Confined Reconstruction of Thiospinels Toward Stable Li–CO 2 Batteries

ABSTRACT Oxidative reconstruction of thiospinel catalysts is well recognized as a common phenomenon in Li–CO 2 batteries, and the oxidation state of catalysts after reconstruction is known to be decisive for battery performance. However, the underlying mechanism of this correlation remains unclear, making it challenging to achieve a thiospinel catalysts that are active and invulnerable to restructuring in Li–CO 2 batteries. Here, the confined reconstruction of NiCo 2 S 4 during battery operation is achieved via a mild oxidation strategy and the mechanism for the improved durability is revealed. Operando X‐ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations reveal that the oxygen substitution creates a mixed O/S coordination environment for metal atoms (Co and Ni) in NiCo 2 S 4 and larger metal‐sulfur bond energy. The resulting strong metal‐sulfur interaction can stabilize the sulfur atoms and thereby enhance the structural durability against the oxidative reconstruction. Thus, the mild oxidation affords NiCo 2 S 4 cathode possessing excellent catalytic activities (high discharge capacity of 6906.8 µA h cm −2 ) and activity retention for over 2000 h. The mild oxidation principles proposed here provide a generalizable strategy for the design of stable electrocatalyst materials.