Nitrogen‐Doped Hollow Carbon Polyhedrons with Carbon Nanotubes Surface Layers as Effective Sulfur Hosts for High‐Rate, Long‐Lifespan Lithium–Sulfur Batteries
Bin Fan, Dengke Zhao, Wei Zhou, Wei Xu, Xinghua Liang, Guoqiang He, Zexing Wu, Ligui Li
Abstract
Abstract Effectively confining lithium polysulfides inside porous material matrix with a high electrical conductivity represents a judicious way to extend lifespan and enhance rate performance of lithium‐sulfur (Li‐S) batteries. Herein, nitrogen‐doped hollow carbon polyhedrons with a thin CNTs conductive surface layer (CNTs/HNC) were prepared by directly pyrolyzing the CNTs coated ZIF‐8 polyhedrons crystallite precursors, and subsequently served as sulfur hosts in Li‐S batteries. The resulted product CNTs/HNC‐800 comprises a nitrogen content of 4.94 at.% as well as a high electrical conductivity of 8.43×10 −1 S cm −1 , which help to effectively adsorb/confine lithium polysulfides and substantially improve the rate capacity of Li‐S batteries. With a sulfur loading of 1.60 mg cm −2 , the S@CNTs/HNC based cathode shows a discharge capacity of 870.7 mAh g −1 at 1.0 C, and can maintain 76.4 % of its initial capacity after 500 charge‐discharge cycles, corresponding to a capacity fade rate of only 0.047 % per cycle. While with a higher sulfur loading of 2.46 mg cm −2 , a discharge capacity of 649.7 mAh g −1 can be achieved at 0.5 C, along with a capacity fade rate of merely 0.044 % per cycle during 200 cycles. When sulfur loading is further increased to 5.39 mg cm −2 , it can also maintain a considerable initial discharge capacity of 812 mAh g −1 at 0.1 C. This work enriches the ways to prepare complicate nano structured sulfur hosts for long‐life and high‐rate Li‐S batteries.