Orthotellurate Cathode Frameworks for Potassium-Ion Battery

Abstract

As a low-cost alternative to lithium, potassium-ion battery (PIB) has recently attracted great attention. PIB can be a high-voltage contender considering the significantly negative potential of the K + /K redox couple, which is close to or even lower than Li depending on the solvent [1,2]. Nonetheless, the large ionic radius of potassium coupled with significant strain accompanying potassium (de)insertion, the number of potassium-based compounds (particularly, cathode materials) that can practically be utilized is limited. Exploration of the broad class of orthotellurate frameworks based on K 6 TeO 6 has led us to identify new cathode frameworks that can reversibly (de) insert potassium ions, not only at high voltage but also at decent capacities. Figure 1 shows a layered crystal structure of K 2 Ni 2 TeO 6 , a new cathode material synthesized via the conventional solid state method. The structure entails a honeycomb-like network of NiO 6 octahedra (in purple) surrounding each TeO 6 octahedon (in blue). Potassium atoms (in brown) occupy trigonal prismatic sites sharing faces with NiO 6 or TeO 6 octahedra. During the meeting, we will highlight the synthesis, crystal structure and electrochemical performance of K 2 Ni 2 TeO 6 as a new cathode material for PIB [3]. 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] T. Masese, K. Yoshii, T. Okumura, H. Senoh, M. Shikano, manuscript submitted. Figure 1. Schematic presentation of K 2 Ni 2 TeO 6 viewed along [110] direction. NiO 6 tetrahedra (blue), TeO 6 octahedra (purple), and K atoms (brown) are illustrated. Figure 1