Secondary battery

Abstract

To provide a method for manufacturing a lithium ion secondary battery that is safer and less expensive.SOLUTION: A method for manufacturing a positive electrode for a secondary battery includes the steps of mixing graphene oxide, a binder, and a positive electrode active material in a solvent containing water to prepare a slurry, applying the slurry to a positive electrode current collector, and reducing the graphene oxide by at least one of chemical reduction and thermal reduction. Ascorbic acid can be used as a reducing agent for the chemical reduction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an article, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, relating to the manufacture or composition of matter, especially One embodiment of the present invention is a semiconductor device, a display device, a light-emitting device, a secondary battery, a power storage device, or a memory device. In particular, one aspect of the present invention relates to a method for driving the same or a method for manufacturing the same. The present invention relates to a secondary battery, a power storage device, and a manufacturing method thereof.

[0002] In this specification, a secondary battery or a power storage device refers to an element or device having a power storage function. It refers to the general. [Background technology]

[0003] In recent years, lithium-ion secondary batteries, lithium-ion capacitors, air batteries, all-solid-state batteries, etc. The development of various types of energy storage devices is actively underway, especially lithium-ion batteries, which have high output and capacity. Demand for secondary batteries has rapidly expanded along with the development of the semiconductor industry, and It has become an indispensable source of information in today's information society.

[0004] For example, in applications such as large-scale secondary batteries for home use and secondary batteries for vehicles, the positive electrode activity of lithium-ion batteries is Those using lithium iron phosphate (LiFePO4, abbreviated as LFP) as the material have already been commercialized. (Non-Patent Document 1).

[0005] On the other hand, graphene has attracted much attention in recent years due to its excellent conductivity, and As shown in Non-Patent Document 2, graphene oxide (gra The compound obtained by reducing GO ( It is sometimes called RGO, and its physical properties have been attracting attention. The GO was analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, etc. There are studies that have characterized the physical properties. In addition, as shown in Patent Document 1, there are examples of using GO in secondary batteries. There are also. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-007141 [Non-patent literature]

[0007] [Non-Patent Document 1] Naoki Nitta et al., “Li-ion battery materials: present and future” Materials Today, Volume 18, Number 5 June 2015, pp252-264. [Non-patent document 2] A. Bagri et al., “Structural evolution during the reduction of chemically derived graphene oxide”, NATURE CHEMISTRY, vol.2,2010,pp.581-587. [Non-patent document 3] Burcu Saner et al., “Utilization of multiple graphene nanosheets in fuel cells: 2. The effect of oxidation process on the characteristics of graphene nanosheets”, Fuel, 90, 2011, pp. 2609-2616. [Non-patent document 4] Hirokazu Suzuki et al., "Carbonization Characteristics of Carbohydrates Using Superheated Steam," Journal of the Japanese Society of Food Science and Technology, Vol. 8, No. 1, pp. 39-43, March 2007. Summary of the Invention [Problem to be solved by the invention]

[0008] Lithium-ion batteries using LFP as the positive electrode active material are promising in terms of safety and cost. Therefore, it is expected that lithium-ion batteries using LFP will be mass-produced in the future. It is expected.

[0009] The electrode manufacturing process for lithium-ion batteries, including those using LFP, involves the use of active materials, conductive materials, Large amounts of organic solvents are used as solvents for slurries containing binders, and for wet mixing. These organic solvents are evaporated in the subsequent steps.

[0010] The organic solvent often used for this purpose is the aprotic polar solvent N-methylpyrrolidine. However, NMP is known to cause skin irritation and may be toxic to reproduction. It is a material that is harmful to health, so it must be collected within the manufacturing plant and not released into the environment. This process increases the manufacturing cost of lithium-ion batteries. .

[0011] Therefore, if it were possible to produce a slurry using water as a solvent in the production process, it would be safer and cheaper. Lithium-ion batteries can be made.

[0012] One embodiment of the present invention is a cathode for a lithium ion secondary battery using water as a solvent in a manufacturing process. Another object of the present invention is to provide a method for manufacturing a safer relay electrode. Another object of the present invention is to provide a method for manufacturing a positive electrode for a lithium ion secondary battery. One aspect of the present invention is to provide a method for producing a lithium ion secondary battery at a reduced cost. Another object of the present invention is to provide a secondary battery with favorable cycle characteristics. Another object of one embodiment of the present invention is to provide a secondary battery with favorable rate characteristics. Another object of one embodiment of the present invention is to provide a secondary battery with higher capacity. Another object of one embodiment of the present invention is to provide a safer secondary battery. Another object of one embodiment of the present invention is to provide a novel power storage device. do.

[0013] The description of these problems does not preclude the existence of other problems. It is not necessary for the embodiments to solve all of these problems. It is possible to extract other problems from the description of the claim. [Means for solving the problem]

[0014] One embodiment of the present invention is a method for manufacturing a positive electrode for a secondary battery, the method comprising: a step of mixing the positive electrode active material with a solvent containing water to prepare a slurry; a step of applying graphene oxide to a positive electrode current collector and a step of reducing the graphene oxide. The step of reducing laphene includes at least one of chemical reduction and thermal reduction. This is a method for producing a positive electrode.

[0015] Another embodiment of the present invention is a method for manufacturing a positive electrode for a secondary battery, the method including: a step of mixing the cathode active material and the cathode active material with a solvent containing water to prepare a slurry; The method includes a step of applying the slurry to a positive electrode current collector and a step of reducing graphene oxide. The process of reducing graphene oxide is chemical reduction and thermal reduction. It is the law.

[0016] In the above, chemical reduction is a process of immersing in a reducing agent solution, and thermal reduction is a process of immersing in a reducing agent solution at 125°C or higher. Preferably, the process involves heating at 00°C or lower for 1 hour or more and 20 hours or less.

[0017] In the above, the binder preferably contains a polysaccharide. It is preferable that

[0018] In the above, the reducing agent solution is preferably an ascorbic acid solution.

[0019] Another embodiment of the present invention is a secondary battery including a positive electrode, a negative electrode, a separator, and an electrolyte solution. The positive electrode has a positive electrode active material, a conductive material, a binder, and a positive electrode current collector. The battery is a secondary battery in which the conductive material is lithium iron phosphate and the conductive material is reduced graphene oxide.

[0020] In the above, the reduced graphene oxide has carbon and oxygen and has a sheet-like shape. It has a two-dimensional structure formed by six-membered carbon rings, and the reduced graphene oxide has The carbon concentration is greater than 80 atomic % and the oxygen concentration is greater than 2 atomic % and less than 15 atomic %. It is preferable to have a portion where the content is less than atomic percent.

[0021] In addition, the reduced graphene oxide exhibits the G band in the Raman spectrum. It is preferable that the intensity ratio G / D to the D band is 1 or more. [Effects of the Invention]

[0022] According to one embodiment of the present invention, a lithium ion secondary battery using water as a solvent in a manufacturing process Another aspect of the present invention is to provide a method for manufacturing a positive electrode for a lithium battery. A method for manufacturing a positive electrode for a lithium-ion secondary battery can be provided. This makes it possible to provide a method for producing a lithium ion secondary battery at a reduced cost. Another embodiment of the present invention can provide a secondary battery with favorable cycle characteristics. According to one embodiment of the present invention, a secondary battery having favorable rate characteristics can be provided. According to one embodiment of the present invention, a secondary battery with a higher capacity can be provided. In addition, a safer secondary battery can be provided. Locations can be provided.

[0023] The description of these effects does not preclude the existence of other effects. The embodiment does not necessarily have to have all of these effects. , the specification, drawings, claims, etc., and It is possible to extract other effects from the claims and other descriptions. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 shows an example of a method for manufacturing a positive electrode for a secondary battery according to one embodiment of the present invention. [Figure 2] FIG. 2 illustrates an example of a method for manufacturing a positive electrode for a secondary battery according to one embodiment of the present invention. [Figure 3] 3(A) and 3(B) are cross-sectional views of active material layers in which graphene and a graphene compound are used as conductive materials. [Figure 4] 4(A) and 4(B) are diagrams illustrating an example of a secondary battery. [Figure 5] 5A to 5C are diagrams illustrating examples of secondary batteries. [Figure 6] 6(A) and 6(B) are diagrams illustrating an example of a secondary battery. [Figure 7] Figures 7(A) and 7(B) are diagrams illustrating a coin-type secondary battery, and Figure 7(C) is a diagram illustrating charging and discharging of a secondary battery. [Figure 8] 8(A) to 8(D) are diagrams illustrating a cylindrical secondary battery. [Figure 9] 9(A) and 9(B) are diagrams illustrating an example of a secondary battery. [Figure 10] 10A1 to 10B2 are diagrams illustrating an example of a secondary battery. [Figure 11] 11(A) and 11(B) are diagrams illustrating an example of a secondary battery. [Figure 12] FIG. 12 is a diagram illustrating an example of a secondary battery. [Figure 13] 13A to 13C are diagrams illustrating a laminated secondary battery. [Figure 14] 14(A) and 14(B) are diagrams illustrating a laminated secondary battery. [Figure 15] FIG. 15 is a diagram showing the appearance of a secondary battery. [Figure 16] FIG. 16 is a diagram showing the appearance of a secondary battery. [Figure 17] 17A to 17C are diagrams illustrating a method for manufacturing a secondary battery. [Figure 18] 18A to 18G are diagrams illustrating examples of electronic devices. [Figure 19] 19A to 19C are diagrams illustrating examples of electronic devices. [Figure 20] FIG. 20 is a diagram illustrating an example of an electronic device. [Figure 21] 21A to 21C are diagrams illustrating examples of electronic devices. [Figure 22]22A to 22C are diagrams showing examples of electronic devices. [Figure 23] 23(A) to 23(C) are diagrams illustrating an example of a vehicle. [Figure 24] FIG. 24 is a photograph of the GO film prepared in Example 1. [Figure 25] FIG. 25 shows the Raman spectrum of the sample analyzed in Example 1. [Figure 26] FIG. 26 shows the FT-IR spectrum of the sample analyzed in Example 1. [Figure 27] FIG. 27 shows the XRD spectrum of the sample analyzed in Example 1. [Figure 28] FIG. 28 shows the surface resistivity of the sample analyzed in Example 1. [Figure 29] FIG. 29 shows the XRD spectrum of the sample analyzed in Example 1. [Figure 30] FIG. 30 shows the FT-IR spectrum of the sample analyzed in Example 1. [Figure 31] FIG. 31 is a surface SEM image of the sample analyzed in Example 1. [Figure 32] Figure 32(A) is a cross-sectional SEM image of the sample prepared in Example 1. Figure 32(B) is a diagram in which part of the reduced GO in Figure 32(A) is traced with a black line for easier viewing. [Figure 33] 33(A) is a discharge curve of the sample prepared in Example 2. FIG. 33(B) is a graph showing the rate characteristics of the sample prepared in Example 2. [Figure 34] 34(A) shows the discharge curve per weight of the sample prepared in Example 2. FIG. 34(B) shows the discharge curve per volume of the sample prepared in Example 2. [Figure 35] 35(A) and 35(B) are discharge curves showing the rate characteristics of the sample prepared in Example 2. [Figure 36] 36(A) and 36(B) are graphs showing the rate characteristics of the sample prepared in Example 3. [Figure 37]37(A) and 37(B) are graphs showing the rate characteristics of the sample prepared in Example 3. [Figure 38] 38(A) and 38(B) are graphs showing the rate characteristics of the sample prepared in Example 3. [Figure 39] 39(A) to 39(C) are graphs showing the cycle characteristics of the sample prepared in Example 3. [Figure 40] 40(A) and 40(B) are graphs showing the rate characteristics of the sample prepared in Example 3. [Figure 41] 41(A) and 41(B) are graphs showing the charging curves of the samples prepared in Example 3. [Figure 42] 42(A) and 42(B) are SEM images of the surface of the sample prepared in Example 4. [Figure 43] FIG. 43(A) shows the charge / discharge curve of the sample prepared in Example 4, and FIG. 43(B) shows the discharge energy retention rate of the sample prepared in Example 4. [Figure 44] FIG. 44 is a graph showing the cycle characteristics of the sample prepared in Example 4. [Figure 45] FIG. 45 is a graph showing the cycle characteristics of the sample prepared in Example 4. [Figure 46] FIG. 46(A) shows the charge / discharge curve of the sample prepared in Example 4, and FIG. 46(B) shows the discharge energy retention rate of the sample prepared in Example 4. [Figure 47] FIG. 47(A) shows the charge / discharge curve of the sample prepared in Example 4, and FIG. 47(B) shows the discharge energy retention rate of the sample prepared in Example 4. [Figure 48] FIG. 48(A) shows the charge / discharge curve of the sample prepared in Example 4, and FIG. 48(B) shows the discharge energy retention rate of the sample prepared in Example 4. [Figure 49] FIG. 49 is a graph showing the capacitance per volume of the sample prepared in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0025] The embodiments of the present invention will be described in detail below with reference to the drawings. The present invention is not limited to these descriptions, and various modifications in form and details are possible by those skilled in the art. Therefore, the present invention should not be construed as being limited to the following description of the embodiments. It is not something that can be done.

[0026] In each figure described in this specification, the size and thickness of each element such as a film, layer, substrate, and region are The dimensions may be exaggerated for clarity of explanation. The components are not limited by their size, nor are they limited by the relative sizes of each component. .

[0027] In this specification, ordinal numbers such as first, second, etc. are used for convenience. It does not indicate the order of processes or the order of lamination. " can be appropriately replaced with "second" or "third" etc. The ordinal numbers described in the specification and the like and the ordinal numbers used to identify one aspect of the present invention are There may be cases where they do not match.

[0028] In the configuration of the present invention described in this specification, etc., the same parts or parts having similar functions The same reference numerals are used for the components in different drawings, and the repeated explanations will be omitted. When referring to parts with similar functions, the hatch pattern is the same and no special reference numeral is attached. There may not be.

[0029] In this specification and the like, both the positive electrode and the negative electrode for the electricity storage device may be collectively referred to as the electrode. In this case, the electrode refers to at least one of the positive electrode and the negative electrode. .

[0030] In this specification and the like, a secondary battery using a positive electrode and a positive electrode active material of one embodiment of the present invention In some cases, lithium metal is used for the counter electrode. However, other materials such as graphite and lithium titanate may be used for the negative electrode. The desirable properties of the positive electrode of one embodiment are not affected by the material of the negative electrode.

[0031] (Embodiment 1) In this embodiment, a method for manufacturing a positive electrode for a secondary battery according to one embodiment of the present invention will be described with reference to FIGS. An example of this will be described.

[0032] <Step S11> First, in step S11, the positive electrode active material, conductive material, binder, and current collector are mixed. Prepare the body and the solvent for mixing.

[0033] [Cathode active material] The positive electrode active material may have an olivine type crystal structure, a layered rock salt type crystal structure, or a spinel type For example, LFP, manganese phosphate, etc. can be used. Lithium ferrous oxide (LiMnPO4), lithium ferrous oxide (LiFeO2), lithium cobalt oxide ( LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn 2O4), V2O5, Cr2O5, MnO2, etc. Lithium cobalt oxide in which some of the cobalt is replaced by manganese, and lithium cobalt oxide in which some of the cobalt is replaced by nickel Lithium cobalt oxide, Lithium nickel-cobalt-manganese oxide, Nickel-cobalt- Lithium aluminum oxide or the like may also be used. A mixture of these may also be used. Additives such as magnesium, fluorine and other halogens may be added to the electrode active material. .

[0034] In particular, LFP has high safety, excellent cycle characteristics, a wide plateau, and is compatible with cobalt. It is preferable because it has the advantage of reducing costs in that it contains relatively inexpensive iron.

[0035] Lithium cobalt oxide has a large capacity and is more stable in the atmosphere than lithium nickel oxide. It is preferable because it has advantages such as thermal stability compared to lithium nickel oxide.

[0036] In addition, lithium-containing materials with a spinel-type crystal structure containing manganese, such as LiMn2O4, The materials include lithium nickel oxide (LiNiO2 and LiNi 1-x M x O2(0 <x<1)(M It is preferable to mix Co, Al, etc.) with the above composition. can be improved.

[0037] In addition, the positive electrode active material is a compound having the composition formula Li a Mn b M c O d Lithium-manganese can be expressed as A manganese composite oxide can be used. Here, element M is selected from elements other than lithium and manganese. The selected metal element, silicon, or phosphorus is preferably used, and nickel is preferred. Further, when measuring the entire particle of the lithium manganese composite oxide, When the value is 0 <a / (b+c)<2、かつc>0 and 0.26≦(b+c) / d<0.5, It is preferable that the metal, silicon, and The composition of phosphorus, etc. is measured using, for example, an ICP-MS (inductively coupled plasma mass spectrometer). ​The oxygen composition of the entire particle of the lithium manganese composite oxide can be determined by, for example, ED It can be measured using energy dispersive X-ray analysis (ICP- In combination with MS analysis, molten gas analysis and XAFS (X-ray absorption fine structure) analysis were used to evaluate the valence. The lithium manganese composite oxide is a compound oxide containing at least lithium It refers to oxides containing thium and manganese, and also contains chromium, cobalt, aluminum, nickel, Iron, magnesium, molybdenum, zinc, indium, gallium, copper, titanium, niobium, silicon It may contain at least one element selected from the group consisting of silicon, phosphorus, etc. stomach.

