Enhancing Charging Efficiency with Lithium Silicate in Silicon Composite Anode Materials Through Lithiothermic Reduction Reaction Synthesis

This study synthesizes silicon (Si) powders with lithium silicates including lithium orthosilicate (Li₄SiO₄), lithium metasilicate (Li₂SiO₃), and lithium disilicate (Li₂Si₂O₅), creating a composite structure of crystalline Si within a Li_xSi_yO_z matrix through the lithiothermic reduction reaction (LTRR) process. The reduction of Li-ion consumption of the anode is investigated by 1) initial solid electrolyte interphase (SEI) layer formation, 2) SEI layer formation in response to Si expansion-induced damage, 3) trapping of Li ions at Si defects, and 4) side reactions during initial charge and discharge cycles. Si/Li_xSi_yO_z electrode exhibits a specific capacity of 1522.2 mAh g⁻¹ and an initial coulombic efficiency of 83.5%. The effect of the calendering process is observed, and a pressurization condition of 5000 kgf cm⁻² or less is set, and the ICE is improved to 93.4%–96%. Si/Li_xSi_yO_z electrodes outperform pure crystalline Si electrodes in specific capacity (7.3%), ICE (42%), and retention characteristics (17%). The integration of the Li_xSi_yO_z matrix into Si anodes enhances Li-ion transport and partially suppresses Si expansion. Additionally, the Si/Li_xSi_yO_z electrode exhibits superior rate capability in the 0.2–1.6 A g⁻¹ range.