Novel Inorganic Oxides-Polypyrrole Nanoarchitectures:Synthesis And Their Electrochemical Performances

Recently，much attention has been paid to develop lithium ion batteries withboth high power and high energy. Anode materials play a key role to the performance of a whole battery. Graphite is currently the main choice in commercial lithium ion batteries. However，its theoretical capacity（372mAh/g）restricts the further increase of the energy density of the batteries. In the recent years，transition-metal oxides （such as Fe₂O₃、SnO₂），with a capacity about two times of that for graphite，has become promising candidates for the anode electrode materials. However，the huge volume changes during Li-ion insertion/extraction result in a quicklyunacceptable capacity fading.In this thesis，we modified Fe₂O₃and SnO₂anode materials using conductingPPy（polypyrrole）with the aims to both increase their conductivity and relive their volume changes. Based on this ideas，we had done the following two work：First，we proposed a surfactant directed in situ polymerization method to anchor PPy nanoparticles on Fe₂O₃nanotube （Fe₂O₃NT-ppy anchored）In this system，the surfactant （PVP），absorbed in Fe₂O₃nanotube，acts as nucleation seeds to induce the pyrrole polymerized on the surface of Fe₂O₃nanotube. However，the composite of Fe₂O₃-PPy nanotube （Fe₂O₃NT-ppy aggregated）prepared by not adding surfactant are disorderly and unsystematic. When tested as anode materials forlithium ion batteries，the Fe₂O₃NT-ppy anchored show the best performance and it can still retain a capacity of712mAh/g after30cycles.Second，we fabricated CNT@SnO₂，SnO₂@CNT@SnO₂and SnO₂@CNT@SnO₂@PPy coaxial nanocables by a simple one-pot chemical solution method. The synthesis consists of coating and filling CNTs with SnO₂nanoparticles，followed bychemical polymerization of PPy on the surface of just generated SnO₂coating layer. TEM images reveal their typical architectures. It was found that the SnO₂@C NT@SnO₂@PPy coaxial nanocables deliver a high discharge capacity of about600mAh/g even after30cycles and the Coulombic efficiency remains close to100%.