Abstract: As a positive electrode active material of a secondary battery, a lithium-manganese composite oxide containing lithium, manganese, and an element represented by M, and oxygen is used, and the lithium-manganese composite oxide is covered with reduced graphene oxide. An active material layer including the active material, graphene oxide, a conductive additive, and a binder is formed and soaked in alcohol, and then heat treatment is performed, whereby an electrode with reduced graphene oxide is fabricated.

Abstract: To provide a power storage device with a high capacity. To provide a power storage device with a high energy density. To provide a highly reliable power storage device. To provide a long-life power storage device. To provide an electrode with a high capacity. To provide an electrode with a high energy density. To provide a highly reliable electrode. To provide a long-life electrode. The power storage device includes a first electrode and a second electrode. The first electrode includes a first current collector and a first active material layer. The first active material layer includes a first active material and a first binder. The first active material is graphite. A separation strength F of the first electrode that is measured when the first active material layer is separated from the first current collector after the first electrode is immersed in a solution at a temperature higher than or equal to 20° C. and lower than or equal to 70° C.

Abstract: A graphene oxide used as a raw material of a conductive additive for forming an active material layer with high electron conductivity with a small amount of a conductive additive is provided. A positive electrode for a nonaqueous secondary battery using the graphene oxide as a conductive additive is provided. The graphene oxide is used as a raw material of a conductive additive in a positive electrode for a nonaqueous secondary battery and, in the graphene oxide, the weight ratio of oxygen to carbon is greater than or equal to 0.405.

Abstract: In manufacture of a storage battery electrode containing graphene as a conductive additive, the efficiency of reduction of graphene oxide under mild conditions is increased, and cycle characteristics and rate characteristics of a storage battery are improved. Provided is a manufacturing method of a storage battery electrode. In the manufacturing method, a first mixture containing an active material, graphene oxide, and a solvent is formed; a reducing agent is added to the first mixture and the graphene oxide is reduced to form a second mixture; a binder is mixed with the second mixture to form a third mixture; and the third mixture is applied to a current collector and the solvent is evaporated to form an active material layer.

Abstract: In manufacture of a storage battery electrode containing graphene as a conductive additive, the efficiency of reduction of graphene oxide is reduced with high efficiency under mild conditions, and cycle characteristics and rate characteristics of a storage battery are improved. Provided is a manufacturing method of a storage battery electrode. In the manufacturing method, a paste containing an active material, a binder, graphene oxide, and a solvent is formed; the paste is applied to a current collector and the solvent contained in the paste is evaporated to form an active material layer; the active material layer is immersed in a liquid containing alcohol; and the active material layer is taken out from the liquid and heated so that the graphene oxide is reduced.

Abstract: Provided is an electrode including a current collector and an active material layer. The active material layer includes an active material, a film including silicone, a conductive additive, and a binder. The active material is in the form of a particle. The film including silicone covers at least part of the active material.

Abstract: A graphene oxide used as a raw material of a conductive additive for forming an active material layer with high electron conductivity with a small amount of a conductive additive is provided. A positive electrode for a nonaqueous secondary battery using the graphene oxide as a conductive additive is provided. The graphene oxide is used as a raw material of a conductive additive in a positive electrode for a nonaqueous secondary battery and, in the graphene oxide, the atomic ratio of oxygen to carbon is greater than or equal to 0.405.

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: An electrode improved for achieving a storage battery having both a high electrode strength and favorable electrode conductivity is provided. The electrode includes graphene and a modified polymer in an active material layer or includes a layer substantially formed of carbon particles and an active material layer including a modified polymer over a current collector. The modified polymer has a poly(vinylidene fluoride) structure and partly has a polyene structure or an aromatic ring structure. The polyene structure or the aromatic ring structure is sandwiched between poly(vinylidene fluoride) structures.

Abstract: A lithium-ion secondary battery with high capacity is provided. Alternatively, a lithium-ion secondary battery with improved cycle characteristics is provided. To achieve this, an active material including a particle having a cleavage plane and a layer containing carbon covering at least part of the cleavage plane is provided. The particle having the cleavage plane contains lithium, manganese, nickel, and oxygen. The layer containing carbon preferably contains graphene. When a lithium-ion secondary battery is fabricated using an electrode including the particle having the cleavage plane at least part of which is covered with the layer containing carbon as an active material, the discharge capacity can be increased and the cycle characteristics can be improved.

Abstract: The cycle performance of a lithium-ion secondary battery or a lithium-ion capacitor can be obtained by minimizing the decomposition reaction of an electrolytic solution, etc. in the repeated charge and discharge cycles of the lithium-ion secondary battery or the lithium-ion capacitor. An electrode includes a current collector and an active material layer over the current collector. The active material layer includes active material particles, a conductive additive, a binder, and a film containing silicon oxide as its main component. The surface of one of the active material particles includes at least one of a region in contact with the surface of another active material particle, a region in contact with the conductive additive, and a region in contact with the binder. The surface of the active material particle except these regions is at least partly in contact with the film containing silicon oxide as its main component.

Abstract: Graphene that is formed from graphene oxide and has high conductivity and a method for forming the graphene are provided. A power storage device with high charge discharge capacity and favorable electric properties such as high reliability and high durability and a method for fabricating the power storage device are provided. Chemical reduction and thermal reduction are performed on graphene oxide in this order to form graphene. In the method for fabricating the power storage device including at least a positive electrode, a negative electrode, an electrolytic solution, and a separator, graphene of one or both of a positive electrode and a negative electrode is formed by the forming method of graphene.

Abstract: To provide a highly reliable power storage device. To provide a long-life power storage device. To provide a power storage device electrode having high adhesion with a current collector. To reduce or inhibit electrochemical decomposition of an electrolytic solution or the like on a surface of an electrode. The power storage device electrode includes a current collector and a second electrode layer provided over the current collector and including a second binder and an active material. A first electrode layer including a first binder and conductive particles is provided between the current collector and the second electrode layer. At least part of a surface of the active material is provided with a coating film, and the coating film is porous.

Abstract: To increase the volume density or weight density of lithium ions that can be received and released in and from a positive electrode active material to achieve high capacity and high energy density of a secondary battery. A lithium manganese composite oxide represented by LixMnyMzOw that includes a region belonging to a space group C2/c and is covered with a carbon-containing layer is used as the positive electrode active material. The element M is an element other than lithium and manganese. The lithium manganese composite oxide has high structural stability and high capacity.

Abstract: The volume density or weight density of lithium ions that can be received and released in and from a positive electrode active material is increased to achieve high capacity and high energy density of a secondary battery. In a lithium manganese composite oxide, each particle includes a first region including a crystal with a layered rock-salt crystal structure and a second region including a crystal with a spinel crystal structure. The second region is in contact with the outside of the first region. The lithium manganese composite oxide has high structural stability and high capacity.

Abstract: A first precipitate is formed by mixing graphite and an oxidizer containing an alkali metal salt in a solution. Next, a second precipitate is formed by ionizing the oxidizer which is included in the first precipitate, with an acid solution, and removing the oxidizer from the first precipitate. Then, a dispersion liquid in which graphene oxide is dispersed is prepared by mixing the second precipitate and water to form a mixed solution and then applying ultrasonic waves to the mixed solution or mechanically stirring the mixed solution, so that the graphene oxide is separated from graphite oxide that is the graphite which is included in the second precipitate and oxidized. Next, graphene oxide salt is formed by mixing the dispersion liquid, a basic solution, and an organic solvent and reacting the graphene oxide included in the dispersion liquid and a base included in the basic solution to each other.