JP2008251433A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of improving a cycle characteristic while reducing the weight thereof even when an armoring can is used as a negative electrode. <P>SOLUTION: A battery element 20 having a laminate structure of a positive electrode 21, a negative electrode 22 and a separator 23 is housed in the armoring can 11. The armoring can 11 is formed of a metal material containing aluminum, and a reaction suppression layer 31 formed of copper or nickel is formed on its inside surface. An alloying reaction of lithium included in an electrolyte held to the separator 23 with aluminum included in the armoring can 11 is suppressed by the reaction suppression layer 31. Since the inside surface of the armoring can 11 faces a positive electrode collector 21A positioned at an end on a rolling outer periphery side of the battery element 20 through the reaction suppression layer 31 and the separator 23, excessive heat generation is suppressed in abnormality such as breakage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery accommodated in an outer can made of a material in which a positive electrode, a negative electrode, and an electrolyte contain aluminum.

  In recent years, mobile electronic devices such as mobile phones, PDAs (Personal Digital Assistants) or notebook computers have been energetically reduced in size and weight, and as part of these efforts, Improvement of the energy density of a battery as a driving power source, particularly a secondary battery is strongly desired. As a secondary battery capable of obtaining a high energy density, a lithium ion secondary battery using a material capable of inserting and extracting lithium (Li) such as a carbon material in a negative electrode has been commercialized, and its market is It is expanding.

  In a lithium ion secondary battery, a porous film made of a synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene or the like or a porous film made of a ceramic is used as a separator that separates a positive electrode and a negative electrode. The separator prevents a short circuit of current due to contact between both electrodes, while holding an electrolyte allows lithium ions to pass therethrough and allows a battery reaction between both electrodes.

As another secondary battery capable of obtaining a high energy density, there is a lithium metal secondary battery using lithium metal for the negative electrode and utilizing only precipitation and dissolution reactions of lithium metal for the negative electrode reaction. Lithium metal secondary batteries have a large theoretical electrochemical equivalent of 2054 mAh / cm ^{3 of} lithium metal, which is equivalent to 2.5 times that of graphite used in lithium ion secondary batteries, so it is higher than lithium ion secondary batteries. The energy density is expected to be obtained. Until now, research and development regarding practical application of lithium metal secondary batteries has been made by many researchers and the like (for example, see Non-Patent Document 1).

  Recently, a secondary battery has been developed in which the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof (for example, see Patent Document 1). .) In this method, a carbon material capable of inserting and extracting lithium is used for the negative electrode, and lithium is deposited on the surface of the carbon material during charging. According to this secondary battery, it can be expected to achieve a high energy density as in the case of the lithium metal secondary battery.

On the other hand, in such a secondary battery, weight reduction has been studied by using an outer can made of aluminum having a specific gravity smaller than that of stainless steel as a container for accommodating a positive electrode and a negative electrode (see, for example, Patent Document 2). ).
Edited by Jean-Paul Gabano, "Lithium Batteries", London, New York, Academic Press, 1983 International Publication No. 01/22519 Pamphlet JP-A-6-163025

  However, lithium as a battery reactant has a property of causing an alloying reaction with aluminum. For this reason, when the outer can made of aluminum is used as the negative electrode, the outer can itself is eroded, the mechanical strength is lowered, and the reliability of the battery may be impaired. Furthermore, since the charge / discharge efficiency of lithium and aluminum is relatively low, it may cause deterioration of cycle characteristics.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a battery capable of improving cycle characteristics while achieving weight reduction even when an outer can is used as a negative electrode.

  The battery of the present invention includes a battery element having a positive electrode including a material capable of inserting and extracting lithium, a negative electrode including a material capable of inserting and extracting lithium, and an outer can that accommodates the battery element. It is a thing. Here, the outer can is made of a metal material containing aluminum, is short-circuited with the negative electrode, and has a reaction suppression layer that suppresses the reaction between aluminum and lithium on the inner surface thereof.

  In the battery of the present invention, the reaction suppressing layer suppresses an alloying reaction between lithium as a battery reactant and aluminum constituting the outer can connected to the negative electrode. In particular, when the positive electrode has a structure in which a positive electrode active material layer is selectively provided on the positive electrode current collector, and the positive electrode current collector is exposed so as to face the inner surface of the outer can, The safety of the battery at the time of abnormality is improved.

  According to the battery of the present invention, since the reaction suppression layer that suppresses the reaction between aluminum and lithium is provided on the inner surface of the outer can, the structure of the outer can can be short-circuited with the negative electrode. A metal material containing aluminum can be used as the material. For this reason, the degree of freedom in design is widened, and the cycle characteristics can be improved while reducing the weight.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Each drawing schematically shows the shape, size, and arrangement relationship to the extent that the present invention can be understood for each component, and does not necessarily match the actual size.

  1 and 2 show a cross-sectional structure of a secondary battery as an embodiment of the present invention. The cross section shown in FIG. 1 and the cross section shown in FIG. 2 are in a positional relationship orthogonal to each other. That is, FIG. 2 is a cross-sectional view in the arrow direction along the line II-II shown in FIG. This secondary battery is a so-called rectangular shape, and has a flat battery element 20 accommodated inside an outer can 11 having a substantially hollow rectangular parallelepiped shape.

  The outer can 11 is made of a metal material containing at least aluminum (Al), and also has a function as a negative electrode terminal. Specifically, in addition to a simple substance of aluminum, an outer can using an alloy in which elements such as copper (Cu), silicon (Si), manganese (Mn), magnesium (Mg), and zinc (Zn) are appropriately added to aluminum. 11 can be configured. A reaction suppression layer 31 is provided on the entire inner surface of the outer can 11. The reaction suppression layer 31 is excellent in chemical resistance and reduction resistance, and is made of a metal that does not form an alloy with lithium, such as a simple substance of copper or an alloy thereof, or a simple substance of nickel (Ni) or an alloy thereof. For example, it has a thickness of 3 μm or more and 100 μm or less. Examples of the metal that does not form an alloy with lithium include iron (Fe) and cobalt (Co) in addition to copper and nickel. Moreover, as a material which comprises the reaction suppression layer 31, resin, a metal oxide, etc. other than the above metals can be used, Furthermore, what compounded them is applicable. Specifically, the reaction suppression layer 31 can also be composed of oxides such as aluminum oxide and silicon dioxide, polymer materials such as fluororesin, polyamideimide, polyimide and epoxy resin, and composite materials containing these. In that case, for example, the thickness may be 5 μm or more and 100 μm or less.

