Bimetallic Compound Catalysts with Multiple Active Centers for Accelerated Polysulfide Conversion in Li-S Batteries

Wuxing Hua, Nanoyang Group, State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China;
Jingyi Xia, Nanoyang Group, State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China;
Zhonghao Hu, Nanoyang Group, State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China;
Huan Li, Nanoyang Group, State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China;
Wei Lv, Shenzhen Key Laboratory for Graphene-based Materials and Engineering Laboratory for Functionalized Carbon Material, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen, 518055, China;
Quan-Hong Yang, Nanoyang Group, State Key Laboratory of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China;

Abstract

The practical applications of lithium-sulfur (Li-S) batteries are hindered mainly by the low sulfur utilization and severe capacity fading derived from the polysulfide shuttling. Catalysis is an effective remedy to this problem by promoting the conversion of polysulfides to reduce their accumulation in the electrolyte, which needs the catalyst to have efficient adsorption ability to soluble polysulfides and high activity for their conversion. In this work, we have proposed a bimetallic compound of NiCo2S4 anchored onto sulfur-doped graphene (NCS@SG) to fabricate a catalytic interlayer for Li-S batteries. Compared to the CoS, NiCo2S4 demonstrates much higher catalytic activity towards sulfur reduction reaction due to its multiple anchoring and catalytic active sites derived from the coordination of the bimetallic centers. As a result, NCS@SG interlayer dramatically improved the specific capacity, rate performance, and cycling stability of Li-S batteries. Especially, when the areal sulfur loading of the NCS@SG battery increases to 15.3 mg·cm-2, high-capacity retention of 93.9 % can be achieved over 50 cycles.