[0038] [Conductive material] Examples of conductive materials include natural graphite, artificial graphite such as mesocarbon microbeads, and carbon fiber. Examples of carbon fibers that can be used include mesophase pitch carbon fibers, etc. Carbon fibers such as isotropic pitch-based carbon fibers can be used. Carbon nanofibers and carbon nanotubes can be used. The tube can be fabricated by, for example, vapor phase growth. Carbon black (acetylene black (AB) etc.), graphite particles, graphite Carbon materials such as phene and fullerene can be used. Also, for example, copper, nickel , aluminum, silver, gold, and other metal powders and metal fibers, conductive ceramic materials, etc. It is possible.

[0039] It is particularly preferable to use graphene and graphene compounds as the conductive material. GO is used as the initial material, and reduced GO is obtained through the reduction process described below. preferable.

[0040] In this specification and the like, graphene compounds include multi-layer graphene, multi-graphene, GO, Multilayer GO, multi-GO, reduced GO, reduced multilayer GO, reduced multi-GO, etc. Graphene compounds include those that contain carbon and have a shape such as a flat plate or sheet, and are made of 6 carbon atoms. It refers to a molecule having a two-dimensional structure formed by a membered ring. It is also preferable that the molecule has a curved shape. It is preferable that the carbon sheet has a functional group. The compound may be rolled into a shape similar to carbon nanofibers.

[0041] In this specification, GO is a material that contains carbon and oxygen, has a sheet-like shape, and has functional groups, particularly It refers to a compound having an epoxy group, a carboxy group, or a hydroxy group.

[0042] In this specification and the like, reduced GO refers to GO that contains carbon and oxygen and has a sheet-like shape. It has a two-dimensional structure formed by six-membered carbon rings. It can also be called a carbon sheet. Reduced GO works well as a single sheet, but multiple sheets can also be stacked. is a carbon concentration greater than 80 atomic % and an oxygen concentration greater than 2 atomic %. It is preferable that the carbon concentration and the acid content are 5 atomic % or less. By adjusting the concentration of the element, even a small amount can function as a highly conductive material. The Raman spectrum of the decomposed GO has a G / D ratio of 1 or more. It is preferable that the reduced GO having such an intensity ratio has high conductivity even in a small amount. It can function as a highly conductive material.

[0043] In this embodiment, GO is prepared as the conductive material, and this is reduced in a later process. The conductive material in the completed positive electrode is reduced GO.

[0044] Graphene compounds have excellent electrical properties, such as high conductivity, as well as high flexibility and high In addition, graphene may have excellent physical properties such as high mechanical strength. The compound has a sheet-like shape. The graphene compound may have a curved surface, and the bonding It allows for surface contact with low contact resistance. In addition, even if it is thin, it can have very high conductivity, Therefore, a conductive path can be efficiently formed in the active material layer with a small amount of graphene. By using the compound as the conductive material, it is possible to increase the contact area between the active material and the conductive material. It should be noted that when the graphene compound is attached to at least a part of the active material particles, It is also preferable that the graphene compound is layered on at least a part of the active material particles. It is also preferable that the shape of the graphene compound coincides with at least a part of the shape of the active material particles. The shape of the active material particles is preferably, for example, the irregularities of a single active material particle. The term also refers to the unevenness formed by a plurality of active material particles. It is preferable that the holes surround at least a part of the material particles. It may be empty.

[0045] When using active material particles with a small particle size, for example, active material particles with a particle size of 1 μm or less, The specific surface area of ​​the active material particles is large, and therefore more conductive paths are required to connect the active material particles together. In such cases, graphene compounds that can efficiently form conductive paths even in small amounts are used. It is preferable to use it.

[0046] Because of the above-mentioned properties, the secondary battery that requires rapid charging and rapid discharging is The use of phene compounds as conductive materials is particularly effective. For example, Dual-purpose secondary batteries, secondary batteries for drones, etc. require rapid charging and rapid discharging characteristics In addition, there are cases where quick charging characteristics are required for mobile electronic devices. The fast discharge may be referred to as a high rate charge and a high rate discharge. For example, 1C , 2C, or 5C or higher charging and discharging.

[0047] [Binder] As the binder, it is preferable to use, for example, a water-soluble polymer. For example, polysaccharides can be used. Examples of polysaccharides include starch and carboxymethyl cellulose. CMC, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, Cellulose derivatives such as diacetyl cellulose and regenerated cellulose can be used. Furthermore, it is more preferable to use these water-soluble polymers in combination with the rubber material described below. It's nice.

[0048] In addition, styrene-butadiene rubber (SBR) and styrene-isoprene are used as binders. Styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene Rubber materials such as olefin-diene copolymers can be used. Rubber may be used.

[0049] Alternatively, the binder may be polystyrene, polymethyl acrylate, or polymethyl methacrylate. Polymethylmethacrylate (PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), poly Ethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride, Polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, poly Ethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylo Nitrile (PAN), Ethylene Propylene Diene Polymer, Polyvinyl Acetate, Nitrocel It is preferable to use a material such as loin.

[0050] The binder may be used in combination with two or more of the above.

[0051] For example, a material having a particularly excellent viscosity adjusting effect may be used in combination with other materials. For example, rubber materials have excellent adhesive strength and elasticity, but it is difficult to adjust the viscosity when mixed with a solvent. In such cases, for example, mixing with a material that has a particularly excellent viscosity adjusting effect can As a material having a particularly excellent viscosity adjusting effect, for example, a water-soluble polymer is preferably used. Furthermore, examples of water-soluble polymers that are particularly effective in adjusting viscosity include the aforementioned polysaccharides, such as carbohydrates. Hydroxymethylcellulose (CMC), methylcellulose, ethylcellulose, hydroxypropyl cellulose derivatives such as propyl cellulose, diacetyl cellulose, and regenerated cellulose In this specification, starch refers to a polymerized form of α-glucose. The higher the degree of polymerization, the better the binder it functions as. It is preferably 0 or more, and more preferably 1000 or more. It does not matter whether it is gelatinized or not. The ratio and type of plant used as raw material are not important. It may contain impurities such as sugars, other polysaccharides such as cellulose, phosphoric acid, and amino acids.

[0052] The cellulose derivatives such as carboxymethyl cellulose are, for example, By converting cellulose into salts such as sodium salts or ammonium salts, the solubility increases, It is easier to exert its effect as a viscosity adjuster. The increased solubility makes it easier to make electrode slurry. When preparing a substrate, it is also possible to improve the dispersibility of the active material and other components. In this case, the cellulose and cellulose derivatives used as binders for electrodes include These salts are also included.

[0053] Water-soluble polymers stabilize viscosity by dissolving in water, and also act as active materials and binders. Other materials to be combined, such as styrene butadiene rubber, are stably dispersed in aqueous solution. In addition, since it has functional groups, it can be easily and stably adsorbed onto the surface of the active material. It is expected that cellulose derivatives such as carboxymethyl cellulose will For example, many materials have functional groups such as hydroxyl groups and carboxyl groups, and because of these functional groups, It is expected that the molecules will interact with each other and widely cover the surface of the active material.

[0054] When the binder that covers or contacts the surface of the active material forms a film, it is called a passive film. It is expected that the passive film will also play a role in suppressing the decomposition of the electrolyte. It is a film with no electrical conductivity or extremely low electrical conductivity, and is When a dynamic membrane is formed, it is possible to suppress the decomposition of the electrolyte at the battery reaction potential. In addition, the passive film suppresses electrical conductivity while allowing lithium ions to conduct. And even more desirable.

[0055] When polysaccharides such as starch are used as binders, they must be subjected to a reduction process, which will be described later. Therefore, the completed positive electrode is preferably at least partially reduced by the It is preferable to have a polysaccharide that has been reduced by reducing the polysaccharide. The reduced polysaccharide has improved conductivity and is a positive electrode active material. This allows for better conductive paths to be formed in the porous layer together with the conductive material.

[0056] The combination of polysaccharide as a binder and GO as a conductive material is particularly effective. Alternatively, the functional groups of the reduced polysaccharide and the functional groups of the GO or reduced GO may be depolymerized. Water condensation occurs, forming covalent bonds, and even a small amount functions as a better binder and conductive material. There are cases where this happens.

[0057] [Current collector] The current collector may be made of metals such as stainless steel, gold, platinum, aluminum, titanium, or any of these metals. The material used for the positive electrode current collector is a highly conductive material such as an alloy. It is preferable that the material does not dissolve at the potential of the electrode. It is recommended to use an aluminum alloy containing elements such as aluminum and molybdenum that improve heat resistance. Alternatively, it may be formed from a metal element that reacts with silicon to form silicide. Metal elements that react with silicon to form silicides include zirconium, titanium, Hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, The current collectors are available in foil, plate, sheet, mesh, and punched metal shapes. The current collector may have a thickness of 5 μm or less, and may have an expanded metal shape or other suitable shape. It is recommended to use one with a thickness of 30 μm or less.

[0058] 〔solvent〕 The solvent for mixing is preferably polar. Examples of polar solvents include water, NMP (N -methylpyrrolidone), methanol, ethanol, acetone, DMF (N,N-dimethyl In particular, water is highly polar and has little impact on the environment and the human body. Furthermore, water may be mixed with other materials to form a solvent for mixing. The amount of water contained is preferably 10% by volume or more, more preferably 50% by volume or more, and more preferably 90% by volume or more. is more preferable.

[0059] <Step S12> Next, the binder, the conductive material, and the positive electrode active material are mixed. The order of mixing is not limited, but for example, As shown in FIG. 1, first, the binder and the solvent are mixed (step S12a), and then the conductive material is mixed. (Step S12b), and then the positive electrode active material can be mixed (Step S12 c) In step S12c, it is preferable to add a solvent to adjust the viscosity.

[0060] Alternatively, as shown in FIG. 2, the positive electrode active material and the solvent are first mixed (step S12d), and then the The electrical materials are mixed (step S12e), and then the binder can be mixed (step In step S12f, it is preferable to add a solvent to adjust the viscosity.

[0061] <Step S13> As described above, the binder, conductive material, and positive electrode active material are mixed with a solvent to form a slurry. (Step S13).

[0062] <Step S14> Next, in step S14, the slurry is applied onto the current collector. The amount of support can be adjusted by adjusting the blade gap during coating. It is possible.

[0063] <Step S15> Next, in step S15, the applied slurry is dried to form an electrode layer. The current collector and electrode layer may be processed into different shapes, for example by punching.

[0064] <Step S16> Next, in step S16, the electrode layer is subjected to reduction treatment. The reduction method is chemical reduction. or thermal reduction may be applied.

[0065] [Chemical reduction] Chemical reduction refers to treatment with a reducing agent. Reducing agents include ascorbic acid and other Organic acids, hydrogen, sulfur dioxide, sulfurous acid, sodium sulfite, sodium bisulfite, sulfurous acid Ammonium or phosphorous acid can be used.

[0066] When using ascorbic acid as a reducing agent, first dissolve the ascorbic acid in a solvent and then The starting solution (ascorbic acid solution) is prepared. The solvents used are water, a mixture of water and NMP, and ethanol. The solution can be treated with ethanol, a mixture of water and ethanol, etc. The current collector and electrode layer prepared in step 15 are immersed in the solution. This treatment is carried out for, for example, 30 minutes to 10 hours. The chemical reduction time can be shortened by heating. For example, it can be heated to a temperature above room temperature and below 100°C, for example, about 60°C. degree is preferred.

[0067] [Thermal reduction] Thermal reduction refers to a process of heating the current collector and electrode layer prepared in step S15. For heating, for example, a glass tube oven can be used. The glass tube oven can be heated under reduced pressure of about 1 kPa.

[0068] The optimum heating temperature and heating time vary depending on the conductive material and binder material. When using GO as the conductive material and PVDF as the binder, it is necessary to ensure that GO is sufficiently reduced and that PVD It is preferable that the temperature is at a level that does not adversely affect F. Specifically, it is 125°C or higher and 20 The temperature is preferably 0°C or lower. If the temperature is lower than 100°C, the reduction of GO may not proceed sufficiently. Temperatures above 50°C may have a negative effect on PVDF, causing the slurry to peel off easily from the current collector. The heating time is preferably between 1 hour and 20 hours. If the heating time is less than 1 hour, the GO may not be fully dissolved. On the other hand, if the heating time exceeds 20 hours, productivity will decrease.

[0069] In addition, when GO is used as the conductive material and starch is used as the binder, the tensile strength is higher than when the binder is PVDF. Specifically, it is preferable to heat the material at a temperature of 200°C or higher and 300°C or lower. In order to fully reduce and carbonize the starch (see Non-Patent Document 4), it is heated at 200°C or higher. On the other hand, if the temperature is too high, special heating equipment will be required, which will increase costs. The heating time is preferably 1 hour or more and 20 hours or less. If the heating time is less than 1 hour, GO may not be reduced sufficiently. Productivity decreases when the work hours exceed 20 hours.

[0070] The reduction treatment can be performed by at least one of chemical reduction and thermal reduction. It is more preferable to carry out both the chemical reduction and the thermal reduction. In this case, the chemical reduction may be followed by the thermal reduction. Alternatively, chemical reduction may be performed after thermal reduction. For example, in step S16a shown in FIG. Chemical reduction can be performed, followed by thermal reduction as step S16b.

[0071] The functional groups that are easily reduced differ between chemical reduction and thermal reduction. The carbonyl group (C=O) and carboxyl group (-COOH) of GO are converted by the addition of hydroxyl groups. On the other hand, thermal reduction is effective in reducing the hydroxyl groups (-OH) in GO by dehydration. Therefore, by performing both chemical reduction and thermal reduction, reduction can be achieved more efficiently. This can increase the conductivity of the reduced GO.

[0072] <Step S17> Next, as shown in step S17 of FIG. 2, the product that has undergone the reduction treatment may be pressed. For example, a calender roll can be used for pressing. The density can be improved.

[0073] <Step S18> The electrode thus manufactured is used as a positive electrode according to one embodiment of the present invention (Step S18).

[0074] As described above, by preparing a slurry using water as a solvent, it is possible to produce a cathode more safely and inexpensively than before. In addition, graphene and graphene compounds can be used as conductive materials. Therefore, a positive electrode with high rate characteristics can be manufactured.

[0075] This embodiment can be used in combination with other embodiments.

[0076] (Embodiment 2) In this embodiment, an example of a secondary battery of one embodiment of the present invention will be described with reference to FIGS. do.

[0077] <Configuration example 1 of secondary battery> The following description will be given taking as an example a secondary battery in which a positive electrode, a negative electrode, and an electrolyte are enclosed in an exterior body. do.

[0078] [Positive electrode] The positive electrode used is the positive electrode described in the previous embodiment. An example of a cross-sectional structure in the case where graphene and a graphene compound are used as the conductive material will be described.

[0079] 3(A) shows a vertical cross-sectional view of the active material layer 200. The active material layer 200 is made of granular positive electrode active material. 100, graphene and graphene compounds 201 as conductive materials, and a binder (as shown in the figure) Here, graphene and graphene compounds 201 are in the form of a sheet or It is preferable that the graphene and graphene compound 201 have a flat plate shape. is composed of multiple multi-layer graphenes, or (and) multiple graphene sheets that overlap each other. The shape may be a flat or granular shape.

[0080] In the vertical cross section of the active material layer 200, as shown in FIG. 3(A), The sheet-like graphene and graphene compound 201 are dispersed approximately uniformly in the solution. Graphene and graphene compound 201 are shown schematically in (A) and (B) of FIG. Although it is represented by a thick line, it is actually a thin film having a thickness of a single layer or multiple layers of carbon molecules. The graphene and graphene compound 201 partially covers a plurality of particles of the positive electrode active material 100. or formed so as to be stuck to the surface of a plurality of granular positive electrode active materials 100. Therefore, they are in surface contact with each other.

[0081] Here, a plurality of graphenes and graphene compounds are bonded to each other to form a mesh-like structure. Graphene compound sheet (hereinafter referred to as graphene compound net or graphene net) When the active material is covered with a graphene net, the graphene net The binder can also function as a binder that binds the active materials together. This allows for a reduction in the amount of electrode material, or even for it to be used at all, reducing the electrode volume and weight. The ratio of the active material can be increased, i.e., the capacity of the secondary battery can be increased. It is possible.

[0082] Here, GO is used as graphene and graphene compounds 201, and it is mixed with an active material. It is preferable to reduce the layer that will become the active material layer 200 after it is formed. By using GO, which has extremely high dispersibility in polar solvents, to form the crystalline silicon compound 201, The graphene and the graphene compound 201 are distributed approximately uniformly inside the active material layer 200. The solvent is evaporated from the dispersion medium containing uniformly dispersed GO, and G In order to reduce O, the graphene and graphene compound 201 remaining in the active material layer 200 are partially overlapping and dispersed to the extent that they are in surface contact with each other, forming a three-dimensional conductive path. The reduction of GO may be carried out by, for example, heat treatment or by reduction. This may be carried out by treatment with a base agent, but it is more preferable to carry out both heat treatment and treatment with a reducing agent.

[0083] Therefore, unlike granular conductive materials such as AB, which are in point contact with the active material, graphene and graphene The silicon compound 201 allows for surface contact with low contact resistance, and is therefore more effective than ordinary conductive materials. The electrical conduction between the small amount of granular positive electrode active material 100 and graphene and graphene compounds 201 was Therefore, the ratio of the positive electrode active material 100 in the active material layer 200 can be improved. This allows the discharge capacity of the secondary battery to be increased. do.