  The outer can 11 has a structure in which one end is closed and the other end is opened, and the inside is sealed by attaching an insulating plate 12 and a battery lid 13 to the open end. The insulating plate 12 is made of polypropylene or the like, and is disposed on the battery element 20 perpendicular to the winding peripheral surface. The battery lid 13 is made of, for example, the same material as the outer can 11 and has a function as a negative electrode terminal together with the outer can 11. A terminal plate 14 serving as a positive electrode terminal is disposed outside the battery lid 13. A through hole is provided near the center of the battery lid 13, and a positive electrode pin 15 electrically connected to the terminal plate 14 is inserted into the through hole. The terminal plate 14 and the battery lid 13 are electrically insulated by an insulating case 16, and the positive electrode pin 15 and the battery lid 13 are electrically insulated by a gasket 17. The insulating case 16 is made of, for example, polybutylene terephthalate. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  A cleavage valve 18 and an electrolyte injection hole 19 are provided near the periphery of the battery lid 13. The cleaving valve 18 is electrically connected to the battery lid 13 and is cleaved when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating, thereby suppressing an increase in the internal pressure. . The electrolyte injection hole 19 is closed by a sealing member 19A made of, for example, a stainless steel ball.

  In the battery element 20, a positive electrode 21 and a negative electrode 22 are stacked with a separator 23 interposed therebetween and wound in a spiral shape, and the battery element 20 is formed into a flat shape according to the shape of the outer can 11. The separator 23 is located on the outermost periphery of the battery element 20, and the positive electrode 21 is located immediately inside thereof. In FIG. 2, the laminated structure of the positive electrode 21 and the negative electrode 22 is shown in a simplified manner. Further, the number of windings of the battery element 20 is not limited to that shown in FIGS. 1 and 2 and can be arbitrarily set. A positive electrode lead 24 made of aluminum or the like is connected to an end portion (for example, an inner terminal portion) of the positive electrode 21, and a negative electrode lead 25 made of nickel or the like is connected to the negative electrode 22 (for example, an outer terminal portion). The positive electrode lead 24 is electrically connected to the terminal plate 14 by being welded to the lower end of the positive electrode pin 15, and the negative electrode lead 25 is welded and electrically connected to the outer can 11.

  FIG. 3 is a developed cross-sectional view of the positive electrode 21 shown in FIGS. 1 and 2. This positive electrode 21 is obtained by selectively providing a positive electrode active material layer 21B on both surfaces of a strip-shaped positive electrode current collector 21A. Specifically, the positive electrode active material layer 21B is present on both surfaces of the positive electrode current collector 21A, and the positive electrode coating region 21C is positioned on the winding center side and the winding outer peripheral side so as to sandwich the positive electrode coating region 21C. Both surfaces of the positive electrode current collector 21A have positive electrode exposed regions 21DS and 21DE in which the positive electrode active material layer 21B is exposed without being present. The positive electrode lead 24 is joined to the positive electrode exposed region 21DS on the winding center side. Note that the positive electrode covering region 21C and the positive electrode exposed regions 21DS, DE do not need to coincide on both surfaces of the positive electrode current collector 21A, and even if a region where the positive electrode active material layer 21B is provided on only one surface exists. Good.

  The positive electrode current collector 21A has, for example, a thickness of about 5 μm to 50 μm and is made of a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

The positive electrode active material layer 21B includes, for example, any one or more of positive electrode materials capable of occluding and releasing lithium, which is an electrode reactant, as a positive electrode active material. A conductive material and a binder such as polyvinylidene fluoride may be included. As a cathode material capable of inserting and extracting lithium, for example, lithium cobalt oxide, lithium nickel oxide or a solid solution containing them _{(Li (Ni x Co y Mn} z) O 2; x, the values of y and z 0 <x <1, 0 <y <1, 0 <z <1, x + y + z = 1), lithium manganate having a spinel structure (LiMn ₂ O ₄ ) or a solid solution thereof (Li (Mn _{2− v} Ni _v ) O ₄ ; the value of v is v <2.) and the like. As the cathode material, for example, a phosphate compound having an olivine structure such as lithium iron phosphate (LiFePO ₄₎ can be cited. This is because a high energy density can be obtained. In addition to the above, the positive electrode material includes, for example, oxides such as titanium oxide, vanadium oxide, and manganese dioxide, disulfides such as iron disulfide, titanium disulfide, and molybdenum sulfide, sulfur, polyaniline, and polythiophene. The conductive polymer may be used.

  FIG. 4 is a developed cross-sectional view of the negative electrode 22 shown in FIGS. 1 and 2. The negative electrode 22 is obtained by selectively providing a negative electrode active material layer 22B on both surfaces of a strip-shaped negative electrode current collector 22A. Specifically, the negative electrode covering region 22C where the negative electrode active material layer 22B exists on both surfaces of the negative electrode current collector 22A, and the winding center side and the winding outer peripheral side so as to sandwich the negative electrode covering region 22C, Both surfaces of the negative electrode current collector 22A have positive electrode exposed regions 22DS and 22DE that are exposed without the negative electrode active material layer 22B. The negative electrode lead 25 is joined to the negative electrode exposed region 22DE on the winding outer periphery side. Note that the negative electrode covering region 22D and the negative electrode exposed regions 22DS and DE do not need to coincide on both surfaces of the negative electrode current collector 22A, and even if a region where the negative electrode active material layer 22B is provided on only one surface exists. Good.

  The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The thickness of the negative electrode current collector 22A is, for example, 5 μm to 50 μm.

  The negative electrode active material layer 22B includes one or more negative electrode materials capable of inserting and extracting lithium as an electrode reactant as a negative electrode active material, and a binder as necessary. Or a conductive agent.

  Examples of the negative electrode material capable of inserting and extracting lithium include materials capable of inserting and extracting lithium and having at least one of a metal element and a metalloid element as a constituent element. . This is because a high energy density can be obtained. The negative electrode material may be a single element, alloy or compound of a metal element or metalloid element, or may have at least a part of one or more phases thereof. In addition, the alloy in the present invention includes an alloy containing one or more metal elements and one or more metalloid elements in addition to an alloy composed of two or more metal elements. Of course, the above-described alloy may contain a nonmetallic element. This structure includes a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or one in which two or more of them coexist.

  Examples of the metal element and metalloid element constituting the negative electrode material include metal elements and metalloid elements capable of forming an alloy with lithium. Specifically, magnesium, boron (B), aluminum, gallium (Ga), indium (In), silicon, germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd) Silver (Ag), zinc, hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), or platinum (Pt). Among these, at least one of silicon and tin is particularly preferable. This is because a high energy density can be obtained because the ability to occlude and release lithium is large.

  Examples of the negative electrode material containing at least one of silicon and tin include, for example, a simple substance, an alloy, or a compound of silicon, a simple substance, an alloy, or a compound of tin, or one or two or more phases thereof. The material which has in part is mentioned. These may be used alone or in combination of two or more.

  Examples of the silicon alloy include, as the second constituent element other than silicon, tin, nickel, copper, iron, cobalt (Co), manganese (Mn), zinc, indium, silver, titanium (Ti), germanium, and bismuth. And at least one selected from the group consisting of antimony (Sb) and chromium (Cr). As an alloy of tin, for example, as a second constituent element other than tin, among the group consisting of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing containing at least 1 sort (s) of these is mentioned.

  Examples of the silicon compound or tin compound include those containing oxygen (O) or carbon (C), and may contain the above-described second constituent element in addition to silicon or tin.

