Germanium Silicon Alloy Anode Material Capable of Tunable Overpotential by Nanoscale Si Segregation

Abstract

We developed the novel electrode that enables fine control of overpotential by exploiting surface segregation that is the enrichment of one component at the surface of binary alloy. To realize this approach, we controlled the proportion of Si with low Li diffusivity at the surface by annealing the SiGe nanowire in H-2 environment at various temperatures. The resulting SiGe nanowires annealed at 850 degrees C exhibited high reversible capacity (>1031 mA.h.g(-1)), and long cycle life (400 cycles) with high opacity retention (89.0%) at 0.2 C. This superior battery performance is attributed to the remaining unlithiated part acting as support frame to prevent pulverization of anode material, which results from the fine-tuning of overpotential by controlling the degree of Si segregation.