Using DFT calculations and experimental methods we have studied the thermodynamic stability of Li2MnSiO4 polymorphs. Three possible Li2MnSiO4 forms have been considered crystallizing in Pmnb, Pmn21 and P21/n space groups. The Pmnb polymorph is predicted to be 2.4 meV/f.u. and 65 meV/f.u. more stable than the Pmn21 and P21/n forms. Calculations were confirmed experimentally by XRD, SAED and 6Li MAS-NMR. The crystal structure has a minor impact in the average lithium intercalation voltage for the two electron process (calculated voltages are 4.18, 4.19, and 4.08 V for Pmnb, Pmn21 and P21/n).
COBISS.SI-ID: 3987482
Paper describes three different synthesis techniques (hydrothermal synthesis, modified Pechini synthesis and Pechini synthesis) for preparation of Li2FeSiO4 samples. With the proper structuring of Li2FeSiO4/C composites, utilisation of large part of capacity is also possible at current densities corresponding to C/5 and C/2 cycling rate. The results obtained by Mössbauer spectroscopy and XRD analysis indicate on the differences in the crystal structure between the thermally treated samples and the sample prepared by hydrothermal synthesis.
COBISS.SI-ID: 3766810