Abstract
Despite considerable worldwide efforts, safety issues due to thermal runaway (TR) still raise concerns for lithium-ion batteries (LIBs). Substantial efforts have been devoted to address TR due to thermal or mechanical abuse, relatively less investigations have been conducted for TR induced by slight overcharging cycling. This is partly due to the complexity and vast amount of interrelated information involved. Indeed, TR can be induced by slight overcharging due to inadequate design of battery management system (BMS) or unexpected malfunction of charger. The occurrence of TR from slight overcharge takes a lengthy incubation period, posing challenge for experimental investigations of either a single cell or cell clusters. Numerical study with validated models can potentially serve as a viable tool. In the present study, a coupled electrochemical and thermal model has been developed within the frame of open-source computational fluid dynamics (CFD) code OpenFOAM to capture the thermal runaway propagation (TRP) behavior induced by slight overcharging cycling in the cell cluster. Following validation with published single cell slight overcharge tests and TR propagation (TRP) tests in a cell cluster, the model was used to simulate (J.X. Wen). 2 TRP in a 5 × 9 LIB cluster. Parametric studies were conducted to investigate the effect of different insulating materials between the cells and their thicknesses on mitigating TRP. This was followed by further numerical simulations to examine the effect of environment temperatures. The results will be analyzed to formulate recommendations to improve safety of LIB modules and packs. Nomenclature H enthalpy (J⋅mol-3) Tc temperature of cell (K) A frequency factor (s-1) TISC additional factor (-) ai fitting coefficients for Y (-) Uocv open circuit voltage(V) b Seebeck coefficient (V⋅k-1) V battery operating voltage(V) bj fitting coefficients for U (-) Vcell battery volume (m 3) Cap battery capacity (Ah) Y electrochemical conductivity of the cell (S cm-2) Crate battery rate for charging and discharging (-) W specific components content in jelly roll (kg⋅m −3) Cp heat capacity at constant pressure (J⋅kg-1 ⋅K-1) Ea. activation energy (J⋅mol-1) Greek symbols h convective heat transfer coefficient (W⋅m −2 ⋅K −1) δ thickness of contact thermal resistance (m) I current (A) Δ filter size (m) J current density (A⋅cm-2) ε eddy dissipation rate (m 2 ⋅s-3) Qele electrical heat (W⋅m −3) κ thermal conductivity (W⋅m-1 ⋅K-1) Qirr irreversible heat (W⋅m −3) ρ density (kg⋅m-3) Qohm ohmic heat (W⋅m −3) σ scattering coefficient (-) Qp heat of polarization (W⋅m −3) QTR reaction heat (W⋅m −3) Subscript Qrev reversible heat (W⋅m −3) c lithium-ion battery Qsoc electrical heat released by the ISC (W⋅m −3) e electrolyte Qtranfer ambient heat transfer (W⋅m −3) f flame R universal gas constant (J⋅mol⋅K-1) g generated gases t time (s) t turbulence Tamb temperature of ambient (K) TR thermal runaway