Secondary battery and liquid electrolyte

Abstract

To provide a secondary battery that does not require lithium or transition metal elements.SOLUTION: A secondary battery includes a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive electrode active material obtained by heat-treating a raw material mixture obtained by mixing the following components (A) to (D) in a non-oxidizing atmosphere, and the electrolyte is a liquid electrolyte containing a sodium salt and / or potassium salt as an electrolyte salt and a non-aqueous solvent. The component (A): ion raw material containing one or more elements selected from the group consisting of Na, K, Ca, and Mg. The component (B): carbonized material for positive electrode active material. The component (C): heavy oil. The component (D): sulfur.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a secondary battery and a liquid electrolyte used therein. [Background technology]

[0002] Demand for lithium secondary batteries has been increasing in recent years as small power sources for mobile phones and other devices, as well as medium- and large-sized power sources for electric vehicles and power storage. However, lithium, the main constituent element of the positive electrode active material in lithium secondary batteries, can only be produced profitably from salt lakes in a limited number of countries, raising concerns about supply instability and price hikes as demand for lithium secondary batteries increases. For this reason, research and development is being conducted on new positive electrode active materials for secondary batteries that can replace lithium secondary batteries.

[0003] Sodium secondary batteries are potential alternatives to lithium secondary batteries because they can use sodium compounds, which are abundant in resources, as the positive electrode active material. Various sodium transition metal composite compounds have been proposed as the positive electrode active material for sodium secondary batteries. Examples of such sodium transition metal composite compounds that have been reported include sodium iron cobalt composite metal oxide (e.g., Patent Document 1), sodium manganese cobalt nickel composite metal oxide (e.g., Patent Document 2), and sodium manganese titanium nickel composite oxide (e.g., Patent Document 3).

[0004] Furthermore, as a positive electrode active material for a sodium secondary battery other than a sodium transition metal complex compound, Patent Document 4 reports a positive electrode active material consisting of a carbon skeleton derived from a carbon source compound selected from special polycyclic aromatic hydrocarbons and sulfur (S) bonded to the carbon skeleton.

[0005] Potassium secondary batteries are also a potential alternative to sodium secondary batteries for lithium secondary batteries. Patent Document 5 reports a potassium secondary battery that uses a composite oxide containing potassium, a transition metal, and phosphorus as the positive electrode active material.

[0006] Another alternative candidate is a calcium secondary battery. Patent Document 6 discloses a calcium secondary battery that uses a calcium-cobalt composite oxide as the positive electrode active material. Patent Document 7 discloses a calcium secondary battery that uses vanadium oxide, which reacts reversibly with calcium, as the positive electrode active material.

[0007] In addition, the electrolyte solution (liquid electrolyte) used in lithium secondary batteries is widely made by dissolving an electrolyte salt made of lithium salt in a cyclic carbonate solvent (non-aqueous solvent) with a high dielectric constant. However, these solvents have flash points near room temperature, and therefore may ignite due to leakage from the battery during manufacturing or storage, or due to heat generation or explosion caused by overcharging of the battery. Therefore, flame retardants are often added to these solvents. For example, Patent Document 8 reports that a lithium secondary battery using an electrolyte solution for a lithium secondary battery, in which lithium hexafluorophosphate is used as an electrolyte salt, a cyclic carbonate is used as a non-aqueous solvent, and a specific proportion of a fluorinated phosphate ester is blended as a flame retardant, has self-extinguishing properties, and is excellent in cycle characteristics and charge / discharge characteristics of the battery.

[0008] Meanwhile, a method for producing a positive electrode active material using sulfur-containing rubbers, such as rubbers derived from tires, as a raw material has been reported (Patent Document 9). In this production method, the rubbers are thermally decomposed to separate them into a solid and a dry distillation gas, the dry distillation gas is cooled to separate it into an oil component and a gas, the oil component is distilled and separated, and the obtained sulfur and heavy oil are mixed and heat-treated to produce a product, which is used as the positive electrode active material for lithium secondary batteries. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-203565 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-229452 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-206925 [Patent Document 4] Patent No. 5737679 [Patent Document 5] Patent No. 6800322 [Patent Document 6] Japanese Patent Application Laid-Open No. 2012-248470 [Patent Document 7] Patent No. 6538835 [Patent Document 8] Patent No. 7175161 [Patent Document 9] Patent No. 6266655 Summary of the Invention [Problem to be solved by the invention]

[0010] The positive electrode active materials for sodium secondary batteries disclosed in Patent Documents 1 to 3, etc., require transition metal elements such as cobalt and nickel, which are scarce resources, while the positive electrode active material of Patent Document 4, while not containing transition metal elements, requires synthesis by bonding a special carbon skeleton with sulfur, and because the positive electrode active material itself does not contain alkali metals, a process of pre-doping alkali metal ions in the electrolyte into the positive electrode active material is necessary when using it as a battery, leaving room for improvement in terms of raw material supply, production costs, operating conditions, etc. Furthermore, while potassium secondary batteries and calcium secondary batteries have been reported in Patent Documents 5 to 7, etc., there have been few examples of their development, and candidates for useful positive electrode active materials have been sought.

[0011] Furthermore, compared to lithium secondary batteries, there are fewer examples of development of electrolytes (liquid electrolytes) for sodium secondary batteries and potassium secondary batteries, and there has been a demand for electrolytes (liquid electrolytes) suitable for sodium secondary batteries and potassium secondary batteries. Furthermore, there are few reports on calcium secondary batteries, and there has been little research into electrolytes (liquid electrolytes) suitable for calcium secondary batteries.

[0012] Furthermore, the positive electrode active material using rubber-derived raw materials in Patent Document 9 has the advantage that waste materials such as rubbers derived from waste tires can be used as the sulfur-containing raw material rubbers. However, although it exhibited excellent performance as a lithium secondary battery, it could not be directly used in secondary batteries of ions other than Li.

[0013] Under these circumstances, an object of the present invention is to provide a secondary battery that does not require lithium or transition metal elements and an electrolyte solution (liquid electrolyte) suitable for the secondary battery. [Means for solving the problem]

[0014] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that a composition obtained by heat-treating a raw material mixture obtained by mixing specific components not containing lithium under a non-oxidizing atmosphere can be used as a positive electrode active material that provides an excellent electrode for a secondary battery. In particular, when the positive electrode active material is a composition containing Ca, it can function as a secondary battery even when a sodium salt or potassium salt is used as the electrolyte salt, which led to the present invention.

[0015] That is, the present invention relates to the following inventions.

[0016] <1> A secondary battery, a positive electrode, a negative electrode, and an electrolyte; The positive electrode comprises a positive electrode active material obtained by heat-treating a raw material mixture obtained by mixing the following components (A) to (D) in a non-oxidizing atmosphere, The secondary battery, wherein the electrolyte is a liquid electrolyte containing a sodium salt and / or a potassium salt as an electrolyte salt and a fluorinated phosphate ester as a non-aqueous solvent. Component (A): An ion source containing one or more elements selected from the group consisting of Na, K, Ca, and Mg. Component (B): Carbide for positive electrode active material Component (C): Heavy oil Component (D): Sulfur <2> Component (A) is an ion source containing Ca <1> The secondary battery according to claim 1. <3> At least a part of component (A) is one or more selected from the group consisting of plant combustion ash, burned eggshells, burned seashells, gypsum, and hot spring scale. <1> or <2> The secondary battery according to claim 1. <4> At least a part of component (B) is a refined carbonized product obtained by thermally decomposing a sulfur-containing rubber to separate it into a solid and a dry distillation gas, separating an unrefined carbonized product from the solid, and heat-treating the unrefined carbonized product. <1> from <3> 1. The secondary battery according to claim 1 , <5> At least a portion of component (C) is heavy oil obtained by thermally decomposing sulfur-containing rubbers to separate them into solids and dry distillation gas, cooling the dry distillation gas to separate it into oil and gas, and distilling the oil to separate it into heavy oil, light oil, and sulfur. <1> from <4> 1. The secondary battery according to claim 1 , <6> At least a part of component (D) is sulfur obtained by thermally decomposing sulfur-containing rubbers to separate them into solids and dry distillation gas, cooling the dry distillation gas to separate it into oil and gas, and distilling the oil to separate it into heavy oil, light oil, and sulfur. <1> from <5> 1. The secondary battery according to claim 1 , <7> Component (A) is at least one selected from the group consisting of plant combustion ash, burned eggshells, burned seashells, gypsum, and hot spring scale; at least a part of component (B) is a refined carbonized product obtained by thermally decomposing a sulfur-containing rubber to separate it into a solid and a dry distillation gas, separating an unrefined carbonized product from the solid, and heat-treating the unrefined carbonized product; At least a portion of the component (C) is a heavy oil obtained by cooling the dry distillation gas to separate it into an oil component and a gas, and then distilling the oil component to separate it into a heavy oil component, a light oil component, and sulfur, At least a part of the component (D) is sulfur obtained by distilling the oil and separating it into heavy oil, light oil, and sulfur. <1> The secondary battery according to claim 1. <8> Claims in which the sulfur-containing rubbers are rubbers derived from tires <1> from <7> 10. The secondary battery according to claim 9, <9> The liquid electrolyte contains 30% by weight or more of a fluorinated phosphate ester as a non-aqueous solvent. <1> from <8> 10. The secondary battery according to claim 9, <10> The fluorinated phosphate ester is tris(2,2,2-trifluoroethyl)phosphate (TFEP). <1> from <9> 1. The secondary battery according to claim 1 , <11> The sodium salt in the liquid electrolyte is sodium bis(fluorosulfonyl)imide (NaFSI), and the potassium salt is potassium bis(fluorosulfonyl)imide (KFSI). <1> from <10> 1. The secondary battery according to claim 1 ,

