Non-aqueous electrolyte secondary battery electrode comprising porous metal-containing current collector and organosulfur-based active material, non-aqueous electrolyte secondary battery containing said electrode, and organosulfur-based active material for manufacturing said electrode

Abstract

Provided according to the present disclosure are: a non-aqueous electrolyte secondary battery comprising a porous metal-containing current collector and an organosulfur-based active material; a non-aqueous electrolyte secondary battery comprising the electrode as a positive electrode or negative electrode; and an organosulfur-based active material used to manufacture the electrode.

Description

Electrode for non-aqueous electrolyte secondary battery containing current collector including porous metal and organic sulfur-based active material, non-aqueous electrolyte secondary battery containing said electrode, and organic sulfur-based active material for manufacturing said electrode

[0001] The present invention relates to an electrode for use in a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery using the electrode, or an organic sulfur-based active material used in the manufacture of the electrode.

[0002] The characteristics of non-aqueous electrolyte secondary batteries depend on their constituent materials, such as electrodes, separators, and electrolytes, and research and development of each of these components is being actively conducted. For electrodes, electrode active materials are important components, along with binders and current collectors, and research and development of these materials is being actively conducted.

[0003] Organic sulfur-based active materials such as sulfur-modified polyacrylonitrile are known as electrode active materials that have a large charge / discharge capacity and exhibit little decrease in charge / discharge capacity with repeated charge / discharge (hereinafter, sometimes referred to as "cycle characteristics") (see, for example, Patent Documents 1 to 4). Organic sulfur-based active materials are used as positive electrode active materials, but depending on the positive electrode active material, they can also be used as negative electrode active materials (see, for example, Patent Documents 5 and 6).

[0004] On the other hand, with regard to current collectors, metal current collectors using porous metal bodies having a three-dimensional network structure are known, and it is known that non-aqueous electrolyte secondary batteries using such metal current collectors have improved active material utilization rates and charge / discharge efficiency (see, for example, Patent Documents 7 and 8).

[0005] International Publication No. 2010 / 044437 JP 2011-028948 A International Publication No. 2012 / 114651 International Publication No. 2013 / 001693 JP 2014-096326 A International Publication No. 2019 / 225588 JP 2002-203542 A Japanese Patent Application Laid-Open No. 2012-174495 A

[0006] Further improvements in the battery characteristics of nonaqueous electrolyte secondary batteries are required. In particular, nonaqueous electrolyte secondary batteries used in electric vehicles or hybrid vehicles are required to be lightweight, have a large charge / discharge capacity, and exhibit good cycle characteristics. In order to increase the charge / discharge capacity of an electrode, it is effective to increase the content of electrode active material per unit area of ​​the electrode, i.e., the so-called basis weight. In nonaqueous electrolyte secondary batteries, multiple positive electrodes and negative electrodes are stacked on top of each other. Although an increase in basis weight increases the weight of the electrode, an increase in charge / discharge capacity allows the number of electrodes to be reduced, leading to a weight reduction of the nonaqueous electrolyte secondary battery.

[0007] In nonaqueous electrolyte secondary batteries, such as lithium-ion secondary batteries, the electrode active material absorbs or releases lithium ions during charging and discharging, causing the volume to increase or decrease, resulting in fluctuations in the thickness of the electrode mixture layer. One of the causes of a decrease in the charge / discharge capacity of a battery is thought to be an increase in strain within the electrode mixture layer due to fluctuations in the thickness of the electrode mixture layer during charging and discharging. Increasing the thickness of the electrode mixture layer and increasing the basis weight of the electrode active material is effective for increasing the energy density of a battery. However, increasing the thickness of the electrode mixture layer also increases strain within the electrode mixture layer, making the battery's cycle characteristics more susceptible to deterioration. In particular, organic sulfur-based active materials have a problem in that they experience a larger volume change during charging and discharging than other electrode active materials, making it difficult to increase the basis weight.

[0008] As a result of extensive investigations, the present inventors have found that by using a porous metal body as a current collector, a nonaqueous electrolyte secondary battery with good cycle characteristics can be obtained even when the basis weight of the organic sulfur-based active material, which is the electrode active material, is increased, and have completed the present invention. That is, the present invention relates to an electrode for a nonaqueous electrolyte secondary battery comprising a porous metal current collector and an organic sulfur-based active material, a nonaqueous electrolyte secondary battery comprising the electrode, or an organic sulfur-based active material used in producing the electrode.

[0009] By using a current collector containing the porous metal disclosed in this specification, it is possible to increase the basis weight of an electrode using an organic sulfur-based active material as an electrode active material, thereby providing a nonaqueous electrolyte secondary battery with large charge / discharge capacity and excellent cycle characteristics.

[0010] Fig. 1 is an exploded perspective view schematically showing an electrode group 6 of a laminated nonaqueous electrolyte secondary battery 9. Fig. 2 is an exploded perspective view schematically showing the laminated nonaqueous electrolyte secondary battery 9. Fig. 3 is an external plan view schematically showing the laminated nonaqueous electrolyte secondary battery 9.

[0011] [A. Electrode for Non-Aqueous Electrolyte Secondary Battery] First, the electrode for a non-aqueous electrolyte secondary battery of the present invention (hereinafter, sometimes referred to as the "electrode of the present invention") will be described. The electrode of the present invention is an electrode comprising a current collector and an organic sulfur-based active material, characterized in that the current collector is a current collector comprising porous metal (hereinafter, sometimes referred to as a "porous metal current collector" or "current collector of the present invention"). Each component used in the electrode of the present invention will be described in detail below.

[0012] [A-1. Current Collector] The electrode of the present invention includes a porous metal current collector. In secondary battery electrodes, the surface of the current collector may be surface-treated or coated with carbon or the like to improve adhesion and electrical characteristics. The current collector of the present invention may include a surface-treated layer and / or a coating layer on the porous metal.

[0013] The shape of the current collector of the present invention is not particularly limited and may be any of mesh, woven fabric, nonwoven fabric, embossed, punched, expanded, foamed, etc. However, a thick current collector with a high porosity is preferred because the organic sulfur-based active material is supported in the pores of the current collector, allowing for a high basis weight of the organic sulfur-based active material. The porosity of the current collector can be calculated using the following formula. The bulk volume of the current collector in the formula refers to the volume including the pores of the current collector, and specifically, is the sum of the volume of the current collector material, the volume of the pores within the current collector, and the volume of the spaces in the uneven parts of the current collector surface. The bulk volume of the current collector is measured in accordance with the density measurement method of JIS P8118 (Paper and paperboard - Test methods for thickness, density, and specific volume). In the JIS standard, thickness is measured using a micrometer by applying a pressure of 100 kPa to a pressure surface with a diameter of 16 mm. However, if the voids in the current collector of the present invention are deformed, the current collector of the present invention is sandwiched between two metal plates of known thickness that will not deform under the measurement pressure, and the measurement is performed at a pressure just before the voids are deformed. Current collector porosity [%] = (1 - (current collector mass [g] / (current collector bulk volume [cm3 ]×material density of current collector)) × 100

[0014] The current collector preferably has a three-dimensional mesh structure because the thickness is large and the porosity is high. In the present invention, the three-dimensional mesh structure refers to a structure in which the mesh exists not only in the planar direction of the current collector but also in the thickness direction. Among the shapes of current collectors, examples of the three-dimensional mesh structure include nonwoven fabrics and foams. Foams are preferred because they can provide an electrode with sufficient physical strength even when the porosity is high.

[0015] The thickness of the current collector of the present invention is preferably 0.1 mm to 10 mm, more preferably 0.2 mm to 7 mm, and even more preferably 0.3 mm to 5 mm, because this improves charge / discharge efficiency. Note that, in the case of a secondary battery electrode, a pressing process may be performed after the electrode active material is supported on the current collector, but the thickness of the current collector of the present invention refers to the thickness of the current collector used in the electrode, not the thickness of the current collector portion of the electrode after the pressing process.

