Preparation of Li₃PS₄–Li₃PO₄ Solid Electrolytes by Liquid-Phase Shaking for All-Solid-State Batteries

Round 1

Reviewer 1 Report

This a decent publication in an interesting area but it has very little relevance to this journal. Li3PS4 is a solid electrolyte and its research would therefore be more appropriate for "Energies" or "Materials". Why was "Electronic Materials" chosen? I recommend publication but not in this journal since its scope does not include energy storage. Also, the self-citations are excessive (~33% of the total citations). There are many other papers on this material and solid-state batteries in general that could be cited. 

Author Response

Thank you for your comment. In fact, this manuscript was invited from the editor and it was preliminary evaluated by the editor prior to submission. More papers were added to the reference list to reduce the self – citation rate. 

Reviewer 2 Report

This study reports that the preparation of Li3PS4-Li3pPO4 solid electrolytes by liquid-phase shaking for all solid state batteries. After carefully evaluating the manuscript, the manuscript would be accepted for publication when the following comments were addressed accordingly.

1. The x value presented in Abstract is 6 or 0.6 ? Please confirm and make the consistency throughout the context.
2. The purpose and functions of the ethyl propionate used in this study were not clearly discussed.
3. The authors mentioned that "100Li3PS4–xLi3PO4 solid electrolytes were prepared from raw materials by the liqid-phase shaking method that has previously been reported." Here should provide the reference information.
4. The authors claimed that the solid-solution of as-synthesized compound was formed up to x >= 10. More solidly evidences e.g., XRD refinement should be provided to support this result.
5. The authors concluded that the incorporation of Li3PO4 into Li3PS4 could improve not only the ionic conductivity, activation energy and stability against metallic Li but also the charge–discharge capacities of the all-solid-state cell employing the 100Li3PS4–6Li3PO4 solid electrolyte at the positive electrode. Nevertheles, the cycling stability presented in Figure 5 (c) was not as good as mentioned above. 

Author Response

This study reports that the preparation of Li₃PS₄-Li₃PO₄ solid electrolytes by liquid-phase shaking for all solid state batteries. After carefully evaluating the manuscript, the manuscript would be accepted for publication when the following comments were addressed accordingly.

1. The x value presented in Abstract is 6 or 0.6? Please confirm and make the consistency throughout the context.

Ans: Thank you for your comments. The x value was corrected to 6.

1. The purpose and functions of the ethyl propionate used in this study were not clearly discussed.

Ans: “ethyl propionate was employed in this study since it was suitable for Li­₃PS₄ and Li₃PS₄ – LiI preparation.” was added to the introduction part.

“The UV-Vis spectra proved that P₂S₅ dissolution in EP was the initial step for the reaction with Li₃PO₄ in EP solvent. To the best of our knowledge, this is the first time that such a reaction has been reported and evidenced using simple UV-Vis spectroscopy.” was written in the discussion part of Fig.1.

1. The authors mentioned that "100Li₃PS₄–xLi₃PO₄ solid electrolytes were prepared from raw materials by the liqid-phase shaking method that has previously been reported." Here should provide the reference information.

Ans: the reference was provided and the sentence was corrected to “100Li₃PS₄–xLi₃PO₄ 100Li₃PS₄∙xLi₃PO₄ solid electrolytes in this study were prepared from raw materials by using the liquid-phase shaking method that has previously been reported [19].”

1. The authors claimed that the solid-solution of as-synthesized compound was formed up to x >= 10. More solidly evidences e.g., XRD refinement should be provided to support this result.

Ans: Sorry for over claiming the result. It was corrected to x = 6 in the main text.

1. The authors concluded that the incorporation of Li₃PO₄ into Li₃PS₄ could improve not only the ionic conductivity, activation energy and stability against metallic Li but also the charge–discharge capacities of the all-solid-state cell employing the 100Li₃PS₄–6Li₃PO₄ solid electrolyte at the positive electrode. Nevertheless, the cycling stability presented in Figure 5 (c) was not as good as mentioned above. 

