Irreversible capacity which causes a decrease in the initial capacity of a power storage device is reduced and the electrochemical decomposition of an electrolytic solution is suppressed. The decomposition reaction of an electrolytic solution as a side reaction of a power storage device is reduced or suppressed to improve the cycle performance of the power storage device. An electrode material for a power storage device includes active material particles and coating films covering part of surfaces of the active material particles. Carrier ions used for the power storage device can pass through the coating film. The product of the electric resistivity and the thickness of the coating film at 25° C. is greater than or equal to 20 &OHgr;m·m.
