Hollow Co<sub>3</sub>S<sub>4</sub> Nanocubes Interconnected with Carbon Nanotubes as Nanoreactors to Accelerate Polysulfide Conversion for High-Performance Lithium–Sulfur Batteries
Junhao Li, Fangyuan Li, Jiajie Pan, Junda Pan, Jinyun Liao, Hao Li, Huafeng Dong, Kaixiang Shi, Quanbing Liu
Abstract
Lithium–sulfur batteries (LSBs) with a high energy density of 2600 Wh kg –1 have drawn intensive attention based on the double electron reaction of sulfur. Nevertheless, blocked by the shuttle effect of lithium polysulfides and sluggish sulfur conversion kinetics, LSBs display a small specific capacity and a rapid capacity loss. Herein, we describe a conductive framework and electrocatalyst where numerous carbon nanotubes run through the hollow Co 3 S 4 nanocubes as the sulfur host. The hollow structure can buffer the volume change during the discharge/charge process, while the CNTs link cubes together to facilitate electron transport. The Co 3 S 4 catalyst can not only effectively accelerate the conversion from liquid LiPSs into solid Li 2 S 1/2 but also promote the conversion of Li 2 S 2 into Li 2 S. Based on the DFT theoretical calculation, the Li–S bond of Li 2 S 2 became longer after interaction with Co 3 S 4, indicating that it is easier to break into Li 2 S. Thus, the Co 3 S 4 /CNTs composite cathode shows a higher initial specific capacity (1252 mAh g –1 ) than the CNT cathode (928 mAh g –1 ) at 0.1C. In addition, it also shows a specific capacity of 440 mAh g –1 after 800 cycles with a decay rate of 0.08% per cycle at 1.0C. This work provides a new perspective for improving the sluggish transformation kinetics, which is conducive to the enhancement of sulfur utilization.