Abstract
Manganese-based layered oxides are promising cathode materials for potassium-ion batteries (PIBs) due to their low cost and high theoretical energy density. However, the Jahn-Teller effect of Mn(3+) and sluggish diffusion kinetics lead to rapid electrode deterioration and a poor rate performance, greatly limiting their practical application. Here, we report a Co/Al co-substitution strategy to construct a P3-type K(0.45)Mn(0.7)Co(0.2)Al(0.1)O(2) cathode material, where Co(3+) and Al(3+) ions occupy Mn(3+) sites. This effectively suppresses the Jahn-Teller distortion and alleviates the severe phase transition during K(+) intercalation/de-intercalation processes. In addition, the Co element contributes to K(+) diffusion, while Al stabilizes the layer structure through strong Al-O bonds. As a result, the K(0.45)Mn(0.7)Co(0.2)Al(0.1)O(2) cathode exhibits high capacities of 111 mAh g(-1) and 81 mAh g(-1) at 0.05 A g(-1) and 1 A g(-1), respectively. It also demonstrates a capacity retention of 71.6% after 500 cycles at 1 A g(-1). Compared to the pristine K(0.45)MnO(2), the K(0.45)Mn(0.7)Co(0.2)Al(0.1)O(2) significantly alleviates severe phase transition, providing a more stable and effective pathway for K(+) transport, as investigated by in situ X-ray diffraction. The synergistic effect of Co/Al co-substitution significantly enhances the structural stability and electrochemical performance, contributing to the development of new Mn-based cathode materials for PIBs.