Preparation And Electrochemical Performance Of Low-dimensional Nano-carbon Materials

With the continuous advancement of society and the continuous improvement of people's living standards,the quality requirements for electronic equipment and electric vehicles are getting higher and higher.With the continuous development of energy storage devices,energy storage with higher energy density and higher power density is prepared.Devices have become an important research direction for researchers.As an emerging energy storage device,supercapacitors are constantly sought after by researchers.Electrode materials play an important role in supercapacitor devices.In practical applications,carbon materials with high specific surface area,excellent electrical conductivity,good chemical stability and low cost have become the ideal electrode materials for supercapacitor applications.The elemental composition,atomic arrangement and dimensions of carbon materials are important factors in determining the electrochemical properties of materials.Among these factors,the dimensions of carbon materials play a key role.After entering the 21st century,low-dimensional nano-carbon materials have gradually become a research hotspot in various fields.Low-dimensional nano-carbon materials mainly include:one-dimensional?1D?nano-carbon materials,such as carbon nanotubes,carbon nanorods,etc.;two-dimensional?1D?nano-carbon materials,such as carbon nanosheets;Three-dimensional?1D?nano-carbon materials,such as nano-carbon materials and nano-carbon structural foams with cross-linked nanostructures and one-dimensional two-dimensional nano-carbon composite materials.Among these low-dimensional nanomaterials,1D carbon nanotubes?CNTs?and 2D carbon nanosheets?CNS?have become the research hotspots due to their own structure and composition advantages.Based on the formation process of carbon nanotubes and carbon nanosheets,a large number of carbon nanostructures such as carbon nanotubes and carbon nanosheets were designed and applied to supercapacitors.The formation mechanism of the prepared materials was systematically studied.The morphology,composition and electrochemical properties of the materials were characterized and tested.The main conclusions are as follows:A large number of nitrogen and oxygen-doped?N,O-doped?CNTs were synthesized in one step using the"sol-gel-low temperature self-propagating combustion"method.N,O-CNTs can range in length from 0.6?m to 1.5?m.We systematically studied the effects of raw material ratio,pH of precursor solution,calcination temperature and holding time on product structure and electrochemical performance.Unique 1D structure,hollow structure,high aspect ratio 1D N,O-CNTs have nanopores?macroporous/mesopor/microporous?combinations at various levels.1D N,O-CNTs with graded macropores/mesopores/micropores can be well constructed to provide abundant active sites,fast ion/electron transport channels,large electrodes/electrolytes in energy storage applications Contact area and stable electrode structure.1D N,O-CNTs electrode materials exhibit excellent electrochemical performance in supercapacitor applications,with a specific capacitance of 162.5 F g^-1 measured at 0.3 A g^-1,circulating at a current density of 2 A g^-1 After 20000 laps,the specific capacity can still have a high retention rate of 97.6%.Based on the above method for preparing 1D N,O-CNTs,we prepared a large number of 2D CNS and metal particle composite materials?2D CNS-Ni,Co?by improving the raw material composition and experimental parameters.The introduction of a suitable precursor solution,pH and ammonium nitrate is a key factor in achieving large scale 2D CNS-Ni,Co.We propose a"sol-gel-instant pyrolysis"mechanism to reasonably explain the formation process of CNS.Compared with other methods for preparing 2D CNS,this method has the advantages of simple and high efficiency,low cost,and large output.2D CNS-Ni,Co has good structural stability,uniform nano-thickness,and lateral dimensions spanning tens to hundreds of microns.Due to the unique physical/chemical properties of the 2D structure,the NiCo nanoparticles contained in these nanosheets undergo a further sulfide and selenization to form a Transition Metal Sulfide?TMS u?,Transition Metal Selenide?TMSe?.Nanocomposites 2D CNS-NiS₂,CoS₂,2D CNS-NiSe₂,CoSe₂ composited with 2D CNS exhibit excellent electrochemical performance as electrode materials for supercapacitors.Among them,2D CNS-NiS₂,CoS₂,2D CNS-NiSe₂,CoSe₂ electrode materials have a specific capacitance of 1195 F g^-1,1400 F g^-1 at 1 A g^-1,and have excellent cycle life.The high-quality two-dimensional structure,simple and high-yield synthesis method and excellent charge storage performance have greatly promoted the wide application of 2D carbon nanomaterials in energy storage.