Thermopolymerized Flame-retardant Polymer Interphase toward Highly Stable Gel Electrolytes for Thermal Safety of Lithium Metal Battery

Abstract

Lithium metal batteries (LMBs) are widely regarded as one of the most attractive options for next-generation high-energy-density energy storage, but their practical application is still limited by lithium dendrite growth, continuous electrolyte decomposition, interfacial instability, and insufficient thermal safety. Herein, we report a multifunctional PVA/PAM-TFEP composite film constructed on lithium metal via an in situ thermal polymerization strategy. The interfacial layer consists of a threedimensional polymer network formed by polyvinyl alcohol (PVA) and acrylamide (AM), with tris(2,2,2-trifluoroethyl) phosphate (TFEP) incorporated as a flameretardant component. Theoretical calculations and interfacial characterizations demonstrate that the composite layer can homogenize Li + flux, regulate lithium deposition, and suppress electrolyte decomposition, thereby promoting the stabilization of the electrode/electrolyte interface. Consequently, the PVA/PAM-TFEP@Li electrode exhibits improved cycling stability in symmetric cells, LFP full cells, and pouch cells. Meanwhile, the incorporation of TFEP enhances the thermal stability and flame-retardant performance of the interface. This work provides an effective strategy for designing multifunctional protective layers for lithium metal anodes toward safe and stable lithium metal batteries.