Preparation And Capacitor Performance Of Cobalt-based Multimetal-compound Integrated Electrodes

In recent years,as an important type of energy storage device,supercapacitors have been widely used in various power sources,such as electronic equipment,electric vehicles,and smart grids.Hybrid capacitors are constructed from pseudocapacitive materials（positive electrodes）and capacitive materials（negative electrodes）.Constructing a hybrid capacitor can increase the overall potential window and at the same time increase the energy density.Pseudocapacitive electrode materials generally have poor electrical conductivity and poor cycle stability.The deficiencies of these electrode materials can be effectively solved by means of interface control and doping.In this paper,four metal compound-based integrated electrodes are grown on foam nickel（NF）by hydrothermal and electrodeposition for use in supercapacitors,and their structure and electrochemical properties have been systematically studied.（1）The integrated electrode of NF/NiMoO₄/CoMoO₄ was prepared by hydrothermal method and subsequent annealing.Because NiMoO₄ nanosheets and a suitable amount of CoMoO₄nanoneedles are staggered and grown vertically on the surface of the nickel foam,the stability of the electrode is effectively improved.The NF/NiMoO₄/CoMoO₄ electrode can maintain 80.1%capacity after 10,000 cycles at 10 A/g.After being assembled into a hybrid capacitor,it exhibited an energy density of 55.71 Wh/kg at a power density of 375 W/kg.（2）The NF/NiCo₂O₄/ZnCo₂O₄ composite integrated electrode was prepared by the subsequent annealing operation after the hydrothermal method.Due to the reasonable combination of the three elements Ni,Co,and Zn,a nanoneedle structure is presented.The electrode has achieved a high specific capacity of 1027 F/g at 1 A/g.After increasing the current density by 20 times,the electrode is still Can maintain 88.8%of the initial capacity.At the same time,since the electrode structure can be oriented and re-formed into a triangular pyramid shape during the recycling process,it exhibits more active sites.It can still maintain 177.11%of the initial capacity after 10,000 cycles at a current density of 10 A/g.（3）The NF/MgCo₂O₄-OV oxygen vacancy electrode was prepared by hydrothermal method and subsequent annealing operation.Due to the existence of oxygen vacancies,the NF/MgCo₂O₄-OV electrode exhibits a higher specific capacity and good conductivity,reaching a specific capacity of 1928.6 F/g at 1 A/g.At the same time,the structure of the MgCo₂O₄nanoneedle structure changed during the process of preparing oxygen vacancies.After 10,000cycles at 10 A/g,the NF/MgCo₂O₄-OV electrode maintained 115%of the initial capacity.After20,000 cycles at 20 A/g,the NF/MgCo₂O₄-OV electrode maintained 98%of the initial capacity.（4）Mn-doped NF/NiCo-LDH nanosheet material was synthesized on NF by means of electrodeposition.Due to the good doping of Mn,the NF/NiCo-LDH electrode exhibits good conductivity and rate performance.At 1 A/g,Mn-doped NF/NiCo-LDH has a specific capacity of 1261.2 F/g.After increasing the current density by 20 times,it can still maintain 92.9%of the initial capacity.After being converted into a hybrid capacitor,it has excellent energy density（31.4 Wh/kg）and good cycle stability（capacity retention rate after 5000 cycles is 82.7%）.