Current density induced growth of Li15Si4 alloy in silicon-carbon anodes during first lithiation process

Abstract

Li15Si4 alloy growth in silicon-carbon anode materials of lithium ion battery influences the subsequent electrochemical performances, so it's important to investigate Li15Si4 alloy growth during first lithiation process. Yolk-shell nano silicon-carbon particles are assembled with liquid electrolyte in coin-cells under moderate pressure. Li15Si4 alloy is firstly detected at 60 mV (vs Li/Li+) at the current density of 0.1 A g−1, but at 120 mV (vs Li/Li+) at the current density of 1 A g−1 (strictly speaking, Li15Si4 alloy growth at higher voltages cannot be absolutely excluded, but these detections demonstrate the big possibility at the potential), indicating growth potential of Li15Si4 alloy can be higher than 60 mV which was reported in previous literatures. Additionally, Li15Si4 alloy distribution is heterogeneous. The variable potential of Li15Si4 alloy growth is elucidated by TEM characterization and qualitative numerical simulation. The research is benefit for a deep understanding on lithiation behaviors of silicon-based anodes.