Co-MOF Derivative Array For Flexible And High Performance Supercapacitors

In recent years,with the implementation of the Paris Agreement,China has introduced various policies to vigorously develop wind energy,solar energy and other non-fossil energy,while reducing the proportion of fossil energy consumption.However,non-fossil energy such as wind energy,solar energy and geothermal energy are often storaged into electric energy and stored,so the research of energy storage devices has become the focus of researchers.Moreover,people's material needs also put forward higher requirements for energy storage devices.Therefore,the research and development of large capacity,long life,safety,environmental protection and cheap electric energy storage equipment is very important.In the meantime,traditional energy storage equipment,such as lead-acid batteries,cannot meet the further development of new energy vehicles and portable electronic devices.Supercapacitors,as a new type of energy storage equipment,have attracted extensive attention from researchers due to their characteristics such as high power density,long cycle life,good rate performance and safety and environmental protection.However,so far,supercapacitors on the market are mainly made of carbon materials,which have limited application scope due to low energy density and other reasons.Therefore,supercapacitors with high energy density need to be studied.Nanoarrays derived from metal-organic frameworks(MOFs)have been widely used in energy storage electrode materials due to their unique morphology and large specific surface area.Here,this paper mainly starts from the two-dimensional Co-MOF nanoarray materials,through carbonization or vulcanization treatment,effectively improve the electrical conductivity of the system.With high capacity NiMn hydrotalcite,the energy density of the electrode is maximized.The specific research contents are as follows:(1)Co-MOF nanosheet array precursors were synthesized on a flexible carbon substrate by co-precipitation method.After carbonization by annealing in Ar atmosphere,CoO and N doped carbon nanosheet arrays(CNS)were formed.Then NiMn hydrotalcites were grown in salt solution of Ni and Mn by hydrothermal method to obtain CNS@NiMn-LDH electrode.In addition,in order to explore the general applicability of the CNS support framework,the CNS@Fe2O3 electrode was obtained by electrochemical deposition of FeOOH on the CNS and annealed in Ar atmosphere.In the three-electrode alkaline test system,the CNS@NiMn-LDH electrode material has an area specific capacity of up to 1.851 C cm-2.There is A high gram capacity of 751 C g-1 at current density of 1 A g-1 and retains 82%of the initial capacity after more than 2300 cycles.Through comparative analysis,it is concluded that the CNS@NiMn-LDH electrode has better electrochemical performance due to its larger specific surface area,better electrical conductivity and unique nanostructure.Finally,the asymmetric supercapacitor made by matching the CNS@NiMn-LDH positive electrode with the CNS@Fe2O3 negative electrode shows higher power density and energy density.(2)Co-MOF nanosheet array precursors were also grown in situ on a flexible carbon cloth substrate,and cobalt sulfide(Co-S)nanosheet arrays were obtained by hydrothermal sulfurization.NiMn hydrotalcite was then hydrothermal grown to obtain amorphous hollow nickel sulfide(Ni-S)and NiMn hydrotalcite to form Ni-S@NiMn-LDH core-shell electrode.Different from the previous work,both Ni-S and NiMn-LDH in our Ni-S@NiMn-LDH core-shell electrode participate in the capacity contribution,and there may be a synergistic effect.This not only increases the area specific capacitance.In addition,the Ni-S@NiMn-LDH core-shell electrode showed higher power density,higher energy density and better magnification performance in the electrochemical test because both the core and the shell participated in the reaction.The cyclic stability of the electrode is relatively poor due to the large deformation in the process of charge and discharge,which needs further study.