Dynamic interface regulation in solid-state lithium-metal batteries by in situ polymerized highly elastic ultrathin layers

Poly(vinylidene fluoride) (PVDF)-based solid-stated electrolytes (SSEs) hold great promise for high-energy-density solid-state lithium metal batteries (SSLMBs) due to their relatively high ionic conductivity and excellent flexibility. However, their practical performance is hindered by instability at the Li/PVDF interface, where the porous PVDF induces uneven ion deposition and residual N,N-dimethylformamide (DMF) solvent triggers severe side reactions with Li. Here, we demonstrate that a highly elastic layer, introduced via in situ polymerization of 1,3-dioxolane (P-DOL) containing thermoplastic polyurethane (TPU), effectively stabilizes and dynamically regulates the Li/PVDF interface. The incorporation of TPU enhances the elastic modulus of the cured layer, enabling local stress redistribution and dynamic retention of intimate interfacial contact at the Li/PVDF interface during cycling, which in turn promotes dense and flat Li deposition morphology to prolong the cycle life. Moreover, the interlayer prevents side reactions between DMF residues and Li anode, preserving an electrochemically stable contact. Consequently, the Li|PVDF|LiNi_0.8Co_0.1Mn_0.1O₂ cell with TPU/P-DOL interlayer delivers a capacity of 136 mA h g⁻¹ over 800 cycles at 1 C. Our findings demonstrate a scalable interfacial engineering strategy that addresses the key bottleneck of PVDF-based SSEs and significantly advances the performance of SSLMBs.