Unshackling the reversible capacity of SiOx/graphite-based full cells via selective LiF-induced lithiation

Abstract

Composite Si@SiOxC anodes with high specific capacity are considered the most promising alternatives to graphite in industrial lithium-ion batteries. However, their cycling stability remains a limiting factor, which originates from the severe volume deformation of silicon-derived species. In this work, the cyclabilities of composite anodes are improved by unshackling the highly reversible lithium storage capabilities from the redundancy capacity of the anode materials. A selective LiF-induced lithiation strategy is proposed based on exploiting interface separation energy differences between LiF and the active materials. An interesting preferential redeposition of LiF is observed at the Si@SiOx particles, which differentiates the otherwise similar lithiation potentials of LiCx and Li15Si4, thereby enabling lithium storage in graphite that was previously underused. The resulting full cell exhibits better rate and cycling performances without sacrificing specific capacity. In an ultra-high area capacity full cell (4.9 mA h cm−2), the capacity retention increases markedly from 66.1% to 94.2% after 300 cycles. The selective lithiation strategy developed herein is feasible for practical industrial applications, and importantly, it requires no changes to the existing mature lithium-ion battery manufacturing process. This study offers a new approach for the development of silicon/graphite composite anodes with long cycling lifetimes.