Targeted Multifunctional Fluorine-Rich Copolymer Coating Design for Ambient-Stable Prelithiated SiOC Anodes

Prelithiation is a pivotal strategy for enhancing the initial coulombic efficiency (ICE) and energy density of lithium-ion batteries, yet its practical application is impeded by the pronounciked sensitivity of prelithiated electrodes to ambient moisture and oxygen during storage. Herein, we rationally devise a targeted design for a fluorine-rich acrylate copolymer-poly (tridecafluorooctyl methacrylate-co-methyl methacrylate) (PFMMA)-and introduce it as a multifunctional protective coating, with Li₁₃Si₄-prelithiated SiOC electrodes (preSiOC) employed as a proof of concept. Fluorinated side chains impart strong hydrophobicity, while methyl methacrylate units retain electrolyte affinity; the two moieties act synergistically to stabilize electrodes in air and preserve unimpeded interfacial ion/charge transport during redox reactions. Consequently, the preSiOC/PFMMA electrode with a 540 nm-thick PFMMA coating retains 97.4% capacity and 95.3% ICE after 48 h air exposure at 50% relative humidity (RH), alongside robust cycling stability (677.5 mAh·g^-1 after 100 cycles). These results outperform both unprotected preSiOC and other reported conventionally protected prelithiated electrodes. Furthermore, the electrode shows exceptional environmental adaptability, maintaining functionality under extreme scenarios (10% RH for 100 days or 90% RH for 3 days). This study establishes a rational copolymer design paradigm for fabricating durable, electrolyte-compatible interfaces, thereby accelerating the development of ambient-stable prelithiated electrodes.