Galvanostatic Intermittent Titration Technique for Phase-Transformation Electrodes

Abstract

A novel galvanostatic intermittent titration technique (GITT) and a novel potentiostatic intermittent titration technique (PITT) for phase-transformation electrodes were developed by integrating mixed control phase-transformation theory with traditional GITT and PITT methods. The contribution of the strain accommodation energy to the thermodynamic driving force for phase transformation was assessed. These novel GITT and PITT methods can be used to determine the true ion diffusion coefficient and the interface mobility of phase-transformation electrodes in the two-phase region. To demonstrate the utility of this method, the lithium ion diffusion coefficient and the interface mobility of two LiFePO4 samples with different particle sizes were obtained in the two-phase region. The lithium ion diffusion coefficient in the two-phase region as measured using phase-transformation GITT was on the order of 10−13 cm2/s in the β phase (Li1−yFePO4) and 10−12 cm2/s in the α phase (LixFeO4), which is similar to the diff...