Innovation of Electrolyte and Electrode Materials and Interface Construction Strategies in Sodium-Ion Batteries

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is very weak as a review paper. Numerous comprehensive review articles and ongoing studies on Na-ion batteries have already been published, whereas this manuscript does not provide sufficient data, critical analysis, or comprehensive discussion. The content lacks the depth and novelty expected for a review article in this field. Therefore, it cannot be considered acceptable as a review paper on Na-ion batteries.

Author Response

Thank you for your candid and thorough evaluation, which we deeply respect and fully accept. We sincerely acknowledge that the current manuscript falls significantly short of the standards expected for a review article on Na-ion batteries, as it lacks the comprehensive data synthesis, critical comparative analysis, and in-depth discussion necessary to contribute meaningfully to a field where numerous high-quality reviews already exist.We truly appreciate the time and intellectual honesty you have invested in this assessment, and we hope to have the opportunity to resubmit a significantly improved version for your further consideration.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript well reviewed the recent reports of the electrodes and electrolytes as well as their interface structure for sodium-ion batteries. However, the manuscript contained some insufficient explanation and small mistakes on writing. As well as, the citation of the references is not enough. After minor revision of the following comments, the manuscript can be accepted on “coatings”.

 

1. Pages 1-11, Introduction Section, Innovation in electrolyte systems section, and Innovative design of electrode materials section, the authors can insert sub-sections, as in Sections 4 and 5.

 

2. Pages 1-3, Introduction Section, please cite the references.

 

3. Pages 1-3, Introduction Section, the authors can add a table summarizing the performance and advantages of the sodium-ion batteries.

 

4. Pages 3-7, Innovation in electrolyte systems section, the authors can add a table summarizing the properties of the electrolytes, and the schematic or chemical structures of the electrolytes.

 

5. Pages 9-10, Innovative design of electrode materials section, the main text of page 10, and Figure caption of Figure 3-5, why is the color of the text light blue?

 

6. Pages 7-11, Innovative design of electrode materials section, the authors can add the schematic models of the insertion/extraction process of Na ion, or the sodium-ion storage mechanism.

In addition, the authors can add a table summarizing the properties and performance of the electrodes.

For the SEI formation at the anode, how thick does the SEI layer have?

 

7. Pages 11-15, Construction and regulation strategies of electrode/electrolyte interface section, the authors can add the schematic models of SEI, CEI, or electrode/electrolyte interface structures.

In addition, page 14, Table 1, please cite the references.

 

8. Pages 15-16, Results and Discussion section, Section 5.1, and Table 2, please cite the references.

 

 

9. Pages 15-19, Results and Discussion section, it is not clear the discussion part of the authors' results and the discussion of the results reported in previous papers. It would be better to clearly distinguish between those discussions.

 

10. Pages 19-20, Summary and Outlook section, the authors can add the schematic model of the electrode or the electrolyte/electrode interface relating the future aspect of the sodium-ion batteries.

In addition, please cite the references, if possible.

 

Comments on the Quality of English Language

There are some small mistakes mentioned following. Please check and revise it.

 

1. Page 1, author name and affiliation, “~ Kai Wang ^{2 and *}” should be “~ Kai Wang ^{2, *}”.
2. Page 3, line 110, “~ positive and negative electrode materials; ~” should be “~ cathode and anode materials; ~”. Page 3, line 120, “~ between the positive and negative electrodes, ~” should be “~ between the cathode and anode, ~”.
3. Page 17, line 712, “~ (such as those with a voltage >4.2 V) ~” should be “~ (such as those with a voltage > 4.2 V) ~”.

Author Response

Dear Reviewer, Thank you for your attention to our research and for your valuable suggestions. We have carefully read your comments and revised our manuscript accordingly. Our specific responses are provided below, with the response and revisions distinguished by different font colors.

The manuscript well reviewed the recent reports of the electrodes and electrolytes as well as their interface structure for sodium-ion batteries. However, the manuscript contained some insufficient explanation and small mistakes on writing. As well as, the citation of the references is not enough. After minor revision of the following comments, the manuscript can be accepted on “coatings”.

1. Pages 1-11, Introduction Section, Innovation in electrolyte systems section, and Innovative design of electrode materials section, the authors can insert sub-sections, as in Sections 4 and 5.

Response: Dear reviewer, thank you for pointing this out. We agree with this comment. Therefore, we have added sub-sections to the Innovation in electrolyte systems, and Innovative design of electrode materials sections (consistent with the structure of Sections 4 and 5) in the revised manuscript.

 

2. Pages 1-3, Introduction Section, please cite the references.

Response: Dear reviewer, thank you for your suggestions. We agree with this comment. Therefore, we have added the corresponding references to the Introduction section (Pages 1–3) in the revised manuscript.

