Preparation And Electrochemical Properties Of SnO₂/Biomass Carbon Composites

With the rapid development of the automotive and electronics field,the new energy lithium battery industry has entered a period of rapid development.At present,graphite is still the main anode material for commercial lithium-ion batteries?LIBs?,but its low specific capacity has gradually failed to meet market demand.Therefore,the focus of LIBs research will shift to high coulomb efficiency,high cycle performance and low cost in future.SnO₂stands out from a wide range of anode materials due to its high energy density and excellent safety properties as well as novel conversion mechanisms.As a potential metal oxide alternative to carbon materials,SnO₂ has a standard specific capacity of up to 782 mAhg^-1.However,as an anode material,it has also metal oxide common defects,such as poor electrical conductivity,large volume expansion ratio,resulting in the electrochemical performance can not reach a desired value.In view of the above problems,rice husks and corn stalks were used as raw materials to prepare amorphous carbon in this paper,which not only reduced the experimental cost,but eased environmental pollution.Amorphous carbon can decrease the negative effects caused by defects such as volume expansion as a matrix supported by SnO₂.The physical characterization and electrochemical properties of the corresponding materials were tested.The main research contents and results are as follows:?1?The rice husk was treated by a method of caustic activation to obtain rice husk cellulose.Graphite oxide?GO?was prepared by a modified Hummers method.GO,rice husk cellulose and SnCl₂·2H₂O were treated to obtain a special multi-stage structure of rice husk carbon@SnO₂@graphene composite by one-step hydrothermal method.The effects of different hydrothermal conditions and different calcination temperatures on the electrochemical properties of the composites were investigated.The text results show that when the hydrothermal time is 36 h and the calcination temperature is 500?,the electrochemical performance is the best.The specific discharge capacity stabilizes at 1206.9mAhg^-1 after charging and discharging for 100 cycles at rate of 0.2C,which far exceeds the standard specific capacity of SnO₂.?2?The corn stalk was treated by solid phase activation to obtain porous corn stalk carbon?CSC?.SnO₂ was deposited in situ on the CSC to obtain a three-dimensional composite material by hydrothermal method.The optimum process parameters were obtained by exploring the effects of different hydrothermal conditions and mass ratios on the morphology and electrochemical properties of the composites.When the water temperature is 180?and the mass ratio of CSC to SnCl₂·2H₂O is 1:1,the material shows the more abundant pore structure and the best performance.The specific discharge capacity after cycling for 100cycles is as high as 691 mAhg^-1 at rate of 0.2C.?3?Using porous CSC and GO as carbon source,three-dimensional CSC-SnO₂-RGO composite was prepared by one-step hydrothermal method.The composite was characterized and tested electrochemical performance as an anode material.It delivers a discharge capacity of 978.7 mAhg^-1 at 0.2C after 100 cycles and high specific capacity of 232.5 mAhg^-1 at 5C,which shows excellent cycle stability.