EFFECTS OF LITHIUM CONTENT ON THE ELECTROCHEMICAL LITHIUM INTERCALATION REACTION INTO LINIO2 AND LICOO2 ELECTRODES

The electrochemical lithium intercalation reaction into LiNiO2 and LiC oO2 electrodes in 1 M LiClO4-propylene carbonate solution is investiga ted as a function of lithium content in the oxide electrodes by using X-ray diffractometry (XRD), electrochemical impedance spectroscopy (EI S), and a galvanostatic intermittent titration technique (GITT). Li1-d eltaNiO2 shows a greater loss in capacity during the first intermitten t discharge, as well as a higher resistance for the electrochemical in tercalation reaction, in comparison with L(1-delta)CoO(2). This is att ributed to a partial cation mixing in Li1-deltaNiO2 which is substanti ated by XRD studies. The electrochemical impedance spectra of the Li1- deltaNiO2 electrode reveals that the magnitude of the intermediate fre quency are that is associated with the absorption reaction decreases w ith increasing lithium content, (1-delta), in the range from 0.5 to 0. 7. By contrast, Li1-deltaCoO2 exhibits the reverse behaviour. The comp onent diffusivities of lithium ions display a nearly constant value, i n the order of 10(-11) cm(2) s(-1), forboth electrodes at room tempera ture, irrespective of the value of (1 - delta) over the range 0.5-0.7. It is suggested that lithium-ion diffusion through both the layered o xides is affected by the number of empty sites within the lithium-ion layer, and not by the lattice parameter.