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 for a secondary battery which enables both good battery characteristics and electrode strength at a predetermined level, a secondary battery, and a method for fabricating the positive electrode for a secondary battery are provided. The positive electrode for a secondary battery includes a current collector and an active material layer over the current collector. The active material layer includes an active material, graphene, and a binder. A carbon layer is on a surface of the active material. The proportion of the graphene in the active material layer is greater than or equal to 0.1 wt % and less than or equal to 1.0 wt %.

Abstract: A method for synthesizing alkali metal silicate which can be easily microparticulated, a method for synthesizing, with the use of the alkali metal silicate, alkali transition metal silicate, and alkali metal silicate and alkali transition metal silicate which are synthesized by the synthesis methods are disclosed. The alkali metal silicate is synthesized by the following steps: forming a basic solution including an alkali metal salt; mixing the basic solution including the alkali metal salt with silicon particles to form a basic solution including the alkali metal silicate; and adding the basic solution including the alkali metal silicate to a poor solvent for the alkali metal silicate to precipitate the alkali metal silicate. Further, the alkali metal silicate is mixed with a microparticulated compound including a transition metal to form a mixture, and the mixture is subjected to heat treatment, whereby the alkali transition metal silicate is generated.

Abstract: An object is to provide an electrode material with high electrical conductivity and a power storage device using the electrode material. An object is to provide an electrode material with high capacity and a power storage device using the electrode material. Provided is a particulate electrode material including a core containing a compound represented by a general formula Li2MSiO4 (in the formula, M represents at least one kind of an element selected from Fe, Co, Mn, and Ni) as a main component, and a covering layer containing a compound represented by a general formula LiMPO4 as a main component and covering the core. Further, a solid solution material is provided between the core and the covering layer. With such a structure, an electrode material with high electrical conductivity can be obtained. Further, with such an electrode material, a power storage device with high discharge capacity can be obtained.

Abstract: An object is to improve the characteristics of a power storage device such as a charging and discharging rate or a charge and discharge capacity. The grain size of particles of a positive electrode active material is nano-sized so that a surface area per unit mass of the active material is increased. Specifically, the grain size is set to greater than or equal to 10 nm and less than or equal to 100 nm, preferably greater than or equal to 20 nm and less than or equal to 60 nm. Alternatively, the surface area per unit mass is set to 10 m2/g or more, preferably 20 m2/g or more. Further, the crystallinity of the active material is increased by setting an XRD half width to greater than or equal to 0.12° and less than 0.17°, preferably greater than or equal to 0.13° and less than 0.16°.

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: A flexible power storage device or a power storage device of which the capacity and cycle characteristics do not easily deteriorate even when the power storage device is curved is provided. An electrode in which an active material layer, a current collector, and a friction layer are stacked in this order is provided. Furthermore, a power storage device that includes the electrode as at least one of a positive electrode and a negative electrode is provided.

Abstract: A positive electrode for a secondary battery which enables both good battery characteristics and electrode strength at a predetermined level, a secondary battery, and a method for fabricating the positive electrode for a secondary battery are provided. The positive electrode for a secondary battery includes a current collector and an active material layer over the current collector. The active material layer includes an active material, graphene, and a binder. A carbon layer is on a surface of the active material. The proportion of the graphene in the active material layer is greater than or equal to 0.1 wt % and less than or equal to 1.0 wt %.

Abstract: To provide a method of manufacturing a lithium-ion secondary battery having stable charge characteristics and lifetime characteristics. A positive electrode is subjected to an electrochemical reaction in a large amount of electrolytic solution in advance before a secondary battery is completed. In this manner, the positive electrode can have stability. The use of the positive electrode enables manufacture of a highly reliable secondary battery. Similarly, a negative electrode is subjected to an electrochemical reaction in a large amount of electrolytic solution in advance. The use of the negative electrode enables manufacture of a highly reliable secondary battery.

Abstract: To provide a positive electrode for a lithium-ion secondary battery, which is highly filled with a positive electrode active material and has a high-density positive electrode active material layer. To provide a lithium-ion secondary battery having high capacity and improved cycle characteristics with use of the positive electrode. After graphene oxide is dispersed in a dispersion medium, a positive electrode active material is added and mixed to form a mixture. A binder is added to the mixture and mixed to form a positive electrode paste. The positive electrode paste is applied to a positive electrode current collector and the dispersion medium contained in the positive electrode paste is evaporated, and then, the graphene oxide is reduced, so that a positive electrode active material layer containing graphene is formed over the positive electrode current collector.

