Research On The Preparation And Performance Of Zinc Ion Hybrid Capacitor

The hybrid energy storage devices can combine the high energy density of the battery with the high power density of the supercapacitor,which is a new type of energy storage devices with excellent electrochemical performance.However,existing lithium ion capacitors and sodium ion capacitors are all based on the transfer of monovalent ions for energy storage,the efficiency of monovalent ion storage is lower than multivalent ion storage.Therefore,applying multivalent ion storage theory to hybrid capacitors can improve the electrochemical performance of hybrid energy storage devices.The main research work of this paper is to apply multivalent ion storage theory to hybrid capacitors to prepare new zinc ion hybrid capacitors.Based on the theory of multivalent ion storage of divalent zinc ions,a new configuration of zinc-ion hybrid capacitors with three kinds of cathode materials was developed by using water-based zinc salt solution as electrolyte.The active carbon anode has the electric double layer effect,and the desorption efficiency of the electrolyte ion on the surface of the active carbon is very high,which can bring a high power density to the system.The cathode material are manganese oxide and vanadium oxide,the zinc ions can inserted and removed from the cathode to bring a high energy density to the system.In addition,since only the electrolyte contains zinc ions in the system,we have also tried to pre-embed zinc ions in the cathode material to compensate for the irreversible zinc ion consumption in the system and improve the stability of the system.The design and preparation of the electrode material and the composition control of electrolyte for the above zinc ion hybrid capacitor can make the energy density of the system reach 34.8 Wh kg^-1 and the power density reaches 13 k W kg^-1.The characterization methods were used to characterize the electrodes and electrolytes in different charge and discharge states,and the charge and discharge mechanism of the system was studied to further improve the electrochemical performance.Investigating the zinc-ion hybrid capacitors of three different cathode materials,we found that the electrochemical performance of the zinc trifluoromethane sulfonate electrolyte is the stablest when manganese dioxide is used as the cathode,its cycle retention rate can achieve 93.4%after 5000 cycles.When vanadium pentoxide is used as the cathode,the system can achieve an excellent cycle retention rate of 97.3%in 6000 cycles in zinc sulfate electrolyte.Besides,pre-embed zinc ions in the cathode material can effectively avoid the consumption of zinc ions by irreversible by-products.We believe that water-based zinc-ion hybrid capacitors have high energy density,high power density and excellent cycle stability.They are also safe,environmentally friendly,inexpensive and easy to obtain.They can be used as an effective next-generation energy storage device solution.