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

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.