High Energy Density Cathode Frameworks for Potassium-Ion Battery

Abstract

Potassium-ion battery (PIB) has recently attracted great attention not only as a low-cost alternative to lithium, but also as a high-voltage contender considering the significantly negative potential of the K + /K redox couple, which is close to or even lower than that of Li + /Li depending on the solvent [1-3]. However, the large ionic radius of potassium limits the number of potassium-based compounds that can practically be utilized as high capacity materials. As shown in Fig. 1, a vast number of polyanion-based frameworks exhibit high voltages, prime among them being vanadium-based compounds ( viz ., KVPO 4 F, KCoSO 4 F, KNiSO 4 F and KVOPO 4 [4]) that show voltages exceeding 4 V vs. K. Equally important as the high voltage is high capacity, that is difficult to achieve considering the high molecular weight of most of the K-containing polyanion frameworks. This has motivated an impetus to develop high capacity oxide-based cathode materials for PIB. We will highlight potential potassium-rich manganese- and iron-based oxides, while underpinning promising polymorphs of phosphate-and sulphate-based polyanion cathode frameworks. Reference s : [1] Y. Marcus, Pure Appl. Chem. , 57 (1985) 1129-1132. [2] S. Komaba, T. Hasegawa, M. Dahbi and K. Kubota, J . Power Sources, 60 (2015) 172-175. [3] A. Eftekhari, J. Power Sources, 126 (2004) 221-228. [4] T. Masese, M. Shikano, H. Sakaebe, H. Senoh and H. Sano, PCT /JP2017/000301. Figure 1