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

Abstract

Transition metal diselenides (TMSe₂) 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 TMSe₂ severely hinders the realization of their full potential for boosting LSB's performance. Herein, we report the synthesis of high-entropy NiCoMnCrVSe₂ nanoflakes anchored on graphene supports (NiCoMnCrVSe₂/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 TMSe₂ through comprehensive experimental studies and theoretical calculations. Our results show that as the number of transition metals in TMSe₂ 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 Li₂S. Consequently, LSBs containing NiCoMnCrVSe₂/G as sulfur hosts deliver a high specific discharge capacity of 1453 mAh g^-1 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^-1 (based on the whole pouch cell weight), demonstrating the great potential of NiCoMnCrVSe₂/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.