Nonaqueous electrolyte secondary battery

摘要

In a wound electrode group, a positive electrode includes positive electrode active material layers formed on both surfaces of a band-like positive electrode current collector, and a negative electrode includes negative electrode active material layers on both surfaces of a band-like negative electrode current collector. Charge capacity of the negative electrode falls within a range of 83-99% of theoretical capacity of the negative electrode in a full charge state of a nonaqueous electrolyte secondary battery. An active material mass M1 per unit area of a negative electrode active material layer formed on an outer circumference of the negative electrode current collector, and an active material mass M2 per unit area of a negative electrode active material layer formed on an inner circumference satisfy a relational expression of M1/M2<(R1+t/2)/(R1−t/2), where the electrode group has an innermost diameter of R1, and the negative electrode has a thickness of t.

主权项

1. A nonaqueous electrolyte secondary battery comprising:
an electrode group formed by winding a positive electrode and a negative electrode with a porous insulating layer interposed therebetween, wherein the positive electrode includes positive electrode active material layers on both surfaces of a band-like positive electrode current collector, the negative electrode includes negative electrode active material layers on both surfaces of a band-like negative electrode current collector, charge capacity of the negative electrode falls within a range of 83-99% of theoretical capacity of the negative electrode in a full charge state of the nonaqueous electrolyte secondary battery, and an active material mass M1 per unit area of one of the negative electrode active material layers, which is formed on an outer circumference of the negative electrode current collector, and an active material mass M2 per unit area of the other of the negative electrode active material layers, which is formed on an inner circumference of the negative electrode current collector, satisfy a relational expression of
M1/M2<(R1+t/2)/(R1−t/2),where the electrode group has an innermost diameter of R1, and the negative electrode has a thickness of t.