Dynamic Mechanical Compression Impulse of Lithium-Ion Pouch Cells
Round 1
Reviewer 1 Report
The authors investigated strain rate sensitivity of the dynamic mechanical properties of lithium-ion cells. They were determined by drop water impact testing, using a diaphragm to minimize transient shock loads and to constrain off-axis motion of the indenter. It was found that inert pouch cells do not recover under the weight of the indenter, suggesting that a highly damped foam material model can be used to delineate dynamic mechanical properties of the inert pouch cells. This study provides a new method for the accurate evaluation of the safety of lithium-ion batteries under impact, which shows great significance in modern lithium-ion battery industry. The newly proposed model not only attracts the scientists in the mechanical area, but the engineers in the battery field. Hence, we believe the quality of this manuscript meets the high criterion of the journal, which can be accepted. Some comments are lists as follows:
- Figure 15 and Figure 16 show the load and displacement for inert pouch cells separately. Figure 17 presents the relationship between the load and displacement. Is there any possible reason for the fluctuation of the displacement with the increase of the load?
- In Figure 17, the displacement was depicted in the range of 0.13 – 0.52 mm. Since this relationship is constructed based on the Figure 15 and Figure 16 in the range of 0 – 0.7 mm, why the author does not present the data beyond this range (displacement < 0.13 nm or displacement > 0.52 nm)?
- Could the authors give an explanation on “electrochemically-driven mechanical recovery” in detail? How could the electrochemical reaction affect the mechanical properties of live pouch cells?
Author Response
Dear Reviewer,
Thank you for your comments about our manuscript, we found the advice very helpful for improving the manuscript. I have made the following changes to the text in response to your corrections:
1) I have improved the discussion of compression impulse of EPP foam with a clarification about the source of sinusoidal noise and its effect on the load-time graph.
2) Thank you for noticing this, the values were incorrect because of a mistake I made when generating graphs in OriginLabs. I have corrected the graphs and updated the comments to values of displacements and time intervals where I had referred to them in the text.
3) I have provided greater clarity about the role that swelling of the jellyroll may have on the mechanical recovery of the pouch cell, both in the introduction and in the conclusion.
Best regards,
Alon Ratner
Reviewer 2 Report
This is a really good article and definitely worth publishing. There are too many figures in the manuscript. The authors are encouraged to consolidate some figures in to one figure. This helps to shorten the length of the article. The quality of some figures are really low. Please improve the quality of figures for publication.
Author Response
Dear Reviewer,
Thank you for your feedback about the manuscript, you are right that there are too many figures in the text. I have combined the information contained in diagrams in the methodology so that there is now a single graph that explains the method development of the apparatus. I have also concatenated the graphs in the results section so that they appear as a single figure. I have also streamlined the placement of images so that the length of the manuscript has been reduced to 14 pages.
I noticed that I was incorrectly importing graphs into Microsoft Word as images rather than importing them as objects from OriginLabs. They are now dynamic objects so I hope that when I upload the word format of the manuscript they are still rendered correctly. This should come out well in the .pdf version of the document. Please let me know if there are any problems when opening the .docx version of the manuscript.
Best regards,
Alon Ratner
Reviewer 3 Report
In this manuscript, Ratner et al have investigated the dynamic mechanical properties of lithium-ion pouch cells through dynamic compression impulse testing and compared with Arpro 5130 EPP. The authors have refined their drop tower impact testing approach by adding diaphragm, specialized impact absorbers and a high speed camera to better control the variables and improve the data collection during experiment. The authors found that there are similarities in terms of dynamic mechanical behavior of the inert pouch cells and highly damped foam.
In general the authors have done a good job in augmenting the current drop tower approach and obtained valuable mechanical data for the Li batteries, which could have help the development of E-vehicles. However it would be beneficial to the readers if the authors could extend the discussion by discussing the real-world implications of their data rather than just having an exhaustive list of their findings. The author should also explain the meaning of the color shades that overlap curves in the figures - are they confidence level, SD, or?
Author Response
Dear Reviewer,
Thank you for your advice about the applicability of the findings. I have added a paragraph to explain the significance of our findings with respect to finite element simulation in the discussion of results for compression impulse of the inert pouch cells in section 3.2.
Please see the section 2.4 for a revised explanation of the shaded regions in the graphs representing one standard deviation from the mean.
Best regards,
Alon Ratner
