Research status and development trend of layered K<italic><sub>x</sub></italic>MnO<sub>2</sub>-based cathode materials for potassium-ion batteries

Abstract

<p indent="0mm">Potassium-ion batteries have the advantages of abundant resources, low price, and similar principles to lithium-ion batteries, and are currently promising candidates to replace lithium-ion batteries as large-scale energy storage systems. Cathode materials play a key role in the performance of potassium-ion batteries, among which layered K<italic>_x</italic>MnO₂-based cathode materials have attracted much attention due to their high specific capacity, environmental friendliness, low cost, and unique two-dimensional structure. However, the repeated intercalation/deintercalation of large-sized K⁺ during the charging and discharging process will lead to the structural damage, and the Jahn-Teller effect generated by Mn³⁺ can easily cause structural distortion, resulting in a rapid capacity decrease of potassium-ion batteries, which much hinders their commercial application. Beginning with the control of the layered structure of K<italic>_x</italic>MnO₂ materials, this review systematically summarizes the preparation methods of K<italic>_x</italic>MnO₂-based cathode materials, and focuses on the doping modification of K<italic>_x</italic>MnO₂-based cathode materials, including single metal doping, dual metal doping and alkali metal doping. And this paper summarizes the main challenges existing in the current research and further looks forward to its future development direction, which is expected to provide a theoretical reference for the development of high-efficiency and stable potassium-ion batteries.