Structure Optimization Of Layered Transition Metal Hydroxide And Its Application In Supercapacitors

Supercapacitors have received widespread attention due to their higher power density,excellent rate performance and cycle performance,but their low energy density has limited their development and applications.This is because the electrochemical reactions in supercapacitors mainly occur on the electrode surface,and the utilization rate of active materials is relatively low.Therefore,the development of embedded capacitor materials is an effective strategy to increase energy density.Cobalt hydroxide and nickel hydroxide are typical intercalation capacitor materials.Their unique layered structure facilitates the diffusion and reaction of ions,thus exhihit a excellent energy storage capacity.However,their performance has not been fully utilized in practical applications,and some commonly used modification methods require higher material and technical costs,which is not conducive to large-scale production and application.Therefore,on the basis of the above two materials,this paper innovatively selects the anion and cation co-intercalation strategy,and introduces potassium and chloride ions into transition metal hydroxide materials,which effectively improves the performance of such materials.The specific works are as follows:?1?The effect of different ionic intercalation on the properties of cobalt hydroxide.By characterizing and comparing of cobalt hydroxide without ion ions,chloride ions,potassium ions,and two ions co-embedded,it was found that the insertion of chloride ions will increase the adsorption energy of H,so that more electrolyte ions are embedded in the material and participate electrochemical reaction,thereby increasing the specific capacitance;and the embedding of potassium ions will reduce the band gap of cobalt hydroxide and improve its conductivity,thereby promoting the transfer of charge,and improving the specific capacitance and rate performance.Dual ion-embedded samples are optimized in both ways,resulting in higher electrochemical performance.?2?Optimization of the performance of double ion-embedded cobalt hydroxide.The amount of active material on the electrode was adjusted by changing the electrodeposition time.When the electrodeposition time is 25 minutes and the mass is about 5 mg,the electrode has a high area capacitance.The areal capacitance can reach3.21 F cm^-2 as the current density is 5 mA cm^-2.After it is assembled with the electrochemically acidified carbon cloth to form a capacitor device,the energy density can still reach 39.8 W h kg^-1 at a power density of 478.6 W kg^-1,which has certain application value.?3?Study on the electrochemical performance of double ion-embedded hydroxides with different cobalt-nickel ratios.The hydroxides with different cobalt-nickel ratios and chloride and potassium ions co-embedded were prepared for characterization and analysis.When nickel ions are dominant in the material,the crystallinity of the active material is poor and it is easy to form a uniform film on the substrate,and the relative electrochemical behavior shows a clear battery type.When cobalt ions dominate,the active material shows the higher crystallization,thus forms vertical nanosheets on the substrate,and the electrochemical behavior is more capacitive.When the cobalt-nickel ratio is 1:3,the electrode has the best electrochemical performance.The specific capacitance can reach 1405.9 F g^-1 as the current density is 2 A g^-1,and the capacitance retention rate can still reach 79.7%under the high current of 50 A g^-1,which has broad application prospects.In summary,the structure optimization of cobalt-nickel-based hydroxides through double ion intercalation,and the adjustment of the atomic ratio of cobalt-nickel can effectively improve the electrochemical performance of such materials,and played an important role in enhancing the energy density of supercapacitors,and expanding its application fields.