Designing a double-coated cathode with high entropy oxides by microwave-assisted hydrothermal synthesis for highly stable Li-S batteries

Nowadays, Li-S batteries are considered as one of the most promising alternatives to Li-ion technology in the near future, thanks to their high specific capacity and their significantly lower environmental impact and production costs. Consequently, many efforts have been directed to tackle with the inherent issues that affect Li-S batteries. One of the main problems is the so-called shuttle effect, which basically entails the unwanted migration of lithium polysulfides (LiPSs) from the cathode to the anode side, causing the degradation of the cell. Here, we report an effective strategy to restrain the shuttle effect and increase the kinetics at the cathode of the lithium-sulfur (Li-S) battery. A functional layer including high entropy oxides (HEO) coated onto the sulfur cathode allows to exploit the HEOs capability as promoter catalysts for the conversion of LiPSs. Pure HEO powders are synthesized by fast, highly efficient microwave irradiation, followed by heat treatment at 930 degrees C. The formation of highly crystalline HEO is confirmed by X-ray diffraction analysis. The LiPSs adsorption capability of HEO is evaluated by UV-vis and X-ray photoelectron spectroscopy analyses. The effect of the HEO-coated sulfur cathode on the electrochemical performance of the Li-S battery is studied by cyclic voltammetry and galvanostatic charge/discharge. The cell with double-coated cathode delivers an initial discharge capacity of 1173 mAh/g at C/10 with 45% capacity retention over 500 cycles at C/5, approaching similar to 99% coulombic efficiency.[GRAPHICS].