Numerical Simulation and in‑operando Measurement of the Local Temperature Evolution in a Lithium Ion Battery Cell

Aiming at a better quantitative understanding of the fundamental mechanisms that cause heat evolution in lithium ion batteries, theoretical modeling of the temperature evolution was performed associated with in-operando temperature measurements across the interfaces of a single lithium ion battery cell. For that purpose, an experimental setup has been developed at the Fraunhofer IKTS. The cylindrical electrode arrangement and the positioning of the thermocouples at specific interfaces within the lithium ion cell is illustrated in the figure. The success of this experimental approach has recently been demonstrated [1]. The present modeling is based on Newman's pseudo-2D model [2], extended however by including a radial spatial dependence of the electrochemical processes and SoC-dependent material properties. To evaluate the reliability of the electrochemical modeling, simulations of GITT experiments were compared with corresponding measurements using a 3-electrode arrangement. Calculations of the electric potential and current densities within the cell during charging and discharging yield the spatially resolved heat-source densities. The simulations enable the comparison of different contributions to the local heat generation. Reversible heat due to entropy changes, irreversible reaction heat, and ohmic heating within the electrode materials and the electrolyte are included in the temperature model as a function of the SoC for a wide range of charge/discharge rates. The effect of parameter variations on the temperature evolution has been extensively explored, particularly in view of different reported material properties [3]. Differences in the heat generation within the cathode, separator, and anode as a function of time, charge/discharge rate and SoC were successfully identified both theoretically and experimentally. Generally, the numerical results and the measurements reveal the significance of reversible heat effects due to electrochemical reactions under near equilibrium conditions, whereas Joule heating becomes important at high current densities. In-operando measurements allow time-resolved as well as SoC-dependend study of key parameters for the numerical simulation.  The present work magnificently show the strong relation between the fundamental electrochemical processes and the resulting heat impact.

 

[1] C. Heubner, M. Schneider, C. Lämmel, U. Langklotz, A. Michaelis; In-operando temperature measurement across the interfaces of a lithium-ion battery cell; Electrochim. Acta, 113 (2013) 730-734.

[2] M. Doyle, T.F. Fuller, J. Newman; Modeling of galvanostatic charge and discharge of the lithium/polymer/insertion cell;  J. Electrochem. Soc. 140 (1993) 1526-1533.

[3] M. Park, X. Zhang, M. Chung, G.B: Less, A.M. Sastry; A review of conduction phenomena in Li-ion batteries; J. Power Sources 195 (2010) 7904-7929