Controllable synthesis of LiMnPO4 nanocrystals: Morphology evolution and their size-dependent electrochemical properties

Abstract Eight typical LiMnPO 4 nanocrystals with tunable morphologies have been controllably synthesized by varying the feeding sequence and the ratio of the reactants in an EG-assisted solvothermal approach. It is found that with the decrease of the OH − concentration induced by the primary LiOH/H 3 PO 4 ratio, the predominately exposed planes of LiMnPO 4 evolve from (010) for nanospindles to (100) for nanoplates in Li–P–Mn feeding sequence, and to both (010) and (100) for nanorods in Mn–P–Li feeding sequence. Further decrease of the OH − concentration hardly affects the formation of pure-phase LiMnPO 4 but results in significant changes in the morphology with distinctly increased particle size. The electrochemical properties of the corresponding LiMnPO 4 /C composites are remarkably dependent on their particle size. By applying the Mn–P–Li sequence and the LiOH/H 3 PO 4 ratio of 2.7–3.0, the as-prepared LiMnPO 4 /C nanorods exhibit superior rate capability (more than 105 mA h g −1 at 10 C) and remarkable cycling stability (a capacity retention of up to 93% after 100 cycles at 0.5 C) among all the samples, owing to their small length of less than 60 nm along the [010] direction. The results also confirm that excess LiOH amount is indeed required to yield LiMnPO 4 crystals with small particle size and attractive electrochemical properties.