A new flexible zinc-ion capacitor based on δ-MnO2@Carbon cloth battery-type cathode and MXene@Cotton cloth capacitor-type anode

Abstract With the rapid development of flexible electronic devices, current flexible energy storage devices face great challenge of achieving both high energy and power density. Exploiting ion capacitor is an intelligent way to improve the energy density without sacrificing the power density by utilizing the battery and capacitor-type energy storage mechanism. For the inspiration, a new flexible zinc-ion capacitor (FZIC) based on δ-MnO2@carbon cloth (δ-MnO2@CAC) battery-type cathode and MXene@cotton cloth (MXene@COC) capacitor-type anode has been designed and realized. The δ-MnO2@CAC//MXene@COC system in aqueous liquid electrolyte exhibits excellent electrochemical performance, e.g. a high energy density of 90 Wh kg−1 (power density of 239 W kg−1) and a high power density of 3838 W kg−1 (energy density of 26.8 Wh kg−1), a high capacitance retention of ~80.7% of its initial capacitance after 16,000 cycles and a high Coulomb efficiency of above 93.6% during all the cycles. Moreover, after being assembled by aqueous gel electrolyte, the FZIC also shows the superior electrochemical performance and excellent flexibility. This study of the FZIC provides an efficient way to develop the next-generation flexible energy storage devices with high performance.