Engineering Ultrathin, Tough Polymer Networks for Stable Lithium Metal Anode Interphases

Abstract Interfacial degradation and dendritic lithium (Li) growth remain critical bottlenecks for practical Li metal batteries (LMBs). Herein, we introduce a tough, ion-conductive poly(2-(dimethylamino)ethyl methacrylate) (pDMAEMA) nanolayer on Li metal via photo-initiated chemical vapor deposition (piCVD). The photo-mediated, solvent-free piCVD enables nanometer-scale coatings with systematic control over photo-crosslinking and chain entanglement without compromising Li surface integrity. This systematic control yields an optimized polymer network balancing toughness (36.3 MJ m–3) and viscoelasticity (10.3% linear viscoelastic strain limit) to accommodate repeated Li volume changes. Furthermore, interactions between pDMAEMA and PF6– anions promote a mechanically durable LiF-rich solid electrolyte interphase, thereby supporting uniform Li deposition. Pouch-type bi-cells employing the optimized 100 nm polymer-coated Li anode achieve an energy density of 338 Wh kg–1 and 80% capacity retention after 90 cycles under practical conditions (N/P = 2, E/C = 3 g Ah–1). This ultrathin, tough polymer network offers a promising design principle for high-energy LMBs.