Structure Regulation Of NiCo-LDH And Its Supercapacitor Performance

With the continuous change of the current world situation and the rapid development of science and technology,the problems of environmental pollution and the shortage of fossil energy have also followed.Therefore,there is an urgent need to find environmental-friendly and efficient energy storage equipment.Supercapacitors are among the most popular energy storage devices due to their high power density,property of pollution free and short charging time.However,the low energy density of supercapacitors limits their practical application.Layered double hydroxides（LDHs）are promising materials for energy storage and energy conversion.Due to its large interlayer spacing and thin layer structure,ions can be freely transferred between layers,which increasing the specific surface area.In particular,NiCo-LDH shows high theoretical capacity.However,the application of NiCo-LDH is limited by low conductivity and irreversible phase transitions,which not only reduces its magnification performance,but also limits its cyclic stability.Therefore,in this paper,NiCo-LDH is designed reasonably and applied to the positive electrode of high-performance supercapacitor to further improve its electrochemical performance.The main contents are as follows:First,ZIF-67 nano sheets array vertically arranged on foam nickel were obtained by simple coprecipitation,and then used as the precursor.Finally,it was ingeniously converted into nickel cobalt layered double hydroxide（NiCo-LDH@NF）by solvothermal method.The core-shell structure formed by designing the morphology of the target product provides favorable conditions for charge transfer,thereby improving the kinetics of oxidation and reduction.And by adding different mass of Ni（NO₃）₂·6H₂O to change the concentration of Ni²⁺,NiCo-LDH@NF with core-shell structure was obtained.The ion and electron transport of NiCo-LDH@NF composite electrode material has been improved,so that it shows a high specific capacity of 1378.7 F g^-1at a current density of 1 A g^-1.Moreover,even at the current density of 10 A g^-1,the capacitance retention rate is 63.4%.Through treatment with NaBH₄NiCo-LDH@NF,the ratio of oxygen vacancies in the original LDH was improved.Oxygen vacancy can provide more electroactive sites and electron or ion transfer pathways for redox reaction,effectively improve its conductivity,and also enable OV-LDH@NF to obtain higher capacity.The prepared OV-LDH@NF electrode obtained an effective increase in specific capacity(1497.7 F g^-1at a current density of 1 A g^-1)and better a better rate capacity(82.66%retention at 10 A g^-1).Compared with NiCo-LDH@NF synthesized in the best proportion,the electrochemical performance of OV-LDH@NF has been effectively improved.In this paper,ZIF-67 was in-situ grown on foam nickel by a simple method,and a NiCo-LDH nanosheet structure with oxygen rich vacancies was synthesized and designed using ZIF-67 as the precursor.The electrode material has the following characteristics:the material grows directly on the substrate without adding organic binder,and the oxygen vacancies can accelerate the electron transport,thus further improving the conductivity and electrochemical performance.This study reports a high-performance LDHs electrode rich in oxygen vacancies,which provides a new idea for the development of electrode materials for supercapacitors.