A novel intercalation pseudocapacitive electrode material: VO(OH)2/CNT composite with cross-linked structure for high performance flexible symmetric supercapacitors

Fabrication of a novel electrode material with efficient storage mechanism is a desirable strategy to build a better supercapacitors. Herein, a novel intercalation pseudocapacitance material, VO(OH)₂/CNT binary composite with cross-linked structure, is first successfully synthesized by a facile one-step hydrothermal method. This composite combines the intrinsic positive traits of each component, in which the synergistic efforts greatly enhance to achieve a considerable electrochemical performance. In the three-electrode system, VO(OH)₂/CNT composite electrode exhibits a capacitance of 256 F·g⁻¹ (512C·g⁻¹) at 0.5 A·g⁻¹ within the wide potential range of −0.8–1.2 V. More remarkably, the VO(OH)₂/CNT-based flexible symmetric supercapacitor delivers a high energy density of 32.08 Wh·kg⁻¹ at a power density of 63.65 W·kg⁻¹ in a large operating voltage of 2.2 V. As well as, it performs a well cycling stability that the capacitance retention is about 90% after 3000 cycles. For the factual application measurement, two devices in series can light red LED for 5 min after charging 100 s. This work enriches the exploration of vanadium oxyhydroxides' pseudocapaicitance performance, which is of great significance to the future application of vanadium oxyhydroxides in energy storage.