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: 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.

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. Another object is to provide a power storage device to which the above-mentioned electrode material is applied, and an application mode thereof. 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 of the general formula, a compound that is a supply source of M of the general formula, and a compound that is a supply source of Si of the general formula; 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.

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 provide a power storage device with high discharge capacity and high energy density. The power storage device includes a positive electrode in which a positive electrode active material is formed over a positive electrode current collector; and a negative electrode which faces the positive electrode with an electrolyte interposed therebetween. The positive electrode active material includes a film-form first region which includes a compound containing lithium and nickel; and a film-form second region which includes a compound containing lithium and one or more of iron, manganese, and cobalt, but not containing nickel. The first region is covered with the second region. Since a superficial portion of the positive electrode active material does not contain nickel, nickel is not in contact with an electrolyte solution; thus, generation of a catalyst effect of nickel can be suppressed, and a high discharge potential of nickel can be utilized.

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 power storage device including a positive electrode having a positive electrode active material and a positive electrode current collector; and a negative electrode which faces the positive electrode with an electrolyte provided between the negative electrode and the positive electrode is provided. The positive electrode active material includes a first region which includes a phosphate compound containing lithium and nickel; and a second region which covers the first region and includes a compound containing lithium and one or more of iron, manganese, and cobalt, but not containing nickel. Since the entire superficial portion of a particle of the positive electrode active material does not contain nickel, nickel is not in contact with an electrolyte solution; thus, generation of a catalyst effect of nickel can be suppressed, and a high discharge potential of nickel can be utilized.

Abstract: A power storage device includes a positive electrode including a positive electrode current collector and a positive electrode active material having an olivine structure which is represented by a structural formula LiFexMe1-xPO4 (Me=Mn, Ni, or Co) (x is greater than 0 and less than 1) over the positive electrode current collector, or a power storage device includes a positive electrode including a positive electrode current collector and a positive electrode active material, and a negative electrode which faces the positive electrode through an electrolyte, where discharging capacitance is greater than or equal to 150 mAh/g and energy density per unit weight is higher than or equal to 500 mWh/g.

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 power storage device comprising a positive electrode which includes in a positive electrode active material layer, lithium iron phosphate particles whose surface is supported by a carbon material and whose half width of the X-ray diffraction peak is less than or equal to 0.17°, or greater than or equal to 0.13° and less than or equal to 0.165? or whose particle size is greater than or equal to 20 nm and less than 50 nm or greater than or equal to 30 nm and less than 40 nm; or a method for manufacturing a power storage device comprising the steps of mixing the lithium iron phosphate particles, a conduction auxiliary agent, and a binder so as to be a paste, and applying the paste on a current collector, thereby manufacturing a positive electrode.