Electrodeposited thin-film CuxSb anodes for Li-ion batteries: enhancement of cycle life via tuning of film composition and engineering of the film-substrate interface

Electrodeposited Cu-Sb thin films on Cu and Ni substrates are investigated as alloy anodes for Li-ion batteries to elucidate the effects of both the film composition and substrate interactions on anode cycling stability and lifetime. Thin films of composition CuxSb (0 < x < 2) exhibit the longest cycle lifetimes nearest x = 1. Additionally, the Cu-Sb films exhibit shorter cycle lifetimes when electrodeposited onto Cu substrates when compared to equivalent films on Ni substrates. Ex situ characterization and differential capacity analysis of the anodes reveal that significant interdiffusion occurs during cycling between pure Sb films and Cu substrates. The great extent of interdiffusion results in mechanical weakening of the film-substrate interface that exacerbates film delamination and decreases cycle lifetimes of Cu-Sb films on Cu substrates regardless of the film's composition. The results presented here demonstrate that the composition of the anode alone is not the most important predictor of long term cycle stability; the composition coupled with the identity of the substrate is key. These interactions are critical to understand in the design of high capacity, large volume change materials fabricated without the need for additional binders.