However, only one broad peak is observed at approximately 3.9 V belonging to Ni4+/Ni2+ in the discharge process, which may be resulted from strong hysteresis during the reduction of Ni4+ to Ni 2+ via Ni3+. Figure 5 Electrochemical performances of the Li 2 NiTiO 4 /C EGFR assay nanocomposite. Charge-discharge curves at 0.05 C rate at room temperature (a) and 50°C (b), cycling performances
at 0.05 C rate (c) and rate capability at room temperature (d). The inset in (a) shows the dQ/dV plot for the first cycle. Figure 5b shows the charge-discharge curves of the Li2NiTiO4/C nanocomposite at 50°C. It delivers a high initial charge capacity of 203 mAh g-1 at 0.05 C rate, corresponding to 1.4 lithium extraction per formula unit. Also, the discharge capacity of 138 mAh g-1 is much higher than that tested at room temperature, demonstrating its enhanced electrode kinetics at high temperature. Figure 5c compares the cycling performances of the Li2NiTiO4/C nanocomposite at room temperature and 50°C. Li2NiTiO4/C exhibits a stable cycle life after several cycles, and its capacity retentions after 50 cycles are 86% at room
temperature and 83% at 50°C. At the GSK2126458 ic50 end of 80 cycles, Li2NiTiO4/C retains 82% of its initial capacity with typical coulombic efficiency of 95% at room temperature, www.selleckchem.com/products/ink128.html displaying a high electrochemical reversibility and structural stability during cycling. Figure 5d
presents the rate capability of the Li2NiTiO4/C nanocomposite from at room temperature. The charge rate remains constant at 0.1 C to insure identical initial conditions for each discharge. The Li2NiTiO4/C retains about 63% of its capacity from 0.05 to 1 C rate. The nanoparticles may reduce Li+ diffusion length and improve the ionic conductivity. Moreover, the highly conductive carbon coated on the surface of Li2NiTiO4 nanoparticles facilitates the rapid electrical conduction and electrode reactions, thus gives rise to capacity delivery and high rate performance. In order to investigate the phase change of Li2NiTiO4 during the charge-discharge process, the ex situ XRD of the Li2NiTiO4/C electrode is employed as shown in Figure 6. XRD peaks corresponding to the Li2NiTiO4 phase are observed from the pristine cathode sheet. The positions of diffraction peaks are hardly changed during cycling, which indicates that the extraction/insertion of lithium cannot change the framework of Li2NiTiO4. However, the I 220/I 200 ratio is 0.43 before charging, 0.50 after charging to 4.9 V, 0.48 after discharging to 2.4 V, and 0.47 after 2 cycles. The I 220/I 200 ratios at different charge-discharge states are very close after the first charge, indicating an incompletely reversible structural rearrangement upon initial lithium extraction. Trócoli et al.