3D porous H-Ti3C2Tx films as free-standing electrodes for zinc ion hybrid capacitors

Abstract

Flexible zinc ion hybrid capacitor (ZICs) as a kind of emerging energy storage devices have great prospect for grid-scale energy storage and wearable electronics due to some advantages such as appropriate density, superb power output, abundant zinc resources, and nontoxic nature. Currently, there are still great demands to seek and design novel electrodes for zinc ion hybrid capacitors, especially for flexible free-standing electrode. Herein, a novel rechargeable aqueous Zn-ion hybrid capacitor using 3D porous H-MXene film (3D-PHMF) as the cathode was reported. The 3D porous H-MXene film was constructed with an interlayer interaction engineering via freeze-casting method, wherein the hydrogen ion (H+) was introduced to weaken electrostatic repulsion of MXene interlayer. The aqueous Zn//3D-PHMF capacitor delivers a specific capacitance of 105.6 mAh g−1 at 0.2 A g−1 and good rate performance of 61.0 mAh g−1 at 5 A g−1 with remarkable cycling stability, which remains 90% of specific capacitance after 20,000 cycles. Besides, the capacitor also shows outstanding anti-self-discharge ability in which the self-discharge rate is 1.87 mV h−1. Remarkably, the as-obtained flexible cathode can be designed into a flexible quasi-solid-state device, which shows excellent flexibility and stability. This work demonstrates the promising possibility of MXene as free-standing electrode for energy storage applications.