[0016] The porosity of the current collector of the present invention is preferably 80% to 99%, and more preferably 90% to 99%, because this increases the basis weight of the organic sulfur-based active material and results in an electrode with high physical strength. Note that the porosity of the current collector of the present invention refers to the porosity of the current collector used in the electrode, and not the porosity of the current collector portion of the electrode after press treatment.

[0017] Specific examples of the porous metal contained in the current collector of the present invention include titanium, aluminum, copper, nickel, stainless steel, and nickel-plated steel, among which aluminum is preferred because of its excellent conductivity and light weight, and it is more preferred that the porous metal be made of aluminum. Therefore, the current collector of the present invention is preferably a porous aluminum current collector.

[0018] A current collector having a foamed shape has numerous pores, which act as voids and support the electrode active material. When the current collector of the present invention has a foamed shape, if the pores are too small, it is difficult to support the organic sulfur-based active material, and if they are too large, the charge / discharge capacity is reduced. Therefore, the average inner diameter of the pores is preferably 50 μm to 1,000 μm, and more preferably 100 μm to 700 μm. The average inner diameter of the pores is the average value of the opening diameters (inner diameters of the pores) observed in the cross section of the current collector of the present invention. The opening diameter refers to the maximum distance between two points passing through the inner circumference forming the openings. The average inner diameter of the pores is the average value obtained by observing at least 10 locations on the current collector of the present invention and measuring the opening diameters of at least 10 adjacent pores per location. The cross section of the current collector of the present invention may be measured, for example, by magnifying it using a microscope photograph or the like.

[0019] When the current collector of the present invention is in the form of a foam, interconnected pores are preferred because this allows the slurry containing the organic sulfur-based active material to enter the pores and be easily supported. Interconnected pores are pores that are interconnected with each other and have at least one open pore. Pores that are not interconnected with other pores are sometimes called closed pores. A porous metal current collector with interconnected pores and few closed pores can be obtained, for example, by forming a metal layer on the surface of the pores of a foamed resin such as polyurethane by plating or other methods, and then decomposing and removing the foamed resin. Examples of such porous metal current collectors include Celmet (trade name) and Aluminum Celmet (trade name) from Sumitomo Electric Industries, Ltd.

[0020] [A-2. Organic sulfur-based active material] In the present invention, the organic sulfur-based active material refers to a compound that can absorb and release lithium ions and can be used as an electrode active material for a secondary battery, and that has carbon atoms and sulfur atoms. Examples of the organic sulfur-based active material include compounds represented by the general formula (CS x ) m (where x is 0.5 to 2 and m is a number of 4 or more), polycarbon sulfide represented by the general formula (CS y ) n(y is a number from 2.5 to 50, and n is a number equal to or greater than 2), and thermally modified organic sulfur compounds. Thermally modified organic sulfur compounds are compounds obtained by heat-treating a mixture of an organic compound and elemental sulfur in a non-oxidizing atmosphere, and examples thereof include sulfur-modified polyacrylonitrile, sulfur-modified elastomer, sulfur-modified polynuclear aromatic ring compound, sulfur-modified pitch, polythienoacene compound, sulfur-modified polyether, sulfur-modified polyamide solvent, and sulfur-modified aliphatic hydrocarbon oxide.

[0021] Sulfur-modified polyacrylonitrile is a compound obtained by heat-treating polyacrylonitrile and elemental sulfur in a non-oxidizing atmosphere. The heat-treatment temperature is not particularly limited, but is preferably 350°C to 550°C. The sulfur content of the sulfur-modified polyacrylonitrile is not particularly limited, but is preferably 25% by mass to 80% by mass. Here, the sulfur content in the organic sulfur-based active material is expressed as the concentration of sulfur relative to the total amount of the organic sulfur-based active material.

[0022] The sulfur-modified elastomer is a compound obtained by heat-treating a rubber such as natural rubber or isoprene rubber with elemental sulfur in a non-oxidizing atmosphere. The heat-treating temperature is not particularly limited, but is preferably 250° C. to 550° C. The sulfur content of the sulfur-modified elastomer is not particularly limited, but is preferably 30% by mass to 85% by mass.

[0023] The sulfur-modified polynuclear aromatic ring compound is a compound obtained by heat-treating a polynuclear aromatic ring compound such as naphthalene or anthracene with elemental sulfur in a non-oxidizing atmosphere. The heat-treatment temperature is not particularly limited, but is preferably 250° C. to 550° C. The sulfur content of the sulfur-modified polynuclear aromatic ring compound is not particularly limited, but is preferably 40% by mass to 85% by mass.

[0024] Sulfur-modified pitch is a compound obtained by heat-treating a mixture of pitches and elemental sulfur in a non-oxidizing atmosphere. Examples of pitches include petroleum pitch, coal pitch, mesophase pitch, asphalt, coal tar, coal tar pitch, organic synthetic pitch obtained by polycondensation of condensed polycyclic aromatic hydrocarbon compounds, and organic synthetic pitch obtained by polycondensation of heteroatom-containing condensed polycyclic aromatic hydrocarbon compounds. Pitches are mixtures of various compounds and may contain nitrogen and sulfur in addition to carbon and hydrogen. The heat treatment temperature is not particularly limited, but is preferably 300°C to 500°C. The sulfur content of the sulfur-modified pitch is not particularly limited, but is preferably 30% to 80% by mass.

[0025] The polythienoacene compound is a compound having a sulfur-containing polythienoacene structure represented by the following general formula (1).

[0026] (wherein * represents a bond)

[0027] The polythienoacene compound can be obtained by heat treating an aliphatic polymer compound having a linear structure such as polyethylene, or a polymer compound having a thiophene structure such as polythiophene, with elemental sulfur in a non-oxidizing atmosphere. The heat treatment temperature is not particularly limited, but is preferably 300°C to 600°C. The sulfur content of the polythienoacene compound is preferably 30 to 80% by mass, as this allows for a large charge / discharge capacity to be obtained.

[0028] The sulfur-modified polyether is a compound obtained by heat-treating a polyether compound such as polyethylene glycol or polypropylene glycol with elemental sulfur in a non-oxidizing atmosphere. The heat-treatment temperature is not particularly limited, but is preferably 250° C. to 500° C. The sulfur content of the sulfur-modified polyether is not particularly limited, but is preferably 40% by mass to 85% by mass.

[0029] Sulfur-modified polyamides are organic sulfur compounds having a carbon skeleton derived from a polymer having an amide bond. Specifically, they are compounds obtained by heat-treating a polymer of an aminocarboxylic acid compound and elemental sulfur, or a polymer of a polyamine compound and a polycarboxylic acid compound and elemental sulfur, in a non-oxidizing atmosphere. The heat-treating temperature is not particularly limited, but is preferably 250°C to 600°C. The sulfur content of the sulfur-modified polyamide is preferably 40% by mass to 70% by mass, as this provides a large charge / discharge capacity.

[0030] The sulfur-modified aliphatic hydrocarbon oxide is a compound obtained by heat-treating an aliphatic hydrocarbon oxide such as an aliphatic alcohol, an aliphatic aldehyde, an aliphatic ketone, an aliphatic epoxide, or a fatty acid with elemental sulfur in a non-oxidizing atmosphere. The heat-treatment temperature is not particularly limited, but is preferably 300°C to 500°C. The sulfur content of the sulfur-modified polyamide compound is not particularly limited, but is preferably 45% by mass to 80% by mass.

[0031] The sulfur content of the organic sulfur-based active material can be measured by performing elemental analysis using, for example, a CHN analyzer (such as Elementar's Vario MICRO Cube) capable of analyzing sulfur and oxygen.

[0032] Among organic sulfur-based active materials, thermally modified organic sulfur compounds are preferred because they have large charge / discharge capacities and excellent cycle characteristics, and sulfur-modified polyacrylonitrile is more preferred. The sulfur content of the sulfur-modified polyacrylonitrile is preferably 35% by mass to 65% by mass, more preferably 45% by mass to 55% by mass, because it has excellent cycle characteristics.