[0017] <1a> A liquid electrolyte for use in a secondary battery having a positive electrode using a positive electrode active material containing Ca, A liquid electrolyte containing a sodium salt and / or a potassium salt as an electrolyte salt and a fluorinated phosphate ester as a non-aqueous solvent. <2a> The liquid electrolyte according to <1a>, wherein the positive electrode active material is a positive electrode active material obtained by heat-treating a raw material mixture obtained by mixing the following components (A) to (D) in a non-oxidizing atmosphere: Component (A): An ion source containing one or more elements selected from the group consisting of Na, K, Ca, and Mg. Component (B): Carbide for positive electrode active material Component (C): Heavy oil Component (D): Sulfur <3a> The liquid electrolyte according to <2a>, wherein the component (A) is an ion source containing Ca. <4a> The liquid electrolyte according to any one of <1a> to <3a>, wherein the liquid electrolyte contains 30% by weight or more of a fluorinated phosphate ester as a non-aqueous solvent. <5a> The liquid electrolyte according to any one of <1a> to <4a>, wherein the fluorinated phosphate ester is tris(2,2,2-trifluoroethyl)phosphate (TFEP). <6a> The liquid electrolyte according to any one of <1a> to <5a>, wherein the sodium salt in the liquid electrolyte is sodium bis(fluorosulfonyl)imide (NaFSI) and the potassium salt in the liquid electrolyte is potassium bis(fluorosulfonyl)imide (KFSI). [Effects of the Invention]

[0018] According to the present invention, a secondary battery that does not contain lithium or transition metal elements and an electrolyte solution (liquid electrolyte) suitable for the secondary battery are provided. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a conceptual diagram of a manufacturing system for an electrode member according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described in detail below using examples, etc., but the present invention is not limited to the examples below and can be practiced with any modifications within the scope of the gist of the present invention. In this specification, the symbol "to" is used as an expression including the numerical values ​​or physical quantities before and after it. In addition, in this specification, the expression "A and / or B" includes "A only," "B only," and "both A and B."

[0021] (Definition of terms) In this specification, the term "electrode member" means "a member constituting an electrode of a battery," and specifically means an electrode active material (a positive electrode active material and a negative electrode active material), a conductive material (a positive electrode conductive material and a negative electrode conductive material), and a current collector (a positive electrode current collector and a negative electrode current collector). In this specification, the term "positive electrode active material" refers to an electrode active material that is used in a positive electrode among materials involved in a reaction that generates electric energy. In addition, in this specification, the term "negative electrode active material" refers to an electrode active material that is used in a negative electrode among materials involved in a reaction that generates electric energy.

[0022] In addition, in this specification, the term "carbonized product" is a concept that encompasses not only "carbon materials consisting of pure carbon atoms" but also "materials containing carbon atoms and impurities (such as mineral components derived from carbon-containing raw materials) obtained by heat-treating carbon-containing raw materials." In this specification, the term "unrefined charcoal" refers to a charcoal separated from solids obtained by pyrolysis of a raw material that is a sulfur-containing rubber. In this specification, the term "purified charcoal" refers to a charcoal obtained by washing the unrefined charcoal and then heat-treating it in a non-acidic atmosphere. Crushing of the unrefined charcoal and the purified charcoal is optional.

[0023] <1. Secondary battery> The present invention relates to a secondary battery (hereinafter referred to as "the secondary battery of the present invention") comprising a positive electrode, a negative electrode, and an electrolyte, in which the positive electrode contains a positive electrode active material obtained by heat-treating, in a non-oxidizing atmosphere, a raw material mixture obtained by mixing the following components (A) to (D):

[0024] Component (A): An ion source containing one or more elements selected from the group consisting of Na, K, Ca, and Mg. Component (B): Carbide for positive electrode active material Component (C): Heavy oil Component (D): Sulfur

[0025] The structure of the secondary battery of the present invention is not particularly limited, and any conventionally known secondary battery structure can be adopted, such as a coin type, button type, sheet type, cylindrical type, rectangular type, or flat type, depending on the intended use.

[0026] Hereinafter, each of the components (positive electrode, negative electrode, and liquid electrolyte) of the secondary battery of the present invention will be described.

[0027] (1-1. Positive electrode) In the secondary battery of the present invention, the positive electrode has a current collector and a positive electrode active material layer formed on the surface of the current collector, and the positive electrode active material layer is formed of a positive electrode mixture (positive electrode active material, conductive material, and binder). In the positive electrode of the secondary battery of the present invention, the positive electrode active material will be described in detail in (1-1-1. Positive electrode active material), and the positive electrode mixture using the positive electrode active material will be described in detail in (1-1-2. Positive electrode mixture).

[0028] The current collector is not particularly limited and may be any conventionally known current collector, such as a foil, mesh, expanded grid (expanded metal), or punched metal made of a conductive material such as aluminum, nickel, copper, or stainless steel (SUS).

[0029] The size and thickness of the current collector are determined depending on the intended use of the battery, and an appropriate size can be selected depending on the size of the positive electrode to be used.

[0030] A typical method for producing a positive electrode involves mixing a positive electrode mixture (positive electrode active material, conductive material, and binder) with a solvent to prepare a slurry, which is then coated on a current collector, dried, and then pressed or otherwise adhered to the current collector, thereby forming a positive electrode active material layer on the surface of the current collector and obtaining a positive electrode.

[0031] Examples of the solvent for the slurry include amine-based solvents such as N,N-dimethylaminopropylamine and diethyltriamine; ether-based solvents such as ethylene oxide and tetrahydrofuran; ketone-based solvents such as methyl ethyl ketone; ester-based solvents such as methyl acetate; and aprotic polar solvents such as dimethylacetamide and N-methyl-2-pyrrolidone. The method for applying the slurry to the current collector is not limited as long as it does not impair the object of the present invention, and examples thereof include slit die coating, screen coating, curtain coating, knife coating, gravure coating, and electrostatic spraying.

[0032] (1-1-1. Positive electrode active material) The positive electrode active material used in the secondary battery of the present invention (hereinafter referred to as the "positive electrode active material of the present invention") will be described below.

[0033] The positive electrode active material of the present invention is produced by a production method (hereinafter, sometimes referred to as the "production method for the positive electrode active material of the present invention") that includes a step of heat-treating a raw material mixture obtained by mixing the following components (A) to (D) in a non-oxidizing atmosphere. Component (A): An ion source containing one or more elements selected from the group consisting of Na, K, Ca, and Mg. Component (B): Carbide for positive electrode active material Component (C): Heavy oil Component (D): Sulfur

[0034] The positive electrode active material of the present invention can be produced as follows using components (A) to (D) as starting materials: That is, the production can be carried out by carrying out the following steps (p1) and (p2) in this order. Step (p1): A step of mixing components (A) to (D) to obtain a raw material mixture Step (p2): A step of heat-treating the obtained raw material mixture in a non-oxidizing atmosphere to obtain a heat-treated product.

[0035] The positive electrode active material of the present invention can be suitably manufactured by the "electrode member manufacturing system of the present invention" described below in <2. Electrode member manufacturing method and electrode member manufacturing system>, but is not limited thereto, and the positive electrode active material manufacturing method of the present invention can also be performed using manufacturing equipment other than the "electrode member manufacturing system of the present invention."

[0036] The method for producing the positive electrode active material of the present invention will be described in detail below.

[0037] <Process (p1)> Step (p1) is a step of mixing components (A) to (D) to obtain a raw material mixture.

[0038] <Component (A)> Component (A) is an ion source containing one or more elements selected from the group consisting of Na, K, Ca, and Mg.

[0039] The ionic raw material, which is component (A), refers to a raw material that contains the target ionic species (Na, K, Ca, or Mg) and can provide the target ionic species to the positive electrode active material.

[0040] The ionic raw material (component (A)) may be one type, or two or more types may be used. When two or more types of ionic raw materials are used, the ionic species may be the same or different.

[0041] Examples of component (A) include percarbonates, carbonates, hydrogencarbonates, sulfates, and nitrates of Na, K, Ca, or Mg. Although new raw materials can be used as component (A), it is preferable to use raw materials derived from waste. As component (A), only new raw materials, only raw materials derived from waste, or a mixture of new raw materials and raw materials derived from waste (in any mixing ratio) may be used.

[0042] One suitable example of component (A) is an ion source containing Ca. In this case, new calcium salts such as calcium oxide (CaO) and calcium carbonate (CaCO3) can be used, but it is preferable to use raw materials derived from waste materials.

[0043] When component (A) is an ionic raw material containing Ca, only new raw materials may be used, only waste-derived raw materials may be used, or a mixture of new raw materials and waste-derived raw materials (in any mixing ratio) may be used.

