Study of Three-Component Fe₂O₃/TiO₂/rGO Nanocomposite Thin Films Anode for Lithium-Ion Batteries

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this manuscript, the authors report on graphene-iron oxide-titanium dioxide based anode materials for lithium-ion batteries. By varying the ratio of iron oxide to titanium oxide, an anode material with excellent cycling stability and high specific capacity was obtained. The results of this manuscript may be useful for the development of lithium-ion battery electrodes and for further research aimed at improving the efficiency of lithium-ion batteries. This manuscript may be recommended for publication after major revisions.

1. The experimental section should describe the GO reduction process in more detail.
2. Line 128-129. "A volume of 300 μL of electrode consisting of 1 M LiPF 6 dissolved in ethylene carbonate (EC): diethyl carbonate 129 (DEC) 3:7 v/v was added to each cell." This most likely refers to the electrolyte, not the electrode.
3. Most of the figures should be corrected. For example, in Fig. 1: 2 mkm should be replaced with 2 µm. Fig. 2: Theta should be written instead of teta. Similar errors can be found in other figures.
4. Units of measurement should be given in all figures. For example, in Figure 2a, the units for the x and y axes are not given.
5. The XRD pattern should show a decoding of the crystalline phases present. It is not clear from the diagrams to which phases the diffraction peaks belong.
6. How was the crystallite size calculated?
7. It is recommended to provide a table with the calculated parameters of the equivalent circuits of the Nyquist plots.
8. The design of the graphs and diagrams should be in the same style.
9. The list of references is not properly formatted.

Author Response

Comment 1: The experimental section should describe the GO reduction process in more detail.

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have added a more detailed description of the thermal reduction process of graphene oxide (GO) in the Experimental section. Specifically, it now states that reduced graphene oxide was obtained by thermal reduction of GO. The obtained samples were placed in a tubular furnace (SNOL 0.2/1250), and subjected to heat treatment at 550 °C for 2 hours under a continuous argon/hydrogen (Ar/H₂) gas flow with a 95:5 ratio. The heating rate was set to 5 °C/min. The presence of hydrogen gas facilitated the removal of oxygen-containing functional groups (such as hydroxyl, epoxy, and carboxyl groups) from the GO structure, thus enhancing the electrical conductivity of the resulting rGO. The furnace was purged with Ar/H₂ prior to heating to eliminate oxygen traces. The thermal reduction conditions were chosen based on literature reports demonstrating effective GO-to-rGO transformation under similar parameters, which promote partial restoration of sp² hybridized carbon domains  (Dreyer et al., 2010).

 This change can be found on page 3, paragraph 2.1. , lines 94-103.

Comment 2: Line 128–129. "A volume of 300 μL of electrode consisting of 1 M LiPF₆ dissolved in ethylene carbonate (EC): diethyl carbonate (DEC) 3:7 v/v was added to each cell." This most likely refers to the electrolyte, not the electrode.

Response 2: Thank you for pointing this out. We agree with this comment. Therefore, we have corrected the terminology in the revised manuscript by replacing the word "electrode" with "electrolyte" to accurately describe the component added to the cell. This change can be found on page 3, paragraph 2.2., lines 119-121.
[Updated manuscript text:]
"A volume of 300 μL of electrolyte consisting of 1 M LiPF₆ dissolved in ethylene carbonate (EC) and diethyl carbonate (DEC) in a 3:7 v/v ratio was added to each cell."

Comment 3: Most of the figures should be corrected. For example, in Fig. 1: 2 mkm should be replaced with 2 µm. Fig. 2: Theta should be written instead of teta. Similar errors can be found in other figures.

Response 3: Thank you for pointing this out. We agree with this comment. Therefore, we have carefully revised all figures to correct the identified unit and label errors. Specifically, in Figure 1, the unit "2 mkm" has been replaced with "2 µm", and in Figure 2, the label "teta" has been corrected to "theta". Similar typographical and unit corrections have been made throughout the manuscript figures where necessary.
These changes can be found in the revised figures on page 4 (Fig. 1),  (Fig. 2), page 8 (Fig. 8).

Comment 4: Units of measurement should be given in all figures. For example, in Figure 2a, the units for the x and y axes are not given.

Response: Thank you for pointing this out. We have revised Figure 2a to include the appropriate units on both axes. In addition, we have carefully reviewed all other figures and ensured that units of measurement are provided wherever applicable.

Comment 5: The XRD pattern should show a decoding of the crystalline phases present. It is not clear from the diagrams to which phases the diffraction peaks belong.