[0084] In addition, by using a spray dryer, the entire surface of the active material is covered with a conductive material in advance. The graphene and graphene compound are formed as a coating film, and the graphene and graphene compound are further formed between the active materials. Conductive paths can also be formed with graphene and graphene compounds.

[0085] [Negative electrode] The negative electrode has a negative electrode active material layer and a negative electrode current collector. The negative electrode active material layer contains a conductive material and It may contain a binder.

[0086] [Negative electrode active material] As the negative electrode active material, for example, an alloy-based material or a carbon-based material can be used.

[0087] As a negative electrode active material, it is possible to carry out charge-discharge reactions by alloying and dealloying reactions with lithium. Any suitable element can be used, such as silicon, tin, gallium, aluminum, Rumanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. Materials containing at least one of these elements can be used. These elements have a large capacity compared to carbon. Silicon has a particularly high theoretical capacity of 4200mAh / g. It is preferable to use silicon. Alternatively, compounds containing these elements may be used. For example, SiO, Mg2Si, Mg2Ge, SnO, SnO2, Mg2Sn, SnS2, V 2Sn3, FeSn2, CoSn2, Ni3Sn2, Cu6Sn5, Ag3Sn, Ag3 Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7, CoSb3, I nSb, SbSn, etc. Here, the charge / discharge reaction occurs due to alloying and dealloying reactions with lithium. Elements capable of undergoing a reaction and compounds containing such elements are sometimes called alloy materials. do.

[0088] In this specification and the like, SiO refers to, for example, silicon monoxide. Alternatively, SiO refers to SiO y Here, y preferably has a value close to 1. For example, y can be expressed as A value between 0.2 and 1.5 is preferred, and a value between 0.3 and 1.2 is more preferred.

[0089] Carbon materials include graphite, easily graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). carbon nanotubes, graphene, carbon black, etc. may be used. .

[0090] Examples of graphite include artificial graphite and natural graphite. Examples include carbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite. Here, as the artificial graphite, spherical graphite having a spherical shape can be used. For example, the MCMB may have a spherical shape, which is preferable. It is relatively easy to reduce the particle size, which is sometimes preferable. Examples include flake graphite and spherical natural graphite.

[0091] Graphite is formed when lithium ions are inserted into graphite (forming a lithium-graphite intercalation compound) It shows a low potential similar to that of lithium metal (0.05V to 0.3V vs. Li / Li + This allows the lithium-ion secondary battery to exhibit a high operating voltage. Furthermore, graphite has a relatively high capacity per unit volume, a relatively small volume expansion, and is inexpensive. It is preferable because it has advantages such as higher safety compared to metallic lithium.

[0092] In addition, titanium dioxide (TiO2) and lithium titanium oxide (Li4T i5O 12 ), lithium-graphite intercalation compound (Li x C6), niobium pentoxide (Nb2O5) Oxides such as tungsten oxide (WO2) and molybdenum oxide (MoO2) can be used. can.

[0093] In addition, the negative electrode active material is a composite nitride of lithium and transition metals, which has a Li3N structure. Li 3-x M x N (M=Co, Ni, Cu) can be used. For example, Li 2.6 Co 0.4 N3 has a large charge / discharge capacity (900mAh / g, 1890mAh / cm 3 ) And preferable.

[0094] When a composite nitride of lithium and a transition metal is used, the negative electrode active material contains lithium ions, The positive electrode active material is a combination of materials such as V2O5 and Cr3O8 that do not contain lithium ions. It is preferable that a material containing lithium ions is used as the positive electrode active material. By first removing the lithium ions contained in the positive electrode active material, A complex nitride of lithium and a transition metal can be used.

[0095] In addition, a material that undergoes a conversion reaction can also be used as the negative electrode active material. , cobalt oxide (CoO), nickel oxide (NiO), iron oxide (FeO), etc. A transition metal oxide that does not form an alloy with the metal may be used as the negative electrode active material. Further materials that can be produced include Fe2O3, CuO, Cu2O, RuO2, Cr2O3, etc. oxide, CoS 0.89 , NiS, CuS and other sulfides, Zn3N2, Cu3N, Ge3 Nitrides such as N4, phosphides such as NiP2, FeP2, CoP3, FeF3, BiF3, etc. It also occurs with fluoride.

[0096] The conductive material and binder that can be contained in the negative electrode active material layer can be the same as those contained in the positive electrode active material layer. The same materials as the conductive material and binder that can be used can be used.

[0097] [Negative electrode current collector] The negative electrode current collector can be made of the same material as the positive electrode current collector. It is preferable to use a material that does not alloy with carrier ions such as lithium.

[0098] [Electrolyte] The electrolytic solution contains a solvent and an electrolyte. The solvent for the electrolytic solution is preferably an aprotic organic solvent. For example, ethylene carbonate (EC), propylene carbonate (PC), ethylene carbonate, chloroethylene carbonate, vinylene carbonate, gamma-butyrolactone lactone, γ-valerolactone, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate, ethyl acetate methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1 ,3-dioxane, 1,4-dioxane, dimethoxyethane (DME), dimethyl sulfone oxide, diethyl ether, methyl diglyme, acetonitrile, benzonitrile, tetrahydrofuran One of tetrahydrofuran, sulfolane, sultone, etc., or two or more of these Combinations and ratios may be used.

[0099] In addition, a flame-retardant and non-volatile ionic liquid (room-temperature molten salt) is used as the solvent for the electrolyte. By using one or more batteries, the internal temperature of the secondary battery can be increased due to an internal short circuit or overcharging. Even if the battery is not fully charged, it can prevent the secondary battery from exploding or catching fire. Ionic liquids are made up of cations and anions. The organic cations used in the electrolyte include quaternary cations. Ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, etc. aliphatic onium cations such as imidazolium cations and pyridinium cations Aromatic cations are also used as anions in electrolytes. Anions, monovalent methide anions, fluorosulfonate anions, perfluoroalkyl Sulfonate anion, tetrafluoroborate anion, perfluoroalkylborate anion, hexafluorophosphate anion, or perfluoroalkylphosphate anions, etc.

[0100] The electrolyte to be dissolved in the solvent is, for example, LiPF6, LiClO4, Li AsF6, LiBF4, LiAlCl4, LiSCN, LiBr, LiI, Li2SO4 , Li2B 10 Cl 10 , Li2B 12 Cl 12 , LiCF3SO3, LiC4F9SO 3, LiC(CF3SO2)3, LiC(C2F5SO2)3, LiN(CF3SO2) 2. Lithium such as LiN(C4F9SO2)(CF3SO2) and LiN(C2F5SO2)2 Use one or more of these ammonium salts in any combination and ratio. can be done.

[0101] The electrolyte used in secondary batteries is free from granular dust and elements other than the constituent elements of the electrolyte (hereinafter simply referred to as "impurities"). It is preferable to use a highly purified electrolyte solution with a low content of ammonium hydroxide. Specifically, the weight ratio of impurities to the electrolyte is 1% or less, preferably 0.1% or less, more preferably It is preferably 0.01% or less.

[0102] In addition, the electrolyte contains vinylene carbonate, propane sultone (PS), and tert-butyl ether. Benzene (TBB), Fluoroethylene carbonate (FEC), Lithium bis(oxalate) Lithium borate (LiBOB), as well as dinitriles such as succinonitrile and adiponitrile Additives such as compounds may be added. The concentration of the added material is, for example, It should be between 0.1 wt% and 5 wt%.

[0103] Alternatively, a polymer gel electrolyte may be used in which a polymer is swollen with an electrolytic solution.

[0104] The use of polymer gel electrolytes increases safety against leakage, etc. It is possible to make the device thinner and lighter.

[0105] The polymers that can be gelled include silicone gel, acrylic gel, acrylonitrile gel, Polyethylene oxide gel, polypropylene oxide gel, fluorine polymer Gel or the like can be used.

[0106] Examples of polymers include polymers having a polyalkylene oxide structure such as PEO, PVDF, polyacrylonitrile, etc., and copolymers containing these may be used. For example, P, a copolymer of PVDF and hexafluoropropylene (HFP), VDF-HFP can be used. The polymer formed has a porous shape. That's fine.

[0107] In addition, instead of the electrolyte solution, solid electrolytes containing inorganic materials such as sulfides and oxides, and P A solid electrolyte containing a polymer material such as an EO system can be used. In this case, the installation of separators and spacers is not required. This eliminates the risk of leakage and dramatically improves safety.

[0108] [Separator] The secondary battery preferably has a separator. The separator may be made of, for example, paper. , nonwoven fabric, glass fiber, ceramics, or nylon (polyamide), vinylon (poly Vinyl alcohol fiber), polyester, acrylic, polyolefin, polyurethane The separator can be made of synthetic fibers or the like. It is preferable that the electrode be processed into a shape such that it wraps around either the positive electrode or the negative electrode.

[0109] The separator may have a multi-layer structure. For example, the separator may be made of an organic material such as polypropylene or polyethylene. The material film is made of ceramic material, fluorine material, polyamide material, or a mixture of these. As a ceramic material, for example, aluminum oxide can be used. Examples of the fluorine-based material include fluorine particles, silicon oxide particles, etc. PVDF, polytetrafluoroethylene, etc. can be used. For example, nylon, aramid (meta-aramid, para-aramid), etc. can be used. can.

[0110] Coating with ceramic materials improves oxidation resistance, making it suitable for separators during high-voltage charging and discharging. This can suppress the deterioration of the battery and improve the reliability of the secondary battery. By coating, the separator and electrodes can be more easily attached to each other, improving output characteristics. Coating polyamide materials, especially aramid, improves heat resistance, which contributes to the safety of secondary batteries. Safety can be improved.

[0111] For example, a polypropylene film is coated on both sides with a mixture of aluminum oxide and aramid. Alternatively, aluminum oxide may be applied to the surface of the polypropylene film that comes into contact with the positive electrode. Alternatively, the surface of the negative electrode that comes into contact with the carbon black may be coated with a mixed material of carbon black and aramid, and then coated with a fluorine-based material.

[0112] By using a multilayer separator, the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin. Since the temperature can be maintained, the capacity per volume of the secondary battery can be increased.

[0113] [Exterior body] The exterior of the secondary battery is made of a metal material such as aluminum or a resin material. Also, a film-like outer casing can be used. For example, polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc. On the film made of the material, a highly flexible metal such as aluminum, stainless steel, copper, or nickel is A metal thin film is then formed on the metal thin film, and the outer surface of the exterior body is made of a polyamide resin or polyester. A three-layer film having an insulating synthetic resin film such as a vinyl resin can be used.

[0114] <Configuration example 2 of secondary battery> As an example of the configuration of a secondary battery, the configuration of a secondary battery using a solid electrolyte layer will be described below. Reveal.

[0115] As shown in FIG. 4A, a secondary battery 400 of one embodiment of the present invention includes a positive electrode 410, a solid electrolyte layer 420 and a negative electrode 430 .

[0116] The positive electrode 410 includes a positive electrode current collector 413 and a positive electrode active material layer 414. The positive electrode active material layer 414 has a positive electrode active material 411 and a solid electrolyte 421. The material may include a binder.

[0117] The solid electrolyte layer 420 includes a solid electrolyte 421. The solid electrolyte layer 420 is connected to the positive electrode 410. The negative electrode 430 is located between the positive electrode active material 411 and the negative electrode active material 431. It is an area.

[0118] The negative electrode 430 includes a negative electrode current collector 433 and a negative electrode active material layer 434. The negative electrode active material layer 434 has a negative electrode active material 431 and a solid electrolyte 421. When metallic lithium is used for the negative electrode 430, 4(B), the negative electrode 430 can be formed without the solid electrolyte 421. When metallic lithium is used for the electrode 430, the energy density of the secondary battery 400 can be improved. This is preferable.

[0119] As the solid electrolyte 421 included in the solid electrolyte layer 420, for example, sulfide-based solid electrolytes, oxide-based solid electrolytes, halide-based solid electrolytes, etc. can be used. For sulfide-based solid electrolytes, thioborosilicon-based (Li

[0120] GeP2S 10 、Li 12 、Li 3.25 Ge 0.25 P 0.75 S4, etc.), sulfide glasses (70Li2S·30P2S5, 30Li2 S·26B2S3·44LiI, 63Li2S·36SiS2·1Li3PO4, 57L i2S·38SiS2·5Li4SiO4, 50Li2S·50GeS2, etc.), sulfide crystallized glasses (Li7P3S 、Li 11 、Li 3.25 P 0.95 S4, etc.) are included. Sulfide-based solid electrolytes have advantages such as some materials having high conductivity, being synthesizable at low temperatures, and the conductive path being easily maintained even after repeated charge and discharge due to relatively softness.

[0121] For oxide-based solid electrolytes, materials having a perovskite-type crystal structure (La 2 / 3-z Li 3z TiO3 (0<z<2 / 3), etc.), materials having a NASICON-type crystal structure (Li1 +A Al A Ti 2-A (PO4)3 (0<A<1), etc.), materials having a garnet-type crystal structure (Li7La3Zr2O 、etc.), materials having a LISICON-type crystal structure (Li1 12 4ZnGe4O 、etc.), oxide glasses (Li3PO4-Li4SiO4, 50Li4S 16 iO4·50Li3BO3, etc.), oxide crystallized glasses (Li 、Li 1.07 Al 0.69 Ti1 .46 (PO4)3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, etc. are included. Acid Oxide-based solid electrolytes have advantages such as being stable in the atmosphere.

[0122] Halide-based solid electrolytes include LiAlCl4, Li3InBr6, LiF, LiCl , LiBr, LiI, etc. Also, composite materials obtained by filling pores of porous aluminum oxide or porous silica with these halide-based solid electrolytes can also be used as solid electrolytes.

[0123] Also, different solid electrolytes may be mixed and used.

[0124] Among them, Li 1+B Al B Ti 2-B (PO4)3( 0 < B < 1) (hereinafter referred to as LATP) contains aluminum and titanium, which are elements that the positive electrode active material used in the secondary battery 400 of one embodiment of the present invention may have. Therefore, a synergistic effect can be expected for improving the cycle characteristics, which is preferable. Also, an improvement in productivity due to reduction of processes can be expected. . In this specification and the like, the NASICON-type crystal structure refers to a compound represented by M2(XO4)3 (M: transition metal, X: S, P, As, Mo, W, etc.), and has a structure in which MO6 octahedra and XO4 tetrahedra share vertices and are three-dimensionally arranged.

[0125] 〔Shape of the exterior body and the secondary battery〕 For the exterior body of the secondary battery 400 of one embodiment of the present invention, various materials and shapes can be used, but it preferably has a function of pressing the positive electrode, the solid electrolyte layer, and the negative electrode.

[0126] ​​​​​​ For example, FIGS. 5(A) to 5(C) show an example of a cell for evaluating materials for an all-solid-state battery.

[0127] FIG. 5(A) is a cross-sectional view of the evaluation cell. The evaluation cell is made up of a lower member 761 and an upper member 7 62 and a fixing screw and a wing nut 764 that fix them. By rotating the electrode plate 753, the evaluation material is fixed in place. An insulator 766 is provided between the lower member 761 and the upper member 762. An O-ring 76 is provided between the upper member 762 and the holding screw 763 for sealing. 5 is provided.

[0128] The material to be evaluated is placed on an electrode plate 751, surrounded by an insulating tube 752, and an electric It is pressed by the electrode plate 753. The figure is shown in Figure 5(B).

[0129] As an example of the evaluation material, a laminate of a positive electrode 750a, a solid electrolyte layer 750b, and a negative electrode 750c is shown. The cross-sectional view is shown in FIG. 5(C). Note that the same points in FIGS. 5(A) to 5(C) The same symbols are used wherever possible.

[0130] The electrode plate 751 and the lower member 761 electrically connected to the positive electrode 750a are It can be said that this corresponds to a terminal. The electrode plate 753 and the upper member 762 can be said to correspond to the negative terminal. The evaluation material is subjected to pressure via the electrode plate 751 and the electrode plate 753, and the electrical resistance is measured. can be measured.

[0131] In addition, a package with excellent airtightness may be used for the exterior body of the secondary battery according to one embodiment of the present invention. For example, a ceramic package or a resin package can be used. In addition, when sealing the exterior body, it is necessary to shut out the outside air and seal it in a sealed atmosphere, for example, in a glove box. It is preferable to carry out the treatment in a gas chamber.

[0132] FIG. 6A is a perspective view of a secondary battery according to one embodiment of the present invention, which has an exterior body and a shape different from those in FIG. The secondary battery in FIG. 6(A) has external electrodes 771 and 772, and is made up of multiple packages. The device is sealed in an exterior body having components.

[0133] An example of a cross section taken along the dashed line in FIG. 6(A) is shown in FIG. 6(B). The laminated body having the electrolyte layer 750b and the negative electrode 750c is formed by providing an electrode layer 773a on a flat plate. a package member 770a in the shape of a frame, a frame-shaped package member 770b, and a flat electrode layer 773 The package member 770c on which the wiring board 770b is provided is enclosed and sealed. The package members 770a, 770b, and 770c are made of an insulating material, such as a resin material or a ceramic material. can be used.

[0134] The external electrode 771 is electrically connected to the positive electrode 750a via the electrode layer 773a, and is connected to the positive electrode terminal The external electrode 772 is electrically connected to the negative electrode 750c via the electrode layer 773b. It is electrically connected to the negative terminal.

