Abstract
Lithium halide solid electrolytes have garnered significant attention owing to their high ionic conductivity and positive electrode compatibility. However, achieving target ionic conductivity typically requires high lithium concentration (>4.3 wt%) within optimal structure, which raises costs and exacerbates air sensitivity. Here, we leverage anion clusters to synthesize a series of amorphous halide electrolytes xLi(2)SO(4)-ZrCl(4), with optimal ionic conductivities of 1.5 mS cm(-1) at 30 °C and a significantly reduced lithium content of 2.4 wt%, alongside good air stability. Through neutron/synchrotron X-ray experiments, first-principles calculations and machine learning-accelerated molecular dynamics simulations, we reveal a disordered backbone of [Zr(a)Cl(4a)(SO(4))](2-) (1 ≤ a ≤ 4) that enables fast Li-ion diffusion via under-coordinated oxygen sites. All-solid-state lithium batteries employing these electrolytes and LiNi(0.8)Co(0.1)Mn(0.1)O(2) positive electrode exhibit 81.1% capacity retention after 1400 cycles at 1 C (60 min) and 30 °C. Our findings reveal anion-cluster chemistry as an approach that transforms solid electrolyte design for advanced batteries, bridging materials science with practical energy storage innovation.