Multi-element doping induced transition metal disordered layered oxide for rapid and stable potassium storage

Layered transition metal oxides are highly desirable cathode materials for potassium-ion batteries (PIBs) because of their considerable theoretical capacity and high output voltage. However, the ordered structure of these oxides limits K+ transport kinetics and the stability of the layered structure, resulting in poor rate and cycling performance. Here, a novel disordered Mn-based quinary transition metal oxide cathode, K0.7Fe0.05Co0.1Mn0.75Ni0.05V0.05O2, was developed for use in high-performance PIBs. The designed K0.7Fe0.05Co0.1Mn0.75Ni0.05V0.05O2 is a completely disordered transition metal that exhibits excellent rate capability (77.39 mA h g−1 at 1000 mA g−1) and long cycle life (∼70.3% capacity retention at 1000 mA g−1 after 500 cycles). The kinetics of the facilitated electrode process was demonstrated by density functional theory calculations, where the disordering of transition metals effectively reduces the energy barrier of K+ migration while increasing the electronic conductivity. In situ X-ray diffraction verifies the highly reversible structural evolution during potassium insertion/extraction, achieving an ultra-low volume change (0.65%). The enhanced performance is attributed to a larger d-spacing and stronger metal–oxygen bond. Such results substantiate that multi-element doping to induce quinary disordered transition metals is an efficient strategy to enhance the electrochemical performance of layered oxides and provide a new guideline for the design of advanced PIBs.