Novel Electro-Analytical Tools for Phase-Transformation Electrode Materials
Final rept. 1 Sep 2008-1 Jun 2009
MARYLAND UNIV COLLEGE PARK DEPT OF CHEMICAL AND BIOMOLECULAR ENGINEERING
Pagination or Media Count:
We measured and compared phase transformation accommodation energy AE for Li4Ti5O12 and LiFePO4 with different particle size by using of galvanostatic intermittent titration GITT. The results showed that charge AE was larger than that for discharge The AE for the 1st cycle was larger than next cycles due to inducing of defects Because of smaller volume difference, AE of Li4Ti5O12 was lower than that of LiFePO4 AE of LiFePO4 with small particle size was lower than that of LiFePO4 with large particle size. By plugging the AE measured by GITT into mixed control model, we simulated the discharge curves in GITT and obtained lithium ion diffusivity in alpha DalphaLi and Beta DBeta Li phase and interface mobility M during phase transformation for Li4Ti5O12 and LiFePO4 respectively. For LiFePO4 DalphaLi tilde 10-14-10-13 cm2s, DBetaLi tilde 10-15 - 10-14 cm 2s and M tilde 10-15 mmolJs for Li4Ti5O12DalphaLi tilde 10-11-10-10cm2s, DBetaLi tilde 10-12-10-11cm2s and M tilde 10-13 mmolJs. The values of DalphaLi and DbetaLi calculated by mixed control theory were consistent with those gained in one phase region according to traditional GITT and potentiostatic intermittent titration PITT method. We also discovered the effects of phase transformation on cyclic voltammetry CV, and electromechanical impedance spectroscopy EIS tests.
- Physical Chemistry
- Electrochemical Energy Storage