[0033] The particle diameter of the organic sulfur-based active material is preferably 0.5 μm to 30 μm, more preferably 1 μm to 20 μm, and even more preferably 2 μm to 15 μm, because excellent battery performance can be obtained. The particle diameter is a diameter based on volume, and in the present invention, the average particle diameter is the 50% particle diameter (D 50 )

[0034] Since the battery characteristics can be fully exhibited, the weight of the organic sulfur-based active material of the electrode of the present invention is 15 mg / cm2 ~50 mg / cm 2 and preferably 20 mg / cm 2 ~40 mg / cm 2 It is more preferable that:

[0035] In an electrode using a metal foil as a current collector, the basis weight of the electrode active material usually refers to the mass of the electrode active material per area of ​​the portion of the electrode containing the electrode active material. However, in the present invention, for an electrode using a porous metal current collector as a current collector, the basis weight of the electrode active material is defined as half the mass of the electrode active material contained in the electrode relative to the area of ​​the portion containing the electrode active material calculated from the outer shape of the electrode when viewed in plan. This is because, in an electrode using a metal foil as a current collector, only the surface containing the electrode active material is usable as an electrode, and there are cases where it is one-sided or both-sided, whereas in an electrode using a porous metal current collector, as in the electrode of the present invention, both sides of the electrode are usable. Note that, in the case where the electrode of the present invention has a curved surface, such as a wound electrode, the curved surface of the electrode is deformed into a flat surface and then the basis weight is calculated in plan view.

[0036] The electrode of the present invention uses the current collector of the present invention, which allows for a significantly increased basis weight of the organic sulfur-based active material compared to when a metal foil current collector is used, thereby increasing the charge / discharge capacity of the electrode. In non-aqueous electrolyte secondary batteries, a large number of positive electrodes and negative electrodes are usually stacked alternately to obtain high output. Although the electrode of the present invention increases the basis weight of the active material, the increased charge / discharge capacity allows for a reduction in the number of electrodes used, thereby reducing the weight of the non-aqueous electrolyte secondary battery.

[0037] [A-3. Slurry] As a method for producing the electrode of the present invention, a method can be used in which an organic sulfur-based active material is mixed with a solvent to form a slurry, and the slurry is then applied to the current collector of the present invention. The organic sulfur-based active material may be supported alone on the current collector of the present invention, but it is preferably supported together with a conductive aid and a binder, as this improves conductivity and adhesion to the current collector. Therefore, when producing the electrode of the present invention by a slurry application method, it is preferable to mix a conductive aid and a binder with the slurry containing the organic sulfur-based active material. In addition to the electrode active material, a layer containing a conductive aid, a binder, etc. is sometimes referred to as an electrode mixture layer.

[0038] [A-3-1. Conductive Aid] The conductive aid used in the present invention may be any known conductive aid for electrodes. Specific examples include carbon materials such as carbon black, ketjen black, acetylene black, channel black, furnace black, lamp black, thermal black, carbon nanotubes, vapor grown carbon fiber (VGCF), graphene, fullerene, needle coke, and graphite; metal powders such as aluminum powder, nickel powder, and titanium powder; conductive metal oxides such as zinc oxide and titanium oxide; and sulfides such as LaS, S, CeS, and TiS.

[0039] The particle size of the conductive additive is preferably 0.0001 μm to 30 μm, and more preferably 0.01 μm to 20 μm, in order to improve conductivity. The content of the conductive additive in the electrode mixture layer is preferably 0.01 mass % to 15 mass %, more preferably 0.2 mass % to 10 mass %, and even more preferably 1 to 5 mass %, relative to the mass of the electrode mixture layer, in order to improve conductivity.

[0040] [A-3-2. Binder] The binder may be any known binder for electrodes. Examples include styrene-butadiene rubber, butadiene rubber, polyethylene, polypropylene, polyamide, polyamideimide, polyimide, polyacrylonitrile, polyurethane, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-propylene-diene rubber, fluororubber, styrene-acrylic acid ester copolymer, ethylene-vinyl alcohol copolymer, acrylonitrile butadiene rubber, styrene-isoprene rubber, polymethyl methacrylate, polyacrylate, polyvinyl alcohol, polyvinyl ether, carboxymethyl cellulose, sodium carboxymethyl cellulose, methyl cellulose, cellulose nanofiber, polyethylene oxide, starch, polyvinylpyrrolidone, polyvinyl chloride, and polyacrylic acid.

[0041] As the binder, an aqueous binder is preferred because it has a low environmental impact and is less likely to cause sulfur elution, and styrene-butadiene rubber, sodium carboxymethyl cellulose, and polyacrylic acid are particularly preferred. Only one type of binder can be used, or two or more types can be used in combination.

[0042] [A-3-3. Solvent] The solvent for preparing the slurry may be any solvent that has appropriate volatility and is dispersible without reacting with the organic sulfur-based electrode active material, conductive aid, binder, etc., and examples thereof include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, acetonitrile, propionitrile, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, nitromethane, N-methylpyrrolidone, N,N-dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N,N-dimethylaminopropylamine, polyethylene oxide, tetrahydrofuran, dimethyl sulfoxide, sulfolane, γ-butyrolactone, water, and alcohol. The amount of solvent used can be adjusted according to the coating method selected when coating the slurry. For example, when coating by a die coater method, the amount of solvent used is preferably 10 parts by mass to 300 parts by mass, and more preferably 20 parts by mass to 200 parts by mass, relative to 100 parts by mass of the total amount of the organic sulfur-based electrode active material, the conductive additive, and the binder.

[0043] [A-3-4. Other Components] The slurry may further contain other components, such as viscosity adjusters, reinforcing agents, antioxidants, and penetration enhancers.

[0044] The method for preparing the slurry is not particularly limited, and examples thereof include methods using a conventional ball mill, sand mill, bead mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, rotation / revolution mixer, planetary mixer, film mix, jet paster, etc.

[0045] The method for applying the slurry to the porous metal current collector is not particularly limited, and any of various methods can be used, such as a die coater method, a comma coater method, a curtain coater method, a spray coater method, a gravure coater method, a flexo coater method, a knife coater method, a doctor blade method, a reverse roll method, a brush coating method, an immersion method, etc. When applying by the immersion method, after immersing the porous metal current collector in the slurry, gas inside the porous metal current collector may be removed by ultrasonic irradiation or reduced pressure to make it easier for the slurry to enter the pores.

[0046] The method for drying the slurry applied to the porous metal current collector is not particularly limited, and various techniques can be used, such as drying with warm air, hot air, or low-humidity air, vacuum drying, leaving the slurry in a heating furnace, or irradiating it with far-infrared rays, infrared rays, or electron beams. This drying causes volatile components such as the solvent to volatilize from the coating of the slurry, forming an electrode mixture layer on the porous metal current collector. The electrode mixture layer may be formed by a single application and drying, or by repeated application and drying of the slurry. Since a thin electrode is preferred to make the battery small and lightweight, the electrode of the present invention is preferably pressed after the slurry has dried.

[0047] [B. Nonaqueous Electrolyte Secondary Battery] The electrode of the present invention can be preferably used as an electrode for a nonaqueous electrolyte secondary battery. A nonaqueous electrolyte secondary battery generally comprises a positive electrode, a negative electrode, a nonaqueous electrolyte, and a separator, and the electrode of the present invention may be used as either the positive electrode or the negative electrode of a nonaqueous electrolyte secondary battery. Examples of nonaqueous electrolyte secondary batteries include alkali metal secondary batteries such as lithium ion secondary batteries, sodium ion secondary batteries, and potassium ion secondary batteries. As nonaqueous electrolyte secondary batteries using the electrode of the present invention, lithium ion secondary batteries and sodium ion secondary batteries are preferred, and lithium ion secondary batteries are particularly preferred, because they provide large charge / discharge capacities and excellent cycle characteristics.

