Temperature strongly impacts battery performance, safety and durability, but modelling heat transfer requires accurately measured thermal properties. Herein we propose new approaches to characterise the heat capacity and anisotropic thermal‐conductivity components for lithium‐ion pouch cells. Heat capacity was estimated by applying Newton's law of cooling to an insulated container within which the cell was submerged in warmed dielectric fluid. Thermal conductivity was quantified by heating one side of the cell and measuring the opposing temperature distribution with infra‐red thermography, then inverse modelling with the anisotropic heat equation. Experiments were performed on commercial 20 Ah lithium iron phosphate (LFP) pouch cells. At 100 % state‐of‐charge (SOC), the heat capacity of a 489 g, 224 mL pouch cell was 541 J K⁻¹. The through‐plane and in‐plane thermal conductivities were respectively 0.52 and 26.6 W m⁻¹ K⁻². Capturing anisotropies in conductivity is important for accurate thermal simulations. State‐of‐charge dependence was also probed by testing at 50 % SOC: the heat capacity dropped by 6 % and thermal conductivity did not significantly change.

Untangling the relationship between reactions, mass transfer, and temperature within lithium-ion batteries enables approaches to mitigate thermal hot spots and slow degradation. Here, we develop an efficient physics-based three-dimensional model to simulate lock-in thermography experiments, which synchronously record the applied current, cell voltage, and surface-temperature distribution from commercial lithium iron phosphate pouch cells. We extend an earlier streamlined model based on the popular Doyle–Fuller–Newman theory, augmented by a local heat balance. The experimental data reveal significant in-plane temperature non-uniformity during battery charging and discharging, which we rationalize with a multiscale coupling between heat flow and solid-state diffusion, in particular microscopic lithium intercalation within the electrodes. Simulations are exploited to quantify properties, which we validate against a fast full-discharge experiment. Our work suggests the possibility that non-uniform thermal states could offer a window into—and a diagnostic tool for—the microscopic processes underlying battery performance and cycle life.

The rising demand to electrify power‐intensive energy devices and systems, as well as fast charging, has imposed a great challenge in current chemistries for lithium‐ion batteries (LIBs), whose rate capabilities are predominantly restricted by the conventional graphite anode. Niobium pentoxide (Nb₂O₅) is a promising high‐rate anode material for LIBs with extraordinary rate performance beyond 5 C and good theoretical capacity (~202 mAh ⋅ g⁻¹). With many possible crystal structures, Nb₂O₅ has a complicated family of different polymorphs, each of which can possess distinct electrochemical properties, specific capacity, cycling stability, and rate capability. This special feature of Nb₂O₅ makes it a challenging material to understand and requires a comprehensive investigation of every one of its polymorphs. In this paper, we summarize the state‐of‐the‐art research on Nb₂O₅ polymorphs for LIBs, with an emphasis on the advanced characterisation techniques that have been used to probe the electrochemical processes of Nb₂O₅. Key findings related to Nb₂O₅ that have emerged from the previous studies are highlighted, and new scientific questions that are important for its scale‐up and commercialization are proposed for future research.