Negative electrode materials for non-aqueous electrolyte secondary batteries and said batteries employing the same materials

摘要

A material of the negative electrode for the non-aqueous electrolyte secondary battery comprises solid phases A and B. A core is formed by the solid phase A of which lithium absorption and desorption amount resulted from charge and discharge is relatively large. The core is partially or entirely wrapped with the solid phase B of which lithium absorption and disorption amount resulted from charge and discharge is not so much as the solid phase A, however, of which discharge capacity decrease a little resulted from cycles. The solid phase A comprises one of the following materials; lithium, at least one of the elements which is able to alloy with lithium, solid solution including at least one of the above elements being able to alloy with lithium, or an intermetallic compound including at least one of the above elements being able to alloy with lithium. The solid phase B has a different composition, but comprises the same kind of materials except lithium by itself as those of the solid phase A. It is essential that the solid phase B is a mixed conductor having electronic conductivity as well as lithium ionic conductivity. When these materials are used in the negative electrode, the non-aqueous electrolyte second battery featuring a high reliability in the safety aspect, high cycle characteristic, a high capacity and excellent high-rate charge and discharge characteristic can be realized.