  As a specific example of a material having at least one of a metal element and a metalloid element, a material containing tin as a first constituent element and further containing second and third constituent elements is preferable. The second constituent element is cobalt, iron, magnesium, titanium, vanadium (V), chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium (Nb), molybdenum (Mo), silver, indium, cerium ( Ce), hafnium, tantalum (Ta), tungsten (W), bismuth and silicon. The third constituent element is at least one selected from the group consisting of boron, carbon, aluminum, and phosphorus (P). This is because excellent cycle characteristics can be obtained by including these second and third elements.

  Among these, tin, cobalt, and carbon are included as constituent elements, the carbon content is in the range of 9.9 mass% to 29.7 mass%, and the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co CoSnC-containing material in which)) is in the range of 30% by mass to 70% by mass is preferable. This is because in such a composition range, a high energy density is obtained and the cycle characteristics are improved.

  This CoSnC-containing material may further contain other constituent elements as necessary. As other constituent elements, for example, silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, bismuth, and the like are preferable, and two or more of them may be included. This is because energy density and cycle characteristics are further improved.

  The CoSnC-containing material has a phase containing tin, cobalt, and carbon, and this phase preferably has an amorphous structure with low crystallinity. In the CoSnC-containing material, it is preferable that at least a part of carbon that is a constituent element is bonded to a metal element or a metalloid element that is another constituent element. The decrease in cycle characteristics is thought to be due to aggregation or crystallization of tin or the like, but this aggregation or crystallization is suppressed when carbon is combined with other elements.

  As a measuring method for examining the bonding state of elements, for example, X-ray photoelectron spectroscopy (XPS) can be cited. In this XPS, in the apparatus calibrated so that the 4f orbit (Au4f) peak of gold atom is obtained at 84.0 eV, the peak of 1s orbit (C1s) of carbon appears at 284.5 eV in the case of graphite. . Moreover, if it is surface contamination carbon, it will appear at 284.8 eV. On the other hand, when the charge density of the carbon element is high, for example, when carbon is bonded to a metal element or a metalloid element, the peak of C1s appears in a region lower than 284.5 eV. That is, when the peak of the synthetic wave of C1s obtained for the CoSnC-containing material appears in a region lower than 284.5 eV, at least a part of the carbon contained in the CoSnC-containing material is a metal element or a half of other constituent elements. Combined with metal elements.

  In XPS, for example, the peak of C1s is used to correct the energy axis of the spectrum. Usually, since surface-contaminated carbon exists on the surface, the C1s peak of the surface-contaminated carbon is set to 284.8 eV, which is used as an energy standard. In XPS, the waveform of the C1s peak is obtained as a form including the surface contamination carbon peak and the carbon peak in the CoSnC-containing material. For example, by analyzing using commercially available software, the surface contamination The carbon peak and the carbon peak in the CoSnC-containing material are separated. In the waveform analysis, the position of the main peak existing on the lowest bound energy side is used as the energy reference (284.8 eV).

  Examples of the negative electrode material capable of inserting and extracting lithium include a carbon material. Examples of the carbon material include graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, or graphite having a (002) plane spacing of 0.34 nm or less. More specifically, there are pyrolytic carbons, cokes, graphites, glassy carbon fibers, fired organic polymer compounds, carbon fibers, activated carbon, carbon blacks, and the like. Among these, coke includes pitch coke, needle coke, petroleum coke, and the like, and the organic polymer compound fired body is obtained by firing and carbonizing a phenol resin or a furan resin at an appropriate temperature. . Since the carbon material has very little change in crystal structure due to insertion and extraction of lithium, for example, when used with other negative electrode materials, a high energy density can be obtained and excellent cycle characteristics can be obtained. In addition, it also functions as a conductive agent, which is preferable.

  Furthermore, examples of the negative electrode material capable of inserting and extracting lithium include metal oxides and polymer compounds capable of inserting and extracting lithium. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of the polymer compound include polyacetylene, polyaniline, and polypyrrole.

  Examples of the binder for the positive electrode 21 and the negative electrode 22 include synthetic rubbers such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene, and polymer materials such as polyvinylidene fluoride. These may be used alone or in combination of two or more. However, as shown in FIG. 1, when the positive electrode 21 and the negative electrode 22 are wound, it is preferable to use a styrene butadiene rubber or a fluorine rubber having high flexibility.

  Moreover, as a electrically conductive agent of the positive electrode 21 and the negative electrode 22, carbon materials, such as graphite, carbon black, or ketjen black, are mentioned, for example. These may be used alone or in combination of two or more. Note that the conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

  Of course, the series of negative electrode materials described above may be used as a mixture of a plurality of types. In particular, when a CoSnC-containing material and a carbon material are used in combination, energy density and cycle characteristics are further improved.

  In this secondary battery, the charge capacity of the negative electrode active material is larger than the charge capacity of the positive electrode active material by adjusting the amount between the positive electrode active material and the negative electrode active material. This prevents lithium metal from being deposited on the negative electrode 22 even during full charge.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows ions of the electrode reactant to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is made of, for example, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, a porous film made of ceramic, or the like, and these two or more kinds of porous films are laminated. It may be what was done. A polymer compound layer (not shown) is provided on the surface of the separator 23, and the separator 23 is bonded to the positive electrode 21 and the negative electrode 22 through this layer.

  The polymer compound layer includes an electrolytic solution in which an electrolyte salt is dissolved in a solvent and a polymer compound that holds the electrolytic solution. Here, the term “holds” the electrolytic solution by the polymer compound is a concept that includes not only the state in which the polymer compound is swollen in the electrolyte solution but also the state in which the electrolyte solution and the polymer compound are mixed without interaction. It is. That is, the polymer compound layer may be a so-called gel electrolyte in which the polymer compound is swollen in the electrolyte solution, or the electrolyte solution exists in the void of the rigid polymer compound without causing interaction. It may be an electrolyte. The electrolytic solution may be impregnated in the positive electrode 21, the negative electrode 22, or the separator 23.

  As the solvent contained in the electrolytic solution, various high dielectric constant solvents and low viscosity solvents can be used. For example, as a high dielectric constant solvent, in addition to ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, 4-fluoro-1,3-dioxolan-2-one (fluoroethylene carbonate), 4-chloro-1,3-dioxolane Cyclic carbonates such as 2-one (chloroethylene carbonate) and trifluoromethylethylene carbonate are preferably used. As the high dielectric constant solvent, a lactone such as γ-butyrolactone, γ-valerolactone, δ-valerolactone or ε-caprolactone, N-methylpyrrolidone, etc., instead of or in combination with the above cyclic carbonate Lactam, cyclic carbamates such as N-methyloxazolidinone, and sulfone compounds such as tetramethylene sulfone can also be used. On the other hand, as low-viscosity solvents, in addition to diethyl carbonate, chain carbonates such as dimethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, Chain carboxylic acid esters such as methyl trimethylacetate and ethyl trimethylacetate, chain amides such as N, N-dimethylacetamide, chain carbamic acid such as methyl N, N-diethylcarbamate and ethyl N, N-diethylcarbamate Esters and ethers such as 1,2-dimethoxyethane, tetrahydrofuran, tetrahydropyran and 1,3-dioxolane can be used.

