Self-charging V2CTx/CNT-based zinc ion micro-supercapacitor for wearable electronics

The flexible self-charging zinc ion micro-supercapacitors (ZIMSC) that can be effectively charged by harvesting ubiquitous energy from the air, not only achieve power supply anytime and anywhere but also improve the integrated degree without external charging plug or cable, enabling it a promising candidate for the wearable electronic device in various environmental scenarios. Herein, we reported a chemically self-charging ZIMSC based on a free-standing V2CTx/CNT electrode. Introducing 1D CNT into 2D V2CTx fundamentally overcomes the self-stacking problem of the nanosheets while providing additional ion transport paths and improving the conductivity of active electrodes. The area-specific capacity of V2CTx/CNT-based ZIMSC achieves 117.2 mF cm−2 after 8.0 h self-charging. The excellent self-charging performance is attributed to the oxidation of vanadium in the V2CTx-based cathode stimulated by ambient oxygen, accompanied by the Zn2+ deintercalation process. The flexible ZIMSC exhibited an optimal area capacitance of 246.88 mF cm−2 at a current density of 0.5 mA cm−2. Additionally, the self-charging ZIMSC is integrated with the V2CTx-based pressure sensors for a self-powering wearable system that exhibits excellent stability over 50,000 loading/unloading cycles. This work provides a rational design for constructing highly efficient self-charging energy storage devices and broadens the horizons of flexible wearable devices