Thermal Performance of Passive Cooling in 2170 Cylindrical Battery Modules

This study examines passive cooling strategies relevant to electric-aviation battery modules during thermal runaway (TR) and thermal runaway propagation (TRP) in a section containing 2170-format Li-ion cylindrical cells. TR kinetics of the solid, homogeneous, orthotropic jellyroll are modeled using a four-equation Arrhenius framework for nickel-cobalt-manganese (NCM) chemistry, including an internal short-circuit equation to capture electrical charge loss. Three-dimensional heat transfer simulations are used to analyze the heat propagation in the battery module section. The impact of air-fin bottom cooling is evaluated for four representative operating points of small electric aircraft – taxi (h = 5 W/m2K), take-off, climb, and cruise (h = 80 W/m2K). Two variants of inter-cell module potting are also studied: firstly, solid filled polyurethane, and secondly, a composite formulation with myristic acid as the phase-changing material (PCM) and a graphene thermal enhancer. The predicted delays between TR and TRP range from two to five minutes. Results indicate that cruise-condition cooling can extend the TRP delay by up to 83 % due to increased air speed and lower ambient temperatures. Secondly, the PCM composite potting delays TRP by up to 53 % through enhanced heat absorption. While complete quenching of TRP is not achieved, the combined effects could increase the delay time between TR and TRP by up to 140 %.