Abstract: A power storage device with high output is provided, in which the specific surface area is increased while keeping the easy-to-handle particle size of its active material. The power storage device includes a positive electrode including a positive electrode current collector and a positive electrode active material layer, a negative electrode including a negative electrode current collector and a negative electrode active material layer, and an electrolyte. The negative electrode active material layer includes a negative electrode active material which is a particle in which a plurality of slices of graphite is overlapped with each other with a gap therebetween. It is preferable that the grain diameter of the particle be 1?m to 50 ?m. Further, it is preferable that the electrolyte be in contact with the gap between the slices of graphite.

Abstract: At least one of an aqueous solution A containing lithium, an aqueous solution B containing iron, manganese, cobalt, or nickel, and an aqueous solution C containing a phosphoric acid includes graphene oxide. The aqueous solution A is dripped into the aqueous solution C, so that a mixed solution E including a precipitate D is prepared. The mixed solution E is dripped into the aqueous solution B, so that a mixed solution G including a precipitate F is prepared. The mixed solution G is subjected to heat treatment in a pressurized atmosphere, so that a mixed solution H is prepared, and the mixed solution H is then filtered. Thus, particles of a compound containing lithium and oxygen which have a small size are obtained.

Abstract: An object is to reduce variation in shape of crystals that are to be formed. Solutions containing respective raw materials are made in an environment where an oxygen concentration is lower than that in air, the solutions containing the respective raw materials are mixed in an environment where an oxygen concentration is lower than that in air to form a mixture solution, and with use of the mixture solution, a composite oxide is formed by a hydrothermal method.

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.

Abstract: A negative electrode and a power storage device are provided, which have one of an alloy-based particle and an alloy-based whisker and a carbon film including 1 to 50 graphene layers. A surface of the alloy-based particle or the alloy-based whisker is covered with the carbon film. In addition, a method of manufacturing a negative electrode and a method of manufacturing a power storage device are provided, which have the step of mixing an alloy-based particle or an alloy-based whisker with graphene oxide, and the step of heating the mixture in a vacuum or in a reducing atmosphere.

Abstract: Graphene is formed with a practically uniform thickness on an uneven object. The object is immersed in a graphene oxide solution, and then taken out of the solution and dried; alternatively, the object and an electrode are immersed therein and voltage is applied between the electrode and the object used as an anode. Graphene oxide is negatively charged, and thus is drawn to and deposited on a surface of the object, with a practically uniform thickness. After that, the object is heated in vacuum or a reducing atmosphere, so that the graphene oxide is reduced to be graphene. In this manner, a graphene layer with a practically uniform thickness can be formed even on a surface of the uneven object.

Abstract: The power extraction efficiency of a nonaqueous electrolyte secondary battery such as a lithium ion battery is improved. A material having magnetic susceptibility anisotropy such as an olivine type oxide including a transition metal element is used for active material particles. The active material particles and an electrolyte solution are mixed to form a slurry. The slurry is applied to a current collector, and then the current collector is left in a magnetic field. Thus, the active material particles are oriented. With the use of active material particles oriented in such a manner, the power extraction efficiency can be improved.

Abstract: To provide a power storage device having a solid electrolyte, in which a charge-discharge capacity can be increased, and a method for manufacturing the power storage device. The power storage device includes a positive electrode, a negative electrode, and an electrolyte provided between the positive electrode and the negative electrode, and the electrolyte includes an ion-conductive high molecular compound, an inorganic oxide, and a lithium salt, and the inorganic oxide is included in the electrolyte at more than 30 wt % and 50 wt % or less to the total of the ion-conductive high molecular compound and the inorganic oxide.

Abstract: An energy storage device having high capacity per weight or volume and a positive electrode active material for the energy storage device are manufactured. A surface of a main material included in the positive electrode active material for the energy storage device is coated with two-dimensional carbon. The main material included in the positive electrode active material is coated with a highly conductive material which has a structure expanding two-dimensionally and whose thickness is ignorable, whereby the amount of carbon coating can be reduced and an energy storage device having capacity close to theoretical capacity can be obtained even when a conduction auxiliary agent is not used or the amount of the conduction auxiliary agent is extremely small. Accordingly, the amount of carbon coating in a positive electrode and the volume of the conduction auxiliary agent can be reduced; consequently, the volume of the positive electrode can be reduced.

Abstract: A positive-electrode active material with improved electrical conductivity, and a power storage device using the material are provided. A positive-electrode active material with large capacity, and a power storage device using the material are provided. A core including lithium metal oxide is used as a core of a main material of the positive-electrode active material, and one to ten pieces of graphene is used as a covering layer for the core. A hole is provided for graphene, whereby transmission of a lithium ion is facilitated, resulting in improvement of use efficiency of current.

Abstract: The present invention relates to a solar power generation device which includes an electric double-layer capacitor and a solar cell. The electric double-layer capacitor includes a pair of current collectors formed using a light-transmitting conductive material; active materials which are dispersed on the pair of current collectors; a light-transmitting electrolyte layer which is provided between the pair of current collectors; and a terminal portion which is electrically connected to the current collector. The solar cell includes, over a light-transmitting substrate, a first light-transmitting conductive film; a photoelectric conversion layer which is provided in contact with the first light-transmitting conductive film; and a second light-transmitting conductive film which is provided in contact with the photoelectric conversion layer.