Cathodic behavior of (Co, Ti, Mg)-doped LiNiO₂

Abstract

Single-phase lithium nickel oxides with the formula LiNi_0.8Co_0.2-2yTi_yMg_yO₂, y=0.0-0.075 have been prepared and characterized. Their electrochemical properties as cathode during charging and discharging are discussed. Thermal behavior of the charged cathodes was studied by differential scanning calorimetry (DSC). Results show that the cathodic behavior of compounds with y=0.0 and 0.03 and those with y=0.05 and 0.075 are similar with respect to the initial irreversible capacity, suppression of phase transitions, cycling behavior and capacity fading. The composition with y=0.05 shows a cathodic capacity of 120 mA h/g at the 0.5 C rate and 2.5-4.4 V voltage window with only 7% fading over 40 cycles. The thermal behavior of the charged cathode with y=0.05 is improved compared to y=0.0 and 0.03. A qualitative explanation for the observed cathodic behavior with various y values is offered in terms of the occupancy of the magnesium-ions in the Li and Ni layers in the lattice.