolyte is provided between the positive electrode and the separator, and between the negative electrode and the separator. A solid electrolyte battery using a microporous thin film having wettability to a nonaqueous solvent impregnated in the solid electrolyte. 2. The solid electrolyte battery according to claim 1, wherein the separator comprises a microporous thin film containing polyolefin as a main component. 3. The solid electrolyte battery according to claim 2, wherein the separator is made of a microporous thin film containing polyethylene or polypropylene as a main component. 4. The separator has a thickness of 5 μm or more.
4. The solid electrolyte battery according to claim 3, wherein the thickness is 35 [mu] m. 5. The solid electrolyte battery according to claim 1, wherein the solid electrolyte is a gel electrolyte. 6. The solid electrolyte battery according to claim 5, wherein the solid electrolyte is made of polyacrylonitrile or a copolymer containing polyacrylonitrile. 7. The solid electrolyte battery according to claim 5, wherein the solid electrolyte is made of polyvinylidene fluoride or a copolymer containing polyvinylidene fluoride. 8. The solid electrolyte comprises a copolymer of polyvinylidene fluoride and polyhexafluoropropylene, wherein the copolymerization ratio of polyvinylidene fluoride in the copolymer is 0.9 or less. The solid electrolyte battery according to claim 7. 9. The solid electrolyte according to claim 5, wherein the solid electrolyte is a mixture of polyacrylonitrile or a copolymer containing polyacrylonitrile, and polyvinylidene fluoride or a copolymer containing polyvinylidene fluoride. Solid electrolyte battery.