A coupled electrothermal lithium-ion battery reduced-order model including heat generation due to solid diffusion

Temperature constitutes a critical variable in the operation of lithium-ion batteries, given its major influence on their behavior, as well as for safety reasons in real-world applications. Therefore, it is imperative to develop accurate thermal models along with precise cell characterizations at different ambient temperatures. These two aspects are often analyzed independently; however, a coupled modeling approach is required in order to replicate cell behavior in a broad range of operating scenarios due to non-negligible self-heating. In this article, we present a coupled electrothermal reduced-order model which is able to yield highly accurate results upon validation against experimental data, both in output voltage (≤ 25 mV RMS) and cell temperature (≤0.68°C RMS) at a low computational cost with a unique set of 7 well-defined parameters, in the range from 50 °C to 0 °C ambient temperatures. A key idea is the consideration of the contributions of entropic heat and solid diffusion to overall heat generation, which proves to be necessary so as to qualitatively and quantitatively explain the evolution of cell temperature throughout a full discharge. The proposed model provides an excellent trade-off between accuracy and computational and parameterization complexities in a wide interval of operating conditions, therefore being suitable alternative for its implementation in practical applications.