Response 5: Thank you for the valuable comment. We have revised the XRD figure to indicate and label the diffraction peaks corresponding to the crystalline phases present in each sample. Specifically:

Fe₂O₃/rGO sample: The peaks at 2θ ≈ 30.3°, 43.3°, 53.7°, 57.3°, 62.9° correspond to the (220), (400), (422), (511), and (440) planes of cubic γ-Fe₂O₃ (maghemite) (JCPDS card No. 39-1346).

TiO₂/rGO sample: The peaks at 2θ ≈ 25.3°, 27.4°, 37.9°, 47.9°, 54.3°, 62.9° correspond to: 25.3° → (101) plane of anatase TiO₂ (JCPDS card No. 21-1272), 27.4° → (110) plane of rutile TiO₂ (JCPDS card No. 21-1276). Remaining peaks are consistent with both anatase and rutile mixed-phase TiO₂. rGO: A broad hump at ~24°, indicative of the amorphous or turbostratic structure typical of reduced graphene oxide, likely associated with the (002) plane. Stainless Steel substrate: Peaks around 44–46° and 51–53° correspond to Fe-based steel (γ-Fe or austenitic phase), e.g., (110), (200) planes.

We have now updated the figure legend and added phase markers to the XRD figure to clarify this. The caption now includes peak assignments and JCPDS references.
This update can be found on page 4, paragraph 3.1, and in revised Figure 2.

Comment 6:. How was the crystallite size calculated?

Response 6: Thank you for pointing this out. We agree with this comment. Therefore, we have added a detailed explanation of the crystallite size calculation using the Scherrer equation. The calculation was performed using the most intense diffraction peaks for each sample: at 2θ = 30.3° for Fe₂O₃/rGO, 25.3° for TiO₂/rGO, and ~24° for rGO. The FWHM values were obtained by fitting the XRD peaks using OriginPro software. The corresponding text has been added in the revised manuscript. This change can be found on page 4, paragraph 3.1, lines 143-151.

Comment 7:
It is recommended to provide a table with the calculated parameters of the equivalent circuits of the Nyquist plots.

Response:
Thank you for this valuable suggestion. In response, a new table (Table 1) has been added to the manuscript, presenting the calculated parameters of the equivalent circuit elements fitted to the Nyquist plots of Fe₂O₃/rGO and TiO₂/rGO electrodes. The equivalent circuit consists of a solution resistance (Rs), a constant phase element (CPE) defined by parameters T and P, a charge transfer resistance (Rct), and a Warburg element (W) associated with lithium ion diffusion. The table also includes χ² values to indicate the goodness of fit. This addition enhances the clarity and completeness of the electrochemical impedance analysis. A corresponding explanation has also been added to the main text.

This update can be found on page 7, paragraph 3.1, lines 222-229.

Comment 8:
The design of the graphs and diagrams should be in the same style.

Response 8:
Thank you for pointing this out. We agree with this comment. Therefore, we have revised all graphs and diagrams to ensure a consistent visual style across the manuscript. Specifically, we have unified font types, axis labels, legend formatting, and color schemes. In addition, schematic elements (such as equivalent circuits) were redrawn for clarity and uniformity.
This change can be found in the revised manuscript and throughout the Results and Discussion section where figures appear. Updated figures and captions are included in the revised manuscript.

Comment 9: The list of references is not properly formatted.

Response 9: Thank you for pointing this out. We agree with this comment. Therefore, we have reformatted the entire list of references according to the MDPI citation style, including the correct order of author names, journal titles in italics, volume and issue formatting, and the inclusion of DOI in URL format. This change can be found on pages 14–17, full reference list section. The updated references are provided in the manuscript accordingly.

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript presents a study on the synthesis and electrochemical performance evaluation of Fe₂O₃/TiO₂/rGO nanocomposite anodes for lithium-ion batteries, fabricated using electrophoretic deposition (EPD). The authors investigate how varying the molar ratio of Fe₂O₃ and TiO₂ influences morphology and battery performance. The manuscript is recommended to publish after addressing the following questions/concerns:

