JP4284261B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery using lithium ions as a medium.

  Lithium ion batteries having high energy density are used for portable electronic devices such as mobile phones and notebook computers. There are various forms of this lithium ion battery, but the forms currently commercialized are coin-type batteries using iron-based cans, cylindrical batteries using iron-based cans, iron-based cans and aluminum cans. There are square batteries using the body and laminated thin batteries using the aluminum laminate film.

  Coin-type batteries are mainly used for memory backup of portable devices and for driving internal clocks. Inserting laminated electrodes into an iron can, closing the opening with an iron lid, and opening the iron can Manufactured by caulking.

  Cylindrical batteries are mainly used for notebook computers and the like, and are manufactured by inserting battery elements into iron-based can bodies, closing the openings with iron-based lids, and caulking the openings in the iron-based can bodies. . For example, Patent Document 1 describes a cylindrical lithium secondary battery in which an insulating sealing plate is caulked and fixed to an opening of a bottomed cylindrical container made of stainless steel.

  The prismatic battery is mainly used for mobile phones, etc., and the battery element is inserted into an iron can or aluminum can, the opening is closed with a metal lid of the same quality as the can, and the contact is welded with a laser to complete the battery. .

  Laminate thin batteries are also mainly used in mobile phones and the like. In this case, the battery elements are manufactured by covering the battery elements with a laminate film as an exterior material and heat-sealing the openings.

  Thus, there are various forms of lithium ion batteries. However, when aluminum is used for the can, it is not possible to employ a caulking process capable of reducing the cost for the reason described below, and in the current technology, expensive laser welding must be used.

  For example, when making a cylindrical battery, if an aluminum can body is used instead of an iron-based can body, the caulking strength at the opening will be low, and electrolyte leakage will frequently occur from the inside, resulting in safety and reliability. Commercialization is difficult. Therefore, at present, a cylindrical lithium ion battery in which a sealing member is caulked and fixed to an aluminum can is not commercialized.

The specific gravity of aluminum is about one-fourth that of iron, and if an aluminum can body can be applied, it will lead to lighter batteries and high commercial value.
JP-A-9-213335

  The present invention has been made in order to solve the above-described problem. Even when a container is formed from aluminum or an aluminum alloy, a secondary battery excellent in charge / discharge cycle characteristics without leaking liquid is provided. The purpose is to provide.

According to the onset bright, and bottomed cylindrical container made of metal,
An electrode group housed in the container and including a positive electrode and a negative electrode;
A non-aqueous electrolyte held in the electrode group and containing γ-butyrolactone;
A disc-shaped sealing member fixed by caulking to the opening of the container ;
A positive electrode lead having one end electrically connected to the positive electrode and the other end extending through the sealing member;
A secondary battery comprising: a negative electrode lead having one end electrically connected to the negative electrode and the other end penetrating the sealing member and extending to the outside ;
The sealing member is formed of a corrosion-resistant layer containing at least one resin selected from the group consisting of polypropylene, polyethylene, polyphenylene sulfide, polyimide, polyamide, polyimide amide, and fluorine-based resin on a surface facing the electrode group. And at least a part of a surface opposite to the surface facing the electrode group contains at least one resin selected from the group consisting of ethylene propylene terpolymer, isobutylene isoprene rubber and butadiene styrene rubber. Formed of layers ,
A secondary battery having a ratio (h / S) of a height h (mm) of the sealing member to an area S (mm ² ) of a circular bottom is 0.04 [1 / mm] or more is provided. Is done.
Further, according to the present invention, a bottomed cylindrical container made of metal,
An electrode group housed in the container and including a positive electrode and a negative electrode;
A non-aqueous electrolyte held in the electrode group and containing γ-butyrolactone;
A disc-shaped sealing member fixed by caulking to the opening of the container;
A positive electrode lead having one end electrically connected to the positive electrode and the other end extending through the sealing member;
A negative electrode lead having one end electrically connected to the negative electrode and the other end penetrating the sealing member and extending to the outside;
A secondary battery comprising:
The sealing member is formed of a corrosion-resistant layer containing at least one resin selected from the group consisting of polypropylene, polyethylene, polyphenylene sulfide, polyimide, polyamide, polyimide amide, and fluorine-based resin on a surface facing the electrode group. And at least a part of a surface opposite to the surface facing the electrode group contains at least one resin selected from the group consisting of ethylene propylene terpolymer, isobutylene isoprene rubber and butadiene styrene rubber. Formed of layers,
A secondary battery is provided, wherein a ratio of the corrosion-resistant layer is 10 to 99% of a volume of the sealing member.

