Zn Doping Strategy to Suppress the Jahn–Teller Effect to Stabilize Mn‐Based Layered Oxide Cathode toward High‐Performance Potassium Ion Batteries

Abstract In the research report of cathode of potassium ion battery, Mn‐based layered structural oxides have attracted the researcher's attention because of its good energy density and high specific rate capacity. However, the Jahn–Teller effect is the main limiting factor for their development. It leads to the expansion and deactivation of Mn‐based layered metal oxides during cycling for a long time. Therefore, mitigation of the Jahn–Teller effect is considered a useful measure to enhance the electrochemical capability of Mn‐based layered oxide. In this paper, an R 3 m‐type K 0.4 Mn 0.7 Co 0.25 Zn 0.05 O 2 cathode material is designed through a Zn doping strategy. X‐ray diffraction techniques and electrochemical tests verified that the Jahn–Teller effect is effectively mitigated. High performance is achieved in the rate capacity test with 113 mAh g −1 at 50 mA g −1 . Comparison with similar materials in recent years has demonstrated its superiority, leading rate performance among Mn‐based metal oxides reported in recent years. The practical feasibility is verified in the assembled full cell with soft carbon in anode materials and K 0.4 Mn 0.7 Co 0.25 Zn 0.05 O 2 as cathode. In the full cell rate test, 104.8 mAh g −1 discharging capacity is achieved at 50 mA g −1 current density.