Preparation Of Wheat Straw Biomass Carbon And Application Of Energy Storage Materials

Lithium-ion battery is recognized as one of the most promising energy storage devices.It has many advantages such as high working voltage,high specific energy,long cycle life,no memory effect,convenient and non-hazardous use.It has been used in a wide variety of energy storage battery products and the market demand is still rising.Graphite materials are widely used as negative electrodes in commercial lithium-ion batteries(LIBs)due to their low potential platform,acceptable specific capacity,stable cycle performance,and low cost.However,the interlayer distance(0.335 nm)of graphite is small,resulting in a long diffusion distance of lithium ions in the graphite crystal,which increases the diffusion resistance of lithium ions,and the lithium dendrite phenomenon is prone to cause safety accidents when working at high current,which seriously hinders the development of high-performance lithium-ion batteries.Therefore,it is necessary to find a new structural material that avoids the occurrence of lithium dendrite and at the same time has the advantages of graphite.In this paper,wheat straw was used as raw material and KOH was used as activator.Porous biomass carbon was prepared by high temperature carbonization and chemical activation and applied as negative electrode material for lithium ion batteries(LIBs).The morphology and structure were characterized by X-ray diffraction(XRD),specific surface area and pore size analysis(BET),scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS).The electrochemical properties were analyzed based on the micro-morphology and structure,and the formation mechanism of porous structure was explored.In order to characterize whether it is suitable as the anode material of LIBs,porous biocarbon materials were assembled into button batteries,and a series of electrochemical tests were carried out at the electrochemical workstation,such as constant current charge-discharge,electrochemical impedance,rate and cycle performance.The results show that the specific capacitance of biomass carbon activated by KOH reaches 271.7F/g at 1 mv/s scanning rate,the first discharge capacity of lithiumion battery is 797.3 mAh/g at 0.1C rate,and the first Coulomb efficiency is 42.9%,respectively.In the second cycle,the apparent discharge capacity of biomass carbon is 342.7mAh/g.At the same time,after 100 cycles,the specific capacity of lithium-ion battery is stable at 310.5mAh/g.The specific capacitance retention rate is more than 90% and the coulomb efficiency is always about 95%.It shows that the sample has good rate performance and cycle stability.The samples prepared by this method have high specific surface area and rich hierarchical porous structure,which can improve the permeability of electrolyte and increase the reactive sites,and increase the free movement space of lithium ions and charges,which is conducive to the improvement of electrochemical properties.