In order to study the influence of multiple ions doping into single-site on the structure and electrochemical properties of Ni-rich layered-structure cathode material LiNi0.5Co0.2Mn0.3O2, the coprecipitation of hydroxides was applied to synthesize Mg, Al co-doped cathode material LiNi0.5Co0.2Mn0.3–xMg1/2xAl1/2xO2 (x = 0.00, 0.01, 0.02, 0.04) in this paper. Morphology and structure, kinetic parameter, impedance and electrochemical performance of the material were respectively characterized by SEM, XRD, CV, EIS and galvanostatic charge/discharge test. The results of comprehensive analysis showed that the properties of material were improved obviously when the amount of doping was 0.02. At this amount of doping, the corresponding material has smaller cation mixing, higher hexagonal ordering of layered-structure, larger Li+ ion diffusion coefficients which are 2.444 × 10–10 and 4.186 × 10–10 cm2 s–1 for Li+ intercalation and deintercalation respectively, smaller impedance which is 33.93 Ω, higher specific capacity of first-discharge which is 168.01 mA h g–1 and higher capacity retention rate which is up to 95.06% after 20 cycles at 0.5 C (100 mA g–1).

LiNi0.5Co0.2Mn0.3O2 particles of uniform size were prepared through carbonate co-precipitation method with acacia gum. The precursor of carbonate mixture was calcined at 800 °C, and a well-crystallized Ni-rich layered oxide was got. The phase structure and morphology were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The micro-sized particles delivered high initial discharge capacity of 164.3 mA h g−1 at 0.5 C (1 C = 200 mA g−1) between 2.5 and 4.3 V with capacity retention of 87.5 % after 100 cycles. High reversible discharge capacities of 172.4 and 131.4 mA h g−1 were obtained at current density of 0.1 and 5 C, respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to further study the LiNi0.5Co0.2Mn0.3O2 particles. Anyway, the excellent electrochemical performances of LiNi0.5Co0.2Mn0.3O2 sample should be attributed to the use of acacia gum.

Li2FeSiO4 cathode materials have been prepared by sol-gel method. The effects of carbon sources on the structural, morphological and electrochemical behaviors of Li2FeSiO4 were investigated. The scanning electronic microscope (SEM) and X-ray diffraction powder analysis (XRD) indicate that the obtained samples using different carbon sources possess some difference in the morphology and in the particle size. The sample using the mixture of citric acid and oxalic acid as carbon source has a maximum discharge capacity of 118 mA h g−1 at 0.1 C between 1.8 and 4.5 V. The resulting cyclic voltammograms and electrochemical impedance spectra suggest that the sample using mixed acid as carbon source has smaller polarization and smaller charge transfer impedance.