[0044] When component (A) is an ion source containing Ca, one suitable example of component (A) is plant combustion ash (particularly wood combustion ash). "Plant combustion ash" is the combustion ash of a plant-derived raw material, and contains Na, K, Ca, and Mg (particularly Ca) derived from the plant-derived raw material, as well as other mineral components. There are no particular limitations on the plant-based raw material as long as it does not impair the object of the present invention, but from the viewpoint of waste utilization, it is preferable that it be at least one selected from rice husks, straw, bamboo, thinned wood, and weeds. One suitable example of plant combustion ash is wood combustion ash, which is the ash obtained by combustion of a woody raw material. The woody raw material is not particularly limited as long as it does not impair the object of the present invention, but typical examples include broad-leaved trees such as cedar, larch, and cypress, coniferous trees such as beech, birch, and oak, and bamboo. In addition, from the perspective of waste utilization, examples of the woody raw material include wood from demolished houses, wood waste from sawmills, wood waste from furniture factories, and tree wood.

[0045] When component (A) is an ion source containing Ca, one suitable example of component (A) is a calcined biological material containing calcium. Examples of "biological materials containing calcium" include eggshells and seashells, and calcined eggshells and seashells (main component: CaO) can be suitably used as an ion source that provides calcium.

[0046] When component (A) is an ion source containing Ca, one suitable example of component (A) is gypsum. “Gypsum” is a mineral containing calcium sulfate and is suitable as a calcium source. There are no particular limitations on the gypsum as long as it does not impair the object of the present invention, but from the viewpoint of waste utilization, gypsum produced by separating gypsum boards can be used.

[0047] When component (A) is an ionic raw material containing Ca, one suitable example of component (A) is hot spring scale. "Hot spring scale" is a component that was originally dissolved in hot spring water but has since precipitated and accumulated as an insoluble component due to changes in temperature or pressure, contact with air, contact with pipes, etc. The components of hot spring scale depend on the original hot spring water, but include at least one of calcium, sodium, potassium, and magnesium. Hot spring scale often also contains components such as silica-based minerals and iron oxide hydroxide, so these may be removed as necessary before use as component (A).

[0048] <Ingredient (B)> The carbonized product for a positive electrode active material, which is component (B), is a carbonized product used as a raw material for a positive electrode active material. Any carbon material can be used as the carbide for the positive electrode active material as long as it does not impair the object of the present invention, and examples thereof include graphite powder, carbon black (e.g., acetylene black, ketjen black, furnace black, etc.), and fibrous carbon materials (carbon nanotubes, carbon nanofibers, vapor-grown carbon fibers, etc.).

[0049] In addition, the carbonized material for the positive electrode active material is preferably a material obtained by heat-treating a carbon-containing raw material under inert conditions. The carbon-containing raw material used as the raw material for the carbonized material may be any material as long as it does not impair the object of the present invention, and examples thereof include biomass raw materials (e.g., wood, bamboo, rice husks, etc.), various resin materials, and plastics such as rubber materials. These carbon-containing raw materials may be used alone or in combination of two or more.

[0050] Component (B) preferably contains at least a portion of a refined carbide, which will be described later in <2. Manufacturing method and manufacturing system for electrode member>. That is, a suitable example of the carbonized material for the positive electrode active material, which is component (B), is a refined carbonized material obtained by thermally decomposing a rubber containing sulfur to separate it into a solid and a dry distillation gas, separating the carbonized material from the solid, and heat-treating the unrefined carbonized material.

[0051] The heat treatment conditions are appropriately determined taking into consideration the type of carbon-containing raw material and the physical properties (crystallinity, porosity, etc.) of the target carbonized product. Typically, the carbon-containing raw material is heated in a non-oxidizing atmosphere (for example, under a flow of an inert gas such as N2) to perform the carbonization treatment. The carbonization temperature is, for example, 500°C or higher and 1200°C or lower.

[0052] <Component (C)> The heavy oil, which is component (C), is an essential component of the positive electrode active material and also functions as a binder that binds the other components together during production.

[0053] As the heavy oil, any of coal tar, petroleum and rubber based oils can be used.

[0054] Component (C) preferably contains at least a portion of heavy oil, which will be explained in <2. Manufacturing method of electrode member and manufacturing system of electrode member> below. That is, a suitable example of the heavy oil that is component (C) is a heavy oil obtained by thermally decomposing rubbers containing sulfur to separate them into solids and dry distillation gas, cooling the dry distillation gas to separate it into oil and gas, and distilling the oil to separate it into heavy oil, light oil, and sulfur.

[0055] <Ingredient (D)> The sulfur as component (D) may be a commercially available product, or may be separated from a sulfur-containing compound or composition.

[0056] Component (D) preferably contains at least a portion of sulfur, which will be explained in <2. Manufacturing method and manufacturing system for electrode member> below. That is, at least a part of component (D) is sulfur obtained by thermally decomposing sulfur-containing rubbers to separate them into solids and dry distillation gas, cooling the dry distillation gas to separate it into oil and gas, and distilling the oil to separate it into heavy oil, light oil, and sulfur.

[0057] In a preferred example of the method for producing a positive electrode active material of the present invention, component (A) is one or more selected from the group consisting of plant combustion ash, burned eggshells, burned seashells, gypsum, and hot spring scale; at least a portion of component (B) is a refined carbonized product obtained by thermally decomposing sulfur-containing rubbers and separating them into solids and dry distillation gas, sorting out crude carbonized material from the solids, and heat-treating the crude carbonized material; at least a portion of component (C) is heavy oil obtained by cooling the dry distillation gas to separate it into oil and gas, and distilling the oil into heavy oil, light oil, and sulfur; and at least a portion of component (D) is sulfur obtained by distilling the oil into heavy oil, light oil, and sulfur.

[0058] The proportions of the components (A) to (D) are determined appropriately depending on the types of the components (A) to (D) within the range in which they function as a positive electrode active material. For example, when component (A) is wood combustion ash, the suitable proportions of components (A) to (D) are 20 to 60% by weight of component (A), 10 to 30% by weight of component (B), 5 to 15% by weight of component (C), and 20 to 40% by weight of component (D). Furthermore, when component (A) is baked eggshell (main component: CaO), the suitable proportions of components (A) to (D) are 35 to 70% by weight of component (A), 10 to 30% by weight of component (B), 5 to 15% by weight of component (C), and 5 to 30% by weight of component (D).

[0059] The mixing method in step (p1) may be dry mixing, which is commonly used industrially. Examples of dry mixing devices include a V-type mixer, a W-type mixer, a ribbon mixer, a drum mixer, and a dry ball mill. Furthermore, the mixing may also be performed by wet mixing, provided that the object of the present invention is not impaired.

[0060] <Process (p2)> In step (p2), the raw material mixture obtained in step (p1) is heat-treated in a non-oxidizing atmosphere to obtain a heat-treated product. In step (p2), a heat-treated product (positive electrode active material) is obtained.

[0061] In this specification, the term "non-oxidizing atmosphere" refers to an atmosphere that does not substantially contain an oxidizing gas such as oxygen, and is typically an inert gas atmosphere such as nitrogen, argon, helium, etc. Furthermore, a reducing atmosphere such as hydrogen or an inert gas containing hydrogen may also be used, provided that the object of the present invention is not impaired.

[0062] In the step (p2), the heat treatment of the raw material mixture is carried out, for example, by placing the raw material mixture in a non-oxidizing atmosphere, raising the temperature from room temperature to a heat treatment temperature, performing the heat treatment at the heat treatment temperature for a predetermined time, and then lowering the temperature to, for example, room temperature.

[0063] The heat treatment temperature and heat treatment time are appropriately set in a range that produces the desired heat-treated product (positive electrode active material) depending on the types and proportions of the components (A) to (D). The heat treatment temperature is, for example, 250° C. or higher and 500° C. or lower (preferably 300° C. or higher and 400° C. or lower). The heat treatment time is, for example, 10 minutes or higher and 10 hours or lower.

[0064] The heat-treated product obtained in step (p2) is optionally pulverized before use. The pulverization method may be any pulverization method commonly used in industry. Examples of pulverization equipment include pulverizers such as vibration mills, jet mills, and dry ball mills. Furthermore, classification operations such as air classification may be performed as necessary.

[0065] (1-1-2. Positive electrode mixture) The positive electrode mixture of the present invention contains the above-described positive electrode active material of the present invention and a conductive material.

[0066] The positive electrode active material of the present invention may increase the resistance inside the electrode if used alone to form a positive electrode, and therefore is usually used in combination with other conductive materials (and other materials as needed) to ensure electrical continuity inside the electrode.

[0067] The conductive material has the role of improving the electronic conductivity when an electrode is formed. The conductive material may be any material that has electrical conductivity (electronic conductivity) and does not impair the performance of the positive electrode active material of the present invention, and may be either an inorganic material or an organic material, but is typically a carbon-based material.

