Nonaqueous electrolyte battery

Abstract

Provided is a nonaqueous electrolyte battery having excellent high-temperature storage characteristics and low-temperature load characteristics. This nonaqueous electrolyte battery is characterized by having a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte solution, the negative electrode having a lithium layer having a lithium-aluminum alloy layer formed on the surface thereof, and further having a carbon layer on the lithium-aluminum alloy layer, the carbon layer containing carbon black.

Description

[0001] This application is a divisional application of the invention application with the application number 2020800419061, the application date of June 5, 2020, and the invention title of "Non-aqueous electrolyte battery and method for manufacturing the same". Technical Field

[0002] The present invention relates to a non-aqueous electrolyte battery having excellent high-temperature storage characteristics and load characteristics at low temperatures, and a method for manufacturing the same. Background Art

[0003] Currently, non-aqueous electrolyte batteries such as primary lithium batteries and lithium-ion secondary batteries having non-aqueous electrolytes are applied to various fields such as power sources for portable devices and uses exposed to high temperatures and large vibrations such as power sources for pressure sensors inside tires. In order to cope with the expansion of such uses, attempts have been made to improve various characteristics.

[0004] However, when storing the battery at high temperatures, reactions between the electrolyte and the electrodes occur, causing problems such as swelling of the battery. Therefore, for uses where the battery is used in a high-temperature environment, etc., countermeasures for suppressing the reaction between the electrolyte and the electrodes are required.

[0005] In this regard, as an additive that can suppress the reaction with the electrolyte and suppress the swelling of the battery during high-temperature storage by forming a film on the surface of the positive electrode or the negative electrode, sulfur-based compounds such as propane sultone are known (Patent Document 1).

[0006] In addition, Patent Document 2 discloses that by using a non-aqueous electrolyte containing lithium bis(oxalato)borate [LiB(C 2 O 4 ) 2 and LiBF 4 in a range of 2:8 to 5:5 in terms of molar ratio, it is possible to prevent an increase in internal resistance caused by moisture released from the positive electrode active material into the electrolyte at high temperatures and an increase in internal pressure caused by decomposition of the electrolyte, and a battery having excellent characteristics at both low and high temperatures can be constructed.

[0007] However, when additives such as propane sultone and lithium bis(oxalato)borate are contained in the electrolyte in order to produce sufficient effects, for example, the film formed on the surface of the negative electrode hinders the discharge reaction and increases the internal resistance of the battery, so that problems such as a decrease in discharge characteristics after high-temperature storage are likely to occur.

[0008] On the other hand, in Patent Documents 3 and 4, as a method for replacing the above additives, a method of forming a carbon-containing layer on the surface of the negative electrode is proposed.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-47413

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2006-269173

[0013] Patent Document 3: Japanese Patent Application Laid-Open No. 2010-257828

[0014] Patent Document 4: Japanese Patent Application Laid-Open No. 2011-091034 Summary of the Invention

[0015] Problems to be Solved by the Invention

[0016] However, for non-aqueous electrolyte batteries, battery characteristics that can be used not only at high temperatures but also in a wide temperature environment including low temperatures are required. In order to balance the storage characteristics at high temperatures and the load characteristics at low temperatures, further research is needed.

[0017] The present invention has been made in view of the above circumstances, and an object thereof is to provide a non-aqueous electrolyte battery having excellent high-temperature storage characteristics and load characteristics at low temperatures, and a method for manufacturing the same.

[0018] Means for Solving the Problems

[0019] The non-aqueous electrolyte battery of the present invention is characterized in that it has a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, the negative electrode has a lithium layer on the surface of which a lithium-aluminum alloy layer is formed, and a carbon layer is further provided on the lithium-aluminum alloy layer.

[0020] The non-aqueous electrolyte battery of the present invention is manufactured by a manufacturing method (manufacturing method of the non-aqueous electrolyte battery of the present invention) having the following steps: a step of laminating an aluminum layer on the surface of the lithium layer; a step of further forming a carbon layer on the surface of the aluminum layer; and a step of reacting the lithium layer with the aluminum layer to form a lithium-aluminum alloy layer on the surface of the lithium layer.

