Patent ID: 8669009

Claim:
A positive electrode active material of a power storage device, wherein the positive electrode active material is represented by a general formula Li (2-x,) M1 y M2 z SiO 4 and satisfies conditions (I) to (IV): (I) x satisfies 0≦x <2 (x is greater than or equal to 0 and less than 2); (II) M1 is one or more 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) Formulae y+z≈1, 0<y<1, and 0<z<1 are satisfied, and also the value of z/(y+z) is greater than or equal to 0.01 and less than or equal to 0.2, and wherein the positive electrode active material satisfies at least one of conditions (V) and (VI): (V) The positive electrode active material has a crystal structure belongs to the space group P121/n1; and (VI) The positive electrode active material has a crystal structure belongs to the space group Pmn21.