Layered LT-LiNi1−yCoyO2 (0.3≤y≤0.7) cathodes for rechargeable lithium cells synthesized by co-precipitation method

Lithium nickel-cobalt oxides were synthesized at low temperature using a precipitation method involving dissolution of metal acetates and Li(COOCH₃) in oxalic acid (dicarboxylic acid). Pyrolysis of the precipitate at 400–600 °C produced single phase LiNi_1−yCo_yO₂ (0.3≤y≤0.7) with submicron-sized particles. Oxalic acid acted as a fuel, decomposed the homogeneous precipitate of metal complexes at low temperature, and yielded the free impurity LiNi_1−yCo_yO₂ compounds. The physicochemical properties of synthesized products were investigated by structural (XRD, SEM), spectroscopic (FTIR and Raman) and thermal (DTA/TG) analyses. The electrochemical properties of the LiNi_1−yCo_yO₂ cathode materials were evaluated in rechargeable Li cells by employing a non-aqueous organic electrolyte mixture of 1M LiPF₆ in EC+DMC. The cells maintained excellent cyclability at moderate charge-discharge rates. Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998.