Analysis of the FePO4 to LiFePO4 phase transition

The electrochemical phase transformation of carbon coated nanophase (60–70 nm) FePO4 to LiFePO4 was investigated by use of the Avrami–Johnson–Mehl–Eroofev equation. The analysis at three temperatures showed an Avrami exponent equal to one. Based upon reinterpretation and in agreement with recent microstructural evidence, a two-dimensional growth mechanism for the phase transformation is proposed in which the new phase grows in a direction perpendicular to the direction of lithium ion transport. Furthermore, the relatively low value of the activation energy for the phase transformation of 13 kJ/mol suggests that the phase transition is controlled by lithium ion diffusion along the phase boundary.

[1]  Jeff Wolfenstine,et al.  Kinetic Study of the Electrochemical FePO 4 to LiFePO 4 Phase Transition , 2007 .

[2]  Peter R. Slater,et al.  Atomic-Scale Investigation of Defects, Dopants, and Lithium Transport in the LiFePO4 Olivine-Type Battery Material , 2005 .

[3]  P. A. Barnes.  Comprehensive chemical kinetics, Vol. 22. Reactions in the solid state. : Edited by C.H. Bamford and C.F.H. Tipper, Elsevier, Amsterdam, 1980, 340 pp. , 1980 .

[4]  M. Avrami.  Kinetics of Phase Change. I General Theory , 1939 .

[5]  K. Easterling,et al.  Phase Transformations in Metals and Alloys , 2021 .

[6]  Anthony R. West,et al.  Solid State Chemistry and its Applications , 1984 .

[7]  Yoji Sakurai,et al.  Reaction behavior of LiFePO4 as a cathode material for rechargeable lithium batteries , 2002 .

[8]  K. Jacobsen,et al.  Softening of nanocrystalline metals at very small grain sizes , 1998, Nature.

[9]  M. Avrami.  Kinetics of Phase Change. II Transformation‐Time Relations for Random Distribution of Nuclei , 1940 .

[10]  Dane Morgan,et al.  Li Conductivity in Li x MPO 4 ( M = Mn , Fe , Co , Ni ) Olivine Materials , 2004 .

[11]  A. Petford-Long,et al.  Determination of the isothermal nucleation and growth parameters for the crystallization of thin Ge2Sb2Te5 films , 2002 .

[12]  K. S. Nanjundaswamy,et al.  Phospho‐olivines as Positive‐Electrode Materials for Rechargeable Lithium Batteries , 1997 .

[13]  Venkat Srinivasan,et al.  Discharge Model for the Lithium Iron-Phosphate Electrode , 2004 .

[14]  G. Corbel,et al.  Isothermal kinetic of phase transformation and mixed electrical conductivity in Bi3NbO7 , 2006 .

[15]  Thomas J. Richardson,et al.  Electron Microscopy Study of the LiFePO4 to FePO4 Phase Transition , 2006 .

[16]  S. Ranganathan,et al.  The three activation energies with isothermal transformations: applications to metallic glasses , 1981 .