A catalytically polymerized solid electrolyte enables 450 Wh kg^-1 lithium-metal batteries with thermal-mechanical...

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_1.3Al_0.3Ti_1.7(PO₄)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.