Thermal Characterisation of Automotive-Sized Lithium-Ion Pouch Cells Using Thermal Impedance Spectroscopy

Round 1

Reviewer 1 Report

This paper uses thermal impedance spectroscopy to study the thermal characteristics of lithium-ion batteries based on the internal heating of the batteries, compares the thermal characteristics of the batteries at different temperatures and SOC, and compares the same experiment with another battery of the same size. The following issues should be improved:

1.       The topic of this study is within the scope of the journal. However, an introduction section does not provide reasons for selecting this topic.

2.       Abstract could be made less general and more specific to this study. Novel findings may be included in an abstract.

3.       Description of the experiment in 2.1. If equation 1 is used to calculate the heat generation power of the battery, how to control the heat generation of the battery is shown in Figure 1a?

4.       How to determine the battery temperature? In Figure 1b, how is the battery temperature determined? The temperature distribution of the battery is generally uneven, will it affect the experimental results?

Author Response

We want to thank the reviewer for the relevant comments. They helped specify the paper's scope and improve the overall script.

This paper uses thermal impedance spectroscopy to study the thermal characteristics of lithium-ion batteries based on the internal heating of the batteries, compares the thermal characteristics of the batteries at different temperatures and SOC, and compares the same experiment with another battery of the same size. The following issues should be improved:

1. The topic of this study is within the scope of the journal. However, an introduction section does not provide reasons for selecting this topic.

The introduction is adjusted to show the benefit of the approach presented, especially in the automotive context. The findings are relevant to speed up the thermal characterisation of state-of-art automotive-sized cells and to examine differences in the thermal behaviour relying on the layer structure (High-Power and High-Energy).

2. Abstract could be made less general and more specific to this study. Novel findings may be included in an abstract.

Further relevant results are supplemented in the abstract. They cover all parts of the paper. Also, the key outcomes of the paper are included in the abstract.

3. Description of the experiment in 2.1. If equation 1 is used to calculate the heat generation power of the battery, how to control the heat generation of the battery is shown in Figure 1a?

We added the relevant equation (Equation 2) used for the heating of the cell (excluding the reversible heat part). Also, a figure to illustrate the modulated current signal is added (Figure 1) and described.

4. How to determine the battery temperature? In Figure 1b, how is the battery temperature determined? The temperature distribution of the battery is generally uneven, will it affect the experimental results?

An improved description is added in the explanation of Figure 2b: "measured thermal response on the centre of the cell's surface caused by the corresponding heating in a)." Also, it is mentioned that the results rely on the mean value of both central temperature sensors. 

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors of the paper entitled “Thermal Characterisation of Automotive-Sized Lithium-Ion Pouch Cells Using Thermal Impedance Spectroscopy” the impedance spectroscopy is used to investigate LIB.

1.       No conclusion;

2.       No experimental setup description or real setup pictures;

3.       Without references to the equipment involved in measurements;

4.       More references can be added, and the introduction needs to be more elaborate, adding information about the new scientific contribution and the new elements brought by it;

5.        … cally distributed frequencies from 3 mHz to 160 μHz. Also, the number of repetitions per 67

I recommend to use the same convection from low frequency to high frequency if the direction of scan is not specified.

Author Response

We want to thank the reviewer for the relevant comments. They helped specify the paper's scope and improve the overall script.

The authors of the paper entitled “Thermal Characterisation of Automotive-Sized Lithium-Ion Pouch Cells Using Thermal Impedance Spectroscopy” the impedance spectroscopy is used to investigate LIB.

1. 1.       No conclusion;

Now the Conclusion part is separated from the rest of the Discussion. It was included in the Discussion section before.

2. 2.       No experimental setup description or real setup pictures;

The test setup is shown in figure 4 and described in section 2.2. A photo of the test setup is not included due to a better visualisation using the schematic representation.

3. 3.       Without references to the equipment involved in measurements;

The utilised testing equipment is described in line 153 ff.: "The tests were conducted using a BasyTec MRS cell cycler and a Memmert ICP110 climate chamber to obtain a constant ambient condition at particular temperatures."

4. More references can be added, and the introduction needs to be more elaborate, adding information about the new scientific contribution and the new elements brought by it;

More adequate references are added, and the new elements used in the approach are shown in more detail in the introduction.

5. … cally distributed frequencies from 3 mHz to 160 μHz. Also, the number of repetitions per 67

I recommend to use the same convection from low frequency to high frequency if the direction of scan is not specified.

A clarification is added. It states that the highest frequency is tested first and therefore mentioned first.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors of the paper entitled” Thermal Characterisation of Automotive-Sized Lithium-Ion Pouch Cells Using Thermal Impedance Spectroscopy” they made a real progress in the revised form of the manuscript. The requirements were met and more they brought enough details relative to the experimental area. The final discussion brings a plus of clarity. Some phrases have remained clumsy or uninspired, in my opinion, but checking the manuscript in the editing process can eliminate these situations.