Preparation And Electrochemical Properties Of SnO₂/SiO₂/rGO Composite

The main negative electrode materials for lithium ion battery are graphite materials, but their discharge/charge specific capacity is relatively low (The theoretical capacity is 372 mAh/g), which is more and more difficult to satisfy the development of electric vehicle. SnO2 has a specific capacity as high as 782 mAh/g. However, SnO2 suffer severe volume change during the process of discharge and charge, making the electrode pulverization and falling off. The cycle performance of the battery is thus worse. Moreover, the poor conductivity of SnO2 is another reason for the inferior electrochemical performance. Therefore it is meaningful to search an effective way to ease the volume change and improve the conductivity to make the electrochemical performance of SnO2 better.In order to improve the cycle performance and conductivity of SnO2 material, in this article through adding SiO2 or rGO in SnO2 material, compounds were prepared and. Their structure, morphology and electrochemical performance have been tested, the results of which are as followed.(1) First, in this article SiO2 powder was prepared by a water bath method. Through regulating the experiment conditions, SiO2 with different sizes was prepared. The sizes can fall into 100 nm,300 nm and 800 nm. After reacting for 6 h under the temperature of 30℃, the particles are spherical and the size is of about 100 nm and the electrochemical performance of this sample is better. Under the current density of 100 mA/g, the discharge capacity is 66 mAh/g.(2) SnO2@SiO2 compound was prepared by a facile hydrothermal method. The SiO2 used here is prepared according to (1), and the sizes are 100 nm and 800 nm. Through regulating the experiment conditions, SnO2@SiO2 compounds with different structure and morphology were prepared. After reacting for 12 h under the temperature of 150℃, the structure and morphology are better, and the sample containing the SiO2 of 100 nm has better electrochemical performance. Under the current density of 100 mA/g, the initial discharge and charge capacity are 531 mAh/g and 281 mAh/g respectively. After 50 cycles, the discharge and charge capacity are 243.56 mAh/g and 238.12 mAh/g respectively, while Under the current density of 1000 mA/g, the discharge and charge capacity are 114 mAh/g and 113 mAh/g respectively.(3) SnO2/rGO compound was prepared by a facile hydrothermal method. Through regulating the experiment conditions, SnO2/rGO compounds with different structure and morphology were prepared. After reacting for 12 h under the temperature of 160℃, the structure and morphology are better. Under the current density of 100 mA/g, the initial discharge and charge capacity are 2132 mAh/g and 1158 mAh/g respectively. After 100 cycles, the discharge capacity is 455 mAh/g and under the current density of 1000 mA/g, the discharge and charge capacity are 450 mAh/g and 435 mAh/g respectively.(4) SnO2@SiO2/rGO compound was prepared by a facile hydrothermal method. Through regulating the experiment conditions, SnO2@SiO2/rGO compounds with different structure and morphology were prepared. After reacting for 12 h under the temperature of 160℃, the structure and morphology are better. The SiO2 particles and rGO sheets formed a kind of sandwich layer construction, while the SnO2 nanoparticles dispersed on the surface of SiO2 particles and rGO sheets to form a coating and layer construction. Under the current density of 100 mA/g, the initial discharge and charge capacity are 1548 mAh/g and 818 mAh/g respectively. After 100 cycles, the discharge capacity is 590 mAh/g and under the current density of 1000 mA/g, the discharge capacity is 410 mAh/g.