Abstract: To provide graphene oxide that has high dispersibility and is easily reduced. To provide graphene with high electron conductivity. To provide a storage battery electrode including an active material layer with high electric conductivity and a manufacturing method thereof. To provide a storage battery with increased discharge capacity. A method for manufacturing a storage battery electrode that is to be provided includes a step of dispersing graphene oxide into a solution containing alcohol or acid, a step of heating the graphene oxide dispersed into the solution, and a step or reducing the graphene oxide.

Abstract: A composite oxide with high diffusion rate of lithium is provided. Alternatively, a lithium-containing complex phosphate with high diffusion rate of lithium is provided. Alternatively, a positive electrode active material with high diffusion rate of lithium is provided. Alternatively, a lithium ion battery with high output is provided. Alternatively, a lithium ion battery that can be manufactured at low cost is provided. A positive electrode active material is formed through a first step of mixing a lithium compound, a phosphorus compound, and water, a second step of adjusting pH by adding a first aqueous solution to a first mixed solution formed in the first step, a third step of mixing an iron compound with a second mixed solution formed in the second step, a fourth step of performing heat treatment under a pressure more than or equal to 0.1 MPa and less than or equal to 2 MPa at a highest temperature more than 100° C. and less than or equal to 119° C.

Abstract: A gel electrolyte and a separator are provided between the positive electrode current collector and the negative electrode current collector. The plurality of positive electrode current collectors and the plurality of negative electrode current collectors are stacked such that surfaces of negative electrodes with which active material layers are not coated or surfaces of positive electrodes with which active material layers are not coated are in contact with each other.

Abstract: A lithium-ion secondary battery having high capacity and excellent charge and discharge cycle performance is provided. A secondary battery having high capacity is provided. A secondary battery with excellent charge and discharge characteristics is provided. A secondary battery in which a reduction in capacity is suppressed even when a state being charged with a high voltage is held for a long time is provided. In the secondary battery, after constant current charging is performed in an environment at 60° C. with a current value of 0.5 C until a voltage reaches 4.5 V, a charging process of performing constant voltage charging until a current value reaches 0.2 C and a discharging process of performing constant current discharging with a current value of 0.

Abstract: A positive electrode active material having high capacity and excellent cycle performance is provided. The positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charge and discharge as compared with those of a known positive electrode active material.

Abstract: A method for manufacturing a highly purified positive electrode active material is provided. Alternatively, a method for manufacturing a positive electrode active material whose crystal structure is not easily broken even when charge and discharge are repeated is provided. The method for manufacturing a positive electrode active material containing lithium and a transition metal includes a first step of preparing a lithium compound, a phosphorus compound, and water; a second step of forming a first mixture by mixing the lithium compound, the phosphorus compound, and the water; a third step of forming a second mixture by adding a first aqueous solution to the first mixture to adjust a pH; a fourth step of forming a third mixture by mixing an iron(II) compound with the second mixture; a fifth step of forming a fourth mixture by heating the third mixture; and a sixth step of obtaining a positive electrode active material by filtering, washing, and drying the fourth mixture.

Abstract: A negative electrode with little deterioration is provided. A novel negative electrode is provided. A power storage device with little deterioration is provided. A novel power storage device is provided. The electrode contains silicon, graphite, and a graphene compound. A silicon particle with a particle diameter of less than or equal to 1 µm is attached to a graphite particle with a particle diameter 10 times or more that of the silicon particle. The graphene compound is in contact with the graphite particle so as to cover the silicon particle.

Abstract: A positive electrode active material having high capacity and excellent cycle performance is provided. The positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charge and discharge as compared with those of a known positive electrode active material.

Abstract: A positive electrode active material includes a plurality of groups of particles. The plurality of groups of particles has a particle diameter of more than or equal to 300 nm and less than or equal to 3 ?m. Each of the groups includes two or more particles. The two or more particles are each a lithium-containing complex phosphate including one or more of iron, nickel, manganese, and cobalt. The group of particles includes a first particle and a second particle each having a major diameter and a minor diameter in the upper surface when seen from a predetermined direction. The major diameters of the first and second particles are substantially parallel to each other. The major diameter of the first particle is two to six times larger than the minor diameter of the first particle and the minor diameter of the first particle is more than or equal to 20 nm and less than or equal to 130 nm.

Abstract: In the case where a film, which has lower strength than a metal can, is used as an exterior body of a secondary battery, a current collector provided in a region surrounded by the exterior body, an active material layer provided on a surface of the current collector, or the like might be damaged when force is externally applied to the secondary battery. A secondary battery which is resistant to external force in obtained. An opening is provided in a central portion of the secondary battery, and a terminal is formed in the opening. An outer edge of the secondary battery is fixed by thermocompression bonding. In addition, the central portion of the secondary battery is fixed by thermocompression bonding, so that the amount of bending is limited even when the outer edge portion of the secondary battery is bent.

Abstract: A positive electrode for a secondary battery having excellent cycle performance is provided. The positive electrode for a secondary battery includes a positive electrode current collector layer, a base film, a positive electrode active material layer, and a cap layer; the base film contains titanium nitride; the positive electrode active material layer contains lithium cobalt oxide; and the cap layer contains titanium oxide. The use of titanium nitride for the base film can inhibit oxidation of the positive electrode current collector and diffusion of metal atoms while ensuring an adequate conductivity. The use of titanium oxide for the cap layer can inhibit a side reaction between the positive electrode active material layer and an electrolyte and collapse of a crystal structure of the electrode active material, improving the cycle performance.

