Aluminum Fluoride Coating on Layered Vanadium-Based Cathode Materials with Enhanced K Storage Performance in the High Potential Range

Layered transitional metal oxides are regarded as the most potential cathode materials in the upcoming K-ion batteries with the advantages of a short ionic diffusion path, high specific capacity, and environmental friendliness. Nevertheless, due to the large ionic radius of K +, they usually suffer from the collapse of the structure and the possibility of decomposition of the electrolyte, especially in the high voltage range, resulting in fast capacity loss. Herein, typical potassium-rich vanadium-based oxide (K 0.486 V 2 O 5 ) was synthesized by a simple hydrothermal reaction and further coated with AlF 3 by liquid-assistant methodology. The as-modified KVO/AlF 3 (3 wt %) shows significantly enhanced cyclic performance and rate performance compared to bare KVO in the high potential (1.5–4.1 V) as well as normal ranges (1.5–3.8 V). The results suggest that a proper thickness of the AlF 3 coating layer can effectively stabilize the crystal structure of KVO and suppress the harmful side reactions between the electrode and the electrolyte, prompting KVO/AlF 3 -3 to exhibit a much higher energy density than the bulk one. This work contributes to the important basic scientific significance of surface coating methodology for the development and application of layered transitional metal oxides in K-ion batteries.