1. The manuscript would benefit from a clearer rationale for selecting Fe₂O₃:TiO₂ molar ratios of 1:1, 2:1, and 3:1. Are these based on theoretical capacity considerations, material compatibility, or previous literature? Please elaborate on the selection criteria and any expected trade-offs between electrochemical activity and structural integrity.
2. Please explain how the grain sizes of TiO₂ and Fe₂O₃ were determined from SEM images in Figure 1. If image analysis software was used, kindly mention the method or measurement approach. Including scale bars and annotations would help clarify particle identification.
3. The cyclic voltammetry curves of Fe₂O₃/rGO in Figure 5 show changes in shape and a shift in peak positions over multiple cycles. Please provide a more detailed explanation of these changes, particularly in the context of redox reversibility, SEI formation, or conductivity enhancement during cycling.
4. In Figure 6, the process used to extract charge transfer resistance (Rct) from the Nyquist plots is not clearly described. Please indicate whether an equivalent circuit model was used and how the data were fitted. Also, since the measurements were performed in half-cell configuration, the potential interference from the Li counter/reference electrode should be acknowledged. A symmetric cell configuration would be more appropriate for EIS analysis—please consider this experiment.
5. Table 1 shows inconsistencies in compositional analysis. While the XRD results align with the expected molar compositions, EDX and XPS data show noticeable deviations. Could the authors comment on these discrepancies?
6. Figures 4 and 11 present cycling performance comparisons, but the specific cycling conditions (e.g., voltage window, C-rate, temperature) are not clearly described in the captions or main text. Please clarify these testing parameters to ensure data reproducibility.
7. The authors are encouraged to briefly discuss the scalability of the EPD technique for industrial or commercial electrode fabrication. Points to consider include deposition uniformity, mass loading limits, and compatibility with current collector formats for commercial LIBs.
8. The manuscript really needs careful proofreading and formatting correction to improve overall readability. Two examples are:

1. Figure formatting: For example, Figure 2A lacks clear labeling of spectra; please revise to ensure all panels are labeled and legible.
2. Inconsistent font styles: There are visible font inconsistencies in the main text, particularly on page 6. Ensure uniform formatting across all sections.

Author Response

Comment 1: The manuscript would benefit from a clearer rationale for selecting Fe₂O₃:TiO₂ molar ratios of 1:1, 2:1, and 3:1. Are these based on theoretical capacity considerations, material compatibility, or previous literature? Please elaborate on the selection criteria and any expected trade-offs between electrochemical activity and structural integrity.

Response 1: Thank you for this valuable comment. We appreciate the opportunity to clarify the rationale behind the selected Fe₂O₃:TiO₂ molar ratios. In the revised manuscript (page 3, paragraph 2.1, lines 113-121, marked as blue), we have added an explanation highlighting that the chosen ratios (1:1, 2:1, and 3:1) were selected to systematically investigate the influence of increasing Fe₂O₃ content on the electrochemical performance and structural behavior of the composite anodes. Fe₂O₃ provides high theoretical capacity but suffers from significant volume expansion, while TiO₂ offers structural stability and moderate capacity.

The 1:1 ratio serves as a balanced reference point between the two oxides. The 2:1 and 3:1 ratios allow us to explore how increased Fe₂O₃ content affects capacity enhancement and stability. These choices are also supported by previous studies, such as:

Zuniga et al. (2019), who fabricated α-Fe₂O₃/TiO₂/carbon composites and demonstrated improved performance compared to single-component systems [Appl. Sci. 2019, 9, 4032. https://doi.org/10.3390/app9194032].

Li et al. (2019), who reported improved electrochemical behavior using TiO₂ nanotubes decorated with Fe₂O₃ nanoparticles [J. Alloys Compd. 2019, 783, 793–800. https://doi.org/10.1016/j.jallcom.2018.12.371

These references and our experimental results confirm that varying the Fe₂O₃:TiO₂ molar ratio offers meaningful insights into the design of high-performance anode materials.

Comment 2: Please explain how the grain sizes of TiO₂ and Fe₂O₃ were determined from SEM images in Figure 1. If image analysis software was used, kindly mention the method or measurement approach. Including scale bars and annotations would help clarify particle identification.

Response 2: Thank you for your comment. We agree with this observation. Therefore, we have clarified the method used for determining grain sizes in the revised manuscript. Specifically, grain sizes of TiO₂ and Fe₂O₃ were estimated from the SEM images using ImageJ software by manually outlining individual grains and measuring their diameters. At least 100 particles were analyzed for each sample to obtain statistically meaningful results. Scale bars have now been added to Figure 1 to facilitate better interpretation and identification of the particles.
This change can be found on page 4, paragraph 3.1, line 145-150 of the revised manuscript.

Comment 3: The cyclic voltammetry curves of Fe₂O₃/rGO in Figure 5 show changes in shape and a shift in peak positions over multiple cycles. Please provide a more detailed explanation of these changes, particularly in the context of redox reversibility, SEI formation, or conductivity enhancement during cycling.

Response 3:
Thank you for your insightful comment. We have revised the manuscript to provide a more detailed explanation of the changes observed in the CV curves of the Fe₂O₃/rGO electrode during cycling.

