Enhanced chemical trapping and catalytic conversion of polysulfides by diatomite/MXene hybrid interlayer for stable Li-S batteries

Abstract

Lithium-Sulfur (Li-S) batteries with high theoretical energy density are promising energy storage systems in the next decades, while the lithium polysulfides (LiPSs) shuttling caused by the sluggish sulfur redox reaction severely lowers the practical performance. The use of interlayer between the cathode and separator has been widely investigated to physically or chemically block the LiPSs, while the introduction of catalytic materials is a more effective strategy to accelerate the conversion of LiPSs. MXene with rich surface chemistry has shown its potential for facilitating the catalytic conversion, however, the aggregation of MXene sheets usually leads to the loss of the catalytic active sites. Herein, we report a diatomite/MXene (DE/MX) hybrid material as the bifunctional interlayer for improving the adsorption/conversion of LiPSs in Li-S batteries. The diatomite with porous structure and rich silica-hydroxyl functional groups could trap LiPSs effectively, while prevent the aggregation of MXene. The DE/MX based interlayer showed bifunctions of enhancing the chemical adsorption and promoting the conversion of LiPSs. The Li-S batteries with the DE/MX interlayer delivered an improved cycling stability with a low capacity decay of 0.059% per cycle over 1000 cycles at 1.0 C. Moreover, stable 200 cycles can be realized with a high sulfur loading electrode up to 6.0 mg cm−2. This work provides an effective strategy to construct bifunctional interlayers for hindering the shuttling of LiPSs and boosting the practical application of Li-S batteries.