A flexible zinc ion hybrid capacitor integrated system with layers-dependent V2CTx MXene

Ti 3 C 2 T x MXene with unique physical and chemical properties are recently sparked tremendous interest in the energy storage field. Compared to Ti 3 C 2 T x , V 2 CT x MXene is a more promising candidate for energy storage due to a low number of atomic layers in the V 2 CT x structure and varied valence states of vanadium. Herein, we report a flexible V 2 CT x electrode with different layers (named accordion-like V 2 CT x , multi-layer V 2 CT x , and few-layer V 2 CT x, respectively) fabricated by using electrophoretic deposition, then assembled a flexible zinc ion hybrid capacitor (ZIHC) by virtue of zinc anode and gel electrolyte. The areal capacitance of few-layer V 2 CT x based ZIHC is 54.12 mF cm −2 at 0.1 mA cm −2 , which is greater than those of accordion-like V 2 CT x and multi-layer V 2 CT x based ZIHC. The outstanding electrochemical performance of few-layer V 2 CT x based ZIHC is attributed to its richer active sites and shorter ion transport routes. Additionally, the few-layer V 2 CT x based ZIHC also owns well cycling stability, with 81.48 % capacity retention after 8000 cycles, and a low self-discharge rate of 6.4 mV h −1 , making it suitable for wearable devices. So, the V 2 CT x based ZIHC is integrated with a Ti 3 C 2 T x based pressure sensor to monitor diverse human activities, demonstrating its steady and long-term power supply capacity as the energy storage device.