C/Li2MnSiO4 nanocomposite material was obtained by sol–gel method followed by carbon coating process. Electrochemical properties of nanosized C/Li2MnSiO4 cathode composite were studied in terms of changes in the long range ordering of the crystalline structure. Structural morphology was determined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Ex-situ XRD studies confirmed amorphization of material during electrochemical process. Even though, C/Li2MnSiO4 composite revealed high discharge capacity (up to 185 mAh g−1) within 1.5–4.8 V, what corresponds to the exchange of more than one lithium-ion per formula unit (1.11 mole Li+). Electrochemical impedance spectroscopy (EIS) studies showed substantial changes in electrical properties of Li2MnSiO4 during amorphization process. The obtained results suggest that electrochemically formed amorphous Li2MnSiO4 has much higher electrical conductivity and Li+ ions diffusibility than as-obtained in sol–gel process crystalline one.