Discharge model for the lithium iron-phosphate electrode
This paper develops a mathematical model for lithium intercalation and phase change in an iron phosphate-based lithium-ion cell in order to understand the cause for the low power capability of the material. The juxtaposition of the two phases is assumed to be in the form of a shrinking core, where a shell of one phase covers a core of the second phase. Diffusion of lithium through the shell and the movement of the phase interface are described and incorporated into a porous electrode model consisting of two different particle sizes. Open-circuit measurements are used to estimate the composition ranges of the single-phase region. Model-experimental comparisons under constant current show that ohmic drops in the matrix phase, contact resistances between the current collector and the porous matrix, and transport limitations in the iron phosphate particle limit the power capability of the cells. Various design options, consisting of decreasing the ohmic drops, using smaller particles, and substituting the liquid electrolyte by a gel are explored, and their relative importance discussed. The model developed in this paper can be used as a means of optimizing the cell design to suit a particular application.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE. Assistant Secretary for Energy Efficiency and Renewable Energy. Office of FreedomCAR and Vehicle Technologies Program (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 836399
- Report Number(s):
- LBNL-55444; R&D Project: 476701; TRN: US200503%%529
- Journal Information:
- The Journal of the Electrochemical Society, Vol. 151, Issue 10; Other Information: Submitted to The Journal of the Electrochemical Society: Volume 151, No.10; Journal Publication Date: 2004; PBD: 28 Feb 2004
- Country of Publication:
- United States
- Language:
- English
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