Further, according to this onset bright, and bottomed cylindrical container made of metal,
An electrode group housed in the container and including a positive electrode and a negative electrode;
A non-aqueous electrolyte that is held in the electrode group and contains a room temperature molten salt;
A disc-shaped sealing member fixed by caulking to the opening of the container ;
A positive electrode lead having one end electrically connected to the positive electrode and the other end extending through the sealing member;
A secondary battery comprising: a negative electrode lead having one end electrically connected to the negative electrode and the other end penetrating the sealing member and extending to the outside ;
The sealing member is formed of a corrosion-resistant layer containing at least one resin selected from the group consisting of polypropylene, polyethylene, polyphenylene sulfide, polyimide, polyamide, polyimide amide, and fluorine-based resin on a surface facing the electrode group. And at least a part of a surface opposite to the surface facing the electrode group contains at least one resin selected from the group consisting of ethylene propylene terpolymer, isobutylene isoprene rubber and butadiene styrene rubber. Formed of layers ,
A secondary battery having a ratio (h / S) of a height h (mm) of the sealing member to an area S (mm ² ) of a circular bottom is 0.04 [1 / mm] or more is provided. Is done.
Further, according to the present invention, a bottomed cylindrical container made of metal,
An electrode group housed in the container and including a positive electrode and a negative electrode;
A non-aqueous electrolyte that is held in the electrode group and contains a room temperature molten salt;
A disc-shaped sealing member fixed by caulking to the opening of the container;
A positive electrode lead having one end electrically connected to the positive electrode and the other end extending through the sealing member;
A negative electrode lead having one end electrically connected to the negative electrode and the other end penetrating the sealing member and extending to the outside;
A secondary battery comprising:
The sealing member is formed of a corrosion-resistant layer containing at least one resin selected from the group consisting of polypropylene, polyethylene, polyphenylene sulfide, polyimide, polyamide, polyimide amide, and fluorine-based resin on a surface facing the electrode group. And at least a part of a surface opposite to the surface facing the electrode group contains at least one resin selected from the group consisting of ethylene propylene terpolymer, isobutylene isoprene rubber and butadiene styrene rubber. Formed of layers,
A secondary battery is provided, wherein a ratio of the corrosion-resistant layer is 10 to 99% of a volume of the sealing member.

  According to the present invention, it is possible to provide a secondary battery having excellent charge / discharge characteristics and high safety and reliability.

  As a result of repeating various studies to achieve the above object, the present inventors have devised a sealing structure and a sealing material, even when aluminum or an aluminum alloy made of an outer container is used. By using a non-aqueous electrolyte, it has been found that a secondary battery excellent in leakage resistance can be realized while having a simple sealing structure in which a sealing member is caulked and fixed to an opening of an outer container.

  In the sealing member, at least the surface facing the electrode group is formed of a corrosion-resistant layer containing at least one resin selected from the group consisting of polypropylene, polyethylene, polyphenylene sulfide, polyimide, polyamide, polyimide amide, and fluorine resin. At the same time, at least a part of the surface opposite to the surface facing the electrode group is at least one selected from the group consisting of ethylene propylene terpolymer (EPDM), isobutylene isoprene rubber (IIR) and butadiene styrene rubber (SBR). The gas permeability of the sealing member can be lowered by forming the liquid-proof layer containing the resin.

  In addition, the corrosion-resistant layer can suppress the erosion of the sealing member due to the strong alkali component generated by the reaction between moisture, which is one of inevitable impurities in the battery, and the lithium salt in the non-aqueous electrolyte. The strength reduction can be suppressed.

  On the other hand, the leak-proof layer can enhance the adhesion between the outer container and the sealing member due to its excellent elasticity.

  Furthermore, a non-aqueous electrolyte containing at least one of γ-butyrolactone and a room temperature molten salt has a low vapor pressure (there is no vapor pressure in the case of a non-aqueous electrolyte composed of a room temperature molten salt), and a high temperature environment of about 45 ° C. Gas generation due to volatilization of the non-aqueous electrolyte below can be suppressed, so by using a combination of the above-mentioned corrosion-resistant layer for maintaining strength and a leak-proof liquid layer for securing adhesion, The problem of deformation and displacement of the sealing member can be avoided. Therefore, in the secondary battery having a simple sealing structure in which the sealing member is caulked and fixed to the opening of the outer container, it is possible to suppress a decrease in hermeticity in a high temperature environment, and to prevent leakage of liquid in a high temperature environment. Prevention and improvement of charge / discharge cycle life can be achieved.

  On the other hand, even when a similar sealing structure is adopted, a solvent typified by a chain carbonate such as ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, which is usually used in a lithium ion battery instead of γ-butyrolactone. When mainly used, these vapor pressures are high and easily volatilize in a high temperature environment, so that the sealing member is deformed or displaced due to gas generation, resulting in a decrease in the adhesion between the sealing member and the container, resulting in airtightness. As a result, the charge / discharge cycle life is shortened.

  For the reasons described above, by adopting the battery configuration of the present invention, it is possible to easily manufacture a secondary battery that is light and has good battery characteristics with good reproducibility.

  Hereinafter, an embodiment of a secondary battery according to the present invention will be described in detail.

This secondary battery basically includes an electrode group having a separator interposed between a positive electrode and a negative electrode, a nonaqueous electrolyte impregnated in the electrode group, and a container in which the electrode group is stored. .

Hereinafter, the positive electrode, the negative electrode, the separator, the nonaqueous electrolyte, and the container will be described.

1) Positive electrode The positive electrode includes a positive electrode current collector and a positive electrode active material layer that is supported on one or both surfaces of the positive electrode current collector and includes an active material and a binder.

  As the positive electrode current collector, for example, a metal foil or a porous plate formed of aluminum or an aluminum alloy can be used.

Examples of the positive electrode active material include various oxides and sulfides. For example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (eg, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxide (eg, Li _x NiO ₂ ) , lithium-cobalt composite oxide (e.g., Li _x CoO _2), lithium nickel cobalt composite oxide (e.g., _{LiNi 1-y Co y O 2} ), lithium manganese cobalt composite oxides (e.g., _{Li x Mn y Co 1-y} O 2 ), spinel type lithium-manganese-nickel composite oxide _{(Li x Mn 2-y Ni} y O 4), lithium phosphates having an olivine structure _{(Li x FePO 4, Li x} Fe 1-y Mn y PO 4, Li x etc. CoPO _4), iron sulfate _{(Fe 2 (SO 4) 3} ), vanadium oxide (e.g. V ₂ O _5), and the like (Note that, x, y is 0-1 It is preferable that the circumference). In addition, conductive polymer materials such as polyaniline and polypyrrole, disulfide-based polymer materials, organic materials such as sulfur (S) and carbon fluoride, and inorganic materials are also included. More preferable positive electrode active materials for secondary batteries include lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, and spinel type lithium manganese nickel composite oxide with high battery voltage. , Lithium manganese cobalt composite oxide, lithium iron phosphate and the like.

