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

Abstract

Ti3C2Tx MXene with unique physical and chemical properties are recently sparked tremendous interest in the energy storage field. Compared to Ti3C2Tx, V2CTx MXene is a more promising candidate for energy storage due to a low number of atomic layers in the V2CTx structure and varied valence states of vanadium. Herein, we report a flexible V2CTx electrode with different layers (named accordion-like V2CTx, multi-layer V2CTx, and few-layer V2CTx, 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 V2CTx based ZIHC is 54.12 mF cm−2 at 0.1 mA cm−2, which is greater than those of accordion-like V2CTx and multi-layer V2CTx based ZIHC. The outstanding electrochemical performance of few-layer V2CTx based ZIHC is attributed to its richer active sites and shorter ion transport routes. Additionally, the few-layer V2CTx 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 V2CTx based ZIHC is integrated with a Ti3C2Tx based pressure sensor to monitor diverse human activities, demonstrating its steady and long-term power supply capacity as the energy storage device.