Effect of aluminium doping on cathodic behaviour of LiNi0.7Co0.3O2

Solid solutions of the formula LiNi0.7Co0.3-zAlzO2 (0.0 less than or equal to z less than or equal to 0.20) have been synthesized and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and surface a rea and density measurements. Single-phase materials are obtained for z les s than or equal to 0.15. Their cathodic behaviour in coin cells with Li met al as anode and a liquid electrolyte is examined by charge-discharge cyclin g at the 0.13C rate between 2.7 and 4.3 V and by cyclic voltammetry. irreve rsible capacity loss occurs for all the compositions, but the phases with z = 0.05 and z = 0.10 show much less capacity fading at the end of 50 cycles as compared to those with z = 0.0 and z > 0.10. The 5 at.% Al-doped compou nd showed a discharge capacity of 137 mA h(-1) g after 100 cycles that corr esponds to 70% capacity retention. The beneficial effect of Al-doping (z le ss than or equal to 0.10) is corroborated by cyclic voltammograms and diffe rential scanning calorimetry (DSC) data on charged cathodes. (C) 2001 Elsev ier Science B.V. All rights reserved.