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

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 R₃m-type K_0.4Mn_0.7Co_0.25Zn_0.05O₂ 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_0.4Mn_0.7Co_0.25Zn_0.05O₂ as cathode. In the full cell rate test, 104.8 mAh g^-1 discharging capacity is achieved at 50 mA g^-1 current density.