Design And Preparation Of Tin Dioxide/Carbon Composite Anode Materials With Novel Nanostructures For Lithium-ion Batteries

The lithium-ion battery?LIBs?has attracted increasing attention due to people attaches great importance to the energy and environmental problems,as well as plays an important role in the development of science and technology,economic growth,social progress and environmental protection.Undoubtedly,improving the performance of LIBs will produce great social and economic value.In the case of a battery,electrode material is one of the determining factors on battery performance.The current LIBs predominantly use graphite as anode materials.Due to graphite anode materials have a lower potential for lithium intercalation?readily leading to lithium platting issues during high current operation?and limited theoretical capacity(372 mAh g^-1),they cannot meet the pressing need for safer power and higher capacity from the coming generation of LIBs.Thus,to improve the development of LIBs,it is highly desirable to develop alternative anode materials to replace the graphite anode.In this thesis,the main work is to enhance electrochemical performances of tin dioxide/carbon?SnO₂/C?composite anode materials by designing and fbricating novel morphologies and structures:1)We prepare two kinds of hollow SnO₂@C nanostructures,namely hollow SnO₂@C spheres and SnO₂@C,by a facile strategy of onepot hydrothermal with subsequent carbonization for the first time.Comparing with general strategies involved templates,the preparation process in our strategy is greatly simplified,and the typical and tedious respective SnO₂ coating,polysaccharides coating and template removal are avoided,instead,the three processes are achieved simultaneously.Thus,our strategy may pave the way for facile preparation of various nanostructures of hollow SnO₂@C composites.2)We prepare a peculiarly nanostructured SnO₂/C composite?denoted as SnO₂@DSC?with a double-shelled carbon support and confined void by hydrothermal method and using hollow carbon spheres as structure support,in which SnO₂ is quasi confined in the void-space between two shells.As a result,the SnO₂@DSC exhibits an excellent cycling performance,delivering a high reversible capacity of 838.2 mAh g^-1 at 200 mA g^-1 even after 500cycles.3)We fabricate an interestingly interconnected quasi-ball-in-ball nanostructure SnO₂/carbon composite,denoted as Cs@void@SnO₂@C,by a simple hydrothermal method and using the carbon spheres as structure support.After 450 cycles,the Cs@void@SnO₂@C delivers a reversible capacity of 793.7 mAh g^-1 at 200 mA g^-1.Even after 1000cycles,the Cs@void@SnO₂@C still delvers a reversible capacity of486.3 mAh g^-1 at a high rate of 1000 mA g^-1.4)We prepare a peculiar nanostructure of SnO₂/Sn@carbon nanospheres dispersed in the interspaces of a three-dimensional SnO₂/Sn@carbon nanowires network composite?denoted as SnO₂/Sn@C?by a facile strategy.As a result,this composite exhibits excellent performance as a potential anode material for lithium ion batteries,delivering a reversible capacity of 678.6 mA h g^-1 at 800 mA g^-1 even after 500 cycles.5)We fabricate a novel nanostructure of encapsulation of SnO₂/Sn nanoparticles into mesoporous carbon nanowires by a facile strategy.Even after 499 cycles,this composite gives a reversible capacity of 949.4 mAh g^-1 at 800 mA g^-1.Its unique architecture should be responsible for the superior performance.6)We design and prepare a tube-in-tube nanostructure,denoted as CNT@void@SnO₂@C,by a facile and novel strategy.The CNT@void@SnO₂@C delivers a reversible capacity of 702.5 mAh g^-1 at200 mA g^-1 after 350 cycles.