  In addition, as a solvent, 1 type in the above-mentioned high-dielectric-constant solvent and low-viscosity solvent is independent, or can mix and use 2 or more types arbitrarily, However, 20-50 mass% cyclic carbonate And a low-viscosity solvent of 50 to 80% by mass are preferable, and a low-viscosity solvent including a chain carbonate having a boiling point of 130 ° C. or less is particularly preferable. By using such a solvent, the polymer compound can be swelled satisfactorily with a small amount of electrolytic solution, and it is possible to achieve both suppression of battery swelling and prevention of leakage and high ion conductivity. Here, if the content of the low-viscosity solvent occupying the electrolytic solution is too high, the dielectric constant will be lowered, and if the content of the low-viscosity solvent is too low, the viscosity will be lowered. Ionic conductivity may not be obtained, and good battery characteristics may not be obtained.

Any electrolyte salt may be used as long as it dissolves in a solvent to generate ions, and one kind may be used alone, or two or more kinds may be mixed and used. For example, if the lithium salt, lithium hexafluorophosphate (LiPF _6), lithium tetrafluoroborate (LiBF _4), lithium hexafluoroarsenate (LiAsF _6), lithium hexafluoro antimonate (LiSbF ₆₎ Inorganic lithium salts such as lithium perchlorate (LiClO ₄ ) and lithium tetrachloride aluminum oxide (LiAlCl ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bis (trifluoromethanesulfone) imide (LiN (CF ₃ SO _2
2 ), perfluoroalkanes such as lithium bis (pentafluoromethanesulfone) imide (LiN (C ₂ F ₅ SO ₂ ) ₂ ) and lithium tris (trifluoromethanesulfone) methide (LiC (CF ₃ SO ₂ ) ₃ ) Lithium salts of sulfonic acid derivatives can be used. Of these, lithium hexafluorophosphate and lithium tetrafluoroborate are preferable from the viewpoint of oxidation stability.

Incidentally, the concentration of such electrolyte salt is preferably at 0.1mol or more 3.0mol or less with respect to solvent 1 dm ^3, in particular, 0.5 mol or more 2.0mol or less with respect to solvent 1 dm ³ Is preferred. This is because higher ion conductivity can be obtained in such a range.

  The polymer compound constituting the polymer compound layer is not particularly limited as long as it retains the electrolytic solution and exhibits ionic conductivity, but the acrylonitrile copolymer is 50% or more (particularly 80% or more). Acrylonitrile polymers, aromatic polyamides, acrylonitrile / butadiene copolymers, acrylic polymers composed of homopolymers or copolymers of acrylate or methacrylate, acrylamide polymers, fluorine-containing polymers such as vinylidene fluoride, polysulfone, Examples thereof include celluloses such as polyallylsulfone and carboxymethylcellulose. In particular, a polymer having a copolymerization amount of 50% or more of acrylonitrile has a CN group in its side chain, and thus can form a gel electrolyte having a high dielectric constant and high ion conductivity. Acrylic nitriles and vinyl carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, acrylamide, methacryl sulfonic acid, hydroxyalkylene glycol (meth) are used to improve the electrolyte support for these polymers and the ionic conductivity of the electrolyte. A copolymer obtained by copolymerizing acrylate, alkoxyalkylene glycol (meth) acrylate, vinyl chloride, vinylidene chloride, vinyl acetate, various (meth) acrylates or the like at a ratio of preferably 50% or less, particularly preferably 20% or less can also be used. . Moreover, since aromatic polyamide is a high heat resistant polymer, it is suitable when high heat resistance is required.

Examples of the polymer compound constituting the polymer compound layer include a polymer having a crosslinked structure obtained by copolymerizing butadiene or the like in addition to the above. Furthermore, polymers containing vinylidene fluoride as a constituent component, that is, homopolymers, copolymers, and multi-component copolymers can also be used as the polymer compound. Specifically, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), and polyvinylidene fluoride-hexafluoropropylene-chlorotrifluoroethylene copolymer (PVdF-HEP-CTFE). ). In particular, from the viewpoint of redox stability, a fluorine-based polymer compound such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene is desirable. The polymer compound layer 26 may further contain insulating particles such as aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ) or silicon oxide (SiO ₂ ) for the purpose of improving safety. Good.

  By attaching the separator 23 to the positive electrode 21 and the negative electrode 22 through the polymer compound layer, it is possible to reduce excess electrolyte solution that is not substantially involved in the battery reaction, and the electrolyte solution is the positive electrode active material layer 21B. And efficiently supplied around the negative electrode active material layer 22B. Therefore, the secondary battery of the present embodiment exhibits excellent cycle characteristics while reducing the total amount of the electrolytic solution, and also has excellent leakage resistance. Here, the peel strength between each of the positive electrode exposed regions 21DS and 21DE of the positive electrode current collector 21A and the negative electrode exposed regions 22DS and 22E of the negative electrode current collector 22A and the separator 23 is preferably 1 mN / mm or more. / Mm or more is particularly desirable. The peel strength is determined by fixing the separator 23 on a support base and pulling the positive electrode current collector 21A or the negative electrode current collector 22A in a 180 ° direction at a speed of 10 cm / min so as to peel from the separator 23. In the meantime, it means the average value of the force required to peel them between 6 and 25 seconds after starting to pull.

  In the secondary battery, when charged, for example, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution held in the polymer compound layer on the separator 23. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted in the positive electrode 21 through the electrolytic solution.

  This secondary battery is manufactured by the following procedure, for example.

  First, the positive electrode 21 is produced. Specifically, a positive electrode active material, a binder, and a conductive agent are mixed to form a positive electrode mixture, and then dispersed in an organic solvent to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 21A using a doctor blade or a bar coater, and then dried. Finally, the cathode active material layer 21B is formed by compression molding using a roll press or the like while heating as necessary. In this case, compression molding may be repeated a plurality of times.

  Next, the negative electrode 22 is produced. Specifically, a negative electrode active material and a binder are mixed to form a negative electrode mixture, and then dispersed in an organic solvent to obtain a paste-like negative electrode mixture slurry. After that, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, dried, and then compression molded to form the negative electrode active material layer 22B. Here, when the negative electrode active material layer 22B is formed of a negative electrode active material containing silicon, tin, or lithium, the negative electrode current collector 22A and the negative electrode active material are subjected to compression molding or annealing treatment as necessary. It is desirable to improve the adhesion with the layer 22B. By doing so, peeling of the negative electrode active material layer 22B from the negative electrode current collector 22A is suppressed, and good cycle characteristics can be obtained.

