Preparation And Modification Of Carbon Aerogel-tin Oxide Composite And Its Lithium Storage Properties

As a new type of energy storage device,lithium ion batteries are used more and more frequently in people’s daily lives.The traditional anode materials of lithium-ion batteries are mostly graphite materials,which have a low specific capacity and cannot meet the market’s demand for high-capacity.Tin oxide materials are generally believed to replace graphite anode materials due to their high capacity.However,the negative electrode material of tin oxide has poor conductivity.When lithium is intercalated,it is easy to cause volume expansion to cause powdering and shedding.Tin oxide particles are prone to agglomeration in the electrode material,which causes the capacity of tin oxide negative electrode to deteriorate seriously during use.In response to the above problems of tin oxide anode materials,the specific surface area of the carbon aerogel is improved firstly,and then two different methods are used to prepare the high specific surface carbon aerogel and tin oxide composites,and finally the composites are coated with polypyrrole to improve the electrochemical properties of tin oxide.The specific research contents are as follows:（1）In order to increase the specific surface area of carbon aerogels,glucose and paraffin are used as raw materials in this paper to prepare carbon aerogels by inverse emulsion polymerization and characterize their structures.The results show that the prepared carbon aerogel has a porous carbon structure,and it can be seen from the XRD that it is an amorphous carbon structure.Potassium hydroxide is selected as the activator to increase its specific surface area.The effects of different impregnation ratios on the specific surface area of the carbon aerogel are compared.The study found that when the impregnation ratio is 3,the specific surface area of carbon aerogel is the highest,which is1792.3 m² g^-1.The high specific surface area can provide more tin dioxide recombination sites,which is helpful to improve the conductivity of the composite material.（2）Two different methods,hydrothermal method and vacuum impregnation method,are used to prepare high specific surface carbon aerogel-tin oxide composite materials.The results show that the loading of tin oxide in the composite material prepared by the vacuum impregnation method is as high as 38.8 wt%,and the nano tin oxide particles are evenly dispersed in the pores of the high specific surface carbon aerogel.At a current density of 0.1 A g^-1,the composite material prepared by the hydrothermal method as the electrode material has a first discharge specific capacity of 1489 m Ah g^-1.However,after50 cycles,the capacity decays fast.The composite material prepared by vacuum impregnation as the electrode material has a first discharge specific capacity of 1768.5m Ah g^-1,and the specific discharge capacity after 50 cycles is still 209.4 m Ah g^-1.It is found by comparison that the composite material prepared by vacuum impregnation has better electrochemical performance.（3）In situ chemical oxidation polymerization is used to coat polypyrrole on the surface of carbon aerogel-tin oxide composite prepared by vacuum impregnation method.Results show that the ratio table carbon aerogel and pyrrole monomer mass ratio of 8,12,16,its circulation after 50 times in lithium ion battery discharge specific capacity are314.7 m Ah g^-1,287.3 m Ah g^-1 and 275.8 m Ah g^-1,polypyrrole coated on composites have good modification effect,when the ratio table carbon aerogel and pyrrole mass ratio is 8,overall material of electrochemical performance is the best.