[0068] As the carbon-based material, any carbon-based material used in secondary batteries or fuel cells can be used, and more specific examples include graphite powder, carbon black (e.g., acetylene black, ketjen black, furnace black, etc.), and fibrous carbon materials (carbon nanotubes, carbon nanofibers, vapor-grown carbon fibers, etc.). Among these, carbon black is a fine particle with a large surface area, and by adding it to the positive electrode mixture, it is possible to increase the conductivity inside the resulting electrode and improve the charge / discharge efficiency and large current discharge characteristics.

[0069] The shape and size of the carbon-based material can be appropriately selected taking into consideration the intended use of the electrode, etc. When the carbon-based material is particulate, the particle size is, for example, 0.03 to 500 μm, and when it is fibrous, the diameter is, for example, 2 nm to 20 μm and the total length is about 0.03 to 500 μm.

[0070] The conductive material used in the present invention may be one type, or two or more types of conductive materials differing in size (particle size, fiber diameter, and fiber length), crystallinity, etc. may be used in any ratio.

[0071] The proportion of the conductive material in the positive electrode mixture can be appropriately selected taking into consideration the intended use of the electrode, etc., but when the conductive material is a carbon-based material, the carbon-based material in the electrode is usually 5 to 100 parts by weight per 100 parts by weight of the electrode active material.

[0072] The positive electrode mixture of the present invention may be composed only of the positive electrode active material of the present invention and the conductive material, but may also contain other components within a range that does not impair the object of the present invention.

[0073] The positive electrode mixture of the present invention may contain other positive electrode active materials in addition to the positive electrode active material of the present invention. As the other positive electrode active materials, any positive electrode active materials may be contained in any proportion as long as the object of the present invention is not impaired.

[0074] Other components that may be blended into the positive electrode mixture of the present invention include, for example, a binder. The binder acts as a binding agent to bond other electrode constituent materials. Examples of binders include binders made of organic polymer compounds, such as polysaccharides and derivatives thereof, such as methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl hydroxyethyl cellulose, and nitrocellulose; Examples include polyvinylidene fluoride (hereinafter sometimes referred to as PVDF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers, hexafluoropropylene-vinylidene fluoride copolymers, tetrafluoroethylene-perfluorovinyl ether copolymers; phenolic resins; melamine resins; polyurethane resins; urea resins; polyamide resins; polyimide resins; polyamide-imide resins; petroleum pitch; and coal pitch.

[0075] One type of binder may be used, or two or more types may be used.

[0076] The amount of binder blended as a constituent material in the electrode is, for example, usually about 0.5 to 50 parts by weight, and preferably about 1 to 30 parts by weight, per 100 parts by weight of the total of the positive electrode active material and the conductive material.

[0077] (1-2. Negative electrode) The negative electrode has a current collector and a negative electrode active material layer formed on the surface of the current collector. The negative electrode active material layer is typically formed of a negative electrode mixture containing a negative electrode active material.

[0078] Examples of the negative electrode active material include carbon materials such as natural graphite, artificial graphite, cokes, hard carbon, carbon black, pyrolytic carbons, carbon fiber, and baked organic polymer compounds. The carbon material may be in any shape, such as flakes like natural graphite, spherical like mesocarbon microbeads, fibrous like graphitized carbon fiber, or aggregates of fine powder. Here, the carbon material may also function as a conductive material.

[0079] The negative electrode active material preferably contains at least a portion of a refined carbide, which will be described later in <2. Manufacturing method and manufacturing system for electrode member>. That is, it is preferable that the negative electrode active material contains at least a portion of a purified carbonized material obtained by thermally decomposing sulfur-containing rubbers as raw materials to separate them into solids and dry distillation gas, selecting an unrefined carbonized material from the solids, treating the unrefined carbonized material with subcritical or supercritical carbon dioxide, and then heat-treating the unrefined carbonized material in a non-oxidizing atmosphere.

[0080] As described above, the negative electrode active material in the present invention is not limited to a particular material, but hard carbon may be used.

[0081] Hard carbon is a carbon material whose stacking order hardly changes even when heat-treated at high temperatures of 2000°C or higher, and is also called non-graphitizable carbon. Examples of hard carbon include carbon fibers obtained by carbonizing infusible yarn, an intermediate product in the carbon fiber manufacturing process, at about 1000 to 1400°C, and carbon materials obtained by air-oxidizing organic compounds at about 150 to 300°C and then carbonizing them at about 1000 to 1400°C. There are no particular limitations on the method for manufacturing hard carbon, and hard carbon manufactured by conventional methods can be used.

[0082] The content of the negative electrode active material in the negative electrode active material layer is not particularly limited, but is preferably 80 to 95 mass %. It is preferable.

[0083] The binder can be the same as that used for the positive electrode, so a detailed description of this will be omitted. The current collector is made of a conductive material such as aluminum, nickel, copper, or stainless steel (SUS). Like the current collector for the positive electrode, the current collector is made of foil, mesh, expanded grid (expanded metal), punched metal, or the like.

[0084] The method for forming the negative electrode active material layer on the current collector can be the same as the method for forming the positive electrode active material layer on the current collector.

[0085] (1-3.Liquid electrolyte) In the secondary battery of the present invention, the electrolyte is a liquid electrolyte (electrolytic solution), and a solution in which an electrolyte salt, a sodium salt and / or a potassium salt, is dissolved in a non-aqueous solvent is used.

[0086] One of the features of the secondary battery of the present invention is the liquid electrolyte used. The first feature of the liquid electrolyte is that, although the ion species contained in the positive electrode active material contains an element other than Na or K (Ca or Mg), a sodium salt and / or a potassium salt is used as the electrolyte salt in the liquid electrolyte.

[0087] The electrolyte salt and the non-aqueous solvent in the liquid electrolyte will be described below.

[0088] (1-3-1. Electrolyte salts) The electrolyte salt may be a sodium salt and / or a potassium salt.

[0089] Examples of sodium salts include sodium perchlorate (NaClO4), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium bis(fluorosulfonyl)imide (NaFSI), sodium 2-trifluoromethyl-4,5-dicyanoimidazolate (NaTDI), sodium bis(pentafluoroethylsulfonyl)imide (NaBETI), sodium trifluoromethanesulfonate (NaTF), sodium fluoride (NaF), sodium nitrate (NaNO3), etc. These electrolyte salts may be used alone or in combination of two or more, as long as the effects of the present invention are not impaired. Among these, sodium bis(fluorosulfonyl)imide (NaFSI) is a suitable example.

[0090] Examples of potassium salts include potassium hexafluorophosphate (KPF6), potassium bis(trifluoromethanesulfonyl)imide (KTFSI), potassium bis(fluorosulfonyl)imide (KFSI), potassium trifluoromethanesulfonate (KSO3CF3) (KTf), etc. These electrolyte salts may be used alone or in combination of two or more, as long as the effects of the present invention are not impaired. Among these, potassium bis(fluorosulfonyl)imide (KFSI) is a suitable example.

[0091] In the secondary battery of the present invention, examples of the electrolyte salt include potassium hexafluorophosphate (KPF6), potassium bis(trifluoromethanesulfonyl)imide (KTFSI), potassium bis(fluorosulfonyl)imide (KFSI), potassium trifluoromethanesulfonate (KSO3CF3) (KTf), etc. These electrolyte salts may be used alone or in combination of two or more, as long as the effects of the present invention are not impaired. Among these, potassium bis(fluorosulfonyl)imide (KFSI) is a suitable example.

[0092] The electrolyte salt concentration (sodium salt concentration and / or potassium salt concentration) in the electrolytic solution is preferably high, and the electrolyte salt concentration is, for example, 1 mol / L or more and not more than the saturated solubility.

[0093] (1-3-2. Non-aqueous solvents) One of the characteristics of the liquid electrolyte of the secondary battery of the present invention is that it uses a fluorinated phosphate as a non-aqueous solvent. Incidentally, a fluorinated phosphate ester is usually used as an additive to other non-aqueous solvents in order to impart flame retardancy and self-extinguishing properties to an electrolyte solution. However, the secondary battery of the present invention uses the above-described positive electrode active material of the present invention, and thereby the fluorinated phosphate ester itself can be used as the non-aqueous solvent for the electrolyte solution. Therefore, the secondary battery of the present invention has the advantage of being excellent in flame retardancy and self-extinguishing properties by using a fluorinated phosphate ester as the non-aqueous solvent of the electrolyte.

[0094] Examples of fluorinated phosphate esters include tris(2,2-difluoroethyl)phosphate, tris(2,2,2-trifluoroethyl)phosphate, bis(2,2,2-trifluoroethyl)methyl phosphate, and bis(2,2,2-trifluoroethyl)ethyl phosphate. Two or more of these fluorinated phosphate esters may be used in combination. Among these, tris(2,2,2-trifluoroethyl)phosphate (TFEP) is preferably used.

[0095] The liquid electrolyte of the secondary battery of the present invention may contain only a fluorinated phosphate ester, but may also contain a non-aqueous solvent other than the fluorinated phosphate ester in combination with the fluorinated phosphate ester.

[0096] As the nonaqueous solvent other than the fluorinated phosphate ester (hereinafter, sometimes referred to as "other nonaqueous solvent"), nonaqueous solvents used in nonaqueous secondary batteries can be used, and examples thereof include carbonates such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; ethers such as 1,2-dimethoxyethane and 1,3-dimethoxypropane; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolidone; and the above organic solvents further having a fluorine substituent introduced therein. Among these, propylene carbonate, ethylene carbonate and fluoroethylene carbonate are preferred from the viewpoint of battery performance. Two or more of these solvents may be used in combination.

