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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
Research Student Awards

PhD Thesis: Synthesis of nanostructure materials for lithium ion batteries

Author: WU, Zhaoyun

Year: 2008

Supervisor(s): Mike Reece, Xiao Guo

This project focuses on the development of a chemical synthesis technique for the manufacture of nanostructural cathode materials for lithium-ion batteries. This technique combines co-precipitation, freeze-drying and calcination (CpFC), and was used to synthesize two types of compounds, LiCoO2 and LiMn2O4, in comparison with other preparation methods, solid-state reaction and self-mixing. The effects of Mo as a dopant in LiCoO2 and Ni in LiMn2O4 were investigated to improve the properties of the native oxides. Furthermore, a new cathode candidate, LiCoPO4, was synthesized for the first time by this approach.

The obtained powder particles were characterised by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis/differential scanning calorimetry (TG/DSC), scanning electron microscopy (SEM) and X-Ray diffraction (XRD).

It is suggested that CpFC may have potential uses in industry where clean burnout and low energy wastage are required. This developed synthesis route is capable of producing high quality materials with much reduced time and low-cost starting materials. Current experimental results indicate that the obtained compounds are generally of high purity, regular morphology, nano-scale particle size and ideal homogeneity. These properties of the sample particles are found to vary with the drying method, pH value of the precipitation media and calcinations atmosphere. Small variations in the lattice parameters between doped and native compounds can be ascribed to the difference between the ionic radii of dopant and host ions. The doping at low concentration levels (0.05 mol% Mo in LiCoC2 and 0.5 mol% Ni in LiMn2O4) shows negligible distortion of the original host structures.