A green and facile strategy for the low-temperature and rapid synthesis of Li2S@PC–CNT cathodes with high Li2S content for advanced Li–S batteries

Abstract

Lithium sulfide (Li₂S) is considered as a promising lithium storage material because of its high theoretical specific capacity of 1166 mA h g⁻¹. The electrochemical performance of Li₂S can be remarkably improved by introducing carbon to form Li₂S–carbon composites. However, the complex preparation process of Li₂S–carbon composites limits their large-scale applications. Herein, we present a green and facile strategy to synthesize porous carbon-coated Li₂S–carbon nanotube composites (Li₂S@PC–CNT) by heating carbon disulfide (CS₂) and the lithium hydride–CNT mixture at a temperature below 250 °C, which is the lowest temperature for in situ synthesis of Li₂S–carbon composites reported till date. For the Li₂S@PC–CNT composites, Li₂S@PC particles are connected with neighboring particles through the 3D CNTs network skeleton. This unique nanoarchitecture not only prevents the loss of active materials and diffusion of polysulfides, but also significantly facilitates fast electron and ion transport. As a result, a high specific capacity (820 mA h g⁻¹ at 0.1 A g⁻¹ after 10 cycles) and a remarkable cycle life (502 mA h g⁻¹ at 0.5 A g⁻¹ after 300 cycles) are achieved. The rationally designed structure and superior electrochemical performance of the Li₂S@PC–CNT composites will pave a new avenue for realizing high energy density of Li–S batteries.