In the first cathodic scan, a broad and intense reduction peak appears around ~0.55 V (vs. Li/Li⁺), corresponding to the initial conversion of Fe₂O₃ to metallic Fe⁰ and the formation of Li₂O. This process is also accompanied by the formation of the solid electrolyte interphase (SEI), which is largely irreversible and contributes to the high initial cathodic current. In subsequent cycles (2nd to 4th), this peak gradually decreases in intensity and shifts to higher potentials (~0.7 V), indicating the stabilization of the electrode–electrolyte interface and suppression of side reactions.

The presence of reduced graphene oxide (rGO) plays a key role in enhancing the electrical conductivity and providing mechanical flexibility to accommodate volume changes during lithiation/delithiation. This leads to more stable and reversible redox behavior in the following cycles.

On the anodic side, an oxidation peak appears around 1.6 V and becomes increasingly pronounced in next cycles. This peak corresponds to the oxidation of Fe⁰ back to Fe²⁺/Fe³⁺ and reflects improved redox reversibility due to enhanced charge transfer kinetics. The increase in anodic peak intensity (reaching ~0.32 mA in the 4th cycle) further confirms the electrochemical activation and stabilization of the Fe₂O₃/rGO composite. These findings are consistent with previously reported behavior for Fe₂O₃-based anodes [Zhang et al., 2015]. This explanation has been added to the revised manuscript on page 7, paragraph 3.1. 212-224 lines.

Comment 4: In Figure 6, the process used to extract charge transfer resistance (Rct) from the Nyquist plots is not clearly described. Please indicate whether an equivalent circuit model was used and how the data were fitted. Also, since the measurements were performed in half-cell configuration, the potential interference from the Li counter/reference electrode should be acknowledged. A symmetric cell configuration would be more appropriate for EIS analysis—please consider this experiment.

Response 4:
Thank you for this valuable observation. We appreciate the opportunity to clarify the electrochemical impedance spectroscopy (EIS) analysis presented in Figure 6. The charge transfer resistance (Rct) values were extracted by fitting the Nyquist plots using an equivalent circuit model consisting of an electrolyte resistance (Rs), a constant phase element (CPE), and a charge transfer resistance (Rct), arranged in series as: Rs – (CPE ‖ Rct). The data were fitted using ZView software, and the fitting quality was verified by minimizing the chi-squared value.

We agree that EIS measurements in a half-cell configuration can be influenced by the presence of the lithium metal counter/reference electrode, especially due to its high interfacial reactivity and unstable SEI layer. Therefore, in the revised manuscript, we have acknowledged this limitation and discussed its possible effect on the extracted impedance values.

Although a symmetric cell would indeed provide a more accurate assessment of the intrinsic impedance characteristics of the electrode material, such a measurement was not conducted in the present study. However, we recognize the value of this suggestion and will consider performing symmetric cell EIS in future work.

This clarification has been included in the revised manuscript on page 7, paragraph 3.1. lines 244-250.

Comment 5: Table 1 shows inconsistencies in compositional analysis. While the XRD results align with the expected molar compositions, EDX and XPS data show noticeable deviations. Could the authors comment on these discrepancies?

Response 5:
Thank you for your observation. We acknowledge the discrepancies between the compositional data obtained from XRD, EDX, and XPS analyses, and we have now included an explanation in the revised manuscript. These deviations arise from the fundamental differences in the depth sensitivity and detection principles of the techniques: XRD provides bulk crystallographic information and reflects the overall phase composition of the material, typically in the micrometer range. EDX (coupled with SEM) offers localized elemental composition, usually limited to a few micrometers in depth, and can be affected by surface inhomogeneities, particle agglomeration, or non-uniform element distribution. XPS, in contrast, is highly surface-sensitive, probing only the top 5–10 nm of the sample, and is strongly influenced by surface oxidation, contamination, or residual functional groups, especially in rGO-containing composites. Therefore, the observed deviations are attributed to surface enrichment, partial oxidation states, and differences in spatial resolution across the techniques. This clarification has been added to the revised manuscript on page X, paragraph Y. We have also noted that such variations are commonly reported in nanocomposite systems and should be interpreted in the context of each technique's limitations.

This clarification has been included in the revised manuscript on page 11, paragraph 3.1. lines 344-353.

Comment 6: Figures 4 and 11 present cycling performance comparisons, but the specific cycling conditions (e.g., voltage window, C-rate, temperature) are not clearly described in the captions or main text. Please clarify these testing parameters to ensure data reproducibility.

Response 6:
Thank you for this important remark. We agree that providing detailed cycling conditions is essential for reproducibility. In the revised manuscript, we have included a clear description of the electrochemical testing parameters used in Figures 4 and 11.

