Cathodic properties of a lithium-ion secondary battery using LiCoO2 prepared by a complex formation reaction

A LiCoO2 precursor is prepared by a complex formation reaction in a solution that contains LiOH, Co(NO3)(2), and humic acid it is used as a cathode for a lithium-ion rechargeable battery. Layered LiCoO2 powders are prepared in air at 700 or 850 degrees C after preheating the precursor at 350 and 450 degrees C, respectively. X-ray diffraction spectra of the powders display a high intensity (003) peak and two low intensity (104) and (101) peaks. This indicates that the powders are well crystallized. Cyclic voltammetry, a galvanostatic charge/discharge experiment, and impedance spectroscopy are used to characterize the LiCoO2 electrode in a 1 M LiClO4/propylene carbonate electrolyte solution during the intercalation/de-intercalation of lithium ions through the electrode. The voltammogram recorded at a scan rate of 0.01 mV s(-1) shows a set of redox waves that are caused by the de-intercalation/intercalation of lithium ions through the electrode. A cell, composed of a LiCoO2 cathode and a Li anode, shows an initial discharge specific capacity of 112.5 mA h g(-1) at a current density of 1 mA cm(-2) (43.25 mA g(-1)) between 3.6 and 4.2 V vs. Li/Li+ electrode. 100 charge/discharge cycles were achieved for a cell composed of a LiCoO2 cathode and graphite (MCMB 6-28) anode separated by Cellgard 2300. X-ray diffraction, charge/discharge, and cyclic voltammetric data shows that there is only a single phase reaction below 4.3 V during charge/discharge for a electrode prepared at 700 degrees C. The diffusivity of lithium ions, D-Li(+), as determined by AC. impedance, is 5.2 X 10(-12) m(2) s(-1). (C) 1998 Elsevier Science S.A.