  Next, the positive electrode lead 24 and the negative electrode lead 25 are attached to predetermined positions of the positive electrode current collector 21A and the negative electrode current collector 22A, respectively, by welding or the like. On the other hand, a polymer compound layer is selectively formed on one side or both sides of the separator 23. Specifically, first, a polymer solution in which a polymer compound such as polyvinylidene fluoride or carboxymethylcellulose is dissolved in a solvent such as N-methyl-2-pyrrolidone or water is applied to one or both surfaces of the separator 23. In that case, it is good not to apply | coat to the area | region used as the outer surface in the outermost periphery of the wound body 20, ie, the area | region used as the surface facing the exterior can 11. Next, the applied polymer solution is dried to remove the solvent, thereby selectively forming a polymer compound layer. After that, the positive electrode 21 and the negative electrode 22 are laminated with the separator 23 formed with the polymer compound layer interposed therebetween, wound in the winding direction R shown in FIGS. 3 and 4 and then molded. A flat wound body 20 is obtained.

  Furthermore, the outer can 11 whose inner surface is covered with the reaction suppression layer 31 is prepared. About the reaction suppression layer 31, it can form with the following method according to the kind, for example. First, in order to form the reaction suppression layer 31 made of copper or nickel, an electroless plating method may be used. In that case, it is desirable to perform a zincate treatment (zinc substitution) for forming a zinc film on the inner surface of the outer can 11 before the plating treatment. This is because the aluminum constituting the outer can 11 has a property of weakening the adhesion to a plating film such as copper or nickel by forming a strong oxide film on its surface. It is performed for the purpose of improving.

  The reaction suppression layer 31 is formed by aluminum oxide containing a fluororesin as follows. First, an aluminum oxide layer is formed on the inner surface of the outer can 11 by energizing the outer can 11 as an anode in an aqueous sulfuric acid solution (alumite treatment). Next, the outer can 11 on which the aluminum oxide layer is formed is subjected to heat treatment while being immersed in an aqueous polytetrafluoroethylene (PTFE) dispersion (dispersion), thereby forming a reaction suppression layer 31 made of fluororesin-containing aluminum oxide. To do.

  In addition, in order to form the reaction suppression layer 31 made of polyimide, the inner surface of the outer can 11 is spray-coated with a polyamic acid dispersed in an organic solvent (N-methyl-2-pyrrolidone or the like), and heat treatment is performed in an argon atmosphere. Should be done. The same applies to the reaction suppression layer 31 made of other types of resins.

  Finally, the secondary battery is assembled. Specifically, after the battery element 20 is accommodated in the outer can 11 having the reaction suppression layer 31, the insulating plate 12 is disposed on the battery element 20. Subsequently, the positive electrode lead 24 is connected to the positive electrode pin 15 and the negative electrode lead 25 is connected to the outer can 11 by welding or the like, and then the battery lid 13 is fixed to the open end of the outer can 11 by laser welding or the like. Finally, after injecting the electrolyte into the outer can 11 from the injection hole 19 and impregnating the separator 23, the injection hole 19 is closed with a sealing member 19A. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  In the secondary battery, when charged, for example, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 via the electrolytic solution held in the separator 23. On the other hand, when discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted in the positive electrode 21 via the electrolytic solution held in the separator 23.

  According to this secondary battery, since the reaction suppression layer 31 is provided on the inner surface of the outer can 11, alloying of lithium as the battery reactant and aluminum constituting the outer can 11 connected to the negative electrode 22 is performed. The reaction is suppressed. As a result, the cycle characteristics can be improved while reducing the weight. In the past, in order to avoid the problem of erosion of the outer can itself during use, it was necessary to short-circuit the outer can using aluminum with the positive electrode, but according to the secondary battery of the present embodiment, Such constraints are eliminated, and the degree of freedom in design can be expanded. Furthermore, since the positive electrode current collector 21A is disposed so as to face the inner surface of the outer can 11, when the reaction suppression layer 31 has conductivity, the safety of the battery at the time of abnormality such as breakage is further improved. Can do. That is, since the outer can 11 is short-circuited with the negative electrode 22 and the positive electrode 21 with the positive electrode current collector 21A exposed through the separator 23 is disposed immediately inside the outer can 11, the negative electrode terminal is used at the time of abnormality such as battery collapse As the outer can 11 is short-circuited with the positive electrode 21, the battery reaction quickly converges. As a result, excessive heat generation and ignition of the battery element 20 can be prevented.

  Next, the second and third batteries will be described. Components that are the same as those of the first battery are denoted by the same reference numerals, and description thereof is omitted.

(Second battery)
The second battery has the same configuration, operation, and effect as the first battery except that the configuration of the negative electrode 22 is different, and is manufactured by the same procedure.

  The negative electrode 22 has a negative electrode active material layer 22B provided on both surfaces of a negative electrode current collector 22A, as in the first battery. The negative electrode active material layer 22B contains, for example, a negative electrode active material containing silicon or tin as a constituent element. Specifically, for example, it contains a silicon simple substance, an alloy or a compound, or a tin simple substance, an alloy or a compound, and may contain two or more of them.

  This negative electrode active material layer 22B is formed by arbitrarily using a vapor phase method, a liquid phase method, a thermal spraying method or a firing method, or two or more of these methods. The electrical conductor 22A is preferably alloyed at least at a part of the interface. Specifically, the constituent elements of the negative electrode current collector 22A diffuse into the negative electrode active material layer 22B at the interface, the constituent elements of the negative electrode active material layer 22B diffuse into the negative electrode current collector 22A, or the constituent elements thereof It is preferable that they diffuse to each other. This is because breakage due to expansion and contraction of the negative electrode active material layer 22B due to charging / discharging can be suppressed, and electronic conductivity between the negative electrode active material layer 22B and the negative electrode current collector 22A can be improved. .

  As the vapor phase method, for example, physical deposition method or chemical deposition method, specifically, vacuum vapor deposition method, sputtering method, ion plating method, laser ablation method, thermal chemical vapor deposition (CVD; Chemical Vapor Deposition) Or plasma chemical vapor deposition. As the liquid phase method, a known method such as electroplating or electroless plating can be used. The firing method is, for example, a method in which a particulate negative electrode active material is mixed with a binder and dispersed in a solvent and then heat treated at a temperature higher than the melting point of the binder. A known method can also be used for the firing method, for example, an atmospheric firing method, a reactive firing method, or a hot press firing method.

  The second battery is formed once because the adhesion between the negative electrode current collector 22A and the negative electrode active material layer 22B is stronger than when formed by a coating method as in the first battery. It is extremely difficult to selectively remove the negative electrode active material layer 22B from above the negative electrode current collector 22A. In addition, when the negative electrode active material layer 22B is selectively formed by performing high-precision masking so as not to be formed in an unnecessary region in advance, the number of processes and the processing time are increased, which causes a decrease in productivity. . Therefore, instead of short-circuiting the outer can 11 with the positive electrode 21 and disposing the negative electrode 22 with the negative electrode current collector 22A exposed via the separator 23 immediately inside the outer can 11, as shown in FIG. It is desirable in manufacturing to secure the safety of the battery by arranging the positive electrode 21 with the positive electrode current collector 21 </ b> A exposed through the separator 23 immediately inside the short circuit with the negative electrode 22. When the negative electrode lead 25 is attached to one end of the negative electrode current collector 22A, the negative electrode lead 25 is strongly pressed (caulked) from above the negative electrode active material layer 22B without removing the negative electrode active material layer 22B. What is necessary is just to carry out press-contact joining with 22 A of negative electrode collectors.

