The Fabrication Of Tin-Based Bimetal Oxide Materials And Their Lithium/Sodium Storage Performances

Energy storage is a critical supporting technology in many fields such as information,transportation,healthcare,aerospace and advanced manufacture.Among the electrochemical energy storage devices,the lithium ion batteries?LIBs?were found to be promising candidates,especially for their high energy density.The increasing demand of the society promotes the application of LIBs in many more energy or power demanding devices.However,the rare lithium resource and high cost hinder the further development of LIBs.Therefore,it is significant to explore new energy storage devices.Recently,sodium ion batteries?SIBs?have drawn increasing attention in this field.Because the sodium and lithium elements are in the same main group with similar physical and chemical properties.What's more,there are abundant sodium resources and low-cost sodium salts to support the development of SIBs.The exploration for the suitable anode material is important to the development of both LIBs and SIBs.But it is worth mentioning that the larger size of sodium?radius of 1.02??than lithium?radius of 0.59??makes many anode materials applied in LIBs display poor electrochemical performances when used for SIBs.Among the anode materials,Sn-based materials have obtained much concentration due to their high theoretical specific capacity.But the huge volume changes of active particles during discharge/charge cycling lead to the poor cyclability of Sn-based materials.To improve the cyclability,it is widely applied to combine the Sn-based materials with carbonaceous materials.Apart from that,because the atomically mixed system of bimetal oxides can buffer the volume changes of the electrode material during cycling,the bimetal Sn-based oxides have also drawn decreasing attention in the field of energy storage.In this thesis,the copper tin oxide?CuSnO₃?nanospheres anchored on the interconnected carbon networks?CuSnO₃/graphene/carbon nanotubes,CuSnO₃/GN/CNT?and the flower-like Zn₂SnO₄ were synthesized.And many advanced testing methods were used to characterize the phase and structure of the materials.And the electrochemical performances of the materials were then investigated as the anode of SIBs and LIBs,respectively.The main content and results are as follows:?1?The CuSnO₃/GN/CNT composite were prepared by facilely mixing copper tin hydroxide[CuSn?OH?₆]with graphene oxide and carbon nanotubes,followed by a freeze-drying treatment and calcination.?2?The CuSnO₃/GN/CNT composite was assembled into lithium ion and sodium ion half cells as the anode material.The composite shows good electrochemical performances.As the anode of LIBs,it delivers a reversible capacity of 1087.4 mAh g^-1 at the current density of 200 mA g^-1,which was maintained at 869.9 mA g^-1 after 50cycles.In addition,as the anode of SIBs,it shows a reversible capacity of 310.8 mAh g^-11 at 100 mA g^-1 after 55 cycles,corresponding to a capacity retention of 90.1%.The electrochemical analysis results confirmed that the cover of carbon networks could relieve the volume variation and enhance the electric conductivity of the material during electrochemical cycling.In addition,the metallic Cu generated during the first discharge process could improve the conductivity of the material in the following discharge/charge cycling.All the factors above lead to the good electrochemical performances of the composite.?3?The high-purity Zn₂SnO₄ nanoflowers composed of nanorods were synthesized by a facile hydrothermal process.And the electrochemical performances of the materials were then investigated as the anode of LIBs and SIBs,respectively.Compared with other bare Sn-based materials,Zn₂SnO₄ nanoflowers exhibit a better cycling performance for both LIBs?730.5 mAh g^-11 after 80 cycles?and SIBs(207.3mAh g^-1 after 80 cycles),indicating that the Zn₂SnO₄ nanoflowers are promising in the field of energy storage,...