Biomass Waste Derived Hard Carbon As Anode Materials For Sodium-Ion Batteries

Among secondary batteries,lithium-ion batteries(LIBs)with high energy density,light weight and long cycle life have achieved great success in the fields of electronics and electric vehicles.However,the shortage of lithium resources limits the further development of LIB.Sodium,which is located in the same main group and has similar physicochemical properties with lithium,is one of the most abundant elements in the Earth's crust,making sodium become a alternative resource for lithium resource.In recent years,the cathode and anode materials for sodium ion batteries have been rapidly developed.Among them,biomass or biomass wastes derived hard carbon materials with the advantages of green,as well as economic and high reversible capacity have became a research hotspot of anode materials for sodium ion batteries.In this work,biomass wastes from different biomass waste(tea slag,peanut shells and soybean hulls)are used as the precursors of hard carbon materials.The sodium ions storage performance of the biomass-derived hard carbon anode material has been optimized by controlling the preparation conditions such as different carbonization temperatures or different hydrothermal pretreatment conditions.The main contents and result of this work are summarized as follows:(1)Hard carbon materials were prepared by pyrolysis at different temperatures using the abundant and cheap jasmine silver tea as the precursor;then its electrochemical performance was tested in sodium ion batteries.The results suggest that the graphitized structure of hard carbon materials is greatly affected by the pyrolysis temperature,while the graphitized structure will affects the sodium storage performance of hard carbon materials.Therefore,hard carbons derived from jasmine silver tea at different pyrolysis temperatures used as anode materials have quite different electrochemical properties.In addition,pretreatment of the precursor with hydrochloric acid will also affect the surface defects and graphitization structure,thereby optimizing the electrochemical performance of the jasmine silver tea derived hard carbon materials.Comparing all the samples,HT-800 can deliver the highest reversible capacity of 259 mAh g~-11 and good cycle stability.After 100 cycles,the reversible capacity still retain99%.(2)We also have prepared renewable and low-cost hard carbon materials using peanut shells as biomass precursor a hydrothermal pretreatment for different treatment time after that by a pyrolysis process at 800?.Hydrothermal carbonization plays an important role in the morphology transformation of materials.The morphology of the peanut shells derived hard carbon materials prepared by hydrothermal pretreatment were transformed from a three-dimensional porous structure to a lath-shaped with a large specific surface area and a suitable interlayer spacing.Comparing all the samples,the PSDHCs-4 sample has the highest reversible capacity of 261 mAh g~-11 at a current rate of 0.1C,after 100 cycles,the capacity retain 99%and deliver a good reversible capacity of 100 mAh g~-11 at a current rate of 5C.(3)We also have synthesized hard carbon materials used soybean hulls as biomass precursor by a hydrothermal pretreatment after that by a pyrolysis process at 1300?.Comparing the electrochemical performance for potassium and sodium ion battery,it was found that soybean hulls derived hard carbon not only exhibited better cycling performance in potassium ion batteries,but also had higher specific capacity at high current rates than in sodium ion batteries.The results indicates that soybean hulls derived hard carbon has the advantage of being used as anode material for potassium ion batteries,and also shows that potassium ion batteries have good development potential.