Hydrogen reduction of vanadium in vanadium-doped LiMnPO₄

The samples of vanadium-doped LiMnPO₄ have been synthesized by the solid-state reaction technique. To reduce the oxidation state of vanadium from V⁵⁺ to V⁴⁺, the samples have been additionally annealed under hydrogen atmosphere. The tetravalent state of vanadium was proved by analysis of V 2p X-ray photoelectron spectra. Raman spectroscopy, first-principle studies and magnetic measurements were used to determine the effect of V⁴⁺ on the Li–Mn phosphate properties. - Highlights: • The samples of LiMnPO₄ doped with vanadium were prepared. • The samples were annealed under hydrogen atmosphere. • The V⁴⁺ presence was proved. • The ab initio calculations revealed the most favorable position for oxygen vacancy. • The presence of V⁴⁺ changes magnetic properties and Raman spectra of LiMnPO₄