Preparation And Electrochemical Properties Of Lignin-based And Cellulose-based Carbon Materials Derived From Hemp

With the rapid development and popularization of energy storage technologies such as lithium-ion batteries and supercapacitors,people have to face the challenges of the cost,sustainability and environmental friendliness of energy storage device.Due to owning many attractive advantage such as abundant reserves,low-cost,good chemical stability and excellent electrical conductivity,biomass-derived carbon materials have been widely researched as a potential high performance energy storage material.In this paper,biomass-derived carbon materials with special morphology were prepared by using different preparation methods from lignin and cellulose extracted from hemp rods,and they were used as the electrochemical performance as anode materials for lithium ion batteries and electrode materials for supercapacitor.The details are as follows:(1)Lignin-derived carbon microspheres with nitrogen-oxygen co-doping have been prepared by hot solvent method and direct carbonization method using hemp lignin as raw material.Furthermore,we have studied the effects of different carbonization temperatures on the lithium storage performance of carbon microspheres.The research indicated that the carbon microspheres obtained by carbonization at 900? exhibited good rate performance and cycling performance when used in a negative electrode of a lithium ion battery(the specific capacity of 546.5 mAh g-1 after 1000 cycles at 2A g-1).(2)High nitrogen content(3.09at.%),high specific surface area(540.05m2 g-1)and heterostructure(honeycomb carbon skeleton supporting monodisperse carbon microspheres)functional carbon were prepared by hemp lignin pretreated by aminophenol.The optimized sample carbonized in 800°C exhibited excellent lithium storage performance as used in lithium ion battery anode materials.The reversible capacity of 0.1 A g-1 current density reached 860.5 mAh g-1,and 403.7 mAh g-1 after 5,000 cycles,the capacity reduction rate is only 5.85%.(3)Using hemp cellulose as raw material,We successfully prepared hierarchical porous carbon with ultra-high specific surface area(2537.48m2 g-1)and rich surface oxygen content(17.15at.%)by hydrogen sulfate and activation with KOH.The effects of hydrothermal time,hydrothermal temperature and activator dosage on the performance of porous carbon were studied in this thesis.The optimized HC-2K exhibited excellent rate performance(specific capacitance of 270 and 216.5F g-1 at current density of 0.5 and 20A g-1)and good cycling performance(the specific capacitance of 183.3 F g-1 after 10000 cycles at 20A g-1,the capacity retention rate was 85.94%)in 6M KOH three-electrode system.