3.4. Electrochemical performance of Li1.2Ni0.13Co0.13Mn0.54O2
3.4.1. Electrochemical charge/discharge behavior
Figure 9 (a-d) shows the charge/discharge profiles of four Li1.2Ni0.13Co0.13Mn0.54O2 electrodes (EV, CA/EDTA, CA and EDTA) cycled at 0.1C between 2.0 and 4.8 V, while Fig. 9(e) depicts the initial charge/discharge profiles of four Li1.2Ni0.13Co0.13Mn0.54O2 electrodes under the same conditions. All the initial charge/discharge profiles show the same general features. All the initial charge curves exhibit the turning point (i.e. sloping curve below 4.5 V and a long plateau around 4.5 V). The existence of a turning point not only differentiates between the extractions of Li ions from layered (LiNi1/3Co1/3Mn1/3O2) and monoclinic (Li2MnO3)-like …show more content…
as the rate capability increases the performance of Li-ion battery increases and can be used for high power appliances. In order to demonstrate the rate capabilities of the synthesized Li1.2Ni0.13Co0.13Mn0.54O2 54O2 electrodes (SA, EDTA, CA/EDTA and EV), the cells were cycled in the volte range 2.0-4.8V at various current rates from 0.1C to 3.0 C, and the results are shown in Fig. 11. It can be seen from Fig.2 that, the discharge capacity of all electrodes gradually decreases to different degree, which attributed to increasing the polarization of the electrodes at high current rate. This is may be due to reduction of the intercalation time of lithium ions (Li+) into the crystal lattice, therefore, only the active material surface participate in the reaction [60]. Among the four electrodes under investigations, EDTA and CA exhibited good electrochemical behavior with improved cycleability even at high current rate. At current rate 3.0C, the two electrodes were possessed average discharge capacity 136.3 and 123.5 mAh/g, respectively. Going back to C/10, EDTA and CA electrodes can retain discharge capacities of 245.4 and 238.4 mAh/g, which represent 91.7 and 91% of the initial discharge capacity obtained in C/10 rate used at the begining. In general rate capabilities go in the same order EDTA > CA > CA/EDTA > EV as obtained in capacity …show more content…
Fig. 12 a and b shows the Nyquist plots of the fresh and after 5th cycles for Li1.2Ni0.13Co0.13Mn0.54O2 electrodes, respectively, where as the shapes of the Nyquist plots are similar. All the EIS curves exhibit one semicircle in the high frequency region which represents interfacial charge transfer resistance between the surface film and the active cathode mass (Rct). While, the sloping line at the low frequency region represents Warburg resistance, which related to the lithium ion diffusion in the bulk materials
3.4.1. Electrochemical charge/discharge behavior
Figure 9 (a-d) shows the charge/discharge profiles of four Li1.2Ni0.13Co0.13Mn0.54O2 electrodes (EV, CA/EDTA, CA and EDTA) cycled at 0.1C between 2.0 and 4.8 V, while Fig. 9(e) depicts the initial charge/discharge profiles of four Li1.2Ni0.13Co0.13Mn0.54O2 electrodes under the same conditions. All the initial charge/discharge profiles show the same general features. All the initial charge curves exhibit the turning point (i.e. sloping curve below 4.5 V and a long plateau around 4.5 V). The existence of a turning point not only differentiates between the extractions of Li ions from layered (LiNi1/3Co1/3Mn1/3O2) and monoclinic (Li2MnO3)-like …show more content…
as the rate capability increases the performance of Li-ion battery increases and can be used for high power appliances. In order to demonstrate the rate capabilities of the synthesized Li1.2Ni0.13Co0.13Mn0.54O2 54O2 electrodes (SA, EDTA, CA/EDTA and EV), the cells were cycled in the volte range 2.0-4.8V at various current rates from 0.1C to 3.0 C, and the results are shown in Fig. 11. It can be seen from Fig.2 that, the discharge capacity of all electrodes gradually decreases to different degree, which attributed to increasing the polarization of the electrodes at high current rate. This is may be due to reduction of the intercalation time of lithium ions (Li+) into the crystal lattice, therefore, only the active material surface participate in the reaction [60]. Among the four electrodes under investigations, EDTA and CA exhibited good electrochemical behavior with improved cycleability even at high current rate. At current rate 3.0C, the two electrodes were possessed average discharge capacity 136.3 and 123.5 mAh/g, respectively. Going back to C/10, EDTA and CA electrodes can retain discharge capacities of 245.4 and 238.4 mAh/g, which represent 91.7 and 91% of the initial discharge capacity obtained in C/10 rate used at the begining. In general rate capabilities go in the same order EDTA > CA > CA/EDTA > EV as obtained in capacity …show more content…
Fig. 12 a and b shows the Nyquist plots of the fresh and after 5th cycles for Li1.2Ni0.13Co0.13Mn0.54O2 electrodes, respectively, where as the shapes of the Nyquist plots are similar. All the EIS curves exhibit one semicircle in the high frequency region which represents interfacial charge transfer resistance between the surface film and the active cathode mass (Rct). While, the sloping line at the low frequency region represents Warburg resistance, which related to the lithium ion diffusion in the bulk materials