Preparation And Performance Study Of Multi-element Nanoporous Metal/oxide Composite Electrode

The increasing environmental pollution and shortage of fossil energy have become two hot issues in current society,developing new energy sources is one of the reliable ways to solve above problems.Supercapacitors and lithium-ion batteries as energy storage devices have attracted much attention.Electrodes are the keys to determine the energy storage performance of supercapacitors and lithium-ion batteries.Among various electrode materials,transition metal oxide becomes an ideal choice for electrode materials due to their advantages of abundant reserves,low price and high theoretical capacity.However,the intrinsic poor conductivity and low rate capacity limits their energy storage performance.For this problem,designing of nanoporous alloy and oxidizing the porous alloy with different elements doped in NiMn alloy was used to prepare the ternary NiVMn,NiMoMn and quaternary NiMoFeMn composite electrodes,which maintained good electrical conductivity,as well as obtaining high specific capacitance and high rate capacity.The research work in this paper is as follows:(1)According to the phase diagram,the ternary(Ni,V,Mn)and quaternary(Ni,Mo,Fe,Mn)alloy systems with different elements content were chosen to prepare the different alloys through the melt-belt method.The nanoporous precursors with different pore size were prepared by dealloying.(2)A layer of amorphous metal oxide/hydroxide was grown on the surface of the alloy by polarization or heat-treatment method.XPS test shows that the surface of the electrode presents different elemental valence,and the specific capacitance of the electrode material could be greatly increased by multivalent metal oxide and hydroxide.The TEM result indicates the core-shell structure of the electrode,where the amorphous oxy-hydroxides grown on the nanoporous metal guarantees the high specific capacitance.Meanwhile,it also not only maintains high electronic conductivity,but also keeps the bicontinuous structural of the alloy.Compared to other metal oxide electrodes,it shows remarkable advantages in pseudocapacitive electrodes.(3)In this work,the effects of doped elements,element proportion,electrolyte type and concentration,polarization voltage and other factors on the electrochemical properties were studied.As a result,polarizing the ternary Ni25V15Mn60 alloy at 0.6 to 0.9V for 3minute,the electrode possesses the highest specific capacitance in 0.5 M KOH+0.5 M Na2SO4 electrolyte.Remarkably,the specific capacitance can reach up to 1053F/cm3 at current density of 1A/cm3.Even cycling for 3000 cycles,the capacitance is almost not decay,which indicates good cyclic stability.For the Ni20V10Mn70 derived nanoporous electrode,in the same electrolyte,it can keep high rate capacity of 81.2%when current density increased from 1A/cm3 to 10 A/cm3.Clearly,the ultra-high rate capacity shows competitive advantages than other metal oxide electrodes.(4)Herein,we also heat-treated the dealloyed nanoporous NiVMn alloy in air to prepare a novel nanoporous alloy@oxides for Li-ion battery anode.With traditional coating method of active material adhered onto copper foil,we assemble a half battery to research its property,where the Li foil working as counter electrode.After a preliminarily investigation,as a result,the electrode shows great potential in promoting the rate capacity and cyclic stability of nanoporous transition metal oxides.