Maintaining a 2170 lithium-ion battery's operating temperature in freezing climates using preheating and an alumina foam PCM structure.

This study develops a combined preheating and passive cooling strategy to maintain a 2170 lithium-ion battery (LIB) within its optimal operating temperature range of 15-35 °C under freezing conditions. A computational fluid dynamics (CFD) model based on the finite volume method (FVM) is employed to simulate a thermal management structure composed of high-porosity Al₂O₃ foam (ε = 0.9) impregnated with hexadecane as the phase change material (PCM), coupled with an external preheating technique. This work provides a system-level assessment of preheating duration, energy consumption, PCM utilization, and thermal regulation under extreme cold-start conditions down to - 40 °C, demonstrating stable temperature uniformity, effective latent heat absorption, and improved thermal safety for cold-climate battery applications. The results show that the preheating stage effectively raises the cell temperature to 15 °C, while the PCM-Al₂O₃ foam matrix maintains the temperature below 35 °C during discharge. Across all operating conditions, both the average temperature (Tavg) and maximum temperature (Tmax) increase with C-rate and environmental temperature. At low C-rates (1-2 C), the available PCM capacity is sufficient to maintain Tavg = 20 °C and keep Tmax near this level until the end of discharge, whereas at higher C-rates (3-4 C), Tavg and Tmax rise above 20 °C once the PCM approaches complete melting.