Separate Control of Electrolyte Wetting and Prelithiation Reaction of Silicon Monoxide-Carbon Nanotube Anodes for Lithium-Ion Batteries

Prelithiation is an essential procedure for applying silicon monoxide (SiO) anode materials to lithium-ion batteries (LIBs) because it compensates for the irreversible active lithium loss during the initial cycles and enhances the overall specific capacity of the cell. In this study, a rational prelithiation process for carbon-coated SiO (SiO/C)–carbon nanotube (CNT) sponge anodes was designed by separating the wetting of the electrode from the lithiation of the SiO active materials. A highly viscous 3.47 M lithium bis(fluorosulfonyl)imide (LiFSI) in 1,2-dimethoxyethane (DME) was used as the prelithiation electrolyte. Initially, the optimal conditions were determined to be 12 h of wetting followed by 6 h of lithiation. To further improve the wetting efficiency, an open-wetting method was proposed. A dilute and less viscous electrolyte of 1 M LiFSI/DME was used to facilitate rapid wetting of the electrode in 1.5 h. Subsequently, lithiation was conducted by placing the electrode in contact with a Li foil for 6 h. This separated wetting and lithiation reaction strategy significantly reduces the overall process time from 24 to 7.5 h, while improving the cycling performance (>1200 mA h gSiO–1 for 100 cycles) and reproducibility and avoiding excess solid-electrolyte interphase formation. Finally, full cells were fabricated and evaluated by combining the SiO/C–CNT anode with a Li2S8–CNT cathode. The simple and fast prelithiation condition with open wetting for 1.5 h followed by prelithiation for 6 h yielded the full cell with the highest cycle performance, demonstrating that the prelithiation method developed in this work makes the SiO/C–CNT anode compatible with the Li-lean/free sulfur-based cathodes. This study provides a promising strategy for expanding the practical applications of SiO-based anodes in next-generation LIBs.