Stability of Li2MSiO4 (M = Mn, Co) in the carbon coating process

The stability of Li2MnSiO4 (LMS) and Li2CoSiO4 (LCS) in the conducting carbon layer (CCL)/Li2MSiO4 (M = Mn, Co) composites forming process was characterized in this paper. Studied nanocomposites were obtained via modified sol-gel Pechinis synthesis followed by the direct deposition of carbon coating on the active material grains. As a carbon precursor the poly-N-vinylforamide (PNVF) modified by pyromellitic acid (PMA) in water solution was used. The investigated materials were examined in terms of physicochemical properties by using the powder X-ray diffraction (XRD), and electrical conductivity studies (EC). The electrochemical properties of Li/Li+/CCL/Li2MnSiO4 cells were determined by the galvanostatic charge discharge tests (CELL TESTS). The stability of LMS and LCS under oxidizing and reductive conditions were analyzed by the temperature programmed oxidation (TPO/TG) and temperature-programmed reduction with H2 (H2-TPR). Results showed that CCL formation can be executed with reconstruction of LMS crystalline structure while it is impossible on LCS grains using standard pyrolysis. Given galvanostatic charging/discharging tests demonstrate that forming carbon coatings, with ca. 10 wt% carbon on polysilicate substrates can provide satisfactory electrical properties as well as enhanced surface stability.