Yttrium-doped Li(Ni, Co)O₂: an improved cathode for Li-ion batteries

Abstract

Yttrium-doped mixed oxides, Li(Ni_0.7-yY_yCo_0.3)O₂, y=0.00-0.05 have been synthesized and characterized. Their cathodic behavior has been examined in cells with lithium metal as anode. The limit for Y solubility is ≤0.05. The beneficial effect of Y is evident by way of increased capacity - retention during charge-discharge cycling, up to 100 cycles at 0.2C rate and up to 50 cycles at 1C rate. Cyclic voltammograms indicate that the phase transitions which usually occur in LiNiO₂ during cycling, are suppressed by Co- and Y-doping but not completely eliminated. A reduced hysteresis in the anodic and cathodic peak voltages observed for y=0.05 is an indication of excellent reversibility of the electrode. Thermal stability of the charged cathode is not, however, improved by Y-doping.