Research On Preparation And Performance Of Cathode Materials For Water-based Zinc-ion Hybrid Capacitors

With the fast development of the economy,the demand for transportable digital units and electric powered motors is increasing,which puts forward higher requirements for new and efficient energy storage technologies.Various electrochemical energy storage devices have emerged and have been widely used in miniaturized optoelectronics/electronic equipment,consumer electronics,etc.Zinc-ion hybrid capacitors（ZSC）have attracted widespread attention as a new type of multivalent energy storage device.In addition,ZSC can also have good electrochemical performance under the requirements of energy storage of daily wearable electronic devices,and also has extremely high safety stability and ultra-low cost.Therefore,in this paper,ZSC cathode materials are used as the main research content,and three flexible energy storage devices with different cathode materials are prepared.（1）A nitrogen-doped MnO₂ composite material（N-MnO₂）with a nanowall-type structure with good flexibility was grown on the surface of flexible carbon cloth by in-situ electrodeposition method,and a zinc-ion hybrid capacitor（ZSC）was assembled with a commercial activated carbon（AC）negative electrode,due to the rapid ion transport kinetics and stable nanowall-type structure,its specific capacitance could reach 1282.5 m F cm^-2 in the aqueous test,and the capacity retention rate was 92.9%after 25,000 continuous charge-discharge tests.At the same time,2 flexible devices connected in series can easily light up 35 light-emitting diodes,showing the application potential of flexible devices.（2）Nanorod-type MnO₂ composites with good stability characteristics were grown on the surface of the flexible carbon cloth woven into shafts by one-step hydrothermal method,and the cyclic stability of Zn-MnO₂ electrode materials was greatly improved by pre-doping of zinc ions.The specific capacitance can reach 1300 m F cm^-2 in the aqueous two-electrode test,and after 20,000 continuous charge-discharge tests,the coulomb efficiency remains 100%and the capacity retention rate is 83.75%.At the same time,two flexible devices connected in series can easily light up small bulbs under bending conditions,showing the application potential of flexible devices under harsh conditions.（3）MnO₂-r GO was synthesized by simple ultrasonic mixing plus freeze drying.r GO provides good electrical conductivity and provides more active sites for the electrode material,making the redox reaction more complete,and alleviating the lattice distortion caused by the subsequent zinc hydrated ion on the electrode material.By adjusting the ratio of carboxymethylcellulose（CMC）,polyvinyl alcohol（PVA）and ethylene glycol（EG）in the electrolyte,a low-temperature quasi-solid electrolyte resistant to-20°C was prepared.After 5000 continuous cycles at-20°C,the cycle retention rate was maintained at 89.189%.At the same time,the coulomb efficiency remained above 90%,exceeding most of the reported flexible ZSC.The above results show that the prepared ZSCs have excellent electrochemical performance,good electrochemical stability under low temperature bending conditions,and show excellent application potential in the flexible field.