[0097] The ratio of the fluorinated phosphate ester to the other non-aqueous solvent may be any ratio as long as the secondary battery of the present invention is capable of being charged and discharged. However, it is preferable that the fluorinated phosphate ester accounts for 30% by weight or more when the total of the fluorinated phosphate ester and the other non-aqueous solvent is taken as 100% by weight. In particular, when the fluorinated phosphate ester is tris(2,2,2-trifluoroethyl)phosphate (TFEP), the proportion of TFEP is 30% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more (including 100% by weight), and is selected appropriately depending on the other non-aqueous solvent.

[0098] (Suitable example of secondary battery) One of the characteristics of the secondary battery of the present invention is that it functions as a secondary battery even if the positive electrode active material is a composition containing Ca (particularly a composition containing Ca and substantially not containing Na or K) or even if a sodium salt or a potassium salt is used as the electrolyte salt. It should be noted that the secondary battery disclosed in the examples is a suitable example of the secondary battery of the present invention.

[0099] A preferred example of the secondary battery of the present invention is a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, in which the positive electrode contains a positive electrode active material containing Ca, and the electrolyte is a liquid electrolyte containing a sodium salt and / or a potassium salt as an electrolyte salt and 30 wt % or more of tris(2,2,2-trifluoroethyl)phosphate (TFEP) as a non-aqueous solvent.

[0100] As the Ca-containing positive electrode active material, a positive electrode active material obtained by heat-treating the raw material mixture obtained by mixing the components (A) to (D) described above in (1-1-1. Positive electrode active material) in a non-oxidizing atmosphere is preferably used.

[0101] As the non-aqueous solvent for the liquid electrolyte other than TFEP, the "other non-aqueous solvents" described above in (1-3-2. Non-aqueous solvents) can be used, and from the viewpoint of battery performance, propylene carbonate, ethylene carbonate, and fluoroethylene carbonate are preferred.

[0102] When the electrolyte salt of the liquid electrolyte is a sodium salt, it is more preferably sodium bis(fluorosulfonyl)imide (NaFSI). The electrolyte concentration (sodium salt concentration) in the liquid electrolyte (electrolytic solution) is preferably high, and the sodium salt concentration can be, for example, 1 mol / L or more and less than the saturated solubility.

[0103] When the electrolyte salt of the liquid electrolyte is a potassium salt, it is more preferably potassium bis(fluorosulfonyl)imide (KFSI). The electrolyte concentration (potassium salt concentration) in the liquid electrolyte (electrolytic solution) is preferably high, and the potassium salt concentration can be, for example, 1 mol / L or more and less than the saturated solubility.

[0104] <2. Electrode member manufacturing method and electrode member manufacturing system> The above-described method for producing a positive electrode active material of the present invention can be part of a method for producing an electrode member using a sulfur-containing rubber as a raw material (hereinafter referred to as "the method for producing an electrode member of the present invention"), which will be described below. Furthermore, the method for producing an electrode member of the present invention can be suitably realized using a system for producing an electrode member (hereinafter referred to as "the system for producing an electrode member of the present invention"), which will be described below.

[0105] The electrode member manufacturing method of the present invention produces electrode members (electrode active material, conductive material, and current collector) from sulfur-containing rubbers as raw materials, and not only the carbides, sulfur, and heavy oil that are the main raw materials for the electrode members, but also the light oil, sulfides, carbon dioxide, and waste heat that are produced as by-products can be reused and used as raw materials or energy. Therefore, the electrode member manufacturing method of the present invention can use sulfur-containing rubbers, such as those from tires, as raw materials for battery components.

[0106] The method for producing an electrode member of the present invention can use new raw materials, but has the advantage of being able to effectively use rubbers that are normally discarded (for example, waste tires) as raw materials.

[0107] The method for producing an electrode member of the present invention is a method for producing an electrode member using a sulfur-containing rubber as a raw material, wherein the electrode member is a positive electrode active material, and the method comprises the steps of thermally decomposing the raw material to separate it into a solid and a dry distillation gas, cooling the dry distillation gas to separate it into an oil component and a gas, distilling the oil component to separate it into a heavy oil, a light oil, and sulfur, kneading the heavy oil obtained by separating it, the sulfur, an ion raw material containing one or more elements selected from the group consisting of Na, K, Ca, and Mg, and a carbonized material for a positive electrode active material, and heat treating the mixture in a non-oxidizing atmosphere.

[0108] Another example of the method for manufacturing an electrode member of the present invention is a method for manufacturing an electrode member using sulfur-containing rubbers as a raw material, wherein the electrode member is a carbonized material for a negative electrode active material and / or a positive electrode active material, and is characterized by comprising the steps of pyrolyzing the raw material to separate it into a solid and a dry distillation gas, selecting an unrefined carbonized material from the solid, treating the unrefined carbonized material with subcritical or supercritical carbon dioxide, and then heat-treating it in a non-oxidizing atmosphere to obtain a refined carbonized material as a carbonized material for a negative electrode active material and / or a carbonized material for a positive electrode active material.

[0109] Another example of the method for manufacturing an electrode member of the present invention is a method for manufacturing an electrode member using a sulfur-containing rubber as a raw material, the electrode member being a positive electrode active material, the method comprising: step (1) of thermally decomposing the raw material to separate it into a solid and a dry distillation gas; step (2) of separating an unrefined carbonized product from the solid; step (3) of washing the unrefined carbonized product, heat-treating it in a non-oxidizing atmosphere, and then obtaining a refined carbonized product; step (4) of cooling the dry distillation gas to separate it into an oil and a gas, and distilling the oil to separate it into a heavy oil, a light oil, and sulfur; and step (5) of kneading an ion raw material (A) containing one or more elements selected from the group consisting of Na, K, Ca, and Mg, a carbonized product for a positive electrode active material (B), heavy oil (C), and sulfur (D), and heat-treating the resulting solid in a non-oxidizing atmosphere, and pulverizing and drying the resulting solid to obtain a positive electrode active material, wherein the method satisfies any one or more of the following requirements (i) to (iii): Requirement (i): At least a part of the carbonized material (B) for the positive electrode active material is a refined carbonized material obtained by step (3). Requirement (ii): At least a part of the heavy oil (C) is a heavy oil obtained by step (4). Requirement (iii): At least a part of the sulfur (D) is sulfur obtained by step (4).

[0110] The above-described method for manufacturing an electrode member of the present invention can be suitably carried out using the system for manufacturing an electrode member of the present invention.

[0111] The electrode member manufacturing system of the present invention is a manufacturing system for an electrode member that uses the above-described manufacturing method for an electrode member of the present invention, and includes a heat treatment means (x) that thermally decomposes the raw material to separate it into a solid and a dry distillation gas, a sorting means (y1) that sorts out an unrefined carbide from the solid, a washing means (y2) that washes the unrefined carbide, a heat treatment means (y3) that heat treats the washed unrefined carbide in a non-oxidizing atmosphere to obtain a refined carbide, and a cooling means (y4) that cools the dry distillation gas to separate it into an oil component and a gas, and a heat treatment means (y5) that cools the dry distillation gas to obtain a refined carbide. The electrode member manufacturing system includes a separation means (z1) for separating the oil into heavy oil, light oil, and sulfur by distillation, a kneading means (z2) for kneading an ion raw material (A) containing one or more elements selected from the group consisting of Na, K, Ca, and Mg, a carbide (B) for a positive electrode active material, heavy oil (C), and sulfur (D) to obtain a raw material mixture, a heat treatment means (z3) for heat treating the raw material mixture in a non-oxidizing atmosphere to obtain a solid, and an adjustment means (z4) for pulverizing and drying the obtained solid.

[0112] An example of an embodiment of the electrode member manufacturing method and the electrode member manufacturing system of the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the following embodiment, and can be implemented with any modifications within the scope of the gist of the present invention.

[0113] FIG. 1 is a conceptual diagram of a manufacturing system for battery components according to an embodiment of the present invention. As shown in Figure 1, in the battery component manufacturing system of this embodiment, sulfur-containing rubbers are used as raw materials, the raw materials are thermally decomposed to separate them into solids and dry distillation gas, unrefined carbonized material is selected from the solids, refined carbonized material (carbonized material for negative electrode active material and / or positive electrode active material (corresponding to component (B) above)) is produced from the obtained unrefined carbonized material, the dry distillation gas is further cooled to separate it into oil and gas components, the oil component is distilled to separate it into heavy oil, light oil, and sulfur, and the obtained heavy oil (corresponding to component (C) above) and sulfur (corresponding to component (D) above) are kneaded with the refined carbonized material (corresponding to component (B) above) and an ion raw material (corresponding to component (A) above) and heat-treated to produce a positive electrode active material. In this way, rubbers containing sulfur as raw materials can be recycled and used as electrode materials.

