Construcion And Electrochemical Performance Of Furfural-Based Aqueous Zinc Ion Energy Storage Electrodes

With the rapid development of society,the continued energy consumption of fossil fuels is causing serious environmental pollution problems and has significant impact on global climate change.In recent years,the search for sustainable energy sources such as solar,hydropower and bioenergy,and the development of corresponding energy storage and conversion technologies has become increasingly intensive.Among the different energy storage technologies,electrochemical energy storage systems have been considered the most practical,reliable and efficient option,including zinc-ion batteries,metal-air batteries and supercapacitors.However,the energy density,lifetime and reliability of current energy storage technologies are still not sufficient to meet the growing demand for practical applications,and further exploratory research in electrode material design and other areas is urgently needed.Currently,biomass carbon/composites are receiving increasing attention from researchers due to their unique easily adjustable structure,good electronic conductivity,natural abundance and environmental friendliness,making them promising materials for electrode composition in electrochemical energy storage devices.The performance of electrochemical energy storage devices is largely dependent on the electrode material,and the design of biomass-derived carbon electrode materials with specific morphologies to enhance the overall electrochemical performance and cycling stability is the issue at hand,and promises to expand its application areas.In this thesis,biomass-derived furfural was used as the main raw material for the synthesis of hydrothermal carbon materials with special morphology by one-step hydrothermal carbonisation using Schiff base reaction.On this basis,the pore structure was adjusted by chemical activation and further compounded with electrochemically active metal oxides to construct different aqueous zinc ion-carbon based energy storage electrode materials.The constructed biomass-derived carbon materials with special morphology and porous structure have morphological structure that can be used as reservoir for electrolyte to store more electrolyte,and the rich pore structure and high specific surface area can shorten the electrolyte transport distance and enable rapid electrolyte ion transport,enhancing energy storage enhancing stability and expanding to low temperature applications.The main studies are as follows:（1）The carbon particles with special morphology were prepared by one-step hydrothermal carbonization method using the biomass derivative furfural as the carbon source and different amines containing nitrogen structure as the nitrogen source,and the difference between hydrophilic and hydrophobic carbon precursors was adjusted by the Schiff base reaction between the aldehyde and amino groups in the precursor molecules.The effects of reaction conditions such as molar ratio of reactants,reaction time and reaction temperature on the morphology and microstructure of hydrothermal carbon materials were systematically investigated,and the hydrothermal synthesis mechanism of furfural-based carbon materials with different morphologies was proposed.The microstructure,crystal structure,specific surface area and pore size distribution of the prepared carbon materials were investigated by FTIR,Raman spectroscopy and nitrogen adsorption and desorption tests.Among them,nitrogen-oxygen co-doped waxberry-like spherical carbon particles with uniform size（particle diameter of about 2-3μm）and nanosheet wrapping could be prepared by using furfural as the carbon source and melamine as the nitrogen source at reaction time of about 16 h,reaction temperature of 180℃and molar ratio of 1:2.（2）Nitrogen-doped porous carbon materials with unique"waxberry-like"structure were prepared by one-step activation method,and the effects of the activation process on the morphology,chemical composition and pore structure of the"waxberry-like"nitrogen-doped porous carbon materials were investigated.NO-CPC-750 possessed BET specific surface area of 1151.3 m² g^-1,average pore size of 0.91 nm and high effective pore percentage of 85.29%,which matched the hydration diameter of Zn²⁺.The"waxberry-like"nitrogen-doped porous carbon material has unique morphology,which facilitates the storage of electrolyte inside the nanosheets and shortens the electrolyte transport distance,and exhibits excellent electrochemical properties.By assembling the NO-CPC-750 with zinc ion hybrid supercapacitor using 2 M ZnSO₄ electrolyte,it has high capacity(122.3 mAh g^-1 at current density of 0.1 A g^-1),high energy/power density(97.78 Wh kg^-1/8000 W kg^-1)and excellent cycling stability（98% capacitance retention）after 10,000 consecutive charge/discharge cycles.The assembled NO-CPC-750//Zn also exhibits excellent low temperature performance and operability(78.27 mAh g^-1 at-30℃,with no performance degradation over three cycles of stability between-20 and 20℃).This study proposes a new design strategy for carbon electrode structures that can facilitate the diffusion and/or transport of multivalent ions.