Patent ID: 7556881

Claim:
A lithium secondary battery comprising: a negative electrode having a current collector and a thin film made of silicon or a silicon alloy as a negative electrode active material, the thin film being provided on the current collector and divided into columnar structures by gaps that are formed along its thickness, and the bottom portions of the columnar structures being in close contact with the current collector; a positive electrode; a separator; the positive and negative electrodes being overlapped with the separator interposed therebetween, and the positive and negative electrodes and the separator being wound around to form an electrode assembly; a non-aqueous electrolyte; and a battery case accommodating the electrode assembly; wherein the ratio of theoretical capacity per unit area of the negative electrode to charge capacity per unit area of the positive electrode (negative electrode capacity/positive electrode capacity) is within the range of from 1.9 to 4.4.