Designed Synthesis And Electrochemical Performance Of Three Potassium Vanadates Nanowires

As a typical layered metal oxide, vanadium oxide nanomaterial is highly valued for the kinds of oxidation state and existence of coordination polyhedron which makes it process a open structure for the insertion of metal ion. As a result, it obtains a long-term development and research as a promising lithium-ion battery material. Potassium vanadates have a layered structure, besides, the lithium ion embedded in the layers has an ionic bond with the layers which would enlarge the interlayer space and improve the stability of the layered structure. Nanowire electrode has also raised great attentions due to large aspect ratio, high electrode-electrolyte contact area, adial electronic limited domain effect and axial electronic transmission characteristic. An ideal cathode material for high-rate Li-ion battery should have high electrical conductivity for fast electron transport, short diffusion distances for fast Li ion migration, and a large surface area. It’s significant to synthesis one dimensional potassium vanadates for improving the electrochemical properties of vanadium oxides, and strongly supporting the development of new energy technology.In this paper, using hydrothermal and solid phase sintering method, KV3O8, K2V8O21, KV6O15nanowires were designed and synthesized by controlling the molar ratio of potassium and vanadium. Then the structure and morphology of them were characterized by XRD, SEM, TEM, etc. testing methods. Cyclic voltammetry and constant-current charge and discharge were used to explore the electrochemical properties, and research the cycling performance at100,500,1000mA/g, respectively.When the current density is100mA/g, the initial capacity of KV3O8, K2V8O21, KV6O15is208,215,180mAh/g, respectively, the retention ratio is59.13%,70.70%,86.11%after100cycles. When the current density is500mA/g, the retention ratio of them is51.53%,80.00%,122.55%after400cycles, respectively. When the current density is1000mA/g, the retention ratio of them is42.09%,56.06%,91.62%, respectively, after1000cycles.It’s shown that KV6O15is the best, K2V8O21is the second, KV3O8is the worst. When the current density is500mA/g, the KV6O15nanowires400th capacity is 125mAh/g, amazing bigger than the initial capacity. When the current density is1000mA/g, the retention ratio is91.62%after1000cycles, corresponding to a capacity fading of only0.0087%per cycle, showing a very good cycling performance.Such performance indicates that the cycling performance becomes better by bring potassium into the vanadium oxide, and much better when the ratio of potassium and vanadium decreasing from1:3to1:4to1:6. These data demonstrate that potassium vanadates nanowires are promising cathode materials for long-life Li-ion battery and support it.