In Situ Formation of LiF-Rich Carbon Interphase on Silicon Particles for Cycle-Stable Battery Anodes

Silicon (Si) is a potential high-capacity anode material for the next-generation lithium-ion battery with high energy density. However, Si anodes suffer from severe interfacial chemistry issues, such as side reactions at the electrode/electrolyte interface, leading to poor electrochemical cycling stability. Herein, we demonstrate the fabrication of a conformal fluorine-containing carbon (FC) layer on Si particles (Si-FC) and its in situ electrochemical conversion into a LiF-rich carbon layer above 1.5 V ( vs . Li + /Li). The as-formed LiF-rich carbon layer not only isolates the active Si and electrolytes, leading to the suppression of side reactions, but also induces the formation of a robust solid–electrolyte interface (SEI), leading to the stable interfacial chemistry of as-designed Si-FC particles. The Si-FC electrode has a high initial Coulombic efficiency (CE) of 84.8% and a high reversible capacity of 1450 mAh/g at 0.4 C (1000 mA/g) for 300 cycles. In addition, a hybrid electrode consisting of 85 wt% graphite and 15 wt% Si-FC, and mass 2.3 mg/cm 2 loading delivers a high areal capacity of 2.0 mAh/cm 2 and a high-capacity retention of 93.2% after 100 cycles, showing the prospects for practical use. Graphical Abstract