[0048] [B-1. Lithium-ion secondary battery (positive electrode)] First, the case where the electrode of the present invention is used as the positive electrode of a lithium-ion secondary battery will be described. Since the organic sulfur-based active material, which is the electrode active material of the electrode of the present invention, does not contain lithium, when the electrode active material of the negative electrode (negative electrode active material) does not contain lithium, a pre-doping process for inserting lithium metal into the positive electrode of the present invention is required, and even when the negative electrode active material contains lithium, it is preferable to pre-dope lithium in order to stably start the secondary battery. As a method for pre-doping lithium into the electrode of the present invention, a half-cell is assembled using metallic lithium as the counter electrode of the electrode of the present invention, and an electrolytic doping method in which lithium is electrochemically doped, a metallic lithium foil is attached to the electrode of the present invention, and the electrode is left in a non-aqueous electrolyte, and the diffusion doping method is used to dope by utilizing the diffusion of lithium into the electrode, etc.

[0049] [B-1-1. Negative Electrode] When the electrode of the present invention is used as the positive electrode of a lithium ion secondary battery, the negative electrode can be produced by a known method. For example, a compound containing a negative electrode active material, a conductive additive, and a binder is mixed in a solvent to form a slurry, which is then applied to a current collector and dried to produce a negative electrode in which an electrode mixture layer is formed on a current collector.

[0050] Examples of negative electrode active materials include natural graphite, artificial graphite, non-graphitizable carbon, easily graphitizable carbon, lithium, lithium alloys, silicon, silicon alloys, silicon oxide, tin, tin alloys, tin oxide, phosphorus, germanium, indium, copper oxide, antimony sulfide, titanium oxide, iron oxide, manganese oxide, cobalt oxide, nickel oxide, lead oxide, ruthenium oxide, tungsten oxide, and zinc oxide, as well as LiVO, LiVO, and LiTiO. 12 and other composite oxides.

[0051] The conductive additive, binder, and solvent may be the same as those exemplified in [A-3. Slurry] above. The method for preparing the slurry, the method for applying the slurry to the current collector, and the method for drying the slurry may also be the same as those exemplified in [A-3. Slurry] above.

[0052] In this case, the current collector can be prepared using a conductive material such as titanium, titanium alloy, aluminum, aluminum alloy, copper, nickel, stainless steel, nickel-plated steel, or carbon. Examples of the shape of the current collector include foil, plate, and mesh, and the current collector may be porous or non-porous. Metal-based negative electrode active materials such as lithium, lithium alloy, tin, and tin alloy have high conductivity, so the metal foil itself may be used as the negative electrode, or the metal foil may be attached to the current collector to form the negative electrode. As the negative electrode active material, lithium metal-based active materials such as lithium and lithium alloys are preferred because of their large charge / discharge capacity, and lithium-based metal foil itself is preferred because it can reduce the weight of the battery.

[0053] In conventional electrodes using an organic sulfur-based active material as the electrode active material, metal foils such as aluminum foil and copper foil have been used as current collectors. In lithium-ion secondary batteries using such an electrode as the positive electrode and a lithium metal foil as the negative electrode, a lithium metal foil with a thickness of at least 100 μm must be used to obtain high cycle performance. In the electrode of the present invention, by using a porous metal current collector as the current collector, the thickness of the lithium metal foil in the negative electrode can be made thinner than when a metal foil is used as the current collector, even though the basis weight of the electrode active material is increased and the charge / discharge capacity is high. Since using a lighter negative electrode is preferable to reduce the weight of a lithium-ion secondary battery, the thickness of the lithium-based metal foil in a lithium-ion secondary battery using the electrode of the present invention as the positive electrode and a lithium-based metal foil as the negative electrode is preferably 1 μm to 200 μm, more preferably 2 μm to 100 μm, and even more preferably 3 μm to 90 μm.

[0054] [B-1-2. Nonaqueous Electrolyte] Examples of nonaqueous electrolytes include liquid electrolytes obtained by dissolving a supporting electrolyte in an organic solvent, polymer gel electrolytes obtained by dissolving a supporting electrolyte in an organic solvent and gelling it with a polymer, pure polymer electrolytes containing no organic solvent and in which the supporting electrolyte is dispersed in a polymer, inorganic solid electrolytes, etc. Liquid electrolytes are preferred because they easily penetrate into the interior of the electrode of the present invention.

[0055] Examples of supporting electrolytes used in liquid electrolytes and polymer gel electrolytes include LiPF, LiBF, LiAsF, LiCFSO, LiCFCO, LiN(CFSO), LiN(CFSO), LiN(SOF), LiC(CFSO), LiB(CFSO), LiB(CO), LiBF(CO), LiSbF, LiSiF, LiSCN, LiClO, LiCl, LiF, LiBr, LiI, LiAlF, LiAlCl, LiPOF, and derivatives thereof. The content of the electrolyte in the liquid electrolyte and polymer gel electrolyte is preferably 0.5 to 7 mol / L, and more preferably 0.8 to 1.8 mol / L.

[0056] Examples of electrolytes used for the pure polymer electrolyte include LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(SO2F)2, LiC(CF3SO2)3, LiB(CF3SO3)4, and LiB(C2O4)2.

[0057] Examples of inorganic solid electrolytes include sulfide-based solid electrolytes, oxide-based solid electrolytes, etc. The inorganic solid electrolyte may be a crystalline material or a non-crystalline (amorphous) material.

[0058] Examples of sulfide-based solid electrolytes include Li2S-P2S5-based compounds, Li2S-SiS2-based compounds, Li2S-GeS2-based compounds, Li2S-B2S3-based compounds, Li2S-P2S3-based compounds, LiI-Si2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 10 GeP2S 12 The term "sulfide-based solid electrolyte" is used as a general term for solid electrolytes that primarily contain raw materials such as "LiS" and "P2S5" as described before "sulfide-based compound." For example, LiS-P2S5-based compounds include solid electrolytes that contain LiS and P2S5 and also contain other raw materials. LiS-P2S5-based compounds also include solid electrolytes with different mixing ratios of LiS and P2S5.

[0059] Examples of Li2S-P2S5-based compounds include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, and Li2S-P2S5-Z m S n (Z is Ge, Zn or Ga, and m and n are positive numbers).

[0060] Li2S-SiS2-based compounds include Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li2SO4, and Li2S-SiS2-Li x MO y (M is P, Si, Ge, B, Al, Ga, or In; x and y are positive numbers).

[0061] Examples of Li2S-GeS2 based compounds include Li2S-GeS2 and Li2S-GeS2-P2S5.

[0062] Examples of oxide-based solid electrolytes include perovskite-type oxides, Nasicon-type oxides, Lisicon-type oxides, garnet-type oxides, and β-alumina oxides.

[0063] Examples of perovskite oxides include Li a La 1-a Li-La-Ti perovskite oxides, such as TiO3, Li b La 1-b Li-La-Ta perovskite oxides, such as LiTaO3, c La 1-c Examples include Li-La-Nb perovskite oxides expressed as NbO3 (0<a<1, 0<b<1, 0<c<1).

[0064] Examples of Nasicon-type oxides include Li d+l Al d Ti 2-dLi with a crystal structure of (PO4)3 as the main crystal e X f Y g P h O j (X is B, Al, Ga, In, C, Si, Ge, Sn, Sb, or Se; Y is Ti, Zr, Ge, In, Ga, Sn, or Al; 0≦d≦1, e, f, g, p, h, and j are positive numbers). A specific example is LiTi2(PO4)3.

[0065] Examples of the silicon-type oxide include oxides represented by Li4XO4-Li3YO4 (X is Si, Ge, or Ti, and Y is P, As, or V).

[0066] Examples of garnet-type oxides include Li7La3Zr2O 12 Li-La-Zr oxides and their derivatives, as typified by the following compounds, are also included.

[0067] Examples of organic solvents used in the liquid electrolyte and polymer gel electrolyte include saturated cyclic carbonate compounds, saturated cyclic ester compounds, sulfoxide compounds, sulfone compounds, amide compounds, saturated chain carbonate compounds, chain ether compounds, cyclic ether compounds, and saturated chain ester compounds.

