Periodic Reporting for period 1 - LiBTR (Modelling of thermal runaway propagation in lithium-ion battery packs)
Reporting period: 2021-11-03 to 2023-11-02
The need to alleviate energy crisis and de-carbonize has promoted a rapid expansion of the electrification for transport and energy storage. With relatively high energy density, extended cycle lifespan and trivial environmental pollution, lithium-ion batteries (LIBs) have been utilized as the most promising energy storage devices of electric vehicles (EVs) and energy storage systems (ESS). However, the potential safety problems of lithium ion batteries, especially the proliferating fire and explosion accidents resulted from thermal runaway (TR) , cause disastrous damages to economy and life safety of consumers and undermine their confidence on LIBs, which therefore are the existing obstructions of the generalization of LIBs.
Safety issues due to thermal runaway (TR) of lithium-ion batteries are the main obstacles that hinder their wider applications. A comprehensive model can potentially help improve understanding of the TR mechanisms and improve battery pack design.
The research aims to develop and validate a predictive tool for TR propagation in LIB packs based on LibFOAM the single cell TR model developed by the host and FireFOAM, the fire simulation solver of open source CFD code OpenFOAM. The following specific research objectives are set towards achieving this goal:
Calibrate LibFOAM for predicting the onset of TR in a single cell under different failure modes and establish the key influencing parameters;
Extend LibFOAM by coupling it with FireFOAM to predict the release of gases prior to and following TR initiation in the triggering cell as well as the subsequent ignition and combustion of the released gases to obtain the resulting thermal environment within the cell groups;
Further extend LibFOAM to predict TR propagation in battery modules and packs;
Validated the extended LibFOAM with experimental data in the literature and data to be generated by the ER’s home institution as well as proprietary data from the UK Health and Safety Executive (HSE) in an ongoing collaborative project;
Use the validated LibFOAM to investigate the effects of different mitigation measures to inhibit TR propagation
Safety issues due to thermal runaway (TR) of lithium-ion batteries are the main obstacles that hinder their wider applications. A comprehensive model can potentially help improve understanding of the TR mechanisms and improve battery pack design.
The research aims to develop and validate a predictive tool for TR propagation in LIB packs based on LibFOAM the single cell TR model developed by the host and FireFOAM, the fire simulation solver of open source CFD code OpenFOAM. The following specific research objectives are set towards achieving this goal:
Calibrate LibFOAM for predicting the onset of TR in a single cell under different failure modes and establish the key influencing parameters;
Extend LibFOAM by coupling it with FireFOAM to predict the release of gases prior to and following TR initiation in the triggering cell as well as the subsequent ignition and combustion of the released gases to obtain the resulting thermal environment within the cell groups;
Further extend LibFOAM to predict TR propagation in battery modules and packs;
Validated the extended LibFOAM with experimental data in the literature and data to be generated by the ER’s home institution as well as proprietary data from the UK Health and Safety Executive (HSE) in an ongoing collaborative project;
Use the validated LibFOAM to investigate the effects of different mitigation measures to inhibit TR propagation
As thermal abuse is one of the most common cause for the thermal runaway (TR) of lithium ion battery (LIB), a three-dimensional model was firstly developed within frame of open source computational fluid dynamics (CFD) code OpenFOAM to study the effects of various battery materials, external heating conditions and heat dissipation conditions on battery thermal runaway behavior. The developed model was validated by the measurements for LiCoO2 (LCO), LiNi0.8Co0.15Al0.05O2 (NCA) and LiFePO4 (LFP) cells, which shows good agreement with experimental results. The validated model was then applied to investigate and rank the thermal safety and thermal stability of different battery materials (i.e. cathode, anode, electrolyte and separator) from the perspective of heat generation. The results indicate that batteries with Li4Ti5O12 anode and LiFePO4 cathode show better thermal safety and stability than other materials.
In addition to the thermal abuse, the electrical abuse condition is also a common cause to induce the thermal runaway of LIBs. Slight overcharge of LIBs could occur due to inadequate design of battery management system or unexpected malfunction of charger. As slight overcharging is difficult to detect, the generated heat could easily accumulate as the cycle process prevails, result in unwanted cell temperature increases with propensity for TR. A three-dimensional (3-D) predictive tool for the transition of the cylindrical 21700 LIB from slight overcharging cycle to TR was developed by implementing the published models for heat generation from various thermal decomposition reactions and ISC into in-house version of the opensource CFD code OpenFOAM. The code is validated with newly conducted experiments involving both normal cycle and a slight overcharging. The predicted cell temperature and voltage evolution during normal cycle and adiabatic condition have achieved reasonably good agreement with the measurements.
The above studies received attentions from the international peers. For example, the well-known expert in the field of thermal safety of lithium ion batteries, Academician of the Chinese Academy of Sciences, Prof. Minggao Ouyang from Tsinghua University has cited the ER’s studies in his several published papers (Appl. Therm. Eng. 2021, 199:117521; J. Power Sources 2021, 504:230065; Energy, 2023, 268:126646), and positively affirmed that “Kong et al. [32] developed a 3D electro-thermal model using the OpenFOAM platform with good experimental validation. The results revealed that the battery composed of a Li4Ti5O12 anode and LiFePO4 cathode is safer than others”.