Abstract: To provide a lithium-ion storage battery or electronic device that is flexible and highly safe. One embodiment of the present invention is a flexible storage battery including a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, an exterior body that surrounds the positive electrode, the negative electrode, and the separator, and a wiring provided along the exterior body. At least part of the wiring is more easily breakable by deformation than the exterior body. The wiring is more vulnerable to deformation than the exterior body and thus damaged earlier than the exterior body. Damage to the wiring is detected and an alert is sent to a user; thus, the use of the storage battery can be stopped before the exterior body is damaged.

Abstract: An object is to improve the characteristics of a power storage device such as a charging and discharging rate or a charge and discharge capacity. The grain size of particles of a positive electrode active material is nano-sized so that a surface area per unit mass of the active material is increased. Specifically, the grain size is set to greater than or equal to 10 nm and less than or equal to 100 nm, preferably greater than or equal to 20 nm and less than or equal to 60 nm. Alternatively, the surface area per unit mass is set to 10 m2/g or more, preferably 20 m2/g or more. Further, the crystallinity of the active material is increased by setting an XRD half width to greater than or equal to 0.12° and less than 0.17°, preferably greater than or equal to 0.13° and less than 0.16°.

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 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: In a manufacturing process of a positive electrode active material for a power storage device, which includes a lithium silicate compound represented by a general formula Li2MSiO4, heat treatment is performed at a high temperature on a mixture material, grinding treatment is performed, a carbon-based material is added, and then heat treatment is performed again. Therefore, the reactivity between the substances contained in the mixture material is enhanced, favorable crystallinity can be obtained, and further microparticulation of the grain size of crystal which is grown larger by the high temperature treatment and crystallinity recovery are achieved; and at the same time, carbon can be supported on the surfaces of particles of the crystallized mixture material. Accordingly, a positive electrode active material for a power storage device, in which electron conductivity is improved, can be manufactured.

Abstract: In a manufacturing process of a positive electrode active material for a power storage device, which includes a lithium silicate compound represented by a general formula Li2MSiO4, heat treatment is performed at a high temperature on a mixture material, grinding treatment is performed, a carbon-based material is added, and then heat treatment is performed again. Therefore, the reactivity between the substances contained in the mixture material is enhanced, favorable crystallinity can be obtained, and further microparticulation of the grain size of crystal which is grown larger by the high temperature treatment and crystallinity recovery are achieved; and at the same time, carbon can be supported on the surfaces of particles of the crystallized mixture material. Accordingly, a positive electrode active material for a power storage device, in which electron conductivity is improved, can be manufactured.

Abstract: An object is to increase the amount of ions capable of entering and leaving a positive electrode active material in an ion battery so that the capacity of the battery is increased. When a solid solution including alkali metal oxide having electrical conductivity less than or equal to 10?10 S/cm and including alkali metal with a valence of 2 or more, and alkali metal oxide having electrical conductivity greater than or equal to 1×10?6 S/cm and less than or equal to 3×10?6 S/cm is used as a positive electrode active material in an ion battery, the amount of ions capable of entering and leaving the positive electrode active material is increased, so that the capacity of the battery is increased.

Abstract: A positive electrode for a nonaqueous secondary battery including an active material layer which has sufficient electron conductivity with a low ratio of a conductive additive is provided. A positive electrode for a nonaqueous secondary battery including an active material layer which is highly filled with an active material, id est, including the active material and a low ratio of a conductive additive. The active material layer includes a plurality of particles of an active material with a layered rock salt structure, graphene that is in surface contact with the plurality of particles of the active material, and a binder.

Abstract: One object is to provide a manufacturing method of an electrode material with which a characteristic of a power storage device can be improved. In a manufacturing method of an electrode material comprising a compound represented by a general formula A2-aMSiO4 (A represents an alkali metal, M represents a transition metal, and a represents 0?a<2), a mixed material is formed by mixing a compound that is a supply source of A, a compound that is a supply source of M, and a compound that is a supply source of Si; a flux is mixed into the mixed material after the mixed material is subjected to a heat treatment at a temperature of 400° C. or lower and pulverized; and the mixed material into which the flux is mixed is subjected to a heat treatment at a temperature of 700° C. or lower in an inert gas atmosphere.

Abstract: As a positive electrode active material, a material which is represented by the general formula Li(2-x)M1yM2zSiO4 and satisfies the conditions (I) to (IV) is used: (I) x is a value which changes due to insertion and extraction of a lithium ion during charging and discharging, and satisfies 0?x<2; (II) M1 is one or more transition metal atoms selected from iron (Fe), nickel (Ni), manganese (Mn), and cobalt (Co); (III) M2 is a metal atom that is titanium (Ti), scandium (Sc), or magnesium (Mg); and (IV) The formulae y+z=1, 0<y<1, and 0<z<1 are satisfied. The value of z/(y+z) is greater than or equal to 0.01 and less than or equal to 0.2.