Improving the Electrochemical Properties of SiO_x Anode for High-Performance Lithium-Ion Batteries by Magnesiothermic Reduction and Prelithiation

For lithium-ion batteries, silicon monoxide is a potential anode material, but its application is limited by its relatively large irreversible capacity loss, which leads to its low initial Coulombic efficiency (ICE). In this study, we conduct a two-step reaction for the formation of silicon oxide-based materials, including a magnesiothermic reduction of SiO x with Mg, followed by the solid-state lithiation of silicon oxide with Li 2 CO 3 . Our results demonstrate that Mg can reduce SiO 2 to Si and form MgSiO 3, while Li 2 CO 3 reacts with SiO x to form Li 2 Si 2 O 5 . MgSiO 3 and Li 2 Si 2 O 5 on the surface of SiO x can effectively mitigate the irreversible loss of lithium ions, thus enhancing the ICE of SiO x . The resulting SiO x –Mg–Li 2 CO 3 –C nanostructure has an ICE of up to 91.1% and a relatively stable cycle performance. After 100 cycles at 0.5 C, the capacity is still 894.5 mAh g –1, and the capacity retention rate is 87.9%. A lithium-ion full battery with the commercial LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NCM811) as the cathode was assembled to test its practical applicability. The full cell exhibits a stable discharge capacity of 91.4 mAh g –1 after 100 cycles at 1 C, with a capacity retention of 79.9%.