[0021] Advantages of the Invention

[0022] According to the present invention, it is possible to provide a non-aqueous electrolyte battery having excellent high-temperature storage characteristics and load characteristics at low temperatures, and a method for manufacturing the same. Brief Description of the Drawings

[0023] Figure 1 is a longitudinal sectional view schematically showing an example of the non-aqueous electrolyte battery of the present invention.

[0024] Figure 2 is a graph showing the measurement results of the discharge voltage of the non-aqueous electrolyte battery of the example. Detailed Description of the Invention

[0025] The non-aqueous electrolyte battery of the present invention includes a negative electrode having a lithium layer with a lithium-aluminum alloy layer formed on its surface, and a carbon layer further formed on the lithium-aluminum alloy layer. The reason is not clear yet, but by using the above negative electrode, it is possible to suppress the deterioration of battery characteristics during high-temperature storage and improve the load characteristics of the non-aqueous electrolyte battery at low temperatures after high-temperature storage (for example, the load characteristics at a low temperature of about -40°C).

[0026] The lithium-aluminum alloy layer of the negative electrode can be formed, for example, as follows: an aluminum layer composed of an aluminum foil or an aluminum alloy foil is provided on the surface of a lithium layer composed of a lithium foil or a lithium alloy foil to form a laminate, and a carbon layer is further formed on the surface of the aluminum layer (the surface opposite to the lithium layer) of the laminate to obtain a laminate for the negative electrode. The laminate for the negative electrode is brought into contact with the non-aqueous electrolyte to cause the lithium layer and the aluminum layer to react.

[0027] When the laminate for the negative electrode is brought into contact with the non-aqueous electrolyte to form a lithium-aluminum alloy layer, it can also be carried out before battery assembly. In this case, the negative electrode obtained by changing the aluminum layer of the laminate for the negative electrode into a lithium-aluminum alloy layer is used for the assembly of the non-aqueous electrolyte battery. On the other hand, the laminate for the negative electrode can also be used instead of the negative electrode to assemble the battery, and when assembling, the laminate for the negative electrode is brought into contact with the non-aqueous electrolyte, and a lithium-aluminum alloy layer is formed in the same manner as above to obtain a negative electrode. In this case, the negative electrode manufacturing process before battery assembly can be simplified, so it is preferable from the aspect of further improving the battery production rate.

[0028] Examples of the lithium foil or lithium alloy foil used to form the lithium layer include a foil composed of Li (and inevitable impurities) (lithium foil); a foil composed of a Li alloy containing Fe, Ni, Co, Mn, Cr, V, Ti, Zr, Nb, Mo, etc. as alloy components in a total amount of 40% by mass or less, preferably 10% by mass or less, and more preferably 5% by mass or less, with the balance being Li and inevitable impurities (lithium alloy foil), etc.

[0029] The thickness of the lithium foil or lithium alloy foil used to form the lithium layer is preferably 0.1 to 1.5 mm.

[0030] Examples of the aluminum foil or aluminum alloy foil used to form the aluminum layer include a foil composed of Al (and inevitable impurities) (aluminum foil); a foil composed of an Al alloy containing Fe, Ni, Co, Mn, Cr, V, Ti, Zr, Nb, Mo, etc. as alloy components, with the balance being Al and inevitable impurities (the content of the above alloy components is, for example, 50% by mass or less, preferably 10% by mass or less, and more preferably 5% by mass or less) (aluminum alloy foil), etc.

[0031] In order to clarify the effects of the present invention brought about by the formation of the lithium-aluminum alloy layer, the thickness of the aluminum foil and aluminum alloy foil used to form the aluminum layer is preferably 1 μm or more, more preferably 3 μm or more, and particularly preferably 5 μm or more.

[0032] On the other hand, if the proportion of the lithium-aluminum alloy layer relative to the lithium layer is too large, the capacity of the negative electrode will be reduced. In addition, due to the volume expansion during the alloying of the aluminum layer and lithium, cracks will occur in the aluminum layer (aluminum alloy layer). However, if the thickness of the aluminum layer becomes thicker, the above-mentioned cracks will occur deep inside the negative electrode, and there is a risk of part of the aluminum alloy layer peeling off when subjected to large vibrations. Therefore, in order to make the thickness of the formed lithium-aluminum alloy layer below a certain value, the thickness of the aluminum foil and aluminum alloy foil is preferably set to 20 μm or less, and more preferably 15 μm or less.

