Component design and regulation to stabilize P3-type Mn-based layered cathodes for potassium-ion batteries

Mn-based layered oxides with high theoretical capacity are one of the most promising cathode materials for potassium-ion batteries. However, the Jahn-teller distortion of Mn3+ in Mn-based layered cathodes always brings about harmful disordered structure and irreversible phase transition, resulting in severe degradation of electrochemical performance. Herein, we synthesized P3–K0.5Mn0.6Ni0.2M0.2O2 (M = Fe, Co, FeCo) and systematically investigate the effect of component regulation on the layered structure and electrochemical properties. The P3–K0.5Mn0.6Ni0.2Co0.2O2 exhibits a discharge capacity of 73.77 mAh g−1, demonstrating an excellent capacity retention rate of 70.17 % after 120 cycles at 50 mA g−1. In-depth analysis reveals that P3–K0.5Mn0.6Ni0.2Co0.2O2 possesses a larger K+ layer spacing, making the insertion/extraction of potassium ions become much easier. Furthermore, the introduction of Co into the transition metal layer enhances the content of Mn4+, thereby inhibiting Jahn-Teller distortion and improving structural stability. Especially, the P3–K0.5Mn0.6Ni0.2Co0.2O2 shows a highly reversible single-phase solid solution reaction during the initial cycle, which means the detrimental phase transition of P3–O3 caused by Jahn-Teller effect is effectively suppressed. This work contributes to a better understanding of the effect of component design and regulation on the performance of the layered oxides cathode and provide insight into the design of high-performance cathode materials for potassium-ion batteries.