Nail Suleimanov

Li₃V₂(PO₄)₃/Li₃PO₄ (LVPO/LPO) composites as cathodes for Li-ion batteries were synthesized by the hydrothermal method and subsequently annealed in an Ar atmosphere. The effect of Li₃PO₄ content on the crystal structure, morphology and the related magnetic and electrochemical properties of Li₃V₂(PO₄)₃/Li₃PO₄ composites, containing 7.5 wt% and 14 wt% of Li₃PO₄ (LVPO/LPO-7.5 and LVPO/LPO-14) was investigated. The microstructure and morphology of the obtained composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM); magnetic and electrochemical properties investigations were performed using the electron spin resonance and galvanostatic methods, respectively. It was shown that Li₃V₂(PO₄)₃/Li₃PO₄ composites exhibit a high discharge capacity, good cycle performance (105 and 120 mAh g⁻¹ for the 200th cycle at 1C for LVPO/LPO-7.5 and LVPO/LPO-14, respectively), and insignificant changes in the surface morphology after 200 lithiation/delithiation cycles. Our results demonstrate that the increase in Li₃PO₄ content led to a decrease in the Li stoichiometry and magnetic inhomogeneity in Li₃V₂(PO₄)₃ phase; thus, the improvement in the electrochemical performance of LVPO/LPO composites due to incorporation of Li₃PO₄ can be attributed to their chemical and magnetic inhomogeneity.

Magnetic properties of the submicron carbon-coated LiFe_1−xMn_xPO₄ (x = 0, 0.01, 0.1) systems were investigated using the electron spin resonance (ESR) method. The observed ESR signal consisted of two broad resonance lines with a Lorentzian line shape for all samples. The temperature dependence character of the integral intensity of these lines changed significantly with increasing manganese concentration, indicating a change in the nature of the magnetic interactions between the manganese and iron ions. We suggest that the noticeable capacity loss observed in the LiFe_1−xMn_xPO₄ systems with increasing Mn content can be explained by the random distribution of Mn ions and changes to the type of magnetic ordering in these systems, despite the attractiveness of the electrochemical Mn²⁺/Mn³⁺ pair compared with Fe⁺²/Fe⁺³.

Here, we present the investigation of the magnetic properties of Li₃V₂(PO₄)₃/Li₃PO₄ composites, which can be potentially used as a cathode material in lithium-ion batteries. Li₃V₂(PO₄)₃/Li₃PO₄ was synthesized by the thermal hydrolysis method and has a granular mesoporous structure. Magnetic properties of the composite were investigated using magnetometry and electron spin resonance methods. Based on magnetization measurements, the simultaneous existence of the paramagnetic phase with antiferromagnetic interactions between spins of V³⁺ ions and magnetically correlated regions was suggested. Most probably, magnetically correlated regions were formed due to anti-site defects and the presence of V⁴⁺ ions that was directly confirmed by electron spin resonance measurements.