Improving the Electrochemical Properties of SiOx 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 SiOx with Mg, followed by the solid-state lithiation of silicon oxide with Li2CO3. Our results demonstrate that Mg can reduce SiO2 to Si and form MgSiO3, while Li2CO3 reacts with SiOx to form Li2Si2O5. MgSiO3 and Li2Si2O5 on the surface of SiOx can effectively mitigate the irreversible loss of lithium ions, thus enhancing the ICE of SiOx. The resulting SiOx–Mg–Li2CO3–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 LiNi0.8Mn0.1Co0.1O2 (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%.