Nitrogen-Doped Hollow Carbon Polyhedrons With Carbon Nanotubes Surface Layers As Effective Sulfur Hosts For High-Rate, Long-Lifespan Lithium-Sulfur Batteries

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 8.43x10(-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.