Built‐in Electric Field Within CoSe <sub>2</sub> ‐FeSe <sub>2</sub> Heterostructure for Enhanced Sulfur Reduction Reaction in Li‐S Batteries
Ruijian Luo, Junzhe Zhao, Ming Zheng, Zichen Wang, Shunqiang Zhang, Jiancan Zhang, Yong Xiao, YingHui Jiang, Zhixiong Cai, Niancai Cheng
Abstract
Abstract The conversion of Li 2 S 4 to Li 2 S is the most important and slowest rate‐limiting step in the complex sulfur reduction reaction (SRR) for Li‐S batteries, the adjustment of which can effectively inhibit the notorious “shuttle effect”. Herein, a CoSe 2 ‐FeSe 2 heterostructure embedded in 3D N‐doped nanocage as a modified layer on commercial separator is designed (CoSe 2 ‐FeSe 2 @NC//PP). The CoSe 2 ‐FeSe 2 heterostructure forms a built‐in electric field at the two‐phase interface, which leads to the optimized adsorption force on polysulfides and the accelerated reaction kinetics for Li 2 S 4 ‐Li 2 S evolution. Density functional theory (DFT) calculations and experimental results combine to show that the liquid‐solid reaction (Li 2 S 4 ‐Li 2 S 2 /Li 2 S) is significantly enhanced in terms of thermodynamics and electrodynamics. Consequently, the batteries assembled with CoSe 2 ‐FeSe 2 @NC//PP delivered an excellent rate capability (606 mAh g −1 under 8.0 C) and a long cycling lifespan (only 0.056% at 1.0 C after 1000 cycles). In addition, the cells can provide high initial capacity of 887 mAh g −1 at sulfur loading of 5.8 mg cm −2 and 0.1 C. This work would provide valuable insights into binary metal selenide heterostructures for liquid‐solid conversion in Li‐S batteries.