Patent ID: 7592099

Claim:
An electrode for a lithium secondary battery, comprising: a current collector composed of a metal that does not alloy with Li, said current collector superficially having irregularities having an arithmetical mean roughness Ra of 0.1 μm or greater; and a thin film, provided on the current collector, of an active material that alloys with Li, said thin film superficially having irregularities formed corresponding to the current-collector surface irregularities, and having a first phase that reacts with Li dominantly and a second phase that reacts less readily with Li than the first phase, the second phase existing at least before initial-cycle charging and after discharging in each cycle following the initial cycle; wherein by the charging and discharging of the electrode in the initial cycle and thereafter, gaps dividing the thin film into columnar or insular structures form along the thin-film thickness on lines connecting valleys in the thin-film surface irregularities and valleys in the current-collector surface irregularities.