Molten salt-assisted SiO _<i>x</i> prelithiation for high-performance quasi-solid-state batteries

Silicon oxide (SiO_x) anodes have emerged as a promising substitute for graphite anodes owing to their high specific capacity and cost-effectiveness. However, they face challenges including significant volume expansion-induced electrode cracking and unsatisfactory initial Coulombic efficiency. Herein, we use a prelithiation strategy to address these challenges for quasi-solid-state batteries using a garnet-type solid electrolyte. Using a contact-based prelithiation configuration, full prelithiation of SiO_x anodes were achieved through spontaneous lithium-ion intercalation assisted by molten salts. The garnet-type solid electrolyte based full cells are assembled with fully prelithiated SiO_x anodes and LiFePO₄ cathode using molten salts as interface layer. The quasi-solid-state full cells with high initial coulombic efficiency maintain exceptional cycling stability with over 80% capacity retention after 300 cycles. The molten salt modulates the solid electrolyte interphase composition for SiO_x anodes and effectively suppressing SiO_x particle fracture during cycling. This work offers a practical route toward high-energy-density lithium batteries for next-generation energy storage.