[0033] It should be noted that the aluminum alloy layer may not be formed on the entire surface of the lithium layer, or the aluminum alloy layer may be formed on a part of the surface of the lithium layer. However, the larger the area ratio of the formed aluminum alloy layer, the easier it is to produce the effects of the present invention. Therefore, the area ratio of the aluminum alloy layer formed on the surface of the lithium layer is preferably 40% or more, more preferably 70% or more, and most preferably 100%, that is, the aluminum alloy layer is formed on the entire surface of the lithium layer.

[0034] The aluminum layer can be formed on one or both sides of the lithium layer according to the form of the battery. For example, in a battery with a positive electrode arranged on both sides of the lithium layer of the negative electrode, the aluminum layer can be provided on both sides of the lithium layer to form a lithium-aluminum alloy layer.

[0035] The laminate having a lithium layer and an aluminum layer can be formed by laminating and pressing a lithium foil or lithium alloy foil used to form the lithium layer and an aluminum foil or aluminum alloy foil used to form the aluminum layer.

[0036] The carbon layer of the negative electrode can be composed only of carbon (its particles), or can contain carbon and a binder at the same time.

[0037] Examples of the carbon constituting the carbon layer include carbon blacks such as furnace black, channel black, acetylene black, and thermal cracking carbon black; natural graphite (such as flake graphite) and artificial graphite; etc. One of them can be used alone, or two or more can be used in combination.

[0038] In addition, examples of the binder that can be used in the carbon layer include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyvinylpyrrolidone, etc. In particular, a compound having a five-membered ring lactam structure such as polyvinylpyrrolidone can disperse fine carbon materials such as carbon black well in a dissolved state in a solvent, so it is preferably used.

[0039] The content of the binder in the carbon layer is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less.

[0040] From the viewpoint of ensuring the above effects well by forming the carbon layer, the weight per unit area of the carbon layer in the negative electrode is preferably 0.15 mg / cm 2 or more, more preferably 0.3 mg / cm 2 or more, and particularly preferably 0.5 mg / cm 2 or more. However, even if the carbon layer is thickened, the effect will saturate, and in addition, the entire negative electrode becomes thicker. For example, the amount of the positive electrode active material that can be introduced into the battery becomes smaller, which may also cause a risk of reducing the battery capacity. Therefore, for example, from the viewpoint of increasing the battery capacity, the weight per unit area of the carbon layer in the negative electrode is preferably 1.5 mg / cm 2 or less, more preferably 1.0 mg / cm 2 or less.

[0041] It should be noted that the carbon layer may not be formed on the entire surface of the aluminum alloy layer, and the carbon layer may be formed on a part of the surface of the aluminum alloy layer. That is, a part of the aluminum alloy layer may be exposed on the surface of the negative electrode without being covered by the carbon layer. For example, when forming a lithium-aluminum alloy layer, its surface may also become uneven, and the convex portions are exposed on the surface of the negative electrode. In addition, there may be a part on the surface of the lithium layer where the aluminum alloy layer is not formed and the carbon layer is directly formed.

[0042] However, the larger the area ratio of the part where the aluminum alloy layer and the carbon layer are formed on the lithium layer, the easier it is to produce the effects of the present invention. Therefore, the area ratio of the surface of the aluminum alloy layer where the carbon layer is formed is preferably 40% or more, more preferably 70% or more, and particularly preferably 100%, that is, the carbon layer is formed on the entire surface of the aluminum alloy layer.

[0043] Furthermore, it is most preferable that the aluminum alloy layer is formed on the entire surface of the lithium layer, and the carbon layer is formed on the entire surface of the aluminum alloy layer.

[0044] The carbon layer can be formed, for example, by a method of coating a carbon layer forming composition (liquid compositions such as paste and slurry) in which carbon and, further, a binder added as required (the binder may also be dissolved) are dispersed in an organic solvent on the surface of the aluminum layer in a laminate having a lithium layer and an aluminum layer and drying.

