Regulating carrier transport and oxychloride interphase formation by increasing configurational complexity in solid-state halide electrolytes

Abstract

Lithium metal-halide solid electrolytes are promising alternatives to lithium thiophosphates owing to their low toxicity and improved positive-electrode compatibility, while interfacial instability during cycling and the high cost of metal-salt precursors remain key commercialization challenges. Herein, we demonstrate that increasing the configurational complexity of low-cost Li2ZrCl6 with a minimal fraction of metal dopants induces significant lattice distortions that promote Li-ion transport. Our strategy furthermore substantially reduces electronic conductivity and promotes formation of an in situ (Liz)ZrOxCly-rich protective nanolayer at the cathode interface during cycling, which is absent in pristine Li2ZrCl6 cells. All-solid-state batteries using the optimized electrolyte coupled with polycrystalline LiNi0.85Co0.1Mn0.05O2 delivered high areal capacity (up to 23.2 mAh cm−2) and excellent long-term 4.4 V cycling stability, unlike the fast capacity decay in Li2ZrCl6 cells. These results show that electronic conductivity and interfacial behavior critically govern cycling performance and suggest general applicability to cathodes susceptible to oxygen release at high potentials.