Toward Heat-tolerant Potassium Batteries based on Pyrolyzed Selenium Disulfide/ Polyacrylonitrile Positive Electrode and Gel Polymer Electrolyte
K-S batteries attract increasing research attention as a promising energy storage system. However, they suffer from the slow reaction kinetics, attributing to the large radius of potassium ions and insulating nature of sulfur. In addition, good heat tolerance of K-S batteries is crucial but not easy to realize, due to the low melting point of potassium metal. Herein, we report a K-S battery which can be operated at both high and room temperatures with remarkable electrochemical performance, using pyrolyzed selenium disulfide/ polyacrylonitrile (SeS2-CPAN) as positive electrode and a gel polymer as electrolyte. SeS2-CPAN can be prepared via a calcination process. By taking advantages of both sulfur and selenium, it delivers a remarkable reversible capacity of 263 mA h g-1 (840.3 mA h gSeS2-1) at 100 mA g-1 and excellent rate performance (152.7 mA h g-1 at 2000 mA g-1) at room temperature. When raising the temperature to 50 oC, the K//SeS2-CPAN cell with liquid electrolyte and porous separator can not be cycled. However, with gel polymer electrolyte, the cell delivers an initial reversible capacity of 304.9 and 229.6 mAh g-1 (974.1 and 733.5 mA h gSeS2-1) at 100 and 500 mA g-1, respectively, and it exhibits good cycle and rate performance as well. The gel polymer electrolyte mitigates the penetration of softened potassium and circumvents the short circuit, leading to the remarkable electrochemical performance at high temperature. This contribution demonstrates an effective and facile strategy to extend the application of potassium batteries, especially at high temperatures. In addition, the reaction mechanism and kinetics between SeS2-CPAN and potassium are discussed.