Microwave-Solvothermal Synthesis of Nanostructured Li2MSiO4/C (M = Mn and Fe) Cathodes for Lithium-Ion Batteries

Nanostructured Li2FeSiO4 and Li2MnSiO4 cathodes have been synthesized by a facile microwave-solvothermal synthesis. To improve crystallinity and enhance electronic conductivity, the resulting samples have been mixed with sucrose and heated at 650 degrees C for 6 h in argon atmosphere. The Li2MSiO4/C nanocomposites, thus, obtained have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, electrochemical measurements, and differential scanning calorimetry. The Li2FeSiO4/C sample exhibits good rate capability and stable cycle life, with discharge capacities of 148 mAh/g at room temperature and 204 mAh/g at 55 degrees C. Although Li2MnSiO4/C shows higher discharge capacities of 210 mAh/g at room temperature and 250 mAh/g at 55 degrees C, it suffers from poor rate capability and drastic capacity fade. The disparity in the electrochemical performance and redox behavior between Li2FeSiO4/C and Li2MnSiO4/C can be attributed to the differences in the structural stability of the delithiated phases, Jahn-Teller distortion of Mn3+ ions, Mn dissolution, and electronic conductivity.