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

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 reducedorder 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.

Anisotropic thermal characterisation of large-format lithium-ion pouch cells

“…For large-format pouch cells operating at high C-rates, high temperatures and spatial temperature non-uniformities may occur depending on the spatial distribution of electrochemical reactions within the cell [8] and the cooling arrangement. The heat-management challenge has motivated research to develop more thermally conductive electrodes [9], effective thermal management techniques [10,11,12] and improved thermoelectrochemical models [13,14,15,16].…”