Enhancing Cycling Stability and Suppressing Lithium Dendrite Formation With A Hierarchical Artificial Solid Electrolyte Interphase Layer on Lithium Anodes for High‐Voltage Lithium Metal Batteries

Lithium metal anodes are promising for next-generation high-energy batteries owing to a high theoretical capacity and low redox potential. However, their use is limited due to uncontrolled dendrite growth, unstable solid electrolyte interphase (SEI), and poor cycling stability. This article reports a new thin layer composed of organic and inorganic materials, specifically combining hexafluorocyclotriphosphazene (HFPN) and Al₂O₃ nanoparticles along with a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) copolymer binder. This layer is applied to Li metal anodes using a spin coating method to create a HFPN@Al₂O₃ artificial SEI (ASEI) layer (HAPH@Li). HAPH@Li benefits from the strength of Al₂O₃ and ionic conductivity of PVDF-HFP. The HFPN additive, rich in F, N, and P, assisted in the formation of a stable SEI to effectively control the flow of Li ions and reduce Li dendrite formation. Moreover, full cells assembled using HAPH@Li anodes paired with Ni-rich NCMA90 cathodes operated at 2.8-4.3 V. The NCMA/HAPH_0.5:1@Li full cell outperformed other full cells with bare and other ASEI-modified Li anodes. The full cell achieved a high Coulombic efficiency of > 99.62%, initial discharge capacity of 181.9 mAh g^-1, and capacity retention exceeding 75.7% over 300 cycles at 1C/1C.