Study On Electrolytic Capacitor Anode Based On TiN Nanowires And Nanotubes

Electrolytic capacitors are used widely for they have the advantages of high power density(10⁷ W kg^-1)and high cycle life compared with batteries and supercapacitors.However,the application range is limited due to its low energy density.The purpose of this article is to construct nanostructured electrodes to increase the capacitance and energy density of electrolytic capacitors.This work focuses on the preparation of TiN nanotubes and nanowires anode.The specific content is as follows:The TiO₂ dielectric film on planar TiN was obtained by anodizing TiN in aqueous solution of 5 wt%of NH₄B₅O₈ and 1 wt%H₃BO₃.It was found that the higher of the oxidation temperature,the more anion embedding on the surface layer of the prepared TiO₂dielectric film when the oxidation temperature was higher than 10°C.The CU value of the prepared TiO₂ dielectric film is slightly increased while the tan?and leakage current are increased greatly,which is not conducive to the preparation of dielectric films.When the anodizing temperature is 10°C,the CU value of the prepared TiO₂ dielectric film decreases with the increase of voltage while the tan?and leakage current increase with the voltage.The performance of TiO₂ dielectric film with 10 V oxidation voltage is the best,whose CU value is60.1?F V cm^-2,tan?is 0.72,and leakage current is 0.29?A?F^-1 V^-1.The TiO₂ was converted into Ba TiO₃ dielectric film by hydrothermal method.The longer the hydrothermal time,the larger the CU value,the smaller the tan?and the leakage current.The CU value is 90.0?F V cm^-2,energy density is 0.45 m J cm^-2,tan?is 0.37 and leakage current is 0.23?A?F^-1 V^-1 when the TiO₂ dielectric film was completely converted to Ba TiO₃ dielectric film after 6 h hydrothermal.The TiO₂ nanowire array was prepared by hydrothermal method.The hydrothermal time and Na OH concentration were investigated on how to affect the morphology of the prepared nanowires.It was found that the length of the prepared nanowires increases with the hydrothermal reaction time and the Na OH concentration.The nanowires would collapse when the hydrothermal time or the Na OH concentration exceed a limit value.The nanowire array with the largest specific surface area is obtained when the hydrothermal time is 6 h and the Na OH solution concentration is 6 mol L^-1.The TiN nanowires are obtained by annealing TiO₂nanowires in NH₃ atmosphere.TiO₂ dielectric film was obtained by anodization TiN nanowires.The CU value of the obtained electrolytic capacitor was 236.2?F V cm^-2.The tan?is 0.36 and the leakage current is 0.14?A?F^-1 V^-1.After transforming the TiO₂ dielectric film into Ba TiO₃dielectric film by hydrothermal reaction,the CU value of Ba TiO₃ dielectric film is 359.2?F V cm^-2,which is 3.99 times the CU value obtained by constructing the same electrolytic capacitor on the TiN plane.The energy density is 0.54 m J cm^-2,the tan?is 0.32,the leakage current is0.12?A?F^-1 V^-1.The CU value increased by 41.3%compared with TiO₂ dielectric film,the tan?decreased by 13.4%and the leakage current decreased by 39.1%.The origin TiO₂ nanotube was fabricated by anodization of Ti foil.The thick-wall TiO₂nanotubes were prepared by corrosion using piranha solution and deposition in Ti Cl₄ solution of origin TiO₂ nanotube.The effects of different anodization,corrosion and deposition processes on the morphology and performance of nanotubes were investigated.The nanotube array obtained by secondary anodization are arranged more regularly and possess large diameter.The inner wall of nanotubes can be etched with piranha solution for 2 min at 70°C and the diameter is increased by 27.7%without destroying the nanotube structure.Then the wall of the TiO₂ nanotubes were thicken by depositing TiO₂ nanoparticles in 0.1 mol L^-1 Ti Cl₄ solution.After 4 cycles of cyclic deposition,thick-walled nanotubes could be obtained with the complete nanotube structure.The TiN nanotubes were fabricated by annealing TiO₂ nanotubes in NH₃atmosphere.TiO₂ dielectric film was obtained by anodization of TiN nanotube.When the oxidation voltage is larger than 7 V,part of the TiN nanotube will be completely anodized.The CU value of the TiO₂ dielectric film prepared under 7 V is 290.4?F V cm^-2,the tan?is 0.51,and the leakage current is 0.28?A?F^-1 V^-1.After the TiO₂ dielectric film was transformed into Ba TiO₃ dielectric film by hydrothermal reaction,the CU value increases from 290.4?F V cm^-2 to 381.2?F V cm^-2,the tan?was reduced from 0.50 to 0.18 and the leakage current was reduced from 0.28?A?F^-1 V^-1 to 0.11?A?F^-1 V^-1,which was reduced by 64.3%and 61.4%,respectively.The energy density is 1.33 m J cm^-2.The CU value is 4.24 times as which obtained by constructing the same electrolytic capacitor on the TiN plane.