[0135] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0136] (Embodiment 3) In this embodiment, an example of the shape of the secondary battery having the positive electrode described in the previous embodiment will be described. The materials used in the secondary battery described in this embodiment are the same as those described in the previous embodiment. You can pour drinks.

[0137] <Coin-type secondary battery> First, an example of a coin-type secondary battery will be described. Figure 7(A) shows a coin-type (single-layer flat type) 7(A) and 7(B) are external views of the secondary battery, and FIG. 7(B) is a cross-sectional view thereof.

[0138] The coin-type secondary battery 300 has a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal. 302 is insulated and sealed by a gasket 303 made of polypropylene or the like. The positive electrode 304 is composed of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector 305. The negative electrode 307 is formed by a negative electrode current collector 308 and a The negative electrode active material layer 309 is formed by bonding the negative electrode active material layer 309 to the negative electrode active material layer 309 .

[0139] The positive electrode 304 and the negative electrode 307 used in the coin-type secondary battery 300 are each an active material. The barrier layer need only be formed on one side.

[0140] The positive electrode can 301 and the negative electrode can 302 are made of nickel and aluminum, which are corrosion-resistant to the electrolyte. , titanium, or alloys thereof or alloys of these with other metals (e.g. stainless steel) In addition, nickel or aluminum can be used to prevent corrosion by the electrolyte. The positive electrode can 301 is preferably coated with a positive electrode 304, and the negative electrode can 302 is preferably coated with a negative electrode 304. 7 and electrically connect to each other.

[0141] The negative electrode 307, the positive electrode 304, and the separator 310 are impregnated with an electrolyte, and the resultant structure shown in FIG. As shown in FIG. 1, the positive electrode can 301 is placed downward, and the positive electrode 304, separator 310, negative electrode 307, and negative electrode 308 are connected to the positive electrode can 301. The positive electrode can 301 and the negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are connected with a gasket 303 interposed therebetween. Then, the laminate is pressed to form a coin-type secondary battery 300.

[0142] By using the positive electrode described in the previous embodiment as the positive electrode 304, it is possible to obtain a battery with low cost and excellent rate characteristics. The secondary battery 300 may be a coin type.

[0143] Here, the flow of current during charging of a secondary battery will be explained using FIG. 7(C). When a secondary battery is considered as a closed circuit, the movement of lithium ions and the flow of current are in the same direction. In secondary batteries that use lithium, the anode (positive electrode) and cathode (cathode) is switched, and the oxidation reaction and reduction reaction are switched, so the reaction potential The electrode with a higher reaction potential is called the positive electrode, and the electrode with a lower reaction potential is called the negative electrode. Whether charging, discharging, or applying a reverse pulse current, Even when an electric current flows through it, the positive electrode is called the "positive electrode" or "+ electrode (plus electrode)" and the negative electrode is called the "positive electrode" or "+ electrode (plus electrode)". This is called the "negative electrode" or "-electrode (minus electrode)." When using the terms anode (positive electrode) and cathode (negative electrode), the following occurs during charging and discharging: This can be confusing as the anode and cathode are opposites. The term "cathode" will not be used in this specification. When using the terms cathode and positive electrode, specify whether they are charging or discharging. It will also be noted whether it corresponds to the negative pole (negative pole) or the positive pole (positive pole).

[0144] A charger is connected to the two terminals shown in FIG. 7(C) to charge the secondary battery 300. As the battery 300 is charged, the potential difference between the electrodes increases.

[0145] <Cylindrical secondary battery> Next, an example of a cylindrical secondary battery will be described with reference to FIG. An external view is shown in Fig. 8(A). Fig. 8(B) is a schematic cross-sectional view of a cylindrical secondary battery 600. As shown in FIG. 8(B), the cylindrical secondary battery 600 has a positive electrode cap on the top surface. The battery has a cover (battery lid) 601 and a battery can (external can) 602 on the side and bottom. The positive electrode cap 601 and the battery can (external can) 602 are connected by a gasket (insulating packing) 6 It is insulated by 10.

[0146] Inside a hollow cylindrical battery can 602, a strip-shaped positive electrode 604 and a negative electrode 606 are placed between a separator 6 The battery element is wound around the sensor. The battery can 602 is closed at one end and open at the other. The battery can 602 is made of a material that is resistant to corrosion by the electrolyte, such as nickel, aluminum, or titanium. These metals, or their alloys or alloys of these with other metals (e.g., stainless steel, etc.) are used. In addition, to prevent corrosion by the electrolyte, nickel, aluminum, etc. It is preferable to coat the battery can 602. Inside the battery can 602, the positive electrode, the negative electrode, and The battery element with the separator wound around it is sandwiched between a pair of opposing insulating plates 608 and 609. The inside of the battery can 602 in which the battery element is provided is filled with a non-aqueous electrolyte (not shown). The non-aqueous electrolyte can be the same as that used in coin-type secondary batteries. .

[0147] The positive and negative electrodes used in cylindrical storage batteries are wound, so active materials are formed on both sides of the current collector. A positive electrode terminal (positive electrode current collecting lead) 603 is connected to the positive electrode 604, and a negative electrode A negative electrode terminal (negative electrode current collecting lead) 607 is connected to the positive electrode terminal 603. The positive terminal 60 and the positive terminal 607 can be made of a metal material such as aluminum. 3 is resistance-welded to the safety valve mechanism 612, and the negative terminal 607 is resistance-welded to the bottom of the battery can 602. The safety valve mechanism 612 is a PTC (Positive Temperature Coupling) element. It is electrically connected to the positive electrode cap 601 via a stable (efficient) 611. When the internal pressure of the battery exceeds a predetermined threshold, the valve mechanism 612 closes the positive electrode cap 601 and The PTC element 611 cuts off the electrical connection with the positive electrode 604. It is a thermal resistance element whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current and prevents abnormalities. The PTC element is made of barium titanate (BaTiO3) based semiconductor. Conductive ceramics or the like can be used.

[0148] 8(C), a plurality of secondary batteries 600 are mounted on the conductive plate 613 and the conductive plate 614. A module 615 may be formed by sandwiching the secondary batteries 600 between them. They may be connected in series, or may be connected in parallel and then in series. By configuring a module 615 having a plurality of secondary batteries 600, It is possible to extract a large amount of power.

[0149] 8(D) is a top view of the module 615. The conductive plate 613 is dotted for clarity. As shown in FIG. 8(D), the module 615 is a module that electrically connects a plurality of secondary batteries 600. The conductive plate may be provided on the conductive wire 616. Furthermore, a temperature control device 617 may be provided between the plurality of secondary batteries 600. When the secondary battery 600 is overheated, the temperature control device 617 cools the secondary battery 600. If the module is too cold, it can be heated by the temperature control device 617. The performance of the module 615 is less affected by the outside temperature. It is preferable that the insulating material has non-flammable properties.

[0150] By using the positive electrode described in the previous embodiment as the positive electrode 604, it is possible to obtain a battery with low cost and excellent rate characteristics. The secondary battery 600 can be a cylindrical type.

[0151] <Example of secondary battery structure> Another structural example of the secondary battery will be described with reference to FIGS.

[0152] 9(A) and 9(B) are diagrams showing the external appearance of a battery pack. The secondary battery 913 is connected to the circuit board 900. The secondary battery 913 is connected to an antenna 914. A label 910 is attached to the secondary battery 913. Furthermore, as shown in FIG. 9(B), the secondary battery 913 has a terminal 951 and a terminal 9 52 and 53. The circuit board 900 is fixed with a seal 915.

[0153] The circuit board 900 has a terminal 911 and a circuit 912. The terminal 911 is connected to a terminal 951. , a terminal 952, an antenna 914, and a circuit 912. Each of the plurality of terminals 911 may be used as a control signal input terminal, a power supply terminal, etc. .

[0154] The circuit 912 may be provided on the back surface of the circuit board 900. The antenna 914 The antenna is not limited to a coil shape, but may be, for example, a wire shape or a plate shape. Antennas such as surface antennas, traveling wave antennas, EH antennas, magnetic field antennas, and dielectric antennas Alternatively, the antenna 914 may be a flat conductor. can function as one of the conductors for electric field coupling. The antenna 914 may function as one of the two conductors. Electric power can be exchanged not only using electromagnetic fields and magnetic fields, but also using electric fields.

[0155] The battery pack has a layer 916 between the antenna 914 and the secondary battery 913. The layer 916 has a function of blocking an electromagnetic field generated by the secondary battery 913, for example. For example, a magnetic material can be used as the material.

[0156] The structure of the battery pack is not limited to that shown in FIG.

[0157] For example, as shown in Figs. 10(A1) and 10(A2), In the secondary battery 913 shown in FIG. FIG. 10(A1) is an external view showing one of the pair of surfaces, and FIG. 10(A2) is an external view showing the one of the pair of surfaces. 9(A) and 9(B) are external views showing the other of the pair of surfaces. For the same parts, the description of the secondary battery shown in FIGS. 9(A) and 9(B) can be used as appropriate. .

[0158] As shown in FIG. 10(A1), a layer 916 is sandwiched between one of the two surfaces of a secondary battery 913. 10(A2), a retainer 914 is provided, and the other of the pair of surfaces of the secondary battery 913 is An antenna 918 is provided on the second layer 913 with a layer 917 sandwiched therebetween. The layer 917 has a function of blocking the electromagnetic field generated by the magnetic field. You can be there.

[0159] By adopting the above structure, the size of both the antenna 914 and the antenna 918 can be increased. The antenna 918 can perform data communication with an external device, for example. The antenna 918 has a shape that can be applied to the antenna 914, for example. A communication method between the secondary battery and other devices via the antenna 918 can be applied. For example, NFC (near field communication) can be used between secondary batteries and other devices. A response method that can be applied can be applied.

[0160] Alternatively, as shown in FIG. 10(B1), the secondary battery 913 shown in FIGS. 9(A) and 9(B) A display device 920 may be provided. The display device 920 is electrically connected to the terminal 911. It is not necessary to provide the label 910 in the area where the display device 920 is provided. The same parts as those of the secondary battery shown in FIGS. 9(A) and 9(B) are shown in FIGS. 9(A) and 9(B). The description of the secondary battery shown in 2. above can be used as appropriate.

[0161] The display device 920 displays, for example, an image indicating whether charging is in progress or not, an image indicating the amount of stored power, etc. The display device 920 may be, for example, an electronic paper, a liquid crystal display, an electrophotographic display, or the like. For example, an electroluminescence (EL) display device can be used. By using the par, the power consumption of the display device 920 can be reduced.

[0162] Alternatively, as shown in FIG. 10(B2), the secondary battery 913 shown in FIGS. 9(A) and 9(B) A sensor 921 may be provided. The sensor 921 is electrically connected to the terminal 911 via a terminal 922. The same parts as those of the secondary battery shown in Fig. 9(A) and Fig. 9(B) are connected to The description of the secondary battery shown in FIGS. 9(A) and 9(B) can be used as appropriate.

[0163] The sensor 921 may be, for example, a sensor for detecting displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, etc. , liquid, magnetic, temperature, chemical, sound, time, hardness, electric field, current, voltage, power, radiation, flow It is sufficient if it has the function of measuring volume, humidity, gradient, vibration, odor, or infrared. By providing the sensor 921, for example, data indicating the environment in which the secondary battery is placed can be obtained. It is also possible to detect a signal (such as temperature) and store it in memory within the circuit 912.

[0164] Furthermore, an example of the structure of the secondary battery 913 will be described with reference to FIGS.

[0165] The secondary battery 913 shown in FIG. 11(A) has a terminal 951 and a terminal 952 provided inside a housing 930. The winding body 950 is impregnated with an electrolyte inside the housing 930. The terminal 952 is in contact with the housing 930, and the terminal 951 is in contact with the housing by using an insulating material or the like. 11A, the housing 930 is not in contact with the housing 930. For convenience, the housing 930 is shown separated. Although the figure shows the winding body 950, in reality, the winding body 950 is covered by the housing 930, and the terminals 951 and 955 are 2 extends outside the housing 930. The housing 930 is made of a metal material (e.g., aluminum Rubber or resin materials can be used.

[0166] As shown in FIG. 11(B), the housing 930 shown in FIG. 11(A) is made of a plurality of materials. For example, the secondary battery 913 shown in FIG. 11B may be formed by a housing 930a and a housing 930b. The wound body 930 is located in the area surrounded by the housing 930a and the housing 930b. 50 are provided.

[0167] The housing 930a can be made of an insulating material such as organic resin. By using a material such as organic resin on the surface on which the secondary battery 913 is formed, If the shielding of the electric field by the housing 930a is small, the shielding of the electric field by the housing 930a can be suppressed. An antenna such as antenna 914 may be provided inside the housing 930b. Metallic materials can be used.

[0168] Furthermore, the structure of the wound body 950 is shown in Fig. 12. The wound body 950 is made up of a negative electrode 931 and a positive electrode 932. The winding body 950 has a pole 932 and a separator 933. The negative electrode 931 and the positive electrode 932 are stacked one on top of the other, and the laminated sheet is wound to form a wound body. The negative electrode 931, the positive electrode 932, and the separator 933 may be further laminated. You can stack several of them.

[0169] The negative electrode 931 is connected to the terminal 911 shown in FIG. 9 via one of the terminals 951 and 952. The positive electrode 932 is connected to the terminal 911 shown in FIG. 9 via the other of the terminals 951 and 952. Connected.

[0170] By using the positive electrode described in the previous embodiment for the positive electrode 932, it is possible to obtain a battery with low cost and excellent rate characteristics. The secondary battery 913 can be used.

[0171] <Laminated secondary battery> Next, an example of a laminated secondary battery will be described with reference to FIGS. If the laminated secondary battery is made flexible, it will have at least one flexible portion. The secondary battery can be mounted in electronic devices that also have some deformation, and the secondary battery can also be bent to match the deformation of the electronic device. Cut.

[0172] A laminated secondary battery 980 will be described with reference to FIG. The battery 980 has a wound body 993 shown in FIG. 12, a positive electrode 995, and a separator 996. Similar to the wound body 950, a negative electrode 994 and a positive electrode 995 are stacked with a separator 996 sandwiched therebetween. The laminated sheet is then wound up.

[0173] The number of layers of the negative electrode 994, the positive electrode 995, and the separator 996 is determined as required. The negative electrode 994 is connected to the lead electrode 997 and the lead The positive electrode 995 is connected to a negative electrode current collector (not shown) via one of the lead electrodes 998. The positive electrode 997 and the lead electrode 998 are connected to a positive electrode current collector (not shown).

[0174] As shown in FIG. 13(B), a film 981 that serves as an exterior body and a film 98 having a recess are 2 are bonded together by thermocompression or the like, and the above-mentioned wound body 993 is housed in the space formed. In this way, a secondary battery 980 can be fabricated as shown in FIG. 3 has lead electrodes 997 and 998, and is connected to a film 981 and a recessed portion. The inside of the film 982 is impregnated with an electrolyte.

[0175] The film 981 and the film 982 having the recesses are made of a metal material such as aluminum. The film 981 and the film 982 having the recesses can be made of a material such as a resin. If a resin material is used as the material, when external force is applied, the film 981 and the recessed portion The film 982 can be deformed to produce a flexible storage battery. can.

[0176] In addition, although Fig. 13(B) and Fig. 13(C) show examples using two films, A space is formed by folding one sheet of film, and the above-mentioned wound body 99 is inserted into the space. 3 may be accommodated.

[0177] By using the positive electrode described in the previous embodiment for the positive electrode 995, it is possible to obtain a battery with low cost and excellent rate characteristics. The secondary battery 980 can be used.

[0178] In addition, in FIG. 13, a secondary battery 9 having a wound body in a space formed by a film that serves as an exterior body is shown. 80 has been explained, but as shown in Figure 14, for example, The space defined by the positive electrode layer may be a secondary battery having a plurality of rectangular positive electrodes, separators, and negative electrodes. stomach.

[0179] The laminated secondary battery 500 shown in FIG. 14(A) includes a positive electrode current collector 501 and a positive electrode active material. a positive electrode 503 having a positive electrode active material layer 502, a negative electrode current collector 504 and a negative electrode active material layer 505 The battery includes a negative electrode 506, a separator 507, an electrolyte 508, and an exterior body 509. A separator 507 is provided between a positive electrode 503 and a negative electrode 506 provided in a body 509. The exterior body 509 is filled with an electrolyte 508. The electrolyte solution shown in the embodiment of (1) can be used.

[0180] In the laminated secondary battery 500 shown in FIG. 14(A), a positive electrode current collector 501 and a negative electrode current collector 502 are The electrode current collector 504 also serves as a terminal for electrical contact with the outside. A part of the current collector 501 and the negative electrode current collector 504 is exposed to the outside from the outer casing 509. In addition, the positive electrode current collector 501 and the negative electrode current collector 504 may be disposed in the outer casing 509. The lead electrode is not exposed to the outside, and the lead electrode is connected to the positive electrode current collector 501 or the negative electrode The lead electrode may be exposed to the outside by ultrasonic bonding to the current collector 504 .

[0181] In the laminated secondary battery 500, the exterior body 509 is made of, for example, polyethylene, poly A film made of propylene, polycarbonate, ionomer, polyamide, etc. is coated with an A thin metal film with excellent flexibility, such as aluminum, stainless steel, copper, or nickel, is applied, and the metal is further On the metallic thin film, an insulating synthetic resin such as polyamide resin or polyester resin is applied as the outer surface of the exterior body. A three-layer laminate film provided with an oil film can be used.

