Electrochemical-Thermal Modeling of Large-Format, Thin-Film, Lithium-Ion Batteries with Cocurrent and Countercurrent Tab Connections Using a Reduced-Order Model

Abstract

We derive and implement a new reduced-order model for the simulation of large-format, thin-film batteries with cocurrent and countercurrent tab connections. We employ the multi-site, multi-reaction (MSMR) framework to describe the solid phase thermodynamics as well as irreversible phenomena associated with diffusion and electrochemical reactions for a graphite negative and a spinel manganese oxide positive. The calculations are streamlined by using the reduced-order electrochemical model for a porous electrode derived by means of a perturbation analysis, which we term ROM1. For discharge rates less than 1 C, where the 1 C rate corresponds to the current needed to fully discharge the cell in 1 h, ROM1 yields accurate results for traction-battery electrodes. We employ ROM1 in the cell energy balance, with the overall results allowing one to clarify the current and temperature distributions within the cell during discharge and isolate and identify the different heat sources. The governing partial differential equations are coupled and nonlinear in part due to the temperature dependence of the physicochemical properties. We show how cocurrent tab locations yield higher cell energy densities, while countercurrent tab locations yield more uniform current and temperature distributions. Sensitivity analyses underscore the flexibility of the approach. Overall, the equation system and open-source (Python) software enables an efficient and rational tool for cell design and integration.