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

Technical Field

[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.

Background Art

[0002] The characteristics of a non-aqueous electrolyte secondary battery depend on its constituent members such as electrodes, separators, and electrolytes, and research and development of each constituent member are actively carried out. For an electrode, together with a binder, a current collector, etc., an electrode active material is an important constituent member, and research and development thereof are actively carried out.

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

[0004] On the other hand, regarding the current collector, a metal current collector using a metal porous body having a three-dimensional network structure is known, and in a non-aqueous electrolyte secondary battery using such a metal current collector, it is known that the active material utilization rate and the charge-discharge efficiency are improved (see, for example, Patent Documents 7 to 8).

Prior Art Documents

Patent Documents

[0006] There is a need for further improvements in the battery characteristics of non-aqueous electrolyte secondary batteries. In particular, non-aqueous electrolyte secondary batteries used in electric vehicles or hybrid vehicles require batteries that are lightweight, have a large charge / discharge capacity, and have good cycle characteristics. To increase the charge / discharge capacity of the electrodes, it is effective to increase the amount of electrode active material per unit area of ​​the electrode, also known as the basis weight. In non-aqueous electrolyte secondary batteries, multiple positive and negative electrodes are stacked on top of each other. While increasing the basis weight increases the weight of the electrodes, the increased charge / discharge capacity allows for a reduction in the number of electrodes, leading to a lighter non-aqueous electrolyte secondary battery.

[0007] In non-aqueous electrolyte secondary batteries, such as lithium-ion secondary batteries, the volume of the electrode active material increases or decreases due to the absorption or release of lithium ions during charging and discharging, causing fluctuations in the thickness of the electrode mixture layer. One of the reasons for the decrease in the battery's charge and discharge capacity is thought to be the increase in strain within the electrode mixture layer due to fluctuations in its thickness during charging and discharging. Increasing the thickness of the electrode mixture layer and thereby increasing the basis weight of the electrode active material is effective in increasing the battery's energy density, but increasing the thickness of the electrode mixture layer also increases the strain within the electrode mixture layer, making it easier for the battery's cycle characteristics to deteriorate. In particular, organic sulfur-based active materials have the problem of exhibiting larger volume changes during charging and discharging compared to other electrode active materials, making it difficult to increase their basis weight. [Means for solving the problem]

[0008] As a result of diligent research, the inventors of the present invention have discovered that by using a porous metal as a current collector, a non-aqueous electrolyte secondary battery with good cycle characteristics can be obtained even if 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 non-aqueous electrolyte secondary battery comprising a current collector containing a porous metal and an organic sulfur-based active material, a non-aqueous electrolyte secondary battery comprising said electrode, or an organic sulfur-based active material used for manufacturing said electrode. [Effects of the Invention]

[0009] By using a current collector containing a porous metal disclosed herein, the basis size of electrodes using an organic sulfur-based active material as the electrode active material can be increased, providing a non-aqueous electrolyte secondary battery with a large charge / discharge capacity and excellent cycle characteristics. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic exploded perspective view showing the electrode group 6 of a laminate-type non-aqueous electrolyte secondary battery 9. [Figure 2] Figure 2 is a schematic exploded perspective view showing a laminate-type non-aqueous electrolyte secondary battery 9. [Figure 3] Figure 3 is a schematic external view of the laminate-type non-aqueous electrolyte secondary battery 9. [Modes for carrying out the invention]

[0011] [A. Electrode for nonaqueous electrolyte secondary batteries] 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 containing a porous metal (hereinafter sometimes referred to as "porous metal current collector" or "the current collector of the present invention"). The following describes in detail each component used in the electrode of the present invention.

[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 properties, and the current collector of the present invention may contain a surface treatment 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 the following: mesh, woven fabric, nonwoven fabric, embossed material, punched material, expanded material, foam, etc. However, a current collector with a thicker thickness and higher porosity is preferred because the organic sulfur-based active material is supported in the voids of the current collector, and the basis weight of the organic sulfur-based active material can be increased. The porosity of the current collector can be calculated using the following formula. In the formula, the bulk volume of the current collector is the volume including the voids of the current collector, and specifically, it is the sum of the volume of the material of the current collector, the volume of the voids inside the current collector, and the volume of the space of the uneven parts on the surface of the current collector. The bulk volume of the current collector is measured in accordance with the density measurement method of JIS P8118 (Paper and cardboard - Test methods for thickness, density and specific volume). In addition, according to the aforementioned JIS standard, the thickness is measured by applying a pressure of 100 kPa to a pressure surface with a diameter of 16 mm using a micrometer. However, if the air gap inside the current collector of the present invention deforms, the current collector of the present invention shall be sandwiched between two metal plates of known thickness that do not deform under the measurement pressure, and the measurement shall be taken at the pressure just before the air gap deforms. The porosity of the current collector [%] = (1 - (the mass of the current collector [g] / (the bulk volume of the current collector [cm³]) 3 ] × current collector material density)) × 100

[0014] Due to its thickness and high porosity, the shape of the current collector is preferably a three-dimensional mesh structure. In this invention, a 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, nonwoven fabrics and foams are examples of three-dimensional mesh structures, and foams are preferred because they provide electrodes with physical strength even with a high porosity.

[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, as this results in good charge and discharge efficiency. In the case of secondary battery electrodes, the electrode active material is sometimes supported on the current collector and then pressed. However, the thickness of the current collector of the present invention refers to the thickness of the current collector used in the electrode, and 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 determined by the amount of organic sulfur-based active material. Ku Therefore, since electrodes with high physical strength can be obtained, a void ratio of 80% to 99% is preferred, and 90% to 99% is even more preferred. Note that the void ratio of the current collector in the present invention refers to the void ratio of the current collector used for the electrode, and not the void ratio of the current collector portion of the electrode after the pressing process.

[0017] Examples of porous metals included in the current collector of the present invention include titanium, aluminum, copper, nickel, stainless steel, and nickel-plated steel. Among these, aluminum is preferred due to its excellent conductivity and light weight, and it is more preferable that the porous metal is made of aluminum. Therefore, the current collector of the present invention is preferably a porous aluminum current collector.

