Study On Ag-modified Fe₂O₃ Nanoparticles And Nitrogen-doped Carbon Nanotubes As Electrode Materials For Supercapacitors

With the development of society and economy,people's demand for energy is gradually increasing.Most of the energy currently used is non-renewable fossil energy such as coal,oil,and natural gas,besides,the burning of such fossil fuels brings serious environmental pollution.To address these issues,people are looking for new renewable energy sources such as wind energy,solar energy,tidal energy,etc.,these kinds of new energy effectively avoids the pollution problem.But these energy are intermittent.In order to use these new energy sources efficiently,a large amount of energy storage devices are required.As a newly emerged high-performance energy storage device,supercapacitors possess many advantages such as high power density,long service life,and wide application range.Its appearance has filled the technical gap between traditional lithium batteries and ordinary capacitors,and broadens the application field of energy storage devices..In the development of supercapacitors,highly efficient and functional energy storage materials are the main goals of device research and application..In this essay,two kinds of supercapacitor materials with good performance are designed based on carbon cloth with good flexibility as the substrate of the capacitor device,and their morphology characteristics,electrochemical performance,ion transport mechanism and filtering performance are further studied.The main contents are as follows:(1)Ag@Fe₂O₃nanoparticles were synthesized by a two-step method on carbon clothes,which were used as anode materials of high-performance supercapacitors.Iron-based material is a potential anode material for supercapacitors,however,its poor electrical conductivity and poor cycle stability limit the development of energy and power density,so the key issue is to improve the electrical conductivity and cyclic stability of iron materials.Here,we synthesized Ag-modified Fe₂O₃nanoparticles on carbon cloth as anode materials for supercapacitors.Carbon cloth is used as the base material as well as the current collector to supporting the electrode material in electrochemical testing and practical applications to avoid the fall of the capacitor capacity caused by the fall of the active material,at the same time,the super capacitor possess flexible properties.The material exhibits excellent electrochemical performance during electrochemical cycling;at a scan rate of 5 m V s^-1,the specific capacitance reaches 7.34 F cm^-2(1931.70 F g^-1),after 12000 the cycle,the specific capacitance value of 83%is still maintained.The energy density is 379.8 Wh kg^-1when the power density is 131.6 W kg^-1,and the energy density is 123.9 Wh kg^-1when the power density is2631.6 W kg^-1.The electrical conductivity and interface effects of Ag/Fe₂O₃are calculated using density functional theory,which theoretically proves the enhancement mechanism of the electrochemical performance of Ag@Fe₂O₃nanoparticles.In addition,the packaged Asymmetric supercapacitor(ASC)device has the flexibility and can light up 10 LEDs for 2 minutes and 30 seconds.At a power density of 1063.8 W kg-1,its energy density can reach 60.3 Wh kg^-1;even at a power density of 4255.3 W kg-1,its energy density can be maintained at 16 Wh kg^-1.All these results show that these materials have the potential to be used in energy storage,and the flexible ASC could be further applied to wearable flexible devices in the future.(2)A supercapacitor made of nitrogen-doped carbon nanotubes realize the conversion of alternating current with arbitrary waveforms of hundreds of hertz to direct current.Filter circuits are an indispensable class of electronic devices in modern electronic devices,and the filter capacitor is the core component of the filter circuit.Traditional filter capacitors mostly use aluminum electrolytic capacitors,however,aluminum electrolytic capacitors exit the disadvantages of small specific capacitance,large error and poor stability.In this research,the supercapacitor formed by nitrogen-doped carbon nanotubes is used in the filter circuit.The supercapacitor can achieved a specific capacitance of 30.2 F g^-1at a current density of 2 A g^-1.When the power density is 1800W kg^-1,the energy density is 48.96 Wh kg-1.Even when the power density is 9000 W kg-1,it can be maintained at 31.5 Wh kg^-1.The supercapacitor used in the filter circuit can convert an arbitrary waveform signal into a linear signal.The filtering effect is remarkable as the maximum fluctuation of the output signal is less than 16 m V.And it works stably in the frequency range of 1?100000 Hz and the amplitude window of 0?10 V.Its excellent performance can greatly improve the stability of the entire electronic circuit and greatly extend the service life of the electronic circuit,and can better meet the needs of high-end electronic products.