Wide-Temperature-Range Li-S Batteries Enabled by Thiodimolybdate [Mo2S12]2- as a Dual-Function Molecular Catalyst for Polysulfide Redox and Lithium Intercalation.

ABSTRACT

In lithium-sulfur batteries, a serious obstacle is the dissolution and diffusion of long-chain polysulfides, resulting in rapid capacity decay and low Coulombic efficiency. At present, a common practice is designing cathode materials to solve this problem, but this gives rise to reduced gravimetric and volumetric energy densities. Herein, we present a thiodimolybdate [Mo2S12]2- cluster as sulfur host material that can effectively confine the shuttling of polysulfides and contribute its own capacity in Li-S cells. Moreover, the [Mo2S12]2- cluster as a "bidirectional catalyst" can effectively catalyze polysulfide reduction and lithium sulfide oxidation. We further investigate the catalytic mechanism of [Mo2S12]2- clusters by theoretical calculations, in situ spectroscopic techniques, and electrochemical studies. The (NH4)2Mo2S12/S cathodes show good electrochemical performance under a wide range of temperatures. In addition, a pouch cell fabricated with (NH4)2Mo2S12/S cathodes maintains a stable output for more than 50 cycles.