[0018] A foam current collector has numerous pores, which act as gaps on which the electrode active material is supported. When the current collector of the present invention has a foam 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 becomes small. Therefore, the average inner diameter of the pores is preferably 50 μm to 1000 μm, and more preferably 100 μm to 700 μm. The average inner diameter of the pores is the average value of the opening diameter (inner diameter 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 that form the opening. 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 at each location. The cross-section of the current collector of the present invention can be measured, for example, by magnifying it with a microscope photograph.

[0019] When the shape of the current collector of the present invention is a foam, it is preferable that the pores are interconnected, as this makes it easier for a slurry containing an organic sulfur-based active material to enter and be supported within the pores. Interconnected pores are pores that are in communication with each other, with at least one pore being open. Pores that are not in communication with other pores are sometimes called independent pores. A porous metal current collector having interconnected pores and few independent 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 a method such as plating, and then decomposing and removing the foamed resin. Examples of such porous metal current collectors include Sumitomo Electric Industries' Cellmet (trade name) and Aluminum Cellmet (trade name).

[0020] [A-2. Organic sulfur active material] In this invention, an organic sulfur-based active material refers to a compound that is capable of intercalating and releasing lithium ions and can be used as an electrode active material for a secondary battery, and which has carbon atoms and sulfur atoms. Examples of organic sulfur-based active materials include those with the general formula (CS x ) m Polysulfide carbon represented by (x is between 0.5 and 2, and m is a number greater than or equal to 4), general formula (C2S y ) nExamples include organic polysulfides and heat-modified organic sulfur compounds, represented by (y being between 2.5 and 50, and n being a number greater than or equal to 2). Heat-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 include sulfur-modified polyacrylonitrile, sulfur-modified elastomer, sulfur-modified polynuclear aromatic ring compound, sulfur-modified pitch, polythienoacene compound, sulfur-modified polyether, sulfur-modified polyamide, 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% to 80% by mass. In this context, organosulfur-based active thing The sulfur content in a substance is expressed as the concentration of sulfur relative to the total amount of organic sulfur-based active material.

[0022] Sulfur-modified elastomers are compounds obtained by heat-treating natural rubber and isoprene rubber, or other rubbers, 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 elastomer is not particularly limited, but is preferably 30% to 85% by mass.

[0023] Sulfur-modified polynuclear aromatic ring compounds are obtained by heat-treating polynuclear aromatic ring compounds such as naphthalene and 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% 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, organically synthesized pitch obtained by polycondensation of condensed polycyclic aromatic hydrocarbon compounds, and organically synthesized 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 sulfur-modified pitch is not particularly limited, but is preferably 30% to 80% by mass.

[0025] Polythienosene compounds are compounds having a sulfur-containing polythienosene structure, represented by the following general formula (1).

[0026] [ka] (In the formula, * represents a bond)

[0027] Polythienoacene compounds can be obtained by heat-treating aliphatic polymer compounds having a linear structure, such as polyethylene, or polymer compounds having a thiophene structure, such as polythiophene, with elemental sulfur in a non-oxidizing atmosphere. The heat treatment temperature is not particularly limited, but it 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] Sulfur-modified polyethers are compounds obtained by heat-treating polyether compounds such as polyethylene glycol and 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% to 85% by mass.

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

[0030] Sulfur-modified aliphatic hydrocarbon oxides are compounds obtained by heat-treating aliphatic hydrocarbon oxides such as aliphatic alcohols, aliphatic aldehydes, aliphatic ketones, aliphatic epoxides, and fatty acids with elemental sulfur in a non-oxidizing atmosphere. The heat treatment temperature is not particularly limited, but 300°C to 500°C is preferred. Aliphatic hydrocarbon oxides The sulfur content is not particularly limited, but is preferably 45% to 80% by mass.

[0031] The sulfur content of organic sulfur-based active materials can be measured by elemental analysis using, for example, a CHN analyzer capable of analyzing sulfur and oxygen (such as Elementor's vario MICRO cube).

[0032] Among organic sulfur-based active materials, heat-modified organic sulfur compounds are preferred due to their large charge / discharge capacity and excellent cycle characteristics, and sulfur-modified polyacrylonitriles are even more preferred. The sulfur content of sulfur-modified polyacrylonitriles is preferably 35% to 65% by mass, and more preferably 45% to 55% by mass, due to their excellent cycle characteristics.

[0033] The particle size 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, in order to obtain excellent battery performance. The particle size is the diameter based on volume, and in this invention, the average particle size is the 50% particle size (D) measured by laser diffraction scattering. 50 ) says.

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

[0035] 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 including the electrode active material in an electrode using a metal foil as a current collector. 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 taken as half of the mass of the electrode active material contained in the electrode with respect to the area of the portion containing the electrode active material among the areas calculated from the outer shape when the electrode is viewed in plan view. This is because in an electrode using a metal foil as a current collector, only the surface containing the electrode active material can be used as an electrode, and it may be either one side or both sides, whereas in an electrode using a porous metal current collector like the electrode of the present invention, both sides of the electrode can be used. In the case where the electrode of the present invention is an electrode having a curved surface such as a wound electrode, the basis weight is calculated after deforming the curved surface portion of the electrode into a flat surface and then viewing it in plan view.

[0036] Since the electrode of the present invention uses the current collector of the present invention, it is possible to significantly increase the basis weight of the organic sulfur-based active material compared to the case of using a current collector of a metal foil, and the charge-discharge capacity of the electrode can be increased. In a non-aqueous electrolyte secondary battery, usually, a large number of positive electrodes and negative electrodes are alternately laminated to obtain high output. Since the basis weight of the active material increases in the electrode of the present invention, the weight per electrode increases, but since the charge-discharge capacity increases, the number of electrodes to be used can be reduced, and the non-aqueous electrolyte secondary battery can be made lighter.

