Simple Pulsing Experiment for Thermodynamic, Kinetic, and Transport Analysis of the Battery Cell

Title: Extracting Thermodynamic, Kinetic, and Transport Properties from Batteries Using a Simple Analytical Pulsing Protocol
Authors: Wood et al.,
Journal: Journal of the Electrochemical Society Link

This paper presents a novel, non-invasive pulsing protocol for analyzing lithium-ion battery (LIB) cells. This technique enables the extraction of key parameters for thermodynamic, kinetic, and transport properties through pulse profiles performed at specific C-rates. These parameters include the Gibbs free energy, exchange current density, and lithium-ion diffusion coefficient.

Thermodynamics: The thermodynamic properties are calculated using dQ/dV curves from open-circuit voltage (OCV) values across nine defined pulse cycles, effectively isolating thermodynamic contributions by neglecting overpotentials from kinetic and transport effects. The Gibbs free energy of reaction is then determined using the maximum dQ/dV value, revealing the purely thermodynamic energy associated with the reaction.

Kinetics: The kinetic properties are evaluated by analyzing cell potentials at the beginning of the pulse and at rest. The difference between these potentials represents the kinetic overpotential and the system’s internal resistance. Using the Butler-Volmer model, the exchange current density is then calculated.

Transport: Transport properties are derived from the potential at the beginning (i.e. end of the pulse phase) and end of the rest phase (i.e., equilibrium) following a pulse. This difference, combined with the current density, is applied in Fick’s law to determine the diffusion coefficient, with set boundary conditions.

This technique is reported to have a robust fundamental basis with minimal assumptions, providing accurate, quantifiable metrics for any cell form factor.