Iron-based fluorides (IBFs, typically FeF₃ and FeF₂) are potential next generation high energy density cathodes for lithium-ion batteries (LIBs) due to their high specific capacity, cost effectiveness and crustal abundance. However, IBFs decompose electrolyte violently which impedes their practical implementation in LIBs. Herein we report a strategy to embed FeF₂ nanoparticles in an interconnected cyclic polyacrylonitrile (cPAN) network to passivate the cathode/electrolyte interface. Moreover, cPAN affords strong adhesion to both the FeF₂ nanoparticles and the current collector, essentially acting as a binder that is superior to polyvinylidene fluoride (PVDF). Cryo-transmission electron microscopy reveals that the amorphous cPAN was uniformly coated on the FeF₂ surface with a thickness of 5 nm, acting as an effective (cathode electrolyte interphase) CEI layer that inhibited the growth of excessive CEI, thus achieved stable cycling in lean electrolyte. When paired with the high capacity SiO/C anode, the FeF₂-cPAN|SiO/C full cell delivered a capacity of 400 mAh/g after 100 cycles at 0.5C. Density functional theory (DFT) calculation indicates that the cPAN is inert to the electrolyte, thus suppresses the catastrophic electrolyte decomposition caused by FeF₂. DFT further suggests that the existence of vacancies on the carbon surface will cause H transfer reaction of the solvent, leading to the degradation of the electrolyte. This study provides a viable technology to enable high energy density FeF₂ cathode-based LIBs for energy storage applications.

铁基氟化物（IBF，通常为 FeF ₃和 FeF ₂）由于其高比容量、成本效益和地壳丰度而成为锂离子电池 (LIB) 的潜在下一代高能量密度阴极。然而，IBF 会剧烈分解电解质，这阻碍了它们在 LIB 中的实际应用。在此，我们报告了一种将 FeF ₂纳米粒子嵌入互连的环状聚丙烯腈 (cPAN) 网络中以钝化阴极/电解质界面的策略。此外，cPAN 对 FeF ₂纳米粒子和集电器，本质上充当优于聚偏二氟乙烯 (PVDF) 的粘合剂。冷冻透射电子显微镜显示，非晶cPAN均匀地涂覆在FeF ₂表面，厚度为5 nm，作为有效的（阴极电解质界面）CEI层抑制了过量CEI的生长，从而实现了贫油中的稳定循环电解质。当与高容量 SiO/C 阳极配对时，FeF ₂ -cPAN | SiO/C 全电池在 0.5C 下循环 100 次后可提供 400 mAh/g 的容量。密度泛函理论 (DFT) 计算表明 cPAN 对电解质呈惰性，从而抑制了由 FeF _{2引起的灾难性电解质分解}. DFT进一步表明，碳表面空位的存在会引起溶剂的H转移反应，导致电解质的降解。该研究提供了一种可行的技术，可实现用于储能应用的高能量密度 FeF _{2阴极基锂离子电池。}