Solvothermal synthesis of hierarchical LiFePO4 microflowers as cathode materials for lithium ion batteries

Hierarchical LiFePO4 microflowers have been successfully synthesized via a solvothermal reaction in ethanol solvent with the self-prepared ammonium iron phosphate rectangular nanoplates as a precursor, which is obtained by a simple water evaporation method beforehand. The hierarchical LiFePO4 microflowers are self-assemblies of a number of stacked rectangular nanoplates with length of 6-8 mu m, width of 1-2 mu m and thickness of around 50 nm. When ethanol is replaced with the water-ethanol mixed solvent in the solvothermal reaction, LiFePO4 micro-octahedrons instead of hierarchical microflowers can be prepared. Then both of them are respectively modified with carbon coating through a post-heat treatment and their morphologies are retained. As a cathode material for rechargeable lithium ion batteries, the carbon-coated hierarchical LiFePO4 microflowers deliver high initial discharge capacity (162 mAh g(-1) at 0.1 C), excellent high-rate discharge capability (101 mAh g(-1) at 10 C), and cycling stability, which exhibits better electrochemical performances than carbon-coated LiFePO4 micro-octahedrons. These enhanced electrochemical properties can be attributed to the hierarchical micro/nanostructures, which can take advantage of structure stability of micromaterials for long-term cycling. Furthermore the rectangular nanoplates as the building blocks can improve the electrochemical reaction kinetics and finally promote the rate performance. (C) 2011 Elsevier B.V. All rights reserved.