Characterization of Lithium-Ion Battery Fire Emissions—Part 1: Chemical Composition of Fine Particles (PM_2.5)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this work, the authors conducted comprehensive research on lithium-ion battery fire emissions, especially regarding the fine particles PM2.5. The topic is interesting, and the manuscript presented the results clearly. These are my suggestions for improving the manuscript’s readability.

 

Since there are many acronyms involved in this manuscript, it would be better if there was a list of them.

Although it was stated that PM2.5 is a threat to human health, not much content was included in the introduction section. This may not be the major focus of the current work. Still, it would be helpful if the authors could talk about what makes PM2.5 different from solid and gaseous pollution generated from battery thermal runways in regard to their short- and long-term impact on humans.

Page 3, for the two types of batteries involved in these tests, there are significant differences in their venting triggering pressures. For example, cylindrical cells can hold the accumulated gases till the internal pressure reaches about 1~2 MPa. This difference causes a difference in the formed gas and the combustion behavior. Is it legit to compare their results directly?

Page 3, line 126, NMC is not just being historically used, but still the dominating cell chemistry at this moment. Please verify.

 

This work involved a lot of effort in presenting the collected data. Still, it seems that the conclusion is merely a summary of observations and lacks the interpretation and suggestions for how to make use of these results. This can hinder the novelty and importance of this work. It is recommended that the authors add suggestions about measures to reduce the impact of PM2.5. For example, in terms of respiratory protection, which kind of mask would be a suitable selection? Is an organic vapor filter needed? How long can certain masks or filters withstand the hazardous particles? Since the water-soluble ions were studied, should water be used to absorb the PM2.5, or should water cause any secondary hazard and thus be avoided? I understand that this is just the first part of a series study and that not all the questions mentioned above can be answered right away, but it is expected that such questions will be considered and will add some corresponding guidance for the benefit of the potential audience. 

Author Response

Please see attached response.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This work characterizes the chemical composition of PM2.5 released from thermal runaway driven combustion of cylindrical lithium iron phosphate and pouch-style lithium cobalt oxide LIB cells, as well as measures the emissions produced by battery venting and flame combustion. The overall quality of the manuscript is good and some minor issues should be resolved before considering acceptance.

1. In introduction, “To the best of our knowledge, no studies have reported detailed chemical composition of PM2.5 from LIB fires.” This is not correct. The following works are included here for reference.(DOI: org/10.1016/j.jaerosci.2024.106420, DOI: org/10.1016/j.applthermaleng.2024.123193, DOI: org/10.1080/02786826.2021.2018399)

2. In Materials and Methods, provide more detailed descriptions of the experimental procedures, especially regarding the setup of instruments. Please Specify the production time and source of the batteries used in the tests

3. It is not clear to me how the PM2.5 samples were processed and analyzed for chemical composition. Please add a bit more information.

4. In Section 3.1, clarify the ignition method of battery thermal runaway: is it auto-ignition or ignited by an electric spark?

5. In Section 3, the test results show that in PM2.5, LCO contains more elements: C, O, P, F, Li, Mg, Al, Ca, Fe, and Zn; while LFP contains more elements: C, O, P, F, Mg, Al, Ca, Fe, Ni, and Zn. In contrast, a recent work (DOI: org/10.1016/j.jaerosci.2024.106420) using XPS results showed that the soot produced by lithium iron phosphate batteries contains more elements such as C, O, F, Fe, Li, and P, while ternary lithium batteries contain more elements such as C, O, F, Co, Mn, Li, and P. The authors should explain why the elemental distribution of LFP and LCO in this study differs from other studies. Is it due to different experimental conditions, sample processing methods, or measurement techniques? Additionally, do different battery formulations, aging degrees, or operating conditions affect the release and detection of elements?

8. Please explain the reasons for the differences in the proportions and types of elements in PM2.5 for different types of batteries under various SOC conditions.

9. In section 4, it is mentioned that particles emitted from LIB fires can have adverse effects on human respiratory tract. However, there is no discussion of research papers that are highly relevant to the health hazards of battery smoke. It is suggested to supplement relevant literature for discussion. (https://doi.org/10.1016/j.jaerosci.2024.106420).

Author Response

Please see attached response.

Author Response File: Author Response.docx