Stochastic many-particle model for LFP electrodes

Clemens Guhlke, Paul Gajewski, Mario Maurelli, Peter K. Friz, Wolfgang Dreyer

Research output: Contribution to journalArticlepeer-review

Abstract

In the framework of non-equilibrium thermodynamics, we derive a new model for many-particle electrodes. The model is applied to LiFePO 4
LiFePO4
(LFP) electrodes consisting of many LFP particles of nanometer size. The phase transition from a lithium-poor to a lithium-rich phase within LFP electrodes is controlled by both different particle sizes and surface fluctuations leading to a system of stochastic differential equations. An explicit relation between battery voltage and current controlled by the thermodynamic state variables is derived. This voltage–current relation reveals that in thin LFP electrodes lithium intercalation from the particle surfaces into the LFP particles is the principal rate-limiting process. There are only two constant kinetic parameters in the model describing the intercalation rate and the fluctuation strength, respectively. The model correctly predicts several features of LFP electrodes, viz. the phase transition, the observed voltage plateaus, hysteresis and the rate-limiting capacity. Moreover we study the impact of both the particle size distribution and the active surface area on the voltage–charge characteristics of the electrode. Finally we carefully discuss the phase transition for varying charging/discharging rates.
Original languageEnglish
Pages (from-to)593-628
Number of pages36
JournalContinuum Mechanics and Thermodynamics
Volume30
Issue number3
Early online date5 Feb 2018
DOIs
Publication statusPublished - May 2018

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