چكيده به لاتين
In the present study, nanomaterials of NCM were synthesized using combustion synthesis method. The production of combustion was used in this research due to the effectiveness an cheapness of nanoparticles production. In order to study the grain growth of nanomaterials of NCM, the material was calcified at temperatures 750, 850, and 950 °C at 5, 7.5, 10, 12.5, and 15 hours, respectively. Using the analysis of the results of XRD and FESEM, the diagram of Ln(crystal diameter) calculated according to Ln(time), was drawn for the annealed sample at 750, 850, and 950˚C temperatures, and the time points 7.5, 10, 12.5, and 15 hours in the Microsoft Excel software. In the following, using the linear equation given by this software for each line, the slope of the line (n) obtained for each line. The value of n indicates the growth of the most crystals has occurred with diffusion through the boundary of the particles, which is the dominant grain growth mechanism of the NCM material . The best synthesized sample at this stage was a calcified sample at 850° C for 15 hours. In this sample, the grain size was estimated to be in the range 100 nm to 300 nm. In this sample, the value of I(003)/I(104) is 1.3036. Subsequently, adding 3% weight to the optimal NCM material in the previous step and analyzing the XRD data indicated a decrease in the cation mixing and an improvement in the layer structure. Also, the peak intensity of the I(003)/I(104) improved compared to the previous sample and was equal to 1.4. Charging-discharging analysis performing for the NCM sample with 3% additional lithium resulted in the initial charge and discharge capacity values of 214.58 mAh/g and 179.17mAh/g at a 0.05C rate, respectively. Also, the obtained reversible capacity for this sample, after the cycling operation at different C rates,, is 95% of the initial capacity at the 0.01C rate. This sample showed an irreversible capacity of 10.36% after 50 cycles of recharging-discharging. In the next step, the suspension of graphene oxide produced by microwave ultraviolet radiation was converted to reducted graphene oxide. Composite RGO-NCM was prepared with weight percentages of 1, 3 and 5. Charging-discharging processes for the RGO-NCM composite samples led to an improvement in initial discharging capacity, reversible capacity and reduce capacity loss during the cycling process, for all graphene samples. The sample with 5% reducted graphene oxide had an initial charge and discharge capacity of 292.76 and 198.14, respectively. Also, the reversible capacity during the cycling process at different C rates equaled to 99.675% of the initial capacity at a 0.1C rate. For this sample, the irreversible capacity during the cycling process at 1C rate was 95.69% of the initial discharge capacity. Using the results of EIS analysis, it was observed that adding RGO and improving the electrical conductivity in the composite material of RGO-NCM led to a reduced charge transfer resistance.
Keywords: Combustion synthesis, Grain growth, Lithium ion battery, RGO-NCM Nanocomposite
