A catalytically polymerized solid electrolyte enables 450 Wh kg−1 lithium–metal batteries with thermal–mechanical abuse tolerance

Practical implementation of solid polymer electrolytes is constrained by interfacial instability and manufacturing scalability. Here, we report a roll-to-roll compatible, 9.6-μm-thick solid polymer electrolyte membrane synthesized via in situ 1,3-dioxolane polymerization catalyzed by Lewis-acidic Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 on a polyethylene matrix, achieving a 99.1% conversion rate. The resulting membrane demonstrates 191.7 MPa mechanical strength and 418.7 mS ionic conductance at 25 °C. To resolve multiscale interfacial incompatibilities, a dual-additive strategy is employed: tris(4-fluorophenyl) phosphine constructs a fluorine-rich interphase extending positive electrode tolerance to 4.8 V, while Mg(TFSI) 2 forms a Li–Mg alloy lowering the negative electrode Li⁺ diffusion barrier to 0.127 eV. Validated in 1.2 Ah pouch cells, this system attains specific energy and energy density of 456.7 Wh kg⁻ 1 and 911.1 Wh L⁻ 1 (based on the total mass and volume of the pouch cell, respectively), stable wide-temperature cycling (−20 to 55 °C), and prevents thermal propagation under abuse conditions.