Li2S In Situ Grown on Three-Dimensional Porous Carbon Architecture with Electron/Ion Channels and Dual Active Sites as Cathodes of Li-S Batteries.

Abstract

Li2S-based Li-S batteries are taken as promising energy storage systems due to the high theoretical specific capacity/energy density and nature of a matching Li-metal-free anode. However, the cyclic stability of the Li2S-based Li-S battery is seriously prevented by the shuttle effect of lithium polysulfides (LiPSs). Meanwhile, due to the poor electrical conductivity of Li2S, the Li-S battery displays slow reaction kinetics. In this work, we design 3D-porous carbon (PC) architecture as a host for inhabiting the LiPS shuttle based on physical capture. Furthermore, this porous carbon architecture is modified by introducing two kinds of heteroatoms (N and S) to form dual active sites (named as NSPC) for chemically binding LiPSs and accelerating their conversion. The polyvinyl pyrrolidone-coated Li2SO4·H2O is embedded in the NSPC skeleton and further forms the Li2S/NSPC cathode via a carbothermal reduction process. In consequence, the NSPC architecture possesses continuous electron/ion channels and abundant active sites, which are beneficial to the fast diffusion of Li+ and timely conversion of sulfur species. As a result, the as-prepared Li2S/NSPC cathode exhibits a high initial discharge capacity of 690 mAh g-1 at a high rate of 1C and keeps a capacity of 587 mAh g-1 after 200 cycles with a good capacity retention rate of 85% and low fading rate of 0.075% per cycle. Therefore, this work offers a brand-new platform to understand the synergistic effects of promoting reaction kinetics for Li2S-based Li-S batteries.