[0037] [A-3. Slurry] As a method for manufacturing the electrode of the present invention, a method can be used in which an organic sulfur-based active material and a solvent are mixed to form a slurry, which is then applied to the current collector of the present invention. The organic sulfur-based active material may be supported on the current collector of the present invention by itself, but it is preferable to support it together with a conductive additive and a binder in order to improve conductivity and adhesion to the current collector. For this reason, when manufacturing the electrode of the present invention by applying a slurry, it is preferable to mix a conductive additive and a binder into the slurry containing the organic sulfur-based active material. In the case of an electrode, a layer containing a conductive additive, a binder, etc., in addition to the electrode active material is sometimes called the electrode mixture layer.

[0038] [A-3-1. Conductive additives] The conductive additives used in the present invention may include those known as conductive additives for electrodes, specifically 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 La2S3, S2S3, Ce2S3, and TiS2.

[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% to 15% by mass, more preferably 0.2% to 10% by mass, and even more preferably 1% to 5% by mass, relative to the mass of the electrode mixture layer, in order to improve conductivity.

[0040] [A-3-2. Binding agent] A known binder for electrodes can be used. Examples include styrene-butadiene rubber, butadiene rubber, polyethylene, polypropylene, polyamide, polyamide-imide, polyimide, polyacrylonitrile, polyurethane, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-propylene-diene rubber, fluororubber, styrene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, acrylonitrile butadiene rubber, styrene-isoprene rubber, polymethyl methacrylate, polyacrylate, polyvinyl alcohol, polyvinyl ether, carboxymethylcellulose, sodium carboxymethylcellulose, methylcellulose, cellulose nanofiber, polyethylene oxide, starch, polyvinylpyrrolidone, polyvinyl chloride, and polyacrylic acid.

[0041] As a binder, a water-based binder is preferred because it has a low environmental impact and is less likely to cause sulfur leaching. Styrene-butadiene rubber, sodium carboxymethylcellulose, and polyacrylic acid are particularly preferred. Only one binder may be used, or two or more may be used in combination.

[0042] [A-3-3. Solvent] The solvent used to prepare the slurry has moderate volatility, YesAny solvent that can disperse without reacting with sulfur-based electrode active materials, conductive additives, binders, etc. is acceptable, and examples 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, alcohol, etc. The amount of solvent used can be adjusted according to the coating method selected when coating the slurry. For example, when coating by the die coater method, the amount of solvent is preferably 10 to 300 parts by mass, and more preferably 20 to 200 parts by mass, per 100 parts by mass of the total amount of organic sulfur-based electrode active material, conductive additive, and binder.

[0043] [A-3-4. Other ingredients] The slurry may also contain other components. Examples of other components include viscosity modifiers, reinforcing agents, antioxidants, and penetration enhancers.

[0044] There are no particular limitations on the method for preparing the slurry, but examples include using a conventional ball mill, sand mill, bead mill, pigment disperser, lye crusher, ultrasonic disperser, homogenizer, rotation / revolution mixer, planetary mixer, film mixer, jet pasteor, etc.

[0045] The method for applying the slurry to the porous metal current collector is not particularly limited, and various methods such as die coating, comma coating, curtain coating, spray coating, gravure coating, flexo coating, knife coating, doctor blade, reverse roll, brush coating, and immersion can be used. When applying by immersion method, after immersing the porous metal current collector in the slurry, the gas inside the porous metal current collector may be removed by ultrasonic irradiation or reduced pressure, making 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 methods can be used, such as drying with hot air, hot air, or low-humidity air, vacuum drying, leaving it in a heating furnace, or irradiation with far-infrared rays, infrared rays, or electron beams. Through this drying, volatile components such as solvents volatilize from the slurry coating, and an electrode mixture layer is formed on the porous metal current collector. The electrode mixture layer may be formed in a single application and drying, or it may be formed by repeatedly applying and drying the slurry. In order to make the battery small and lightweight, it is preferable that the electrodes be thin, so it is preferable that the electrodes of the present invention be 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 in a non-aqueous electrolyte secondary battery. A non-aqueous electrolyte secondary battery generally consists of a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator, but the electrode of the present invention can be used as the positive electrode of a non-aqueous electrolyte secondary battery and do It may be used, and the negative electrode and do It may be used. Examples of non-aqueous electrolyte secondary batteries include alkali metal secondary batteries such as lithium-ion secondary batteries, sodium-ion secondary batteries, and potassium-ion secondary batteries. Since the non-aqueous electrolyte secondary batteries using the electrodes of the present invention can be obtained with large charge / discharge capacity and excellent cycle characteristics, lithium-ion secondary batteries and sodium-ion secondary batteries are preferred, and lithium-ion secondary batteries are particularly preferred.

[0048] [B-1. Lithium-ion secondary battery (positive electrode)] First, we will describe the case where the electrode of the present invention is used as the positive electrode of a lithium-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 lithium, if the negative electrode active material (negative electrode active material) does not contain lithium, a pre-doping treatment in which lithium metal is inserted into the positive electrode of the present invention is necessary. Even if the negative electrode active material contains lithium, it is preferable to pre-dop with lithium in order to stably start the secondary battery. Methods for pre-doping lithium into the electrode of the present invention include the electrolytic doping method, in which a half-cell is assembled using metallic lithium as the counter electrode of the electrode of the present invention and lithium is electrochemically doped, and the diffusion doping method, in which metallic lithium foil is attached to the electrode of the present invention and left in a non-aqueous electrolyte, and doping is performed by utilizing the diffusion of lithium into the electrode.

[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 manufactured by known methods. For example, a negative electrode can be manufactured by applying a slurry of a compound containing a negative electrode active material, a conductive additive, and a binder in a solvent to a current collector and drying it, thereby forming an electrode mixture layer on the 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, zinc oxide, as well as LiVO2, Li2VO4, Li4Ti5O 12 Examples of composite oxides include the following.

[0051] The conductive additive, binder, and solvent exemplified in [A-3. Slurry] above can be used. The method for preparing the slurry, the method for applying the slurry to the current collector, and the drying method can also be carried out according to the methods exemplified in [A-3. Slurry] above.