The cycling tests were performed in Swagelok-type cells using a lithium metal counter electrode. The cells were cycled in a voltage window of 0.01–3.0 V (vs. Li/Li⁺) at a constant current corresponding to a C-rate of 1C. All measurements were carried out at room temperature (25 ± 2 °C). This information has been added both in the figure captions and in the experimental section of the revised manuscript on page 6, paragraph 3.1. lines 196-199.

Comment 7: The authors are encouraged to briefly discuss the scalability of the EPD technique for industrial or commercial electrode fabrication. Points to consider include deposition uniformity, mass loading limits, and compatibility with current collector formats for commercial LIBs.

Response 7:
Thank you for this valuable suggestion. We have added a short discussion in the revised manuscript regarding the scalability of the electrophoretic deposition (EPD) method for practical electrode fabrication. EPD is considered a promising technique for large-scale manufacturing of binder-free electrodes due to its simplicity, low cost, and versatility in depositing uniform coatings on various conductive substrates. It allows for good control over film thickness and mass loading by adjusting deposition time, voltage, and suspension concentration. However, challenges such as maintaining deposition uniformity over large areas, achieving high areal mass loading, and ensuring strong adhesion to commercial current collectors (e.g., Cu foil, stainless steel) must be addressed through process optimization. Notably, EPD is already compatible with roll-to-roll production and can be applied to substrates commonly used in lithium-ion battery manufacturing. This discussion has been included in the revised manuscript on page 15, paragraph 3.2. lines 462 -472.

Comment 8: The manuscript really needs careful proofreading and formatting correction to improve overall readability. Two examples are:  Figure formatting: For example, Figure 2A lacks clear labeling of spectra; please revise to ensure all panels are labeled and legible. Inconsistent font styles: There are visible font inconsistencies in the main text, particularly on page 6. Ensure uniform formatting across all sections.

Response 8: Thank you for pointing this out. We agree with this comment. Therefore, we have thoroughly proofread the entire manuscript and corrected multiple formatting inconsistencies. Figure 2A has been revised to include clear labeling for all spectra and improved legibility for each panel. Font style inconsistencies have been corrected throughout the manuscript, especially on page 6, to ensure a uniform and professional appearance. The formatting corrections have been made in the figure captions and included into the revised manuscript (page 6, Section 3.1, Figure 2, left panel).

 

 

 

Reviewer 3 Report

Comments and Suggestions for Authors

Reduced graphene oxide (rGO) is a promising material for use in lithium-ion batteries (LIB) as a component of electrode materials. Thus, the relevance of the article is due to the electrochemical synthesis of composite electrodes based on Fe2O3/TiO2/rGO. The use of graphene oxide as a reinforcing additive allows creating a buffer between individual Fe2O3 and TiO2 nanoparticles, as well as increasing the physicochemical properties of the anode composite, including reactivity. The article presents a wide range of electrochemical studies of new composite materials and electron microscopy. The article is well illustrated, and the results obtained are correctly interpreted. Most of the comments are related to the design of the article. The results of the article leave a positive impression.
Comments:
1. The title of the article should be improved. Based on the text of the article, it would be more appropriate to call it, for example: "Study of Three-Component Fe2O3/TiO2/rGO Nanocomposite Thin Films Composite Anode for Lithium-Ion Battery";
2. The Introduction section provides useful information on anode materials. It would also be more informative to provide a table of known anodes, which would include information on advantages and disadvantages, as well as specific capacity, etc.;
3. The manuscript lacks relevant references for the last 5 years, the list of references should be expanded with articles for the last 5 years. [https://doi.org/10.1016/j.mtelec.2024.100089] should be inserted in line 35. The reference [https://doi.org/10.1134/S1070363222060317] can be inserted in line 50;
4. The Introduction section should also provide more detailed information on GO and rGO-based anode materials and their application in metal oxide composite electrodes as an additive, etc. In the present form, a small paragraph on graphene is presented. Although the authors present a composite based on reduced graphene oxide in their work;
5. The article lacks a section on "Methods and Materials". In this regard, section "2. Experimental" should be called "2. Methods and Materials". Line 107 presents the parameters of electrochemical deposition, but the value of the cathode polarization potential is missing. The article does not provide the material of the substrate (cathode) on which the electrodeposition of Fe2O3/TiO2/rGO films was performed, as well as the cathode material;
6. In the description of methods and materials, not all methods used in the work are described, for example, XRD, Raman spectra, SEM, etc. It is also unclear from the text of the article at what temperature graphene oxide was reduced and the duration of the heat treatment of the material is also not indicated;
7. Figure 1 should be divided into (a) and (b), the same applies to figures 2 and 3. It is also necessary to improve the quality of Figure 1;
8. In Figure 5, the profile of the 1st cycle for the Fe2O3/rGO composite is not aligned with the subsequent ones. What is the reason for this?;
9. What is the reason for the difference between the imaginary part of the EIS (Figs. 6 and 13) of the TiO2/rGO and Fe2O3/rGO composites?;
10. The electrolyte and its concentration should be indicated in the caption of the figure;
11. It would also be informative to include the Faraday efficiency of the obtained electrodes in the article;
12. It would be somewhat better to separately present all the electrochemical reactions on the composite anodes shown in the graphs of Figure 5.
13. It is also unclear from the article whether the authors assessed the residual functional groups on the RGO surface? And how do they affect the reactivity as a whole?
14. In conclusion, it is not shown what positive effect the composite anode has from the inclusion of the rGO film.