In consideration of resistance to γ-butyrolactone, the positive electrode active material is preferably a lithium-containing composite oxide containing Sn, and particularly preferably LiCoO _{2 to} which Sn is added. The effective addition amount of Sn is 0.01 atomic% or more, and is preferably 5 atomic% or less from the viewpoint of increasing the capacity.

  Examples of the conductive agent include acetylene black, carbon black, and graphite.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber.

  The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 18% by weight of the conductive agent, and 2 to 17% by weight of the binder.

2) Negative electrode The negative electrode includes a negative electrode current collector and a negative electrode active material layer that is supported on one or both surfaces of the negative electrode current collector and includes an active material and a binder.

  For the negative electrode current collector, for example, a metal foil or a porous plate formed of nickel, nickel alloy, copper, copper alloy, aluminum, aluminum alloy, or the like can be used.

Examples of the negative electrode active material include lithium metal, lithium alloy, lithium titanium composite oxide (eg, Li ₄ Ti ₅ O ₁₂ ), and metal oxide (eg, amorphous tin oxide, WO ₂ , MoO _2, etc.). TiS ₂ , carbonaceous materials that occlude and release lithium ions, and the like. Of these, carbonaceous materials are preferred. Since the negative electrode containing this carbonaceous material can improve the charge / discharge efficiency of the negative electrode and reduce the negative electrode resistance accompanying charge / discharge, the cycle life and output characteristics of the nonaqueous electrolyte secondary battery can be greatly improved. Can be improved.

  Examples of the carbonaceous material include graphite, isotropic graphite, coke, carbon fiber, spherical carbon, resin-fired carbon, and pyrolytic vapor grown carbon. Among them, a carbon fiber using mesophase pitch as a raw material and a negative electrode containing spherical carbon are preferable because they can improve cycle life because of high charging efficiency. Furthermore, the orientation of carbon fibers made from mesophase pitch or spherical carbon graphite crystals is preferably radial. Carbon fibers and spherical carbon made from mesophase pitch are carbonized by heat-treating raw materials such as petroleum pitch, coal tar and resin at 550 ° C. to 2000 ° C., or graphite by heat treatment at 2000 ° C. or higher. Can be produced.

The carbonaceous material is preferably surface spacing d ₀₀₂ of (002) plane of graphite crystal obtained from X-ray diffraction peaks in the range of 0.3354Nm～0.40Nm. The carbonaceous material preferably has a specific surface area of 0.5 m ² / g or more by the BET method. A more preferable range of the specific surface area is 1 m ² / g or more.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), carboxymethylcellulose (CMC), and fluorine-based binder. Rubber or the like can be used.

  The negative electrode is produced by suspending a conductive agent and a binder in an appropriate solvent in a negative electrode active material, applying the suspension to a current collector, drying and pressing to form a strip electrode.

  Examples of the conductive agent include acetylene black, carbon black, and graphite.

  The compounding ratio of the negative electrode active material, the conductive agent and the binder is preferably in the range of 70 to 96% by weight of the negative electrode active material, 2 to 28% by weight of the conductive agent, and 2 to 28% by weight of the binder. If the amount of the conductive agent is less than 2% by weight, there is a possibility that the current collecting property is lacking and the large current characteristic is deteriorated. Further, if the amount of the binder is less than 2% by weight, the binding performance between the mixture layer and the current collector is lacking, and the cycle performance may be deteriorated. On the other hand, from the viewpoint of increasing the capacity, the amount of the conductive agent and the binder is preferably 28% by weight or less.

  In addition, in the negative electrode configuration, particularly when a negative electrode active material that is nobler than 1.0 V with respect to the potential of metallic lithium is used, the negative electrode current collector is preferably formed of, for example, aluminum or an aluminum alloy. . With such a configuration, when aluminum is used for the bottomed cylindrical container, the bottomed cylindrical container made of aluminum is eluted even when the negative electrode touches the bottomed cylindrical container. Without this, stable battery characteristics can be maintained. From the viewpoint of weight reduction, it is preferable that the negative electrode current collector and the bottomed cylindrical container be made of aluminum or an aluminum alloy by using a negative electrode active material that is nobler than 1.0 V with respect to the potential of metallic lithium. .

In this case, as the negative electrode active material, a material in which the operating potential of the negative electrode is nobler than 1.0 V with respect to the potential of metallic lithium, such as tungsten oxide, molybdenum oxide, iron sulfide, titanium sulfide, lithium titanate, etc. Can be used. In particular, it is preferably a composite oxide containing lithium and titanium, or a composite sulfide containing lithium and iron. In particular, it is represented by the chemical formula Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3), and is a spinel type. A lithium titanate having a structure or iron sulfide represented by Li _x FeS _y (0 ≦ x ≦ 4, 0.9 ≦ y ≦ 2.1) is preferable.

3) Separator A porous separator can be used as the separator.

  Examples of the porous separator include a porous film containing polyethylene, polypropylene, cellulose, or polyvinylidene fluoride (PVdF), and a synthetic resin nonwoven fabric. Among these, a porous film made of polyethylene, polypropylene, or both is preferable because it can improve the safety of the secondary battery.

