A new solution combustion route to synthesize LiCoO_2 and LiMn_2O_4

摘要

Commercially important, high-voltage, lithium cathodes, such as LiCoO_2 and LiMn_2O_4 have been synthesized from nitrates, following the 'soft-chemistry' approach using starch as the combustion-assisting component. The minimum temperature required for phase formation and the degree of crystallinity has been evaluated from thermal studies and X-ray diffraction analysis, respectively. The starch-assisted combustion (SAC) method produces mono-dispersed powders of grain size below 1.5 μm as observed from scanning electron microscopy and particle-size analysis. The electrochemical activity of the synthesized oxide powders has been examined via cyclic voltammetric and charge-discharge studies using lithium coin cells. Cyclic voltammetric data shows excellent reversibility with respect to Li~+ and confirms the effect of crystallinity of the compounds on the electrochemical performance of the cathode materials. The electrochemical stability and performance of the cathodes over 30 cycles have been demonstrated with a capacity fade of <10% of the initial capacity. The simplicity and flexibility of this approach towards the synthesis of various other cathode materials is also discussed.