Thermally Annealed Co2MnAl Thin-Film Electrode for Lithium Secondary Batteries

Abstract

A 360 nm thick Co2MnAl thin film was electrochemically cycled with excellent capacity retention as an anode for lithium-ion batteries. The as-deposited Co2MnAl film, which was amorphous, exhibited a large initial discharge capacity (920 mAh g(-1) at 0.02 mA cm(-2)), which quickly deteriorated during cycling. The initial discharge capacity of the electrode progressively dropped when the film was annealed at 100-500 degrees C; however, the capacity retention was markedly improved by the annealing. The optimum annealing temperature was 300 degrees C at which 430 mAh g(-1) 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.