Comments on the Quality of English Language

The English could be improved to more clearly express the research.

Author Response

Comment 1: The title of the article should be improved. Based on the text of the article, it would be more appropriate to call it, for example: "Study of Three-Component Fe₂O₃/TiO₂/rGO Nanocomposite Thin Films Composite Anode for Lithium-Ion Battery."

Response 1: Thank you for this helpful suggestion.
We agree with the reviewer that the original title can be improved to better reflect the scope and focus of the manuscript. Therefore, we have revised the title to:
"Study of Three-Component Fe₂O₃/TiO₂/rGO Nanocomposite Thin Films as Anode for Lithium-Ion Batteries." This revised title highlights the multi-component structure, material form (thin films), and its specific application. The updated title appears on the title page and in the manuscript header.

Comment 2: The Introduction section provides useful information on anode materials. It would also be more informative to provide a table of known anodes, which would include information on advantages and disadvantages, as well as specific capacity, etc.

Response 2: Thank you for this suggestion. We agree that the comparative table summarizing known anode materials would enhance the clarity and value of the Introduction. Therefore, we have added a new table (Table 1 Summary of Selected Anode Materials for Lithium-Ion Batteries) that presents an overview of selected anode materials, including their specific capacity, advantages and disadvantages.
This addition provides a perspective on the reasoning behind our choice of Fe₂O₃/TiO₂/rGO as a composite material. The table has been inserted in the Introduction section (page 2), and text has been modified (lines 76-82).

Comment 3: The manuscript lacks relevant references for the last 5 years. The list of references should be expanded with articles from the last 5 years. [https://doi.org/10.1016/j.mtelec.2024.100089] should be inserted in line 35. The reference [https://doi.org/10.1134/S1070363222060317] can be inserted in line 50.

Response 3: Thank you for this valuable suggestion. We agree that the manuscript benefits from including recent literature to ensure relevance and scientific currency. Therefore, we have added two references from the past five years: Mishra et al. (2024) https://doi.org/10.1016/j.mtelec.2024.100089] has been cited in line 30 to support the discussion of recent advancements in anode materials for lithium-ion batteries. Shchegolkov et al. (2022) [https://doi.org/10.1134/S1070363222060317] has been included in line 50. Both references have also been added to the reference list in MDPI format.

Comment 4: The Introduction section should also provide more detailed information on GO and rGO-based anode materials and their application in metal oxide composite electrodes as an additive, etc. In the present form, a small paragraph on graphene is presented. Although the authors present a composite based on reduced graphene oxide in their work.

Response 4:
Thank you for this valuable suggestion. We agree with this comment. Therefore, we have significantly expanded the Introduction section to include a more detailed discussion on graphene oxide and reduced graphene oxide based anode materials. We describe their key structural and electrochemical properties, their role as conductive additives in metal oxide composites, and their synergistic effects in improving electrode stability, conductivity, and capacity retention. This additional information highlights the rationale behind incorporating rGO in Fe₂O₃/TiO₂-based composite.
This change can be found on page 2, lines 65–85 of the revised manuscript.

Comment 5.The article lacks a section on "Methods and Materials". In this regard, section "2. Experimental" should be called "2. Methods and Materials". Line 107 presents the parameters of electrochemical deposition, but the value of the cathode polarization potential is missing. The article does not provide the material of the substrate (cathode) on which the electrodeposition of Fe₂O₃/TiO₂/rGO films was performed, as well as the cathode material.

Response 5:
We thank the reviewer for this helpful observation. In response, we have renamed section 2. Experimental to 2. Methods and Materials to reflect its content more accurately and to align with standard scientific structure.

