Preparation And Sodium-storage Performance Of Biomass-derived Hard Carbon Anode Materials

Lithium-ion batteries have developed rapidly since their successful commercialization,and their products are widely used in 3C digital products,Evs and electrochemical energy storage.But the scarcity of lithium resources and high costs limit their long-term development.Sodium-ion batteries have the advantages of abundant reserves,low cost and high safety,so it is considered to be a new type of secondary battery that is expected to replace lithium-ion batteries.Research must be urgently pursued to create electrode materials with a high energy density,long cycle stability,low cost,and high safety.In this paper,low-cost biomass waste was used as a precursor to synthesize biomass-derived hard carbon anode materials by simple preparation method,and the differences in microstructure and sodium storage performance were explored,the effects of different carbonization temperatures on the sodium storage performance of biomass are also studied.At the same time,sunflower stem carbon microspheres were prepared by acidic hydrothermal carbonization with mild synthetic conditions,and its electrochemical performance as a sodium-ion battery and the anode of lithium-ion batteries were studied and analyzed.The following are the primary work contents:(1)Biomass wastes such as dragon peel,sunflower stem and sunflower tray were selected as precursors,and biomass-derived hard carbon anode materials were synthesized by direct high-temperature carbonization,and the differences in sodium storage performance of different biomass were compared.At the same time,the effects of carbonization temperature on the microstructure and sodium storage performance were studied by XRD,SEM,Raman,specific surface area and pore size distribution tests,as well as electrochemical performance tests.The three biomass materials can show good cycling performance when used as anode materials for sodium-ion batteries,and they can have outstanding capacity recovery ability after high rate test.By comparing the microscopic properties and electrochemical properties at different temperatures,it is found that the main contribution of materials of different structure to sodium storage capacity is also different.For example,dragon peel and sunflower tray hard carbon materials mainly realize the storage of sodium ions through the embedding between graphite carbon layers,while sunflower stem hard carbon materials mainly store sodium ions through the adsorption and filling of the internal pores of the material.(2)The anode material of sunflower stem carbon microsphere was prepared by acid hydrothermal carbonization,and the formation conditions of carbon microsphere morphology were comparatively studied,and it was found that different biomass raw materials,carbonization temperature,precursor particle size and solution conditions of hydrothermal reaction all affected the formation of carbon microsphere morphology.The prepared hard carbon material formed a carbon microsphere morphology with smooth surface and uniform size at 500℃,and had the highest sodium and lithium storage capacity.At a charge-discharge current density of 20 mA·g-1,the reversible specific capacity as a sodium anode material reaches 257.3 mAh·g-1,while the reversible specific capacity as a lithium battery anode material reaches 754.1 mAh·g-1,which shows very excellent sodium storage and lithium storage potential.