[0182] An example of the cross-sectional structure of a laminated secondary battery 500 is shown in FIG. For simplicity, in A), an example consisting of two current collectors is shown, but in reality, as shown in Figure 14(B), As shown in Figure 1, it is composed of multiple electrode layers.

[0183] In FIG. 14(B), as an example, the number of electrode layers is set to 16. However, the secondary battery 500 has flexibility. In FIG. 14(B), the negative electrode current collector 504 has eight layers. The positive electrode current collector 501 has eight layers, making a total of 16 layers. The cross section of the extraction part is shown, and eight layers of negative electrode current collector 504 are ultrasonically bonded. The number of electrode layers is not limited to 16, and may be more or less. In this case, a secondary battery having a larger capacity can be obtained. In this case, a secondary battery can be made thin and highly flexible.

[0184] An example of the external appearance of a laminated secondary battery 500 is shown in FIGS. 15 and 16. 5 and 16 show a positive electrode 503, a negative electrode 506, a separator 507, an outer casing 509, a positive electrode lead The positive electrode 510 and the negative electrode 511 are provided.

[0185] 17(A) shows an external view of the positive electrode 503 and the negative electrode 506. The positive electrode 503 is connected to the positive electrode current collector 50 1, and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501. 503 has a region where the positive electrode current collector 501 is partially exposed (hereinafter referred to as the tab region). 506 has a negative electrode current collector 504, and a negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504. In addition, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, a tab region. The area and shape of the tab regions of the positive electrode and negative electrode are not limited to the example shown in FIG. I can't.

[0186] <Method for manufacturing laminated secondary batteries> Here, an example of a method for manufacturing the laminated secondary battery shown in FIG. 15 will be described with reference to FIG. This will be explained using (B) and (C).

[0187] First, the negative electrode 506, the separator 507, and the positive electrode 503 are stacked. The figure shows five pairs of negative electrodes 506, separators 507, and positive electrodes 503. Next, the bonding of the tab regions of the positive electrode 503 and the bonding of the tabs of the positive electrode on the outermost surface are shown. The positive lead electrode 510 is bonded to the region. For example, ultrasonic welding or the like can be used for bonding. Similarly, the bonding of the tab regions of the negative electrodes 506 to each other and the bonding of the negative electrode leads to the tab region of the negative electrode on the outermost surface are also preferable. Then, the bonded electrode 511 is formed.

[0188] Next, the negative electrode 506 , the separator 507 and the positive electrode 503 are placed on the exterior body 509 .

[0189] Next, as shown in FIG. 17(C), the exterior body 509 is folded at the portion indicated by the broken line. After that, the outer periphery of the exterior body 509 is bonded. For example, thermocompression bonding may be used for bonding. , and a part (or one side) of the outer casing 509 so that the electrolyte 508 can be poured therein later. An area that is not bonded (hereinafter referred to as an inlet) is provided.

[0190] Next, electrolyte 508 (not shown) is introduced into exterior body 509 through an inlet provided in exterior body 509. The electrolyte 508 is introduced into the inside of the electrode 509 under a reduced pressure atmosphere or an inert atmosphere. Finally, the inlet is bonded. The secondary battery 500 can be manufactured.

[0191] By using the positive electrode described in the previous embodiment as the positive electrode 503, it is possible to obtain a battery having low cost and excellent rate characteristics. The secondary battery 500 can be made of a material other than aluminum.

[0192] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0193] (Fourth embodiment) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on an electronic device will be described. do.

[0194] First, examples of mounting the secondary battery described in the above embodiment on an electronic device are shown in FIGS. As an example of an electronic device to which the secondary battery described in the above embodiment is applied, a For example, television equipment (also called television or television receiver), computer Monitors, digital cameras, digital video cameras, digital photo frames, mobile phones, etc. Telephones (also called mobile phones or mobile phone devices), portable game consoles, personal digital assistants, portable batteries , audio playback devices, large game machines such as pachinko machines, etc.

[0195] FIG. 18A shows an example of a mobile phone. The mobile phone 7400 has a housing 7401. In addition to the display unit 7402 incorporated in the The mobile phone 7400 is equipped with a speaker 7405, a microphone 7406, etc. The secondary battery 7407 is a secondary battery of one embodiment of the present invention. This makes it possible to provide inexpensive, high-performance mobile phones.

[0196] FIG. 18B shows an example of a wristwatch-type portable information terminal. The portable information terminal 7200 is , a housing 7201, a display unit 7202, a band 7203, a buckle 7204, and an operation button 72 05, input / output terminal 7206, etc.

[0197] The portable information terminal 7200 is capable of carrying out mobile phone calls, e-mails, viewing and creating documents, playing music, and internet access. - It can run various applications such as internet communication and computer games. do.

[0198] The display surface of the display unit 7202 is curved, and the display is performed along the curved display surface. The display portion 7202 is provided with a touch sensor, and can be touched with a finger or a stylus. For example, the icon 72 displayed on the display unit 7202 can be operated by touching it. You can launch the application by touching 07.

[0199] The operation button 7205 is used to set the time, turn the power on and off, and turn wireless communication on and off. It has various functions such as operation, silent mode activation and deactivation, power saving mode activation and deactivation, etc. For example, an operating system installed in the portable information terminal 7200 can The function of the operation button 7205 can also be freely set using the stem.

[0200] In addition, the mobile information terminal 7200 is capable of performing standardized short-range wireless communication. For example, by communicating with a wireless headset, hands-free operation is possible. You can also make calls.

[0201] The portable information terminal 7200 also has an input / output terminal 7206, and can be connected to other information terminals via a connector. It is also possible to charge the battery via the input / output terminal 7206. The charging operation can be performed by wireless power supply without going through the input / output terminal 7206. That's fine.

[0202] The display portion 7202 of the portable information terminal 7200 includes the secondary battery of one embodiment of the present invention. By using the secondary battery of one embodiment of the present invention, an inexpensive and high-performance portable information terminal can be provided. For example, the secondary battery 7104 shown in FIG. 18D is curved inside the housing 7201. Alternatively, it can be incorporated in the band 7203 in a bendable state.

[0203] The mobile information terminal 7200 preferably has a sensor. For example, a fingerprint sensor may be used as the sensor. Human body sensors such as pulse sensors and body temperature sensors, as well as touch sensors, pressure sensors, and acceleration sensors It is preferable that a sensor, etc. be installed.

[0204] FIG. 18C shows an example of a bangle-type display device. The portable display device 7100 includes: The device includes a housing 7101, a display unit 7102, operation buttons 7103, and a secondary battery 7104. 18(D) shows the state of the bent secondary battery 7104. The secondary battery 7104 is bent. When the device is worn on the user's arm with the device attached, the housing may deform and cause damage to part of the secondary battery 7104 or The total curvature changes. The degree of curvature at any point on the curve is expressed as the radius of the corresponding circle. The value expressed is called the radius of curvature, and the reciprocal of the radius of curvature is called the curvature. Specifically, the radius of curvature is The area is within the range of 40 mm to 150 mm, and the area is part of the main surface of the casing or the secondary battery 7104. The radius of curvature of the main surface of the secondary battery 7104 is 40 mm or more and 150 mm or less. If the thickness is within the range of 1 mm or less, high reliability can be maintained. By using the secondary battery of one embodiment, an inexpensive and high-performance portable display device can be provided.

[0205] FIG. 18(E) shows an example of a wristband-type display device. The display device 7300 includes a display unit 7 304 and includes the secondary battery of one embodiment of the present invention. The display unit 7304 may be provided with a touch sensor, and may function as a portable information terminal. It is also possible.

[0206] The display surface of the display unit 7304 is curved, and images can be displayed along the curved display surface. The display device 7300 can also communicate with the display device 7300 by short-distance wireless communication according to a communication standard. The situation can be changed.

[0207] The display device 7300 also has an input / output terminal, and can directly exchange data with other information terminals via a connector. It is also possible to charge the device via the input / output terminals. The charging operation may be performed by wireless power supply without using the input / output terminals.

[0208] When the secondary battery of one embodiment of the present invention is used as the secondary battery included in the display device 7300, This makes it possible to provide a low-cost, high-performance display device.

[0209] FIG. 18(F) shows an example of a mobile battery. It has a secondary battery and multiple terminals 7351. It can charge other electronic devices via the terminals 7351. The secondary battery of one embodiment of the present invention is included in the mobile battery 7350. By using it as a battery, it can be used as a cheap and high-performance mobile battery 7350. .

[0210] In addition, an example in which the secondary battery with good cycle characteristics shown in the above embodiment is mounted on an electronic device is shown in FIG. 18(G), and will be explained with reference to FIGS. 19 and 20.

[0211] By using the secondary battery of one embodiment of the present invention as a secondary battery in an electronic device, a lightweight and long-life product can be achieved. For example, electronic devices such as electric toothbrushes, electric shavers, and electric beauty devices can be provided. The secondary batteries for these products are designed to be easy for users to hold, Therefore, there is a demand for a stick-shaped secondary battery that is small, lightweight, and has a large capacity.

[0212] FIG. 18(G) is a perspective view of a device also called a tobacco-containing smoking device (electronic cigarette). In 18(G), the electronic cigarette 7500 is an atomizer 7501 containing a heating element and an atomizer A secondary battery 7504 that supplies power to the MYZA, and a cart containing a liquid supply bottle, sensors, etc. To enhance safety, the secondary battery 7504 is protected from overcharging and overcharging. A protection circuit for preventing discharge may be electrically connected to the secondary battery 7504. The secondary battery 7504 has an external terminal so that it can be connected to a charging device. The 504 is the tip when held, so the total length is short and the weight is light. The secondary battery according to one embodiment of the present invention is inexpensive and has good rate characteristics. This allows us to provide the 7500 e-cigarette with high heating performance.

[0213] Next, Fig. 19(A) and Fig. 19(B) show an example of a foldable tablet terminal. The tablet terminal 9600 shown in FIG. 19(A) and FIG. 19(B) includes a housing 9630 a, a housing 9630b, a movable part 9640 connecting the housings 9630a and 9630b, and a display A display unit 9631 having a display unit 9631a and a display unit 9631b, switches 9625 to The display unit 9631 has a switch 9627, a fastener 9629, and an operation switch 9628. By using a flexible panel, it is possible to create a tablet terminal with a larger display area. FIG. 19(A) shows a state in which the tablet terminal 9600 is opened, and FIG. B) shows the tablet terminal 9600 in a closed state.

[0214] The tablet terminal 9600 also includes a battery storage device inside the housing 9630a and the housing 9630b. The power storage unit 9635 is connected to the housing 9630a through the movable portion 9640. It is located across 9630b.

[0215] The entire or a part of the display portion 9631 can be used as a touch panel. By touching images, text, input forms, etc. containing icons displayed in the area, data For example, a keyboard is provided on the entire surface of the display portion 9631a of the housing 9630a. By displaying the button, information such as text and images can be displayed on the display unit 9631b on the housing 9630b. may be displayed and used.

[0216] In addition, a keyboard is displayed on the display unit 9631b on the housing 9630b side, and The display portion 9631a on the side may be used to display information such as text and images. The 9631 is set to display a keyboard display switch button on the touch panel, and the By touching the button with your finger or a stylus, the keyboard will be displayed on the display 9631. You may do so.

[0217] In addition, the touch panel area of ​​the display unit 9631a on the housing 9630a side and the touch panel area of ​​the display unit 9631b on the housing 9630b side Simultaneous touch inputs can also be made to the touch panel area of ​​the display portion 9631b.

[0218] In addition, switches 9625 to 9627 are used to operate the tablet terminal 9600. It is not only an interface for switching between various functions, but also an interface for switching between various functions. For example, at least one of the switches 9625 to 9627 may be One acts as a power on / off switch for the tablet device 9600. Also, for example, at least one of the switches 9625 to 9627 may be The ability to switch between horizontal and vertical display, or between black and white and color display In addition, for example, at least one of the switches 9625 to 9627 may have a function to At least one of the display portions 9631 may have a function of adjusting the brightness of the display portion 9631. The brightness of 1 is the external brightness detected by the light sensor built into the tablet terminal 9600 during use. It can be optimized according to the amount of light. Note that the tablet device has a light sensor. In addition, it also incorporates other detection devices such as gyro, acceleration sensor, etc. to detect tilt. It is also acceptable to do so.

[0219] In FIG. 19A, the display portion 9631a on the housing 9630a side and the display portion 9631b on the housing 9630b side are 9631a and 9631b have almost the same display area. The display area of ​​each of the 631b is not particularly limited, and one size may be different from the other. The display quality may be different, for example, one may have a higher resolution than the other. The display panel may also be capable of performing the above.

[0220] FIG. 19(B) shows the tablet terminal 9600 in a folded state. The terminal 9600 includes a housing 9630, a solar cell 9633, and a DC-DC converter 9636. The power storage unit 9635 includes a charge / discharge control circuit 9634 including a power storage device according to one embodiment of the present invention. A storage battery is used.

[0221] As mentioned above, the tablet terminal 9600 can be folded in half, so when not in use, The housing 9630a and the housing 9630b can be folded so that they overlap each other. By folding, the display portion 9631 can be protected, and therefore the durability of the tablet terminal 9600 can be improved. Furthermore, the power storage unit 9635 using the secondary battery of one embodiment of the present invention can be stabilized. It has good rate characteristics at low cost, allowing us to provide a low-cost, high-performance tablet terminal, the 9600. Cut.

[0222] In addition, the tablet terminal 9600 shown in FIG. 19(A) and FIG. 19(B) , functions to display various information (still images, videos, text images, etc.), calendar, date or The function to display the time, etc. on the display, and the function to touch input or edit the information displayed on the display Touch input function, function to control processing by various software (programs), etc. can have:

[0223] The solar cell 9633 attached to the surface of the tablet terminal 9600 generates power. The solar cell 963 can be supplied to a panel, a display unit, a video signal processing unit, etc. 3 can be provided on one or both sides of the housing 9630, and the power storage unit 9635 can be efficiently charged. The power storage unit 9635 can be configured to use a lithium ion battery. This has the advantage of enabling miniaturization.

[0224] The configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 19(B) are shown in FIG. A block diagram is shown in FIG. 19(C) and will be explained. In FIG. 19(C), a solar cell 9633, a power storage unit 963 5, DC-DC converter 9636, converter 9637, switches SW1 to SW3, table The display unit 9631 is shown, and the storage battery 9635, the DC-DC converter 9636, 19B. This corresponds to 34.

[0225] First, an example of operation when power is generated by the solar cell 9633 using external light will be described. The power generated by the solar cell is converted into a voltage for charging the storage battery 9635. The voltage is increased or decreased by a inverter 9636. When power is used from the 9633, switch SW1 is turned on and the converter 9637 The voltage is increased or decreased to the voltage required for the display unit 9631. When not displaying the display, turn SW1 off and SW2 on to charge the power storage unit 9635. The configuration may be such that electricity is supplied.

[0226] The solar cell 9633 is shown as an example of a power generating means, but is not particularly limited thereto. Power storage using other power generation methods such as piezoelectric elements and thermoelectric conversion elements For example, the power may be transmitted and received wirelessly (contactlessly). It is also possible to combine it with a contactless power transmission module that charges the battery, or other charging means. That's fine.

[0227] Another example of electronic equipment is shown in FIG. 20. In FIG. 20, a display device 8000 is a display device according to one embodiment of the present invention. 8 is an example of an electronic device using a secondary battery 8004 according to an embodiment. 8000 corresponds to a display device for receiving TV broadcasts, and includes a housing 8001, a display unit 8002, and a speaker unit. The secondary battery 8004 according to one embodiment of the present invention includes a housing 8003 and a secondary battery 8004. The display device 8000 is provided inside a body 8001. The display device 8000 receives power from a commercial power source. Alternatively, the power stored in the secondary battery 8004 can be used. Even when power cannot be supplied from a commercial power source due to a power outage or the like, the present invention The display device 8000 can be used by using the secondary battery 8004 as an uninterruptible power supply. do.

[0228] The display unit 8002 includes a liquid crystal display device, an emitting device having a light emitting element such as an organic EL element in each pixel, and Device, electrophoretic display device, DMD (Digital Micromirror Device) ce), PDP (Plasma Display Panel), FED (Field A semiconductor display device such as a reflective LED (emission display) can be used.

[0229] In addition to TV broadcast reception, display devices are also used for personal computers and advertising displays. , including all display devices for displaying information.

[0230] In FIG. 20, a stationary lighting device 8100 includes a secondary battery 81 according to one embodiment of the present invention. 8101, a housing 8102, a light source 8103, and a light source 8104. 20, the secondary battery 8103 is mounted in the housing 81. 8101 and a light source 8102 are installed inside a ceiling 8104. However, the secondary battery 8103 may be provided inside the housing 8101. The device 8100 can receive power from a commercial power source or can store power in a secondary battery 8103. Therefore, if the power supply from the commercial power source is interrupted due to a power outage, etc., Even when the power is not available, the secondary battery 8103 according to one embodiment of the present invention can be used as an uninterruptible power supply. This allows the lighting device 8100 to be used.

[0231] 20 shows an example of a fixed lighting device 8100 provided on a ceiling 8104. However, the secondary battery according to one embodiment of the present invention is not limited to the ceiling 8104, but may be installed on other parts such as the side wall 8105 and the floor 8106. 106, it can be used for a fixed lighting device provided in a window 8107, etc., or it can be used for a tabletop lighting device. It can also be used in lighting devices of this type.

