Electrochemical-Thermal Coupling for Battery Thermal Runaway Prediction Under Nail Penetration Abuse
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Thermal runaway (TR) triggered by nail penetration remains a critical safety challenge for high-energy cylindrical Li-ion cells. This work presents a coupled electrochemical-TR modeling framework that connects a physics-based Doyle-Fuller-Newman (DFN) electrochemical-thermal model (solved using PyBaMM library) with a reduced TR kinetics model including decomposition reactions and nail-induced internal short circuit (ISC). DFN simulations are used offline to extract SOC-dependent open-circuit voltage and resistance maps drive the abuse solver, retaining electrochemical consistency at low computational cost. Nail penetration is represented through a SOC-dependent equivalent circuit predicting ISC current, Joule heating in the cell and nail, and electrical SOC depletion [1]. The TR model integrates Arrhenius-type SEI, anode, and cathode decomposition together with a chemical ISC term [2]. All are coupled to a lumped energy balance with convective and radiative losses. The model is validated against an original nail-penetration test on EVE 49650 cylindrical cells (5 mm nail, 30 mm penetration) with multiple circumferential surface thermocouples. The coupled model reproduces the experimentally observed two stages thermal response: an ISC/ohmic preheating phase followed by rapid acceleration to TR. This later yields a peak temperature around 640-650 K and a consistent post-peak cooling trend on the hottest channel. A heat-source breakdown shows that bulk ohmic heating and chemical ISC dominate escalation, while the nail primarily acts as the trigger by establishing the conductive pathway. Sensitivity studies link abuse outcome to state and design. Varying initial SOC shifts both TR triggered sensitivity and time-to-runaway, with a transition low-risk behavior at initial SOC lower than 0.4 to high-risk behavior at SOC0 higher than 0.6 under identical penetration conditions. Electrochemical parameter sweeps (electrode thickness, electrolyte conductivity) reveal critical changes in TR onset time and onset temperature. This framework supports safer cell design and thermal management strategies.
