Improving the electrochemical performance of lithium-sulfur batteries via separator coating

Abstract

High energy density batteries have become a hot topic due to the increasing requirements of green energy vehicles, portable devices and rechargeable equipment. Lithium sulfur batteries (LSB) is one of the excellent candidate due to that it has a high theoretical gravimetric energy density and is based on a low cost and environmentally-friendly active material sulfur. However, the commercialization of LSB is blocked by the its fast capacity decay rate and the low cycle stability. This low performance is mainly caused by the shuttle effect of lithium polysulfides (LPS). This report aims to develop a new type multi-walled carbon nanotube (MWCNTs)- supported Nafion coated separator via the experimental investigating on current carbon-based and polymer-based separator coatings to further improve the electrochemical performance of LSBs. In this MWCNTs & Nafion composites, the MWCNT provides a two-dimensional framework for the Nafion to further improve the mechanical strength of Nafion coating, and suppress the interaction between Nafion and electrolytes. The nanometre size Nafion can intergrade into the porous structure of MWCNTs, which improves the trap ability of MWCNTs on migrating LPS. The batteries with MWCNT & Nafion-coated separator reach a high initial discharge capacity of 927 mAh/g at 0.2C, and still have a capacity of 816.8 mAh/g after 56 cycles with an average columbic efficiency higher than 80%.