Changbao Zhu, Jelena Popovic
Recently, LiFePO4 has received much attention as a potential of high rate cathode material for electric vehicle and hybrid electric vehicle application. However, size effects in LiFePO4 need to be clarified in order to arrive at deeper conceptual understanding of its electrochemical behaviour.
In this project, metastable LiFePO4 (nanocrystalline and amorphous phase) is investigated using thermodynamic considerations combined with obtained experimental results. The effect of size as well as the impact of amorphization are strongly dependent on the storage mechanism (single phase vs. two phase model), size distribution and surface energy.
The thermodynamic effects in the LiFePO4 are very complex and even staging phenomena are observed, which challenges the traditional two phase models. Various staging phenomena were observed for LiFePO4 of different sizes. The corresponding thermodynamics and kinetics for phase transition process are discussed.