Origin of Phase Engineering CoTe 2 Alloy Toward Kinetics-Reinforced and Dendrite-Free Lithium-Sulfur Batteries.

Slow electrochemistry kinetics and dendrite growth are major obstacles for lithium-sulfur (Li-S) batteries. The investigations over the polymorph effect requires more endeavors to further access the related catalyst design principles. Herein, we report the systematic evaluation of CoTe 2 alloy with two polymorphs regarding sulfur reduction reaction (SRR) and lithium plating/stripping. As disclosed by theoretical calculations and electrochemical measurements, the orthorhombic (o-) and hexagonal (h-) CoTe 2 make a substantial difference. We explore the reactivity origin of the CoTe 2 polymorphs. The higher position of d-band centers for the Co atoms on the o-CoTe 2 leads to a higher displacement of the antibonding state, the lower antibonding state occupancy, the more effective interaction with the sulfide moieties and lithium. Hence, o-CoTe 2 annihilates h-CoTe 2 and exhibits better catalysis and more uniform lithium deposition, consolidated by excellent performance of full cell made of o-CoTe 2 . It keeps stable charging/discharging for 800 cycles at 0.5 C with only 0.055% capacity decay per cycle and even achieves an areal capacity of 6.5 mAh cm -2 at lean electrolyte and high sulfur loading of 6.4 mg cm -2 . This work establishes the mechanistic perspective about the catalysts in Li-S batteries and provides new insight into the unified solution. This article is protected by copyright. All rights reserved.