US Patent 7781099 Non-aqueous electrolyte secondary cell

The present invention provides a non-aqueous electrolyte secondary battery having high energy density and satisfactory cycle performance by using an alloy comprising Ni and Sn as a negative active material. The non-aqueous electrolyte secondary battery comprises a negative electrode with a composite layer containing a negative active material, a positive electrode and a non-aqueous electrolyte. The negative active material consists of an alloy containing 5 to 25 mass % of nickel and 75 to 95 mass % of tin and the alloy contains Sn4Ni3 phase and Sn phase. It is preferable that the content ratio of Sn4Ni3 phase and Sn phase in the alloy be 0.2≦Z≦3, when m1 is the mass of Sn4Ni3 phase, m2 is the mass of said Sn phase, and Z=ml /m2; and that the composite layer contain carbon material.