Improving the Electrochemical Properties of SiO _<i>x</i> /Graphite Anode for High‐Performance Lithium‐Ion Batteries by Ultrathin Lithium Film Prelithiation

ABSTRACT High‐capacity SiO x /graphite (SiO/G) anodes offer great potential for advancing lithium‐ion battery technology; however, their practical application is limited by low initial coulombic efficiency (ICE) and rapid capacity decay. These challenges primarily arise from unstable phase transitions and the formation of the solid electrolyte interphase (SEI). Prelithiation strategies that aimed at compensating lithium loss have emerged as an effective solution, showing significant advancements in both anode and cathode research. Nevertheless, the interfacial evolution and mechanisms underlying performance enhancement remain unclear. In this work, we demonstrate roll‐to‐roll contact prelithiation of SiO/G anodes using an ultrathin lithium film, resulting in improved ICE, cycling stability, and rate capability. The contact prelithiation mechanism of silicon‐based anodes was investigated via a combination of in situ and ex situ characterizations alongside electrochemical analyses. These studies reveal that the formation of SEI contains multiple lithium silicate phases during the first cycle of prelithiation. This SEI exhibits enhanced conductivity and stability, which contribute to improved cycling performance and rate capability of the prelithiated anode. The prelithiated silicon‐carbon composite anode achieved an ICE of 96% in 5.4 Ah pouch cell tests and demonstrated excellent capacity retention of 74% after 500 cycles. This study not only elucidates the critical role of interfacial evolution in SiO x /graphite anodes but also proposes a rational strategy based on phase–phase interface synergistic design for developing durable, high‐performance silicon‐based anodes suitable for next‐generation lithium‐ion batteries.