  According to this secondary battery, as with the first battery, it is possible to improve the cycle characteristics while achieving weight reduction and to ensure high safety.

(Third battery)
The third battery is a secondary battery (so-called lithium metal secondary battery) in which the capacity of the negative electrode 22 is represented by a capacity component based on precipitation and dissolution of lithium. This secondary battery has the same configuration as the first or second battery except that the negative electrode active material layer 22B is made of metallic lithium.

  This secondary battery can obtain a higher energy density by using metallic lithium as a negative electrode active material.

  For example, a metal lithium foil is used as the negative electrode active material layer 22B, and this is bonded to a negative electrode current collector 22A such as a copper foil. Alternatively, the negative electrode active material layer 22B made of metallic lithium can be formed on the negative electrode current collector 22A using a vapor phase method, a liquid phase method, or the like.

  In this secondary battery, when charged, lithium ions are released from the positive electrode 21 and deposited as metallic lithium on the surface of the negative electrode current collector 22A through the electrolytic solution. On the other hand, when discharging is performed, metallic lithium is eluted as lithium ions from the negative electrode active material layer 22B and is occluded in the positive electrode 21 through the electrolytic solution.

  Note that the negative electrode active material layer 22B may be provided at the assembly stage, but may be configured by metallic lithium deposited during charging without being provided at the time of assembly. Further, by using the metal lithium foil itself as the negative electrode current collector 22A together with the negative electrode active material layer 22B, the copper foil as the negative electrode current collector 22A may be omitted.

  According to this secondary battery, when the capacity of the negative electrode 22 is expressed by a capacity component based on the precipitation and dissolution of lithium, the cycle characteristics are improved while reducing the weight as in the first and second batteries. And high safety can be ensured.

  Next, specific examples of the present invention will be described in detail.

(Examples 1-1 to 1-10)
As this example, the square secondary battery shown in FIGS. 1 and 2 was produced. However, the negative electrode 22 has four types A to D described below, and the reaction suppression layer 31 provided on the inner surface of the outer can 11 has four types I to IV described below. Further, the separator 23 was directly impregnated with the electrolytic solution without providing the separator 23 with a polymer compound layer.

First, the positive electrode 21 was produced. Specifically, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a molar ratio of Li ₂ CO ₃ : CoCO ₃ = 0.5: 1, and 5 ° C. at 900 ° C. in the air. After firing for a time, lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material was obtained. Next, 91 parts by mass of this lithium / cobalt composite oxide, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. Subsequently, the positive electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, which is selectively applied to both surfaces of a positive electrode current collector 21A made of an aluminum foil having a thickness of 12 μm and dried. Then, the cathode active material layer 21B was formed by compression molding with a roll press machine, and the cathode 21 was produced. At this time, the positive electrode exposed regions 21DS and 21DE (FIG. 3) are provided on the winding center side and the winding outer peripheral side of the positive electrode 21, respectively. Subsequently, an aluminum positive electrode lead 24 was attached to the positive electrode current collector 21A in the positive electrode exposed region 21DS.

  Next, the negative electrodes 22 of types A to D were produced as follows.

<Type A>
First, a 99% pure silicon powder having an average particle diameter of 1 μm, a flaky artificial graphite powder having an average particle diameter of 6 μm, and polyamic acid are mixed at a mass ratio of 80:10:10 to form a negative electrode mixture. Adjusted. Subsequently, the negative electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry, which was uniformly applied to both surfaces of the negative electrode current collector 22A made of an electrolytic copper foil and dried. Here, as the electrolytic copper foil, one having a thickness of 15 μm and a surface roughness of Ra value of 0.4 μm was used. After drying, a negative electrode active material layer 22B formed by mixing silicon, graphite, and polyimide was formed on the negative electrode current collector 22A by performing heat treatment in an argon atmosphere at a temperature of 350 ° C. for 12 hours. . Further, a nickel negative electrode lead 25 was attached to one end of the negative electrode current collector 22A. At this time, the negative electrode lead 25 was pressed and joined to the negative electrode current collector 22A by strongly pressing (caulking) the negative electrode lead 25 from above the negative electrode active material layer 22B.

<Type B>
A thin film of silicon having a thickness of 7 μm is deposited on both surfaces of the negative electrode current collector 21A made of electrolytic copper foil by using an electron beam deposition method, and then heat treatment is performed at a temperature of 300 ° C. for 6 hours in an argon atmosphere. By performing, the negative electrode active material layer 22B was formed. Here, as the electrolytic copper foil, one having a thickness of 15 μm and a surface roughness Ra value of 0.3 μm was used. Further, in the same manner as in Type A, a negative electrode lead 25 made of nickel was attached to one end of the negative electrode current collector 21A.

<Type C>
A tin plating film having a thickness of 6 μm is formed on both surfaces of the negative electrode current collector 21A made of an electrolytic copper foil using an electrolytic plating method, and a thickness of 2 μm is formed on the plating film using an electron beam evaporation method. A thin film of cobalt (Co) was deposited. After that, the negative electrode active material layer 22B was formed by performing heat treatment for 24 hours at a temperature of 200 ° C. in an argon atmosphere. Here, as the electrolytic copper foil, one having a thickness of 15 μm and a surface roughness Ra value of 0.3 μm was used. Further, in the same manner as in Type A, a negative electrode lead 25 made of nickel was attached to one end of the negative electrode current collector 21A.

<Type D>
Spherical artificial graphite particles having an average particle size of 25 μm, graphitized vapor-grown carbon fiber, and polyvinylidene fluoride as a binder were mixed at a mass ratio of 90: 3: 7 to prepare a negative electrode mixture. . Subsequently, the negative electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry, which was selectively applied to both surfaces of the negative electrode current collector 22A made of electrolytic copper foil and dried. . Here, as the electrolytic copper foil, one having a thickness of 15 μm and a surface roughness of Ra of 0.1 μm was used. After drying, the negative electrode active material layer 22B was formed by press molding with a roll press. After that, a nickel negative electrode lead 25 was attached to one end of the negative electrode current collector 22A not covered with the negative electrode active material layer 22B.

  After preparing the positive electrode 21 and the negative electrode 22, a rectangular outer can 11 (0.3 mm thickness) made of an aluminum alloy is prepared, and reaction suppression layers 31 of type I to IV are respectively formed on the inner surface thereof as follows. did.

<Type I>
First, the outer can 11 was degreased and washed with trichlorethylene and then washed in a nitric acid bath. Subsequently, the zincate process which forms a zinc membrane | film | coat on the inner surface of the armored can 11 was performed using the commercially available zinc alloy substitution agent, and after making it immersed once in a nitric acid bath, the same zincate process was performed again. After that, it was immersed in a mixed solution of nickel chloride, sodium hypophosphite and sodium oxyacetate maintained at 85 ° C., and a reaction suppressing layer 31 made of a nickel plating film having a thickness of 20 μm was formed by an electroless plating method. .