Abstract: According to one embodiment of the present invention, a secondary battery that can be used at a wide range of temperatures and is less likely to be influenced by an environmental temperature is provided. Furthermore, a secondary battery with high safety is provided. An electrolyte obtained by mixing an acyclic ester having high temperature characteristics with a fluorinated carbonic ester at 5 vol. % or higher, preferably 20 vol. % or higher, is used for the purpose of reducing interface resistance between an electrode and an electrolyte, whereby a secondary battery capable of operating at a wide range of temperatures, specifically, at temperatures higher than or equal to ?40° C. and lower than or equal to 150° C., preferably higher than or equal to ?40° C. and lower than or equal to 85° C. can be achieved.

Abstract: An object is to provide a nonaqueous solvent, a secondary battery, or a vehicle having a wide usable temperature range and high heat resistance. The nonaqueous solvent of the present invention contains an ionic liquid at greater than or equal to 50 vol % and less than or equal to 95 vol % and a fluorinated cyclic carbonate, and the ionic liquid contains an imidazolium cation. The nonaqueous solvent of the present invention has low viscosity at low temperatures and high heat resistance, thereby having a wide usable temperature range.

Abstract: To provide a positive electrode active material film that does not have a (003) orientation and has a layered rock-salt crystal structure even though an inexpensive substrate such as a glass substrate is used, and a positive electrode including the positive electrode active material film. The positive electrode includes a substrate, a positive electrode current collector film, and the positive electrode active material film. The positive electrode current collector film has a stacked structure of a titanium film and a titanium nitride film. The titanium film has a crystal structure belonging to a space group P63/mmc and a (101) orientation, the titanium nitride film has a crystal structure belonging to a space group Fm-3m and a (311) orientation, and the positive electrode active material film has a layered rock-salt crystal structure and a (116) orientation.

Abstract: Interface contact between a polymer electrolyte and an active material layer is improved. A secondary battery with improved discharge capacity is provided. The secondary battery includes a positive electrode, a negative electrode, and an electrolyte layer between the positive electrode and the negative electrode. The positive electrode includes a positive electrode active material, a first lithium-ion conductive polymer, a first lithium salt, and a conductive material over a positive electrode current collector. The electrolyte layer includes a second lithium-ion conductive polymer and a second lithium salt. The conductive material is preferably graphene. The negative electrode preferably includes a negative electrode active material, a third lithium-ion conductive polymer, a third lithium salt, and a second conductive material over a negative electrode current collector.

Abstract: A positive electrode active material includes a plurality of groups of particles. The plurality of groups of particles has a particle diameter of more than or equal to 300 nm and less than or equal to 3 ?m. Each of the groups includes two or more particles. The two or more particles are each a lithium-containing complex phosphate including one or more of iron, nickel, manganese, and cobalt. The group of particles includes a first particle and a second particle each having a major diameter and a minor diameter in the upper surface when seen from a predetermined direction. The major diameters of the first and second particles are substantially parallel to each other. The major diameter of the first particle is two to six times larger than the minor diameter of the first particle and the minor diameter of the first particle is more than or equal to 20 nm and less than or equal to 130 nm.

Abstract: In the case where a film, which has lower strength than a metal can, is used as an exterior body of a secondary battery, a current collector provided in a region surrounded by the exterior body, an active material layer provided on a surface of the current collector, or the like might be damaged when force is externally applied to the secondary battery. A secondary battery which is resistant to external force is obtained. An opening is provided in a central portion of the secondary battery; and a terminal is formed in the opening. An outer edge of the secondary battery is fixed by thermocompression bonding. In addition, the central portion of the secondary battery is fixed by thermocompression bonding, so that the amount of bending is limited even when the outer edge portion of the secondary battery is bent.

Abstract: A positive electrode active material having high capacity and excellent cycle performance is provided. The positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charge and discharge as compared with those of a known positive electrode active material.

Abstract: An active material layer that has a high filling rate and a higher density and is formed using a small amount of conductive additive is provided. A positive electrode active material layer includes a first carbon material and a second carbon material, which is more likely to aggregate than the first carbon material, and mixing is performed such that the weight of the second carbon material is more than or equal to 1.5 times and less than or equal to 20 times that of the first carbon material, thereby preventing the aggregation of the second carbon material and the aggregation of the first carbon material and reducing the proportion of the aggregated portions.

Abstract: A secondary battery with favorable cycle performance is provided. Alternatively, a secondary battery with higher capacity is provided. A positive electrode active material layer including a first graphene layer, a second graphene layer, and a positive electrode active material. The first graphene layer includes a first region covering the positive electrode active material. The second graphene layer includes a second region covering the positive electrode active material and a third region overlapping with the first region. The first region includes a plane positioned between the positive electrode active material and the third region and formed of arranged six-membered carbon rings. The positive electrode active material includes a fourth region with a layered rock-salt structure. A lithium layer with a layered rock-salt structure included in the fourth region is substantially perpendicular to the plane formed of six-membered carbon rings and included in the second region.