Anodization Preparation And Electrochemical Performance Studies On Superior Rate Capability Nickel-based Composite Film Electrode

Supercapacitors are characterized with some excellent properties, such as high power density,high energy density,long cycle life,fast charge and discharge,no pollution, et al.That have been applied in the following fields, such as, energy, chemical industry,electronics,military, et al. Metal oxides are becoming attreacted because of their capacitance,energy density and power density higher than carbon and conductive polymer supercapacitor.Among different metal oxide materials for supercapacitors,hydrous ruthenium oxide（Ru O2）shows a high specific capacitance and excellent cycle-life stability, which has been successfully applied in the aerospace and military equipment. However,the abundance and high cost, besides being toxic have limited the utilization of ruthenium oxide in bulk commercial applications. Therefore, great efforts have been taken to develop low cost-effective alternative materials with good pseudo-capacitive performan close to that of Ru O2 based materials. Based on the reviews on preparation processings of nickel oxide /nickel hydroxide electrode materials,anodization was developed to prepare nickel-based film electrodes with superior rate capability. The main contents are shown as followings:A two-electrode anodization method was introduced to preparea nickel-based supercapacitor film electrode in different solutions. With XRD,SEM,XPS,BET and BJH,surface morphologies,chemical states,crystal structures,pore and surface areas of the film were studied. Electrochemical performances of the nickel-based film were tested using an electrochemical workstation and a battery program-control test system. To further improve the electrochemical performances of nickel-based film electrode, two post-treatment methods,galvanostatic charge / discharge（GCD） or hydrothermal treatment, were developed.The two-electrode anodization method could be applied to successfully prepare the nickel-based film electrode in a NH4 F and H3PO4-containing electrolyte. The niekcl-based film electrode has showed significant capacitive characteristics and the first specific capacitor reached 505 m F / cm²,but its life cycle was unstability. Thus, two different post-processingmethods, GCD and hydrothermal treatment,were developed to improve the cycle life of the nickel-based anodic film.After being treated by the GCD treatment method, the film showed a nanoflower-like morphlogy and consisted of Ni O,a-Ni（OH）2and b-Ni（OH）2. This compounds showing a high specific capacitance, superior rate capability and good cyclability（1505 F/g at 6.7 A/g,1120F/g at 66.7 A/g, after 2000 cycles,the capacitance of the film kept unchanged.）And,after being treated by the hydrothermal method,the anodic film on the nickel foil was converted to a Ni（OH）2-Ni O-Ni F composite coating.No crack was found in the resultant coating. This coating consisted of nano-plate crystals with porous morphology,and exhibited a high specific capacitance（1984F/g at 10A/g）,the highly capability and a good cycling stability（capacitance close to 1680F/g at 100A/g after 2000 cycles）.Additionally,a Cs Cl and H₂SO₂ soltuion was used as an electrolyte. And a Ni（OH）2-Ni O composite coating was successfully fabricated on a nickel foil by the two-electrode anodization method. This coating consisted exhibited a good cycling stability（capacitance from 332 m F/cm² increases to 564 m F/cm² after 100000 cycles） and superior rate capability（80 m A/cm² at 100 m A/cm²,600 m F/cm² at 490 m F/cm²,after 10000 cycles,the capacitance of the film kept unchanged.）...