An expeditious chemical pre-lithiation tactic for the enhancement of coulombic efficiency in silicon-based composite films for lithium-ion battery anodes

High Coulombic efficiency is a critical performance indicator for lithium-ion batteries. Silicon thin-film anodes have garnered significant attention due to their advantageous features, including a high specific capacity of 4200 mAh/g and a low lithiation voltage of 0–0.5 V. However, during the initial charge/discharge cycle, the formation of a solid electrolyte interface (SEI) film occurs, which results in the consumption of lithium ions and subsequent irreversible loss of battery capacity and a decline in Coulombic efficiency. In this study, a composite thin-film anode with an amorphous phase is prepared by magnetron sputtering film-forming technology, using lithium titanate as a lithium source and pre-lithiation modification of silicon-based film through RF co-sputtering process to improve the structural stability of the thin-film anode and first-time coulombic efficiency through chemical pre-lithiation. The silicon-lithium titanate composite film exhibits remarkable electrochemical performance , with a reversible capacity of 1489.2 mAh/g, Initial coulombic efficiency of 83.6 %, and capacity retention over 500 cycles. Notably, a reversible capacity of 400 mAh/g is attained at high multiplicity and demonstrated stability after 500 cycles. • This presents a simple and direct pre-lithiation method. • The initial specific capacity of the Si-LTO composite film was 1489.2 mAh/g, with 90.4 % retention after 100 cycles. • The composite film showed excellent structural stability, maintaining 85 % of its capacity after 200 cycles at 4200 mA/g. • The Si-LTO composite film had an average Coulombic efficiency of 99.23 % in the first 100 cycles, with ICE of 83.6 %.