[0068] Examples of saturated cyclic carbonate compounds include ethylene carbonate, 1,2-propylene carbonate, 1,3-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, and 1,1-dimethylethylene carbonate.

[0069] Examples of the saturated cyclic ester compounds include γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-hexanolactone, δ-octanolactone, etc. Examples of the sulfoxide compounds include dimethyl sulfoxide, diethyl sulfoxide, dipropyl sulfoxide, diphenyl sulfoxide, thiophene, etc.

[0070] Examples of the sulfone compound include dimethyl sulfone, diethyl sulfone, dipropyl sulfone, diphenyl sulfone, sulfolane (also called tetramethylene sulfone), 3-methyl sulfolane, 3,4-dimethyl sulfolane, 3,4-diphenylmethyl sulfolane, sulfolene, 3-methyl sulfolene, 3-ethyl sulfolene, and 3-bromomethyl sulfolene, and sulfolane and tetramethyl sulfolane are preferred.

[0071] Examples of the saturated chain carbonate compound include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl butyl carbonate, methyl t-butyl carbonate, diisopropyl carbonate, and t-butyl propyl carbonate.

[0072] Examples of the chain ether compound or cyclic ether compound include glymes such as dimethoxyethane, ethoxymethoxyethane, diethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; tetrahydrofuran, dioxolane, dioxane, 1,2-bis(methoxycarbonyloxy)ethane, 1,2-bis(ethoxycarbonyloxy)ethane, 1,2-bis(ethoxycarbonyloxy)propane, ethylene glycol bis(trifluoroethyl)ether, propylene glycol bis(trifluoroethyl)ether, ethylene glycol bis(trifluoromethyl)ether, and diethylene glycol bis(trifluoroethyl)ether.

[0073] The saturated chain ester compound is preferably a monoester compound or a diester compound having 2 to 8 carbon atoms in total in the molecule, and specific examples of the compound include methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, methyl malonate, ethyl malonate, methyl succinate, ethyl succinate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethylene glycol diacetyl, and propylene glycol diacetyl.

[0074] Other organic solvents that can be used to prepare the non-aqueous electrolyte include acetonitrile, propionitrile, nitromethane, derivatives thereof, and various ionic liquids.

[0075] Examples of polymers used in the polymer gel electrolyte include polyethylene oxide, polypropylene oxide, polyvinyl chloride, polyacrylonitrile, polymethyl methacrylate, polyethylene, polyvinylidene fluoride, and polyhexafluoropropylene.

[0076] Examples of fluororesins, which are polymer-based solid electrolytes, include polymers containing vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, and derivatives thereof as structural units. Specific examples include homopolymers such as polyvinylidene fluoride, polyhexafluoropropylene, and polytetrafluoroethylene; and copolymers of vinylidene fluoride and hexafluoropropylene.

[0077] The polymer-based solid electrolyte may contain a supporting electrolyte (salt). Examples of the supporting electrolyte include salts containing lithium ions. Specific examples of the supporting electrolyte include those commonly used in the field of the present invention, such as LiClO, LiBF, LiPF, LiAlCl, LiSbF, LiSCN, LiCFSO, LiCFCO, LiAsF, and LiB. 10 Cl 10 , lower aliphatic lithium carboxylates, LiCl, LiBr, LiI, LiBCl4, borates, imide salts, etc.

[0078] As a complex hydride solid electrolyte, Li(CB9H 10 ), Li(CB 11 H 12 ), Li2(B 12 H 12 ), Li(BH4), LiBH4-LiI, Li(NH2), Li(AlH4), Li3(AlH6), LiBH4-Li(NH2), Li(BH4)-Li(NH2), Li(CB9H 10 )-Li(CB 11 H 12 ), Li(BH4)-KI, Li(BH4)-P2I4, ​​Li(BH4)-P2S5, Li2(NH2), Li(BH4)-GdCl3, Li(BH4)-NaI, Li(BH4)-Li(NH2), etc.

[0079] The phosphoric acid-based solid electrolytes include Li3PO4, LiPON, and Li 2.9 P.O. 3.3 N 0.46 Examples of organic molecular crystal solid electrolytes include Li{N(SO2F)2}-NCCH2CH2CN.

[0080] The particle diameter of the solid electrolyte is set to the average particle diameter (D 50 ) is preferably 0.1 μm to 50.0 μm.

[0081] [B-1-3. Separator] When the nonaqueous electrolyte of a nonaqueous electrolyte secondary battery is a liquid electrolyte, it is preferable to interpose a separator between the positive electrode and the negative electrode to prevent short circuits. As the separator, microporous polymer films, nonwoven fabrics, and the like commonly used in nonaqueous electrolyte secondary batteries can be used without particular limitation. Examples of films include films made of polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene chloride, polyacrylonitrile, polyacrylamide, polytetrafluoroethylene, polysulfone, polyethersulfone, polycarbonate, polyamide, polyimide, polyethers such as polyethylene oxide and polypropylene oxide, various celluloses such as carboxymethyl cellulose and hydroxypropyl cellulose, polymer compounds mainly composed of poly(meth)acrylic acid and various esters thereof, derivatives thereof, copolymers or mixtures thereof, and the like. These films may be coated with ceramic materials such as alumina and silica, magnesium oxide, aramid resin, or polyvinylidene fluoride.

[0082] When a polymer gel electrolyte, a pure polymer electrolyte, or an inorganic solid electrolyte is used as the non-aqueous electrolyte, a separator may not be included.

[0083] [B-2. Lithium-ion secondary battery (negative electrode)] Next, the case where the electrode of the present invention is used as the negative electrode of a lithium-ion secondary battery will be described. Note that when the electrode of the present invention is used as the positive electrode of a lithium-ion secondary battery, a pre-doping treatment with lithium is performed, but when it is used as the negative electrode, this is not necessary.

[0084] [B-2-1. Positive Electrode] When the electrode of the present invention is used as the negative electrode of a lithium ion secondary battery, examples of the positive electrode active material include lithium transition metal composite oxides, lithium-containing transition metal phosphate compounds, and lithium-containing silicate compounds.

[0085] The transition metal of the lithium transition metal composite oxide is preferably vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, etc. Specific examples of the lithium transition metal composite oxide include lithium cobalt composite oxides such as LiCoO2, lithium nickel composite oxides such as LiNiO2, lithium manganese composite oxides such as LiMnO2, LiMn2O4, and Li2MnO3, and lithium transition metal composite oxides in which a portion of the main transition metal atoms of these lithium transition metal composite oxides has been substituted with other metals such as aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, lithium, nickel, copper, zinc, magnesium, gallium, and zirconium. Specific examples of the lithium transition metal composite oxide in which a portion of the main transition metal atoms has been substituted with other metals include Li, 1.1 Mn 1.8 Mg 0.1 O4, Li 1.1 Mn 1.85 Al 0.05 O4, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.5 Mn 0.5 O2, LiNi 0.80 Co 0.17 Al 0.03 O2, LiNi 0.8 0Co 0.15 Al 0.05 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiMn 1.8 Al 0.2 O4, LiNi 0.5 Mn 1.5 O4, Li2MnO3-LiMO2 (M=Co, Ni, Mn), etc.

[0086] The transition metal of the lithium-containing transition metal phosphate compound is preferably vanadium, titanium, manganese, iron, cobalt, nickel, or the like. Specific examples include LiFePO4, LiMn xFe 1-x Examples of the lithium-containing silicate compounds include iron phosphate compounds such as PO4 (0<x<1), iron sulfate compounds such as LiFeSO4, cobalt phosphate compounds such as LiCoPO4, lithium transition metal phosphate compounds in which some of the main transition metal atoms are substituted with other metals such as aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, lithium, nickel, copper, zinc, magnesium, gallium, zirconium, and niobium, and vanadium phosphate compounds such as Li3V2(PO4)3. Examples of the lithium-containing silicate compounds include Li2FeSiO4.

[0087] [B-2-2. Nonaqueous Electrolyte] When the electrode of the present invention is used as the negative electrode of a lithium ion secondary battery, examples of the nonaqueous electrolyte include the nonaqueous electrolytes described in the section [B-1-2. Nonaqueous Electrolyte].

