Spinel High-Entropy Oxide with High-Valence Mo for Ultra-sensitive H2S Detection and Safety Warning of All-solid-state Battery

All-solid-state batteries (ASSBs) have the advantages of wide temperature range and high energy density. However, Improper storage, transportation and use of ASSBs may produce cracks, leading the electrolytes exposed and reacting with moisture in air to generate toxic and harmful H2S, which seriously endangers the life and property safety of operators. Therefore, the design of an ultra-sensitive H2S gas sensor is expected to achieve safety warning of ASSBs. High-entropy oxides (HEOs) possess multiple cations and inherent oxygen vacancies making it's possible for performance customization. Spinel HEOs have the advantages of low cost, simple synthesis, stable structure, and have been partially developed for gas sensing, catalysis, heat-resistant and other fields. In addition, the introduction of high-valence metals can further adjust the electronic structure, activate lattice oxygen, and bring significant performance improvements. In this work, (CoCrMnMoZn)3O4 with highvalence Mo was synthesized and its morphology, structure and composition were analyzed. Through gas sensing tests, it proved to be an ideal candidate for H2S sensors due to its high sensitivity (1.03 to 10 ppb H2S), good selectivity, long-term and humidity stability. Simulation experiments show the applicability of the sensor for failure detection of ASSBs with multiple temperatures in the whole relative humidity range. Diffuse reflaxions infrared fourier transformations spectroscopy (DRIFTS) showed H2S was adsorbed at the Mo sites to form Mo-S bonds and decomposed into SO2 and H2O. The study provides a promising approach for the safety warning of ASSBs.