[0052] In this case, the current collector can be prepared using conductive materials such as titanium, titanium alloy, aluminum, aluminum alloy, copper, nickel, stainless steel, nickel-plated steel, and carbon. The shape of the current collector can be foil-like, plate-like, or mesh-like, 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 alloy are preferred because they have a large charge / discharge capacity, and it is preferable to use the lithium-based metal foil itself as the negative electrode because it can lighten the battery.

[0053] In conventional electrodes using organic sulfur-based active materials, metal foils such as aluminum foil and copper foil have been used as current collectors. In lithium-ion secondary batteries where such electrodes are used as the positive electrode and lithium metal foil as the negative electrode, lithium metal foil with a thickness of at least 100 μm had to be used to obtain high cycle characteristics. In the electrode of the present invention, by using a porous metal current collector as the current collector, the basis weight of the electrode active material is increased, and the charge / discharge capacity is increased, but the metal foil is not used as the current collector. as The thickness of the lithium metal foil in the negative electrode can be made thinner than when using other methods. Since it is preferable to use a lighter negative electrode in order to lighten the lithium-ion secondary battery, the thickness of the lithium metal foil in a lithium-ion secondary battery in which the electrode of the present invention is used as the positive electrode and the lithium 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. Non-aqueous electrolyte] Examples of non-aqueous electrolytes include liquid electrolytes obtained by dissolving a support electrolyte in an organic solvent, polymer gel electrolytes obtained by dissolving a support electrolyte in an organic solvent and gelling it with a polymer, pure polymer electrolytes that do not contain an organic solvent and in which the support electrolyte is dispersed in a polymer, and inorganic solid electrolytes. Liquid electrolytes are preferred because the non-aqueous electrolyte can 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 LiPF6, LiBF4, LiAsF6, LiCF3SO3, LiCF3CO2, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(SO2F)2, LiC(CF3SO2)3, LiB(CF3SO3)4, LiB(C2O4)2, LiBF2(C2O4), LiSbF6, LiSiF5, LiSCN, LiClO4, LiCl, LiF, LiBr, LiI, LiAlF4, LiAlCl4, LiPO2F2, and their derivatives. The electrolyte content in liquid electrolytes and polymer gel electrolytes is preferably 0.5 to 7 mol / L, and more preferably 0.8 to 1.8 mol / L.

[0056] Examples of electrolytes used in genuine polymer electrolytes 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 and oxide-based solid electrolytes. Inorganic solid electrolytes may be crystalline materials or amorphous materials.

[0058] Examples of sulfide-based solid electrolytes include Li2S-P2S5 compounds, Li2S-SiS2 compounds, Li2S-GeS2 compounds, Li2S-B2S3 compounds, Li2S-P2S3 compounds, LiI-Si2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 10 GeP2S 12 These are some examples. The term "system compound," which refers to sulfide-based solid electrolytes, is used as a general term for solid electrolytes that mainly contain the raw materials such as "Li2S" and "P2S5" listed before "system compound." For example, Li2S-P2S5 system compounds include solid electrolytes that contain Li2S and P2S5, as well as other raw materials. Furthermore, Li2S-P2S5 system compounds also include solid electrolytes with different mixing ratios of Li2S and P2S5.

[0059] Li2S-P2S5 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 Examples include (where Z is Ge, Zn, or Ga, and m and n are positive numbers).

[0060] Li2S-SiS2 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 Examples include (where M is P, Si, Ge, B, Al, Ga, or In, and x and y are positive numbers).

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

[0062] Oxide-based solid electrolytes include perovskite oxides, nasicon oxides, lisicon oxides, and garnet-type oxides. oxides Examples include oxides such as β-alumina.

[0063] Examples of perovskite-type oxides include Li a La 1-a Li-La-Ti perovskite-type oxides, such as TiO3, Li b La 1-b Li-La-Ta perovskite-type oxides, such as TaO3, Li c La 1-c Examples include Li-La-Nb perovskite-type oxides represented as NbO3, etc. (0 <a<1、0<b<1、0<c<1)。

[0064] Examples of NASICON-type oxides include Li d+l Al d Ti 2-d Li, which has crystals as its main crystal, such as (PO4)3. e X f Y g P h O j Examples of oxides are those represented by (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 lithicone-type oxides include those represented as Li4XO4-Li3YO4 (where X is Si, Ge, or Ti, and Y is P, As, or V).

[0066] Examples of garnet-type oxides include Li7La3Zr2O 12 Examples include Li-La-Zr oxides and their derivatives, such as those listed above.

[0067] Organic solvents used in liquid electrolytes and polymer gel electrolytes 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, saturated chain ester compounds, and the like.

[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, and δ-octanolactone. Examples of the sulfoxide compounds include dimethyl sulfoxide, diethyl sulfoxide, dipropyl sulfoxide, diphenyl sulfoxide, and thiophene.

[0070] Examples of the aforementioned sulfone compounds include dimethyl sulfone, diethyl sulfone, dipropyl sulfone, diphenyl sulfone, sulfolane (also called tetramethylene sulfone), 3-methylsulfolane, 3,4-dimethylsulfolane, 3,4-diphenylmethylsulfolane, sulfolene, 3-methylsulfolene, 3-ethylsulfolene, and 3-bromomethylsulfolene, with sulfolane and tetramethylsulfolane being preferred.

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

[0072] Examples of the chain-like 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 diester compound having a total of 2 to 8 carbon atoms in the molecule. Specific examples of such compounds 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] In addition, acetonitrile, propionitrile, nitromethane and their derivatives, and various ionic liquids can also be used as organic solvents for the preparation of non-aqueous electrolytes.

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

[0076] Examples of polymeric solid electrolytes, such as fluororesins, include polymers containing vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, and their derivatives as constituent units. Specifically, these include homopolymers such as polyvinylidene fluoride, polyhexafluoropropylene, and polytetrafluoroethylene; and copolymers of vinylidene fluoride and hexafluoropropylene.