[0045] As the organic solvent used in the composition for forming the carbon layer, it is preferable to use the solvent used in the non-aqueous electrolyte of the battery. Specific examples thereof include cyclic carbonates such as ethylene carbonate, propylene carbonate (PC), butylene carbonate, and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; ethers such as 1,2-dimethoxyethane (DME), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, methoxyethoxyethane, 1,2-diethoxyethane, and tetrahydrofuran; cyclic esters such as γ-butyrolactone; nitriles; etc. One or two of them can be used. Carbonates such as propylene carbonate react with lithium to form lithium carbonate, and there is a risk of reducing the reactivity of the negative electrode surface. Therefore, from the viewpoint of more easily exerting the effects of the present invention, it is preferable to use solvents other than carbonates, more preferably ethers, and further preferably DME.

[0046] In addition, as the organic solvent used in the composition for forming the carbon layer, the solvent used when forming a coating such as a slurry having a positive electrode active material can also be used. In the case of using a fine carbon material such as carbon black, compounds having a five-membered ring lactam structure such as 2-pyrrolidone and N-methyl-2-pyrrolidone (NMP) can disperse the above carbon material well, so they are preferably used. The compounds having a five-membered ring lactam structure can also be used in admixture with the solvent used in the non-aqueous electrolyte.

[0047] The negative electrode can be composed only of a lithium layer, a lithium-aluminum alloy layer, and a carbon layer, or can further have a current collector as needed.

[0048] As the negative electrode current collector, negative electrode current collectors made of copper, nickel, iron, and stainless steel as raw materials can be cited. As its form, plain woven metal mesh, expanded metal mesh, lath mesh, stamped metal, metal foam, foil (sheet), etc. can be exemplified. The thickness of the current collector is preferably 5 to 100 μm, for example. It is also preferable to previously coat a paste-like conductive material such as carbon paste or silver paste on the surface of such a current collector.

[0049] The positive electrode related to the non-aqueous electrolyte battery can, for example, use a molded body obtained by molding a mixture (positive electrode mixture) containing a positive electrode active material, a conductive assistant, a binder, etc. into a granular shape or the like, and having a structure in which a layer (positive electrode mixture layer) composed of the above positive electrode mixture is provided on one or both sides of a current collector.

[0050] As the positive electrode active material, manganese dioxide, lithium-containing manganese oxides [for example, LiMn 3 O 6, composite oxides having the same crystal structure as manganese dioxide (such as β-type, γ-type, or a structure in which β-type and γ-type coexist), with the Li content being 3.5% by mass or less, preferably 2% by mass or less, more preferably 1.5% by mass or less, and particularly preferably 1% by mass or less), Li a Ti 5 / 3 O 4 (4 / 3 ≤ a < 7 / 3) and other lithium-containing composite oxides; vanadium oxides; niobium oxides; titanium oxides; sulfides such as iron disulfide; graphite fluoride; etc.

[0051] In addition, examples of the conductive aids involved in the positive electrode mixture include flake graphite, acetylene black, Ketjen black, carbon black, etc. One of them can be used alone, or two or more of them can be used in combination.

[0052] Furthermore, examples of the binders involved in the positive electrode mixture include fluororesins such as PVDF, PTFE, and polymers of hexafluoropropylene, etc. One of them can be used alone, or two or more of them can be used in combination.

[0053] In the case of the molded body of the positive electrode mixture, the positive electrode can be manufactured, for example, by pressure-molding the positive electrode mixture prepared by mixing a positive electrode active material, a conductive aid, a binder, etc. into a predetermined shape.

[0054] In addition, in the case of a positive electrode having a positive electrode mixture layer and a current collector, it can be manufactured, for example, through the following process: dispersing a positive electrode active material, a conductive aid, a binder, etc. in water or an organic solvent such as N-methyl-2-pyrrolidone (NMP) to prepare a composition containing the positive electrode mixture (slurry, paste, etc.) (the binder can also be dissolved in the solvent), coating it on the current collector and drying it, and performing pressing treatments such as calendering as needed.

[0055] However, the positive electrode is not limited to the positive electrode manufactured by the above methods, and can also be a positive electrode manufactured by other methods.

