Papers by Author: Yun Jiang Cui

Abstract: The layered LiNi_0.5Mn_0.5O₂ used as a cathode material for lithium-ion batteries was synthesized from precursor Ni_0.5Mn_0.5CO₃ prepared via a carbonate co-precipitation method. The precursor Ni_0.5Mn_0.5CO₃ was synthesized by the addition of KHCO₃ to an aqueous solution of Ni, Mn sulphates. The powder LiNi_0.5Mn_0.5O₂ was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Spherical LiNi_0.5Mn_0.5O₂ with well development layered structure was obtained by the carbonate co-precipitation method. The LiNi_0.5Mn_0.5O₂ samples adopted the α-NaFeO₂ structure with a space group R-3m. Galvanostatic charge-discharge behavior of the LiNi_0.5Mn_0.5O₂ cathodes delivered a initial charge and discharge capacity of 144.4 mAh/g and 140.2 mAh/g, respectively in the voltage range 2.5-4.5V at a discharge rate of 0.02A/g. The capacity showed no dramatic capacity fading during 50 cycles.

Abstract: The energy storage density of (1-x) BaTiO3 – x Ba(Mg1/3Nb2/3)O3 (x = 0, 0.1, 0.2, 0.3) ceramics was investigated. The microstructure of samples was characterized by scanning electron microscopy (SEM). The energy storage density was calculated from the P-E hysteresis loops measured at room temperature. Experimental results show that the energy storage density of 0.9 BaTiO3 – 0.1 Ba(Mg1/3Nb2/3)O3 ceramics is highest among all compositions. At 15.8kV/mm electric field, the energy storage density of the sample can reach up to 1.07J/cm3, which is about 1.5 times higher than pure BaTiO3. The improvement of the energy density can be due to two factors: one is the improved breakdown strength caused by the optimized microstructure, the other is the decreased remnant polarization. This result indicates that bulk 0.9 BaTiO3 – 0.1 Ba(Mg1/3Nb2/3)O3 ceramic has advantages compared with pure BaTiO3 ceramic for energy storage applications, and with further improvements in microstructure and reduction of sintering temperature, could be a good candidate for energy storage capacitors.