Preparation Of Carbon Aerogel/SnO₂ Composite And Its Sodium Storage Properties

With the continuous development of society and the continuous advancement of economic technology,the excessive use of fossil energy by humans has caused a sharp decrease,and people need to develop new energy technologies.Lithium-ion batteries?LIBs?have many advantages and are used in various fields.However,lithium metal is expensive and unevenly distributed,which limits its development.Sodium metal is abundant in reserves and sodium and lithium are in the same main group,and their chemical properties are very similar,so they can be used as a potential supplement and substitute.Tin dioxide?SnO₂?has a relatively high theoretical specific capacity(?667mAh·g^-1)in sodium-ion batteries?SIBs?.However,its poor conductivity and easy volume expansion during cycling restrict its development.Carbon aerogel?CA?is a new type of porous carbon material,which has a high specific surface area and good electrical conductivity.Recombining it with SnO₂ can improve the shortcomings of volume expansion and low conductivity of SnO₂ directly used as the anode electrode of SIBs.The main research work of this paper includes the following aspects:?1?First,CA was prepared by a new method with simple process,green environmental protection and low cost,and its morphology and structure were tested.The results showed that the overall CA obtained was a honeycomb shape with a specific surface area of up to 1760 m²·g^-1.The electrochemical performance of CA as an anode electrode material for SIBs was analyzed,and the specific discharge capacity can maintain a discharge specific capacity of 106.3 mAh·g^-1 at a current density of 0.05 A·g^-1after 50 cycles.At the same time,the purchased SnO₂ was tested for electrochemical performance such as microstructure,cycle performance and rate performance.?2?Based on the poor electrochemical performance of SnO₂ and CA,the ball milling method was used to prepare CA/SnO₂ composite materials,so that CA and SnO₂ were fully compounded.SEM test results showed that SnO₂ was distributed in the skeleton of carbon aerogel;The discharge cycle test shows that the CA/SnO₂ composite can maintain a discharge specific capacity of 193.7 mAh·g^-1 at a current density of 0.05 A·g^-1 after 50cycles,which improves the electrochemical performance compared to SnO₂.?3?In order to overcome the disadvantages of the CA/SnO₂ composite material prepared by the ball milling method,it is easy to cause the crushing of the CA pore structure and the larger SnO₂ particles.The CA/SnO₂ composite material was prepared by vacuum impregnation.SEM and BET test results showed that the prepared SnO₂ particles had a size of approximately 20 nm,and the porous structure of CA remained intact.Some SnO₂ particles filled the pores of CA.It shows that the CA/SnO₂ composite material prepared by vacuum impregnation can maintain a discharge specific capacity of 203.9mAh·g^-1 at a current density of 0.05 A·g^-1 after 100 cycles,and the volume expansion during the SnO₂ cycle is relieved to a certain extent.?4?The vacuum impregnation method has a long preparation time and low efficiency.Therefore,a simple hydrothermal method was used to prepare the CA/SnO₂ composite material.The TEM test results showed that the SnO₂ size was uniformly distributed at the nanometer level,and some SnO₂ particles were filled in the pores of the CA.The results of electrochemical tests show that the CA/SnO₂composite prepared by hydrothermal method can maintain the discharge specific capacity of 235 mAh·g^-1 at a current density of 0.05 A·g^-1 after 100 cycles,which is superior to SnO₂.