In-Situ-Polymerized Interface Modulation Drives Spark-Plasma-Sintered Garnet Electrolyte-Based Solid-State Lithium Metal Batteries

Abstract

Garnet-type solid electrolytes offer high ionic conductivity to be employed in solid-state lithium metal batteries. However, sluggish lithium-ion kinetics at the electrolyte–electrode interface hinder their application in full cells. Herein, we report the fabrication of a dense cubic-phase Li6.5La3Zr1.5Nb0.5O12 (LLZNO) garnet solid electrolyte using the spark plasma sintering technique, with a conductivity of ∼2.82 × 10–4 S cm–1 at room temperature. A free-radical-initiated in-situ polymerization strategy using poly(ethylene glycol) dimethacrylate and tetraethylene glycol dimethyl ether was employed to establish intimate electrode–electrolyte interfacial contact. Consequently, the resulting polymer interlayer facilitates uniform lithium plating/stripping in lithium symmetric cells and provides lithium-ion conduit channels at the electrolyte–cathode interface in full cells. LiFePO4 full cells delivered a high specific capacity (100 mAh g–1) and exceptional cycling stability (90% capacity retention after 500 cycles) at 1 C (30 °C). © 2026 American Chemical Society