Carbon/LiF-Rich Interfaces Constructed from Lithiation of Fluorinated Carbon Coating on Microsized Silicon Anodes

Microsized silicon particles (Si-MPs) are candidate anodes for lithium-ion batteries, but they suffer from severe volume change during charge/discharge and low electrical conductivity, leading to rapid capacity decay and limited rate capability. Here we address these critical challenges by encapsulating Si-MPs within dual-layer coatings of compact carbon layer and LiF-rich solid electrolyte interface (SEI), which are realized by the electrochemical reduction of fluorinated carbon (FC) precoated on Si-MPs. The formation of LiF via the lithiation of C–F bonds within FC, rather than the electrolyte decomposition, as encountered conventionally, enriches LiF in the inner region of SEI and reduces electrolyte consumption. The dual-layer structure preserves electrode integrity and improves conductivity, allowing the Si-MP anode to deliver 80.8% capacity retention after 500 cycles at 4.0 mAh cm^–2 and to maintain capacities of 2031.9, 1736.3, 1189.7, and 813.8 mAh g^–1 at 0.2 C, 1 C, 3 C, and 5 C, respectively.