A Lithiophilic Donor-Acceptor Polymer Modified Separator for High-Performance Lithium Metal Batteries

As traditional lithium-ion batteries near their theoretical limits, the advancement of lithium-metal batteries (LMBs) becomes crucial for achieving higher energy densities. However, uncontrolled ion transport and unstable solid electrolyte interface (SEI) layer are key factors inducing lithium dendrite growth, hindering the development of LMBs. Separator modification is an effective strategy to address the challenges of LMBs. To tackle the issues, a donor-acceptor polymer (ArMT) consisting of benzene rings and triazine was successfully synthesized and modified onto commercial polypropylene (ArMT@PP) as separators for LMBs. Benefitting from the highly lithiophilic triazine organic units, this ArMT exhibits affinity towards Li⁺ and simplifies the solvation structure of Li⁺ during the diffusion process, thus decreasing the ion diffusion activation energy, thereby accelerating the migration of Li⁺. Furthermore, triazine organic units with appropriate pore size regulate the plating/stripping behavior of lithium metal anodes, thereby facilitating the formation of a stable solid electrolyte interface (SEI) layer. As a result, the assembled Li|ArMT@PP|Li symmetric cells exhibit stable plating/stripping over 800 h. Moreover, the LiFePO₄|ArMT@PP|Li cells achieved excellent cycling stability with 127.3 mAh g^-1 after 1200 cycles at 1 C and a high capacity retention of 90.58 %. This design strategy ensures a durable and dendrite-free anode and paves the way for the development of high-energy-density LMBs.