Highly Transparent and Flexible Zn-Ti₃C₂T_x MXene Hybrid Capacitors

Abstract

With the development of transparent and wearable electronic devices, energy supply units with high transmittance and flexibility, long cycle life, and high power and energy density are urgently needed. Zinc ion hybrid capacitors (ZIHCs) combined with the advantages of both supercapacitors and zinc ion batteries are promising energy supply components in the abovementioned devices. In addition, the preparation of multifunctional devices has become a trend for the need of space- and resource-saving. Therefore, obtaining ZIHCs with high transmittance and exploring their potential applications are meaningful challenges. Herein, a transparent and flexible ZIHC composed of a patterned zinc foil anode, transparent MXene cathode, and ZnSO₄-polyacrylamide (PAM) hydrogel electrolyte is designed and realized. The ZIHC exhibits a superior capacitance of 318 μF cm^-2 (5 mV s^-1) with 94% transmittance and retains 76% of the initial capacitance after 10,000 charge-discharge cycles. It also shows excellent flexibility, i.e., its capacitance has no obvious attenuation under different bending states. Interestingly, the leakage current of the ZIHC is highly sensitive to electric fields, which shows potential application in electric field detection. This work presents a method to realize the multifunctional ZIHC with electric field sensing function for transparent and flexible wearable devices in the future.