[0077] Polymer-based solid electrolytes may contain a supporting electrolyte (salt). Examples of supporting electrolytes include salts containing lithium ions. Specifically, examples include those commonly used in the field of the present invention, such as LiClO4, LiBF4, LiPF6, LiAlCl4, LiSbF6, LiSCN, LiCF3SO3, LiCF3CO2, LiAsF6, and LiB 10 Cl 10Examples include lithium lower aliphatic carboxylates, LiCl, LiBr, LiI, LiBCl4, borates, and imide salts.

[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 Examples include Li(BH4)-KI, Li(BH4)-P2I4, ​​Li(BH4)-P2S5, Li2(NH2), Li(BH4)-GdCl3, Li(BH4)-NaI, and Li(BH4)-Li(NH2).

[0079] Examples of phosphate-based solid electrolytes include Li3PO4, LiPON, and Li 2.9 PO 3.3 N 0.46 Examples include Li{N(SO2F)2}-NCCH2CH2CN, among others, as an example of an organic molecular crystalline solid electrolyte.

[0080] The particle size of solid electrolytes allows for the formation of dense layers, thus the average particle size (D 50 The particle size is preferably 0.1 μm to 50.0 μm.

[0081] [B-1-3. Separator] In the case of a non-aqueous electrolyte secondary battery where the non-aqueous electrolyte is a liquid electrolyte, it is preferable to interpose a separator between the positive and negative electrodes to prevent short circuits. As the separator, any microporous polymer film, nonwoven fabric, etc., commonly used in non-aqueous electrolyte secondary batteries can be used without particular limitation. Examples of films include polymer compounds and their derivatives mainly composed 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 carboxymethylcellulose and hydroxypropylcellulose, poly(meth)acrylic acid and its various esters, copolymers and mixtures thereof, etc. These films may be coated with ceramic materials such as alumina and silica, or with magnesium oxide, aramid resin, or polyvinylidene fluoride.

[0082] When using polymer gel electrolytes, pure polymer electrolytes, and inorganic solid electrolytes as non-aqueous electrolytes, a separator may not be included.

[0083] [B-2. Lithium-ion secondary battery (negative electrode)] Next, we will describe the case where the electrode of the present invention is used as the negative electrode of a lithium-ion secondary battery. Note that while lithium pre-doping was performed when the electrode of the present invention was used as the positive electrode of a lithium-ion secondary battery, this is unnecessary when used as the negative electrode.

[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 positive electrode active materials include lithium transition metal composite oxides, lithium-containing transition metal phosphate compounds, lithium-containing silicate compounds, and the like.

[0085] Preferred transition metals for the lithium transition metal composite oxide include vanadium, titanium, chromium, manganese, iron, cobalt, nickel, and copper. Specific examples of lithium transition metal composite oxides 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 those in which some of the main transition metal atoms are replaced with other metals such as aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, lithium, nickel, copper, zinc, magnesium, gallium, and zirconium. Specific examples of lithium transition metal composite oxides in which some of the main transition metal atoms are replaced with other metals include, for example, Li 1.1 Mn 1.8 Mg 0.1 O4, Li 1.1 Mn 1.85 Al 0.05 O4, LiSa 0.5 Co 0.2 Mn 0.3 O2, LiLiLi 0.8 Co 0.1 Mn 0.1 O2, LiLiLi 0.5 Mn 0.5 O2, LiLiLi 0.80 Co 0.17 Al 0.03 O2, LiLiLi 0.8 0Co 0.15 Al 0.05 O2, LiLiLi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.6 Co 0.2 Mn 0.2 O2, LiMn 1.8 Al 0.2 O4, LiSa 0.5 Mn 1.5 Examples include O4, Li2MnO3-LiMO2 (M=Co,Ni,Mn), etc.

[0086] The transition metals used in the lithium-containing transition metal phosphate compounds are preferably vanadium, titanium, manganese, iron, cobalt, nickel, etc., and specific examples include LiFePO4 and LiMn.x Fe 1-x Iron phosphate compounds such as FePO4(0<x<1), iron sulfate compounds such as LiFeSO4, cobalt phosphate compounds such as LiCoPO4, and these lithium Contains Those obtained by substituting part of the transition metal atoms that are the main components of the transition metal phosphate compound with other metals such as aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, lithium, nickel, copper, zinc, magnesium, gallium, zirconium, niobium, etc., and vanadium phosphate compounds such as Li3V2(PO4)3. Examples of the lithium-containing silicate compound include Li2FeSiO4.

[0087] 〔B-2-2. Non-aqueous electrolyte〕 When the electrode of the present invention is used as the negative electrode of a lithium-ion secondary battery, examples of the non-aqueous electrolyte include the non-aqueous electrolytes described in the section of 〔B-1-2. Non-aqueous 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 the separators described in the section of 〔B-1-3. Separator〕.

[0089] 〔B-3. Sodium-ion secondary battery (positive electrode)〕 The case where the electrode of the present invention is used as the positive electrode of a sodium-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 sodium, when the negative electrode active material of the negative electrode does not contain sodium, a pre-doping treatment of inserting sodium metal into the positive electrode of the present invention is required. Even when the negative electrode active material contains sodium, it is preferable to pre-dope sodium in order to start the secondary battery stably. The method of pre-doping sodium into the electrode of the present invention is 、〔 It may be carried out by replacing lithium metal with sodium metal in the lithium doping method described in the section of B-1. Lithium-ion secondary battery (positive electrode).

[0090] Examples of negative electrode active materials include natural graphite, artificial graphite, non-graphitizable carbon, easily graphitizable carbon, sodium, sodium 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, zinc oxide, as well as NaVO2, Na2VO4, Na4Ti5O 12 Examples of composite oxides include the following.

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

[0092] Non-aqueous electrolytes are non-aqueous electrolytes in which the lithium atoms are replaced with sodium atoms, as exemplified in section [B-1-2. Non-aqueous electrolytes]. Solution Quality can be used. The separator can be one of the separators described in section [B-1-3. Separator] above.