[0056] Regarding the composition of the positive electrode mixture involved in the positive electrode, the amount of the positive electrode active material is preferably 80 to 90% by mass, the content of the conductive aid is preferably 1.5 to 10% by mass, and the content of the binder is preferably 0.3 to 10% by mass.

[0057] In the case of the molded body of the positive electrode mixture, its thickness is preferably 0.15 to 4 mm. On the other hand, in the case of a positive electrode having a positive electrode mixture layer and a current collector, the thickness of the positive electrode mixture layer (the thickness on each side of the current collector) is preferably 30 to 300 μm.

[0058] When a current collector is used in the positive electrode, examples of the current collector include current collectors made of stainless steels such as SUS316, SUS430, and SUS444. As its form, a plain woven metal mesh, an expanded metal mesh, a lath mesh, a stamped metal, a metal foam, a foil (sheet), etc. can be exemplified. The thickness of the current collector is preferably, for example, 0.05 to 0.2 mm. It is also preferable to previously coat a paste-like conductive material such as a carbon paste or a silver paste on the surface of such a current collector.

[0059] The non-aqueous electrolyte battery of the present invention is assembled using a laminate (laminated electrode body) in which the above-mentioned negative electrode and the above-mentioned positive electrode are laminated with a separator interposed therebetween, a wound body (wound electrode body) obtained by winding the laminate in a spiral shape, and further a flat wound body (flat wound electrode body) having a flat cross section formed from the wound body, etc. In addition, the non-aqueous electrolyte battery of the present invention can also be assembled using a positive electrode composed of a formed body of a positive electrode mixture and the above-mentioned negative electrode, with a separator interposed therebetween and housed in a flat battery case.

[0060] In addition, the above-mentioned laminate for negative electrode can be used instead of the above-mentioned negative electrode to assemble the battery, and the negative electrode is formed during the assembly.

[0061] As the separator, a non-woven fabric or a microporous membrane (microporous film) is used. As its raw material, polyolefins such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer can be used. In addition, when heat resistance is required due to the relationship with the battery use, fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polybutylene terephthalate (PBT), polymethylpentene, polyamide, polyimide, aromatic polyamide, cellulose, etc. can also be used. The raw material of the non-woven fabric or the microporous membrane can use only one of the above-exemplified raw materials, or two or more kinds. In addition, the non-woven fabric or the microporous membrane forming the separator can be a non-woven fabric or a microporous membrane having a laminated structure in which multiple non-woven fabrics or microporous membranes made of different raw materials are laminated, in addition to the non-woven fabric or the microporous membrane having a single-layer structure composed of the above-exemplified raw materials.

[0062] From the viewpoint of suppressing a decrease in the energy density of the battery, the thickness of the separator is, for example, preferably 500 μm or less, more preferably 450 μm or less, and still more preferably 300 μm or less. However, if the separator is too thin, there is a risk of a reduction in the function of preventing short circuits. Therefore, when using a non-woven fabric, its thickness is, for example, preferably 30 μm or more, more preferably 100 μm or more, and still more preferably 150 μm or more. In addition, when using a microporous membrane, it is preferably 10 μm or more, more preferably 15 μm or more.

[0063] As the non-aqueous electrolyte of a non-aqueous electrolyte battery, a non-aqueous electrolyte prepared by dissolving LiPF 6 、LiBF 4 、LiClO 4 、LiCF 3 SO 3 etc. in an organic solvent can be cited. As the organic solvent, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate can be cited; chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; ethers such as 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, methoxyethoxyethane, 1,2-diethoxyethane, and tetrahydrofuran; cyclic esters such as γ-butyrolactone; mononitriles such as acetonitrile and propionitrile; etc., and one or more of them can be used. A combination of the above carbonates and ethers is particularly preferred.

[0064] When using a carbonate and an ether in combination as the non-aqueous electrolyte solvent, the volume ratio of the carbonate to the ether in the total solvent (mixing ratio) is preferably set to carbonate:ether = 30:70 to 70:30.

[0065] The concentration of the electrolyte in the non-aqueous electrolyte is preferably 0.3 to 1.5 mol / l.

