Flexible reduced graphene oxide/V2O5 composite battery-type cathode and MXene capacitor-type anode for aqueous zinc ion hybrid supercapacitors with high energy density

To meet the rapid development of flexible supercapacitors with both high energy density and power density, hybrid ion capacitors like lithium and sodium ion capacitors have attracted more and more attention. However, the hidden danger associated with the using of organic electrolytes limit their practical application. In this regard, a new configuration flexible zinc-ion hybrid supercapacitor (ZHSC) based on free-standing films of RGO-V2O5 (RGV) battery-type cathode and RGO-MXene (RGM) capacitor-type anode in aqueous electrolyte has been designed. The RGM/RGV system consists of specific layered structure, short ion diffusion pathway, high electrical conductivity and exceptional structural stability. As a result, the ZHSC based on RGM/RGV exhibits excellent electrochemical performance, including a large specific capacity of 175 F g−1 at 0.5 mV s−1, a maximum energy density up to 107.2 Wh kg−1 (321.6 W kg−1) and a high capacitance retention of 81% of its initial capacitance (10,000 cycles). Additionally, the ZHSC displays a high specific capacity of 125 F g−1 at 0.5 mV s−1 even in an aqueous gel electrolyte. More importantly, supercapacitors based on the composite films exhibit stable flexibility electrochemical performance. The investigation provides an essential strategy to synthesize composite films for application in high performance flexible hybrid supercapacitors.