Increasing the efficiency of carbon coating on olivine-structured cathodes by choosing a carbon precursor

•LiFe0.5Mn0.5PO4/C is obtained by mechanochemically assisted solid-state synthesis.•Carbon black, citric acid and polyvinylpyrrolidon are used as carbon precursors.•Carbon coating formation is studied using FTIR spectroscopy of adsorbed probe molecules.•The properties of carbon coating are studied by Raman spectroscopy, MSCP and EIS. Carbon-coated LiFe0.5Mn0.5PO4 (C-LFMP) cathode materials were obtained by two-step mechanochemically assisted solid-state synthesis. After mechanical activation and heat treatment of the reagent mixture at 400 °C, the pre-prepared carbon-free LFMP-400 was obtained, which was then ball milled with three different carbon precursors: carbon black (CB), citric acid (CA) and polyvinylpyrrolidon (PVP) and subsequently annealed at 700 °C. FTIR spectroscopy of adsorbed probe molecules (pyridine) was used to detect the presence of Brønsted acid centers on the surface of LFMP-400. The mechanism of their interaction with functional groups of carbon precursors during joint ball milling and heating up to 700 °C was investigated using FTIR spectroscopy. The properties of carbon coatings were studied by Raman spectroscopy, standard contact porosimetry, and electrochemical impedance spectroscopy, and their effect on electrochemistry of the C-LFMP composites was studied by galvanostatic cycling. It is shown that the LFMP/PVP composite is characterized by higher capacity and better high-rate capability due to the formation of well-graphitized carbon coating tightly bound to the surface of LFMP and having an optimal porous structure.