Preparation And Electrochemical Properties Of Biomass Silicon-Based Anode Materials

Lithium-ion batteries?LIBs?are playing an increasingly important role in contemporary society.With the rapid development of society and the continuous improvement of consumption levels,there is a higher requirement for the energy density of lithium ion batteries.As an important component of lithium ion batteries,negative electrode materials have a decisive influence on the capacity density and price of LIBs.Among the candidate anode materials proposed to replace commercial graphite,silicon?Si?materials are considered to be the most promising and commercially available anodes due to their high theoretical capacity(4200 mAh g^-1)and abundant reserves one of the materials.However,the silicon material undergoes large volume expansion during repeated charge and discharge processes,resulting in the crushing of the electrode material and the rapid decay of capacity,resulting in extremely poor cycling performance,which severely limits its commercial development.In addition,due to the current manufacturing process,the silicon material used for LIBs,the high price also further limits its large-scale commercial application.In response to the scientific problems that need to be solved urgently,in this paper,we use silicon-rich biomass?such as rice husk and oat husk?as raw materials,and take advantage of its natural SiO₂properties through simple carbonization and reduction processes.A silicon-oxygen-carbon composite anode material was synthesized,which exhibited excellent electrochemical performance.Specific research contents are as follows:?1?Using rice husk as the silicon source,a low-cost and high-capacity rice husk-based SiO_x/C@graphite?SCG?composite anode material was designed and synthesized through a simple one-pot carbonation/hydrogen reduction process of rice husk and graphite.The composite anode material was characterized by XRD,TG,XPS,BET,EDS,SEM and TEM,and assembled into a button half-cell for electrochemical performance test.Electrochemical test results show that this material is used as a negative electrode of a lithium ion battery,and the porous SiO_x/C@graphite composite material has considerable reversible capacity and excellent cycle stability(after 300 cycles at a current density of 0.5 Ag^-1The reversible capacity is still 842 mAh g^-1)and high rate performance(the reversible capacity is 562mAh g^-1after 300 cycles at a current density of 1 Ag^-1).This is mainly due to the positive synergy between the SiO_xnanoparticles and the carbon matrix network formed in situ can effectively improve the performance of the electrode material.In addition,on the one hand,the added graphite can enhance the conductivity of the composite material and reduce the resistance of the electrode material,which is conducive to the improvement of rate performance.On the other hand,it can also buffer the volume change of SiO_xduring charge and discharge,which is beneficial to the improvement of material cycle performance.?2?Using oat husk as the silicon source,the precursors were prepared by washing and drying,low-temperature calcination and pre-carbonization,and then doped with graphite in different proportions for ball milling and mixing,and then calcined in hydrogen-argon mixed gas at high temperature to obtain oats husk-based SiO_x/C@graphite?SCG?composite material.The SCG-1 sample maintains a specific capacity of 600 mAh g^-1after200 cycles at a current density of 1 Ag^-1.The conclusion of the study shows that proper doping of graphite can effectively improve the conductivity of the material and increase the lithium ion storage site of the electrode material.