The Preparation And Performance Of Metal Oxide/Carbon Nanocomposite As Lithium Ion Battery Anodes

With the development of science and technology rapidly, the growing demand oflithium-ion batteries, such as: low consumption, no memory effect, high energydensity, long cycle life, high efficiency and so on. The function of anode material forlithium-ion battery is an important way to elevating circulation property and capacity.However, the theory capacity of current commercial graphite is so low (372mAh/g),it is limited to their practice application by certain restrictions. So the study of newmaterials instead of graphite carbon anode material is very important. To achieve highpower and energy density, nano-sized transition metal oxides have been used as anodematerials for LIBs because their specific capacities are about three times higher thanthose of commercial graphite (372mA h g-1). However, the practical application oftransition metal oxides has be frustrated due to the large volumeexpansion–contraction and severe particle aggregation, which always leads toelectrode pulverization and loss of inter-particle contact, a large capacity loss andpoor cycling stability. To overcome these limitations, an effective way to enhance theelectrochemical performance is to combine transition metal oxides with carbon andpreparing nano-materials. Till now, Compared to the corresponding bulk materials,nanoscale materials introduce innovative reaction mechanisms and provide shorter iondiffusion paths and larger electrode/electrolyte contact areas in lithium ion batteries,which improve the electrochemical performance in terms of reversible capacity, highcurrent charge/discharge ability, and cycling stability. First is the use of nanosizeparticles of the metals or oxides or other compounds, which will enable them toabsorb some of the volume changes because of the smaller number of atoms presentin the nanograins and the inherent large surface area of the nanosize particles.Therefore, more effort is committed to the synthesis of nanoparticles structure. Thecarbon-based materials are one of the best choices for supporting nano-sized metallicparticles in the electrode for lithium ion battery. It is expected that this carbon wouldact as a barrier to prevent the aggregation of transition metal oxides during Li+insertion/extraction, and mitigate the pulverization problem and improve the cyclicretention. Therefore, a good thium storage property of transition metal oxide/carboncomposite material is a new research direction. This thesis work mainly keeps thefocuses on the synthesis of transition metal oxide/carbon nanocomposite and its application in lithium ion storage as anode, the work can be specified into followingthree aspects:1. The N-doped porous carbon was synthesis by calcining biological carbonmaterials, to form the graphitization of carbon. Different particle size of Co3O4nanoparticles (NPs)/N-doped PC nanocomposites were successfully synthesized via afacile hydrothermal method using natural porous crawfish shells as both the carbonsource. The structure and morphology of the material were characterized using SEM.Since the N-doped PC has a large number of nitrogen functional groups, which leadsto deposit Co3O4on them directly. The crawfish shell is the food waste, which asprecursor is economic and environmentally friendly. The N-doped PC-Co3O4nanocomposites as a low-cost anode material for LIBs exhibited high lithiationcapacity, good rate capability and excellent cycle performance.2. In the second part, we regarded Prussian blue as the precursor which coatedwith dopamine and synthesized complexes of nanometer structure size with uniformmorphology. We achieved the optimum calcination temperature of PB-DPAcomposites, the cycle performance of which is at650℃for1h.3. We have acted Zn-Fe-ZIF as precursor, using Fe and Zn metal to formZn-Fe-ZIF. Then through the way of calcination Zn-Fe-ZIF is aim to synthesis twokinds of metal oxide mixed material which is are uniformly mixed,nanohetero-junction, porous, active/synergertic materials, larger specific surface area,can be observed by SEM. Previous studies have demonstrated that metal–organicframeworks (MOFs) with their unique porous structure can act as both templates andprecursors for the preparation of porous carbon materials. The result of ZnO/Fe3O4/Cis characteristiced by all methods.