Novel CV for Phase Transformation Electrodes

Abstract

Phase transformation cyclic voltammetry (CV) was developed by integrating mixed-control phase transformation theory and charge transfer effect with traditional CV model. This mixed-control phase transformation CV model was validated by good agreement between experimental CV data and simulated values from phase transformation CV for LiFePO4. The lithium ion diffusion coefficient (10−16 m2 s−1) of LiFePO4 obtained from the phase transformation CV model was 2 orders of magnitude higher than apparent values (10−18 m2 s−1) determined from traditional CV. The low diffusion coefficient from traditional CV is attributed to the disregard of phase transformation. In addition to the lithium ion diffusion coefficient, the interface mobility (on the magnitude of 10−14 m mol J−1 s−1) of the LiFePO4 electrode, which cannot be measured from traditional CV, was obtained using phase transformation CV. Using the phase transformation CV model, the CV curves of LiFePO4 and LiMnPO4 phase transformation electrodes were characterized, and the effects of lithium ion diffusion coefficient, interface mobility, exchange current density, and particle size on the CV profiles of phase transformation electrodes were systemically investigated.