[0088] [B-2-3. Separator] When the electrode of the present invention is used as the negative electrode of a lithium ion secondary battery, examples of the separator include those described in the section [B-1-3. Separator].

[0089] [B-3. Sodium ion secondary battery (positive electrode)] The electrode of the present invention will be described when used as the positive electrode of a sodium ion secondary battery. Since the organic sulfur-based active material, which is the electrode active material of the electrode of the present invention, does not contain sodium, if the negative electrode active material of the negative electrode does not contain sodium, a pre-doping process for inserting sodium metal into the positive electrode of the present invention is required, and even if the negative electrode active material contains sodium, it is preferable to pre-dope sodium in order to stably start the secondary battery. The method of pre-doping sodium into the electrode of the present invention can be carried out by replacing lithium metal with sodium metal in the lithium doping method described in the section [B-1. Lithium ion secondary battery (positive electrode)].

[0090] Examples of the negative electrode active material for the negative electrode include natural graphite, artificial graphite, non-graphitizable carbon, easily graphitizable carbon, sodium, sodium alloy, silicon, silicon alloy, silicon oxide, tin, tin alloy, tin oxide, phosphorus, germanium, indium, copper oxide, antimony sulfide, titanium oxide, iron oxide, manganese oxide, cobalt oxide, nickel oxide, lead oxide, ruthenium oxide, tungsten oxide, zinc oxide, as well as NaVO, NaVO, NaTiO. 12 and other composite oxides.

[0091] The conductive additive, binder, and solvent for the negative electrode may be the same as those exemplified in [A-3. Slurry]. The method for preparing the slurry, the method for applying the slurry to the current collector, and the method for drying may also be the same as those exemplified in [A-3. Slurry]. The current collector may be the same as those described in [B-1-1. Negative electrode].

[0092] The nonaqueous electrolyte may be a nonaqueous electrolyte exemplified in Section [B-1-2. Nonaqueous electrolyte] in which the lithium atoms are replaced with sodium atoms. The separator may be a separator described in Section [B-1-3. Separator].

[0093] [B-4. Sodium ion secondary battery (negative electrode)] Next, the case where the electrode of the present invention is used as the negative electrode of a sodium ion secondary battery will be described. Note that, when the electrode of the present invention is used as the positive electrode of a sodium ion secondary battery, a pre-doping treatment with sodium is performed, but when it is used as the negative electrode, this is not necessary.

[0094] Examples of the positive electrode active material for the positive electrode include the positive electrode active material in which the lithium atoms of the positive electrode active material for the lithium ion battery exemplified in the section [B-2-1. Positive Electrode] are replaced with sodium atoms.

[0095] The conductive additive, binder, and solvent for the positive electrode may be the same as those exemplified in [A-3. Slurry]. The method for preparing the slurry, the method for applying the slurry to the current collector, and the method for drying may also be the same as those exemplified in [A-3. Slurry]. The current collector may be the same as those described in [B-1-1. Negative electrode].

[0096] The nonaqueous electrolyte may be the nonaqueous electrolyte exemplified in Section [B-1-2. Nonaqueous electrolyte] in which the lithium atoms are replaced with sodium atoms. The separator may be the separator described in Section [B-1-3. Separator].

[0097] [B-5. Shape of Non-Aqueous Electrolyte Secondary Battery] The shape of the non-aqueous electrolyte secondary battery using the electrode of the present invention is not particularly limited, and batteries of various shapes such as coin-shaped batteries, cylindrical batteries, prismatic batteries, and laminated batteries can be used, and a metal container or laminate film can be used as the external packaging member. The thickness of the external packaging member is usually 0.5 mm or less, preferably 0.3 mm or less. Examples of the shape of the external packaging member include flat (thin), prismatic, cylindrical, coin, and button types.

[0098] Examples of metal containers include those made of stainless steel, aluminum, or aluminum alloys. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, or silicon. By keeping the content of transition metals such as iron, copper, nickel, or chromium in aluminum or aluminum alloys to 1% or less, long-term reliability and heat dissipation performance in high-temperature environments can be dramatically improved.

[0099] The laminate film can be a multilayer film having a metal layer between resin films. The metal layer is preferably aluminum foil or aluminum alloy foil for weight reduction. The resin film can be made of a polymer material such as polypropylene, polyethylene, nylon, or polyethylene terephthalate. The laminate film can be sealed by heat fusion to form an exterior component.

[0100] 1 to 3 show an example of a laminated non-aqueous electrolyte secondary battery using the electrode of the present invention. FIG. 1 is an exploded perspective view schematically showing an electrode group 6 of a laminated non-aqueous electrolyte secondary battery 9. In the examples described below, a laminated non-aqueous electrolyte secondary battery will be used for explanation, but the present invention is not limited thereto. The electrode group 6 has a structure in which, for example, a sheet-like positive electrode 1, a sheet-like negative electrode 2, and a sheet-like separator 5 separating the positive electrode 1 and the negative electrode 2 are alternately stacked. 3 is a positive electrode terminal, and 4 is a negative electrode terminal.

[0101] Fig. 2 is an exploded perspective view showing a laminated nonaqueous electrolyte secondary battery 9, and Fig. 3 is an external plan view showing a laminated nonaqueous electrolyte secondary battery 9. 3 denotes a positive electrode terminal, 4 denotes a negative electrode terminal, 6 denotes an electrode group, 7 denotes a case-side laminate film, and 8 denotes a lid-side laminate film.

[0102] [C. Organic sulfur-based active material] Next, the organic sulfur-based active material of the present invention will be described. The organic sulfur-based active material of the present invention is an organic sulfur-based active material characterized by being used for manufacturing an electrode using a porous metal current collector as a current collector. The details of such an organic sulfur-based active material can be the same as those described in the section [A-2. Organic sulfur-based active material] above, and therefore, further description here will be omitted.

[0103] The porous metal current collector in which the organic sulfur-based active material of the present invention is used can be the same as that described in the section [A-1. Current Collector] above, and therefore further description thereof will be omitted here.

[0104] The organic sulfur-based active material of the present invention may be used as an electrode active material for an electrode using a porous metal current collector as a current collector, and may be used to form an electrode, preferably for forming a positive electrode of a nonaqueous electrolyte secondary battery or a negative electrode of a nonaqueous electrolyte secondary battery, particularly preferably for forming a positive electrode of an alkali metal ion secondary battery or a negative electrode of an alkali metal ion secondary battery, and particularly preferably for forming a positive electrode of a lithium ion secondary battery or a negative electrode of a lithium ion secondary battery. This is because, by using the organic sulfur-based active material of the present invention as an electrode active material for an electrode using a porous metal current collector as a current collector, a nonaqueous electrolyte secondary battery with excellent cycle characteristics can be provided, even if the basis weight of the organic sulfur-based active material is increased to increase the charge / discharge capacity of the electrode. In particular, when the organic sulfur-based active material of the present invention is used to form the positive electrode of a lithium ion secondary battery, in a lithium ion secondary battery using a lithium metal foil as the negative electrode, the thickness of the lithium metal foil can be made thinner, even though the basis weight of the organic sulfur-based active material of the positive electrode is larger, compared to when the organic sulfur-based active material is used to form a metal foil current collector.

[0105] <Others> The present disclosure includes the following aspects: [1] An electrode for a non-aqueous electrolyte secondary battery, comprising a current collector containing a porous metal and an organic sulfur-based active material.

[0106] [2] The electrode for a non-aqueous electrolyte secondary battery according to [1], wherein the porous metal contains aluminum.

[0107] [3] The electrode for a non-aqueous electrolyte secondary battery according to [1] or [2], wherein the porosity of the current collector containing the porous metal is 80% to 99%.

[0108] [4] The electrode for a non-aqueous electrolyte secondary battery according to any one of [1] to [3], wherein the average inner diameter of the pores in the porous metal current collector is 50 μm to 1000 μm.

