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 μm, width of 1–2 μm 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.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Hierarchical LiFePO4 microflowers assembled by thin rectangular nanoplates have been synthesized. ► Hierarchical LiFePO4 microflowers deliver excellent electrochemical performance. ► Hierarchical micro/nanostructures take the advantages of both nanometer-sized building blocks and micro-sized assemblies, which facilitate fast electrochemical reaction kinetics and good structural stability.