Ans: Thank you for your concern. The sentences were change to “It was observed that the incorporation of Li₃PO₄ into Li₃PS₄ could improve not only the ionic conductivity, and activation energy and but also stability against metallic Li. but also The charge–discharge capacities of the all-solid-state cell employing the 100Li₃PS₄∙6Li₃PO₄ solid electrolyte at the positive electrode was slightly higher than those of the cell using Li₃PS₄ in the positive electrode.”

Reviewer 3 Report

Thank you for submitting this manuscript to the journal. 

Two issues must be addressed: 

In the abstract, a sample with x=0.6 is discussed, (line 17) but no such material shows up in the discussion.  I believe this was an error and is supposed to refer to the material with x=6.

Likewise, in the abstract the statement that from the PXRD data one can conclude that solid solutions can be formed up to x=10 (line 12), but the series of PXRD data has an x=6 and an x=20.  Therefore it can be stated that solid solutions can be formed at up to 6, but whether that limit is 10 cannot be stated with any certainty (based on the information in the paper...)  Therefore, either the authors need to expand in the discussion as to why x=10 is the correct value, or change the conclusion reported in the abstract.

 

Additionally, small changes can be made to improve the manuscript overall.  Specifically:

The way that the "100Li₃PS₄-xLi₃PO₄" (Line 61) is typeset in the submission is nearly indistinguishable from "100Li₃PS_4-xLi₃PO₄" which caused me to become confused for a while.  It may be useful to write it as "100Li₃PS₄∙xLi₃PO₄"   in a manner similar to how you write "75Li₂S∙25P₂S₅" on line 40. (i.e., make it evident to the reader that in no way is "4-x" intended to be read as a group.

Incidentally (best to verify anyway) I would like to confirm that the authors do mean "100Li₃PS₄∙xLi₃PO₄" and not "(100-x)Li₃PS₄∙xLi₃PO₄"

In the experimental section, the expression "screw bin" also caused me to become confused for a bit until I saw the top half of Figure 1.  I believe that the term "screw vial" or "screw top vial" may make it easier for readers to understand the glassware used.

Similarly, even though the definition for EP is given in the introduction, it would make it easier to give it (or give it again) in the experimental section. 

Also, it may be that the solvent used is "Super Dehydrated Ethylene Propionate" instead of "Dehydrate" and usually the term is "agate mortar and pestle".

For completeness in the exerimental section, it would be useful to give the source of the SUS rods (Misumi?) and define the NMC as the material described in line 75.

In Figure 2 a) and b) both, the abbreviation LPO is used.  It would be best if that was defined somewhere in the text, possibly the discussion of the XRD.

Figure 4 shows values for conductivity and apparent activation energies.  In case the authors have taken the trouble to replicate the work, it would be excellent if error bars on those derived values were given to help assess how strongly to use the results as design parameters for future work...  If you didn't replicate the work, then let your students know it is essential to do so.

 

 

 

Author Response

Two issues must be addressed: 

In the abstract, a sample with x=0.6 is discussed, (line 17) but no such material shows up in the discussion.  I believe this was an error and is supposed to refer to the material with x=6.

Ans: Thank you for your comments. The x value was corrected to 6.

Likewise, in the abstract the statement that from the PXRD data one can conclude that solid solutions can be formed up to x=10 (line 12), but the series of PXRD data has an x=6 and an x=20.  Therefore it can be stated that solid solutions can be formed at up to 6, but whether that limit is 10 cannot be stated with any certainty (based on the information in the paper...). Therefore, either the authors need to expand in the discussion as to why x=10 is the correct value, or change the conclusion reported in the abstract.

Ans: Sorry for over claiming the result. It was corrected to x = 6 in the main text.

Additionally, small changes can be made to improve the manuscript overall.  Specifically:

The way that the "100Li₃PS₄-xLi₃PO₄" (Line 61) is typeset in the submission is nearly indistinguishable from "100Li₃PS_4-xLi₃PO₄" which caused me to become confused for a while.  It may be useful to write it as "100Li₃PS₄∙xLi₃PO₄"   in a manner similar to how you write "75Li₂S∙25P₂S₅" on line 40. (i.e., make it evident to the reader that in no way is "4-x" intended to be read as a group. Incidentally (best to verify anyway) I would like to confirm that the authors do mean "100Li₃PS₄∙xLi₃PO₄" and not "(100-x)Li₃PS₄∙xLi₃PO₄".

