Patent ID: 8409752

Claim:
An active material for a battery, comprising: an electrochemically reversibly oxidizable and reducible base material selected from the group consisting of a lithium-containing metal oxide, and a lithium-containing chalcogenide compound; and a surface-treatment layer formed on the base material and comprising a solid-solution compound including surface treating elements M and X, and a compound of the formula MXO k , wherein: M is at least one element selected from the group consisting of an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, and a rare-earth element, X is an element that is capable of forming a double bond with oxygen, and k is a numerical value in the range of 2 to 4, and an oxide comprising Li, M, and Co being present between the surface-treatment layer and the base material.