The Fabrication And Electrochemical Performance Of Zinc-Cobalt-Nickel Hydroxide Electrode

Supercapacitors are widely used in information communication,energy vehicles,medical equipment and other fields due to their advantages such as fast charging and discharging,high power density,environmentally friendly.Electrode material,as a key component of supercapacitors,has a great impact on the performance of supercapacitors.Transition metal hydroxides have received extensive attention in the field of supercapacitors due to their high theoretical specific capacitance,low cost,and environmentally friendly.In this thesis,several different electrode materials were synthesized by direct current electrodeposition,pulse electrodeposition,and ultrasonic pulse electrodeposition methods.SEM,XRD and other methods were used to characterize and analyze the electrodes.The electrochemical performance of the electrodes were evaluated by CV,GCD and EIS.The main results obtained are as follows:(1)Cobalt hydroxide,nickel hydroxide,cobalt-nickel bimetal hydroxide,Zn-doped cobalt hydroxide,Zn-doped nickel hydroxide,and Zn-doped cobaltnickel bimetal hydroxide electrodes(abbreviated as Co,Ni,CN,ZC,ZN,ZCN)were prepared on the nickel foam by direct current electrodeposition.Among them,the Ni electrode has a high specific capacitance,but the rate performance and cycle stability are poor.The CN electrode has a higher specific capacitance and better cycle stability,but the rate performance is poor.The ZCN electrode has a excellent rate performance and good cycle stability.Because after the incorporation of Zn2+ions into the lattice,not only reduces the charge transfer resistance,but also improves the reversibility of the electrode reaction.Therefore,the rate performance and cycle stability are significantly improved.(2)The above-mentioned six kinds of electrodes(abbreviated as P-Co,PNi,P-CN,P-ZC,P-ZN,P-ZCN)were prepared by pulse electrodeposition.Among them,the P-Ni electrode is significantly improved compared with the electrode prepared by direct current electrodeposition,however,the specific capacitance is relatively low.The P-CN electrode has a good cycle stability,but it shows a lower specific capacitance.The P-ZCN electrode exhibits a high specific capacitance and excellent rate performance,but its cycle stability is slightly poor.(3)Cobalt-nickel bimetal hydroxide and Zn-doped cobalt-nickel bimetal hydroxide electrodes(abbreviated as UP-CN and UP-ZCN)were prepared by ultrasonic pulse electrodeposition.The results show that the active material is deposited more uniformly by ultrasonic pulse electrodeposition.Among them,the UP-CN electrode has a high specific capacitance and excellent rate performance,but its cycle stability is poor,which is determined by the characteristics of cobalt and nickel materials.The UP-ZCN electrode has a higher specific capacitance,better rate performance,and better cycle stability.(4)Moreover,an asymmetric supercapacitor was designed based on a UPZCN cathode and an active carbon anode.The supercapacitor possessed high energy densities(39.6 Wh kg-1 at 400 W kg-1 and 20.3 Wh kg-1 at 6347 W kg-1)and extraordinary cycling stability(85.5%of initial capacity after 1000 cycles at a high current density of 6 A/g).This UP-ZCN electrode therefore has potential applications as a cathode material for supercapacitors.