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

Abstract

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 (K0.486V2O5) was synthesized by a simple hydrothermal reaction and further coated with AlF3 by liquid-assistant methodology. The as-modified KVO/AlF3(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 AlF3 coating layer can effectively stabilize the crystal structure of KVO and suppress the harmful side reactions between the electrode and the electrolyte, prompting KVO/AlF3-3 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.

Crystallization and electrochemical properties of KxV2O5 nano-ribbons obtained via a solvothermal process as a promising cathode for PIBs

“…25 When C 6 H 12 O 6 (0.02 and 0.04 g) was added, both KVO-G1 and G2 products can be ascribed to layered monoclinic K 0.486 V 2 O 5 (JCPDS 86-0347) with space group C 2/ m ( a = 11.688 Å, b = 3.668 Å, c = 9.505 Å), whose distinct diffraction peaks appeared at 9.3°, 25.4° and 28.2°, corresponding to the (001), (110) and (003) crystal planes, respectively. 26,27 When the additive amount of C 6 H 12 O 6 increases to 0.08 g, the product KVO-G3 can be generally assigned to the monoclinic VO 2 (B) phase, which belongs to the space group C 2/ m (JCPDS 81-2393). 28 As to KVO-HG, the main peak positions of both KVO-HG0 and HG1 basically conform to the K 0.486 V 2 O 5 phase (JCPDS 86-0347).…”