[0109] [5] The electrode for a non-aqueous electrolyte secondary battery according to any one of [1] to [4], wherein the organic sulfur-based active material is sulfur-modified polyacrylonitrile.

[0110] [6] The weight per unit area of ​​the organic sulfur-based active material is 15 mg / cm 2 ~50 mg / cm2 The electrode for a non-aqueous electrolyte secondary battery according to any one of [1] to [5],

[0111] [7] A non-aqueous electrolyte secondary battery comprising a positive electrode formed from the electrode for a non-aqueous electrolyte secondary battery according to any one of [1] to [6], a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte.

[0112] [8] The nonaqueous electrolyte secondary battery according to [7], wherein the negative electrode active material of the negative electrode contains a lithium-based metal.

[0113] [9] The nonaqueous electrolyte secondary battery according to [7], wherein the negative electrode is made of a lithium-based metal foil.

[0114]

[10] A non-aqueous electrolyte secondary battery comprising a positive electrode containing a positive electrode active material, a negative electrode formed of the electrode for a non-aqueous electrolyte secondary battery according to any one of [1] to [6], and a non-aqueous electrolyte.

[0115]

[11] An organic sulfur-based active material for producing an electrode for a non-aqueous electrolyte secondary battery, the electrode comprising a current collector containing a porous metal.

[0116]

[12] The organic sulfur-based active material according to

[11] , wherein the organic sulfur-based active material is sulfur-modified polyacrylonitrile.

[0117] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to the following examples. In the examples, "parts" and "%" are by mass unless otherwise specified. The sulfur content was calculated from the analysis results using a CHN analyzer capable of analyzing sulfur and oxygen.

[0118] [Production Example 1] Sulfur-modified polyacrylonitrile was produced using a method similar to the production example described in JP 2013-054957 A. Specifically, 20 g of the raw material PAN mixture was placed in a bottomed cylindrical glass tube with an outer diameter of 45 mm and a length of 120 mm, and a silicone stopper with a gas inlet tube and a gas outlet tube was attached to the opening of the glass tube. After the air inside the glass tube was replaced with nitrogen, the lower part of the glass tube was placed in a crucible-type electric furnace, and heated at 400 °C for 1.5 hours while introducing nitrogen through the gas inlet tube to remove the generated hydrogen sulfide. The sulfur vapor condensed and refluxed at the top or lid of the glass tube. The obtained intermediate product was heated at 260 °C under atmospheric pressure under a nitrogen stream for 20 hours to remove sulfur. The obtained sulfur-modified product was pulverized using a ball mill for 30 hours and then classified through a sieve to obtain an organic sulfur-based active material A1 (sulfur-modified polyacrylonitrile) with an average particle size of 10 μm. The sulfur content of A1 is 48% by mass.

[0119] [Production Example 2] 90 parts by mass of organic sulfur-based active material A1 as the active material, 5.0 parts by mass of acetylene black (manufactured by Denka Co., Ltd.) as the conductive aid, 3.0 parts by mass (solid content) of styrene-butadiene rubber (40% by mass aqueous dispersion, manufactured by Zeon Corporation) as the binder, and 2.0 parts by mass of sodium carboxymethyl cellulose (manufactured by Daicel FineChem Co., Ltd.) were added to 130 parts by mass of water, and these were mixed for 30 minutes using a rotation / revolution mixer under conditions of revolution of 1600 rpm and rotation of 640 rpm to prepare slurry B1.

[0120] [Production Example 3] 50 parts by weight of sulfur powder (manufactured by Sigma-Aldrich, average particle size 200 μm) and 50 parts by weight of Ketjen Black (manufactured by Lion Specialty Chemicals Co., Ltd.) were mixed and heated for 1 hour at 155 ° C. under a nitrogen stream to obtain a sulfur-Ketjen Black composite (SKB). As the active material, 90 parts by weight of SKB, as a conductive additive, 5 parts by weight of acetylene black (manufactured by Denka Co., Ltd.), as a binder, 3.0 parts by weight (solids) of styrene-butadiene rubber (40% by weight aqueous dispersion, manufactured by Zeon Corporation) and 2.0 parts by weight of sodium carboxymethylcellulose (manufactured by Daicel FineChem Co., Ltd.) were added to water, and these were mixed for 30 minutes using a rotation / revolution mixer under conditions of 1600 rpm revolution and 640 rpm rotation to prepare slurry B2.

[0121] [Example 1] An aluminum porous metal current collector (manufactured by Sumitomo Electric Industries, Ltd., product name Aluminum Celmet) having a thickness of 1 mm, a porosity of 96%, and an average inner diameter of 550 μm was immersed in slurry B1, and then the porous metal current collector was removed and allowed to stand for 1 hour to dry at 80° C. The dried porous metal current collector was press-molded to a thickness of 570 μm, cut to a predetermined size, and further vacuum-dried at 150° C. for 5 hours immediately before use to obtain a porous metal current collector having an organic sulfur-based active material weight of 25 mg / cm. 2 (50 mg / cm on both sides 2 ) Example 1 electrode was prepared.

[0122] Comparative Example 1 The same procedure as in Example 1 was carried out except that the slurry B1 in Example 1 was changed to the slurry B2. 2 (50 mg / cm on both sides 2 ) An electrode of Comparative Example 1 was prepared.

[0123] [Comparative Example 2] A carbon-coated aluminum foil having a thickness of 15 μm was used as a current collector, and the weight of the organic sulfur-based active material was 5.0 mg / cm 2 (10 mg / cm on both sides 2The amount of slurry B1 applied was adjusted so that the thickness of the current collector was 1 / 3 of the total thickness of the electrode, and the slurry B1 was applied to both sides of the current collector by the comma coating method and allowed to stand for 1 hour at 80° C. to dry. The current collector was then press-molded, cut to a predetermined size, and further vacuum-dried at 150° C. for 5 hours immediately before use to prepare an electrode of Comparative Example 2.

[0124] [Comparative Example 3] In Comparative Example 2, the weight per unit area of ​​the organic sulfur-based active material was 7.5 mg / cm 2 (15 mg / cm on both sides 2 An electrode of Comparative Example 3 was produced in the same manner as in Comparative Example 2, except that the amount of slurry B1 applied was adjusted so that the thickness of the electrode was 1 / 3.

[0125] [Comparative Example 4] In Comparative Example 2, the weight per unit area of ​​the organic sulfur-based active material was 10 mg / cm 2 (20 mg / cm on both sides 2 An electrode of Comparative Example 4 was prepared in the same manner as in Comparative Example 2, except that the amount of slurry B1 applied was adjusted so that the thickness of the electrode was 1 / 3.

[0126] [Evaluation] The electrode active materials, current collectors, and evaluations of the appearance of the basis weight used in Example 1 and Comparative Examples 1 to 3 are shown in Table 1 below. Note that the electrode of Comparative Example 4 was not used in further tests because fine cracks were observed on the surface. In the case of a metal foil current collector, the fact that cracks occurred on the surface of the electrode when the basis weight was increased indicates that it is difficult to increase the basis weight of a metal foil current collector to the extent that it is possible to increase the basis weight of a porous metal current collector.

[0127]

[0128] [Preparation of Liquid Electrolytes] Liquid electrolyte E1 using a carbonate-based solvent and liquid electrolyte E2 using an ether-based solvent were prepared using the method described below. Of these, only liquid electrolyte E2 was used in the electrode of Comparative Example 1. The reason is as follows. Although SKB, the electrode active material of Comparative Example 1, does not contain sulfur crystals, it is known that lithium polysulfide (Li2Sx) produced by reaction with lithium ions chemically reacts with carbonate-based solvents, resulting in poor charge / discharge. On the other hand, lithium polysulfide elutes in ether-based solvents, but no chemical reaction occurs, making charge / discharge possible. For this reason, only liquid electrolyte E2 using an ether-based solvent was used in the electrode of Comparative Example 1.

