Improving the Electrochemical Properties of SiO_<i>x</i> 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_<i>x</i> 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 SiO_<i>x</i> to form Li₂Si₂O₅. MgSiO₃ and Li₂Si₂O₅ on the surface of SiO_<i>x</i> can effectively mitigate the irreversible loss of lithium ions, thus enhancing the ICE of SiO_<i>x</i>. The resulting SiO_<i>x</i>-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 LiNi_0.8Mn_0.1Co_0.1O₂ (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%.