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

Eight typical LiMnPO4 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/H3PO4 ratio, the predominately exposed planes of LiMnPO4 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 LiMnPO4 but results in significant changes in the morphology with distinctly increased particle size. The electrochemical properties of the corresponding LiMnPO4/C composites are remarkably dependent on their particle size. By applying the Mn-P-Li sequence and the LiOH/H3PO4 ratio of 2.7-3.0, the as-prepared LiMnPO4/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 LiMnPO4 crystals with small particle size and attractive electrochemical properties. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.