Preparation Of Tin Dioxide Anode Material And Its Sodium Storage Performance

Lithium ion batteries（LIBs）have been widely used in electric vehicles and distributed energy systems because of their high discharge voltage,high energy density,long cycle life,and environmental friendliness.However,with the rapid development of the industry,the limited lithium resources on the earth have been unable to meet the growing human demand for energy.As one of the most abundant elements on the earth,sodium has similar physical and chemical properties compared with lithium,and its cost is low.Therefore,sodium ion batteries are expected to replace lithium-ion batteries in the future.Transition metal oxides have a high theoretical capacity and have great application prospects in sodium ion battery anode materials.However,poor conductivity and large volume expansion during cycling limit their wide application.In this paper,we design and modify tin dioxide based material by constructing nanostructures,compounding with carbon materials,coating and doping to explore the corresponding electrochemical performance.The main research results are as follows:（1）Tin oxide nanoflake arrays have been grown on the carbon cloth through hydrothermal method,and then coated with polypyrrole（PPy）through electrodeposition.The design of the nano-sheet structure contributes to the sufficient contact between the material and the electrolyte.The introduction of polypyrrole improves the conductivity of the material and at the same time relieves the volume expansion during the cycle by coating.The prepared material exhibits excellent performance with an initial capacity of 1172.1 mAh g^-11 and a good cycling stability with 85%capacity retention after 300 cycles at 0.1 A g^-11 as a sodium anode.Besides,the involved charge/discharge reactions have been verified by ex situ XRD characterizations.（2）A three-dimensional sponge carbon substrate have been obtained through carbonation of the purchased melamine sponge.Then,a three-dimensional array of molybdenum-doped tin dioxide nanosheets supported by sponge carbon have been synthesized by one-step hydrothermal method.The three-dimensional carbon substrate relieves the volume expansion of the material to some extent,and in the meanwhile,improving the conductivity.Molybdenum doping accelerates the transport of sodium ions.As a result,the as-prpared composite exhibits excellent rate performance with a first capacity of 1143 mAh g^-11 at a current density of 0.1 A g^-1.Even st a high current density of 1 A g^-1,the molybdenum-doped composite displays a high capacity,which is three times larger than that of the undoped composite.