# A Review of Experimental and Numerical Studies of Lithium Ion Battery Fires
## 7 Conclusions  
A review of experimental and numerical studies was conducted, focusing on LIB chemistry, TR, SOC, incident heat flux, HRR, and various numerical modeling methods. The focus of these studies reported in the literature is largely directed toward understanding the parametric effects on TR and HRR. Based on this review, the following conclusions are formulated:  
1. The chemical composition of the battery changes both the likelihood of a LIB going into TR and the consequence (energy magnitude of the resultant HRR) for the resultant fire/explosion.  
2. The higher SOC leads to shorter time to TR and ignition, and larger magnitude of the rate of energy released (HRR).
3. HRR is considered a major factor after the LIB has gone into TR and the magnitude is directly proportional to the LIB chemistry, the SOC, and incident heat flux.
4. Three-dimensional thermal modeling is challenging. Accurate data for thermal property variables such as thermal conductivity, density, and specific heat are critical to LIB fire modeling. Determining how a test object reacts/changes with time in a fire scenario is critical to the boundary conditions required to complete accurate LIB fire modeling.
5. Three-dimensional thermal modeling has the potential to identify methods to be incorporated in systems to delay or inhibit TR, such as (a) modifying the separator, (b) varying the charging of the battery, (c) changing the convective heat transfer coefficient, and (d) adding additional thermal layers between adjacent batteries.  
We compiled HRR data from fire tests of different LIB composition with various SOC. As LIBs tested were of different shapes and sizes, we endeavored to normalize HRR in terms of per unit surface area (HRRPUA). CFD fire models (such as FDS) can specify the fire (as an input or source term) in terms of HRRPUA. We expect that fire modelers will be able to use these data combined with time to TR and TTI data to determine the consequence of LIB fires. However, more future studies need to be conducted to measure HRR magnitude as functions of various parameters so that better HRR function can be developed to use as input to CFD fire models to assess the fire risk. Future studies require more experimental investigations to determine the fire properties of the LIBs and identify very fine details of each chemical reaction, particularly around the time of TR initiation. Additionally, fire tests should involve more instrumentation to record temperatures of surfaces and at the various depths of the packaging, as well as gas temperatures and radiation flux at various distances from the LIBs. These would allow for conducting more faithful numerical simulations and validation. With additional experimental and numerical studies, solutions to prevent or delay TR for reducing fire risk can be found.  
It is also observed from this review that different battery testing protocols are used. Furthermore, anecdotal evidence suggests that manufacturers use different standards and protocols, which lead to variations in determining the state of the battery. Therefore, it is recommended that a collaborative effort be undertaken to develop a universal testing standard.  
**Author Contributions:** Conceptualization, writing--review and editing, data curation, visualization, and supervision, M.G.; writing--original draft, data curation, and visualization, S.E.; conceptualization, writing--review and editing, data curation, project administration, and supervision, K.M. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** No new data were created or analyzed in this study. Data sharing is not applicable to this article.  
**Conflicts of Interest:** The authors declare no conflict of interest.