Fabrication And Energy Storage Characteristics Of Flexible Nanoporous Ni/NiO Composite Electrodes

With the rapid development of super-capacitors,nanoporous metal as a new type of super-capacitors electrode materials has become a hot research topic.However,most of the nanoporous metals are brittle,easy to break,and can not maintain mechanical integrity in a state of high curvature.In the present thesis,we report an integrated nanoporous nickel/nickel oxide（np-Ni/NiO）composite electrode materials synthesized by chemical dealloying the ductile Ni-based metallic glasses（MGs）ribbon coupled with natural oxidation.The inner amorphous layer of the ductile Ni-based metallic glasses was retained by controlling the dealloying depth.And then a sandwich structured（NiO/np-Ni|MGs|np-Ni/NiO）electrode with excellent flexibility was fabricated by this method.In the work,the Ni₄₀Zr₆₀0 amorphous ribbon was firstly selected as dealloying precursors to fabricate the np-Ni/NiO composite electrode in HF etching solution.The effects of the concentration of HF etching solution and the dealloying time on the morphology,the overall structure,the flexibility and the energy storage characteristics of the electrode were investigated.Based on the above research,a portion of Zr element in Ni₄₀Zr₆₀ precursors was replaced by Ti element.The effects of the content of Ti element in precursors on the surface morphology,structure and flexibility of the electrode were further investigated.After dealloying in 0.05 M HF solution,it can be observed that a large number of star-shaped cracks were uniformly distributed on the as-dealloyed Ni₄₀Zr₆₀0 ribbon surface.When the 50%Zr element in as-spun Ni₄₀Zr₆₀ ribbon was replaced by Ti element,star-shaped cracks disappeared and uniform nanoporous structure was formed on the as-dealloyed Ni₄₀Zr₃₀Ti₃₀0 ribbon.When the Zr element in as-spun Ni₄₀Zr₆₀ ribbon was completely replaced by Ti element,the corresponding as-dealloyed Ni₄₀Ti₆₀0 ribbon showed a very compact surface structure.According to the atomic percentage of the Ti elements in the precursors,the electrodes prepared by the three kinds of precursors were recorded as"electrode T-0","T-30"and"electrode T-60",respectively.All the three kinds of electrodes showed the ability of bending deformation.But in the finger pressing test,the electrode T-0was broken,while the electrode T-30 and electrode T-60 did not crush.The results showed that the surface morphology and flexibility of the electrodes can be improved effectively by adding Ti in as-spun ribbons.At a discharge current density of 1 A/cm³（considering the overall volume of the electrode）,the maximum volumetric capacitance of electrode T-0,T-30 and T-60 was 730 F/cm³,806 F/cm³ and 177 F/cm³,respectively.With the increase of discharge current density from 1 to 128 A/cm³,the volumetric capacitance of electrode T-0,T-30 and T-60 decreased by 65.7%,19.7%,and 17.3%,respectively.The results show that the uniform and loose porous structure on the surface of electrode T-30 is beneficial to the improvement of the energy storage capacity and rate performance.