Rare-Earth-Free Chloride Solid Electrolytes with High Ionic Conductivity for All-Solid-State Lithium Batteries

The commercialization of all-solid-state lithium batteries (ASSLBs) depends on solid electrolytes (SEs) that simultaneously offer high ionic conductivity (>1 mS cm –1 ) and low cost (<$20 kg –1 ). However, existing SEs face performance-cost trade-off: highly conductive materials rely on expensive precursors, whereas low-cost alternatives fail to meet conductivity benchmarks. Herein, we report a rare-earth-free chloride SE, Li 2.03 Zr 0.98 P 0.02 Cl 5.95 S 0.05 (LZC-1PS), which combines ultralow cost ($15.21 kg –1 ) with a room-temperature ionic conductivity of 1.02 mS cm –1 . The fast ionic migration behavior arises from a reduced diffusion barrier (particularly along the a-b lattice plane), achieved via a dual-site substitution strategy where Cl – is partially replaced by more polarizable S 2– to ease electrostatic constraints, and Zr 4+ is substituted with more electronegative P 5+ to weaken Li + -anion interactions through inductive effects. As proof of concept, the LZC-1PS is tested in combination with a Li 6 PS 5 Cl-coated Li–In anode and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) or LiCoO 2 (LCO) cathode in lab-scale cell configuration. Those ASSLBs show outstanding cycling stability, retaining 75.2% capacity after 1200 cycles for LCO cathodes and 76.6% after 1000 cycles for NCM811 cathodes at 1C.