Triple functionalization of carved N-doped carbon nanoboxes with synergistic trimetallic sulphide for high performance lithium–sulphur batteries

Abstract

Lithium–sulphur batteries (LSBs) have been drawing rapidly increasing research attention because of the low cost and high theoretical capacity of sulphur. The applications of LSBs however are hampered by poor stability caused by the shuttle effects of lithium polysulphides (LiPS), poor conductivities of sulphur, and sluggish redox kinetics of LiPS. Here, an advantageous carved N-doped carbon nanobox structure triply functionalized with an FeCoNi trimetallic sulphide was developed as a high performance sulphur host for LSBs. The strong chemical interactions toward LiPS, half-metallic conductivities, and catalytic activities toward redox reactions of LiPS, enabled through functionalization with FeCoNi trimetallic sulphide, work together to resolve the critical issues of LSBs. Moreover, the carved N-doped carbon nanobox structure serves as a nanoreactor that helps retain LiPS at cathodes and offers a confined space for fast local redox reactions. The triply functionalized carved N-doped carbon nanoboxes (S-FeCoNi@C-CNB) lead to high performance LSBs, delivering a high capacity of 1238 mA h g⁻¹ at 0.1C and maintaining a decent capacity of 655 mA h g⁻¹ at 2C. The LSB exhibits excellent stability with a low capacity decay rate of 0.049% per cycle over 200 cycle operations at 1C, indicating the success of S-FeCoNi@C-CNB in suppressing the shuttle effect.