Surface-modified PVdF-derived hierarchical mesoporous carbon matrix for high sulfur loading cathode in lithium-sulfur batteries

Abstract

Lithium-sulfur batteries have attracted considerable interest because of their high energy density, non-toxicity, and low-cost. However, the main challenges associated with the dissolution of lithium polysulfides and low conductivity of sulfur are still required to be overcome to achieve improved cycling life and power density. Herein, we design and synthesize a hierarchical mesoporous carbon (HMC) through one-step pyrolysis of a low-cost polyvinylidene fluoride (PVdF) precursor with a sodium hydroxide activating agent for an efficient encapsulating host for sulfur. By impregnating sulfur into carbon via a melt-diffusion process, the HMC/sulfur composite contains a high sulfur content (similar to 72 wt%) inside the mesopore-dominant host. Moreover, with a multifunctional polyvinylpyrrolidone coating, the obtained composite exhibits an enhanced electrochemical performance including high specific capacity (1124 mA h 8(-1) at 100 mA g(-1)) and good cycling life with a reversible capacity of 456 mA h g(-1) after 500 cycles at 800 mA g(-1). Both the hierarchical mesoporous nature of the carbon host and the protective coating not only suppresses the polysulfide dissolution but also provides improved interfacial stability and facile charge transport pathways. This strategic combination leads to high reversible capacity, enhanced cycling reversibility, and good rate capability of the high sulfur loading cathodes.