Elevated Lithium Ion Regulation by a “Natural Silk” Modified Separator for High-Performance Lithium Metal Anode

Metallic lithium anode has long stood as the “holy grail” in the field of secondary batteries for its high theoretical specific capacity and low electrochemical potential. But its edge is blunted by the inherent uncontrolled lithium dendrite growth that can curtail the cycle life and raise safety concerns. In this work, a functional modification layer from a derivant of natural silk is developed to protect lithium anode via a facile automatic transfer route. Via offering abundant functional group sites, the Li-ion flux on the anode surface is made uniform efficiently. The silk fibroin-based modification layer also contributes to the in situ formation of a Li₃N-rich solid electrolyte interphase film on the lithium anode. Consequently, a high-performance lithium metal anode with dendrite-free morphology and significantly enhanced cycle stability is achieved: when paired with LiFePO₄ cathodes, the full cell achieves a long-term cycling stability of 3000 cycles at 5 C; when paired with sulfur cathodes (5 mg_sulfur cm⁻²), a long lifespan for over 400 cycles at 1 C is achieved. This work offers a facile and practical approach for the interface modification of the high-performance lithium anode and as well as provides a new perspective for the application of biomass-based materials in advanced batteries.