Lithium ion battery

Abstract

Provided is a lithium ion battery whose manufacturing process is simple and which has high energy density and heat resistance. A lithium ion battery capable of storing and releasing lithium ions, and being provided with a separator between a positive electrode and a negative electrode having irreversible capacity at the initial charge/discharge, and having a structure in which void portions in the separator are filled with a nonaqueous electrolytic solution including lithium ions, wherein a positive electrode active material contained in the positive electrode has a first charge-discharge efficiency of 80% to 90% when charged/discharged using metal Li as an counter electrode; a negative electrode active material contained in the negative electrode includes a mixed material of a silicon compound and a carbon material; in the negative electrode, lithium corresponding to an irreversible capacity at the initial charge/discharge is not doped; a capacity ratio of the negative electrode to the positive electrode at the initial electric charge capacity of the positive electrode and the negative electrode is 0.95 or more and 1 or less; the positive electrode binder contained in the positive electrode is an aqueous binder; the negative electrode binder contained in the negative electrode is a polyimide; and the nonaqueous electrolyte contains lithium bis(oxalate) borate.