[0066] Furthermore, in order to improve the storage characteristics at high temperatures, etc., additives can also be contained in the non-aqueous electrolyte as needed. As the additives that can be used, saturated sultone compounds such as 1,3-propane sultone and 1,4-butane sultone can be cited; unsaturated sultone compounds such as 1,3-propene sultone; acid anhydrides such as maleic anhydride and phthalic anhydride; organic lithium borates such as LiB(C 2 O 4 ) 2 etc.; dinitriles such as malononitrile, succinonitrile, glutaronitrile, and adiponitrile; etc., and one or more of them can be used.

[0067] The content of the above additives in the non-aqueous electrolyte is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and particularly preferably 0.5% by mass or more. On the other hand, if the content of the additives is too high, there is a risk of an increase in the internal resistance of the battery and a decrease in the discharge characteristics. Therefore, the content of the additives in the non-aqueous electrolyte is preferably 3% by mass or less, more preferably 2% by mass or less, and particularly preferably 1.5% by mass or less.

[0068] Regarding the form of the non-aqueous electrolyte battery, there is no particular limitation, and it can be set to various forms such as flat (including coin-shaped and button-shaped), laminated, cylindrical (cylindrical, square (square cylinder-shaped)), etc. In addition, as the outer package (battery case) that houses the negative electrode, positive electrode, separator, and non-aqueous electrolyte, a metal can (outer can) with an opening and a lid (sealing can) can be combined and used, or a metal laminated film can be used.

[0069] Specifically, a flat or cylindrical battery can be produced by riveting and sealing the outer can and the sealing can with a gasket in between, or by welding the outer can and the sealing can for sealing. A laminated battery can be produced by overlapping two metal laminated films, or by bending one metal laminated film and bonding the surrounding for sealing.

[0070] It should be noted that in the case of using an outer package in the form of riveting and sealing, the raw material of the gasket between the outer can and the sealing can can be PP, nylon, etc. In addition, in the case where particularly high heat resistance is required due to the relationship with the battery application, heat-resistant resins such as PFA and other fluororesins, polyphenylene ether (PEE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), PPS, and PEEK with a melting point or thermal decomposition temperature of 200 °C or higher can also be used. In addition, when the battery is applied to applications requiring heat resistance, its sealing can also use glass vacuum sealing.

[0071] Examples

[0072] Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

[0073] (Example 1)

[0074] <Fabrication of Positive Electrode>

[0075] A positive electrode mixture prepared by mixing manganese dioxide as a positive electrode active material, carbon black as a conductive assistant, and PTFE as a binder in a mass ratio of 90:5:5 was formed to obtain a positive electrode (positive electrode mixture formed body) with a diameter of 16 mm and a thickness of 1.8 mm.

[0076] <Fabrication of Negative Electrode Stack>

[0077] An aluminum foil with a thickness of 9 μm was crimped onto one side of a lithium foil with a thickness of 1.2 mm, and it was punched into a circle with a diameter of 16 mm to obtain a stack of a lithium layer and an aluminum layer.

[0078] Next, acetylene black was dispersed in propylene carbonate to prepare a carbon layer-forming composition (slurry), and the slurry was coated on the aluminum layer of the laminate and dried, thereby producing a negative electrode laminate having a carbon layer composed of acetylene black formed on the entire surface of the aluminum layer of the laminate. The weight per unit area of the carbon layer was 0.5 mg / cm 2 .

[0079] <Modulation of non-aqueous electrolyte>

[0080] LiClO 4 was dissolved in a mixed solvent obtained by mixing propylene carbonate and 1,2-dimethoxyethane at a volume ratio of 1:1 at a concentration of 0.5 mol / l, and 1,3-propane sultone: 2% by mass was further added to prepare a non-aqueous electrolyte.

[0081] <Assembly of battery>

[0082] Using the above positive electrode, negative electrode laminate and non-aqueous electrolyte, a non-woven fabric made of polymethylpentene (thickness: 320 μm) was used as the separator, and a coin-shaped non-aqueous electrolyte primary battery with a diameter of 20 mm and a height of 3.2 mm was assembled according to the Figure 1 shown structure.

