Feasibility Study of Current and Emerging Battery Chemistries for Electric Vertical Take-Off and Landing Aircraft (eVTOL) Applications
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors(1) Can the author provide a definition of whether the method proposed in this article is applicable to all types of eVTOLs.
(2) The numerous formulas involved in the second part of the research methodology are all based on certain literature sources, but they are not applicable to all eVTOLs. Please provide an explanation of the scope of application for the author.
(3) How is the "Requirement for eVTOL" provided in Tables 7 and 9? Please explain in detail.
(4) Where is the data source for Figure 1?
(5) There are some formatting issues on page 4 of the paper, please have the author correct them.
(6) Is the time given in Figures 3, 4, and 5 only 700 seconds too short? A normal eVTOL flight usually takes a few hours. Also, which flight phase of eVTOL is being simulated here?
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript presents a comprehensive analysis to establish battery requirements for electric vertical take-off and landing (aVTOL) aircraft applications. Based on the established requirements, current and new battery chemistries are evaluated to identify the most suitable candidates for this use case. The results are validated using simulations. The developed eVTOL simulation model is applied to a representative 12-minute flight profile for two real-world eVTOL aircrafts, the Volocopter VoloCity light wingless vehicle and the Archer Midnight heavy vectored thrust aircraft. The battery state of charge , discharge current and voltage evaluated. 300 commercial cells from a large database were analysed and the Molicel INR21700-P45B cell was selected as the most suitable for eVTOL flight. Similar comparative analysis was also conducted for new battery chemistries., which concluded that solid-state batteries with sulfide electrolytes and silicon-based anodes are the most promising for improving eVTOL performance and safety. The Conclusion section outlines the outlook for future research work.
The information presented in the manuscript is of scientific and practical interest, the relevance of the topic topic is due to the need to reduce the environmental impact in the aviation sector through technological innovation, including the electrification of aircraft, the success of which largely depends on overcoming significant problems in battery technology.
The applied methodology allowed the authors to establish the requirements for batteries for eVTOL applications based on a comprehensive analysis using analytical modeling and available data from real eVTOL aircraft. The conclusion correspond to the presented arguments and meet the task set by the authors. References to published materials are appropriate, the published materials considered in the review chapter of the manuscript reveal the state of the problem, based on which the authors formulated the task of their study. The figures are informative and sufficiently fully illustrate the content of the presented material. The tables provide the information required to disclose the topic.
Thetre is the following recommendation:
Looking forward, consider the battery requirements for eVTOL flight with multiple take-off s and landings, which is typical for applications such as air taxis. 9
Author Response
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Author Response File: 
Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsThis article examines the highly relevant topic of the development of electric vertical take-off and landing (eVTOL) aircraft, with a focus on their battery technologies. Given the increasing pressure to reduce the environmental impact of the transportation sector, the study is of particular relevance, as it highlights the need to improve battery technologies to meet the technical and operational requirements of eVTOL. The article also makes an important contribution to the scientific literature, as it reviews not only the batteries currently on the market but also their latest alternatives, including solid-state batteries.
The title of the article is aptly formulated and accurately reflects its content. The authors thoroughly examine the suitability of current and emerging battery chemistries for eVTOL use, taking into account such important aspects as energy density, power density, and battery safety. This topic is not only relevant but also innovative, as most previous studies have limited themselves to narrower battery performance parameters without providing a comprehensive analysis of their suitability for eVTOL.
The presented analysis uses a clear technique and is rather thorough. Using mathematical modeling and thorough technical parameter evaluations, the writers evaluate the suitability of batteries for specific eVTOL aircraft, such as the Volocopter VoloCity and Archer Midnight. The authors clearly state why it is necessary to improve current battery technologies and present arguments why solid-state batteries may be an ideal solution. The study not only summarizes existing knowledge but also provides concrete data that can stimulate the practical application of these technologies. This includes an analysis of gravimetric energy density and power density, which are key in determining the suitability of batteries.
The list of references includes important sources that support the statements made in the article. However, it would be useful to add more sources related to practical applications of eVTOL in order to better connect theoretical data with real industry practices.
In terms of structure and style, the article is written clearly and coherently. It is recommended that further work include more practical experiments and consider battery operating conditions to further strengthen the analytical part of the article.
The details of my remarks are provided below:
(Lines 18–29): Lacks a more detailed discussion of other alternative solutions, such as hydrogen fuel cells or hybrid systems. At least one additional paragraph discussing these technologies is needed.
(Lines 30–36): The discussion of Urban Air Mobility focuses only on technologies. Lacks an analysis of socio-economic challenges. Needs to mention costs, infrastructure, or regulation.
(Lines 52–56): The study is limited to gravimetric energy density and power density. Needs to expand the analysis to include economic aspects such as production cost or operating costs.
