Enhanced electrochemical properties of fluoride-coated LiCoO2 thin films
The electrochemical properties of fluoride-coated lithium cobalt oxide [LiCoO2] thin films were characterized. Aluminum fluoride [AlF3] and lanthanum fluoride [LaF3] coating layers were fabricated on a pristine LiCoO2 thin film by using a spin-coating process. The AlF3- and LaF3-coated films exhibited a higher rate capability, cyclic performance, and stability at high temperature than the pristine film. This indicates that the AlF3 and LaF3 layers effectively protected the surface of the pristine LiCoO2 film from the reactive electrolyte.
The Effect of Surface Modification with La-M-O (M = Ni, Li) on Electrochemical Performances of Li[Ni0.8Co0.15Al0.05]O2 Cathode
The surface of Li[Ni 0.8 Co 0.15 Al 0.05 ]O 2 cathode particle was modified by lanthanum based oxide to improve electrochemical property and thermal stability. The XRD pattern of surface layer was indexed with that of La 4 NiLiO 8 . The discharge capacity of modified electrode was higher than that of pristine sample, specially at fast charge-discharge rate and high cut-off voltage. In the DSC profile of the charged sample, the generation of heat by exothermic reaction was decreased by surface modification. Such enhancement may by attributed to the presence of stable lanthanum based oxide, which effectively suppressd the reaction between electrode and electrolyte on the surface of Li[Ni 0.8 Co 0.15 Al 0.05 ]O 2 electrode.
Influence of aluminum doping on the properties of LiCoO2 and LiNi0.5Co0.5O2 oxides
Abstract We have prepared LiCo 1− y Al y O 2 and LiNi 0.5− y Al y Co 0.5 O 2 (0≤ y ≤0.3) powder samples by a low temperature sol–gel method using succinic acid as chelating agent. We have studied the details of their crystallographic and local structure by X-ray diffraction (XRD) and FTIR spectroscopy, respectively; we have analyzed their chemical composition by ICP and obtained information about the morphology of the polycrystalline particles by SEM. Also, we have studied the electrochemical performance of the as-prepared materials in the LiLiNi 0.5− y Al y Co 0.5 O 2 cells cycled in the potential range 2.5–4.2 V finding that the overall capacity of the oxides has been reduced due to the metal substitution. For example, at 4.2 V cut-off, the charge capacity of the LiLiNi 0.35 Al 0.15 Co 0.5 O 2 cell is ca. 115 mA h/g. However, more stable charge–discharge cycling performances have been obtained as compared to those displayed by the native oxides. Finally, we have characterized the kinetics of Li-diffusion by the galvanostatic intermittent titration technique and, according to our results, Al substitution provides an increase in the chemical diffusion coefficients of Li ions in the LiNi 0.5− y Al y Co 0.5 O 2 matrix.