Synthesis of Ag-La_0.8Sr_0.2MnO₃ (LSM-Ag) Composite Powder and Its Application in Magnesium Air Battery

Round 1

Reviewer 1 Report

The study on the synthesis of Ag-LSMO3 composite powder and its applications in Magnesium air battery presented in this manuscript is interesting and can be useful for the scientific community. However, there is a lot of room for improvement. My opinion, suggestions and questions are as following- 

1. Is this the first time such a study has been performed using these composite materials? Authors should ask this question to themselves and clearly write about previous efforts and their results in the Introduction and use those results to compare theirs in the discussion. This would be helpful in highlighting the novelty in the work which I could not found.
2.  The abstract needs a revision. Silver nanoparticles reduction by PVP is understandable but there is nothing about LSMO3 synthesis. So, the Authors can remove the entire synthesis and write a general statement or should rephrase and include the important information. 
3. There is two contradictory statements in the abstract about Ag particles distribution in the composite. Either they are uniformly distributed throughout the mass or are they present only on the surface?
4. Crystal structure distortion would happen when Ag atoms would go into the crystals of the LSM which doesn't appear so the statement using SEM about the crystal structure is not right.
5. When you say 63 mW/cm2 power density for LSM battery you are talking about your results or it is the maximum reported using this material? If it is your results then please write about the maximum power density using this material and explain.
6. The introduction needs proper citations. Please also improve it in light of my comment no.1.
7. I assume for the synthesis of Ag nanoparticles, the surfactant is used to control the particle sizes. Please write if it is for another reason. However, there are no separate SEM images of Ag nanoparticles to support the claims so it is difficult to understand the reaction's purpose where Ag particles can easily be formed using just a reducing agent.
8. XRD shows a mixture of both LSM and Ag particles. There is no citation to claim that you do not have AgO. Why would you expect crystal structure distortion when you have prepared both the particles separately? It is unlikely for any metal particles not to have oxides on the surface unless it is well passivated by some ligands and in your case PVP.  So the statements from 'This means...' to the end of the paragraph don't make any sense. Please use XRD results to show that you have a mixture of both particles. Maybe a comparison with different Ag loading would be interesting or crystallite size approximation using Williamson-Hall equation.
9. SEM analysis is completely useless. I do not see any changes in the SEM images with and without Ag. Particle sizes are of the submicron range that you could write. 14 % weight Ag particles is not so small that you would not see unless you have a uniformly distributed sample. So maybe your sample is nicely uniform so use this statement to say something about the SEM images than the current explanation. SEM and crystal structure have no relation. Please do not use SEM to explain crystal structure. Zoomed in Fig. 3 doesn't make any sense unless accompanied with EDX ( point) to confirm the presence of Ag and LSM with it.
10. The quality of Fig. 5-7 is very poor. Please improve the quality of the figures. I can't read the legends of the figure. Please make them bigger.
11. Finally, Discussion doesn't provide much information about the results you got. How the quantitative results are and how about when you compare them with the previous studies? There is no qualitative assessment with the structural studies either.

Author Response

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Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript entitled “Synthesis of Ag-La0.8Sr0.2MnO3 (LSM-Ag) Composite Powder and Its Application in Magnesium Air Battery“ reports results concerning the synthesis of LSM-Ag composite powders, their characterization by XRD, SEM-EDX, electrochemical performance and tests for Mg-air battery. The discussions are well structured and experimental results prove conclusions of this work. However, in my opinion to improve this manuscript it is necessary:

1)  Title for section “2.2. Characterization of LSM-Ag composite powder” should be modified because is the same like for section 2.3. The word "Characterization" in section 2.2. should be changed for "Preparation" or other.

2) In section 2.4. is not noted the reference electrode and counter electrode.

3) In section 2.4 should be add description of cyclic voltammetry measurements.

4) In section 2.5. is not noted the mass ratio of catalyst, the carbon black and polytetrafluoroethylene.

5) In section 2.5. is not noted the number of measured charge/discharge cycles and their discussion in section 4.

6) Page 6: lines 162-169 should be described in section 2.4.

7) Description for Figure 1 should be before figure not after figure.

8) In section 3.2 should be add description for cyclic voltammetry curves and their figure.

9) Description for Figure 6 should be before figure not after figure.

10) Page 9, line 191: the concentration for KOH is different than in section 2.4.; should be 5 mV/s not 5mV/s.

11) On Figure 7a should be add description of particular parts of battery.

12) In section “4. Discussion”  the obtained materials should be compared to other composite materials containing the perovskite. What is the advantages of materials in this study compare to other composite materials?

I recommend this article to be published in Metals after major revision.

Author Response

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Round 2

Reviewer 1 Report

The authors have incorporated suggested changes and answered my questions satisfactorily. I would like to suggest the following changes that may help to improve the manuscript-

1. In the abstract, "in the form of a simple substance" can be replaced by "elemental form".
2. In the introduction, when you say many studies, readers expect to see multiple citations but I see only one so please add more relevant citations.
3. Statements made in the discussion need to be supported by relevant references.

Author Response

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Reviewer 2 Report

I accept revised version and I in my opinion paper can be published in current version. 

Author Response

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