Ionic Liquid Electrolyte for Enhancing Electrochemical Performance of Antimony Sulfide/Graphene Nanosheets Composite Anode in Sodium-Ion Batteries

Abstract

High-capacity carbon-coated Sb2S3/graphene composite anode for sodium rechargeable batteries is synthesized using a facile solvothermal method. An effective additive, 5 vol% fluoroethylene carbonate (FEC), is incorporated into the conventional organic electrolyte to improve the electrochemical performance of the Sb2S3/graphene composite anode due to the formation of more stable solid/electrolyte interface. In 1 M NaClO4 propylene carbonate/fluoroethylene carbonate (PC/FEC, v/v =95:5), maximum capacity of 621 mAh/g and cyclic stability of 43% after 50 cycles are obtained. In contrast, the cells with 1 M NaFSI in N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (PMP–FSI) ionic liquid shows the comparable capacity of 588 mAh/g and the best cyclic stability of 55% among the studied electrolytes at room temperature. With the increase in cell temperature from 25 to 60 °C, both the maximum capacity and cyclic stability of the cell with PMP–FSI improve significantly because of its high thermal stability (without decomposition below 400 °C) and the reduction of electrolyte and charge transfer resistance. The cell with IL electrolyte delivers the maximum capacity of 734 mAh/g and the cyclic stability of 62%, remarkably higher than those with conventional organic electrolytes at 25 °C and 60 °C. The promising ionic liquid electrolyte for the Sb2S3 anode of sodium rechargeable batteries is thus proposed.