High Performance Room Temperature Sodium-Sulfur Battery by Eutectic Acceleration in Tellurium-Doped Sulfurized Polyacrylonitrile

Room temperature (RT) sodium-sulfur batteries suffer from slow reaction kinetics and polysulfide dissolution, resulting in poor performance. Sulfurized polyacrylonitrile is a unique sulfur cathode which is suggested to involve only S3-4 and shows high specific capacity. Herein, the designed Te-0.04 S-0.96@pPAN with 4 mol % Te used as eutectic accelerator exhibits significantly enhanced reaction kinetics and excellent sulfur utilization, leading to a high performance RT Na-S battery. Te0.04S0.96@pPAN delivers capacities of 1236 and 629 mA h g(-1) and 1111 and 601 mA h g(-1) at 0.1 and 6 A g(-1) in carbonate and ether electrolytes, respectively. Furthermore, UV-vis spectra and the shuttle current test reveal diminished sodium polysulfides in ether electrolyte, attributed to the fast kinetics enabled by Te doping. More significantly, the spectral technique and electrochemical analysis demonstrate a two-step reaction pathway in which Na2S3 and Na2S are the main intermediate and final discharge product, respectively. This method provides a promising approach toward applicable RT Na-S batteries.