A solid solutions series of LiMn1-xNixPO4 nanomaterials with 0 <= x <= 0.45 was produced by a low-temperature microwave-assisted hydrothermal process. The materials have been systematically studied regarding structure, morphology, magnetism, and electrochemical properties. The lattice parameters in the orthorhombic olivine structure obey Vegard's law and linearly depend on x. Similarly, the static magnetisation reflects the decrease of the transition metal paramagnetic moment upon substitution of Mn2+ by Ni2+. At low temperatures, antiferromagnetic long range order appears for all Ni-concentrations. The potential of the Mn2+/3+ redox couple is found to linearly increase with x. This is explained by a larger electronegativity of Ni2+ as compared to Mn2+ and associated changes in the covalency of the Mn-O bond. (C) 2014 Elsevier Ltd. All rights reserved.