Improved Rate Performance of Lithium Sulfur Batteries by In-Situ Anchoring of Lithium Iodide in Carbon/Sulfur Cathode

Abstract

Lithium sulfur battery is one of the most cost-effective alternatives to meet the requirement of high energy density for power sources due to its high energy density and low cost. However, lithium sulfur battery still suffers from a rapid capacity fading and poor rate performance, which are mainly related to the shuttle effect of polysulfides during cycling and the insulating nature of sulfur as well as the reduced product of Li2S or Li2S2. Here, we proposed an iodine-incorporated carbon/sulfur electrode to improve the rate performance of Li-S batteries. The resultant composite electrode exhibits good high-rate charge-discharge capability with a high discharge capacity of 479 mAh/g at 3C after 100 cycles. The excellent rate capability is mainly correlated to the iodine-doped carbon host with improved electronic conductivity, formation of lithium iodide (LiI) served as solid-state electrolyte in electrode during the first discharge process and the dissolution of iodine species into the electrolyte as additive for improving the ionic conductivity. This work offers an innovative, effective and facile method to ameliorate the electrochemical performance of lithium sulfur batteries.