Solvothermal-assisted morphology evolution of nanostructured LiMnPO_4 as high-performance lithium-ion batteries cathode

摘要

As a potential substitute for LiFePO_4, LiMnPO_4 has attracted more and more attention due to its higher energy, showing potential application in electric vehicle(EV) or hybrid electric vehicle(HEV). In this work,solvothermal method was used to prepare nano-sized LiMnPO_4, where ethylene glycol was used as solvent, and lithium acetate(LiAc), phosphoric acid(H_3 PO_4) and manganese chloride(MnCl_2) were used as precursors. The crystal structure and morphology of the obtained products were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The electrochemical performance was evaluated by charge-discharge cycling, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the molar ratio of LiAc:H_3 PO_4:MnCl_2 plays a critical role in directing the morphology of LiMnPO_4. Large plates transform into irregular nanoparticles when the molar ratio changes from 2:1:1 to 6:1:1. After carbon coating, the product prepared from the 6:1:1 precursor could deliver discharge capacities of 156.9,122.8, and 89.7 mAhg-1 at 0.05 C, 1 C and 10 C, respectively.The capacity retention can be maintained at 85.1% after 200 cycles at 1 C rate for this product.