High “C” rate Li-S cathodes: sulfur imbibed bimodal porous carbons

Abstract

A highly ordered mesoporous carbon with a bimodal pore structure which exhibits a high specific area and large pore volume, was synthesized by a triblock-copolymer-templating approach. This optimized framework served as the scaffold for the preparation of carbon/sulfur (C/S) nanocomposites that serve as novel cathodes for Li-S batteries. They exhibit high discharge capacities and good cycling stability at very high current rates of 1675 mA g⁻¹ (1 C), which can be attributed to the unique bimodal porous structure of the carbon. The small mesopores contain the majority of the sulfur mass and aid in suppressing the diffusion of polysulfide species into the electrolyte, whilst the large interconnected cylindrical pores favour rapid transport of solvated Li⁺ on charge/discharge. Additional doping with hydrophilic nanoporous silica also aids in capacity retention on cycling.