 

3. Pages 1-3, Introduction Section, the authors can add a table summarizing the performance and advantages of the sodium-ion batteries.

Response: Dear reviewer, thank you for your suggestions. We agree with this comment. Therefore, we have added a comparative table summarizing the key performance metrics and core advantages of sodium-ion batteries in the Introduction section of the revised manuscript.

 

Table 1. Summary of key performance characteristics and advantages of sodium-ion batteries (SIBs)

Aspect	Sodium-ion Batteries (SIBs)		Remarks
Raw material abundance	Na: ~2.64% in Earth's crust, evenly distributed		SIBs have lower supply risk and geopolitical constraints
Raw material cost	Low (using Na, Fe, Mn, etc.)		SIBs are more suitable for cost-sensitive large-scale storage
Current collector	Al foil for both anode and cathode		Al anode current collector reduces cost and weight
Theoretical energy density	Lower		Exact values depend on materials; SIBs typically 150-200 Wh/kg at cell level
Typical operating voltage	2.5–3.7 V (depending on cathode)		SIBs generally lower voltage due to Na potential
Safety	Better (less prone to thermal runaway, milder chemical reactivity)		SIBs show improved safety in nail penetration and overcharge tests
Low-temperature performance	Good (can retain >80% capacity at -20°C with optimized electrolytes)		SIBs are promising for cold regions
Cycle life	Moderate (2000–5000 cycles for lab scale; improving)		SIBs still need improvement for grid storage (target >10,000 cycles)
Environmental friendliness	High (non-toxic, easily recyclable)		SIBs are more sustainable

 

 

 

 

 

 

 

 

4. Pages 3-7, Innovation in electrolyte systems section, the authors can add a table summarizing the properties of the electrolytes, and the schematic or chemical structures of the electrolytes.

Response: Dear reviewer, thank you for your suggestions. We agree with this comment. Therefore, we have added a dedicated summary table of electrolyte properties in the Innovation in electrolyte systems section of the revised manuscript.

Table 2: Comprehensive Comparison of Electrolyte Systems for Sodium-Ion Batteries

Electrolyte Type	Representative System	Ionic Conductivity (mS cm⁻¹, RT)	Electrochemical Window (V vs. Na⁺/Na)	Operating Temperature (°C)
Liquid Organic
Conventional Carbonate	EC/DMC + NaPF₆	5–12	0–4.3	–20 to 60
Locally High-Concentration (LHCE)	NaPF₆/EC-DMC + HFE diluent	2–8	0–4.8	–30 to 80
Ether-based	DME/MeTHF + NaBF₄	8–15	0–4.0	–40 to 40
Solid-State
Polymer	PEO-based	0.001–0.1	0–4.0	60–80
Oxide (NASICON)	Na₃Zr₂Si₂PO₁₂ (NZSP)	0.1–1.0	0–5.0	RT–200
Sulfide	Na₃PS₄, Na₃SbS₄	0.1–12.66	0–4.2	RT–80
Halide	Na₃YCl₆, LaCl₃-based	0.5–1.38	0–4.5	RT–150
Composite Polymer	PEO-LLTO-TiO₂	0.1–0.2 (55°C)	0–4.5	55–80
Aqueous	Water-in-Salt (17 mol kg⁻¹ NaClO₄)	10–30	1.5–2.5	–10 to 60

 

5. Pages 9-10, Innovative design of electrode materials section, the main text of page 10, and Figure caption of Figure 3-5, why is the color of the text light blue?

Response: Thank you for pointing this out. We sincerely apologize for this formatting error. This light blue text was an unintended formatting leftover from the manuscript editing process and does not reflect the final formatting we intended for the manuscript. Therefore, we have corrected this issue in the revised manuscript

 

6. Pages 7-11, Innovative design of electrode materials section, the authors can add the schematic models of the insertion/extraction process of Na ion, or the sodium-ion storage mechanism.

Response: Thank you for this constructive suggestion. We agree that incorporating schematic models of the Na⁺ insertion/extraction process and the sodiumion storage mechanism will significantly improve the readability and scientific clarity of Section 3. Therefore, we have added new content in the revised manuscript

The electrochemical energy storage in sodium-ion batteries is realized through reversible sodiation/desodiation reactions at both cathode and anode materials. Based on the nature of the electrode reactions, the sodium-ion storage mechanisms can be systematically classified into four categories: intercalation/insertion, alloying, conversion, and adsorption-filling mechanisms. Each mechanism exhibits distinct electrochemical characteristics, capacity potential, and structural stability profiles, which fundamentally determine the selection and design strategies of electrode materials.

