K3MnO4 a New Cathode Material for K-Ion Batteries

Abstract

To meet future energy demands, developing beyond-lithium energy storage technologies have become a major part of global research activities. Potassium-ion batteries (KIBs) represent a promising technology thanks to their chemical and economic advantages1–3. To succeed in developing commercial KIBs, it is necessary to develop new cathode materials4 which must be non-toxic, inexpensive, easy to prepare and have a reasonable K+ diffusion pathway to improve their electrochemical performance. Here we have chosen to explore the inexpensive and non-toxic K-Mn-O system, where only two-dimensional materials of the KxMnO2 type have been studied so far for their electrochemical properties5,6.In this system, a composition attracted our attention: K3MnO4. In principle, up to two potassium ions can be removed from the structure, leading to KMnO4 with a theoretical capacity of 227 mAh/g.Hagenmuller and co-workers succeeded in preparing two polymorphs of K3MnO4 as single crystals7. The high temperature polymorph γ-K3MnO4 has a cubic symmetry (P213) with a disordered distribution of K and Mn in similar tetrahedral sites. The low temperature polymorph β-K3MnO4, can be prepared by annealing γ-K3MnO4 under argon. This polymorph has a tetragonal symmetry (I-42m) with ordered MnO4 tetrahedra. Mn is reported at the edge and at the center of the tetragonal unit cell, surrounded by four oxygens. These phases could be described as a 0D-type structure built of isolated MnO4 tetrahedra surround by potassium ions.We recently succeed in the synthesis of a new polymorph of K3MnO4, labelled α-K3MnO4,8 prepared by a conventional solid-state route by annealing a mixture of KO2 and MnO under vacuum at 500°C in a Al2O3 boat. The structure of this polymorph could be described with a “zig-zag” distribution of the MnO4 tetrahedra (Fig. 1a) and is isostructural to the iron-based K3FeO4 9,10 with an orthorhombic symmetry (Pnma). The blue colour of the powder is classically associated to the Mn+V oxidation state, as confirmed by magnetic and EDS analyses. K3MnO4 exhibits a reversible capacity of 70 mAh/g in the 1.6-3.5 V vs. K+/K potential window at C/20 (Fig. 1b).In our presentation, we will detail the electrochemical behaviour of K3MnO4 and discuss the structure/properties relationship of this family of materials, showing the interest in the exploration of such a system. Xu, Y. et al. 2023 roadmap for potassium-ion batteries. J. Phys. Energy 5, 021502 (2023).Tian, Y. et al. Promises and Challenges of Next-Generation “Beyond Li-ion” Batteries for Electric Vehicles and Grid Decarbonization. Chem. Rev. 121, 1623–1669 (2021).Zhang, W., Liu, Y. & Guo, Z. Approaching high-performance potassium-ion batteries via advanced design strategies and engineering. Sci. Adv. 5, eaav7412 (2019).Nathan, M. G. T. et al. Recent Advances in Layered Metal-Oxide Cathodes for Application in Potassium-Ion Batteries. Adv. Sci. n/a, 2105882.Liu, T. et al. Insight of K-deficient layered KxMnO2 cathode for potassium-ions batteries. J. Energy Chem. 64, 335–343 (2022).Liu, C., Luo, S., Huang, H., Zhai, Y. & Wang, Z. Layered potassium-deficient P2- and P3-type cathode materials KxMnO2 for K-ion batteries. Chem. Eng. J. 356, 53–59 (2019).Olazcuaga, R., Reau, J.-M., Leflem, G. & Hagenmuller, P. Préparation, Proprietés Cristallographiques et Magnétiques des Phases K3XO4 (X=V, Cr, Mn). Z. Für Anorg. Allg. Chem. 412, 271–280 (1975).Sagot, A., Stievano, L. & Pralong, V. K3MnO4: A New Cathode Material for K-Ion Batteries. ACS Appl. Energy Mater. 6, 7785–7789 (2023).Kokarovtseva, I. G., Belyaev, I. N. & Semenyakova, L. V. Oxygen Compounds of Iron(VI, V, IV). Russ. Chem. Rev. 41, 929–937 (1972).Hoppe, R. & Mader, K. Zur Konstitution von K3[FeO4]. Z. F ür Anorg. Allg. Chem. 586, 115–124 (1990). Figure 1