Dynamic Interfacial Protection via Molecularly Tailored Copolymer for Durable Artificial Solid Electrolyte Interphase in Lithium Metal Batteries

Abstract The serious dendrite formation and safety hazards associated with side reactions hinder the practical application of lithium metal batteries. A molecular customization strategy based on both physical and chemical properties is reported. A copolymer of acrylamide and hexafluorobutyl acrylate molecules is used as an artificial solid electrolyte interface(ASEI) for lithium metal to achieve dynamic interface protection during cycling. The amide group serves as the rigid unit, while the hexafluorobutyl group serves as the flexible unit, and imparts excellent mechanical properties to the copolymer. Synergistically abundant C─F bonds exhibit excellent water and oxygen resistance and have good electrolyte affinity. The ester and amide groups serve as amphiphilic sites for Li⁺ and PF₆⁻, regulating the ion flux at the interface and achieving dendrite‐free lithium deposition. During cycling, the organic–inorganic composite SEI dynamically evolves to safeguard the lithium metal, preventing undue electrolyte consumption. The copolymer achieves stable cycling for 1500 and 950 h at 1 and 2 mA cm⁻², respectively. It demonstrates excellent performance with LiNi_0.8Co_0.1Mn_0.1O₂ and LiFePO₄ cathodes. This study introduces a new approach to designing polymers at the molecular level to optimize the physical properties/chemical activity of lithium metal interfaces.