Preparation And Electrochemical Performance Study Of Carbon-based Composite Electrode For Lithium Batteries

As a successful electrochemical rechargeable device,lithium battery can make the storage and utilization of energy more effective,which is widely used in power-consuming equipment,such as mobile devices,electric cars and home appliances.The structure of current collector and electrode has a significant effect on the mechanical strength of electrode,the efficiency of electron's transfer/collection,and the electrochemical performance of batteries.In order to make the performance of active materials of lithium ion batteries?LIBs?and lithium sulfur?Li-S?batteries fully display,a carbon-based composite electrode with the optimized structural design of current collector and electrode was fabricated in this thesis by using high-performance functional carbon materials.The design and preparation of the structure for current collectors and electrodes in carbon-based composite electrode,the performance evaluation of functional current collector and electrode,and its influence on the electrochemical performance of batteries were systematically studied.Specifically,the main contents include the following:?1?Preparation of the layered CuO/MCMB electrode and study the performance of CuO nanoflowersA layered carbon-based composite electrode composed of a honeycomb-inspired copper current collector,an interlayer of CuO nanoflowers,and an active layer of MCMB was prepared by combining photolithography,solution immersion,and coating processes.The tests of X-ray diffraction spectrometry?XRD?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?,transmission electron microscope?TEM?and electrochemical performance were used to study the morphology and conductivity of electrode,reveal the optimization mechanism of layered electrode structure on the traditional mesocarbon microbead graphite powders?MCMB?based electrode.The tests found that the specific capacity,rate performance and impedance characteristics of the CuO/MCMB carbon-based composite electrode were significantly improved compared to the traditional commercial MCMB electrode.?2?Preparation and performance test of 3D porous CuO@MWCNT electrodeThe Cu layer,multi-wall carbon nanotubes?MWCNT?layer and CuO nanoflowers were sequentially deposited on a nickel foam substrate by combining electroplating process,electrophoretic deposition process and solution immersion,finally forming the 3D porous CuO@MWCNT binder-free carbon-based composite electrode with the integrated structure of CuO nanoflower and Cu@MWCNT composite current collector.In the meanwhile,we analyzed the composition and micromorphology of composite electrode.The tests showed that the CuO@MWCNT carbon-based composite electrode exhibited a stable electrode structure and excellent electrochemical performance under the effect of the functionalized current collector and electrode.?3?Preparation and performance test of the sandwich-structural electrodeThe MWCNT slurry,S/C active slurry and MWCNT/Li₄Ti₅O₁₂ composite slurry were sequentially coated on the aluminum foil by a facile layer-by-layer slurry coating process,fabricating a sandwich-structural carbon-based composite electrode for Li-S batteries.We also studied the properties of electrode,such as its mechanical strength,adsorption effect of lithium polysulfide and electrochemical performance.With the combined effect of the micro-cracked current collector and the sandwiched electrode structure,the Li-S battery based on the carbon-based composite electrode had an improved EIS characteristics,safety performance,cycle performance,and rate performance.Even with a higher sulfur loading,the Li-S battery also exhibited the enhanced charge-discharged specific capacity and cyclic stability.