Prelithiated Silicon Alloy (Si-Fe-Mn): Dodging the Irreversible Capacity Loss for High Performance Lithium Ion Batteries

In this work, silicon alloy (Si-Fe-Mn) was pretreated with a number of lithium compounds and investigated on improvements in electrochemical properties for high efficiency and better capacity retention. The motivation was to prefill the cracks and any voids of the silicon alloy with lithium-based compounds, to avoid unnecessary solid electrolyte interface (SEI) reformations, and thus to dodge the capacity drains to a certain extent. Prelithiation was performed by simply heat treating the grounded mixture of silicon alloy and lithium compounds. The temperature for heat treatment was maintained slightly above the melting point of the lithium compound to allow diffusion into the cracks and voids of silicon alloy. Lithium stearate (C 18 H 35 LiO 2 ), lithium carbonate (Li 2 CO 3 ), lithium tetrafluoroborate (LiBF 4 ), and lithium nitride (Li 3 N) were chosen for prelithiation. Investigations were performed by changing the chemicals and amount of the materials, heat treatment temperature, and the order of the processes. Out of which, silicon alloy with 5 wt.% lithium stearate treated at 300°C for 4 hours demonstrated the best electrochemical performance.