Intralayer ordered structure engineering for long-life Mn-based potassium-ion battery cathodes

Abstract

Mn-based layered oxides have become one of the most promising cathode materials in potassium-ion batteries (PIBs) due to their high theoretical specific capacity. Nonetheless, the Jahn-Teller effect of Mn3+ leads to lattice distortion and a high K+ migration barrier, resulting in structural instability during the charge/discharge processes. To effectively overcome these problems, this work provides a method to change electronic energy levels to suppress the Jahn-Teller effect through the synergistic regulation of multiple specific element doping. The X-ray diffraction pattern of K0.4Mn0.7Ti0.1Ni0.1Cu0.1O2 shows its P3-type structure. The electrochemical test results demonstrate that K0.4Mn0.7Ti0.1Ni0.1Cu0.1O2 exhibits superior rate capacity, higher discharge specific capacity, and significant cycling stability (with a capacity retention rate of 80 % after 860 charge/discharge cycles). The in-situ X-ray diffraction pattern demonstrates the high reversibility of the electrochemical process of K+ insertion/extraction. First-principles calculations have confirmed that the electronic energy levels of K0.4Mn0.7Ti0.1Ni0.1Cu0.1O2 have better dispersion, the K+ migration channel has been effectively optimized, and the K+ migration barrier has been reduced. This study provides a significant and effective reference for the design of advanced PIBs with high performance.