 

7. Pages 11-15, Construction and regulation strategies of electrode/electrolyte interface section, the authors can add the schematic models of SEI, CEI, or electrode/electrolyte interface structures.

Response: Thank you for pointing this out. We agree with this comment. Therefore, we have added the schematic models of SEI, CEI, or electrode/electrolyte interface structures.

Fig.6 presents schematic models illustrating the structural characteristics of these interfacial layers.

 

Fig.6 Schematic of SEI Interfacial Structure

 

8. Pages 15-16, Results and Discussion section, Section 5.1, and Table 2, please cite the references.

Response: Thank you for pointing this out. We agree with this comment. Therefore, we have added the corresponding references in the specified locations in the revised manuscript.

 

9. Pages 15-19, Results and Discussion section, it is not clear the discussion part of the authors' results and the discussion of the results reported in previous papers. It would be better to clearly distinguish between those discussions.

Response: Thank you for pointing this out. We agree with this comment. Therefore, we have revised the Results and Discussion section (Pages 15-19) to clearly distinguish between the discussion of our own results and the comparison with previous literature.

It should be noted that this section presents a comprehensive analysis and discussion of representative research results reported in the literature, rather than experimental data obtained by the authors. The comparative evaluation of different electrolyte systems, electrode materials, and interface engineering strategies is based on published studies, with specific references cited for each data point and conclusion. The authors' own contribution lies in the systematic categorization, quantitative comparison, and scenario-oriented technical route analysis of these existing research achievements.

 

10. Pages 19-20, Summary and Outlook section, the authors can add the schematic model of the electrode or the electrolyte/electrode interface relating the future aspect of the sodium-ion batteries.

Response: Thank you for this valuable suggestion. We agree that adding a schematic model will greatly improve the clarity of our outlook on sodium-ion batteries. Therefore, we have added a new schematic illustration of the electrolyte/electrode interface, highlighting key challenges and future research directions for sodium-ion batteries, in the Summary and Outlook section.

To visually clarify the technical routes for future performance enhancement, Figure 7 demonstrates a representative design schematic of electrode/electrolyte interfaces toward next-generation high-performance sodium-ion batteries.

 

 

Figure 7. Schematic diagram of future electrode/electrolyte interface construction strategies for sodium-ion batteries

 

There are some small mistakes mentioned following. Please check and revise it.

1.Page 1, author name and affiliation, “~ Kai Wang 2 and *” should be “~ Kai Wang 2, *”.

2.Page 3, line 110, “~ positive and negative electrode materials; ~” should be “~ cathode and anode materials; ~”. Page 3, line 120, “~ between the positive and negative electrodes, ~” should be “~ between the cathode and anode, ~”.

3.Page 17, line 712, “~ (such as those with a voltage >4.2 V) ~” should be “~ (such as those with a voltage > 4.2 V) ~”.

Response: Thank you for pointing out these typos and inconsistencies. We appreciate your careful review and have corrected all the issues as suggested in the revised manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

In this review the authors report a comprehensive overview of innovation in the electrolyte system, electrode material design and electrode/electrolyte interface engineering for sodium-ion batteries. This review is a summary of latest research articles, reported in the literature, in which the authors highlight the advantages and limitations of the different electrolyte optimization strategies, innovative design cathode and anode materials and the different interface engineering strategies. The paper is well structured and nay be interesting for researchers to address future studies on  sodium-ion batteries with the aim of obtaining better performance and promoting their commercialization.  

To help authors improve their manuscript, I provide additional comments:

1) English must be improved.  

2) I advise authors to check the entire text because there are typos and mistakes, such as: 

- line 738 replace Na₃⁺ with Na⁺.

3)The section 3 – Innovative design of electrode materials – should be partly rewritten to avoid repetition.  The sentences reported from line 331 to line 338 are the same as those from line 382 to 389.

 

Comments for author File: Comments.pdf

Author Response

Dear Reviewer, Thank you for your attention to our research and for your valuable suggestions. We have carefully read your comments and revised our manuscript accordingly. Our specific responses are provided below, with the response and revisions distinguished by different font colors.

In this review the authors report a comprehensive overview of innovation in the electrolyte system, electrode material design and electrode/electrolyte interface engineering for sodium-ion batteries. This review is a summary of latest research articles, reported in the literature, in which the authors highlight the advantages and limitations of the different electrolyte optimization strategies, innovative design cathode and anode materials and the different interface engineering strategies. The paper is well structured and nay be interesting for researchers to address future studies on  sodium-ion batteries with the aim of obtaining better performance and promoting their commercialization.  

To help authors improve their manuscript, I provide additional comments:

• English must be improved.  

