| Owing to the rapid development of modern technology,wearable/portable intelligent electronic devices have gradually entered people's vision and changed their daily life.The requirements for the intelligent portable electronic devices,such as compact,wearable,foldable,and flexible,become higher.Therefore,the demands of light,thin,soft and so on for energy storage devices in electronic products have been proposed.Among plenty of energy storage devices,supercapacitors,especially flexible all-solid supercapacitors,draw researchers'attention,which attribute to their remarkable electrochemical performance,such as fast charge and discharge,outstanding power density,superior circular life,safety and environmental friendly,and superior mechanical properties(maintain their electrochemical performance in any deformation condition)and wide operating temperature range.Electrode materials play a crucial role in supercapacitors,which related to energy storage and multiple functions in flexible and wearable devices.These days,more and more attentions are focused on copper and nickel-based transition metal(hydrogen)oxides as electrode materials for supercapacitors because of their unique physical and chemical properties.However,the poor rate performance and cycle performance still hinder the wide utilization of copper and nickel-based transition metal(hydrogen)oxide materials.In light of these problems,to develop high electrochemical performance supercapacitors while possess flexibility is still a huge challenge.Based on the above considerations,the main research contents of this paper are as follows:Cu(OH)2/Cu/CC electrode was prepared through the quasi-steady-state electroless plating technique to construct a copper coating on carbon cloth(CC),and then Cu(OH)2 nanowires were grown on the copper coating in situ by alkali-assisted oxidation.SEM and TEM exhibit that Cu(OH)2 presents a three-dimensional network nanowire structure.The electrochemical performance test results of the three-electrode system shows that the Cu(OH)2/Cu/CC electrode have excellent cyclic stability(after 5000 cycles of cyclic stability test,the capacitance retention rate of the electrode material was 90.8%).The related electrochemical tests show that the energy density of the Cu(OH)2//AC flexible supercapacitors is 16.2 Wh·kg-1when its power density is603.1 W·kg-1.In addition,the Cu(OH)2/Cu/CC//AC/CC device shows good flexibility,and excellent cycle stability.In order to improve the specific capacitance of Cu(OH)2,CuCo2O4/CC was prepared by constructing porous CuCo2O4 nanosheets on the flexible carbon cloth substrate via hydrothermal method and annealing treatment.Compare with Cu(OH)2 materials,CuCo2O4material has more multiple oxidation states which ascribe to the advantage of the combination of Cu and Co.The high electrochemical activity of CuCo2O4 material endows the prepared CuCo2O4/CC electrode better capacitance performance.SEM and TEM shows that CuCo2O4presents a two-dimensional porous nanosheet structure,which is conducive to electrolyte infiltration and increases the active site of electrochemical reaction.The electrochemical performance test results of the three-electrode system for the CuCo2O4 flexible electrode with porous nanosheets structure shows a specific capacitance of 697.2 F·g-1.The electrochemical performance test results of the two electrodes shows that the flexible all-solid-state asymmetric supercapacitor assembled with the prepared CuCo2O4/CC as the positive electrode achives a specific capacitance of 95.6 F·g-1 when the current density is 1 A·g-1.In addintion,the maximum energy density of the CuCo2O4//AC achieves 34 Wh·kg-1,when the power density of the device is 800.6 W·kg-1,indicating good flexibility and cycle stability.To further to improve the specific capacitance and cycle stability of CuCo2O4material,hollow-porous CuCo2O4 nanosheets were prepared on carbon cloth by etching,ion exchange and annealing using the metal-organic framework compound Co-ZIF as a template(CuCo2O4/CC).A superior specific capacitance(847 F·g-1 at the current density 1 A·g-1)and cyclic stability(after 5000 GCD tests,the capacitance retention rate was up to 93.1%)of the CuCo2O4/CC electrode are proved via the electrochemical test in the three-electrode system.In addition,the electrochemical test of the assembled CuCo2O4/AC flexible supercapacitors in the two-electrode system exhibits that when the power density is as high as 750 W·kg-1,a high energy density of 39.6 Wh·kg-1 is achieved.To investigate the effect of heterostructure on electrochemical performance of electrode,CuCo2O4 nanosheets with high crystallinity were hydrothermal synthesized on carbon cloth,and then Ni(OH)2 were grown on the surface of CuCo2O4 nanosheets to prepare the heterostructured CuCo2O4@Ni(OH)2 binderless flexible electrode(CuCo2O4@Ni(OH)2/CC).SEM,TEM and XRD shows that the CuCo2O4@Ni(OH)2 heterostructure nanosheets are successfully constructed on the carbon cloth.The electrochemical test of the CuCo2O4@Ni(OH)2/CC electrode in the three-electrode system shows that the CuCo2O4@Ni(OH)2/CC electrode exhibits superior specific capacitance(2271 F·g-1)when the current density is 1 A·g-1,rate performance(82.7%)and relatively good cyclic stability(after5000 consecutive GCD tests,the capacitance retention rate can still reach 92%).The electrochemical test of the flexible supercapacitors assembled with CuCo2O4@Ni(OH)2 as the positive electrode in the two-electrode system shows that the CuCo2O4@Ni(OH)2//AC has a good power density,energy density,and flexibility.A heterogeneous structured Ni Mo O4@PPy was constructed on the flexible carbon cloth by hydrothermal method,annealing treatment and chemical oxidative polymerization method.SEM,TEM,XRD,and ATR-FTIR show that Ni Mo O4@PPy heterostructure nanowires are successfully constructed on CC.The results of the N2 adsorption and desorption test show that the heterogeneous structures increase the specific surface area of the Ni Mo O4@PPy/CC electrode material(33.6 m2·g-1),when compare to the Ni Mo O4/CC(25.9 m2·g-1).The electrochemical test of the prepared electrode in the three-electrode system shows that the specific capacitance of Ni Mo O4@PPy/CC electrode achieves 1788 F·g-1,and its capacitance retention rate is 94%after 5000 cycles GCD test,much higher than those of Ni Mo O4/CC.The electrochemical test of the assembled flexible all-solid asymmetric supercapacitor in the two-electrode system shows that the Ni Mo O4@PPy//AC has a high energy density of 43.7 Wh·kg-1when the power density is 739.1 W·kg-1.In addition,under different deformation conditions,the shape of CV curve does not change significantly,indicating that the device has good flexibility. |
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