4) Nonaqueous Electrolyte As long as this nonaqueous electrolyte contains at least one of γ-butyrolactone and a room temperature molten salt, the form is not particularly limited, and can be liquid, gel, or solid.

  As a preferable non-aqueous electrolyte, for example, a liquid non-aqueous electrolyte in which an electrolyte is dissolved in an organic solvent can be exemplified.

  As the organic solvent, γ-butyrolactone is a main solvent, and for example, cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC) may be mixed as appropriate.

  The content of γ-butyrolactone in the organic solvent is desirably more than 50% by volume and 95% by volume or less. A more preferable range is 60% by volume or more and 80% by volume or less.

  As additives, a small amount of chain carbonate such as dimethyl carbonate (DMC), methyl ethyl carbonate (MEC) and diethyl carbonate (DEC), cyclic ether such as tetrahydrofuran (THF) and 2 methyl tetrahydrofuran (2MeTHF), dimethoxyethane A chain ether such as (DME), acetonitrile (AN), sulfolane (SL), trifluoropropylene, an aromatic compound, or the like may be mixed. These organic solvents can be used alone or in the form of a mixture of two or more.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), and trifluoro lithium methanesulfonic acid (LiCF ₃ SO _3), bis (trifluoromethylsulfonyl) imide lithium _{[LiN (CF 3 SO 2)} 2] include lithium salts such as. Most preferably, lithium tetrafluoroborate (LiBF ₄ ), which exists stably in γ-butyrolactone and has a high dielectric constant, is the main electrolyte.

  The electrolyte is preferably dissolved in the range of 0.5 to 2.0 mol / L with respect to the organic solvent.

  Moreover, a room temperature molten salt containing a lithium salt can be used as the non-aqueous electrolyte.

  The room temperature molten salt refers to a compound that can exist as a liquid at room temperature (15 to 25 ° C.) among organic salts composed of a combination of an organic cation and an anion. Examples of the room temperature molten salt include a room temperature molten salt that exists alone as a liquid, a room temperature molten salt that becomes a liquid when mixed with an electrolyte, and a room temperature molten salt that becomes a liquid when dissolved in an organic solvent. In general, the melting point of a room temperature molten salt used for a nonaqueous electrolyte battery is 25 ° C. or less.

As the lithium salt, a lithium salt having a wide potential window, which is generally used for lithium secondary batteries, is used. For example, LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ), LiN (CF ₃ SC (C ₂ F ₅ SO ₂ ) _3, etc. However, these are not limited, and these may be used alone or in combination of two or more.

  The lithium salt content is desirably 0.1 to 3 mol / L. This is due to the reason explained below. If the content of the lithium salt is less than 0.1 mol / L, the ion conductivity of the non-aqueous electrolyte is lowered and high high current / low temperature discharge characteristics may not be obtained. On the other hand, when the content of the lithium salt exceeds 3 mol / L, the melting point of the non-aqueous electrolyte is increased and it may be difficult to maintain a liquid state at room temperature. A more preferable range of the lithium salt content is 1 to 2 mol / L.

Examples of the room temperature molten salt include those having a quaternary ammonium organic cation having a skeleton represented by the formula (1) or those having an imidazolium cation having a skeleton represented by the formula (2).

However, in the formula (2), R1 and R2 are _{each, C n H 2n + 1 (} n = 1~6), also may be the same or different from each other, R3 is H or C _n H _{2n +1} (n = 1 to 6).

  Examples of the quaternary ammonium organic cation having a skeleton represented by the formula (1) include imidazolium ions such as dialkylimidazolium and trialkylimidazolium, tetraalkylammonium ions, alkylpyridinium ions, pyrazolium ions, pyrrolidinium ions, And piperidinium ions. In particular, an imidazolium cation having a skeleton represented by the formula (2) is preferable.

  Examples of the tetraalkylammonium ion include, but are not limited to, trimethylethylammonium ion, trimethylpropylammonium ion, trimethylhexylammonium ion, and tetrapentylammonium ion.

  Examples of the alkylpyridinium ion include N-methylpyridinium ion, N-ethylpyridinium ion, N-propylpyridinium ion, N-butylpyridinium ion, 1-ethyl-2-methylpyridinium ion, 1-butyl-4-methylpyridinium ion, Although 1-butyl-2,4 dimethyl pyridinium ion etc. are mentioned, it is not limited to these.

  In addition, the normal temperature molten salt which has these cations may be used independently, or may be used in mixture of 2 or more types.

  The imidazolium cation having a skeleton represented by the formula (2) is not particularly limited. For example, as the dialkyl imidazolium ion, 1,3-dimethylimidazolium ion, 1-ethyl-3-methylimidazolium ion, 1-methyl-3-ethylimidazolium ion, 1-methyl-3-butylimidazolium ion 1-butyl-3-methylimidazolium ion, and the like. Examples of the trialkylimidazolium ion include 1,2,3-trimethylimidazolium ion, 1,2-dimethyl-3-ethylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion, and 1-butyl-2. , 3-dimethylimidazolium ion and the like.

  In addition, the normal temperature molten salt which has these cations may be used independently, or may mix and use 2 or more types.

5) Bottomed cylindrical container As the bottomed cylindrical container, a metal container can be used. The material is preferably aluminum or an aluminum alloy from the viewpoints of weight reduction, caulking workability, and the possibility of Fe elution during overdischarge. Among aluminum alloys, an aluminum alloy to which a small amount of Mg, Fe, Si, or the like is added is preferable because it can increase the caulking strength of the sealing portion. The thickness is preferably 0.2 mm or more and 0.5 mm or less in consideration of weight reduction and strength, although it depends on the material.

