Thermal Modeling of Porous Insertion Electrodes

Abstract

Isothermal calorimetry was performed on Li͉LiPF 6 in ethylene carbonate:dimethyl carbonate͉LiAl 0.2 Mn 1.8 O 4Ϫ␦ F 0.2 cells. The measured rate of heat generation varied substantially with time. To understand why, we investigated the entropy, irreversible resistance, and heats of mixing. Two methods for computing the heat of mixing, one computational and one analytic, are derived. We demonstrate how the energy balance of Rao and Newman accounts for heat of mixing across electrodes, but neglects heat of mixing within particles and in the electrolyte, which may be of equal magnitude. In general, the magnitude of the heat of mixing, which is the amount of heat released during relaxation after interruption of the current, will be small in materials with transport properties sufficiently high to provide acceptable battery performance, with the possible exception of heat of mixing within the insertion particles if the particle radius is large. Comparing simulations of heat generation to calorimetry measurements reveals that the entropic heat is significant and accounts for much of the variation of the rate of heat generation. The rate of irreversible heat generation is larger when the open-circuit potential varies steeply with lithium concentration, because of diffusion limitations within the solid.

Online Internal Temperature Estimation for Lithium-Ion Batteries Based on Kalman Filter

“…An expression for heat sources in a lithium-ion battery was presented by Thomas and Newman [13]. In their study, heat sources include the Joule heating, reversible entropic heat from the reaction, the heat produced from mixing and the heat from irreversible chemical reactions.…”

Smart Battery Thermal Management for PHEV Efficiency

“…Heat generation inside Li-ion batteries results from four phenomena [1][2][3]: -irreversible resistive heating (Joule heating), due to current flows through the internal resistance, causing a deviation of the cell potential from its equilibrium potential;…”

Macroscopic Modeling of Polymer-Electrolyte Membranes

“…Similarly, the effect of diffusion on heat flux, the Dufour effect, is likewise neglected [59]. In addition, heats of mixing for ideal gases are zero, and for the other components are assumed negligible [129]. Overall, since the above effects can usually be assumed negligible, the governing conservation and equations described in sections 3.1 and 3.2 remain valid and do not require alteration.…”

“…Newman and coworkers [59,128,129,188]. The irreversible heat generation is represented by the surface overpotential, and the reversible by the Peltier coefficient [189].…”