[0083] By bringing the negative electrode laminate into contact with the non-aqueous electrolyte, a negative electrode having a lithium-aluminum alloy layer formed on the surface of the lithium layer and further having a carbon layer on the lithium-aluminum alloy layer was formed in the battery.

[0084] (Example 2)

[0085] The weight per unit area of the carbon layer on the surface of the negative electrode laminate was set to 0.02 mg / cm 2 , and except for this, a coin-shaped non-aqueous electrolyte primary battery was assembled in the same manner as in Example 1.

[0086] (Example 3)

[0087] The weight per unit area of the carbon layer on the surface of the negative electrode laminate was set to 0.2 mg / cm 2 , and except for this, a coin-shaped non-aqueous electrolyte primary battery was assembled in the same manner as in Example 1.

[0088] (Example 4)

[0089] The weight per unit area of the carbon layer on the surface of the negative electrode laminate was set to 1 mg / cm 2 , and except for this, a coin-shaped non-aqueous electrolyte primary battery was assembled in the same manner as in Example 1.

[0090] (Example 5)

[0091] A slurry was prepared by dispersing acetylene black in 1,2-dimethoxyethane, and a carbon layer was formed using the above slurry. Except for this, a coin-shaped non-aqueous electrolyte primary battery was assembled in the same manner as in Example 1.

[0092] (Example 6)

[0093] The weight per unit area of the carbon layer on the surface of the negative electrode laminate was set to 0.02 mg / cm 2 , and except for this, a coin-shaped non-aqueous electrolyte primary battery was assembled in the same manner as in Example 5.

[0094] (Example 7)

[0095] The weight per unit area of the carbon layer on the surface of the negative electrode laminate was set to 0.2 mg / cm 2 , and except for this, a coin-shaped non-aqueous electrolyte primary battery was assembled in the same manner as in Example 5.

[0096] (Example 8)

[0097] The weight per unit area of the carbon layer on the surface of the negative electrode laminate was set to 1 mg / cm 2 , and except for this, a coin-shaped non-aqueous electrolyte primary battery was assembled in the same manner as in Example 5.

[0098] (Comparative Example 1)

[0099] A slurry prepared in Example 1 was coated on one side of a lithium foil with a thickness of 1.2 mm and dried to produce a laminate of a lithium layer and a carbon layer in which the carbon layer was integrally formed on one side of the lithium layer. The weight per unit area of the above carbon layer was 0.5 mg / cm 2 . The above laminate was used instead of the negative electrode laminate of Example 1, and except for this, a coin-shaped non-aqueous electrolyte primary battery was assembled in the same manner as in Example 1.

[0100] (Comparative Example 2)

[0101] The carbon layer was formed using the slurry prepared in Example 5, and except for this, a coin-shaped non-aqueous electrolyte primary battery was assembled in the same manner as in Comparative Example 1.

[0102] (Comparative Example 3)

[0103] The carbon layer-forming composition was not coated on the surface of the laminate of the lithium layer and the aluminum layer, and the above laminate was directly used for the assembly of the battery. Except for this, a coin-shaped non-aqueous electrolyte primary battery was assembled in the same manner as in Example 1.

[0104] The batteries of Examples 1 to 8 and Comparative Examples 1 to 3 were kept in a thermostat at -40°C. After the temperature of the batteries decreased, they were discharged at a current value of 10 mA, and the battery discharge voltage (CCV) 8 m seconds after the start of discharge was measured to evaluate the load characteristics at low temperature before storage.

[0105] Separately from the above evaluation, after storing the batteries of Examples 1 to 8 and Comparative Examples 1 to 3 in a high-temperature environment at 120°C for 500 hours, the discharge voltage of the batteries was measured in the same manner as above to evaluate the load characteristics at low temperature after high-temperature storage. The respective measurement results are shown in Table 1 and Figure 2 in.

[0106] [Table 1]

[0107]

[0108] As Figure 2 shown by the results, in the batteries of Examples 1 to 4 and Examples 5 to 8 in which a lithium-aluminum alloy layer is formed on the surface of the lithium layer of the negative electrode and a carbon layer is further formed on the above lithium-aluminum alloy layer, in any case before storage and after high-temperature storage, the greater the weight per unit area of the carbon layer, the higher the discharge voltage of the battery, and the more the load characteristics at low temperature can be improved.

