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

Abstract

Transition metal diselenides (TMSe 2 ) 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 2 severely hinders the realization of their full potential for boosting LSB’s performance. Herein, we report the synthesis of high-entropy NiCoMnCrVSe 2 nanoflakes anchored on graphene supports (NiCoMnCrVSe 2 /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 2 through comprehensive experimental studies and theoretical calculations. Our results show that as the number of transition metals in TMSe 2 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 Li 2 S. Consequently, LSBs containing NiCoMnCrVSe 2 /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 NiCoMnCrVSe 2 /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.

Topics & Concepts