Preparation Of Nickel Base Layered Double Hydroxides And Its Application In Supercapacitor

Supercapacitors represent a promising new generation of energy storage devices,uniquely characterized by their high power density,long cycle life,and energy density in comparison to traditional capacitors and lithium batteries.The potential for these devices to serve as clean energy storage solutions has positioned them as the subject of significant research in the field.This paper will focus on the Nibase bimetallic hydroxide as a research object,with a specific emphasis on its potential for application in supercapacitors.This exploration will be approached through three primary research directions:heterogeneous element doping,hollow nanostructure construction,and metal-organic framework template derivation.Throughout this research,we will seek to optimize the capacity of supercapacitors and explore ways to enhance their charge storage mechanisms by examining morphology and crystal structure.The following sections will provide a detailed analysis of the key contents and innovations of our work:1.Three kinds of LDHs nanoflower-like electrode materials with different Co content,Ni₂Co₁Al₁-LDH,Ni_1.5Co_1.5Al₁-LDH and Ni₁Co₂Al₁-LDH,were synthesized by hydrothermal method.The influence of different contents of Co on the electrical conductivity and valence state of Ni-based hydrotalcite was studied.The experimental results show that the Ni/Co ratio has no significant effect on the crystal structure,morphology,specific surface area and pore size distribution.However,the introduction of more Co elements can significantly increase the Ni³⁺/Ni²⁺ratio and oxygen vacancy concentration,thus achieving the purpose of improving the capacitive performance of the material.Ni₁Co₂Al₁-LDH showed the highest conductivity,Ni³⁺content and oxygen vacancy concentration,and the specific capacitance was 728 C g^-1 when the current density was 1 A g^-1,and the capacitance retention rate was 92.18%after 10000cycles.This work reveals the synergistic interaction of Niand Co elements in LDHs,and provides some insights into the doping strategies of heterogeneous elements.2.NiCo-LDHs nanoboxes with hollow structure were synthesized by ion displacement reaction using Cu₂O as template.This hollow structure can provide more active sites for charge storage,and XPS test results show that it has reasonable valence distribution of metal elements.When the current density was 1 A g^-1,the electrode capacity of NiCo-LDHs hollow nanoboxes reached 817 C g^-1,showing higher electrochemical performance than that of Work 1.When the asymmetric capacitor is assembled with NiCo-LDH nanoboxes and activated carbon electrodes,the capacity reaches 129.3 F g^-1 when the current density is 1 A g^-1,and the capacity retention rate remains at 92.52%after 10000 cycles at 20 A g^-1.This work demonstrates the advantages of hollow nanostructures for the preparation of NiCo-LDH electrode materials.3.In this work,we deposited ZIF-67 nanosheet arrays on nickel foam and transformed the ZIF-67 nanosheet arrays into Ni/Co/Fe-LDH@NF based nanosheet arrays with different elements with different precursor solutions.The results of electrochemical test show that the three-component NiCo Fe-LDH@NF nanosheet array has the lowest surface electrode charge transfer resistance and the most abundant electrochemically active sites through the synergistic interaction between nickel,cobalt and iron.NiCo Fe-LDH@NF nanoarray not only obtains high specific area capacitance up to 951 m C cm^-2 at current density of 1 A g^-1,but also has OER overpotential of only 270 m V and tafel slope of only 47 m V dec^-1 at polarization current density of 50 m A cm^-2.After the current density of 50 m A cm^-2 constant current stability test,the overpotential remained unchanged for 72 h.This work provides an idea for the development of high performance layered bimetallic hydroxide electrode materials using the metal-organic framework template method.