Thermally Annealed Co2MnAl Thin-Film Electrode for Lithium Secondary Batteries

A 360 nm thick thin film was electrochemically cycled with excellent capacity retention as an anode for lithium-ion batteries. The as-deposited film, which was amorphous, exhibited a large initial discharge capacity ( at ), which quickly deteriorated during cycling. The initial discharge capacity of the electrode progressively dropped when the film was annealed at ; however, the capacity retention was markedly improved by the annealing. The optimum annealing temperature was at which was maintained throughout 50 cycles. The structural analysis and magnetic properties suggest that the lithium ions induced the Co atoms to segregate during cycling, which led to the capacity degradation of the amorphous electrode. The thermal annealing of the film improved the cycling stability by segregating the Co and Mn atoms through crystallization before cycling.