Study On The Construction And Energy Storage Mechanism Of Supercapacitors Derived From Wood Graded Structure Derived Carbon Materials

Wood is the most abundant,green,and renewable resource found in nature,extensively utilized in traditional industries such as manufacturing artificial boards,pulp and paper production,as well as construction and furniture.As science and technology continue to advance and develop,our understanding of wood has deepened.Utilizing nanotechnology,bionics,and other state-of-the-art scientific and technological principles,combined with the distinctive hierarchical porous structure and chemical composition inherent in wood,its derived carbon materials offer immense potential in the realm of green energy storage.Supercapacitors,as a novel form of energy storage devices,possess remarkable characteristics including high power density,extended cycle life,rapid charging and discharging capabilities,and suitability for diverse temperature ranges.These features have garnered significant attention from researchers worldwide and sparked extensive studies in this field.However,current research on utilizing wood in supercapacitors primarily focuses on improving the energy storage performance of electrode materials,often overlooking the significant impact of wood’s unique hierarchical structure,chemical composition,and other inherent advantages on energy storage capabilities.Addressing these gaps,this study aims to investigate the specific surface area,pore size distribution,surface functional groups,crystal structure,morphology,and other physicochemical properties of wood-based structures across various scales(including solid wood,wood fibers,and nanocellulose).By exploring the structure-activity relationship between the physicochemical properties of different carbon materials and their energy storage performance,the research endeavors to develop a range of wood-derived electrode materials.The ultimate goal is to achieve effective morphology and structure regulation,as well as optimize the electrochemical performance of wood-based carbon composites.Building upon this foundation,a comprehensive range of supercapacitors were constructed utilizing diverse wood-derived carbon electrode materials.Through extensive testing,characterization,and analysis of electrochemical performance,the energy storage mechanism of wood carbon materials within the capacitor was thoroughly examined.This investigation uncovered the remarkable synergistic effect of wood when employed in energy storage materials.These findings not only contribute to a deeper understanding of the potential applications of wood graded structures in the realm of energy storage but also lay a solid theoretical groundwork for their comprehensive utilization.The main research content and results are as follows:(1)Performance evaluation and electrochemical analysis of wood grading structures at different scales.The physicochemical properties of wood grading structures at different scales were tested and characterized,and the influence of the microstructure,chemical composition,crystal structure,pore size distribution,and other aspects of their derived carbon materials on electrochemical performance was explored.The interior of solid wood and its carbon materials is mainly a channel structure formed by fibers and ducts,and its cell wall can provide a large number of specific surface areas and active site.Wood fibers and their carbon materials are mainly formed from a single fiber,with a hollow structure inside.Although they can store a large amount of electrolyte ions,they do not have a structure that runs through the top and bottom.The internal structure of nanocellulose and their carbon materials is a multidimensional network layer structure,while the layer structure is a porous network structure composed of fibers,with excellent specific surface area and pore volume.Research has found that these structural characteristics and chemical composition have a significant impact on the electrochemical performance of their derived carbon materials.(2)Solid wood loaded ZIF(Zeolite Imidazole Framework)to construct an integrated thick electrode material and structural regulation.Composite materials were prepared by loading ZIF-67 onto solid wood using hydrothermal methods,insitu growth,and other treatment methods.The composite form of ZIF-67 on solid wood was controlled by controlling experimental conditions such as reaction time,reaction temperature,and reagent ratio.An integrated thick electrode material with different morphology,structure,and electrochemical performance was obtained.The thick electrode material retains the array channel structure of natural wood with graded porosity,low curvature,and upper and lower connectivity.This unique structure is conducive to the rapid transport and storage of ions in the electrolyte,and has a positive promoting effect on improving its electrochemical performance.The introduction of N element can doping carbon materials,thereby improving their wettability,conductivity,carbon defect degree,and other properties,and improving the electrochemical performance of electrode materials.The optimized sample CWZ-3 exhibits excellent area specific capacitance(5155.3 mF/cm2)at a current density of 2.5 mA/cm2(172.40 F/g at a current density of 1.0 A/g),and the thick electrode material exhibits outstanding rate performance and cyclic stability.(3)Preparation and performance regulation of ZIF composite electrode materials loaded with wood fibers.After loading ZIF-8 onto wood fibers and hightemperature carbonization,a hollow and independent carbon fiber electrode material is obtained.By changing the synthesis ratio of ZIF-8,the electrochemical performance of the carbon fiber electrode material can be regulated.The carbon material layer formed by ZIF-8 is coated on the surface of wood carbon fibers,which has a positive impact on the storage of electrolyte ions.At the same time,the excellent conductivity of the carbon substrate material provides a basic guarantee for its electrochemical performance.The optimized CWFZ2 electrode material has a specific capacitance of 270.74 F/g at a current density of 0.5 A/g,and can still maintain 98.4%of the initial specific capacitance after 10000 cycles of testing,indicating that the material has excellent cycling stability.(4)The construction and performance evaluation of electrode materials featuring a multidimensional network structure with embedded ZIF nanofibers were carried out.By leveraging the self-assembly properties of wood nanocellulose,a carbon aerogel material with a three-dimensional network lamellar structure was obtained through the carbonization and oxidation of ZIF-67 and wood nanocellulose as the matrix.The carbon aerogel serves not only as a carrier structure with excellent conductivity but also possesses numerous microporous and mesoporous structures within its lamellar framework,which actively contributes to the storage of ions in the electrolyte.The optimized electrode material,CCAZ3,exhibited a specific capacitance of 574.44 F/g at a current density of 1 A/g.Furthermore,even at higher current densities(20.0 A/g),its specific capacitance remained at 302.22 F/g,indicating exceptional rate performance.(5)A study was conducted on the assembly of supercapacitors using wood graded structures of different scales and evaluating their energy storage performance.The electrode materials obtained from these varied wood grading structures were assembled into three types of supercapacitors:solid wood-based,wood fiber-based,and wood nanocellulose-based.Experimental tests have demonstrated the remarkable electrochemical properties exhibited by these supercapacitors,including high energy density,power density,and cyclic service life.Notably,the solid wood thick electrode material can be utilized as an electrode material without requiring any additional treatment.It displays exceptional characteristics of double-layer capacitance,with excellent area-specific capacitance,volume-specific capacitance,and cycling stability.Wood fibers,on the other hand,require mixing with other active substances to prepare electrode materials for use.They demonstrate typical characteristics of double-layer capacitance,similar to the energy storage performance of solid wood thick electrode materials,and exhibit excellent cycling stability.When wood nanofibers are utilized to construct carbon aerogel,they also require blending with other active substances to prepare electrode materials.Due to the presence of Co3O4 within the wood nanofibers following carbonization and oxidation,they exhibit the characteristics of pseudo-capacitive energy storage.This article leverages the characteristics of wood’s multi-layer pore structure and abundant surface active functional groups to construct wood graded carbon materials of different scales.It explores the influence of the physicochemical properties of these wood graded carbon materials on their electrochemical performance.Building upon this foundation,an integrated thick electrode composite material with a graded porous structure,low curvature,and interconnected array channel structure,a hollow and independent carbon fiber electrode material,and a three-dimensional network layer structure electrode material rich in Co3O4 were synthesized.Subsequently,symmetrical supercapacitors were assembled using these materials.The findings of this study not only enhance the electrochemical performance of various wood-derived carbon electrode materials but also shed light on the application of wood graded structures in supercapacitors.This research provides a theoretical foundation for improving the high-value utilization of wood and expanding its comprehensive use in the field of energy storage materials.