Template-Assisted Hydrothermal Synthesis of Li₂MnSiO₄ as a Cathode Material for Lithium Ion Batteries

Lithium manganese silicate (Li₂MnSiO₄) is an attractive cathode material with a potential capacity above 300 mA h g^-1 if both lithium ions can be extracted reversibly. Two drawbacks of low electronic conductivity and structural collapse could be overcome by a conductive surface coating and a porous structure. Porous morphology with inner mesopores offers larger surface area and shorter ions diffusion pathways and also buffers the volume changes during lithium insertion and extraction. In this paper, mesoporous Li₂MnSiO₄ (M-Li₂MnSiO₄) prepared using MCM-41 as template through a hydrothermal route is compared to a sample of bulk Li₂MnSiO₄ (B-Li₂MnSiO₄) using silica as template under the same conditions. Also, in situ carbon coating technique was used to improve the electronic conductivity of M-Li₂MnSiO₄. The physical properties of these cathode materials were further characterized by SEM, XRD, FTIR, and N₂ adsorption-desorption. It is shown that M-Li₂MnSiO₄ exhibits porous structure with pore sizes distributed in the range 9-12 nm, and when used as cathode electrode material, M-Li₂MnSiO₄ exhibits enhanced specific discharge capacity of 193 mA h g^-1 at a constant current of 20 mA g^-1 compared with 120.1 mA h g^-1 of B-Li₂MnSiO₄. This is attributed to the porous structure which allows the electrolyte to penetrate into the particles easily. And carbon-coated M-Li₂MnSiO₄ shows smaller charge transfer resistance and higher capacity of 217 mA h g^-1 because carbon coating retains the porous structure and enhances the electrical conductivity. (Figure Presented).