ИСТИНА

At the moment, olivine-structured complex phosphates of lithium and transitional metals are considered as one of the most promising cathode materials for the Li-ion batteries; LiFePO4 is actually most studied. Besides its advantages, such as high theoretical capacity, low cost and excellent cyclability, LiFePO4 has serious drawbacks. One of them – low working potential in comparison with other materials (3.4V vs. Li/Li+). In other side, materials with higher potential such as LiCoPO4, LiMnPO4, LiNiPO4 cannot be used in li-ion batteries at the moment, because of low achievable capacity and poor cycle life. Combining these compositions into the solid solutions with general formula Li(M1,M2,M3)PO4, М1,2,3 = Fe, Mn, Co, gives opportunity to combine increased working potential, structure stability and good cyclability. Besides this, it is established that random distribution of the d-cations in the olivine structure leads to the increasing of the solid solution (or single-phase) mechanism, and therefore considerable improves performance at high cycling rates[1]. Also, for the perfect electrochemical performance and cycle life it is important to obtain defectless material with definite morphology and size of particles, which may be achieved by the application of the hydro- and solvothermal routes. Synthesis of LiFe1-x-yMnxCoyPO4 (x=0.5, y=0 and x=y=0.33) cathode materials by hydro- and solvothermal routes and study of the electrochemical properties of the obtained materials was the aims of the present work. Optimization of the synthetic route was carried out mainly for LiFe0.5Mn0.5PO4. Different salt concentrations and solvents were used; main tendencies of particles growth were established for the “water-alcohol” systems (ethylene glycol, ethanol, polyethylene glycol). The phase-formation process for the named compounds was studied by in-situ method – Calvet calorimetry. The dependence of the phase-growth process on the starting synthetic conditions is shown, and autocatalytic mechanism of the reaction is demonstrated by calculation from the empirical data. This work was supported by the Russian Foundation of Basic Research (grants No. 14-29-04064), Skolkovo Institute of Science and Technology, and the Lomonosov Moscow State University Program of Development. References 1. Drozhzhin, O. A., et al. Electrochimica Acta, 2016, 191: 149-157.