Development of a Comprehensive Model for the Coulombic Efficiency and Capacity Fade of LiFePO₄ Batteries under Different Aging Conditions

Round 1

Reviewer 1 Report

The author has made most of the suggested corrections, including modifications to the figures. Some minor text and language errors remain. I have no further objections to the acceptance of this manuscript, which optional corrections.

Author Response

Dear reviewer

Thank for your help. I would like to take this opportunity to thank you for the effort and expertise that you contribute to reviewing, without which it would be impossible to maintain the high standards of peer-reviewed journals.

Kind regards

TingJung Kuo

Reviewer 2 Report

The paper proposes a model to determine the LifePo4 cell SoC, based on an internal electro-chemical modeling, using the adapted Thévenin model and associating a neural network. The model has an error of the order of 1.55%. However, both in the abstract and in the text, the way in which this value is determined is not sufficiently detailed. Some points need to be clarified in the text. There are also some errors of form, listed below.

 

Point to be specified:

Row 18: specify in two words what are the different environments.

Row 74: specify the SoC and CE binding equation.

Row 107: clarify what is a "quasi"-NN?

Row 117: the article plan is missing.

Row 217: what is "fast" and "slow" RC network? They model what phenomena? What is the relationship with the sentence in row 294?

Row 235: a reference to justify it?

Row 415: where is demonstrated this value of 1.55%?

 

Form points:

Row 59: define the term SEI at its first occurance (move the row 85's definition).

Rows 73 and 306: equation number?

Row 80: is not there something missing in the sentence?

Row 115: first occurrence of BPNN in the text part: explicit here as well and delete the definition in row 332.

Row 126: define the term ANN.

Row 141: repeats previous sentences.

Row 178: in Table 2, 91.08 refers to 0.5C and 96.42 for 3C.

Rows 186-187: make unbreakable 30 and °C.

Row 197: a space before "Table 2" is missing.

Rows 215 (2 times), 217: a space is missing after the formula.

Row 289: space and not dot between 'equation' and '(13)'.

Rows 338 and 339 (2 times): a space is missing before the formula.

Row 379, define the term MAPE.

Row 395: second chapter 5.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Abstract:

 

The proposed model has a direct correlation… (not “straight”).

 

The phrase “The proposed model...” is used 3 times!

 

Introduction:

 

“potential”, not “potentials.”

 

Li-ion batteries are not environmentally friendly. Just consider the problems with recyclability.

 

“dissimilar working conditions” is an erroneous phrase. You mean “variable working conditions”

 

“Much research…” instead of “Many researches”

 

“Joule heating”, not “Joule heat”

 

It is not clear what you mean by battery “tabs”. This is not a common term.

 

p. 2 line 80. “…a practical…”

 

p. 2 line 85. “…a solid…”

 

Define BPNN.

 

“The performance of lithium batteries must…” (remove “requirements”).

 

p3. line 129. The reference is missing, it shows an Error! message. Please make sure to remove Endnote -or similar- fields before uploading your paper.

 

Section 2. and Section 2.1 The experimental set up and procedure description is unacceptably poor. There is no mention of the type, brand, specific characteristics of the cells. There are no details on the equipment or instrumentation used, nor software. Again, there are references missing (shows the message “Error! Reference source not found). 

 

This phrase is extremely obvious/strange “rapidly drop suggesting that the capacity is already insufficient” please replace it.

 

The authors reveal no experience in electrochemistry or batteries. It is completely inappropriate to point out “turning points” in voltage plots. The data is treated as if it was mathematical functions. “Flat voltage platform” is another term never heard in the field of electrochemistry, batteries, or energy storage. The authors will have to revise textbooks with the typical characteristics of voltage curves to better understand what they see here. What the authors call “voltage curves” is more “cell discharge curves”. Where are the charge cycles? The authors show only the discharge.

 

Figures 1 to 4 are grouped, yet each one displays its own caption. When figures are grouped, each has a letter, for example a), b), etc. Please see other papers. The fact that you have dome this shows no experience in publishing. What is more, each of the captions is extremely poor and concise. A caption should describe the figure in detail and give enough data to be understood. Here, the authors have made the captions as short as possible. 