[0093] [B-4. Sodium-ion secondary battery (negative electrode)] Next, we will describe the case where the electrode of the present invention is used as the negative electrode of a sodium-ion secondary battery. Note that while sodium pre-doping was performed when the electrode of the present invention was used as the positive electrode of a sodium-ion secondary battery, this is unnecessary when used as the negative electrode.

[0094] Examples of positive electrode active materials include those obtained by replacing the lithium atoms with sodium atoms in the positive electrode active material of a lithium-ion battery as exemplified in section [B-2-1. Positive Electrode] above.

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

[0096] For the non-aqueous electrolyte, you can use a non-aqueous electrolyte in which the lithium atoms of the non-aqueous electrolyte exemplified in section [B-1-2. Non-aqueous electrolyte] are replaced with sodium atoms. For the separator, you can use the separator described in section [B-1-3. Separator] above.

[0097] [B-5. Shape of a non-aqueous electrolyte secondary battery] The shape of the non-aqueous electrolyte secondary battery using the electrodes of the present invention is not particularly limited, and can be a variety of shapes such as coin-type batteries, cylindrical batteries, prismatic batteries, laminated batteries, etc., and a metal container or laminated film can be used as the external packaging material. The thickness of the external packaging material is usually 0.5 mm or less, preferably 0.3 mm or less. Examples of external packaging material shapes include flat (thin), prismatic, cylindrical, coin-type, button-type, etc.

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

[0099] The laminate film can be a multilayer film having a metal layer between resin films. For weight reduction, aluminum foil or aluminum alloy foil is preferred for the metal layer. The resin film can be, for example, 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] Figures 1 to 3 show an example of a laminate-type non-aqueous electrolyte secondary battery using the electrodes of the present invention. Figure 1 is a schematic exploded perspective view showing the electrode group 6 of a laminate-type non-aqueous electrolyte secondary battery 9. In the embodiments described later, a laminate-type 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-shaped positive electrode 1, a sheet-shaped negative electrode 2, and a sheet-shaped separator 5 that separates the positive electrode 1 and the negative electrode 2 are alternately stacked. 3 is the positive electrode terminal, and 4 is the negative electrode terminal.

[0101] Figure 2 is a schematic exploded perspective view of the laminate-type non-aqueous electrolyte secondary battery 9, and Figure 3 is a schematic plan view of the laminate-type non-aqueous electrolyte secondary battery 9. 3 is the positive electrode terminal, 4 is the negative electrode terminal, 6 is the electrode group, 7 is the case-side laminate film, and 8 is the lid-side laminate film.

[0102] [C. Organic sulfur 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 its use in the manufacture of electrodes using a porous metal current collector as the 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, so the explanation here will be omitted.

[0103] The details of the porous metal current collector using the organic sulfur-based active material of the present invention can be the same as those described in section [A-1. Current Collector] above, so a detailed explanation is omitted here.

[0104] The organic sulfur-based active material of the present invention can be used as an electrode active material for electrodes using a porous metal current collector as the current collector, and any application for electrode formation is acceptable. Preferably, it is used for forming the positive electrode or negative electrode of a non-aqueous electrolyte secondary battery, and more preferably for forming the positive electrode or negative electrode of an alkali metal ion secondary battery, and especially preferably for forming the positive electrode or negative electrode of a lithium-ion secondary battery. pond It is preferable that the organic sulfur-based active material of the present invention be used as the electrode active material of an electrode using a porous metal current collector as the current collector, so that even if the basis weight of the organic sulfur-based active material is increased in order to increase the charge and discharge capacity of the electrode, a non-aqueous electrolyte secondary battery with excellent cycle characteristics can be provided. In particular, when the organic sulfur-based active material of the present invention is used for forming the positive electrode of a lithium-ion secondary battery, in a lithium-ion secondary battery using lithium metal foil as the negative electrode, the thickness of the lithium metal foil can be reduced despite the increased basis weight of the organic sulfur-based active material in the positive electrode compared to when the organic sulfur-based active material is used for forming a metal foil current collector.

[0105] <Other> The following aspects are included in this disclosure: [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 comprises aluminum.

[0107] [3] An 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 porous metal including An electrode for a non-aqueous electrolyte secondary battery as described in any of [1] to [3], wherein the average inner diameter of the pores of the current collector is 50 μm to 1000 μm.

[0109] [5] An 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 basis weight of the organosulfur active material is 15 mg / cm³ 2 ~50 mg / cm³ 2 An electrode for a non-aqueous electrolyte secondary battery as described in any of [1] to [5].

[0111] A non-aqueous electrolyte secondary battery comprising a positive electrode consisting of electrodes for a non-aqueous electrolyte as described in any of [7][1] to [6], a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte.

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

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

[0114]

[10] A positive electrode comprising a positive electrode active material, a negative electrode comprising an electrode for a non-aqueous electrolyte secondary battery as described in any of [1] to [6], and a non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte.

[0115]

[11] Organic sulfur-based active material for manufacturing electrodes for non-aqueous electrolyte secondary batteries, including a current collector containing a porous metal.

[0116]

[12] The organosulfur-based active material according to

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

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

[0118] [Manufacturing Example 1] Sulfur-modified polyacrylonitrile was produced by a method similar to the production example described in Japanese Patent Publication No. 2013-054957. 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 having a gas inlet pipe and a gas outlet pipe was attached to the opening of the glass tube. After replacing the air inside the glass tube with nitrogen, the lower part of the glass tube was placed in a crucible-type electric furnace, and the mixture was heated at 400°C for 1.5 hours while introducing nitrogen through the gas inlet pipe 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 and a nitrogen stream for 20 hours to remove the sulfur. The obtained sulfur-modified product was pulverized using a ball mill for 30 hours, and then classified by sieving to obtain 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] [Manufacturing Example 2] As an active material, 90 parts by mass of organic sulfur-based active material A1, 5.0 parts by mass of acetylene black (manufactured by Denka Co., Ltd.) as a conductive additive, and 3.0 parts by mass (solids) of styrene-butadiene rubber (40% by mass aqueous dispersion, manufactured by Nippon Zeon Co., Ltd.) and 2.0 parts by mass of carboxymethylcellulose sodium (manufactured by Daicel Finechem Co., Ltd.) as binders were added to 130 parts by mass of water. These were mixed using a rotating / revolving mixer at revolving speeds of 1600 rpm and rotating speeds of 640 rpm for 30 minutes to prepare slurry B1.

