| Energy and environmental problems have been hindering the growth of economyand development of society. Modern governments of countries have put priority inlifting energy efficiency. Lithium-ion secondary batteries showed attractive propertieslike high output voltage, high specific energy per volume or mass, long life, nomemory effect, environment-friendly processing. Therefore the lithium ion secondarybatteries occupied the rechargeable battery high-end market since last decade.Nanotechnology has developed rapidly and the combination of nanotechnology andlithium ion battery technology would definitely lead to next generation of lithium ionbattery. Nanostructured lithium ion batteries electrode materials have larger surfacearea, enhanced storage kinetics, enhanced structural stability, and new lithium ionstorage mechanism, etc. The inherent performance is greatly improved compared withthe conventional electrode materials. In addition, the electrode materials are alsowidely used in the field of electrochemical sensors.This thesis includes three major works:(1) porous template-synthesizedLiTi2(PO4)3nanowire array based electrode materials for lithium ion batteries;(2)preparation of LiTi2(PO4)3hierarchical porous materials with cotton template forlithium ion batteries;(3) synthesis of hierarchical Cu/C composite microspheres,evolution of microstructure, and using as glucose sensor electrode materials.Nanowire structure have many advantages as lithium ion battery electrodematerials, such as reducing the diffusion distance of lithium ions; mitigating thevolume expansion and chalking due to the insertion of lithium ion into the electrodematerials; improving the electrical conductivity. We use sol-gel method, and optimizethe experimental condition to prepare the LTP precursor sol, immerse thecommercially available polycarbonate filter, control the heat treatment temperatureand atmosphere to anneal, single crystal LTP nanowires arrays were synthesized forthe first time. The LTP nanowires were used as battery electrode materials directly,without any conductive agent and binder, the electrochemical performance wasimproved to some extent. The results prove that nanowire structural electrodematerials could improve the poor electrical conductivity of LTP itself as lithium ionbattery electrode materials. The TEM result showed two types of nanowires, perfect single crystals and quasi-mono-crystalline with rich stacking faults. Furtherinvestigation needs to be done.Due to the limited sample mass of LTP nanowires, it is difficult to obtain theirelectrochemical capacity accurately. Therefore, it is necessary to prepare other form ofLTP samples. The micro-scale porous materials have a large specific surface area,easy to prepare, and the performance could be improved, etc. We use cotton, paper,fabric, cloth, and silk as template, combined with a sol-gel method to prepare thesamples. By immersing the template into precursor sol and post-heating process,hierarchical porous pure phase LTP materials were prepared at a moderately lowtemperature. We developed two routes to prepare the LTP electrode materials,(1)annealing under inert atmosphere to produce flexible battery electrode materials afterthe template carbonized,(2) annealing under oxidizing atmosphere to burn out thetemplate and then carrying out a carbon coating process. We found that theas-obtained electrode materials showed approximately the theoretical capacity, abetter rate capability, compared with the porous materials without carbon coatingwhich have no capacity, a pair of new peaks in the CV curve, and the presence of alarge number of stacking fault in the materials which were also found in the singlecrystal LTP nanowires from the HRTEM experimental result.Besides one component electrode materials, nano composite is also beingconsidered. We use ascorbic acid and copper nitrate as raw materials, carbonmicrospheres were synthesized by a hydrothermal procedure. Interestingly, afterannealing under inert atmosphere or electron beam irradiation in a TEM chamber,copper nanoparticles are grown in situ from the as-obtained carbonaceousmicrospheres, and the particle size and crystal shape could be well controlled by theexperimental parameters from the experimental result, such as the annealingtemperature. The annealed copper/carbon composite microspheres were used as theactive materials to modify the glass carbon electrode, and tested as an electrochemicalglucose sensor. Changing the concentration of ascorbic and copper nitrate, withoutany soluble oxalate or oxalic acid, copper oxalate microspheres could be obtained,which changed to porous copper oxide microspheres after annealing in air.In summary, we use nano materials preparation technology, microstructureanalysis, electrochemical study to do the research. We obtained single crystal LTPnanowires and micro-scale LTP porous materials. We found the stacking faults defect from the LTP materials, and obtained a better electrochemical performance. Wedeveloped a new route to prepare LTP electrode materials using sol-gel method andtemplate-method. Nanowire electrode could be used as nanobattery for in situ TEMexperiment; By the same way, TiP2O7and Li4Ti5O12could also be synthesized aslithium ion battery electrode materials; Other hard template could be utilized toprepare titanium based lithium ion battery electrode materials with differentmorphologies and structures; The carbon microspheres synthesized by hydrothermalroute, could expand dramatically after electron beam converged rapidly under TEM. |
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