6) Sealing member The sealing member includes a leak-proof layer and a corrosion-resistant layer. The leak-proof layer suppresses the movement of gas from the inside and outside, and improves the adhesion between the sealing member and the lead part, and the sealing member and the bottomed cylindrical container, and the corrosion-resistant layer prevents the movement of gas from the inside and outside. While suppressing, it has the effect which suppresses erosion of the sealing member by a nonaqueous electrolyte.

  For the leak-proof layer, ethylene propylene terpolymer (EPDM), isobutylene isoprene rubber (IIR), butadiene styrene rubber (SBR), or the like can be used. The type of the resin that forms the leak-proof layer can be one type or two or more types.

  The rubber material constituting the leak-proof layer preferably has a maximum elongation (%) of 700 (%) or more and 1000% or less based on the ASTM (D638) test method. Thereby, adhesiveness with an exterior container increases and it can suppress effectively movement of gas inside and outside and a nonaqueous electrolyte.

  From the viewpoint of suppressing moisture penetration, the leak-proof layer preferably contains IIR or EPDM, which is a non-diene rubber. This is because a diene rubber containing a double bond such as SBR is susceptible to ozone attack and is inferior in weather resistance, and therefore there is a possibility that the moisture penetration inhibiting effect is insufficient.

  For the corrosion resistant layer, polypropylene (PP), polyethylene (PE), polyphenylene sulfide, polyimide, polyamide, polyimide amide, fluorine-based resin, or the like can be used. Among these, polypropylene (PP) and polyethylene (PE) which are excellent in alkali resistance are preferable.

  Examples of the polyamide include MC nylon, 6 nylon, 66 nylon and the like.

  Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / ethylene copolymer (ETFE), and tetrafluoroethylene / perfluoroalkyl vinyl ether. Examples thereof include a polymer (PFA), polychlorotrifluoroethylene (PCTFE), and polyvinylidene fluoride (PVDF). Since any fluororesin is rich in alkali resistance, the effect of suppressing erosion by the nonaqueous electrolyte of the sealing member is high. Among these, PTFE, FEP, and PCTFE having a water supply rate of 0.01% or less are preferable.

  The type of resin that forms the corrosion-resistant layer can be one type or two or more types.

  The water absorption rate (24 hours) of the resin constituting the corrosion-resistant layer is preferably 0.01% or less (including 0%). Thereby, it becomes possible to suppress the invasion of moisture from the outside and effectively suppress the erosion by the non-aqueous electrolyte.

  Moreover, it is preferable that elongation (%) based on the ASTM (D638) test method of the resin constituting the corrosion-resistant layer is 200% or more and 700% or less. Thereby, the adhesiveness of an exterior container and a sealing member improves, and the penetration | invasion of the nonaqueous electrolyte to a leak-proof liquid layer can be suppressed.

  Based on the above-described reason, a more preferable configuration of the sealing member includes a leak-proof layer containing isobutylene isoprene rubber (IIR) and a corrosion-resistant layer containing polyethylene or polypropylene. The same can be said for an ambient temperature molten salt having a quaternary salt as a solute as well as an electrolytic solution having a lithium salt as a solute.

  Further, the sealing member is eroded by the strong alkali component in the battery, and the effect of suppressing this erosion appears remarkably when the proportion of the corrosion-resistant layer is 10 to 99% of the volume of the sealing member. By increasing the proportion of the corrosion-resistant layer therein, it is possible to reduce the permeation amount of the non-aqueous electrolyte that greatly affects the battery performance. In this case, since it becomes possible to reduce the whole thickness of the sealing member, the volume of the power generation element can be increased, and the capacity of the battery can be increased. In order to obtain excellent charge / discharge cycle characteristics at high temperatures, the proportion of the corrosion-resistant layer is desirably 40% or more and 90% or less of the volume of the sealing member.

  An embodiment of a secondary battery according to the present invention will be described with reference to the drawings. 1 is a partially cutaway perspective view showing a cylindrical secondary battery according to a first embodiment of the present invention, FIG. 2 is a schematic cross-sectional view of the cylindrical secondary battery of FIG. 1, and FIG. It is the typical fragmentary sectional view which showed the cylindrical secondary battery which concerns on the 2nd Embodiment of this invention.

  As shown in FIG. 1, an electrode group 2 is accommodated in a bottomed cylindrical container 1. The electrode group 2 has a structure in which a positive electrode 3 and a negative electrode 4 are wound in a spiral shape with a separator 5 interposed therebetween. The liquid nonaqueous electrolyte is held in the electrode group 2. The disk-shaped sealing member 6 is attached to the opening of the container 1 by crimping and fixing the upper end 1a of the opening inward after the diameter of the opening of the container 1 is reduced in the radial direction. The sealing member 6 is formed by integrating a corrosion-resistant layer 7 disposed on a surface facing the electrode group 1 and a leakage-resistant layer 8 disposed outside the corrosion-resistant layer 7.

  One end of the positive electrode lead 9 is electrically connected to the positive electrode 3, and the other end penetrates the sealing member 6 and is drawn to the outside. One end of the negative electrode lead 10 is electrically connected to the negative electrode 4, and the other end penetrates the sealing member 6 and is drawn to the outside. The positive electrode lead 9 and the negative electrode lead 10 can be formed from a metal wire such as an aluminum wire, for example.

