LiMn1−x Fe x PO4 nanomaterials at low Fe concentration (x = 0, 0.1, 0.2) for lithium-ion batteries have been synthesized with high yield via a facile solvothermal route in a mixed solvent of water and polyethylene glycol (PEG200). SEM and TEM images reveal that all samples are single crystalline with similar rod-like shapes, and XRD characterizations indicate that the crystal lattices decrease with the increasing concentration of Fe. Electrochemical tests show that the best electrochemical properties can be achieved by substituting 20% of Fe at Mn-site. The as-prepared LiMn0.8Fe0.2PO4 sample delivers a high initial discharge capacity of 165.3 mAh g−1 at 0.05C, which is close to the theoretical capacity of LiMnPO4. Moreover, it also demonstrates excellent cycle performance and remarkable rate capability.