Sequencing‐Dependent Impact of Carbon Coating on Microstructure Evolution and Electrochemical Performance of Pre‐lithiated SiO Anodes: Enhanced Efficiency and Stability via Pre‐Coating Strategy

Abstract

Silicon monoxide (SiO) has attracted considerable interest as anode material for lithium‐ion batteries (LIBs). However, their poor initial Coulombic efficiency (ICE) and conductivity limit large‐scale applications. Prelithiation and carbon‐coating are common and effective strategies in industry for enhancing the electrochemical performance of SiO. However, the involved heat‐treatment processes inevitably lead to coarsening of active silicon phases, posing a significant challenge in industrial applications. Herein, the differences in microstructures and electrochemical performances between prelithiated SiO with a pre‐coated carbon layer (SiO@C@PLi) and SiO subjected to carbon‐coating after prelithiation (SiO@PLi@C) are investigated. A preliminary carbon layer on the surface of SiO before prelithiation is found that can suppress active Si phase coarsening effectively and regulate the post‐prelithiation phase content. The strategic optimization of the sequence where prelithiation and carbon‐coating processes of SiO exert a critical influence on its regulation of microstructure and electrochemical performances. As a result, SiO@C@PLi exhibits a higher ICE of 88.0%, better cycling performance and lower electrode expansion than SiO@PLi@C. The pouch‐type full‐cell tests demonstrate that SiO@C@PLi/Graphite||NCM811 delivers a superior capacity retention of 91% after 500 cycles. This work provides invaluable insights into industrial productions of SiO anodes through optimizing the microstructure of SiO in prelithiation and carbon‐coating processes.