[0114] The resulting negative electrode active material can be applied to a negative electrode current collector together with a binder to produce a negative electrode. The resulting positive electrode active material can be applied to a positive electrode current collector together with a binder to produce a positive electrode. A battery can be manufactured using the resulting positive electrode and negative electrode. The negative electrode active material, negative electrode conductive material, and negative electrode, as well as the positive electrode active material, positive electrode conductive material, and positive electrode according to the present invention, are not limited to being used to manufacture the same battery, but can also be used to manufacture separate batteries.

[0115] In the battery component manufacturing system according to the embodiment of the present invention, first, raw rubber is subjected to thermal decomposition treatment using a thermal decomposition furnace as a heat treatment means (x), whereby the raw rubber is separated into a solid material and a gaseous dry distillation gas. The heat used to pyrolyze the rubber raw material in the pyrolysis furnace is the combustion heat generated when light oil is burned in the combustion furnace, which is the combustion means (w2). If the combustion heat is insufficient, fuel is added from the outside to heat the system. By using the combustion heat from light oil, the need for additional fuel from the outside can be reduced, improving the energy efficiency of the production method (and production system) according to this embodiment. The thermal decomposition conditions in the thermal treatment means (x) (shape and dimensions of the thermal decomposition furnace, temperature, thermal decomposition time, etc.) can be appropriately set depending on the amount and type of raw material to be thermally decomposed, etc. Any thermal treatment means can be used as the thermal treatment means (x) as long as it can thermally decompose the raw material and separate it into a solid and a dry distillation gas.

[0116] The raw material rubbers may be any rubbers containing sulfur, and are preferably rubbers derived from tires. Here, "rubbers derived from tires" refers to rubbers contained in tires, which are obtained by removing components other than rubbers (metals such as reinforcing materials). The tire may be any tire that uses vulcanized rubber, and examples thereof include pneumatic tires, solid tires, etc. Furthermore, new tires can be used as the raw rubber material, but tires that are discarded after use (waste tires) and waste materials that are generated and discarded as defective or surplus materials during the tire manufacturing process and contain sulfur-containing rubber as the main component can also be suitably used. Furthermore, the rubbers used as raw materials can be used not only for the above-mentioned tires but also for, for example, vibration-proof rubber members for automobiles.

[0117] The solid matter separated from the rubbers by pyrolysis is sorted using a sorting machine, which is sorting means (y1). This separates the solid matter into crude charcoal and matter other than crude charcoal (typically metals). As mentioned above, tires contain metals such as reinforcing materials in addition to rubbers, and the sorting process removes the metals from the solid matter.

[0118] The sorting means (y1) can be any sorting means as long as it can separate the crude carbide from the solid material obtained by the heat treatment means (x). For example, a magnetic separator, a wind separator, or a sieve separator can be used as the sorting means (y1).

[0119] The metals separated from the solids can be recycled as metal resources.

[0120] Meanwhile, the crude carbonized material separated from the solid matter is washed to remove impurities. Specifically, by performing subcritical or supercritical carbon dioxide treatment using a subcritical / supercritical treatment device, which is the washing means (y2), the crude carbonized material is washed with subcritical or supercritical carbon dioxide, thereby improving the quality and performance of the carbonized material (purified carbonized material) for use as an anode active material or a cathode active material.

[0121] The unrefined char separated from the solids may be crushed if necessary before washing.

[0122] Any washing means can be used as the washing means (y2) as long as it can wash the unrefined carbonized material separated from the solid matter.

[0123] The washed unpurified carbide is subjected to heat treatment (in a non-oxidizing atmosphere, at 500 to 1200°C) using a heat treatment machine, which is the heat treatment means (y3), to obtain a purified carbide. The obtained purified carbide can be recycled and reused as a carbide for a negative electrode active material or a positive electrode active material. The heat treatment conditions in the heat treatment means (y3) (shape and dimensions of the heat treatment machine, temperature, heat treatment time, etc.) can be appropriately set depending on the amount and type of unrefined carbide to be heat treated, etc. Any heat treatment means can be used as the heat treatment means (y3) as long as it can heat treat the unrefined carbide to be heat treated in a non-oxidizing atmosphere and obtain refined carbides (carbides for negative electrode active material and positive electrode active material).

[0124] Furthermore, the resulting refined carbide is preferably subjected to a treatment to remove iron, particularly when used as a negative electrode active material.

[0125] When the obtained purified carbide is to be used as a negative electrode active material, it is preferable to pulverize it. The obtained purified carbide can be pulverized into fine powder by a pulverizer, which is the pulverizing means (w3). The pulverized purified carbide can be molded using a binder as a negative electrode active material and recycled for use as a negative electrode of a battery. Examples of the pulverizing means (w3) include pulverizers such as a vibration mill, a jet mill, and a dry ball mill.

[0126] The resulting refined carbide can also be used for purposes other than the negative electrode active material of secondary batteries and conductive materials (for example, active materials for capacitors and carriers for fuel cell catalysts).

[0127] Meanwhile, the dry distillation gas separated from the rubbers by thermal decomposition is sent to a separation means (z1) that separates the dry distillation gas. The separation means (z1) has a cooler that separates the dry distillation gas into gas and liquid, a distiller that distills the liquid separated in the cooler, and a desulfurizer (not shown) that removes sulfur from the gas or liquid. The carbonized gas is first cooled using a cooler, whereby the carbonized gas is separated into a liquid oil fraction and a gas fraction (non-condensed gas).

[0128] Here, the production ratio and composition of heavy oil and non-condensable gas can be controlled by the cooling temperature of the cooler. Lowering the cooling temperature increases the production ratio of heavy oil and reduces the amount of hydrocarbons contained in the non-condensable gas. Therefore, it is possible to detect the hydrocarbon concentration of the non-condensable gas with a detector and control the cooling temperature so that the concentration remains constant.

[0129] The non-condensed gas separated from the dry distillation gas is decompressed and then desulfurized using a desulfurizer. The sulfur recovered by the desulfurizer can be used to produce a positive electrode active material.

[0130] The non-condensable gas after desulfurization is a hydrocarbon gas that does not contain sulfur and is sent to the gas processing means (w1). The gas processing means (w1) has a combustor and a carbon dioxide recovery unit. The desulfurized non-condensable gas is combusted in the combustor, and then the carbon dioxide is recovered in the carbon dioxide recovery unit, and the rest is vented. Some or all of the recovered CO2 can be used for subcritical or supercritical carbon dioxide treatment of the unpurified char in the above-mentioned washing means (y2).

[0131] On the other hand, the oil fraction separated from the dry distillation gas is distilled at a temperature above the boiling point of sulfur using a distiller. This process separates light oil containing a large amount of sulfur, leaving heavy oil containing almost no sulfur.

[0132] Light oil containing sulfur is desulfurized in a desulfurizer to separate it into sulfur and sulfur-free light oil, which can then be recovered. The separated sulfur-free light oil can then be recycled as fuel.

[0133] The separation means (z1) according to this embodiment includes a cooler, a distiller, and a desulfurizer, but any separation means can be used as the separation means (z1) according to the present invention as long as it can separate the dry distillation gas obtained by the heat treatment means (x) into gas components, heavy oil, light oil, and sulfur.

[0134] As described above, the separated heavy oil and sulfur are kneaded together with the refined carbide (cathode active material) and ion raw material recovered from the solid matter using a kneader, which is the kneading means (z2), and then heat-treated in a heat treatment machine (non-oxidizing atmosphere), which is the heat treatment means (z3). The mixture is then pulverized in a pulverizer included in the adjustment means (z4), and further dried in a vacuum dryer included in the adjustment means (z4), thereby producing the desired solid cathode active material.

[0135] The kneading means (z2), the heat treatment means (z3) and the adjusting means (z4) are optional as long as they do not impair the object of the present invention. The kneading means (z2) may be a dry mixer commonly used in industry. Examples of dry mixers include a V-type mixer, a W-type mixer, a ribbon mixer, a drum mixer, and a dry ball mill. Furthermore, the kneading may also be carried out by wet mixing, provided that the object of the present invention is not impaired. Examples of the heat treatment means (z3) include an electric heat treatment machine, a combustion heat treatment machine, a batch heat treatment machine, and a flow heat treatment machine. Examples of the pulverizer included in the adjusting means (z4) include a vibration mill, a jet mill, and a dry ball mill.

[0136] Here, the ion raw material, the carbonized material for the positive electrode active material, the heavy oil, and the sulfur correspond to the component (A), the component (B), the component (C), and the component (D) in the above-mentioned <1. Method for producing the positive electrode active material>, respectively.

[0137] The ion raw material has been described in detail above as component (A), and therefore will not be described here. For example, raw materials such as eggshells, plant-derived materials (plants), seashells, gypsum, and hot spring scale are subjected to heat treatment or other treatment using a heat treatment machine, which is the ion raw material production means (w4), and used as an ion raw material containing one or more elements selected from the group consisting of Na, K, Ca, and Mg (preferably an ion raw material containing Ca).

[0138] In addition, in this embodiment, the carbonized material for the positive electrode active material (component (B)), heavy oil (component (C)), and sulfur (component (D)) used in the production of the positive electrode active material are not limited to those derived from the rubbers used as raw materials, and those produced from other raw materials or commercially available products may be added as needed. However, it is preferable that at least a portion of the carbonized material for the positive electrode active material (component (B)), heavy oil (component (C)), and sulfur (component (D)) used in the production of the positive electrode active material are obtained by the method for producing an electrode member of the present invention.

