Controllable Preparation Of Copper Cobaltite Electrode Materials For High-performance Supercapacitors

The requirement for storage technologies is increasingly urgent for the prosperity of renewable energy.For the advantages of high power density,stability,long cycle life,and low-cost,supercapacitors have a promising future in various situations.Though,limited applications have been found for low energy density in the commercial field.Battery-type electrode materials could improve the energy density of supercapacitors reserving high power density.As a type of battery-type material,CuCo₂O₄ is a promising alternative in high-performance supercapacitors with the advantages of low-cost,low-toxic,high theoretical capacity,etc.For the aim of controllable synthesis of CuCo₂O₄with high electrochemical performance,the research has been made and described as follows.（1）CuCo₂O₄ nanowires（CuCo₂O₄-NWs）and CuCo₂O₄ nanosheets（CuCo₂O₄-NSs）were synthesized through the hydrothermal method on stainless steel foil with high uniformity.The powered CuCo₂O₄ was peeled off from stainless steel foil and the prepared electrodes exhibited superior electrochemical performance.CuCo₂O₄-NWs exhibited a specific capacity of 299.12 C g^-1 at a current density of 1 A g^-1,along with a rate performance of 75.62%at 10A g^-1.A specific capacity of 332.18 C g^-1 and a rate performance of 78.46%for CuCo₂O₄-NSs were obtained under the corresponding current density.Moreover,the hybrid supercapacitor（HSC）was assembled employing powered CuCo₂O₄ as the cathode and activated carbon（AC）as the anode.At the current density of 1 A g^-1,CuCo₂O₄-NWs//AC HSC reached a specific capacity of 129.46 C g^-1（0-1.75 V）and a higher specific capacity of 134.52 C g^-1 for CuCo₂O₄-NSs//AC HSC.Besides,both HSCs exhibited an excellent cycling durability.After5000 cycles,the capacity retentions of two HSCs were 104.09%and 104.25%,respectively.Moreover,CuCo₂O₄-NWs//AC HSC possessed an energy density of 36.16 W h kg^-1 at 1.01k W kg^-1,while CuCo₂O₄-NSs//AC HSC possessed a higher energy density of 38.46 W h kg^-1at 1.03 k W kg^-1.（2）CuCo₂O₄/CuO hollow microspheres（CuCo₂O₄/CuO MSs）were prepared through the solvothermal method as the mixed solvent consisting of glycerol,isopropanol,and de-ionized water.CuCo₂O₄/CuO nanosheets（CuCo₂O₄/CuO NSs）were synthesized through a combination of the solvothermal and hydrothermal methods.CuCo₂O₄/CuO MSs reached a specific capacity of 284.5 C g^-1 at 1 A g^-1 and 217.0 C g^-1 at 10 A g^-1.In contrast,CuCo₂O₄/CuO NSs reached a specific capacity of 337.6 C g^-1 and 258.6 C g^-1 at the corresponding current density.The assembled HSC employed AC as the anode and CuCo₂O₄/CuO as the cathode.Besides,CuCo₂O₄/CuO MSs//AC HSC reached a specific capacity of 112.8 C g^-1（0-1.7 V）,while CuCo₂O₄/CuO NSs//AC HSC exhibited a higher specific capacity of 145.1 C g^-1.Both HSCs showed impressive cycling stability over 3000cycles,and 4.8%as well as 3.1%capacity loss were found after cycling,respectively.In addition,CuCo₂O₄/CuO MSs//AC HSC possessed an energy density of 28.7 W h kg^-1 under0.9 k W kg^-1,while CuCo₂O₄/CuO NSs//AC HSC possessed a higher energy density of 38.8 W h kg^-1 under 1.0 k W kg^-1.