Fabrication And Electrochemical Properties Of Rice Husk Derived Silicon-based Composite Materials

The continuous exhaust of fossil fuels and a series of environment problems make the exploration of new energy sources concerned.Among the new sustainable energy storage system,lithium ion batteries are widely used in the field of electrical vehicles and portable electronic products due to their small size,high energy density,long cycle life,high stability and sustainable.As an important part of lithium ion battery,electrode materials has an influence on the performance of the battery,Silicon-based materials have being attracted much attention due to the highest theoretical capacity.However,the enormous volume change and poor electric conductivity of the silicon based materials lead to severe capacity fading of the anodes.To overcome these drawbacks,varies silicon based composites have been developed.Among the various natural substances,rice husk,which is an agriculture waste with giant volumes globally containing naturally formed silica and other organic components,has been used for the preparation of different carbon,silicon based composites as anode materials for lithium-ion batteries and compared their cycling stability and rate capability.The main contents are as follows:1.SiO2/C and Ag/SiO2/C composites:SiO2/C nanocomposites are obtained by direct carbonization of the rice husk at different temperatures under inert atmosphere.When as anode materials for lithium ion batteries,the SiO2/C composite obtained at 900 ℃ exhibits excellent electrochemical performance,the discharge capacity remains 650 mAh g-1 after 150 discharge-charge cycles.Then this sample is further deposited with silver nanoparticles resulted in Ag/SiO2/C composites.When this composite is employed as an anode material for lithium ion batteries,it shows improved electrochemical performance for enhanced electric conductivity because of the existence of silver nanocomposites.2.Si/C and Ag/Si/C composites:The Si/C composite is synthesized by one-pot carbonization/magnesiothermic reduction process and direct carbonization of natural rice husks in inert atmosphere.The discharge capacity of Si/C composite remains 560 mAh g-1 after 180 discharge-charge cycles.Then Si/C composite is further deposited with silver nanoparticles resulted in Ag/Si/C composite.When as anode materials for lithium ion batteries,the two composites shows obvious difference.Ag/Si/C composite displays improved cycling stability and rate capability,which can retain a discharge capacity of 630 mAh g-1 afer 100 cycles.3.Si/TiO2 composite:The Si/TiO2 composite is obtained by carbonization,magnesiothermic reduction of rice husk in sequence,then an titanium dioxide layer is coated onto the obtained Si above by the solvent evaporation method.The composite has a shell core structure with silicon core and titanium dioxide thin layer.Under the protection of the titania as buffer layer,the obtained Si/TiO2 composite shows higher cycling capacity than the pure Si,also,the thicker titania layer resulted in the decline of electrochemical performance,Si/TiO2-5 shows best electrochemical performance and retains a stable discharge capacity of 412.95 mAh g-1 afer 100 charge-discharge cycles at a current density of 100 mA g-1.Silicon based materials as anode materials for lithium ion batteries have excellent research prospects,A series of silicon based composites derived from rice husk are prepared for electrochemical performance testing.The research realized waste utilization,simplification of the synthesis.This work provides guidance for material selection and synthesis route.