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 K₆TeO₆ 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 K₂Ni₂TeO₆, a new cathode material synthesized via the conventional solid state method. The structure entails a honeycomb-like network of NiO₆ octahedra (in purple) surrounding each TeO₆ octahedon (in blue). Potassium atoms (in brown) occupy trigonal prismatic sites sharing faces with NiO₆ or TeO₆ octahedra.

During the meeting, we will highlight the synthesis, crystal structure and electrochemical performance of K₂Ni₂TeO₆ as a new cathode material for PIB [3].

References:

[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 K₂Ni₂TeO₆ viewed along [110] direction. NiO₆

tetrahedra (blue), TeO₆ octahedra (purple), and K atoms (brown) are illustrated.