Anion-regulated solvation chemistry constructs LiF-rich CEI for suppressing cathode microcracking in lithium-metal...

High-nickel layered cathodes are susceptible to interfacial side reactions, lattice oxygen release, and microcrack propagation during high-voltage cycling, leading to continuous electrolyte corrosion and rapid degradation of battery performance. To address these issues, we regulated the local solvation structure in the quasi-solid-state electrolyte to create an anion-dominated, locally high-concentration solvation environment (QSPE-AL), which promotes the preferential participation of anions in interfacial reactions and induces the formation of a LiF-rich cathode electrolyte interphase (CEI). The in situ polymerized polymer network provides continuous ion transport channels, which contributes to suppressing interfacial contact issues during the cycling process. The Raman spectroscopy results indicate that in QSPE-AL, more anions enter the first solvation shell around Li⁺. X-ray photoelectronic spectroscopy analysis further confirms that the LiF content in the CEI formed by QSPE-AL has increased remarkably. Owing to its high mechanical strength and interfacial stability, LiF CEI effectively buffers the volumetric stress generated during the cycling of high-nickel cathodes, inhibits the continuous penetration of electrolyte along grain boundaries, and slows the formation and propagation of microcracks in cathode particles. Electrochemical testing reveals that NCM622‖Li batteries using QSPE-AL electrolyte maintain a capacity retention rate of 88% after 300 cycles and continue to exhibit excellent stability even after more than 1000 cycles. This work provides new insights into the interface design of highly stable, high-voltage quasi-solid-state lithium-metal batteries.