Anion species are proved to have a significant influence on orientation, agglomeration and defect control of crystal growth for LiMn0.9Fe0.1PO4 nano-particles prepared by solvothermal synthesis. SO4 2− is helpful for high dispersity, while Cl− benefits accurate molar ratio control of transition metals in LiMn0.9Fe0.1PO4. Various LiMn0.9Fe0.1PO4 particles, being agglomerative spindles or mono-dispersed uniform nano-flakes, can be obtained by just tuning [Cl−]:[SO4 2−] ratio, and present dramatically different electrochemical performances. Though the as-prepared samples possess similar reversible capacities around 130 mAh g−1 at low C-rate, they show very different rate performances depending on morphology of the particles.