[0232] The light source 8102 may be an artificial light source that artificially obtains light using electricity. Specifically, incandescent lamps, fluorescent lamps and other discharge lamps, and light-emitting devices such as LEDs and organic EL elements The element is an example of the artificial light source.

[0233] In FIG. 20, an air conditioner having an indoor unit 8200 and an outdoor unit 8204 is 8 is an example of an electronic device using a secondary battery 8203 according to one embodiment of the present invention. The device 8200 includes a housing 8201, an air outlet 8202, a secondary battery 8203, and the like. 8 illustrates an example in which the secondary battery 8203 is provided in the indoor unit 8200. The battery 8203 may be provided in the outdoor unit 8204. Both the power supply 8201 and the power supply 8204 may be provided with a secondary battery 8203. The power supply can be supplied from a commercial power source, or the power stored in the secondary battery 8203 can be used. In particular, both the indoor unit 8200 and the outdoor unit 8204 may be equipped with secondary batteries 82 If 03 is installed, when power cannot be supplied from the commercial power source due to a power outage, etc. In addition, by using the secondary battery 8203 of one embodiment of the present invention as an uninterruptible power supply, The conditioner can be used.

[0234] In Figure 20, a separate type air conditioner consisting of an indoor unit and an outdoor unit is shown. As an example, it is an all-in-one air conditioner that has the functions of both the indoor unit and the outdoor unit in a single housing. The secondary battery according to one embodiment of the present invention can also be used in the conditioner.

[0235] In FIG. 20, an electric refrigerator-freezer 8300 includes a secondary battery 8304 according to one embodiment of the present invention. Specifically, an electric refrigerator-freezer 8300 includes a housing 8301, a refrigerator It has a storage compartment door 8302, a freezer compartment door 8303, a secondary battery 8304, etc. A secondary battery 8304 is provided inside the housing 8301. The electric refrigerator-freezer 8300 is It can receive power from a commercial power source, or use the power stored in the secondary battery 8304. Therefore, when power cannot be supplied from the commercial power source due to a power outage, etc. However, by using the secondary battery 8304 of one embodiment of the present invention as an uninterruptible power supply, It will be possible to use the 8300-capacity refrigerator.

[0236] Among the above-mentioned electronic devices, high-frequency heating devices such as microwave ovens and electric rice cookers are Equipment requires high power for a short period of time, so it supplements the power that cannot be supplied by commercial power. By using a secondary battery according to one embodiment of the present invention as an auxiliary power source for This prevents the commercial power breaker from tripping during use.

[0237] In addition, during times when electronic devices are not in use, especially when the total amount of power that can be supplied by the commercial power supplier is low, During the time period when the ratio of the amount of electricity actually used (called the electricity usage rate) is low, By storing power in the battery, it is possible to prevent power usage rates from increasing outside of the above time periods. For example, in the case of the electric refrigerator-freezer 8300, when the temperature is low and the refrigerator compartment door 830 2. During the night when the freezer door 8303 is not opened or closed, the secondary battery 8304 stores power. Then, as the temperature rises, the refrigerator door 8302 and the freezer door 8303 are opened and closed. By using the secondary battery 8304 as an auxiliary power source during the daytime, the daytime power usage rate can be kept low.

[0238] According to one embodiment of the present invention, the cycle characteristics of the secondary battery are improved, and the reliability is improved. Furthermore, according to one aspect of the present invention, a high-capacity secondary battery can be obtained. This improves the characteristics of the secondary battery, thereby making it possible to reduce the size and weight of the secondary battery itself. Therefore, the secondary battery according to one embodiment of the present invention can be used in the electronic devices described in this embodiment. By incorporating such a device, electronic devices can be made cheaper and have higher performance.

[0239] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0240] (Embodiment 5) In this embodiment, examples of electronic devices using the secondary battery described in the previous embodiment are shown. 21 to 22.

[0241] FIG. 21(A) shows an example of a wearable device. It uses a secondary battery as a power source. In addition, when the user uses it at home or outdoors, To improve splash, water or dust resistance, the connectors are exposed. There is a demand for wearable devices that can be charged wirelessly as well as by wire.

[0242] For example, a secondary lens according to one aspect of the present invention may be applied to a glasses-type device 4000 as shown in FIG. 21(A). The eyeglass-type device 4000 includes a frame 4000a and a display. The secondary battery is mounted on the temple of the curved frame 4000a. This allows for a lightweight, well-balanced eyeglass-type device that can be used continuously for a long time. By including the secondary battery according to one embodiment of the present invention, A high-performance eyeglass device 4000 can be realized.

[0243] In addition, the headset device 4001 may be equipped with a secondary battery according to one embodiment of the present invention. The headset type device 4001 includes at least a microphone unit 4001a and a frame. The flexible pipe 4001b and the earphone part 4001c are included. A secondary battery can be provided in the earphone unit 4001b or the earphone unit 4001c. By using a secondary battery, a low-cost, high-performance headset device 4001 can be realized. It can be realized.

[0244] In addition, a device 4002 that can be directly attached to the body is equipped with a secondary battery according to one embodiment of the present invention. The device 4002 can be mounted with a secondary battery 400 in a thin housing 4002a. By providing the secondary battery according to one embodiment of the present invention, it is possible to provide a low-cost, high-performance A device 4002 capable of performing the above-described operations can be realized.

[0245] In addition, a device 4003 that can be attached to clothing is equipped with a secondary battery according to one embodiment of the present invention. The device 4003 has a thin housing 4003a and a secondary battery 4003b. By including the secondary battery according to one embodiment of the present invention, it is possible to provide a low-cost, high-performance A device 4003 can be realized.

[0246] In addition, the belt-type device 4006 can be equipped with a secondary battery according to one embodiment of the present invention. The belt-type device 4006 includes a belt part 4006a and a wireless power receiving part 4006b. 06b, and a secondary battery can be mounted inside the belt portion 4006a. By providing a secondary battery, which is one aspect of the present invention, a low-cost and high-performance belt-type device 4006 can be realized. It can be realized.

[0247] In addition, the secondary battery of one embodiment of the present invention can be mounted on the wristwatch device 4005. The wristwatch type device 4005 has a display part 4005a and a belt part 4005b. A secondary battery can be provided in the display part 4005a or the belt part 4005b. By incorporating a secondary battery, which is one aspect, a low-cost, high-performance wristwatch-type device 4005 is realized. It is possible.

[0248] The display unit 4005a displays not only the time but also various information such as incoming emails and phone calls. It is possible.

[0249] The wristwatch type device 4005 is a wearable device that can be worn directly on the wrist. Therefore, sensors for measuring the user's pulse, blood pressure, etc. may be installed. It is also possible to accumulate health-related data and manage health.

[0250] FIG. 21(B) shows a perspective view of the wristwatch type device 4005 removed from the wrist.

[0251] A side view is shown in Fig. 21(C). Fig. 21(C) shows a device with a built-in secondary battery 913. The secondary battery 913 is the secondary battery described in the third embodiment. The battery 913 is provided in a position overlapping the display unit 4005a, and is small and lightweight. .

[0252] FIG. 22(A) shows an example of a cleaning robot. The cleaning robot 6300 is a housing 63 01 A display unit 6302 arranged on the top surface, multiple cameras 6303 arranged on the side, and a brush 6304, an operation button 6305, various sensors, etc. Although not shown, The cleaning robot 6300 is equipped with tires, a suction nozzle, etc. It moves on its own, detects dust 6310, and sucks it up through the suction port on the bottom. can.

[0253] For example, the cleaning robot 6300 analyzes the image captured by the camera 6303 and detects the walls, furniture, etc. It can also determine whether there are obstacles such as steps or wiring by image analysis. If an object that may become entangled in the brush 6304 is detected, the rotation of the brush 6304 is stopped. The cleaning robot 6300 includes a secondary battery 630 according to one embodiment of the present invention. 6, and a semiconductor device or an electronic component. By using this in the Cleaning Robot 6300, it will become an inexpensive and high-performance electronic device. can be done.

[0254] Figure 22(B) shows an example of a robot. The robot 6400 shown in Figure 22(B) is , secondary battery 6409, illuminance sensor 6401, microphone 6402, upper camera 640 3, a speaker 6404, a display unit 6405, a lower camera 6406, and an obstacle sensor 640 7, equipped with a moving mechanism 6408, a computing device, etc.

[0255] The microphone 6402 has a function of detecting the user's voice and environmental sounds. The speaker 6404 has a function of emitting sound. The device can communicate with the user using the microphone 6402 and the speaker 6404. It is possible.

[0256] The display unit 6405 has a function of displaying various information. The display unit 6405 can display desired information. The display unit 6405 may be a detachable information terminal. By placing it in a fixed position on the Robot 6400, charging and data transfer can be performed. It is possible.

[0257] The upper camera 6403 and the lower camera 6406 are used to capture images of the surroundings of the robot 6400. The obstacle sensor 6407 also detects the obstacles in the robot 640 by using the movement mechanism 6408. Robot 64 can sense whether there are any obstacles in its path as it moves forward. 00 uses an upper camera 6403, a lower camera 6406, and an obstacle sensor 6407 It is possible to recognize the surrounding environment and move safely.

[0258] The robot 6400 includes a secondary battery 6409 according to one embodiment of the present invention and a semiconductor device. The secondary battery according to one embodiment of the present invention can be used in a robot 6400. This allows the robot 6400 to be an inexpensive, high-performance, and highly reliable electronic device.

[0259] FIG. 22(C) shows an example of an aircraft. The aircraft 6500 shown in FIG. 22(C) is a plane It has a lopeller 6501, a camera 6502, and a secondary battery 6503, and flies autonomously. It has the function of

[0260] For example, image data captured by the camera 6502 is stored in the electronic component 6504. Part 6504 can analyze image data and detect the presence or absence of obstacles when moving. In addition, the electronic component 6504 can detect the change in the storage capacity of the secondary battery 6503. The remaining amount of the battery can be estimated. The secondary battery 6503 according to one embodiment of the present invention has good rate characteristics. It has high power output. Therefore, by using it in the flying object 6500, it is possible to achieve high acceleration performance etc. It can be set to 0.

[0261] This embodiment mode can be implemented in appropriate combination with other embodiment modes.

[0262] (Sixth embodiment) In this embodiment, an example in which a secondary battery according to one embodiment of the present invention is mounted on a vehicle will be described.

[0263] When a secondary battery is installed in a vehicle, it becomes a hybrid vehicle (HV), an electric vehicle (EV), or a plastic vehicle (PVE). This will enable the realization of next-generation clean energy vehicles such as powertrain hybrid vehicles (PEVs).

[0264] 23A illustrates an example of a vehicle using a secondary battery according to one embodiment of the present invention. The automobile 8400 shown in FIG. 1 is an electric automobile that uses an electric motor as a power source for driving. Alternatively, an electric motor and an engine can be selected as the power source for driving. By using one aspect of the present invention, it is possible to extend the driving range. Furthermore, the automobile 8400 has a secondary battery. 8(C) and 8(D) are mounted on the floor of the vehicle. In addition, a battery pack made up of multiple secondary batteries as shown in Figure 11 can be installed in a vehicle. The secondary battery only drives the electric motor 8406. It supplies power to light-emitting devices such as headlights 8401 and room lights (not shown). It is possible.

[0265] In addition, the secondary battery is used to power the speedometer, tachometer, and other displays of the automobile 8400. The secondary battery can supply power to the navigation device of the automobile 8400. The present invention can provide power to semiconductor devices such as mobile terminals.

[0266] The automobile 8500 shown in FIG. 23(B) has a secondary battery that is plugged in. It can be charged by receiving power from an external charging facility using a contactless power supply system or other methods. FIG. 23(B) shows a diagram of a charging device 8021 installed on a ground and a charging station 8022 installed on a vehicle 8500. The primary battery 8024 and the secondary battery 8025 are charged via a cable 8022. When charging, please refer to CHAdeMO (registered trademark) for charging methods and connector specifications. The charging device 8021 may be installed in a commercial facility. It can be a charging station connected to the car or it can be a home power source. For example, plug-in technology By this, the secondary battery 8024 and the battery 8025 mounted on the automobile 8500 are supplied with power from an external source. The secondary battery 8025 can be charged. This can be done by converting AC power into DC power via

[0267] Although not shown, a power receiving device is mounted on the vehicle and power is supplied contactlessly from a power transmitting device on the ground. In this case, a power transmission device is installed on the road or exterior wall. By incorporating this technology, charging can be carried out not only when the vehicle is stopped but also while the vehicle is moving. This method may be used to transmit and receive power between vehicles. A solar cell may be provided to charge the secondary battery when the vehicle is stopped or running. The power can be supplied by an electromagnetic induction method or a magnetic resonance method.

[0268] 23C shows an example of a two-wheeled vehicle using the secondary battery of one embodiment of the present invention. The scooter 8600 shown in (C) has a secondary battery 8602, side mirrors 8601, and a turn signal. The secondary battery 8602 can supply electricity to the direction indicator light 8603. can.

[0269] In addition, the scooter 8600 shown in FIG. 23(C) has a secondary battery 860 in the storage under the seat 8604. 2 can be stored. The secondary battery 8602 can be stored even if the under-seat storage 8604 is small. , it can be stored in the under-seat storage 8604. The secondary battery 8602 is removable, and when charging, the secondary battery 8602 is carried indoors, charged, and stored before driving. That's all. That's all.

[0270] According to one aspect of the present invention, it is possible to improve the productivity of a secondary battery with good rate characteristics and high output. Therefore, by using the secondary battery according to one aspect of the present invention in a vehicle, it is possible to obtain a vehicle with improved acceleration performance and the like. In addition, the secondary battery mounted on the vehicle can also be used as a power supply other than the vehicle. In this case, for example, it is possible to avoid using the commercial power supply during the peak of power demand. Avoiding using the commercial power supply during the peak of power demand can contribute to energy saving and reduction of carbon dioxide emissions. In addition, if the cycle characteristics are good, the secondary battery can be used for a long time, so the usage amount of rare metals including cobalt can be reduced. That's all for this paragraph. That's all for this paragraph. That's all for this paragraph. That's all for this paragraph. That's all for this paragraph. That's all for this paragraph. That's all for this paragraph.

[0271] This embodiment can be implemented in appropriate combination with other embodiments.

Example

[0272] In this example, the reduction method of GO was studied. For this purpose, a GO film for basic evaluation was prepared, reduced by several methods, and various analyses were performed. That's all for this paragraph.

[0273] <Fabrication of GO film> As GO, the one prepared using potassium permanganate and sulfuric acid in the oxidation process by the Modified Hummers method was used. For 200 ml of a dispersion obtained by dispersing 3 wt% of GO in water, 600 mL of water was added, and the mixture was stirred with a stirrer at 600 rpm. That's all for this paragraph. That's all for this paragraph. This was carried out for 12 hours to prepare dispersion A.

[0274] Next, the GO dispersion was used as a raw material and graphene compound sheets were obtained by spray drying. Here, the GO film was formed on the wall of the chamber of the spray-drying device. The details are explained below.

[0275] The spray drying device used was a BUCHI Mini Spray Dryer B-290. The inlet temperature was set to 160°C. The area around the nozzle was heated to a temperature of 100°C or higher. Dispersion A was supplied to the nozzle of the spray dryer at a rate of about 65 mL / min. Dispersion liquid A was sprayed into the chamber from a nozzle together with nitrogen gas at a flow rate of 12 L / min. and was supplied.

[0276] Dispersion A was supplied to the chamber as a spray, and part of it was collected in a collection container as GO powder. The powder was collected, and a portion of it was deposited as a GO film on the inner wall of the cylindrical chamber.

[0277] Next, the GO film was peeled off from the inner wall of the chamber. The GO film has multiple GO films stacked on top of each other. The average thickness of this GO film before reduction was 8.6 μm. did.

[0278] <Chemical reduction> Next, the GO film was reduced chemically using ascorbic acid as a reducing agent. A 0.078 mol / L L-ascorbic acid solution was prepared and the GO film was immersed in it. The reaction was then carried out at 60°C for 1 hour. This chemically reduced product was designated as Sample 2. .

[0279] <Thermal reduction> Next, the GO film was reduced by a thermal method using a glass tube oven. The heating temperatures were 100°C, 120°C, 150°C, 170°C, 200°C, or 250°C. The heating time was 10 hours. However, for the heating temperature of 170°C, the heating time was 1 hour. The heating time also included the time during which the temperature was rising. The heating rate was about 11°C / min. All samples were heated under reduced pressure (approximately 1 kPa). Sample 9 was selected.

[0280] In addition, after chemical reduction by treating with ascorbic acid solution at 60°C for 1 hour, The sample that was thermally reduced for 0 hours was designated as Sample 10.

[0281] The conditions for producing Samples 1 to 10 are shown in Table 1.

[0282] [Table 1]

[0283] <Raman spectroscopy> Samples 1, 7, and 10 prepared as described above were subjected to Raman spectroscopy. The laser wavelength was 532 nm, the wavelength dispersion D = 0.6, and the pinhole diameter was 1 00μm, and the central wave number of the spectrometer is 2000cm -1 , Diffraction grating is 150-500nm, exposure The time was 10 seconds, and the number of measurements was 5. The sample was fixed to a glass plate with double-sided tape and the measurement was performed. .