Ans: Thank you for your concern. All the formula was changed to "100Li₃PS₄∙xLi₃PO₄" and "100Li₃PS₄∙6Li₃PO₄" in the main text.  

In the experimental section, the expression "screw bin" also caused me to become confused for a bit until I saw the top half of Figure 1.  I believe that the term "screw vial" or "screw top vial" may make it easier for readers to understand the glassware used.

Ans: “screw bin” was changed to “screw vial” as recommended.

Similarly, even though the definition for EP is given in the introduction, it would make it easier to give it (or give it again) in the experimental section. Also, it may be that the solvent used is "Super Dehydrated Ethylene Propionate" instead of "Dehydrate" and usually the term is "agate mortar and pestle".

Ans: "Super dehydrated Ethylene Propionate (EP)" was used instead of "Super dehydrate EP". “Agate mortar and pestle” was inserted into the experimental part.   

For completeness in the exerimental section, it would be useful to give the source of the SUS rods (Misumi?) and define the NMC as the material described in line 75.

Ans: the source of SUS rods was provided in the experimental part and definition of NMC was also added.

In Figure 2 a) and b) both, the abbreviation LPO is used.  It would be best if that was defined somewhere in the text, possibly the discussion of the XRD.

Ans: the abbreviation was provided in the discussion part of Fig.2.

Figure 4 shows values for conductivity and apparent activation energies.  In case the authors have taken the trouble to replicate the work, it would be excellent if error bars on those derived values were given to help assess how strongly to use the results as design parameters for future work...  If you didn't replicate the work, then let your students know it is essential to do so.

Ans: Thank you for your comments. Due to time limit of this time, I would like to leave those experiments for the future works.  

Reviewer 4 Report

This paper describes a procedure for the preparation of a solid electrolyte of  Li3PS4 doped with certain amount of with Li3PO4, and prepared through liquid-phase synthesis. The manuscript seems to me well organised and clearly explained. The results are interesting and the procedure seems to be correct. I am not been able to evaluate the materials characterisation plots (figure 2 and 3) due to the lack of experience. Otherwise, I think the manuscript is suitable to publication with minor changes. 

1) Line 58. Clarify LiX

2) Lines 80-92. Add hard short space between values and units in quantities. 

3) Please, define RT first time it is mentioned. (Room Temperature, I suppose?)

4) The optical image of the materials before and after sanitation in line 136 is not numbered. I also consider this image unattractive. 

5) Figure 4 caption. Please place the (a) and (b) before the description of the (a) and (b) sub-figures. 

Author Response

This paper describes a procedure for the preparation of a solid electrolyte of Li₃PS₄ doped with certain amount of with Li₃PO₄, and prepared through liquid-phase synthesis. The manuscript seems to me well organised and clearly explained. The results are interesting and the procedure seems to be correct. I am not been able to evaluate the materials characterisation plots (figure 2 and 3) due to the lack of experience. Otherwise, I think the manuscript is suitable to publication with minor changes. 

• Line 58. Clarify LiX

Ans:”(X = Cl, Br and I) “ was added to the main text next to LiX.

• Lines 80-92. Add hard short space between values and units in quantities.

Ans: space was added between values and units as recommended.  

• Please, define RT first time it is mentioned. (Room Temperature, I suppose?)

Ans: definition of RT was provided in the introduction part.

• The optical image of the materials before and after sanitation in line 136 is not numbered. I also consider this image unattractive. 

Ans: The optical image was mentioned in the text and new set of photograph was added to Fig.1.

• Figure 4 caption. Please place the (a) and (b) before the description of the (a) and (b) sub-figures. 

Ans: the caption was corrected as mentioned.

Round 2

Reviewer 1 Report

My comments have been addressed.

Reviewer 2 Report

The comments were revised according. It would be accepted for publication.