  Although only one of the positive electrode lead 9 and the negative electrode lead 10 can be passed through the sealing member 6 and pulled out to the outside, in this case, it is necessary to weld the remaining leads to the bottom of the container, and space for this purpose. Must be provided in the container 1. As shown in FIGS. 1 and 2, by pulling out both leads to the outside through the sealing member 6, the space for welding the leads to the bottom of the container becomes unnecessary, so the volume of the electrode group 1 that can be accommodated in the container 1 The capacity can be increased and the capacity can be increased.

  In FIGS. 1 and 2 described above, the example in which the sealing member 6 having the two-layer structure of the corrosion-resistant layer 7 and the leakage-resistant layer 8 is used has been described, but the present invention is not limited to this. For example, as shown in FIG. 3, a surface 7 a facing the electrode group 1, an outermost periphery (a surface in contact with the inner periphery of the container 1) 7 b, an inner peripheral surface 7 c of a through hole of each of the positive electrode lead 9 and the negative electrode lead 10 Can be formed with the anti-corrosion layer 7 and other portions can be formed with the leak-proof liquid layer 8. In this case, the anti-corrosion layer 7 is disposed on the surface facing the electrode group 1, and the anti-corrosion layer 7 and the leak-proof liquid layer 8 are disposed on the surface opposite to the surface facing the electrode group 1.

In the disk-shaped sealing member illustrated in FIGS. 1 to 3 described above, the ratio (h / S) between the height h (mm) of the sealing member and the area S (mm ² ) of the circular bottom surface is 0. When it is 0.04 [1 / mm] or more, it is possible to effectively suppress the ingress of moisture from the outside of the battery and the leakage of the non-aqueous electrolyte to the outside of the battery.

  In FIGS. 1 to 3 described above, the diameter of the opening of the container is reduced, and then the upper end of the opening is bent inwardly. However, the opening of the container is not reduced without reducing the diameter of the opening. The present invention can also be applied to caulking by bending the upper end inward.

[Example]
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples as long as the gist of the invention is not exceeded.

(Examples 1 to 10)
<Preparation of positive electrode>
First, 90% by weight of lithium cobalt oxide (LiCo _0.97 Sn _0.03 O ₂ ) powder containing Sn as a positive electrode active material, 3% by weight of acetylene black, 3% by weight of graphite, and 4% by weight of polyvinylidene fluoride (PVdF) are added to N -In addition to methyl pyrrolidone (NMP), a slurry is obtained by mixing, and this slurry is applied to both sides of a current collector made of 15 μm aluminum foil, excluding the lead weld, and then dried and pressed to reduce the electrode density. A positive electrode of 3.0 g / cm ³ was produced.

<Production of negative electrode>
A weight ratio of Li ₄ Ti ₅ O ₁₂ as a negative electrode active material, coke fired at 1200 ° C. (d ₀₀₂ is 0.3465 nm, average particle size 3 μm) and polyvinylidene fluoride (PVdF) as a conductive material is 90: 5 in weight ratio. : N-methylpyrrolidone (NMP) solution was added so as to be mixed, and the obtained slurry was applied to an aluminum foil having a thickness of 15 μm excluding lead welds, dried, and then pressed. A negative electrode was produced.

<Production of electrode group>
A positive electrode lead made of an aluminum wire was welded to the positive electrode current collector, and a negative electrode lead made of an aluminum wire was welded to the negative electrode current collector.

  After laminating a positive electrode, a separator made of a polyethylene porous film having a thickness of 25 μm, a negative electrode, and a separator in this order, they were wound in a spiral shape to produce an electrode group. The produced electrode group was inserted into an aluminum bottomed cylindrical container and vacuum-dried at 80 ° C. for 24 hours.

<Preparation of liquid nonaqueous electrolyte>
By dissolving 1.5 mol / L of lithium tetrafluoroborate (LiBF ₄ ) as an electrolyte in a mixed solvent (volume ratio 20:80) of ethylene carbonate (EC) and γ-butyrolactone (GBL), a liquid non-aqueous electrolyte ( Non-aqueous electrolyte) was prepared.

<Preparation of sealing member>
The sealing member is a combination of a circular plate of isobutylene isoprene rubber (IIR) as a liquid-proof layer and a circular plate of polyethylene (PE) as a corrosion-resistant layer, and the proportion of PE is 10 to 99% (10 20, 30, 40, 50, 60, 70, 80, 90, 99), and a height h having a two-layer structure of a leak-proof layer and a corrosion-resistant layer as shown in FIG. A 4 mm sealing member was produced. The ratio (h / S) between the height h (mm) of the sealing member and the area S (mm ² ) of the circular bottom surface was 0.05 [1 / mm].

  After injecting the liquid non-aqueous electrolyte into the bottomed cylindrical container containing the electrode group, a sealing member is placed in the opening of the container so that the corrosion-resistant layer faces the electrode group, and the tip of the positive electrode lead and the negative electrode lead Was inserted into the sealing member and penetrated. Next, after compressing the opening of the container in the radial direction to reduce the diameter, the upper end of the opening is bent inward to fix the sealing member to the opening of the container, and the structure shown in FIGS. A cylindrical non-aqueous electrolyte secondary battery was manufactured.

(Examples 11 to 24)
A cylindrical non-aqueous electrolyte secondary battery was manufactured in the same manner as described in Example 1 except that the corrosion-resistant layer and leak-proof layer of the sealing member were used in the combinations shown in Tables 1 and 2 below. . In addition, 66 nylon was used as the polyamide described in Table 1.

(Example 25)
1 mol of LiBF ₄ is dissolved in 1 liter of a room temperature molten salt (EMIBF ₄ ) composed of 1-methyl-3-ethylimidazolium ion (MEI ⁺ ) and tetrafluoroborate ion (BF ₄ ⁻ ). A non-aqueous electrolyte was prepared. This room temperature molten salt was liquid at 20 ° C., and the prepared nonaqueous electrolyte was also liquid at 20 ° C.