(Lines 58–62): Insufficient detail is given to the limitations of previous studies. Needs to provide more examples of how this study fills these gaps.
(Lines 82–114): The models are complex and may be difficult to understand for a wider audience. Needs to provide a simplified diagram or explanations.
(Line 91): The table is not intuitive—phase names and parameters could be visually separated. It is necessary to add colors or icons to distinguish phases.
(Lines 115–130): The calculations are well presented, but it is not clear how they would be affected by extreme conditions (e.g., strong winds). Such scenarios should be discussed.
(Lines 133–137): The lift-to-drag ratio values are not based on real model data. It is necessary to rely on empirical data from manufacturers.
(Line 147): The table provides a lot of data, but short comments on their importance are missing. Explanations should be added after each parameter.
(Line 154): The table is missing a description of the conditions. It is necessary to mention that these are optimistic conditions without environmental factors.
(Lines 160–188): References to practical examples where these parameters have already been used are missing. Information about similar real systems should be added.
(Lines 203–220): Insufficient attention to manufacturing cost analysis. A table with conditional manufacturing costs should be added.
(Lines 228–250): Focuses on theoretical shortcomings but lacks empirical support. Experimental data should be provided.
(Lines 259–278): Insufficient attention to technology challenges. Difficulties in manufacturing and mass application should be detailed.
(Lines 284–295): Lack of clarity on how simulation accuracy was verified. Discussion of accuracy validation should be added.
(Lines 360–370): Insufficient discussion of battery performance under real-world conditions. Discussion of battery performance over a longer period of time should be added.
(Lines 380–393): Strong analysis provided, but potential shortcomings not discussed. Discussion of temperature effects should be added.
(Line 387): Lacks a clear comparison between different chemicals. A graphic should be created to visualize the differences.
(Lines 394–404): No analysis of the environmental impact of battery production. A discussion of sustainability aspects should be added.
(Line 406): Limitations are presented too succinctly. A detailed discussion of how they may affect the results is needed.
(Lines 421–429): Strong conclusions are presented, but there is no overview of how this knowledge could be used in industry. A description of practical applications should be added.
(Line 431): Lacks specific suggestions for further improvements to solid-state batteries. Specific research directions should be identified.
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
Comments and Suggestions for Authorsvery well done work. Maybe the authors could better specify in the tables when they are referring to cell mass or to the pack mass.
Author Response
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Author Response File: Author Response.pdf
Reviewer 5 Report
Comments and Suggestions for AuthorsThank you for inviting me to review the manuscript below:
Ms. Ref. No.: wevj-3454414
Title: Feasibility Study of Current and Emerging Battery Chemistries for Electric Vertical Take-Off and Landing Aircraft (eVTOL) Applications
This paper focuses on the feasibility study of current and emerging battery chemistries for electric vertical take-off and landing (eVTOL) aircraft applications. The paper is well written, the methodology is well presented, and the results are clearly stated. However, the manuscript requires major revisions. My comments are as follows:
1. The originality of the study should be emphasized. In the abstract, striking sentences highlighting the significance of the work should be added.
2. The novelty and originality of the study should be further justified, ensuring that the manuscript provides sufficient contributions to the body of knowledge. The knowledge gap needs to be clearly addressed in the Introduction section.
3. All existing equations must be properly cited.
4. More information should be provided regarding the validation of the simulation model. This part is currently missing. The model can be validated using various methods, such as MSE, RMSE, and R. See the article https://doi.org/10.1016/j.ijhydene.2022.03.230, which may be relevant for citation.
5. Please clarify the source of the model input data. Is the data obtained from actual measurements or other published articles?
6. The Results and Discussion section should be expanded by incorporating more literature references. Results should be compared with those of other authors in the field.
7. There are several errors in English throughout the text. The manuscript should be carefully reviewed and corrected for grammar and clarity.
Comments on the Quality of English Language1. There are several errors in English throughout the text. The manuscript should be carefully reviewed and corrected for grammar and clarity.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsI'm fully satisfied with the improvements of the paper.
Reviewer 5 Report
Comments and Suggestions for AuthorsThank you for inviting me to review the manuscript below:
Manuscript Number: wevj-3454414
Article Type: Full-length article
Title: Feasibility Study of Current and Emerging Battery Chemistries for Electric Vertical Take-Off and Landing Aircraft (eVTOL) Applications
This paper focuses on the study of current and emerging battery chemistries for electric vertical Take-Off and landing aircraft applications. The concept is interesting, the methodology is well presented, and all my comments have been fulfilled. The paper can be published in the WEVJ journal.
Comments on the Quality of English LanguageIn the text, there are errors in English, which need to be carefully read and corrected.
