| For resolve the Jahn-Teller effect, improve the capacities and cycle performance and decrease the cell price, a series of spinel lithium manganese oxides doped by lithium, nickel and titanium were prepared by liquid method. Energy spectrometer and atomic absorption spectrum (AAS) were used to determine their compositions, and Scanning electron microscope (SEM) , Transmission electron microscopic (TEM) were used to analysis the appearance of the samples. X-ray powder diffractometer (XRD), Forier transform infrared spectroscopy (FT-IR) and crystalline parameters were used to determine the structure of the samples, X-ray photoelectron spectra (XPS) were employed to determine the oxide state of elements in the samples. In the meantime, electrochemical properties of the materials in the organic electrolyte and aqueous electrolyte were researched.SEM and TEM analysis show that the sample co-doped by nickel and titanium has nano-pellets with morpha like snow and great surface, Which theinitial discharge capacities in organic electrolyte reached 155.8mAh/g and whichwere more than theoretic one Farad electron discharge capacities (148mAh/g). Duringthe charging and discharging cycle, the change rate of the crystal volume was only 0.233% and the sample showed long cycle life. When there are more nickel atom doped in spinel (the mole ratio of Mn and Ni was 1.4:0.6), the discharging platform jumped to 4.5V from original 3.8V. The materials showed to suit for positive materials in 5V lithium ion batteries.After finished the cyclic voltammetry experiments, the results showed that iron steel grid can act as good current collector in the aqueous electrolyte. While the scan rate was fall in the range of 0.5-4.0mV/s, electrochemical reaction of the lithium insertion/extraction in the solid phase was kinetically limited by the diffusion of lithium ions . After 40 cycles in aqueous electrolyte the discharge capacities of sample of S13 reached 77mAh/g, and showed good cycle performance. |
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