All-solid-state lithium-ion batteries have great potential for higher energy and power density compared with conventional lithium-ion batteries. With extensive research efforts devoted to the development of inorganic super-ionic conductors, lithium thiophosphates stand out due to their high ionic conductivity and room-temperature processability. However battery rate performance still suffers from increased impedance attributed to the interfacial reactions between thiophosphate electrolytes and oxide electrodes. Stabilizing the interfaces with a protective coating layer has been proposed as a solution to the interfacial problem, but it is rare for a material to simultaneously exhibit fast ionic conduction and chemical stability at battery interfaces. Here, we propose a novel double-layer coating design which comprises a sulfide-based layer adjacent to the thiophosphate electrolyte accompanied by a layer that is stable against both the sulfide layer and the oxide cathode. Enabled by the development of ab initio databases and machine-learned interatomic potentials, we screened thousands of crystalline materials by their thermodynamic stability and ionic conductivity. Several sulfide + halide couples we identified potentially outperform the known coating materials in interfacial stability as well as ionic conductivity. We highlight the integration of several fast ionic conductors which may stabilize battery interfaces with minor loss of charge transfer rate through the thiophosphate electrolyte.

Stabilizing electrolyte-cathode interfaces via double-layer coating design in thiophosphate-based all-solid-state batteries

ACS Fall 2021

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