（3）The nano porous carbon material was prepared by one-step activation method on the basis of the morphologically regular nano flower-like spherical carbon particles studied by the group previously.The surface morphology and electrochemical properties of nano flower-like carbon electrode materials were investigated at different hydrothermal temperatures.The V₂O₅/nano flower-like carbon electrode material was further prepared by hydrothermally coating the metal oxide vanadium pentoxide on its surface in one step using porous nano flower-like structures.The morphology and electrochemical properties of V₂O₅/nano flower-like carbon electrode materials at different hydrothermal temperatures were investigated.The V₂O₅-180 nano flower-like carbon electrode assembled into zinc-vanadium battery at hydrothermal temperature of 180℃ exhibited high reversible specific capacity of 244.35 mAh g-1 at current density of 50 mA g^-1,and after 2000 cycles V₂O₅-180 was still able to maintain its original specific capacity of 97.5%with Coulombic efficiency of nearly 98%,indicating that V₂O₅-180 has good electrochemical reversibility and excellent cycling stability as the cathode material for zinc-vanadium batteries.In addition,the specific capacity value of the constructed zinc ion battery reached 171 mAh g^-1 at-20℃ with specific capacity retention rate of 70%,which provides useful reference and guidance for investigating the influence of electrode morphological characteristics on the performance of aqueous zinc ion batteries.（4）The MnO₂-coated"waxberry-like"porous carbon particle was further designed and synthesized using activated"waxberry-like"porous carbon as carrier and introducing manganese oxides in situ during the hydrothermal synthesis of the carbon particles.The morphology,lattice structure and electrochemical properties of the MnO₂-coated"waxberry-like"porous carbon particles were investigated by controlling the addition of KMnO₄ in different amounts.The MnO₂/NC-30-140 sample exhibited higher surface area of 332.14 m² g^-1 and larger pore volume of 0.44 cm³ g^-1 when added with 30 mM KMnO₄ at hydrothermal temperature of 140℃ to form Zn-Mnbattery at current density of 50 mA g^-1.MnO₂/NC-30-140 as the cathode material assembled with zinc foil to form zinc-manganese battery exhibited high reversible specific capacity(251 mAh g^-1)and excellent energy density(225.9 Wh kg^-1).After 3000 cycles at current density of 0.5 A g^-1,MnO₂/NC-30-140 maintains its original specific capacity of 98.62%and coulombic efficiency of nearly 99%,which due to the unique morphology and pore characteristics of the MnO₂/"waxberry-like"carbon electrode,which facilitate rapid electrolyte transport.Thus,the assembled aqueous zinc ion battery exhibits excellent electrochemical reversibility(specific capacity value of 181 mAh g^-1 and retention rate of 72%)at low temperatures（-20℃）.（5）In order to inhibit the growth of Zn dendrites to improve the stability of aqueous Zn-ion batteries,the paper constructs Zn/"waxberry-like"carbon anode materials by chemical plating on the surface of"waxberry-like"carbon materials to further investigate the effect of electrode morphology on the electrochemical performance and stability of Zn-ion batteries.The results show that the chemical galvanization addition ratio has a significant effect on the microstructure and zinc dendrite growth of the electrode material.The optimized Zn-1:2 anode material has specific surface area of 127.86 m² g^-1 and maximum pore volume of 0.39 cm³ g^-1.Notably,the morphological effect of the zinc anode as an aqueous zinc ion battery changes the direction of zinc dendrite growth,thus improving the damage to the diaphragm due to dendrite growth and further enhancing the electrochemical performance as well as the cycling stability.The zinc-manganese battery assembled from Zn-1:2 anode and MnO₂/"waxberry-like"carbon cathode exhibits high reversible specific capacity(243 mAh g^-1)at current density of 50 mA g^-1and maintains specific capacity of 97%after 4000 cycles with coulombic efficiency of 97.5%.The cycling stability of the aqueous zinc ion battery is significantly enhanced.The unique morphological characteristics of the electrode material enable the constructed Zn-Mnbattery to exhibit good electrochemical behaviour even at low temperatures(-20℃,specific capacity of165 mAh g^-1,retention rate of 68%).