| With the rise of wearable electronic devices,flexible lightweight energy storage devices are attracting more and more attention from scholars at home and abroad.Among them,flexible supercapacitors have become one of the main research hotspots due to their advantages of fast charge and discharge,long cycle life and good temperature adaptability.However,flexible supercapacitors still have problems such as poor electrochemical performance,poor mechanical flexibility and high cost,which limit their wide application.Electrode materials are the main factors determining the performance of capacitors,thus improving the electrochemical performance of electrode materials and improving their mechanical properties.Performance and reduction of manufacturing costs have become an urgent problem to be solved in the industrialization of flexible energy storage devices.In this paper,a wide range of cotton fabrics(CF)are used as flexible substrates.The top-down assembly method is used to deposit metal Ni particles on the surface of the substrate by palladium-free electroless plating,and then electrochemically polarization method in Ni.Ni(OH)2having a nano-sheet structure is formed in situ on the surface of the particle to form a core-shell structure Ni@Ni(OH)2 composite.Firstly,the effects of different electroless plating conditions on the capacitance properties of fabric-based composite electrodes were investigated.Secondly,the influence of the number of cycles on the morphology of Ni(OH)2 nanosheets during subsequent electrochemical oxidation polarization was studied.The results show that the fabric-based electrode material(Ni@Ni(OH)2/CF)with excellent electrochemical performance can be obtained under optimized preparation conditions,and its area specific capacitance at a current density of 5m A/cm2 is 5.17 F/cm2,the capacitance retention rate is 72%at a current density of 25 m A/cm2,and the capacitance retention rate is 89.5%at 1500 times cycles at a current density of 30 m A/cm2.At the same time,the electrode material has good flexibility and tensile strength,and the response current under bending conditions remains basically unchanged.Under the weight of 504 g,the material remains in its original shape without fracture.The copper salt(Cu SO4)was added into the electroless Ni plating solution to further explore the application prospects of this method in the preparation of flexible electrodes.The effect of copper ions on the co-deposition of copper-nickel metal on the fabric surface was explored.And the copper salt concentration on the electrochemical polarization process and the effect of the fabric-based composite electrode(Ni/Cu@Ni(OH)2/Cu(OH)2/CF)capacitance performance were discussed.The results show that with the increase of copper sulfate concentration in the electroless plating bath,the conductivity of the composite electrode is improved and the metal hydroxide size in the composite is larger and the structure is more stable.When the concentration of copper sulfate in electroless plating is 5 g/L,the electrode exhibits good electrochemical performance;the area specific capacitance is 22.4 F/cm2 at a current density of 5 m A/cm2,the capacitance retention is 82.3%at a current density of 30 m A/cm2 and the capacitance retention rate was 86.7%after2000 times cycles at 30 m A/cm2.Two kinds of fabric-based composite electrodes(Ni@Ni(OH)2/CF and Ni/Cu@Ni(OH)2/Cu(OH)2/CF)were prepared as positive electrodes,and activated carbon cloth(ACC)was used as negative electrode.2M KOH is the electrolyte and the cellulose membrane is the separator.Two flexible asymmetric supercapacitors(Ni@Ni(OH)2/CF//ACC and Ni/Cu@Ni(OH)2/Cu(OH)2/CF//ACC)have been successfully assembled,and their electrochemical performance have been tested and compared with each other.The results show that the power density of Ni@Ni(OH)2/C//ACC is 3.75 m W/cm2?18.75 m W/cm2,and the energy density is 0.45 m Wh/cm2?0.59 m Wh/cm2;The power density of Ni/Cu@Ni(OH)2/Cu(OH)2/CF//ACC is 3.6 m W/cm2?21.6 m W/cm2,and the energy density reaches 1.04 m Wh/cm2?1.31 m Wh/cm2;and Compared with the Ni@Ni(OH)2/CF electrode system,the electrochemical performance of the Ni/Cu@Ni(OH)2/Cu(OH)2/CF electrode system has been greatly improved.Both of them can light the LED diode under bending conditions,indicating that it has a good application prospect in flexible energy storage products. |
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