Regulating Electronic Structure and Coordination Environment of Transition Metal Selenides through the High-Entropy Strategy for Expedited Lithium-Sulfur Chemistry.

Transition metal diselenides (TMSe) have proven as promising catalysts able to promote the conversion kinetics of lithium polysulfides (LiPSs) in lithium-sulfur batteries (LSBs). However, the limited number of catalytically active edge sites in TMSe severely hinders the realization of their full potential for boosting LSB's performance. Herein, we report the synthesis of high-entropy NiCoMnCrVSe nanoflakes anchored on graphene supports (NiCoMnCrVSe/G) through a microwave-assisted solvothermal method. We systematically investigate how the high-entropy strategy enables the regulation of the electronic structure and coordination of various metal species in TMSe through comprehensive experimental studies and theoretical calculations. Our results show that as the number of transition metals in TMSe increases, the d-band center of metal active sites upshifts toward the Fermi level and the difference among d-band centers of various metal species diminishes, which facilitates the adsorption of LiPSs and lowers the energy barriers to nucleation/decomposition of LiS. Consequently, LSBs containing NiCoMnCrVSe/G as sulfur hosts deliver a high specific discharge capacity of 1453 mAh g at 0.1 C and excellent stability at 1 C for 500 cycles with a low decay rate of merely 0.016% per cycle. More importantly, we fabricate a ∼2.18 Ah multilayer pouch cell that can deliver an energy density of 435 Wh kg (based on the whole pouch cell weight), demonstrating the great potential of NiCoMnCrVSe/G for practical applications. This work provides important guidelines for the rational design of efficient high-entropy catalysts for bidirectional LiPSs conversion and other reactions beyond.