<Type II>
First, an aluminum oxide layer was formed on the inner surface of the outer can 11 by energizing the outer can 11 as an anode in a sulfuric acid aqueous solution (alumite treatment). Subsequently, the outer can 11 on which the aluminum oxide layer is formed is subjected to heat treatment while being immersed in an aqueous polytetrafluoroethylene dispersion having an average particle diameter of 0.3 μm, whereby the reaction suppression layer 31 made of fluororesin-containing aluminum oxide is performed. Formed. The heat treatment was performed in an argon atmosphere at a temperature of 350 ° C. for 12 hours. In addition, the thickness of the reaction suppression layer 31 here was 30 micrometers.

<Type III>
After the polyamic acid dispersed in N-methyl-2-pyrrolidone is spray-coated on the inner surface of the outer can 11, heat treatment is performed in an argon atmosphere, and the operation of spray coating and heat treatment is repeated again, so that the polyimide can be removed. The reaction suppression layer 31 was formed. The first heat treatment was performed at a temperature of 300 ° C. for 3 hours, and the second heat treatment was performed at a temperature of 450 ° C. for 12 hours. Here, the thickness of the reaction suppression layer 31 was 20 μm.

<Type IV>
First, an aluminum oxide layer was formed on the inner surface of the outer can 11 by energizing the outer can 11 as an anode in a sulfuric acid aqueous solution (alumite treatment). Next, after spraying a xylene solution containing 10% by weight of perhydropolysilazane (PHPS) on the inner surface of the outer can 11 on which the aluminum oxide layer is formed, the silicon dioxide layer is obtained by reacting moisture in the air with perhydropolysilazane. The reaction suppression layer 31 having a laminated structure of an aluminum oxide layer and a silicon dioxide layer was obtained. Here, the thickness of the reaction suppression layer 31 was 40 μm.

  After forming the reaction suppression layer 31, a separator 23 made of a microporous polyethylene film having a thickness of 16 μm is prepared. After the positive electrode 21 and the negative electrode 22 are stacked with the separator 23 interposed therebetween, a stacked body is formed. The battery element 20 was obtained by winding the battery in a spiral shape and molding it into a flat shape. At this time, the positive electrode exposed region 21DE of the positive electrode current collector 21A was positioned on the outer peripheral side of the battery element 20 with respect to the negative electrode 22.

Next, after the battery element 20 is accommodated in the outer can 11, the insulating plate 12 is disposed on the battery element 20, the negative electrode lead 25 is welded to the outer can 11, and the positive electrode lead 24 is connected to the positive electrode pin 15. The battery lid 13 was fixed to the open end of the outer can 11 by laser welding. After that, an electrolytic solution was injected into the outer can 11 from the injection hole 19. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ as an electrolyte salt at a concentration of 1 mol / dm ³ in a solvent in which 30% by volume of ethylene carbonate and 70% by volume of diethyl carbonate were mixed was used. Finally, the injection hole 19 was closed with a sealing member 19A to obtain a square secondary battery.

  Each type of the negative electrode 22 and the reaction suppression layer 31 in each example is as shown in Table 1 (described later).

  As Comparative Examples 1-1 to 1-8 with respect to Examples 1-1 to 1-10, except that the reaction suppression layer was not formed, the battery was manufactured in the same manner as in Examples 1-1 to 1-8. Produced. However, Comparative Examples 1-5 to 1-8 were prepared such that the outer can 11 was short-circuited with the positive electrode, and the negative electrode 22 was positioned on the outermost periphery of the battery element 20. The type of the negative electrode 22 in each comparative example is as shown in Table 1.

About the obtained secondary battery of each Example and each comparative example, constant current charging was performed until the battery voltage reached 4.2 V while maintaining a current density of ² mA / cm ² , and then a constant voltage of 4.2 V Was stopped at the time when the current density reached 0.2 mA / cm ² . Subsequently, constant current discharge was performed until the battery voltage reached 2.5 V at a current density of ² mA / cm ² , and the initial charge / discharge efficiency (initial discharge capacity / initial charge capacity) was determined. The results are shown in Table 1.

  As shown in Table 1, in Examples 1-1 to 1-10, by forming the reaction suppression layer 31 on the inner surface of the outer can 11, from Comparative Examples 1-1 to 1-4 in which this was not provided The initial charge / discharge efficiency was also greatly improved. In other words, in Examples 1-1 to 1-10, Comparative Examples 1-5 to 1-8 in which the outer can 11 itself was short-circuited with the positive electrode without causing a battery reaction as the negative electrode terminal. Almost the same performance could be maintained.

(Examples 2-1 to 2-3)
Next, the nail penetration test was performed and the change in the state was observed to examine the safety when the battery was damaged. The results are shown in Table 2.

  In this nail penetration test, a constant current / constant voltage charge is performed up to 4.2V with a current corresponding to a design rated capacity of 1C at room temperature, and then the nail is inserted so as to penetrate almost the center of the outer can 11. Φ2.5 mm) was stabbed, and after 30 seconds, the surface temperature of the outer can 11 was measured and the appearance was observed. Here, the battery state after the test was classified and evaluated in three stages (level 0 to level 2) based on changes in appearance and surface temperature. Level 0 represents a state where the surface temperature is 50 ° C. or less, no smoke or ignition, level 1 represents a state where the surface temperature is 90 ° C. or less and no smoke or ignition, and level 2 represents a state where the surface temperature is 90 ° C. or more and smoke or ignition occurs. Among these, levels 0 and 1 at which no smoke or ignition occurred are acceptable levels as safety when the battery is broken.

  In the batteries of Examples 2-1 to 2-3, the outer can 11 is short-circuited with the negative electrode 22, the configuration of the negative electrode 22 is the above type B, and the reaction suppression layer 31 of the above type I is provided on the inner surface of the outer can 11. Formed. Further, in Example 2-1, the exposed portion of the negative electrode current collector 22A and the exposed portion of the positive electrode current collector 21A were not provided. In Example 2-2, as illustrated in FIG. 1, the exposed portion of the positive electrode current collector 21 </ b> A is provided at the winding outer peripheral side end portion of the battery element 20 without providing the exposed portion of the negative electrode current collector 22 </ b> A. . In Example 2-3, an exposed portion was provided for both the negative electrode current collector 22A and the positive electrode current collector 21A at the winding outer peripheral side end of the battery element 20.

  As Comparative Examples 2-1 to 2-2 and 2-4 with respect to Examples 2-1 to 2-3, except that the outer can 11 was short-circuited with the positive electrode and the reaction suppression layer was not formed. Batteries were produced in the same manner as in 2-1 to 2-3. Furthermore, as Comparative Example 2-3, except that the exposed portion of the negative electrode current collector 22A was provided at the winding outer peripheral side end portion of the battery element 20 without providing the exposed portion of the positive electrode current collector 21A, Otherwise, a battery was fabricated in the same manner as in Comparative Example 2-4. In Comparative Examples 2-1 to 2-4, the battery element 20 was fabricated such that the outermost periphery of the battery element 20 was the negative electrode 22, contrary to Examples 2-1 to 2-3.