Additionally, we have included the missing value of the cathodic polarization potential, which was –30 V, and we now clearly state that the substrate (cathode) used for electrodeposition was stainless steel (AISI 304, thickness 0.5 mm). These details enhance the clarity and reproducibility of the experimental procedure. The corresponding revisions can be found on page 4, lines 118–123 of the revised manuscript.

Comment 6: In the description of methods and materials, not all methods used in the work are described, for example, XRD, Raman spectra, SEM, etc. It is also unclear from the text of the article at what temperature graphene oxide was reduced and the duration of the heat treatment of the material is also not indicated.

Response 6: Thank you for this important remark. We acknowledge that some characterization and processing details were missing in the original submission. To address this, the Methods and Materials section has been revised and new paragraph 2.2. Material characterization was added to include complete descriptions of the analytical techniques and reduction process. 

 The reduction of graphene oxide was performed via thermal treatment at 550 °C for 2 hours in an inert atmosphere. This temperature and duration are now clearly stated in the revised manuscript (paragraph 2.1). These additions improve the transparency and reproducibility of the study and appear on lines 126-137 of the revised manuscript.

Comment 7:
Figure 1 should be divided into (a) and (b), the same applies to figures 2 and 3. It is also necessary to improve the quality of Figure 1.

Response 7:
We appreciate the reviewer’s helpful comments regarding the figures. In the revised manuscript: Figure 1 ( A and B), Figure 2 (left and right),  as suggested, to improve clarity and facilitate reference in the text. The image resolution and overall quality of figures have been significantly enhanced, ensuring better visibility of structural and morphological details.

Comment 8:
In Figure 5, the profile of the 1st cycle for the Fe₂O₃/rGO composite is not aligned with the subsequent ones. What is the reason for this?

Response 8:
We thank the reviewer for this important observation. The deviation of the 1st cycle profile in the cyclic voltammetry (CV) curve is a well-known and commonly observed phenomenon in metal oxide-based anode materials. The difference arises primarily due to electrochemical activation and the formation of the solid electrolyte interphase during the initial lithiation process. In the 1st cycle, irreversible reactions occur, such as the reduction of Fe³⁺ to Fe⁰, decomposition of electrolyte components, and the formation of Li₂O and SEI layer, which do not repeat in subsequent cycles. These processes lead to a higher cathodic current and a shift in peak positions. From the 2nd cycle, the electrode stabilizes, and redox peaks become more consistent, reflecting the reversible redox behavior of Fe²⁺/Fe⁰ and Fe³⁺/Fe²⁺ couples. To clarify this, we have included an explanatory text in the revised manuscript on page 8, lines 26 - 272.

Comment 9:
What is the reason for the difference between the imaginary part of the EIS (Figs. 6 and 13) of the TiO₂/rGO and Fe₂O₃/rGO composites?

Response 9:
We thank the reviewer for this insightful question. The difference in the imaginary part of the impedance spectra (–Im(Z)) between the Fe₂O₃/rGO, TiO₂/rGO (Fig 6) and FT11, FT21 (Fig 13) composites is mainly attributed to differences in their charge-transfer resistance (Rct), ion diffusion behavior, and interfacial characteristics. The FT11 and FT21 composites shows a higher imaginary impedance component, indicating greater Warburg impedance, which reflects slower lithium-ion diffusion through the electrode/electrolyte interface and within the bulk of the active material. This can be due to the larger particle size and less favorable conductivity of FT11, FT21 composites compared to Fe₂O₃/rGO, TiO₂/rGO.

Comment 10:
The electrolyte and its concentration should be indicated in the caption of the figure.

Response 10:
We thank the reviewer for this helpful suggestion. Although the electrolyte type and concentration were already described in the Methods and Materials section, we agree that repeating this information in the figure captions enhances clarity and accessibility. Therefore, we have updated the captions of Figures 5, 6, and 13 to include the following specification: “Electrolyte: 1 M LiPF₆ in EC:DMC (1:1 v/v)”.

Comment 11: It would also be informative to include the Faraday efficiency of the obtained electrodes in the article.

Response 11:
We appreciate the reviewer’s insightful suggestion. We fully agree that Faradaic efficiency is an important parameter when evaluating electrochemical processes. However, in the present study, our focus was on structural, morphological, and cycling performance characterization of the electrodes. Accurate determination of Faradaic efficiency would require additional experiments under strictly controlled conditions, including quantitative gas analysis or charge/mass balance measurements, which were beyond the scope of this work. Nonetheless, we acknowledge the importance of this parameter and plan to include Faradaic efficiency measurements in future studies to improve the electrochemical evaluation of the developed materials.

