Nanostructured mixed phospho-olivine LiMnyFe1-yPO4/C composites having different ratio of manganese and iron (0 < y < 1) are prepared by an easy, quick and cost effective hydrothermal synthesis in the presence of a cationic surfactant and their electrochemical behaviour as cathodes for Li-ion battery is demonstrated. A detailed study of the influence of Fe substitution with Mn on the structure, morphology and electrochemical performances of the resulting samples is performed by means of X-ray powder diffraction and Rietveld refinement of the diffraction patterns, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, N-2 physisorption at 77 K, scanning and transmission electron microscopy, cyclic voltammetry and constant current charge-discharge cycling. The best performing LiMnyFe1-yPO4/C composite sample is able to deliver a very stable cycling behaviour for several hundred cycles with good specific capacity values, high Coulombic efficiency and rate capability and is also demonstrated to work in a real Li-ion battery configuration versus a graphite anode. These improved electrochemical properties are ascribed to the kind of synthesis adopted that leads to nanostructured particles, homogeneously coated by a thin layer of carbon, which exerts its positive effect by improving electronic conductivity and suppressing Mn dissolution from the olivine structure during prolonged cycling. (c) 2013 Elsevier Ltd. All rights reserved.