  As shown in Table 2, in this example, the level was 0 or 1, and both were acceptable levels. In particular, in Examples 2-2 and 2-3 in which the exposed portion of the positive electrode current collector 21A was provided and opposed to the inner surface of the outer can 11 serving as the negative electrode terminal, the level was 0, and a better result was obtained. . Moreover, it was found from comparison between Example 2-2 and Example 2-3 that sufficiently high safety can be ensured without intentionally providing the exposed portion of the anode current collector 22A. On the other hand, when the outer can 11 is short-circuited with the positive electrode 21, the level 2 is obtained unless the exposed portion of the negative electrode current collector 22A is provided (Comparative Examples 2-1 and 2-2). In order to ensure, it is necessary to provide the exposed part of 22 A of negative electrode collectors like Comparative example 2-3 and 2-4. That is, the outer can 11 as the negative electrode terminal is made to function as in this embodiment, so that the negative electrode active material layer 22B is removed or a complicated operation of selectively forming the negative electrode active material layer 22B is sufficient. It was found that ensuring safety was feasible.

  The present invention has been described with reference to the embodiments and examples. However, the present invention is not limited to the embodiments described in the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the case where a gel electrolyte in which an electrolytic solution is held in a polymer compound is used and the case where a separator is impregnated with an electrolytic solution are used. However, other types of electrolytes are used. May be used. Other electrolytes include, for example, electrolyte solutions that are not retained in a polymer compound, a mixture of an ion conductive ceramic compound such as ion conductive ceramics, ion conductive glass, or ionic crystals, and an electrolyte solution, and others. Or a mixture of these inorganic compounds and a gel electrolyte.

  In the above-described embodiments and examples, the battery of the present invention is a lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component based on insertion and extraction of lithium, or lithium metal is used for the negative electrode active material. The lithium metal secondary battery in which the capacity of the negative electrode is represented by a capacity component based on the precipitation and dissolution of lithium has been described, but is not necessarily limited thereto. In the battery of the present invention, the negative electrode material capable of occluding and releasing lithium has a smaller charge capacity than the positive electrode, so that the capacity of the negative electrode is determined based on the storage and release of lithium and the deposition of lithium. Further, the present invention can be similarly applied to a secondary battery that includes a capacity component based on dissolution and is expressed by the sum of the capacity components.

  In the above-described embodiment or example, both surfaces of the positive electrode current collector are exposed without providing the positive electrode active material layer in the outermost peripheral portion of the positive electrode. However, the present invention is not limited to this. For example, as in the first modification of FIG. 5, the surface of the positive electrode current collector 21 </ b> A at the outermost peripheral portion that faces the outermost peripheral portion of the negative electrode 22 located inside thereof corresponds to the negative electrode active material layer 22 </ b> B. It is desirable to provide the positive electrode active material layer 21B at the position. By doing so, the battery capacity can be further improved. Further, when both surfaces of the positive electrode current collector at the outermost peripheral part are exposed, the negative electrode current collector facing the outermost peripheral part of the positive electrode current collector 21A, for example, as in the second modification shown in FIG. The body 22A may be exposed. By doing so, in an abnormal state, in addition to the outer can 11 and the outermost peripheral surface of the positive electrode current collector 21A being in contact, the outermost peripheral portions of the positive electrode current collector 21A and the negative electrode current collector 22A are brought into contact with each other. Therefore, the battery reaction can be converged more quickly, which is more advantageous in terms of safety.

  In the above-described embodiments or examples, the battery structure of the battery of the present invention has been described by taking a square shape as an example. However, the battery of the present invention can be a cylindrical shape, a laminate film type, a coin type, or a button type. The present invention can be similarly applied to secondary batteries having other battery structures. Furthermore, in the above-described embodiment or example, the winding type battery element is described as an example, but the present invention can be similarly applied to a secondary battery using a stacked type battery element. Further, the battery of the present invention is not limited to the secondary battery, but can be similarly applied to other types of batteries such as a primary battery.

It is sectional drawing showing the battery as one embodiment in this invention. It is sectional drawing showing the structure along the II-II line of the battery shown in FIG. It is sectional drawing which expand | deployed the positive electrode shown in FIG. It is sectional drawing which expand | deployed the negative electrode shown in FIG. It is sectional drawing showing the structure of the 1st modification of the battery shown in FIG. It is sectional drawing showing the structure of the 2nd modification of the battery shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Exterior can, 12 ... Insulating plate, 13 ... Battery cover, 14 ... Terminal board, 15 ... Positive electrode pin, 16 ... Insulating case, 17 ... Gasket, 18 ... Cleavage valve, 19 ... Injection hole, 19A ... Sealing member, DESCRIPTION OF SYMBOLS 20 ... Battery element, 21 ... Positive electrode, 21A ... Positive electrode collector, 21B ... Positive electrode active material layer, 22 ... Negative electrode, 22A ... Negative electrode collector, 22B ... Negative electrode active material layer, 23 ... Separator, 24 ... Positive electrode lead, 25 ... Negative electrode lead, 31 ... Reaction suppression layer.

Claims (9)

A battery element having a positive electrode including a material capable of inserting and extracting lithium (Li) and a negative electrode including a material capable of inserting and extracting lithium;
An outer can that houses the battery element;
The outer can is made of a metal material containing aluminum (Al), is short-circuited to the negative electrode, and has a reaction suppression layer that suppresses a reaction between aluminum and lithium on an inner surface thereof. battery. The battery according to claim 1, wherein the reaction suppression layer includes a metal that does not form an alloy with lithium. The battery according to claim 2, wherein the reaction suppression layer includes at least one of copper (Cu) and nickel (Ni). The battery according to claim 1, wherein the reaction suppression layer includes at least one of polyamideimide, polyimide, fluorine-containing resin, and epoxy resin.   The battery according to claim 1, wherein the reaction suppression layer includes a metal oxide. The positive electrode is one in which a positive electrode active material layer is provided so as to cover at least a part of the surface of the positive electrode current collector other than the facing surface facing the inner surface of the outer can
The battery according to claim 1, wherein the facing surface of the positive electrode current collector is separated from an inner surface of the outer can by a separator. The battery element is a wound body having a laminated structure in which the positive electrode and the negative electrode are laminated via a separator,
The outermost peripheral part of the positive electrode is located between the outermost peripheral part of the negative electrode and the outer can,
The negative electrode is provided with a negative electrode active material layer so as to cover at least a part of a surface other than the outermost peripheral surface of the negative electrode current collector,
The positive electrode is provided with a positive electrode active material layer so as to cover at least a part of a surface other than both surfaces of the outermost peripheral portion of the positive electrode current collector,
The battery according to claim 1, wherein an inner surface of the outer can and an outermost peripheral surface of the positive electrode current collector are separated by the separator. The negative electrode is obtained by providing a negative electrode active material layer containing at least one of silicon (Si) and tin (Sn) or metallic lithium on a negative electrode current collector. The battery described. The battery according to claim 8, wherein the negative electrode current collector and the negative electrode active material are alloyed in at least a part of an interface.

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