[0109] In addition, the batteries of Examples 5 to 8 using DME as the solvent of the composition for forming the carbon layer can increase the discharge voltage of the battery compared with the batteries of Examples 1 to 4 using PC, and further can more effectively suppress the decrease in the discharge voltage caused by high-temperature storage. This is considered because the carbon dispersion in the composition for forming the carbon layer using DME as the solvent is better, and a uniform carbon layer can be formed, and problems such as the formation of lithium carbonate when using PC as the solvent do not occur.

[0110] On the other hand, in the batteries of Comparative Examples 1 and 2 in which a carbon layer is directly formed on the surface of the lithium layer, even when the weight per unit area of the carbon layer is increased to 0.5 mg / cm 2 , the decrease in the discharge voltage caused by high-temperature storage also increases to about 1 V. In addition, for the battery of Comparative Example 3 in which a lithium-aluminum alloy layer is formed on the surface of the lithium layer but no carbon layer is formed thereon, similarly, the decrease in the discharge voltage caused by high-temperature storage also increases to about 1 V.

[0111] In the battery of the present invention, as shown in Table 1, by forming a lithium-aluminum alloy layer between the lithium layer and the carbon layer, even if the weight per unit area of the carbon layer is reduced, the decrease in the discharge voltage caused by high-temperature storage can be sufficiently suppressed.

[0112] The present invention can be implemented in other ways without departing from its gist. The embodiments disclosed in this application are examples, and the present invention is not limited to these embodiments. Compared with the description in the above specification, the scope of the present invention is preferably interpreted by the description in the appended claims, and all changes within the scope equivalent to the claims are included in the claims.

[0113] Industrial Applicability

[0114] The non-aqueous electrolyte battery of the present invention mainly adopts the form of a primary battery, and can also adopt the form of a secondary battery, and can be applied to various uses of non-aqueous electrolyte primary batteries and non-aqueous electrolyte secondary batteries known in the past.

[0115] Symbol Explanation

[0116] 1 Non-aqueous electrolyte battery

[0117] 2 Positive electrode

[0118] 3 Negative electrode

[0119] 4 Separator

[0120] 5 Outer can

[0121] 6 Sealing can

[0122] 7 Insulating washer.

Claims

1. A non-aqueous electrolyte battery, which is a non-aqueous electrolyte battery having a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, characterized in that, the negative electrode has a lithium layer with a lithium-aluminum alloy layer formed on its surface, and further has a carbon layer on the lithium-aluminum alloy layer, and the carbon layer contains carbon black.

2. The non-aqueous electrolyte battery according to claim 1, wherein the weight per unit area of the carbon layer is 0.15 mg / cm 2 or more.

3. The non-aqueous electrolyte battery according to claim 1 or 2, wherein the weight per unit area of the carbon layer is 1.5 mg / cm 2 or less.

4. The non-aqueous electrolyte battery according to claim 1 or 2, wherein the carbon layer contains a binder.

5. The non-aqueous electrolyte battery according to claim 1 or 2, wherein the positive electrode contains manganese dioxide, or a lithium-containing manganese oxide having the same crystal structure as manganese dioxide and a Li content of 3.5% by mass or less as a positive electrode active material.

6. The non-aqueous electrolyte battery according to claim 1 or 2, wherein the area ratio of the portion of the surface of the lithium layer where the lithium-aluminum alloy layer is formed is 40% or more.

7. The non-aqueous electrolyte battery according to claim 6, wherein the lithium-aluminum alloy layer is formed on the entire surface of the lithium layer.

8. The non-aqueous electrolyte battery according to claim 1 or 2, wherein the area ratio of the portion of the surface of the lithium-aluminum alloy layer where the carbon layer is formed is 70% or more.

9. The non-aqueous electrolyte battery according to claim 8, wherein the carbon layer is formed on the entire surface of the lithium-aluminum alloy layer.

10. The non-aqueous electrolyte battery according to claim 1 or 2, wherein the lithium-aluminum alloy layer has cracks.

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