[0120] [Manufacturing Example 3] 50 parts by mass of sulfur powder (manufactured by Sigma-Aldrich, average particle size 200 μm) and 50 parts by mass of Ketjenblack (manufactured by Lion Specialty Chemicals Co., Ltd.) were mixed and heated at 155°C for 1 hour under a nitrogen stream to obtain a sulfur-Ketjenblack composite (SKB). 90 parts by mass of SKB was used as the active material, 5 parts by mass of acetylene black (manufactured by Denka Co., Ltd.) as a conductive additive, and 3.0 parts by mass (solids) of styrene-butadiene rubber (40% by mass aqueous dispersion, manufactured by Nippon Zeon Co., Ltd.) and 2.0 parts by mass of carboxymethylcellulose sodium (manufactured by Daicel Finechem Co., Ltd.) as binders were added to water. These were then mixed using a rotation-revolution mixer at 1600 rpm orbital and 640 rpm rotational for 30 minutes to prepare slurry B2.

[0121] [Example 1] A porous aluminum current collector (manufactured by Sumitomo Electric Industries, Ltd., product name: Aluminium Cellmet) with a thickness of 1 mm, a porosity of 96%, and an average inner diameter of 550 μm was immersed in slurry B1. After immersion, the porous metal current collector was removed and allowed to stand at 80°C for 1 hour to dry. The dried porous metal current collector was press-molded to a thickness of 570 μm, cut to the specified size, and then vacuum-dried at 150°C for 5 hours immediately before use, resulting in a basis weight of 25 mg / cm³ of organic sulfur-based active material. 2 (50 mg / cm² on both sides) 2 An electrode for Example 1 of ) was fabricated.

[0122] [Comparative Example 1] In Example 1, the same procedure was followed except that slurry B1 was replaced with slurry B2, resulting in a basis weight of SKB of 25 mg / cm³. 2 (50 mg / cm² on both sides) 2 An electrode for Comparative Example 1 of ) was fabricated.

[0123] [Comparative Example 2] The current collector is made of carbon-coated 15 μm thick aluminum foil, and the basis weight of the organic sulfur-based active material is 5.0 mg / cm³. 2 (10 mg / cm² on both sides) 2The coating amount was adjusted to achieve [the specified value], and Slurry B1 was applied to both sides of the current collector by the comma coating method, followed by standing at 80 °C for 1 hour for drying. After that, it was press-molded, cut into a predetermined size, and further vacuum dried at 150 °C for 5 hours immediately before use to fabricate the electrode of Comparative Example 2.

[0124] 〔Comparative Example 3〕 In Comparative Example 2, except that the coating amount of Slurry B1 was adjusted so that the basis weight of the organic sulfur-based active material was 7.5 mg / cm 2 (15 mg / cm on both sides 2 ), the same operations as in Comparative Example 2 were performed to fabricate the electrode of Comparative Example 3.

[0125] 〔Comparative Example 4〕 In Comparative Example 2, except that the coating amount of Slurry B1 was adjusted so that the basis weight of the organic sulfur-based active material was 10 mg / cm 2 (20 mg / cm on both sides 2 ), the same operations as in Comparative Example 2 were performed to fabricate the electrode of Comparative Example 4.

[0126] 〔Evaluation〕 The evaluation of the electrode active materials, current collectors, and appearance of the basis weight used in Example 1 and Comparative Examples 1 to <000056⑧>is shown in Table 1 below. Note that, since fine cracks were observed on the surface of the electrode of Comparative Example 4, it was not used in subsequent tests. In the case of the current collector of metal foil, the occurrence of cracks on the surface of the electrode by increasing the basis weight indicates that it is more difficult to increase the basis weight for the current collector of metal foil than for the porous metal current collector.

[0127]

Table 1

[0128] 〔Preparation of Liquid Electrolyte〕 Liquid electrolyte E1 using a carbonate-based solvent and liquid electrolyte E2 using an ether-based solvent were prepared by the methods shown below. Among these, for the electrode of Comparative Example 1, only liquid electrolyte E2 was used. The reason is as follows. Although SKB, the electrode active material in Comparative Example 1, does not contain sulfur crystals, it is known that lithium polysulfide (Li2Sx), which is produced by reaction with lithium ions, chemically reacts with carbonate-based solvents, resulting in poor charge and discharge performance. On the other hand, lithium polysulfide dissolves in ether-based solvents, but no chemical reaction occurs, allowing for charge and discharge. Therefore, in the electrode of Comparative Example 1, only liquid electrolyte E2 using an ether-based solvent was used.

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

[0130] [Liquid electrolyte E2] Liquid electrolyte E2 was prepared by dissolving LiN(CF3SO2)2 to a concentration of 1.0 ml / L in a mixed solvent consisting of 50 vol% dioxolane and 50 vol% dimethoxyethane, and then adding 1 wt% LiNO3.

[0131] Since the electrodes in Example 1 and Comparative Examples 1-3 did not have the same basis weight, they were pre-doped with lithium using the following method before being used in the tests. Liquid electrolyte E1 was used for the electrodes in Example 1 and Comparative Examples 2-3, which used electrode active material A1, while liquid electrolyte E2 was used for the electrode in Comparative Example 1, which used 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 (500 μm thick) as the negative electrode. The positive electrode was sandwiched between the negative electrodes via a polypropylene separator with a microporous membrane (Celgard Co., Ltd., 15 μm thick, product name: Celgard 2325). Positive and negative electrode terminals were provided on the positive and negative electrodes, respectively. The electrodes were then housed in a case made of laminate film, injected with a liquid electrolyte, and sealed. Subsequently, the device was placed in a constant temperature bath at 25°C, and one discharge was performed under conditions of a discharge termination voltage of 1.0V and a discharge rate of 0.1C to pre-dope the positive electrode. After pre-doping, the positive electrode was removed, washed with dimethyl carbonate, and air-dried to prepare the pre-doped electrode.