[0129] [Liquid Electrolyte E1] LiPF6 was dissolved in a mixed solvent consisting of 50 vol% ethylene carbonate and 50 vol% diethyl carbonate to a concentration of 1.0 ml / L to prepare liquid electrolyte E1.

[0130] [Liquid Electrolyte E2] LiN(CF3SO2)2 was dissolved in a mixed solvent consisting of 50 vol% dioxolane and 50 vol% dimethoxyethane to a concentration of 1.0 ml / L, and 1 wt% LiNO3 was added to prepare liquid electrolyte E2.

[0131] Since the electrodes of Example 1 and Comparative Examples 1 to 3 did not have the same basis weight, they were pre-doped with lithium by the following method before being used in the test. Note that liquid electrolyte E1 was used for the electrodes of Example 1 and Comparative Examples 2 and 3 using electrode active material A1, and liquid electrolyte E2 was used for the electrode of Comparative Example 1 using electrode active material SKB.

[0132] [Pre-doping method] The electrode to be pre-doped was used as the positive electrode, and a lithium metal foil (thickness 500 μm) was used as the negative electrode. A polypropylene separator having a microporous membrane (manufactured by Celgard, thickness 15 μm, product name: Celgard 2325) was sandwiched between the negative electrodes on both sides of the positive electrode, and a positive electrode terminal and a negative electrode terminal were provided on the positive electrode and the negative electrode, respectively. The case was housed in a laminate film, and the liquid electrolyte was injected and then sealed. Thereafter, the case was placed in a thermostatic chamber at 25 ° C., and the discharge end voltage was set to 1.0 V, and discharge was performed once under the conditions of a discharge rate of 0.1 C, and pre-doping was performed on the positive electrode. After pre-doping, the positive electrode was removed, washed with dimethyl carbonate, and air-dried to prepare a pre-doped electrode.

[0133] Laminate-type nonaqueous electrolyte secondary batteries of Examples 2 to 5 and Comparative Examples 5 to 9 were fabricated using the pre-doped electrode as the positive electrode, a 50 μm or 300 μm thick lithium metal foil as the negative electrode, and liquid electrolytes E1 and E2 in the combinations shown in Table 2. The laminate-type nonaqueous electrolyte secondary batteries are shown in the schematic diagrams of FIGS. 1 to 3. A positive electrode 1 provided with a positive electrode terminal 3 and a negative electrode 2 provided with a negative electrode terminal 4 were stacked via a separator 5 to form an electrode group 6, and the liquid electrolyte was housed in a case consisting of a case-side laminate film 7 and a lid-side laminate film 8. The liquid electrolyte was injected and then sealed. The amount of liquid electrolyte used was 1.2 times the sum of the void volume of the positive electrode and the void volume of the separator.

[0134] The weight energy density and cycle characteristics of the nonaqueous electrolyte secondary batteries of Examples 2 to 4 and Comparative Examples 5 to 9 were evaluated by the following method. The results are shown in Table 2.

[0135] [Energy Density] The nonaqueous electrolyte secondary battery was placed in a thermostatic chamber at 25°C, and a charge / discharge test was carried out five times consecutively under the conditions of a charge cut-off voltage of 3.0 V, a discharge cut-off voltage of 1.0 V, a charge rate of 0.05 C, and a discharge rate of 0.05 C, to measure the discharge capacity. The weight energy density of the nonaqueous electrolyte secondary battery was calculated using the fifth discharge capacity, discharge voltage, and weight of the nonaqueous electrolyte secondary battery using the following formula. A higher weight energy density indicates the possibility of manufacturing a lightweight secondary battery with a large charge / discharge capacity. Weight energy density (Wh / kg) = fifth discharge capacity (Ah) × fifth discharge voltage (V) / weight of battery (kg)

[0136] [Cycle Characteristics] The nonaqueous electrolyte secondary battery that had undergone five charge / discharge tests was placed in a thermostatic chamber at 25°C, and a charge test was conducted 50 times consecutively under the conditions of a charge rate of 0.1C and a discharge rate of 0.1C, and the discharge capacity was measured. Of the total of 55 charge / discharge tests, the ratio of the discharge capacity at the 55th time to the discharge capacity at the 7th time was defined as the cycle capacity retention rate (%). A higher cycle capacity retention rate indicates better cycle characteristics.

[0137]

[0138] The secondary batteries of Examples 2 to 4, which used the electrode of the present invention as the positive electrode, all achieved higher weight energy densities and cycle capacity retention rates than the secondary batteries of the comparative examples. In Example 4 and Comparative Example 6, which used the same liquid electrolyte, the electrode current collector and the basis weight of the electrode active material were also the same, but there was a large difference due to the difference in the electrode active material. In Examples 2 and 3 and Comparative Examples 7 to 9, which used the same electrode active material and liquid electrolyte, it is believed that the large difference was due to the difference in the porous metal current collector, metal foil current collector, and basis weight of the electrode active material.

[0139] Comparative Example 8 has a higher weight energy density but a lower cycle capacity retention rate than Comparative Example 7. This is thought to be because the electrode of Comparative Example 2 used in Comparative Example 8 has a larger basis weight of the electrode active material than the electrode of Comparative Example 3 used in Comparative Example 8, which results in a larger charge / discharge capacity and a higher weight energy density, but the thicker electrode mixture layer results in greater distortion of the electrode active material due to volume changes associated with charge / discharge, resulting in a deterioration in cycle characteristics.

[0140] Reducing the weight of the battery is an effective way to increase the weight energy density. In this example, the weight energy density increased by reducing the thickness of the negative electrode from 300 μm to 50 μm. However, in the secondary batteries of Comparative Examples 5-6 and 8-9, reducing the thickness of the negative electrode reduced the cycle capacity retention rate and deteriorated the cycle characteristics. In contrast, in the secondary batteries of Examples 2-3, the cycle capacity retention rate remained almost the same even when the thickness of the negative electrode was reduced from 300 μm to 50 μm. In other words, in a lithium-ion secondary battery using a lithium-based metal foil as the negative electrode, using the electrode of the present invention as the positive electrode not only increases the charge / discharge capacity of the positive electrode and increases the weight energy density compared to a positive electrode using a metal foil current collector with an organic sulfur-based active material, but also allows the lithium-based metal foil of the negative electrode to be made thinner while maintaining good cycle characteristics, thereby further increasing the weight energy density.

[0141] In addition, a secondary battery with a higher weight energy density has a larger charge / discharge capacity than a secondary battery with a lower weight energy density, provided that the weights of the batteries are the same, and a secondary battery with the same charge / discharge capacities is lighter.

[0142] REFERENCE SIGNS LIST 1 positive electrode 2 negative electrode 3 positive electrode terminal 4 negative electrode terminal 5 separator 6 electrode group 7 case-side laminate film 8 lid-side laminate film 9 laminate-type non-aqueous electrolyte secondary battery

Claims

1. An electrode for a non-aqueous electrolyte secondary battery, comprising a current collector containing porous metal and an organic sulfur-based active material.

2. The electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the porous metal contains aluminum.

3. The electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the porosity of the current collector containing the porous metal is 80% to 99%.

4. The electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the average inner diameter of the pores of the porous metal current collector is 50 μm to 1000 μm.

5. The electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the organic sulfur-based active material is sulfur-modified polyacrylonitrile.

6. The basis weight of the organic sulfur-based active material is 15 mg / cm 2 to 50 mg / cm 2 The electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the electrode has the above properties.

7. A positive electrode comprising the electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

8. The non-aqueous electrolyte secondary battery according to claim 7, wherein the negative electrode active material of the negative electrode contains a lithium-based metal.

9. The non-aqueous electrolyte secondary battery according to claim 7, wherein the negative electrode is made of a lithium-based metal foil.

10. A positive electrode containing a positive electrode active material, a negative electrode comprising the electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, and a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte.

11. An organic sulfur-based active material for manufacturing an electrode for a non-aqueous electrolyte secondary battery, comprising a current collector containing porous metal.

12. The organic sulfur-based active material according to claim 11, wherein the organic sulfur-based active material is sulfur-modified polyacrylonitrile.