[0139] That is, in the method for manufacturing an electrode member of the present invention, it is preferable that at least a portion of the carbonized material for the positive electrode active material (component (B)) is a refined carbonized material obtained by thermally decomposing sulfur-containing rubbers to separate them into solids and dry distillation gas, sorting out crude carbonized material from the solids, and heat treating the crude carbonized material; at least a portion of the heavy oil (component (C)) is a heavy oil obtained by cooling the dry distillation gas to separate it into oil and gas, and distilling the oil to separate it into heavy oil, light oil, and sulfur; and at least a portion of the sulfur (component (D)) is sulfur obtained by distilling the oil to separate it into heavy oil, light oil, and sulfur.

[0140] In addition, in producing the positive electrode active material, sulfides (particularly hydrogen sulfide) generated during heat treatment in the heat treatment means (z3) are desulfurized with an aqueous solution containing a neutralizing agent in a neutralizer, which is the neutralization means (w5), and sulfur content is recovered. In addition, a solid (neutralized solid) containing ions obtained by evaporating water from the aqueous solution containing the neutralizing agent used in the desulfurization treatment can also be reused as an ion raw material.

[0141] Although the embodiments of the method for manufacturing an electrode member of the present invention have been described above with reference to the drawings, the embodiments disclosed herein are illustrative in all respects and are not limiting. In particular, matters not explicitly disclosed in the embodiments disclosed herein, such as operating conditions, various parameters, dimensions, weights, volumes, etc., do not deviate from the scope of ordinary practice by a person skilled in the art, and values ​​that can be easily assumed by a person skilled in the art can be used. [Example]

[0142] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following, "%" means "% by weight" unless otherwise specified.

[0143] (Experimental Example 1) The positive electrode active material of Experimental Example 1 was obtained by the following procedure. Wood combustion ash (plant combustion ash) obtained by burning wood (camellia trees) in air using a heating furnace was used as component (A). In addition, charcoal derived from waste tires, "Renesis A1 (product number)," was used as the charcoal for the positive electrode active material (component (B)). The waste tire-derived charcoal "Renesis A1 (product number)" used as the charcoal for the positive electrode active material (component (B)) was obtained by heating waste tires in an inert atmosphere container at 400°C for two hours, gasifying the components within the waste tires and converting them into oil through cooling (gasification and oil conversion totaling approximately 55%), and recovering the residue that was neither gasified nor converted into oil. The recovered waste tire pyrolysis residue was further heat-treated, pulverized to an average particle size of 20μm, and then completely removed magnetic material using a 16,000 gauss electromagnetic separator to obtain the charcoal derived from waste tire pyrolysis residue.

[0144] A total of 30.7 g of raw materials, consisting of 12.7 g (41% of the total raw materials) of wood combustion ash (component (A)), 6 g (20% of the total raw materials) of carbonized material for the positive electrode active material (component (B)), 3 g (10% of the total raw materials), and 9 g (29% of the total raw materials), was mixed in a stainless steel container and placed in a heating furnace. Nitrogen gas was introduced into the container to create an inert atmosphere, and heating began 10 minutes later. The temperature was raised to 300°C in 50 minutes. Heating continued even after reaching 300°C and stopped at 350°C. After the temperature dropped to 200°C, the container was removed from the heating furnace and allowed to cool naturally. After the temperature inside the container had dropped below 50°C, the synthesized product was removed. The weight of the synthesized product was 21.9 g, a yield of 71%. The synthesized product was pulverized in a mixer to obtain the positive electrode active material of Experimental Example 1, consisting of a powder with an average particle size of 20 μm.

[0145] A positive electrode mixture for Experimental Example 1 was obtained by uniformly mixing (kneading) 1.14 g of the positive electrode active material of Experimental Example 1 and 0.08 g of acetylene black (AB, Denki Kagaku Kogyo Co., Ltd. (HS100)) as a conductive material with 2.453 g of N-methyl-2-pyrrolidone (NMP) solvent containing 0.073 g of polyvinylidene fluoride (PVDF) (carbon nanotubes (CNTs) were essentially 0.025 g, solid content ratio 2.14%). Next, the obtained positive electrode mixture was applied to an aluminum sheet (thickness: 16 μm) that would serve as a positive electrode current collector, and dried at 50° C. for 3 hours to obtain a positive electrode sheet. A piece of 12.9 mmφ was cut out from the obtained positive electrode sheet to provide the positive electrode of Experimental Example 1.

[0146] The negative electrode was prepared as follows. The negative electrode active material used was the same carbonized material used for the positive electrode active material, "Renesis A1 (product number)," derived from waste tires. 1.5 g (92.71% of the total) of the negative electrode active material (carbonized waste tires) and 0.106 g (6.55% of the total) of polyacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name 20CLPAH) as a binder were mixed in an aqueous solution containing 0.007 g of carboxymethyl cellulose (CMC) and 0.005 g of CNTs ("TUBALL" by Kusumoto Chemical Co., Ltd.) as a solvent. TMThe mixture was mixed (kneaded) with 1.2 g of BATT H2O (CMC) to obtain a negative electrode mixture. Next, the obtained negative electrode mixture was applied to an aluminum sheet (thickness: 16 μm) that would serve as a negative electrode current collector, and dried at 70° C. for 3 hours to obtain a negative electrode sheet. A negative electrode having a diameter of 11.3 mm was cut out from the obtained negative electrode sheet.

[0147] The obtained positive and negative electrodes were combined with an electrolyte solution (KFSI / TFEP) in which potassium bis(fluorosulfonyl)imide (KFSI) as a potassium salt was dissolved to a concentration of 2 mol / L in tris(2,2,2-trifluoroethyl)phosphate (TFEP), and Celgard 2400 as a separator to obtain a battery (coin-type battery (R2032)) of Experimental Example 1.

[0148] Using the battery of Experimental Example 1, a charge / discharge test was carried out under the following conditions while maintaining the temperature at 25°C. (Cell configuration) 2-electrode type Positive electrode: An electrode containing a positive electrode active material Negative electrode: An electrode containing a negative electrode active material Electrolyte: 2M KFSI / TFEP (Charge / discharge conditions) Voltage range: 1.2-3.8V CVCC charge, CC discharge (The initial voltage hold CV is 30 hours, the second is 10 hours, and the third and subsequent times are 5 hours.)

[0149] The results of the charge / discharge test of the battery of Experimental Example 1 are as follows. 112μA / 1.306cm 2 (Positive electrode 12.9mmφ) Number of charge / discharge cycles: 27 Discharge time: Approximately 1 hour (112μAh)

[0150] As described above, it was confirmed that a rechargeable secondary battery can be produced using a positive electrode active material obtained by heat-treating wood combustion ash (component (A)), carbonized material for the positive electrode active material (component (B)), coal tar (component (C)), and sulfur (component (D)) under an inert gas atmosphere.

[0151] (Experimental Example 2) The positive electrode active material of Experimental Example 2 was obtained by the following procedure. Eggshells were heat-treated at 1200°C in a heating furnace to produce calcined eggshells, which were used as component (A). When the calcined eggshells were evaluated using X-ray diffraction, a signal corresponding to crystalline CaO was confirmed. Furthermore, a carbonized material derived from waste tires, "Renesis A1 (product number)" (the same as in Experimental Example 1), was used as the carbonized material for the positive electrode active material (component (B)). A total of 48.8 g of raw materials, consisting of 25 g (51% of the total raw materials) of baked eggshells (component (A)), 10 g (20% of the total raw materials) of carbonized material for the positive electrode active material (component (B)), 3.8 g (8% of the total raw materials), and 10 g (20% of the total raw materials), was mixed in a stainless steel container and placed in a heating furnace. Nitrogen gas was introduced into the container to create an inert atmosphere, and heating began 10 minutes later. The temperature was raised to 300°C in 50 minutes. Heating continued after reaching 300°C and stopped at 350°C. After the temperature dropped to 200°C, the container was removed from the heating furnace and allowed to cool naturally. The synthesized product was removed after the internal temperature of the container dropped below 50°C. The weight of the synthesized product was 32.5 g, representing a yield of 67%. The synthesized product was pulverized in a mixer to obtain the positive electrode active material of Experimental Example 2, consisting of a powder with an average particle size of 20 μm.

[0152] The positive electrode mixture of Experimental Example 2 was obtained by uniformly mixing (kneading) 4.015 g of the positive electrode active material of Experimental Example 2 and 0.08 g of AB as a conductive material with 2.453 g of NMP solvent containing 0.073 g of PVDF (CNT was essentially 0.025 g, solid content ratio 2.14%). Next, the obtained positive electrode mixture was applied to an aluminum sheet (thickness: 16 μm) that would serve as a positive electrode current collector, and dried at 50° C. for 3 hours to obtain a positive electrode sheet. A piece of 11.3 mmφ was cut out from the obtained positive electrode sheet to provide the positive electrode of Experimental Example 2.

[0153] The negative electrode was prepared in the same manner as in Experimental Example 1.

