Temperature Behaviour of Li-Ion Batteries at High Discharging Current Degraded Using Different Methods: An Experimental Study

초록

As global demand for clean energy continues to grow, lithium-ion batteries (LIBs) have become vital for portable electronics, electric vehicles, and large-scale energy storage due to their high energy density, long cycle life, and compact design. However, this rising demand poses challenges for thermal management and safety, as repeated use leads to internal degradation. In this study, six nickel-cobalt-manganese oxide (NCM) pouch-type LIBs were degraded using three distinct methods-urban dynamometer driving schedule (UDDS), worldwide harmonized light vehicles test procedure (WLTP), and constant current (CC) cycling-until their state of health (SoH) declined from 100 to 90%. Infrared thermography (IRT) was employed to monitor the surface temperature, focusing on the evolution of the average temperature rise (Delta T) in relation to SoH, as well as the Delta T distribution across the surface and along lines parallel and perpendicular to the electrode direction at SoH levels of 100%, 95%, and 90%. The results indicate that when the SoH is greater than 98%, the average surface Delta T remains nearly identical across all groups. However, differences begin to emerge at 98% SoH, with WLTP-aged cells exhibiting higher average Delta T values. At 90% SoH, WLTP-aged batteries develop two regions of elevated Delta T near the electrode terminals, while CC- and UDDS-aged cells maintain a central concentration of heat. Additionally, WLTP-aged cells exhibit a two-stage temperature difference rise along the electrode direction, contrasting with the simpler unimodal profiles observed in other groups.

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