Multiscale coupling of surface temperature with solid diffusion in large lithium-ion pouch cells

TL;DR

This paper presents a multiscale physics-based model linking surface temperature and solid diffusion in large lithium-ion pouch cells, aiding thermal management and material fingerprinting.

Contribution

It introduces an efficient coupled model that explains surface temperature nonuniformity by integrating heat flow and solid-state diffusion in large-format cells.

Findings

Multiscale coupling explains temperature nonuniformity.

Model accurately simulates commercial 20 Ah LFP cells.

Heat signatures can identify material properties.

Abstract

Untangling the relationship between reactions, mass transfer, and temperature within lithium-ion batteries enables control approaches that mitigate thermal hot spots and slow degradation. Here, we develop an efficient physics-based pouch-cell model to simulate lock-in thermography experiments, which synchronously record the applied current, cell voltage, and surface-temperature distribution. Prior modelling efforts have been confounded by experimental temperature profiles whose characteristics suggest anisotropic heat conduction. Accounting for a multiscale coupling between heat flow and solid-state diffusion rationalizes this surface-temperature nonuniformity. We extend an earlier streamlined model based on the popular Doyle--Fuller--Newman theory, augmented by a local heat balance. The reduced-order model is exploited to parametrize and simulate commercial 20 Ah lithium iron phosphate (LFP) cells at currents up to 80 A. This work highlights how microscopic intercalation processes produce distinctive macroscopic heat signatures in large-format cells, as well as how heat signatures can be exploited to fingerprint material properties.