Sulfur/polyacrylonitrile/carbon multi-composites as cathode materials for lithium/sulfur battery in the concentrated electrolyte

Abstract

Sulfur/polyacrylonitrile(PAN)/carbon multi-composites with different sulfur content are prepared based on dual-mode of fixing sulfur on the matrix of the partially carbonized PAN (cPAN) and activated-conductive carbon black (A-CCB). The electrochemical performance of the as-prepared multi-composites as active materials are tested in the electrolyte with a high concentration lithium salt (LiTFSI) in different mixed solvents of 1,3-dioxolane (DOL)/1,2-dimethoxyethane (DME), and 1,3-dioxolane (DOL)/tetraethylene glycol dimethyl ether (TEGDME), respectively. It is demonstrated that the high concentration lithium salt (LiTFSI) and high viscous solvent have a great impact on the cycle stability of the multi-composite by suppressing polysulfide dissolution at the slight expense of the discharge potential plateaus (width and height). The as-prepared multi-composites present the excellent cycle performance in the electrolyte with 5 M LiTFSI in DOL/DME. Meanwhile, when the lower viscous DME solvent is replaced by the higher viscous TEGDME solvent in the electrolyte with 3 M LiTFSI, the optimized cycle stability is still obtained for the as-prepared multi-composites based on the evaluation of the discharge capacity and cycle stability. Therefore, the electrochemical performance of the as-prepared multi-composites is obviously influenced by the common ion effect and viscosity of the electrolyte, which are induced from both the lithium salt and solvent.