[0133] Using a pre-doped electrode as the positive electrode, a lithium metal foil with a thickness of 50 μm or 300 μm as the negative electrode, and liquid electrolytes E1 and E2, the combinations shown in Table 2 were used in Example 2~ 4 Laminated non-aqueous electrolyte secondary batteries were fabricated in Comparative Examples 5 to 9. The laminated non-aqueous electrolyte secondary batteries are shown in the schematic diagrams in Figures 1 to 3. An electrode group 6, consisting of a positive electrode 1 with a positive electrode terminal 3 and a negative electrode 2 with a negative electrode terminal 4, laminated via a separator 5, and a liquid electrolyte are housed in a case made of a case-side laminate film 7 and a lid-side laminate film 8. After injecting the liquid electrolyte, the case is 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 gravimetric energy density and cycle characteristics of the non-aqueous electrolyte secondary batteries of Examples 2-4 and Comparative Examples 5-9 were evaluated using the following method. The results are shown in Table 2.

[0135] [Energy density] A non-aqueous electrolyte secondary battery was placed in a constant temperature bath at 25°C, and a charge termination voltage of 3.0V and a discharge termination voltage of 1.0V were set. Five consecutive charge-discharge tests were performed under conditions of a charge rate of 0.05C and a discharge rate of 0.05C, and the discharge capacity was measured. The gravimetric energy density of the non-aqueous electrolyte secondary battery was calculated from the discharge capacity, discharge voltage, and weight of the non-aqueous electrolyte secondary battery using the following formula. A higher gravimetric energy density indicates the potential for manufacturing a lightweight secondary battery with a large charge-discharge capacity. Gravimetric energy density (Wh / kg) = Discharge capacity after 5th discharge (Ah) × Discharge voltage after 5th discharge (V) / Weight of battery (kg)

[0136] [Cycle Characteristics] A non-aqueous electrolyte secondary battery that had undergone five charge-discharge tests was placed in a constant temperature bath at 25°C and charged at a charge rate of 0.1C and a discharge rate of 0.1C. release The discharge capacity was measured after 50 consecutive charge-discharge tests. The cycle capacity retention rate (%) was defined as the ratio of the discharge capacity after the 55th test to the discharge capacity after the 7th test out of a total of 55 charge-discharge tests. A higher cycle capacity retention rate indicates superior cycle performance.

[0137] [Table 2]

[0138] The secondary batteries of Examples 2 to 4, which use the electrode of the present invention as the positive electrode, all exhibit higher gravimetric energy density and cycle capacity retention rates than the secondary batteries of the comparative examples. In Example 4 and Comparative Example 6, where the liquid electrolyte is the same, the basis weight of the electrode current collector and electrode active material is also the same, yet a significant difference is observed due to the difference in the electrode active material. In Examples 2 to 3 and Comparative Examples 7 to 9, where the electrode active material and liquid electrolyte are the same, it is thought that the significant difference is due to the difference between the porous metal current collector and the metal foil current collector, as well as the basis weight of the electrode active material.

[0139] Comparative Example 8 has a higher gravimetric energy density than Comparative Example 7, but a lower cycle capacity retention rate. This is because the comparative example used in Comparative Example 8 was a comparative example. 3 The electrodes of the comparative example 7 Comparative example used 2Compared to the previous electrode, the larger basis weight of the electrode active material resulted in a larger charge / discharge capacity and higher gravimetric energy density. However, the increased thickness of the electrode mixture layer led to greater distortion of the electrode active material due to volume changes associated with charging and discharging, which is thought to have reduced the cycle characteristics.

[0140] To increase the gravimetric energy density, reducing the weight of the battery is effective, and in this embodiment, reducing the thickness of the negative electrode from 300 μm to 50 μm increases the gravimetric energy density. However, in the secondary batteries of Comparative Examples 5-6 and 8-9, reducing the thickness of the negative electrode lowers the cycle capacity retention rate and worsens the cycle characteristics. In contrast, in the secondary batteries of Examples 2-3, the cycle capacity retention rate remains almost the same even when the thickness of the negative electrode is reduced from 300 μm to 50 μm. In other words, in lithium-ion secondary batteries with 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 raises the gravimetric energy density compared to using a metal foil current collector electrode using an organic sulfur-based active material as the positive electrode, but also allows for further increases in gravimetric energy density by making the lithium-based metal foil of the negative electrode thinner while maintaining good cycle characteristics.

[0141] Furthermore, a secondary battery with a high gravimetric energy density indicates that, for the same weight, it has a larger charge / discharge capacity than a secondary battery with a low gravimetric energy density, and that it is lighter if the charge / discharge capacity is the same. [Explanation of symbols]

[0142] 1 positive electrode 2 negative electrode 3. Positive terminal 4 Negative terminal 5 Separators 6 electrode groups 7. Case-side laminating film 8. Laminating film for the lid 9. Laminated non-aqueous electrolyte secondary battery

Claims

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, The porous metal includes aluminum, An electrode for a non-aqueous electrolyte secondary battery, wherein the porosity of the current collector containing the porous metal is 80% to 99%.

2. The electrode for a non-aqueous electrolyte secondary battery according to Claim 1, wherein the average particle size of the organic sulfur-based active material is 0.5 μm to 30 μm.

3. 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.

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

5. The electrode for a non-aqueous electrolyte secondary battery according to claim 4, wherein the sulfur content of the sulfur-modified polyacrylonitrile is 35% by mass to 65% by mass.

6. The basis weight of the aforementioned organic sulfur-based active material is 15 mg / cm³. ２ ~50 mg / cm ２ The electrode for a non-aqueous electrolyte secondary battery according to claim 1.

7. A non-aqueous electrolyte secondary battery comprising a positive electrode consisting of electrodes 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.

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 lithium-based metal foil.

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

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