  A secondary battery similar to that of Example 5 described above was produced except that the obtained nonaqueous electrolyte was used.

(Example 26)
A non-aqueous electrolyte was prepared by dissolving 1 mol of LiBF ₄ in 1 liter of room temperature molten salt (BPyBF ₄ ) composed of N-butylpyridinium ion (BPy ⁺ ) and BF ₄ ⁻ . This room temperature molten salt was liquid at 20 ° C., and the prepared nonaqueous electrolyte was also liquid at 20 ° C.

  A secondary battery similar to that of Example 5 described above was produced except that the obtained nonaqueous electrolyte was used.

(Example 27)
Al alloy (JIS 3005 alloy (1.25% Mg-0.09% Zn-0.4% Si-1.2% Mn-0.5% Fe-0.1% Cu-0.2% Ti-Al [ wt.%]), and a secondary battery similar to that of Example 5 described above was manufactured, except that a container made of) was used.

(Comparative Example 1)
Using a sealing member having a PE ratio of 50%, lithium tetrafluoroborate (LiBF ₄ ) as an electrolyte was mixed in a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (volume ratio 20:80). A secondary battery similar to that of Example 5 was completed, except that a nonaqueous electrolyte prepared by dissolving 5 mol / L was used.

(Comparative Example 2)
Using a sealing member having a PE ratio of 50%, lithium tetrafluoroborate (LiBF ₄ ) as an electrolyte was mixed in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio 20:80). A secondary battery similar to that of Example 5 was completed, except that a nonaqueous electrolyte prepared by dissolving 5 mol / L was used.

(Comparative Example 3)
Using a sealing member having a PE ratio of 50%, lithium tetrafluoroborate (LiBF ₄ ) as an electrolyte was mixed in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 20:80). A secondary battery similar to that of Example 5 was completed, except that a nonaqueous electrolyte prepared by dissolving 5 mol / L was used.

(Comparative Example 4)
A secondary battery similar to that of Example 1 was produced except that the sealing member was IIR alone.

(Comparative Example 5)
A secondary battery similar to that of Example 1 was produced except that the sealing member was PE alone.

  With respect to the produced secondary battery, the charge / discharge cycle was repeated 200 times in a 45 ° C. environment, and the capacity retention rate at the 200th cycle relative to the initial capacity was measured. The results are shown in Tables 1 and 2 below.

In addition, the maximum elongation (%) based on the ASTM (D638) test method of the rubber material used in the leak-proof layer of Examples 1 to 28, the water absorption rate (24 hours) of the resin used in the corrosion-resistant layer, and ASTM ( D638) Elongation (%) based on the test method is also shown in Tables 1 and 2 below.

  As is clear from the results of Tables 1 and 2, two of Examples 1 to 27 in which a nonaqueous electrolyte containing γ-butyrolactone or a room temperature molten salt and a sealing member provided with a corrosion-resistant layer and a liquid-resistant layer were combined. According to the secondary battery, it was found that an excellent cycle life could be realized even at a high temperature of about 45 ° C.

  The reason for this can be considered as follows. As shown in Comparative Example 4, when the sealing member is composed of only the leak-proof layer, it is eroded by the strong alkali component from the surface that directly contacts the nonaqueous electrolyte, loses its function as a sealing material, leaks, and has battery performance. Decreases. On the other hand, as shown in Comparative Example 5, when the sealing member is composed only of the corrosion-resistant layer, the reaction with the non-aqueous electrolyte can be suppressed, but the elasticity of the sealing member itself is lost, the airtightness is reduced, and from the outside Moisture and gas can easily enter, reducing battery performance.

  As shown in Examples 1 to 27, by using a composite material of a leak-proof liquid layer and a corrosion-resistant layer, both elasticity and resistance to a non-aqueous electrolyte can be achieved, and battery performance can be maintained for a long time. it can.

  Even when a sealing member made of the above composite material is used, if a chain carbonate (DMC, EMC, DEC) having a high vapor pressure is used for the nonaqueous electrolyte as in Comparative Examples 1 to 3, gasification of the nonaqueous electrolyte is performed. As a result, the internal pressure of the battery rises, the sealing member is pushed out, the airtightness is lowered, and the battery performance is lowered.

  Thus, it was found that by adopting the configuration of the present invention, good battery performance can be maintained for a long time even with a simple sealing method.

  By comparing Examples 1 to 10 in which the volume ratio of the leakage-proof layer and the corrosion-resistant layer was changed, two of Examples 4 to 9 in which the corrosion-resistant layer was 40% or more and 90% or less of the volume of the sealing member. According to the secondary battery, it can be understood that the capacity retention rate at the 200th cycle is 90% or higher, which is higher than those of Examples 1 to 3.

  Moreover, Example 5 which contains PE or PP as a corrosion-resistant layer by comparing Example 5 and Examples 11 to 18 with the type of the liquid-resistant layer fixed to IIR and changing the type of the corrosion-resistant layer. 11 shows that the secondary battery of No. 11 has a high capacity retention rate at the 200th cycle.

  Furthermore, when the type of the corrosion-resistant layer was fixed to PE or PP and the type of the liquid-resistant layer was compared, among Examples 5, 11, 19, 20, 22, and 23, the leakage-resistant layer contained IIR. The capacity retention rate at the 200th cycle of the secondary batteries of Examples 5 and 11 was high.

