| Carbon nanotubes?CNTs?and their films have wide application in many fileds,including electromagnetic shielding and lithium ion batteries?LIBs?.However,the electrical conductivity of the obtained CNTs and their films would be decreased sharply due to impurities generated in the preparation process.Therefore,improving the electrical conductivity of the CNTs becames a significant factor for their practical applications.?1?In this thesis,fluffy CNTs sponges were obtained through the continuums were assemblied.After being mechanical pressed,CNTs macro film?CMF?will be prepared using Cu foil with formal microscopic structure as substrate.The surface roughness of the CMFs was checked by three-dimensional surface profiler.In electrodeposition,the electrical current on the CNTs will be distrubited and increased homogenous for formal surface of the film.The results will accelerate the progress of the electrodeposition reaction.?2?Based on the formal surface of the CMF,a thin Cu layer of tightly deposited on the the substrate CMF was obtained by electrodeposition method.The sheet resistance of the CMF/Cu composite film was tested by a four-probe system.The results indicated the resistivity of the film was reduced from the initial 8.3×10-6?m to 6.25×10-8?m,and the electrical conductivity was increased from the initial 1.2×105 S/m to 1.6×107 S/m.According to the theories of the electromagnetic shielding,the increased electrical conductivity of the film will demonstrate high electromagnetic interference?EMI?shielding effectiveness?SE?of the composite.After measured by a vector network analyzer?VNA?,it can be seen that the EMI SE of the CMF/Cu composite film was improved from 34 dB to 64 dB in the frequency range from 2.6 to 26.5 GHz.?3?CMF/Ni and CMF/Al deposition composite films were also prepared by electrodeposition and magnetron sputtering method,respectively.The lithium ion batteries?LIBs?based on the CMF/Ni as anode current collector and CMF/Al as cathode current collector were further been studied.The LTO/Li half-cell based on the CMF/Ni composite film displayed a significantly improve specific capacity of about 100 mAh/g at a C-rate of 30C.Due to the improving electrical conductivity of the current collectors,the transference efficiency of electrons in the LIBs will be increased.And the LCO/LTO full cells based on CMF/metal composite film also shown better performance than that based on traditional metals or CMFs current collectors.In addition,the electrochemical impedance spectroscopy?EIS?of the full batteries were also tested by an electrochemical workstation,and it can be found that the internal impedance was obviously decreased and thereby the output voltage was significantly increased.Furthermore,the active materials could be coated tightly on the CNT/metal composite films for porous surface of the current collectors that similar to original CMFs.The foldable electrode demonstrates stable electrochemical performance of the assembled LIB even after repeated fold. |
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