[0284] The Raman spectrum is shown in Figure 25. 2 The peak due to hybrid orbitals is 15 90cm -1Occurs in the vicinity. D band (sp 3 Peak derived from hybrid orbital) occurs at 1350 c m -1 Occurs in the vicinity.

[0285] As shown in Fig. 25, in Sample 7 where only thermal reduction was performed, the intensity of the G band peak became slightly stronger compared to Sample 1 without reduction, and the D band peak broadened. Therefore, it was suggested that both sp hybrid orbitals and defects increased. Therefore sp 2 It was suggested that both hybrid orbitals and defects increased.

[0286] On the other hand, in Sample 10 where both chemical reduction and thermal reduction were performed, the intensity of the G band peak became stronger compared to Sample 1. Therefore, it was suggested that sp 2 orbitals increased.

[0287] The intensity ratio G / D of the G band and the D band was 0.936 for Sample 1, 1.06 for Sample 5, and 1.63 for Sample 10.

[0288] <FT-IR and XRD (Reduction Temperature)> Next, Fourier transform infrared spectroscopy (FT-IR) and XR D were used to analyze and compare Sample 1 of the comparative example with Samples 3, 4, 5 Sample 6, and Sample 9 with different thermal reduction temperatures. FT-IR was measured by the total reflection measurement method (ATR method).

[0289] The results of FT-IR are shown in Fig. 26. In FT-IR, the absorption derived from the hydroxy group (O-H) occurs at a wavenumber of 3000 cm -1 or higher and 3600 cm -1 or lower. The absorption derived from the carbonyl group (C=O ) occurs at a wavenumber of around 1720 cm -1 In the vicinity. The absorption derived from the carbon-carbon double bond (C=C) occurs at a wavenumber of 1640 cm -1It is derived from the bond between carbon and oxygen (CO) Absorption is at a wavenumber of 1050 cm -1 These are shown in gray in Figure 26.

[0290] As shown in Figure 26, as the reduction temperature increases, the wavenumber of 3000 cm -1 More than 3600cm -1 Absorption due to OH occurring below 1050 cm -1 CO generated nearby The absorption of the hydroxyl group is reduced, suggesting that the hydroxyl group has been removed. 1640cm -1 The increase in absorption due to the C=C bond in the vicinity indicates that the carbon-carbon double bond (C=C ) is suggested to be increasing.

[0291] The results of XRD are shown in Figure 27. XRD was performed as powder XRD using CuKα1 radiation, and measurements were taken in air. The electrodes were attached to a silicon non-reflective plate with grease to maintain flatness. The broad peak at about 2θ=19° is the background. There is a peak at around 2θ=25° due to distance.

[0292] As shown in Figure 27, Sample 1, which was not thermally reduced, and Sample 2, which was reduced at 100°C, 3 had a peak at 2θ = 10° to 12°. Samples 4, 5, 6 and 9 showed a peak around 2θ = 24°. This is close to the peak due to the interlayer distance of graphite.

[0293] From these results, it is clear that in the case of thermal reduction, reduction progresses as the temperature increases. It was also found that the reduction proceeded significantly when the thermal reduction was carried out at 125°C or higher. Ta.

[0294] <Sheet resistance> Next, for Sample 1, Sample 2, Sample 6, and Sample 10, the surface resistivity was measured. The measurement was performed by the four-probe method. The results are shown in Fig. 28.

[0295] As shown in Fig. 28, compared with Sample 1 that has not been subjected to reduction treatment, the conductivity of Sample 2, Sample 6, and Sample 10 that have undergone some reduction treatment has improved. Compared with Sample 2 that has undergone chemical reduction, Sample 6 that has undergone thermal reduction had a lower surface resistivity. Therefore, it is suggested that thermal reduction contributes more to reducing the resistance than chemical reduction using ascorbic acid.

[0296] <XRD (Reduction method)> Next, for Sample 1 and Sample 2, Sample 6, and Sample 10 with different reduction methods, XRD was used for analysis and comparison in the same manner as in Fig. 27. The results are shown in Fig. 29. The broad peak at about 2θ = 19° indicated by an asterisk in Fig. 29 is the background. Also, the peak near 2θ = 25° indicated by a dotted line in Fig. 29 is the peak derived from the interlayer distance of graphite.

[0297] From the peak positions of the (002) plane of the XRD spectra shown in Fig. 29, the distances between carbon sheets of each sample were calculated using Bragg's equation, and the results are shown in Table 2. The surface resistivities measured above are also shown.

[0298]

Table 2

[0299] From Fig. 29 and Table 2, it can be seen that the sample with the lowest resistivity and the smallest interlayer distance is the one subjected to both chemical reduction and thermal reduction. Sample 10 was the one that underwent both the original processes. Also, Sample 6, which was thermally reduced, had a lower resistivity than Sample 2, which underwent only chemical reduction, and the interlayer distance had shrunk. From these results, it became clear that as the distance between the carbon sheets shrank, the reduction of resistance progressed. Next, Sample 1, Sample 2 with a different reduction method, Sample 6, and Sample 10 were analyzed and compared using FT-IR in the same manner as in Fig. 26. The results are shown in Fig. 30. The absorption of each functional group is shown in gray in the figure in the same manner as in Fig. 26. As shown in Fig. 30, in Sample 10, which underwent both chemical reduction and thermal reduction, an absorption appeared near a wavenumber of 1640 cm⁻¹, indicating that C=C was formed. Also, in Sample 6 and Sample 10, which underwent thermal reduction, the absorption near a wavenumber of 1050 cm⁻¹ and above 3000 cm⁻¹ and below 3600 cm⁻¹ decreased, indicating that the hydroxy group (-OH) had detached from the carbon. Also, in Sample 2 and Sample 10, which underwent chemical reduction, the absorption near a wavenumber of 1720 cm⁻¹ decreased, indicating that the carbonyl group (C=O) and the carboxy group (-COOH) had been reduced.

[0300] <FT-IR (Reduction Method)> Next, regarding Sample 1, Sample 2 with a different reduction method, Sample 6, and Sample 10, they were analyzed and compared using FT-IR in the same manner as in Fig. 26. The results are shown in Fig. 30. The absorption of each functional group is shown in gray in the figure in the same manner as in Fig. 26. As shown in Fig. 30, in Sample 10, which underwent both chemical reduction and thermal reduction, an absorption appeared near a wavenumber of 1640 cm⁻¹, indicating that C=C was formed. Also, in Sample 6 and Sample 10, which underwent thermal reduction, the absorption near a wavenumber of 1050 cm⁻¹ and above 3000 cm⁻¹ and below 3600 cm⁻¹ decreased, indicating that the hydroxy group (-OH) had detached from the carbon. Also, in Sample 2 and Sample 10, which underwent chemical reduction, the absorption near a wavenumber of 1720 cm⁻¹ decreased, indicating that the carbonyl group (C=O) and the carboxy group (-COOH) had been reduced.

[0301] As shown in Fig. 30, in Sample 10, which underwent both chemical reduction and thermal reduction, an absorption appeared near a wavenumber of 1640 cm⁻¹, indicating that C=C was formed. Also, in Sample 6 and Sample 10, which underwent thermal reduction, the absorption near a wavenumber of 1050 cm⁻¹ and above 3000 cm⁻¹ and below 3600 cm⁻¹ decreased, indicating that the hydroxy group (-OH) had detached from the carbon. Also, in Sample 2 and Sample 10, which underwent chemical reduction, the absorption near a wavenumber of 1720 cm⁻¹ decreased, indicating that the carbonyl group (C=O) and the carboxy group (-COOH) had been reduced. 0 cm⁻¹ -1 An absorption appeared near a wavenumber of 1640 cm⁻¹, indicating that C=C was formed. Also, in Sample 6 and Sample 10, which underwent thermal reduction, the absorption near a wavenumber of 1050 cm⁻¹ and above 3000 cm⁻¹ and below 3600 cm⁻¹ decreased, indicating that the hydroxy group (-OH) had detached from the carbon. Also, in Sample 2 and Sample 10, which underwent chemical reduction, the absorption near a wavenumber of 1720 cm⁻¹ decreased, indicating that the carbonyl group (C=O) and the carboxy group (-COOH) had been reduced. Samples 6 and 10 that underwent thermal reduction had a decrease in absorption near a wavenumber of 1050 cm⁻¹ and above 3000 cm⁻¹ and below 3600 cm⁻¹, indicating that the hydroxy group (-OH) had detached from the carbon. Also, in Samples 2 and 10 that underwent chemical reduction, the absorption near a wavenumber of 1720 cm⁻¹ decreased, indicating that the carbonyl group (C=O) and the carboxy group (-COOH) had been reduced. -1 near a wavenumber of 1050 cm⁻¹ and above 3000 cm⁻¹ and below 3600 cm⁻¹ 00 cm⁻¹ -1 above 3000 cm⁻¹ and below 3600 cm⁻¹ -1 decreased, indicating that the hydroxy group (-OH) had detached from the carbon. Also, in Samples 2 and 10 that underwent chemical reduction, the absorption near a wavenumber of 1720 cm⁻¹ decreased, indicating that the carbonyl group (C=O) and the carboxy group (-COOH) had been reduced. In Samples 2 and 10 that underwent chemical reduction, the absorption near a wavenumber of 1720 cm⁻¹ decreased, indicating that the carbonyl group (C=O) and the carboxy group (-COOH) had been reduced. -1 near a wavenumber of 1720 cm⁻¹ decreased, indicating that the carbonyl group (C=O

[0302] <xps> Next, samples 1, 2, 8, and 9 were prepared without being made into GO films. The same reduction treatment as for Model 10 was performed and analyzed using XPS. The results are shown in Table 3. .

[0303] [Table 3]

[0304] As shown in Table 3, the proportion of CO in Sample 2, which underwent chemical reduction, decreased. It was revealed that the epoxy group or carboxy group was reduced. This may be due to the hydroxyl group, but considering the FT-IR results, it is not clear whether Sample 2 was sufficiently reduced. It is thought that the carbon double bond (C=C) is not present in the sample 7, which was only thermally reduced. was also increasing.

[0305] From the above analysis, it was found that chemical reduction is a process in which the carbonyl groups in GO are protonated by a reducing agent. It was found that the reduction effect of carboxyl groups (C=O) and carboxyl groups (-COOH) was significant. In addition, thermal reduction is highly effective in reducing the hydroxyl groups (-OH) in GO through dehydration. As the reduction of GO progresses, the interlayer distance decreases. Electricity increases.

[0306] Thus, GO can be reduced more efficiently by performing both chemical and thermal reduction. On the other hand, chemical reduction reduces the material at a lower temperature than thermal reduction. Therefore, if the material used for the positive electrode has low heat resistance, chemical reduction is possible. is effective. [Example]

[0307] In this example, a secondary battery was fabricated using chemically or thermally reduced GO as a conductive material. , and its characteristics were evaluated.

[0308] <Preparation of secondary battery> For evaluation, a CR2032 type (diameter 20 mm, height 3.2 mm) coin-type secondary battery was used. was produced.

[0309] LFP was used as the positive electrode active material for the secondary battery. GO (Nishina Materials Co., Ltd., acid The modified Hummers method was used in the annealing process. The binder used was PVDF. Positive electrode active material: Conductive material: Binder = The mixture was mixed at a ratio of 94.2:0.8:5 (by weight) to prepare a slurry. The slurry was applied to a current collector and dried. An aluminum foil having a groove was used.

[0310] Next, the GO in the positive electrode active material layer was reduced by chemical or thermal reduction.

[0311] L-ascorbic acid was used as the reducing agent for chemical reduction. The solvent was water:NMP = 1:9 (volume ratio). ) to prepare a 0.078 mol / L L-ascorbic acid solution. The current collector coated with the positive electrode active material layer was immersed in the solution and reacted at 60°C for 1 hour. The reduction conditions were the same as those for Sample 2 in Example 1.

[0312] Sample 12 was also prepared by thermal reduction at a heating temperature of 170°C for 10 hours. This is the same reduction condition as Sample 6.

[0313] Also, immerse in 0.078 mol / L L-ascorbic acid solution and react at 60°C for 1 hour. After chemical reduction, the sample was thermally reduced at a heating temperature of 170°C for 10 hours. This was sample 13, which was the same reduction condition as sample 10.

[0314] After each reduction treatment, the electrodes were pressed at a linear pressure of 210 kN / m to form positive electrodes.

[0315] As a comparative example, AB was used as the conductive material, and the ratio of positive electrode active material:conductive material:binder was 94.2:0. Sample 14 was prepared by mixing AB and AB as the conductive material. Sample 15 was prepared by mixing material, conductive material, and binder in a ratio of 85:10:5 (by weight). In addition, graphene (manufactured by Graphene Supermarket, Grade A-12) is used as the conductive material. The positive electrode active material: conductive material: binder = 85:10:5 (wt%) was used as sample 1. This graphene has not undergone any oxidation process. The samples were prepared in the same manner as Samples 11 to 13 except for the mixing ratio of the material layers.

[0316] The counter electrode was made of lithium metal.

[0317] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). A mixture of C:DEC=3:7 (volume ratio) was used.

[0318] The separator was made of polypropylene with a thickness of 25 μm.

[0319] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0320] The preparation conditions for Samples 11 to 16 are shown in Table 4.

[0321] [Table 4]

[0322] <sem> The positive electrode of Sample 13 prepared above was observed with an electron microscope. The surface SEM image is shown in Figure 31. The cross-sectional SEM image is shown in Figure 32(A). The reduced GO, which is observed as white in Figure 32(A), A portion of the figure is shown in black in order to make it easier to see.

[0323] Figure 31 shows that reduced GO covers multiple particles of the positive electrode active material. 2(A) and 32(B), it can be seen that the reduced GO does not aggregate but is well distributed in the positive electrode active material layer. It can also be seen that the reduced GO is distributed in a mesh-like pattern, suggesting a net-like structure. It can be said that a net-like structure is formed by reduced GO. It can also be called a net.

[0324] <Battery characteristics> Next, charge-discharge tests were carried out on Samples 11 to 16. Charging was performed using CCCV (0. 2C, 4.3V, final current 0.02C), discharge is CC (0.2C, final voltage 2.0V) The measurement was carried out at 25° C. In this example, 1C was set to 170 mA / g.

[0325] The first discharge curves of Samples 11 to 13, which use reduced GO as the conductive material, are shown. The initial discharge capacity is shown in Figure 33(A). Sample 11 had a capacity of 55 mAh / g, and Sample 12 had a capacity of 15 6mAh / g, and sample 13 was 158mAh / g. Sample 13, which used GO after reduction, had good discharge characteristics with a broad plateau. It was revealed that the resistance of GO was reduced by combining the original techniques.

[0326] Next, Sample 13 was subjected to a cycle test at different discharge rates. Discharge the cycle at 0.2C, discharge 11 to 20 cycles at 0.5C, and discharge 21 to 30 cycles at 1 The other conditions were the same as those in the charge-discharge test described above. The same was true.

[0327] The discharge capacity of Sample 13 is shown in Figure 33(B). Sample 13, which uses GO, shows good battery characteristics even when the discharge rate increases. It became clear.

[0328] Next, the initial charge-discharge curves of Samples 13 to 16 are shown in Fig. 34(A) and Fig. 34(B). Fig. 34(A) shows the discharge capacity per weight of active material, and Fig. 34(B) shows the volume of the positive electrode active material layer. The discharge capacity per unit.

[0329] Sample 13, which used 0.8 wt% reduced GO as the conductive material, exhibited a higher thermal conductivity than Sample 15. Although the amount of conductive material is much less than that of the It was suggested that a sufficient conductive path could be formed in the positive electrode active material layer at 0.8 wt% of GO. The discharge capacity of Sample 13 was 158 mAh / g per active material weight and 158 mAh / g per positive electrode active material layer volume. 304mAh / cm 3 It was.

[0330] On the other hand, the discharge capacity of sample 14, which uses 0.8 wt% AB as a conductive material, is 1 mAh / g and 1mAh / cm 3 The battery barely functioned as a battery. AB was 0. It was suggested that a conductive path could not be formed at 8 wt %.

[0331] Sample 15, which uses 10% by weight of AB as the conductive material, exhibits relatively good discharge characteristics. This suggests that a conductive path was formed in the positive electrode active material layer. The discharge capacity is 139mAh / g per active material weight and 201mAh / g per positive electrode active material layer volume. cm 3 In particular, the discharge capacity per volume was less than two-thirds of that of Sample 14. When 10 wt% of AB is used as the active material, the volume of AB increases, so It was also revealed that the discharge capacity per volume of the positive electrode active material layer decreased.

[0332] Sample 16, which uses 10% by weight of graphene as a conductive material, also exhibits a similar level of conductivity to Sample 14. Although the discharge characteristics were good, they were not as good as those of Sample 13, which used reduced GO. Reduced GO is more dispersed than graphene in smaller amounts, and can efficiently form conductive paths. It was shown that:

[0333] Next, the rate characteristics of Sample 13 and Sample 15 were compared. The discharge rate was set to 0.2C, The measurements were taken at 0.5C, 1C, 2C and 5C. The other conditions were the same as the charge / discharge test described above. It was decided.

[0334] Figure 35(A) shows the discharge curve of sample 13, and Figure 35(B) shows the discharge curve of sample 15. The discharge capacity of sample 13 was 158mAh / g at 0.2C and 153mAh at 0.5C. / g, 149mAh / g at 1C, 143mAh / g at 2C, and 130mAh / g at 5C. On the other hand, the discharge capacity of sample 15 was 139 mAh / g at 0.2 C and 127 mAh / g at 0.5 C. mAh / g, 118mAh / g at 1C, 107mAh / g at 2C, 92mAh / g at 5C It was.

