In-plane nonuniform temperature effects on the performance of a large-format lithium-ion pouch cell

Due to the temperature sensitive behavior of lithium-ion batteries a thermal management system (TMS) is typically integrated into the battery pack design. This system plays a crucial role in the total battery pack performance. During operation the TMS will induce nonuniform temperature distributions within the cells of the pack, due to relatively low cell thermal conductivity. However, limited research has been published regarding the effects of thermal nonuniformity throughout a cell, module, or pack. Understanding these effects will be beneficial to heat exchanger design and TMS control strategy optimization. Here, an experimental investigation is performed where fixed one-dimensional temperature distributions, emulating the effects of edge-based heat transfer, are applied across the face of a 10Ah NiCoMn Li-ion pouch cell. Average cell temperature conditions of 15, 25, and 35 °C with edge-to-edge temperature differences (ΔT) of 0, 5, 10, and 20 °C are applied. At each thermal treatment the effects on: (1) the pulse resistance at 50% state of charge, (2) the bulk resistance on a Charge-Depleting US06 power profile, and (3) the overpotential during Constant-Current charge are investigated. Pulse resistance is decreased with increased ΔT. However, the discharge resistance on the Charge-Depleting cycle was increased with increased ΔT. The Constant-Current charging overpotential (and therefore resistance) was also increased with increased ΔT. All effects are largest at 15 °C, and negligible at 35 °C.