Potassium batteries for low temperature applications using high energy density organic cathodes

Abstract

We introduce two highly promising polymeric cathode materials for potassium batteries prepared using simple and scalable single-step synthesis from triquinoyl and tetraaminophenazine as precursors. The obtained materials have been extensively characterized in the solid state using a set of complementary spectroscopic and physicochemical techniques and also computational methods to unravel the peculiarities of their molecular structures and also the nature of the formed structural defects. Importantly, both polymers were capable of complete utilization of all redox centers in their chemical structures (CO groups and pyrazine rings) with respect to electrochemical reduction and potassium ion storage, thus enabling theoretical specific capacities of 638 and 574 mA h g⁻¹. Even though the achieved practical capacities of 400–475 mA h g⁻¹ were considerably lower than the theoretical values, they enabled record-high energy densities of 800–950 W h kg⁻¹ for organic cathodes in potassium cells. Furthermore, the fabricated batteries have demonstrated excellent operation at low temperatures between −20 and −55 °C with minimal capacity depression. These findings feature a considerable potential of organic potassium batteries for a broad range of applications, e.g., in the aerospace industry and other fields where stable battery performance at low temperature is crucially required.