Nano high-entropy alloy with strong affinity driving fast polysulfide conversion towards stable lithium sulfur batteries

Abstract

High-entropy alloys (HEAs), as a special heterostructure, possesses many exclusive advantages, including the inherited merits from each component and the synergistic regulation of electronic properties, which has a great potential for catalyzing complicated redox conversions. Herein, we reveal that the synthesized nano-HEA plays a unique role in the multi-electron and multiphase conversions of lithium polysulfides (LiPSs) in lithium-sulfur batteries (Li-S). Owing to the strong affinity with LiPSs, nano-HEA enriches the activity of LiPSs around the electrode more than 17 times higher than that of the control sample (without nano-HEA addition), significantly reducing the concentration polarization. In addition, the activation polarization was greatly suppressed by the nano-HEA catalyst, which is demonstrated by the lower Tafel slope, higher exchange current density, and the larger current response from the scanning electrochemical microscopy (SECM). Besides, the smooth and continuous redistribution of surface charge is further revealed by DFT calculation, benefiting the multi-electron reactions of LiPSs. As a result, Li-S batteries assembled with nano-HEA modified separators delivered outstanding capacity retention rates of 83.3% (2 C after 500 cycles in coin cell) and 82% (0.1 C 150 cycles in pouch cell), respectively.