Phosphorous‐Based Heterostructure for the Effective Catalysis of Polysulfide Reactions with Phase Changes in High‐Sulfur‐Loading Lithium–Sulfur Batteries
Yun Zhao, Huanyu Zhang, Hualin Ye, Dan Zhao, Jim Yang Lee, Limin Huang
Abstract
Abstract High sulfur loading and long cycle life are the design targets of commercializable lithium–sulfur (Li–S) batteries. The sulfur electrochemical reactions from Li 2 S 4 to Li 2 S, which account for 75% of the battery's theoretical capacity, involve liquid‐to‐solid and solid‐to‐solid phase changes in all Li–S battery electrolytes in use today. These are kinetically hindered processes that are exacerbated by a high sulfur loading. In this study, it is observed that an in situ grown bimetallic phosphide/black phosphorus (NiCoP/BP) heterostructure can effectively catalyze the Li 2 S 4 to Li 2 S reactions to increase the sulfur utilization at high sulfur loadings. The NiCoP/BP heterostructure is a good polysulfide adsorber, and the electric field prevailing at the Mott−Schottky junction of the heterostructure can facilitate charge transfer in the Li 2 S 4 to Li 2 S 2 liquid‐to‐solid reaction and Li + diffusion in the Li 2 S 2 to Li 2 S solid‐state reaction. Consequently, a sulfur cathode with the NiCoP/BP catalyst can deliver a specific capacity of 830 mAh g −1 at the sulfur loading of 6 mg cm −2 for 500 cycles at the 0.5 C rate. High sulfur utilization is also possible at a higher sulfur loading of 8 mg cm −2 for 440 cycles at the 1 C rate.