Preparation Of Rice Husk-derived Novel Silicon/Carbon Anode Materials And Their Electrochemical Performance

In order to solve the current energy crisis,the development of new energy storage devices has become increasingly important.The rechargeable battery can gradually meet the daily needs of the people.It has been applied to electric vehicles,aerospace,medical and other fields.As a successfully commercialized rechargeable battery,lithium-ion battery has many excellent properties:high cycle life,high specific energy,high working voltage,no pollution,and good safety performance.The development of anode materials is an important prerequisite for the further development of lithium-ion batteries.The traditional anode material-graphite,has been successfully commercialized but the lower theoretical specific capacity(372 mAh g^-1)and poor rate performance also limit the further application of lithium-ion batteries.At present,various anode materials are available,such as metal oxides and silicon-based materials,Among them,silicon has drawn extensive attention due to its abundant reserves and extremely high theoretical specific capacity(4200 mAh g^-1).In this paper,we use rice husk as both source of silicon and carbon to prepare a silicon-carbon composite using simple carbonization and magnesiothermic reduction reaction.Compared with the traditional method,this method does not require additional compounding steps and silicon source precursor.In this paper,the main research contents are as follows:?1?Using rice husk as raw material,carbonization treatment was carried out to obtain carbon and silica composite after washing by deionized water and hydrochloric acid to obtain clean rice husk.Finally,after magnesiothermic reduction reaction,the obtained product was washed with hydrochloric acid and hydrofluoric acid,respectively,to obtain a silicon carbon composite.In this paper,we studied the main carbonization temperatures?450,550,650,750??and magnesiothermic reduction reaction temperatures?600,700,800??.After structure characterization and electrochemical performance testing,we finally choose 550?and 700?as carbonization temperature and magnesiothermic reduction reaction temperature.At a current density of 100 mA g^-1,initial discharge capacity was 1256.1 mAh g^-1,and the reversible specific capacity was maintained at 556.1 mAh g^-1 after 100 cycles.?2?In order to further improve the electrochemical performance of the silicon/carbon material,we used zinc chloride as an activator to activate the rice husk,and then carry out the?1?operation,and finally obtained a porous silicon/carbon material.RGO was introduced into the porous silicon/carbon composite to improve the electrochemical stability and consolidate the structural integrity.Finally,we obtained a silicon/carbon/RGO composite.We compared the effects of different activators?ZnCl₂,CaCl₂,K₂CO₃?and activation ratios?1:1,1:2,1:3?on the structure and properties of the material.It was finally determined that the rice husk was pretreated with zinc chloride at1:2?RH:ZnCl₂=1:2?.After activation,the specific surface area of the material reached539.442 m² g^-1,and the specific surface area was greatly improved compared with the silicon/carbon(198.792 m² g^-1)in?1?.At a current density of 100 mA g^-1,the specific capacity of the material in the first cycle was as high as 1684.9 mAh g^-1.After 80 cycles,the reversible specific capacity was stable at 764.8 mAh g^-1.Compared with?1?,the reversible specific capacity of the material has been significantly improved.At the same time,the material still has a reversible specific capacity of 317.5 mAh g^-1 at a current density of 1 A g^-1.