Comment 12:
It would be somewhat better to separately present all the electrochemical reactions on the composite anodes shown in the graphs of Figure 5.

Response 12:
We appreciate the reviewer’s suggestion. In response, we have separated the electrochemical reactions corresponding to the Fe₂O₃/rGO and TiO₂/rGO composite anodes and now present them clearly and systematically in the revised manuscript. These reactions, which were previously annotated directly on the CV curves in Figure 5, are now also described in the text of the Results and Discussion section to enhance readability and scientific clarity. The electrochemical processes include the conversion reaction of Fe₂O₃ to Fe⁰ and Li₂O, the formation of intermediate lithium–iron oxide phases, and the lithium intercalation/deintercalation in TiO₂. The relevant reactions are now listed and discussed on page 8, lines 272–279 of the revised manuscript.

Comment 13:
It is also unclear from the article whether the authors assessed the residual functional groups on the RGO surface? And how do they affect the reactivity as a whole?

Response 13:
We thank the reviewer for raising this important point. In the present study, we did not perform a direct quantitative assessment of the residual functional groups on the rGO surface (e.g., via XPS or FTIR analysis after reduction). However, based on the synthesis conditions used (thermal treatment ), we expect that a partial removal of oxygen-containing groups occurred, resulting in partially reduced graphene oxide (prGO) with residual –OH, –COOH, or epoxy groups. These residual groups can play a dual role:
-On the one hand, they slightly reduce the electrical conductivity of the rGO network compared to pristine graphene;
-On the other hand, they can improve electrode wettability, facilitate Li⁺ ion access, and even form chemical bonds with metal oxides, enhancing the mechanical and electrochemical stability of the composite during cycling.

To address the reviewer’s comment, we have added a brief discussion on this in the Results and Discussion section on page 17, lines 528–537, and acknowledged it as a limitation and opportunity for future work.

Comment 14:
In conclusion, it is not shown what positive effect the composite anode has from the inclusion of the rGO film.

Response 14:
We appreciate the reviewer’s comment. In response, we have revised the conclusion section to clearly highlight the positive impact of rGO inclusion in the composite anodes. We emphasize that the presence of the rGO film improves:
Electrical conductivity of the electrode;
Structural stability during cycling by buffering volume changes;

This addition underscores the role of rGO as a critical component contributing to the overall performance of the composite. The revised sentence has been added to the Results and Discussion  section on page 17, lines 537-540.

 

 

 

 

 

 

 

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have corrected the previously identified errors. The quality of the manuscript has been significantly improved. The manuscript can be accepted for publication.

Author Response

Comments: The authors have corrected the previously identified errors. The quality of the manuscript has been significantly improved. The manuscript can be accepted for publication.

Response: We sincerely thank the reviewer for their careful re-evaluation of our manuscript and for the positive recommendation for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

All concerns have been addressed. I would recommend publication.

Author Response

Comments: All concerns have been addressed. I would recommend publication.

Response: We sincerely thank the reviewer for their careful re-evaluation of our manuscript and for the positive recommendation for publication.

Reviewer 3 Report

Comments and Suggestions for Authors

After a second careful review of the manuscript, it can be noted that the authors have seriously revised the content of the article. The only significant remark in my opinion is that the authors did not justify the choice of the coefficient K = 0.9 in the Scherrer equation. Usually K = 0.95 or K = 1. It would be good if the authors would somehow comment on this point.
In general, it can be noted that the manuscript has been significantly improved. The authors politely responded to all comments and questions, supplementing their research with reasoned comments and conclusions. The article certainly has theoretical and practical significance for a potential reader.

Author Response

Comment: The only significant remark in my opinion is that the authors did not justify the choice of the coefficient K = 0.9 in the Scherrer equation. Usually K = 0.95 or K = 1. It would be good if the authors would somehow comment on this point.

Response: We thank the reviewer for the positive evaluation and the insightful remark regarding the Scherrer equation. In our calculation of the crystallite size, we used a shape factor K = 0.9, which is commonly applied in the literature for spherical or nearly spherical particles with cubic symmetry (Monshi, A., Foroughi, M. R., & Monshi, M. R. (2012). Modified Scherrer Equation to Estimate More Accurately Nano-Crystallite Size Using XRD. World Journal of Nano Science and Engineering, 2(3), 154–160). However, we acknowledge that values of K between 0.89 and 1.0 are used depending on particle shape and structure. Since our synthesized materials consist of semi-spherical or agglomerated nanoparticles as observed in SEM, we found K = 0.9 to be an appropriate approximation.