Response: Thank you for your positive feedback and constructive suggestions. We have carefully addressed all your comments as follows: We have revised the entire manuscript with the help of a native English speaker with expertise in electrochemistry, to improve grammar, flow, and academic writing style. All language corrections are marked in red in the revised manuscript.

 

2) I advise authors to check the entire text because there are typos and mistakes, such as: 

- line 738 replace Na3+ with Na+.

Response: Thank you for your positive feedback and constructive suggestions.We have carefully checked the entire text and corrected all identified errors, including the one you mentioned.

 

3)The section 3 – Innovative design of electrode materials – should be partly rewritten to avoid repetition.  The sentences reported from line 331 to line 338 are the same as those from line 382 to 389.

Response: Thank you for your positive feedback and constructive suggestions.We have rewritten the relevant parts of Section 3 (Innovative design of electrode materials) to eliminate redundancy.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript is a little better now. However, this manuscript does not provide sufficient data, critical analysis, or comprehensive discussion to be a review article. Authors must write the novelty and aim of this review. Further, all the data and materials mentioned must be cited with the correct journals, and the data in all tables should be cited too. Also, the authors must keep the results of currently published articles (of the last 5 years) and should demonstrate how the results are improving with which modifications. Therefore, it can be acceptable as a review paper on Na-ion batteries after the revision.

Comments on the Quality of English Language

Grammatical errors throughout the draft need to be corrected.

Author Response

Reviewer :

Dear Reviewer, Thank you for your attention to our research and for your valuable suggestions. We have carefully read your comments and revised our manuscript accordingly. Our specific responses are provided below, with the response and revisions distinguished by different font colors.

The manuscript can be accepted after minor revisions to correct typographical errors and improve the clarity of several figures, as detailed below:
1) Figure 2: Several typographical and labeling errors were identified, including “Negativelect” and “SEI MaF”. In addition, the arrows pointing to the NaF-related labels are confusing, as multiple labels such as “NaF”, “SEI NaF”, and “SEI MaF” appear to overlap. The distinction between the labels “SEI MaIm” and “SEI MaF” is also unclear and should be corrected and clarified.

Response: We sincerely thank the reviewer for the careful check and constructive feedback on the labeling issues in Figure 2. We acknowledge that these typographical errors and overlapping labels are our oversight during manuscript preparation, and they would undoubtedly affect the readability and accuracy of the figure. Accordingly, we have made comprehensive revisions to Figure 2.

 

Fig.2 Schematic diagram of component distribution of SEI film rich in NaF

• Figure 3: Several arrows and annotations are difficult to interpret. For example, the arrows indicating atomic positions and the TiB₂ coating thickness appear inconsistent with the structural illustration and the corresponding colored atoms. Moreover, the coating thickness seems to be indicated along the x-axis rather than the z-axis. The meanings of the labels “J” and “3-Type layer oxides+” in the upper-left part of the figure should also be clearly explained.

Response: We sincerely thank the reviewer for the careful examination and constructive feedback on Figure 3. We fully acknowledge that the inconsistent annotations, incorrect dimension orientation, and undefined labels are oversights during figure preparation, which will affect the readability and academic rigor of the manuscript. Accordingly, we have thoroughly revised Figure 3 and supplemented corresponding explanations in the text.

 

Fig.3 Schematic diagram of "element doping/surface coating" structure of layered oxides

 

 

 

 

• Figure 4: Some annotations and arrows appear ambiguous or unreasonable, particularly those associated with “UMTS”, “UMTS structure”, “Pore size”, and “Pore volume”. Furthermore, the distinction between “Ultra-microporous tunnel structure (UMTS)” and “Ultra-microporous tunnel hard carbon (UMTS structure)” is unclear. A clearer description and figure annotation are required. In addition, “Ultra-microproous” should be corrected to “Ultra-microporous”.

Response: We sincerely thank the reviewer for the meticulous review and valuable comments on Figure 4. We fully acknowledge that the ambiguous annotations, unclear terminology distinction, and spelling error are our oversights during figure preparation, which have compromised the clarity and accuracy of the figure. We have thoroughly revised Figure 4 and supplemented corresponding clarifications in the manuscript.

 

Fig.4 Schematic diagram of hard carbon structure

 

 

 

 

• Figure 6: If this figure was quoted from a literature, the original source should be properly cited in both the figure caption and the reference list.

Response: We sincerely thank the reviewer for pointing out this important issue regarding the source citation of Figure 6. We acknowledge that the omission of the original literature source in the original submission was our oversight, which does not conform to standard academic citation specifications.

Aurbach, D. Nonaqueous Liquid Electrolytes for Lithium-Based Rechargeable Batteries. Chem. Rev. 2004, 104, 4303–4417.

 

Author Response File: Author Response.docx