[0154] The obtained positive and negative electrodes were combined with an electrolyte solution of tris(2,2,2-trifluoroethyl)phosphate (TFEP) in which potassium bis(fluorosulfonyl)imide (KFSI) as a potassium salt was dissolved to a concentration of 2 mol / L (KFSI / TFEP), and Celgard 2400 as a separator to obtain a battery (coin-type battery (R2032)) of Experimental Example 2.

[0155] Using the battery of Experimental Example 2, a charge-discharge test was carried out under the following conditions while maintaining the temperature at 25°C. (Cell configuration) 2-electrode type Positive electrode: An electrode containing a positive electrode active material Negative electrode: An electrode containing a negative electrode active material Electrolyte: 2M KFSI / TFEP (Charge / discharge conditions) Voltage range: 1.2-3.8V CVCC charge, CC discharge (The initial voltage hold CV is 30 hours, the second is 10 hours, and the third and subsequent times are 5 hours.)

[0156] The results of the charge / discharge test of the battery of Experimental Example 2 are as follows. 75μA / 1cm 2 (Positive electrode 11.3mmφ) Number of charge / discharge cycles: 48 Discharge time: Approximately 1 hour (75μAh)

[0157] As described above, it was confirmed that a rechargeable secondary battery can be produced using a positive electrode active material obtained by heat-treating baked eggshells (component (A)), carbonized material for positive electrode active material (component (B)), coal tar (component (C)), and sulfur (component (D)) under an inert gas atmosphere.

[0158] (Experimental Example 3) The positive electrode was prepared in the same manner as in Experimental Example 2. First, in the same procedure as in Experimental Example 2, baked eggshells (component (A)), carbonized material for positive electrode active material (component (B)), coal tar (component (C)), and sulfur (component (D)) were heat-treated under an inert gas atmosphere to obtain a positive electrode active material (the same as the positive electrode active material in Experimental Example 2). 4.015 g of the obtained positive electrode active material and 0.1 g of AB as a conductive material were mixed (kneaded) uniformly into 3.84 g of NMP solvent containing 0.23 g of PVDF (CNT was substantially 0.01 g), thereby obtaining a positive electrode mixture for Experimental Example 3. Next, the obtained positive electrode mixture was applied to an aluminum sheet (thickness: 16 μm) that would serve as a positive electrode current collector, and dried at 50° C. for 3 hours to obtain a positive electrode sheet. A piece of 11.3 mmφ was cut out from the obtained positive electrode sheet to provide the positive electrode of Experimental Example 3.

[0159] The negative electrode was prepared in the same manner as in Experimental Example 1.

[0160] The obtained positive and negative electrodes were combined with an electrolyte solution (KFSI / TFEP-PC) prepared by dissolving potassium bis(fluorosulfonyl)imide (KFSI) as a potassium salt in a mixed solvent of 40% by weight of tris(2,2,2-trifluoroethyl)phosphate (TFEP) and 60% by weight of propylene carbonate (PC) to a concentration of 2 mol / L, and Celgard 2400 as a separator to obtain a battery (coin-type battery (R2032)) of Experimental Example 3.

[0161] Using the battery of Experimental Example 3, a charge / discharge test was carried out under the following conditions while maintaining the temperature at 25°C. (Cell configuration) 2-electrode type Positive electrode: An electrode containing a positive electrode active material Negative electrode: An electrode containing a negative electrode active material Electrolyte: 2M KFSI / TFEP(40)-PC(60) (Charge / discharge conditions) Voltage range: 1.2-3.8V CVCC charge, CC discharge (The initial voltage hold CV is 30 hours, the second is 10 hours, and the third and subsequent times are 5 hours.)

[0162] The results of the charge / discharge test of the battery of Experimental Example 3 are as follows. 75μA / 1cm 2 (Positive electrode 11.3mmφ) Charge / discharge cycles: 30 times Discharge time: Approximately 1 hour (75μAh)

[0163] As described above, it was confirmed that a rechargeable secondary battery can be produced using a positive electrode active material obtained by heat-treating baked eggshells (component (A)), carbonized material for positive electrode active material (component (B)), coal tar (component (C)), and sulfur (component (D)) under an inert gas atmosphere. [Industrial Applicability]

[0164] The secondary battery of the present invention does not require or use lithium or transition metal elements, and uses inexpensive raw materials that are in abundant supply (sodium, potassium, calcium, sulfur, carbides, etc., and waste-derived raw materials can also be used). Therefore, the secondary battery of the present invention is suitable not only as a small battery that is a power source for small devices, but also as a medium- to large-sized battery (for example). The secondary battery of the present invention can be suitably used, for example, as an outdoor / indoor power source for factories, homes, etc.; a load-leveling power source for various power generation devices such as solar battery charging devices and wind power generation charging devices; and the like, and therefore the present invention is extremely useful industrially.

Claims

1. A secondary battery, a positive electrode, a negative electrode, and an electrolyte; The positive electrode comprises a positive electrode active material obtained by heat-treating a raw material mixture obtained by mixing the following components (A) to (D) in a non-oxidizing atmosphere, The secondary battery is characterized in that the electrolyte is a liquid electrolyte containing a sodium salt and / or a potassium salt as an electrolyte salt and a non-aqueous solvent. Component (A): An ion source containing one or more elements selected from the group consisting of Na, K, Ca, and Mg. Component (B): Carbide for positive electrode active material Component (C): Heavy oil Component (D): Sulfur

2. 2. The secondary battery according to claim 1, wherein the component (A) is an ionic raw material containing Ca.

3. 2. The secondary battery according to claim 1, wherein at least a part of component (A) is at least one selected from the group consisting of plant combustion ash, burned eggshells, burned seashells, gypsum, and hot spring scale.

4. 2. The secondary battery according to claim 1, wherein at least a portion of component (B) is a refined carbonized material obtained by thermally decomposing a sulfur-containing rubber to separate it into a solid material and a dry distillation gas, separating an unrefined carbonized material from the solid material, and heat-treating the unrefined carbonized material.

5. 2. The secondary battery according to claim 1, wherein at least a portion of component (C) is heavy oil obtained by thermally decomposing sulfur-containing rubbers to separate them into solids and dry distillation gas, cooling the dry distillation gas to separate them into oil and gas, and distilling the oil to separate them into heavy oil, light oil, and sulfur.

6. 2. The secondary battery according to claim 1, wherein at least a portion of component (D) is sulfur obtained by thermally decomposing sulfur-containing rubbers to separate them into solids and dry distillation gas, cooling the dry distillation gas to separate them into oil and gas, and distilling the oil to separate them into heavy oil, light oil, and sulfur.

7. Component (A) is at least one selected from the group consisting of plant combustion ash, burned eggshells, burned seashells, gypsum, and hot spring scale; at least a part of component (B) is a refined carbonized product obtained by thermally decomposing a sulfur-containing rubber to separate it into a solid and a dry distillation gas, separating an unrefined carbonized product from the solid, and heat-treating the unrefined carbonized product; at least a portion of the component (C) is a heavy oil obtained by cooling the dry distillation gas to separate it into an oil component and a gas, and then distilling the oil component to separate it into a heavy oil component, a light oil component, and sulfur; 2. The secondary battery according to claim 1, wherein at least a part of the component (D) is sulfur obtained by distilling the oil and separating it into heavy oil, light oil, and sulfur.

8. 2. The secondary battery according to claim 1, wherein the sulfur-containing rubber is rubber derived from tires.

9. 9. The secondary battery according to claim 1, wherein the liquid electrolyte contains 30% by weight or more of a fluorinated phosphate ester as a non-aqueous solvent.

10. 10. The secondary battery according to claim 9, wherein the fluorinated phosphate ester is tris(2,2,2-trifluoroethyl)phosphate (TFEP).

11. 10. The secondary battery according to claim 9, wherein the sodium salt in the liquid electrolyte is sodium bis(fluorosulfonyl)imide (NaFSI) and the potassium salt in the liquid electrolyte is potassium bis(fluorosulfonyl)imide (KFSI).

12. A liquid electrolyte for use in a secondary battery having a positive electrode using a positive electrode active material containing Ca, A liquid electrolyte containing a sodium salt and / or a potassium salt as an electrolyte salt and a fluorinated phosphate ester as a non-aqueous solvent.

13. The liquid electrolyte according to claim 12, wherein the positive electrode active material is a positive electrode active material obtained by heat-treating a raw material mixture obtained by mixing the following components (A) to (D) in a non-oxidizing atmosphere: Component (A): An ion source containing one or more elements selected from the group consisting of Na, K, Ca, and Mg. Component (B): Carbide for positive electrode active material Component (C): Heavy oil Component (D): Sulfur

14. 14. The liquid electrolyte according to claim 13, wherein component (A) is an ion source containing Ca.

15. 13. The liquid electrolyte according to claim 12, wherein the liquid electrolyte contains 30% by weight or more of a fluorinated phosphate ester as a non-aqueous solvent.

16. 13. The liquid electrolyte according to claim 12, wherein the fluorinated phosphate ester is tris(2,2,2-trifluoroethyl)phosphate (TFEP).

17. 13. The liquid electrolyte of claim 12, wherein the sodium salt in the liquid electrolyte is sodium bis(fluorosulfonyl)imide (NaFSI) and the potassium salt is potassium bis(fluorosulfonyl)imide (KFSI).

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