Thermodynamically Consistent Analysis for Lithium-Ion Batteries
Abstract
An approach for the numerical modelling of Lithium Plating on intercalation electrodes with or without phase transition using a thermodynamically consistent (TC) solid-state transport is presented for a positive electrode (Nickel-Cobalt-Aluminum oxide) and a negative electrode (Lithiated graphite). The proposed method considers the positive electrode to be a single-phase regime and the graphite to consist of three phases, each with a Nernstian Equilibrium potential. The phase transition and volume fraction of the species are directly related through modifications to the Avrami’s equation. A thermodynamically consistent approach is used to match experimental results to models at high C-rates (greater than 0.25C). The effect of using thermodynamically consistent approach on discharge/charge is obtained for varying performance characteristics (C-rate, size of particle). The visualization of phase change in graphite is captured through the assumption that each phase of graphite (LiC6, LiC12 and LiC32) are each represented by a sphere whose diffusivity is equal to the diffusivity of the phase. Lithium plating is considered to occur at negative overpotentials that are created locally, through low temperature or high C-rates and is formulated as being a Butler-Volmer type current density which is then directly correlated to the thickness of the Lithium plated metal layer. The effect of temperature and C-rate is observed in this study. C-rate and temperature have equal impact on the performance of the electrode and the formation of lithium plating on the surface of the electrode.
Citation
Chakravarthy, Murali Srivatsa (2017). Thermodynamically Consistent Analysis for Lithium-Ion Batteries. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /187208.