Insight into the Desolvation of Organic Electrolyte Cations with Propylene Carbonate as a Solvent in Flat Pores: A First-Principles Calculation
Round 1
Reviewer 1 Report
The paper aims to report the First-Principles Calculation of the desolvation of organic electrolyte cation with propylene carbonate. The authors took a chance and wrote an impressive manuscript. However, before it can be considered for publication, it must undergo further revision according to the following comments.
- A general discussion discussing the advantages and limitations of the prepared materials and the used organic electrolytes is missing. In addition, the morphology of these surfaces is changed depending on the used electrolytes. This kind of discussion is very important to make this study attractive to the reader and to avoid this work becoming a listing of examples.
- In conclusion, include a section on current research obstacles/challenges and potential future directions of these electrolytes for other applications.
- Minor editing of English language required
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments on Desolvatization of Cationic Organic Electrolytes from Graphene bilayer Pores
The authors construct a structural model composed of a graphene bilayer (GB) with separation d between layers. Two ways of stacking are defined, AA and AB. The GB is in contact with a medium of organic cations (“A”) in propylene carbonate (PC). The energy profiles for three reactions are traced:
R1: A(PC) + BG ® A(BG) + PC; PC is expelled and A enters a graphene bilayer pore.
R2: A(PC) + BG ® A + PC(BG); BG captures PC, producing free A.
R3: A(PC) + BG ® [A,PC] (BG); A (PC) adds to BG.
The organic cation may be the organic species TEA+ (tetraethyl ammonium) TEMA+ (TriethylMethyl ammonium), or bipyrrolidinium ammonium (SBP+). Li+ provides a reference point.
The energies are computed by a tight-binding simplification of Density Functional Theory with a PBE:GGA representation of energy. No evaluation of the reliability of this method is provided., or whether it has proved useful in analogous systems. The distance between layers is varied, affecting the pore (hole) size d. This quantity is varied to produce the profiles described below. It does not appear that the system structure is optimized at each value of d (relaxed scan) which may be significant, especially at small values of distance.
Graphs of reaction energy vs. a measure of the size of the pore in the graphene bilayer GB show that Reaction R2 will never favor production of free cation. The quantity reported seems to be internal energy with no entropic correction rather than the more relevant Gibbs energy. But use of Gibbs energy is unlikely to change this conclusion.
Reactions R1 and R3 are energetically favored for all values investigated, and for each A the graphs define a crossover point at specific values of bilayer distance. Below this critical pore size d*(A), R1 is favored and the GB is desolvated.
For TEA+, d* is 5.5 (Angstroms) while for TEMA+ the value is 4.9; the ionic radii are 3.43 and 3.27 respectively. It appears there is a dramatic dependence between spontaneous desolvation and size of pore. Perhaps this relation is not simple. For SBP+ the ionic radius is quite small, 2.09 and d* is only slightly reduced, 4.8 Angstroms. For Li+, which to me seems to be quite different from the organic cations, the values are 0.69 and 5.9 Angstroms. The binding at d* is similar for the organic cations (about 6 eV) but much smaller for Li+. Does this make a difference?
This work is well-conceived and the results are of interest. It provides a coherent semi-quantitative explanation for important phenomena. However I recommend revision to address the points made.
Minor points:
Often a pseudopotential is used for the atomic core. Why was LIB 2019 chosen? A reference should be made to its definition and performance.
What are “Flexible holes”?
The “intelligent algorithm” (Line 84) needs definition and reference.
English expression is clear and unambiguous - a scan by Grammarly or the like can catch minor errors.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript "Insight into the Desolvation of Organic Electrolyte Cation with Propylene Carbonate as a Solvent in Flat Pores: A First-Principles Calculation" calculates the reaction energies of ions, propylene carbonate and ionic complexes in bilayer graphene with different layer distances, as well as the desolvation behavior of lithium salt cations (Li+), of tetraethyl quaternary ammonium salt cations (TEA+), of triethyl methyl quaternary ammonium salt cations (TEMA+) and bipyrrolidinium quaternary ammonium salt cations (SBP+).
The author has considered the not really relevant and updated literature evidence in this scientific area and present their results and analysis in unclear and meaningful way. A few comments for the author are given below:
A few comments for the author are given below:
1. Abstract
The background is too short. In the methods and results of the abstract, please mention the results that has mentioned in the methods. More information about the highly significant observations should be clarified in the results. The authors should provide conclusion with focusing on the innovations related to be in a harmony with the title of the manuscript and the objectives of your study.
2. Introduction
The literature must be enriched with more recent data.
- The authors should focus on the objectives of their study. Introduce why they chose to study this topic is important with recent references.
- In the last paragraph, please add a couple of sentences to highlight the “innovative” aspect of the paper (added value in this field?) …what has been examined for very first time/or in more depth in this research area by your work presented in this manuscript?
3. Results
- The authors has not explained in detail about the findings.
4. Method
- The authors did not explain in detail about the methods in the manuscript
5. Discussion
-I think the authors should discuss the innovations and more clarifying why they study in this section in more details.
-The authors needs to update the reference sources used. Make sure it is up to date.
6. Conclusion: More details about their observations by showing some of this valuable study significations point by point should be more clarified.
7. References
A number or references need some formatting changes. Please ensure that the authors follow MDPI guidelines for presenting name of authors/abbreviation of journals/year of publication in bold/volume journals in italics etc.
Comments for author File: 
Comments.docx
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The respondent has addressed all my suggestions and questions with care. This work is ready for publication.
