Hierarchical LiMnPO4 assembled from nanosheets via a solvothermal method as a high performance cathode material

A series of LiMnPO4 nanoparticles with different morphologies have been successfully synthesized via a solvothermal method. The samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results show that the morphology, particle size and crystal orientation are controllably synthesized by various precursor composite tailoring with various Li : Mn : P molar ratios. At 3 : 1 : 1, a Li+-containing precursor Li3PO4 is obtained while at 2 : 1 : 1, only a Mn2+-containing precursor involving Mn-5(PO4)(2)[(PO3)OH](2)center dot 4H(2)O and MnHPO4 center dot 2.25H(2)O is detected. Especially, at 2.5 : 1 : 1, the precursor consists predominantly of a Mn2+-containing precursor with a minor amount of Li3PO4. From 2 : 1 : 1 to 3 : 1 : 1, the particle morphology evolves from sheet to spherical texture accompanied with the particle size reducing. In the presence of urea, highly uniform LiMnPO4 with a hierarchical micro-nanostructure is obtained, which is composed of nanosheets with a thickness of several tens of nanometers. Thus, these unique hierarchical nanoparticles with an open porous structure play an important role in the LiMnPO4 cathode material. At a concentration of 0.16 mol L-1 for urea, the hierarchical LiMnPO4/C sample assembled from nanosheets with the (010) facet exposed shows the best electrochemical performance, delivering higher reversible capacity of 150.4, 142.1, 138.5, 125.5, 118.6 mA h g(-1) at 0.1, 0.2, 0.5, 1.0, 2.0C, respectively. Moreover, the composites show long cycle stability at high rate, displaying a capacity retention up to 92.4% with no apparent voltage fading after 600 cycles at 2.0C.