 

p. 5 line 157. Another missing reference.

 

Section 2.3. You didn’t mention in the experimental procedures how did you performed many cycles. 

 

You say that the results are consistent with the hypothesis, but no hypothesis was promised in first place.

 

I think that, by definition, is impossible to have a SOH of more than 100%.

 

p 6. 164. “Reference not found.”

 

p 7. 184. “Reference not found.”

 

p 10. 261. “Reference not found.”

 

SO, it seems that, by equation 10, the experimental data is fitted by arbitrary constants. Then, table 4 and 1 shows the values of experimental and “predicted data”. But how is the “predicted data” produces, what do you mean by it? Is this the result of a physicochemical model or is it that you call “predicted data” to the lines produced by the arbitrary parameters in Eq. 13?

 

Table 1 appears AFTER Table 4.

 

Caption for Fig. 7 is very poor, too short, non-explicative.

 

p 13. 306. “Reference not found.”

 

I disagree on the validity of the model in Figure 8. It seems that the combination if the Butler-Volmer Eq. is not really important if the parameters just fit the discharge lines and are then adjusted by a neural network. In my opinion, it seems that the model just fits data. Moreover, the author has not succeed to explain clearly how the model (models?) are developed in a logical order. I wouldn’t describe it as comprehensive. 

 

Figure 9. It is not clear what does the sets correspond to in the data. Sets of what?                 

 

“a lot of research” is a colloquial phrase

 

The conclusions contain a number of well-known facts and only a summary of what was found, no actual conclusions with new or relevant knowledge. 

Author Response

Please see the attachment. The response to reviewer comments  
attached to the manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

General comment and recommendation

In this paper the author presents a comprehensive model for LiFePO4 batteries is proposed to evaluate the state of charge (SOC) of a LiFePO4 cathode material for a Li-rechargeable battery. Upon application of the proposed algorithm the SOC is calculated within an error of 1.55%. The argument is interesting. Though, some of the key terminology seems not be properly used in the paper, and so some revisions are required.

 

Specific comments

1.       The author refers LiFePO4 as anode (see introduction) but actually the potential vs. Li/Li+ of the material corresponds to a cathode. The author also claims in the Experimental section that the upper and lower potential considered were 3.65 and 2.0 vs. Li. This is inconsistent to an anode material.

2.       The author talks about Li electroplating in the introduction, but this is a no longer a problem if Li-Ion cell are considered. Please be more specific.

3.       Discussion on page 4. From the lines 133-142 it seems that the capacity fading is a term related to the voltage drop after a turning point. Actually the capacity fading rules out the capacity delivered by a battery before the voltage drop.

4.       Error in the determination of the parameter. How did the author make this quotation?

Author Response

Please see the attachment. The response to reviewer comments  
attached to the manuscript.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Some corrections have been made to the manuscript, but the style and writing is still very poor and confusing. Some phrases are either too obvious or not clear. 

 

There is a mistake repeating several times in the manuscript "discharg". It should be "discharge".

Line 164: "references [50-52]" not "... reference[50-52]" In what way are they consistent with your results?

Figure 6. The caption is too poor. It doesnt describe the figure. Which parameters? In what conditions? The caption for figures should describe the content in a standalone manner.

Line 293: "... of Tables 1, 2 and 3..." instead of "... of table1, 2 and 3..."

Figure 5the legend in the x-axis should say " °C ", not "Degree"

I am surprised that the number of neutrons in involved in the model. I don't know if this is a translation error or if you do mean the elemental particle. Neutrons are irrelevant to the chemical and redox reactions taking place in batteries. Do you mean neutral elements in a simulation network? The manuscript needs to read by a professional tranalator.

Again, in Figures 2, 3, 4, 6, and 9 there are descriptions in text a), b), c) in the actual figures, but there are incorporated in the caption. This is basic scientific/technical style. 

 

 

 

 

Reviewer 2 Report

The revised version has taken inconsideration all my previous comments and suggestion, by modifying the text accordingly