Safety of lithium ion batteries

Through a series of projects funded by the European Commission and Innovate UK, we are carrying out analytical, experimental, and numerical studies of thermal runaway in lithium-ion batteries with particular focus on the mechanisms of thermal runaway and its propagation in lithium-ion batteries clusters and modules.

Overview

Within the frame of OpenFOAM, a dedicated in-house LibFOAM solver has been developed and validated to address the following:

An electrothermal model to capture the evolution from normal operation to abuse condition and thermal runaway
A vent model to predict the internal pressure evolution during lithium-ion battery thermal runaway
A coupled venting, ejection and fire model for predicting thermal runaway propagation in lithium-ion battery clusters

Publications

Shelke, Ashish V., Buston, Jonathan E. H., Gill, Jason, Howard, Daniel, Williams, Rhiannon C. E., Read, Elliott, Abaza, Ahmed, Cooper, Brian, Richards, Philip and Wen, Jennifer X. (2022) Combined numerical and experimental studies of 21700 lithium-ion battery thermal runaway induced by different thermal abuse . International Journal of Heat and Mass Transfer, 194, 123099. doi: 10.1016/j.ijheatmasstransfer.2022.123099 .

Thermal runaway evolution

Thermal runaway induced by thermal abuse

Combined numerical and experimental studies (in collaboration with the UK Health and Safety Executive Science Division) have been carried out to investigate thermal runaway of large format 21700 cylindrical lithium-ion batteries induced by different thermal abuse. Experiments were conducted using extend volume accelerating calorimetry (EV-ARC) with both the heat-wait-seek (HWS) protocol and under isothermal conditions.

The kinetic parameters were derived from one of the HWS EV-ARC tests and implemented in a modified computational fluid dynamics OpenFOAM model. For the simulations, the cell was treated as a three-dimensional block with anisotropic thermal conductivities.

The model was verified using two additional heat-wait-seek tests and validated with newly conducted isothermal EV-ARC tests. Further laboratory validation was conducted using Kanthal wire heaters. The validated model was used to predict onset temperature, heat generation rate under different abuse reactions, the influence of heating power and arrangement, and the effect of heat dissipation on thermal runaway evolution and battery thermal management.

Thermal runaway induced by nail penetration

A modelling approach has been developed considering the cell as a lumped block with anisotropic thermal conductivities. The model incorporates heat generation due to penetration induced internal short circuit and exothermic decomposition reactions as well as heat dissipation through convective and radiative heat transfer. Validation has been conducted with the current experimental measurements.

The predictions have also been used to analyse the relative contributions to heat generation due to internal short circuit and decompositions of the component materials including solid electrolyte interphase layer, anode, cathode and electrolyte.

Venting during thermal runaway

The cell internal pressure evolution predicted by the analytical model

An analytical model has been developed to predict cell lithium-ion batteries internal pressure evolution following vent opening. The model uses the measured cell internal temperature and EV-ARC canister pressure as input data.

Its predictions serve as boundary condition in the three-dimensional computational fluid dynamics simulation of thermal runaway induced fire using opensource code OpenFOAM.

Battery fires and thermal runaway propagation

A predictive tool for simulating lithium-ion batteries fires and thermal runaway propagation in cell clusters/modules has been developed by coupling LIBFOAM with the in-house modified FireFOAM, quantifying the heat release rate and temperature evolution during lithium-ion batteries thermal runaway.