Research On Preparation And Performance Of Electrode Materials For Zinc-ion Hybrid Capacitors

As an excellent energy storage system,supercapacitors have been widely applied in some electronic devices due to their excellent power density and rapid charging and discharge.However,with the rapid development of the economy,energy failure and environmental pollution have become increasingly serious,which has put forward higher requirements for energy storage technology.As a new type of energy storage system,zinc ion hybrid capacitors(ZHC)combine the merits of battery and supercapacitors that are widely studied due to the high security and low-cost nature.In addition,the requirement for ZHC is not only excellent electrochemical performance,but also flexible characteristics to meet the needs of wearable electronic energy storage devices.Therefore,the main research of this paper is to develop the positive material of zinc ion hybrid capacitor,and the corresponding flexible devices are also prepared.(1)Mn O₂@CC composite materials with a dense needle-shaped structure show good flexibility,which can be assembled to zinc ion hybrid capacitor with activated carbon materials as the negative electrode.Thanks to the high surface area and rapid ionic transport dynamics,the device can reach a high capacity of 589 m F cm^-2.The analysis of SEM and XRD confirmed the presence of Zn₄(OH)₆SO₄·0.5H₂O,and the contribution of its dissolution and precipitation process on the CC surface to the capacity was explained.At the same time,in order to improve the electrochemical properties of flexible devices,different zinc salt electrolytes were prepared to explore its impact on the electrochemical properties of flexible devices.(2)V₂O₅ successfully embedded with metal ions and water molecules into its layered structure,and a composite material(NVO)of nanoflow structure was prepared.In order to prevent the irreversible phase change and structure collapse when larger hydrophilic Zn²⁺embedding in the V₂O₅ layer,co-doping was applied to expansion the laminar spacing and effectively stabilized the structure.An aqueous zinc-ion hybrid capacitor was assembled by using NVO as the positive electrode and the activated carbon electrode as the negative electrode.This hybrid capacitor showed excellent performance under the optimal ratio of positive and negative with high capacity of 52 m Ah g^-1 at 0.1 A g^-1.Furthermore,the device shows good cycle stability,with 100%capacity retention after 5000 cycles.This study provided a valid and stable ion storage strategy for the vanadium-based ZHC.(3)In order to meet the flexibility requirement of the zinc ion hybrid capacitor,the NVO@CC positive composite material was prepared.At the same time,the smooth surface of the CC was activated with KOH.On the basis of maintaining the flexibility,the CC obtains a rough and high surface area which greatly improves the capacity of the electrode.Because the Cl^-can play a decomposition of the aquarium Zn²⁺cluster,Zn Cl₂/PVA was used as the gel electrolyte for zinc ion hybrid capacitor.The device shows the area capacitance value of267.1 m F cm^-2,and the single device can easily light up the timer,which presents high energy density(148.4?Wh cm^-2)and shows great potential as flexible devices.