[0335] Thus, the 0.8 wt% reduced G was more effective than the 10 wt% AB in Sample 15. Sample 13, which used O, showed better rate characteristics. Since surface contact with the particles is possible, this property is thought to contribute to the low resistance of secondary batteries. It was.

[0336] As shown in the above examples, secondary batteries using reduced GO as a conductive material have a small amount of Conductive materials have good battery characteristics, such as high energy density and high rate characteristics. It became clear. [Example]

[0337] In this example, a secondary battery having reduced GO as a conductive material and a secondary battery having graphene were A secondary battery with AB and a secondary battery with AB were fabricated and their characteristics were compared.

[0338] <Preparation of secondary battery> For evaluation, a CR2032 type (diameter 20 mm, height 3.2 mm) coin-type secondary battery was used. was produced.

[0339] The positive electrode active material of secondary batteries is LFP or lithium nickel-cobalt-manganese oxide (NC LFP was composed of lithium carbonate, ammonium dihydrogen phosphate, and iron oxalate dihydrate. The NCM was synthesized by the solid phase method using a monohydrate of Ni:Co:Mn=5:2: The product used was a 3 (atomic ratio) product (manufactured by MTI). This is sometimes referred to as NCM523. Samples 17 to 19 are LFP, and samples 20 to 22 are NCM5. 23 was used.

[0340] GO or AB was used as the conductive material. GO will be reduced in a later process. Sample 17, Samples 20 and 22 were made of GO. Sample 18 was made of graphene (graphene Supermarket Co., Ltd., Grade A-12) was used. Sample 19 and Sample 2 1 used AB.

[0341] PVDF was used as the binder. The compounding ratio was set to 5 wt%.

[0342] The positive electrode active material, conductive material, and binder were mixed to prepare a slurry. NMP was used as the solvent. The slurry was applied to a current collector and dried. Aluminum foil was used.

[0343] Next, we will look at Samples 17, 20, and 22, which use GO as the conductive material. Chemical and thermal reduction were carried out.

[0344] L-ascorbic acid was used as the reducing agent for chemical reduction. The solvent was water:NMP = 1:9 (volume ratio). ) to prepare a 0.078 mol / L L-ascorbic acid solution. The current collector coated with the positive electrode active material layer was immersed in the solution and reacted at 60° C. for 1 hour.

[0345] Next, thermal reduction was carried out at a heating temperature of 170°C for 10 hours.

[0346] After the reduction treatment, the electrode was pressed at a linear pressure of 210 kN / m to form a positive electrode.

[0347] The counter electrode was made of lithium metal.

[0348] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contained ethylene carbonate (EC) and diethyl carbonate (DEC). EC:DEC=3:7 (volume ratio) mixed with 2 wt% vinylene carbonate (VC) was added.

[0349] The separator was made of polypropylene with a thickness of 25 μm.

[0350] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0351] Table 5 shows the preparation conditions for Samples 17 to 22.

[0352] [Table 5]

[0353] <Battery characteristics> A charge-discharge test was carried out on Samples 17 to 22.

[0354] FIG. 36A shows the charge rate characteristics of Samples 17 to 19 at 25° C. Charge is CC (0.2C, 0.5C, 1C, 2C or 5C, final voltage 4.3V), discharge is CC (0.2 C, final voltage 2.0 V). In this example, 1 C is 170 mA. The discharge rates at 25° C. of Samples 17 to 19 are shown in FIG. The characteristics are shown below. Charge is CCCV (0.2C, 4.3V, final current 0.02C), discharge is CC (0.2C, 1C, 2C, 5C or 10C, final voltage 2.0V).

[0355] The CC charge capacity of sample 17, which uses reduced GO as the conductive material, is 154 at 0.2 C. 0.24mAh / g, 148.77mAh / g at 0.5C, 143.99mAh / g at 1C , 138.33mAh / g at 2C and 127.92mAh / g at 5C. The CC charge capacity of sample 18, which uses graphene as the material, is 115.4 mA at 0.2 C. h / g, 101.0mAh / g at 0.5C, 89.35mAh / g at 1C, and 78 at 2C. The efficiencies were 30mAh / g at 5C and 60.88mAh / g at 5C. The CC charge capacity of sample 19 was 120.59 mAh / g at 0.2 C and 10.5 C at 0.5 C. 7.79mAh / g at 1C, 99.18mAh / g at 2C, 89.76mAh / g at 5C The result was 76.17mAh / g.

[0356] FIG. 37(A) shows the charge rate characteristics of Sample 17 and Sample 19 at 0° C. FIG. 37(B) shows the discharge rate characteristics of Sample 17 and Sample 19 at 0° C. The charge and discharge conditions were the same as those in FIGS. 36(A) and 36(B).

[0357] As shown in Table 5, Figures 36(A) and 36(B), Figures 37(A) and 37(B) Sample 17, which uses reduced GO as a conductive material, is significantly better than Sample 1, which uses graphene. Although the weight ratio of the conductive material is much lower than that of Sample 19 using 8 and AB, At 25°C and 0.5C to 5C, Sample 1 exhibited extremely good high rate characteristics. It showed more than twice the charging capacity of the 9.

[0358] In this way, in secondary batteries that use LFP as the positive electrode active material, reduced GO is used as the conductive material. It was revealed that the high-speed charging and high-power discharging characteristics were improved by using the reduced This is thought to be because the restored GO forms a good conductive path in the positive electrode active material layer. It was found that the high-power discharge characteristics were improved by using reduced GO rather than graphene. This is thought to be due to the extremely high dispersibility of reduced GO compared to graphene. can be.

[0359] FIG. 38(A) shows the charge rate characteristics of Sample 20 and Sample 21 at 25°C. Figure 38(B) shows the discharge rate characteristics of Sample 20 and Sample 21 at 25°C. The charge and discharge conditions were the same as those in Figure 36.

[0360] As shown in Figure 38(A), even when the positive electrode active material is NCM523, it is reduced as a conductive material. Sample 20, which uses GO, shows excellent conductivity, especially at high rates, despite the low weight ratio of the conductive material. It showed good characteristics during charging. It is clear that reduced GO has good conductivity in the positive electrode active material layer. This is thought to be because an electrical path is formed.

[0361] FIG. 39(A) shows the cycle characteristics of Sample 21 and Sample 22 at 25°C. FIG. 39(B) shows the cycle characteristics of Sample 21 and Sample 22 at 45° C. FIG. 39(C) shows the cycle characteristics of Sample 21 and Sample 22 at 60°C. Charge is CC (0.2C, end voltage 4.3V), discharge is CC (0.2C, end voltage 2.0V ) was decided.

[0362] As shown in Figures 39(A) to 39(C), when AB is used as the conductive material, especially at 60°C, Sample 21, which had a conductive material, showed a significant decrease in capacity as the cycles went by. Sample 22, which used GO reduced as a catalyst, showed excellent cycle performance. Sample 22 also exhibited better cycle characteristics than Sample 21 in terms of temperature.

[0363] FIG. 40(A) shows the charge rate characteristics of Sample 21 and Sample 22 at 0° C. Charging is CCCV (0.5C, 1C, 2C, 5C or 10C, 4.3V, final current 0.0 The discharge was CC (0.2C, final voltage 2.0V).

[0364] FIG. 40(B) shows the discharge rate characteristics of Sample 21 and Sample 22 at 0° C. Charge is CCCV (0.2C, 4.3V, final current 0.02C), discharge is CC (0.5C, The voltage was 1C, 2C, 5C or 10C, and the final voltage was 2.0V.

[0365] Figure 41(A) shows the charging curves of Sample 21 and Sample 22 at 1 C at 0°C. FIG. 41(B) shows the charging characteristics of Sample 21 and Sample 22 at 0°C and 0.2 C. Shows.

[0366] As shown in Figures 40(A) and 41(A), at 0°C, Sample 21 using AB exhibited no electrical conductivity. The charge was terminated immediately due to a voltage drop, resulting in an extremely low charge capacity. Sample 22 using the same material showed good charge capacity even at 2C.

[0367] As shown in Fig. 40(B) and Fig. 41(B), the discharge rate of Sample 22 showed better characteristics.

[0368] Thus, even at a low temperature of 0°C, the secondary battery using reduced GO exhibited excellent charging rate and It was shown that the battery had good discharge rate characteristics. [Example]

[0369] In this example, reduced GO was used as the conductive material and reduced polysaccharide was used as the binder. A secondary battery having a positive electrode was fabricated and its characteristics were evaluated.

[0370] <Preparation of positive electrode> Potato starch was used as the polysaccharide binder. As in step S12a, the binder and solvent were mixed.

[0371] 1 g of starch was dispersed in 9 g of water and mixed in a stainless steel container while heating to 100°C. The starch paste was 10 wt% prepared by Method 1. This was used for Samples 23 and 24. there was.

[0372] Also, weigh out 1g of starch and 9g of water and place them in a mixing container, cover it, and heat it in a hot water bath at 80℃ for 5 minutes. This was the 10 wt% starch paste prepared by Method 2. Used for pull 30.

[0373] Next, similarly to step S12b, 10 wt% starch paste and a conductive material were mixed. Powdered GO (Graphenea) or amine-modified GO (Graphenea) Samples 23, 24, 26, and 28 were coated with GO. Sample 25 used amine-modified GO. Sample 25 also used AB as a comparative example. These were prepared as Samples 29 and 30. The mixture was stirred at 2000 rpm for 3 minutes using a mixing machine (manufactured by THINKY).

[0374] Next, similar to step S12c, the positive electrode active material was mixed with the mixture of 10 wt% starch paste and GO. The positive electrode active material used was LFP without a carbon coating. The LFPs used were those synthesized by the solid-phase method (manufactured by ATR) or those synthesized by the solid-phase method. The raw materials are lithium oxalate, ammonium dihydrogen phosphate, and iron oxalate dihydrate, which are synthesized by solid-phase method. The mixture was mixed in a planetary centrifugal mixer at 2000 rpm for 3 minutes, repeated five times. Water was added as needed to adjust the viscosity, and this was made into a slurry (step S13).

[0375] Next, the slurry was applied to the current collector (step S14). The aluminum foil used was

[0376] After coating, the slurry was dried at 80°C (step S15). For coin-type secondary batteries (diameter 20 mm, height 3.2 mm), current collectors and slurry were poured. I pulled it out.

[0377] Next, a reduction treatment was carried out (step S16). The reduction treatment was carried out by either thermal reduction alone or chemical reduction. After the reaction, thermal reduction was carried out. A glass tube oven was used for heating the mixture under reduced pressure (1 The heating time included the time during which the temperature was increased. The heating rate was about 1°C / min. The heating temperature was 170°C, 200°C, 250°C, or 300°C.

[0378] Ascorbic acid was used as the reducing agent for chemical reduction, and ethanol was used as the solvent. An 8 mol / L L-ascorbic acid ethanol solution was prepared, and the current collector and slurry were added to this. The mixture was then allowed to react at 60°C for 1 hour.

[0379] Sample 27 was subjected to thermal reduction after chemical reduction. The heating time for thermal reduction was 170°C. Samples 23 to 26 and samples 28 to 30 were only thermally reduced. The heating temperature was 300°C for Samples 23 and 24, and 25°C for Sample 25. 0°C, sample 26 at 200°C, sample 28 and sample 29 at 250°C, sample 30 was set to 200°C.

[0380] The above-mentioned reduction-treated product was used as a positive electrode (step S18).

[0381] The preparation conditions for Samples 23 to 30 are shown in Table 6. The amount of starch mixed as a binder is expressed as the weight of starch contained in the starch paste.

[0382] [Table 6]

[0383] <Preparation of secondary battery> Using the positive electrodes of Samples 23 to 30, CR2032 type (diameter 20 mm) A coin-type secondary battery (height 3.2 mm) was fabricated.

[0384] The counter electrode was made of lithium metal.

[0385] The electrolyte used in the electrolytic solution is 1 mol / L lithium hexafluorophosphate (LiPF6). The electrolyte contains ethylene carbonate (EC) and diethyl carbonate (DEC). A mixture of C:DEC=3:7 (volume ratio) was used.

[0386] The separator was made of polypropylene with a thickness of 25 μm.

[0387] The positive electrode can and the negative electrode can were made of stainless steel (SUS).

[0388] <sem> The positive electrode of Sample 23 prepared above was observed under an electron microscope. The surface SEM image is shown in Figure 42 (A ) and Fig. 42(B). From Fig. 42(A), it can be seen that the reduced GO in the positive electrode active material layer is well In addition, Figure 42(B) shows that the reduced GO is dispersed in multiple cathode active materials. You can see how it covers the particles of matter.

[0389] <Battery characteristics and charge / discharge cycle characteristics> Next, charge-discharge tests were carried out on Samples 23 to 30. Charging was performed using CCCV (0. 5C, 4.3V, final current 0.05C), discharge is CC (0.5C, final voltage 2.5V) The measurement was carried out at 25° C. In this example, 1C was set to 170 mA / g.

[0390] The charge-discharge curves of Sample 23 from 1 to 50 cycles are shown in FIG. 43(A), and the charge-discharge cycle characteristics are shown in FIG. The discharge energy retention rate is shown in Figure 43(B). It was found that the positive electrode using GO and thermally reduced at 300°C was capable of sufficient charge and discharge. It became.

[0391] The charge-discharge cycle characteristics of Samples 23 and 24 are shown in Figure 44. Sample 23, which used O, was capable of charging and discharging. Sample 24 used in this study showed almost no discharge capacity. This is thought to be because the dispersibility in the starch paste was poor and sufficient conductive paths could not be formed even after reduction. Ta.

[0392] The charge-discharge cycle characteristics of Samples 25 to 27 are shown in Figure 45. Sample 25, which underwent thermal reduction at 200°C, showed better cycle performance than Sample 26, which underwent thermal reduction at 200°C. Sample 27, which was thermally reduced at 170°C after chemical reduction, also showed sufficient charge / discharge properties. On the other hand, thermal reduction at high temperatures such as 250°C or higher resulted in the formation of binders and positive electrode active materials. Depending on the material, the strength of the positive electrode active material layer may be reduced. Thermal reduction at temperatures below 200°C can also be effective depending on the binder and positive electrode active material. In some cases, the strength of the positive electrode active material layer can be increased by leaving some uncarbonized portions in the conductive material. There is.

[0393] The charge-discharge curves of Sample 28 for the first to eighth cycles are shown in FIG. 46(A), and the charge-discharge cycle characteristics are shown in FIG. The discharge energy retention rate is shown in Figure 46(B). The amount of support in Sample 28 was 4.57 mg. / cm 2 The supported amount refers to the weight of the positive electrode active material per area. was calculated as the weight of the positive electrode active material layer after reduction / the compounding ratio of the positive electrode active material.

[0394] The charge-discharge curves of Sample 29 for cycles 1 to 28 are shown in FIG. 47(A). The discharge energy retention rate is shown in Figure 47(B). The amount of support in Sample 29 was 1.64 m g / cm 2 It was.

[0395] The charge-discharge curves of sample 30 for the first to 31st cycles are shown in FIG. 48(A), and the charge-discharge cycle characteristics are shown in FIG. The discharge energy retention rate is shown in Figure 48(B). The amount of support in sample 30 was 1.65 m g / cm 2 It was.

[0396] All of Samples 28 to 30 were able to be fully charged and discharged. In contrast, the positive electrode using starch as a binder has a very thin positive electrode active material layer after the slurry is applied. It was difficult to fabricate a positive electrode with the same amount of support as in Sample 28. Therefore, by significantly reducing the amount of support in Samples 29 and 30, the positive electrode It became possible to fabricate and charge / discharge the battery.

[0397] On the other hand, sample 28, which uses GO as a conductive material, forms a sufficient conductive path even with a small amount, and the positive electrode The strength of the active material layer was also good.

[0398] The initial discharge capacities of Samples 28 and 29 are shown in Figure 49. The discharge capacity per volume is , and sample 28, which used GO as the conductive material, had a capacity of 198.0 mAh / cm 3 , AB Sample 29 is 158.6mAh / cm 3 As shown in Figure 49, sample 28 was The battery had a low plateau, a large discharge capacity, and good discharge characteristics.

[0399] In this way, a secondary battery using GO as a conductive material and starch as a binder is The secondary battery using AB was superior in strength of the positive electrode active material layer, discharge characteristics, etc. [Explanation of symbols]

[0400] 100 Cathode active material 200 Active material layer 201 Graphene and graphene compounds< / sem> < / sem> < / xps>

Claims

1. A secondary battery having a positive electrode, a negative electrode, a separator, and an electrolyte, the positive electrode includes a positive electrode active material, a conductive material, a binder, and a positive electrode current collector; the positive electrode active material is lithium iron phosphate, the conductive material is reduced graphene oxide; The reduced graphene oxide has carbon and oxygen, the reduced graphene oxide has a sheet-like shape and a two-dimensional structure formed of six-membered carbon rings; a secondary battery comprising a portion in which the reduced graphene oxide has a carbon concentration of more than 80 atomic % and an oxygen concentration of 2 atomic % or more and 15 atomic % or less.

2. In claim 1, The reduced graphene oxide has an intensity ratio G / D of a G band to a D band in a Raman spectrum of 1 or more.

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