High-temperature combustion synthesis and electrochemical characterization of LiNiO2, LiCoO2 and LiMn2O4 for lithium-ion secondary batteries

Lithium nickelate (Li_0.88Ni_1.12O₂), lithium cobaltate (LiCoO₂) and lithium manganate (LiMn₂O₄) were synthesized by fast self-propagating high-temperature combustion and their phase purity and composition were characterized by X-ray diffraction and inductively coupled plasma spectroscopy. The electrochemical behaviour of these oxides was investigated with regard to potential use as cathode materials in lithium-ion secondary batteries. The cyclic voltammograms of these cathode materials recorded in 1 M LiClO₄ in propylene carbonate at scan rates of 0.1 and 0.01 mV s^–1 showed a single set of redox peaks. Charge-discharge capacities of these materials were calculated from the cyclic voltammograms at different scan rates. The highest discharge capacity was observed in the case of Li_0.88Ni_1.12O₂. In all the cases, at a very slow scan rate (0.01 mV s^–1) the capacity of the charging (oxidation) process was higher than the discharging (reduction) process. A strong influence of current density on the charge-discharge capacity was observed during galvanostatic cycling of Li_0.88Ni_1.12O₂ and LiMn₂O₄ cathode materials. LiMn₂O₄ can be used as cathode material even at higher current densities (1.0 mA cm^–2), whereas in the case of Li_0.88Ni_1.12O₂ a useful capacity was found only at lower current density (0.2 mA cm^–2). For the fast estimation of the cycling behaviour of LiMn₂O₄, a screening method was used employing a simple technique for immobilizing microparticles on an electrode surface. Electronic Publication