In addition, a multi-scale and multiphase modelling framework was firstly proposed to predict the multiphase venting process of the LIB single cell due to TR. The proposed model covered the entire chain of chemical reactions and physical transformation during TR. A lumped model in battery cell scale unveiled the interplay of thermal abuse progression and pressure accumulation. The CFD model coupled with the discrete phase model (DPM) was adopted to simulate both generated gases and ejected particles.
After developing the TR, venting and jet fire model for a single cell, we developed a model framework based on the conjugate heat transfer to predict the TR propagation behaviour considering the interaction between jet fire and TR propagation in module. Simulation results demonstrate that increasing the space confinement degrees shortens the propagation time interval by enhancing the convection from ejected gases and the radiation from flame. The reduction of ceiling height extends the flame extension length and significantly accelerates the cell-to- cell failure, highlighting the impacts of jet fire on TR propagation.
In addition to the thermal abuse, the electrical abuse condition is also a common cause to induce the thermal runaway of LIBs. Slight overcharge of LIBs could occur due to inadequate design of battery management system or unexpected malfunction of charger. As slight overcharging is difficult to detect, the generated heat could easily accumulate as the cycle process prevails, result in unwanted cell temperature increases with propensity for TR. A three-dimensional (3-D) predictive tool for the transition of the cylindrical 21700 LIB from slight overcharging cycle to TR was developed by implementing the published models for heat generation from various thermal decomposition reactions and ISC into in-house version of the opensource CFD code OpenFOAM. The code is validated with newly conducted experiments involving both normal cycle and a slight overcharging. The predicted cell temperature and voltage evolution during normal cycle and adiabatic condition have achieved reasonably good agreement with the measurements.
The above studies received attentions from the international peers. For example, the well-known expert in the field of thermal safety of lithium ion batteries, Academician of the Chinese Academy of Sciences, Prof. Minggao Ouyang from Tsinghua University has cited the ER’s studies in his several published papers (Appl. Therm. Eng. 2021, 199:117521; J. Power Sources 2021, 504:230065; Energy, 2023, 268:126646), and positively affirmed that “Kong et al. [32] developed a 3D electro-thermal model using the OpenFOAM platform with good experimental validation. The results revealed that the battery composed of a Li4Ti5O12 anode and LiFePO4 cathode is safer than others”.
In addition, a multi-scale and multiphase modelling framework was firstly proposed to predict the multiphase venting process of the LIB single cell due to TR. The proposed model covered the entire chain of chemical reactions and physical transformation during TR. A lumped model in battery cell scale unveiled the interplay of thermal abuse progression and pressure accumulation. The CFD model coupled with the discrete phase model (DPM) was adopted to simulate both generated gases and ejected particles.
After developing the TR, venting and jet fire model for a single cell, we developed a model framework based on the conjugate heat transfer to predict the TR propagation behaviour considering the interaction between jet fire and TR propagation in module. Simulation results demonstrate that increasing the space confinement degrees shortens the propagation time interval by enhancing the convection from ejected gases and the radiation from flame. The reduction of ceiling height extends the flame extension length and significantly accelerates the cell-to- cell failure, highlighting the impacts of jet fire on TR propagation.
The results have been communicated to both academia and industries, attracting a lot of interest and opening up new opportunities to the ER in terms of career development.
Immediate opportunities for knowledge transfer and exploitation include the existing industrial sponsors and the extensive network of the host’s collaborators from the LIB and automotive industry including Jaguar Land Rover and Tata motor. There will also be opportunities to transfer knowledge through our long-term sponsor FM Global which has offices in many different countries in Europe to improve the safety of LIB by their clients such as LIB storage in warehouses.
The developed models in this project will be actively promoted to potential end users in the LIB industry such as the industry of electric vehicle and battery energy storage and regulatory bodies through the planned activities described above to facilitate commercial exploitation. Some top energy storage manufacture, such as SUNGROW, Huawei Digital Energy show great interest in employing the developed models in this project for TR risk assessment and improving the safety performance of their battery module or pack products.
Immediate opportunities for knowledge transfer and exploitation include the existing industrial sponsors and the extensive network of the host’s collaborators from the LIB and automotive industry including Jaguar Land Rover and Tata motor. There will also be opportunities to transfer knowledge through our long-term sponsor FM Global which has offices in many different countries in Europe to improve the safety of LIB by their clients such as LIB storage in warehouses.
The developed models in this project will be actively promoted to potential end users in the LIB industry such as the industry of electric vehicle and battery energy storage and regulatory bodies through the planned activities described above to facilitate commercial exploitation. Some top energy storage manufacture, such as SUNGROW, Huawei Digital Energy show great interest in employing the developed models in this project for TR risk assessment and improving the safety performance of their battery module or pack products.