Research On Energy Storage Properties Of Tin-based Composites With Graphene

The sodium ion batteries have attracted increasing attention because of the advantages of high specific capacity,wide operating temperature range and long cycle life.Electrode materials play a decisive role in the performance of sodium ion batteries,especially the negative electrode materials.At present,the anode materials of sodium batteries are mostly hard carbon,but the capacity of hard carbon is low and can not meet the application of large-scale storage system.Therefore,it is very important to study the negative electrode materials of sodium ion batteries.Our work is mainly based on the study of tin-based anode materials,which shows a great advantages compared with carbon-based materials.However,there are several unavoidable problems for tin-based compounds,namely the low conductivity and the large volume expansion during the charge and discharge process.In order to alleviate the above problems,SnO₂/GF nanorod arrays and SnS₂/VG nanosheet arrays structure are designed.In this paper,SnO₂/GF nanorod arrays and SnS₂/VG nanosheet arrays structure were successfully prepared by hydrothermal method and solvothermal method,respectively.The addition of GF and VG can significantly increase the conductivity of the tin-based compounds,while the formation of the three-dimensional array structure can act as a buffer matrix to suppress the volume expansion during charging and discharging.Meanwhile,the array structure can effectively increase the specific surface area of the material and provide more active sites for the insertion of sodium ions/lithium ions.SnO₂/GF nanorod arrays the initial discharge specific capacity is445mAh·g^-11 as the anode materials for sodium-ion batteries at the current density of40mA·g^-1,The coulombic efficiency is close to 100%,and its cycle performance and rate performance are better than lithium-ion batteries.The SnS₂/VG nanosheet arrays electrode is used as a anode of sodium ion batteries,the discharge capacity is up to750mAh·g^-1 at the first cycle,it is much higher than lithium batteries.besides,the rate performance is also superior.In addition,we have compared the AC impedance of pure nanoparticles and composites.the results show that the impedance of the composites is far less than that of the pure material,the impedance of the electrode materials have obvious decreases,and suggests that the addition of GF and VG on material performance improvement has played a crucial role.