  From these results, it can be understood that a combination of a leak-proof liquid layer containing IIR and a corrosion-resistant layer containing PE or PP is desirable in order to improve charge / discharge cycle characteristics at high temperatures.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a partially cutaway perspective view showing a cylindrical secondary battery according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the cylindrical secondary battery in FIG. 1. The typical fragmentary sectional view which showed the cylindrical secondary battery which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Bottomed cylindrical container, 1a ... Bending part, 2 ... Electrode group, 3 ... Positive electrode, 4 ... Negative electrode, 5 ... Separator, 6 ... Sealing member, 7 ... Corrosion-resistant layer, 8 ... Leak-proof liquid layer, 9 ... Positive electrode Lead, 10 ... negative electrode lead.

Claims (7)

A bottomed cylindrical container made of metal,
An electrode group housed in the container and including a positive electrode and a negative electrode;
A non-aqueous electrolyte held in the electrode group and containing γ-butyrolactone;
A disc-shaped sealing member fixed by caulking to the opening of the container ;
A positive electrode lead having one end electrically connected to the positive electrode and the other end extending through the sealing member;
A secondary battery comprising: a negative electrode lead having one end electrically connected to the negative electrode and the other end penetrating the sealing member and extending to the outside ;
The sealing member is formed of a corrosion-resistant layer containing at least one resin selected from the group consisting of polypropylene, polyethylene, polyphenylene sulfide, polyimide, polyamide, polyimide amide, and fluorine-based resin on a surface facing the electrode group. And at least a part of a surface opposite to the surface facing the electrode group contains at least one resin selected from the group consisting of ethylene propylene terpolymer, isobutylene isoprene rubber and butadiene styrene rubber. Formed of layers ,
A secondary battery , wherein a ratio (h / S) of a height h (mm) of the sealing member to an area S (mm ² ) of a circular bottom is 0.04 [1 / mm] or more . A bottomed cylindrical container made of metal,
An electrode group housed in the container and including a positive electrode and a negative electrode;
A non-aqueous electrolyte held in the electrode group and containing γ-butyrolactone;
A disc-shaped sealing member fixed by caulking to the opening of the container;
A positive electrode lead having one end electrically connected to the positive electrode and the other end extending through the sealing member;
A negative electrode lead having one end electrically connected to the negative electrode and the other end penetrating the sealing member and extending to the outside;
A secondary battery comprising:
The sealing member is formed of a corrosion-resistant layer containing at least one resin selected from the group consisting of polypropylene, polyethylene, polyphenylene sulfide, polyimide, polyamide, polyimide amide, and fluorine-based resin on a surface facing the electrode group. And at least a part of a surface opposite to the surface facing the electrode group contains at least one resin selected from the group consisting of ethylene propylene terpolymer, isobutylene isoprene rubber and butadiene styrene rubber. Formed of layers,
The secondary battery according to claim 1, wherein a ratio of the corrosion-resistant layer is 10 to 99% of a volume of the sealing member . A bottomed cylindrical container made of metal,
An electrode group housed in the container and including a positive electrode and a negative electrode;
A non-aqueous electrolyte that is held in the electrode group and contains a room temperature molten salt;
A disc-shaped sealing member fixed by caulking to the opening of the container ;
A positive electrode lead having one end electrically connected to the positive electrode and the other end extending through the sealing member;
A secondary battery comprising: a negative electrode lead having one end electrically connected to the negative electrode and the other end penetrating the sealing member and extending to the outside ;
The sealing member is formed of a corrosion-resistant layer containing at least one resin selected from the group consisting of polypropylene, polyethylene, polyphenylene sulfide, polyimide, polyamide, polyimide amide, and fluorine-based resin on a surface facing the electrode group. And at least a part of a surface opposite to the surface facing the electrode group contains at least one resin selected from the group consisting of ethylene propylene terpolymer, isobutylene isoprene rubber and butadiene styrene rubber. Formed of layers ,
A secondary battery , wherein a ratio (h / S) of a height h (mm) of the sealing member to an area S (mm ² ) of a circular bottom is 0.04 [1 / mm] or more . A bottomed cylindrical container made of metal,
An electrode group housed in the container and including a positive electrode and a negative electrode;
A non-aqueous electrolyte that is held in the electrode group and contains a room temperature molten salt;
A disc-shaped sealing member fixed by caulking to the opening of the container;
A positive electrode lead having one end electrically connected to the positive electrode and the other end extending through the sealing member;
A negative electrode lead having one end electrically connected to the negative electrode and the other end penetrating the sealing member and extending to the outside;
A secondary battery comprising:
The sealing member is formed of a corrosion-resistant layer containing at least one resin selected from the group consisting of polypropylene, polyethylene, polyphenylene sulfide, polyimide, polyamide, polyimide amide, and fluorine-based resin on a surface facing the electrode group. And at least a part of a surface opposite to the surface facing the electrode group contains at least one resin selected from the group consisting of ethylene propylene terpolymer, isobutylene isoprene rubber and butadiene styrene rubber. Formed of layers,
The secondary battery according to claim 1, wherein a ratio of the corrosion-resistant layer is 10 to 99% of a volume of the sealing member . The container, the secondary battery according to claim 1 to 4 any one of claims, characterized in that it is formed of aluminum or an aluminum alloy.   The secondary battery according to claim 1, wherein the corrosion-resistant layer contains at least one of polypropylene and polyethylene, and the liquid-proof layer contains isobutylene isoprene rubber. The secondary battery according to claim 1, wherein the negative electrode includes a negative electrode active material that is nobler than 1.0 V with respect to a potential of metallic lithium.

Images