Research On The Bio-based Composite Energy Storage Materials Based On Carbon-nitrogen Precursor Chito-oligosaccharide

Chito-oligosaccharide(COS)is a kind of small molecule oligosaccharide with amino groups which degraded from chitosan.Compared with chitosan,COS has the advantages of low molecular weight,high nitrogen content,strong biological activity,completely dissolve in water and non-pollution.At present,researchers have mostly explored the application of chitosan in the field of energy storage materials.However,few people have studied the application value of COS in this field.As a low-molecular-weight precursor,COS is completely soluble in an aqueous solution to make the composite more homogeneous.Compared with chitosan macromolecules,COS derived carbon has a higher porosity than macromolecules derived carbon,providing reliable channels for ions to shuttle.In addition,amino groups from COS effectually promote the wettability of electrode interface.The above-mentioned advantages of COS showed great potential in energy storage materials applications.With the urgent demand for high capacity and high endurance of new energy vehicles,portable electronics and communication equipment,researchers have focused on how to prepare lithium-ion batteries and supercapacitors with good portability,environmentally friendly,excellent cycle performance and high energy density.In this paper,COS is used as the carbon-nitrogen precursor to prepare electrode materials with excellent performance using novel and simple methods.The main research results are as follows:1.Preparation of nitrogen-doped porous carbon materials for supercapacitors by dual-alkali activated chito-oligosaccharide.Using COS as carbon-nitrogen source,activated carbon materials are prepared by dual-alkali activation of potassium hydroxide and calcium hydroxide,and nitrogen doped with melamine.The COS carbon materials with hierarchical complex porous structure have good electrochemical performance.The specific capacitance of COS-N-C-1 is as high as 267.4 F/g when the current density is 0.5 A/g.After 5000 cycles,the specific capacitance can still retain 93.9%,showing good cycling stability.The excellent electrochemical performance benefits from the modification of activation and nitrogen atom doping.The activator can make the material form abundant pore structure,increase the specific surface area,and increase the number of micro mesopores,which is conducive to the electrochemical adsorption of ions.In addition,when nitrogen functional groups are introduced into COS,a reversible oxidation-reduction reaction will occur in the material,resulting in Faraday current,thus providing Faraday quasi-capacitance and improving the electrochemical performance of COS-N-C-1.2.Preparation of lithium-ion battery anode materials with yolk-shell structure using chito-oligosaccharide as carbon-nitrogen source.Using COS as carbon source and nitrogen source,the Si@void@C anode material of lithium-ion battery with yolk-shell structure was prepared by simple hydrothermal method.The carbon shell in the yolk-shell structure can not only accelerate the transport rate of microscopic particles,but also significantly reduce the charge transfer resistance,and effectively protect the silicon core ball from electrolyte corrosion.The void layer between silicon core and carbon shell can adapt to huge volume expansion of Si and stabilize the electrode structure.The results show that Si@void@C exhibits superior cycle stability and high rate performance.At a current density of 420 mA g-1,the Si@void@C maintains a high capacity of 1038.5 mAh g-1 after 200 cycles.This studies showed that COS,as a carbon-nitrogen precursor,has a good industrial application prospect in preparing electrode materials for lithium-ion batteries and supercapacitors.