One-Pot Bottom-Up Synthesis of SiO2 Quantum Dots and Reduced Graphene Oxide (rGO) Nanocomposite as Anode Materials in Lithium-Ion Batteries
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors1. The paper presents an innovative synthesis method for the growth of crystalline SiO2 quantum dots (QDs) within a reduced graphene oxide (rGO) layer by a solution-mode chemical growth process at a relatively low temperature (100 °C) and its application to anode materials for lithium-ion batteries. However, in the introduction section, the unique features of the method in preparing SiO2-rGO nanocomposites compared with the existing studies, such as the key differences and advantages with the previously reported synthesis methods of SiO2/C composites, should be more emphasized to further highlight the novelty of the study.
2. There is insufficient elaboration of the basis for the selection of key parameters in the experimental process. For example, parameters such as the amount of Si starting material (3 - aminopropyl) trimethoxysilane (APTMS), the concentration of ascorbic acid (AA), the reaction time and temperature, etc., it should be explained in detail how these parameters were determined and whether optimization studies were carried out on these parameters to ensure that the experimental conditions are reasonable and scientific.
3. In the XRD analysis, only the shift of the main peaks before and after annealing is pointed out, and the reasons for the shift of the peaks should be explained in depth, e.g., whether it is related to the change of the crystal structure (e.g., increase in crystallinity, change in the grain size, etc.), the interaction between SiO₂ and rGO.
4. The writing style, grammar and language usage should be checked .
5. The analysis of the D and G bands in Raman spectroscopy can be more detailed, for example, by analyzing the peak shape, half-height width, and other parameters of the D and G bands, to further explore the changes in the carbon structure before and after annealing, as well as the intrinsic connection between such changes and the electronic conductivity and electrochemical properties of the composites, instead of limiting only to the changes in the ID/IG ratio.
Comments on the Quality of English LanguageThe writing style, grammar and language usage should be checked.
Author Response
Response to the Reviewer 1
Many thanks to all the reviewers for reviewing our manuscript and the constructive comments. These comments were very useful improve the quality of our manuscript. We have carefully read all the comments and made necessary modifications marked in red and underlined in the manuscript. Following is the point-to-point response to the reviewers’ comments.
Open Review
(x) I would not like to sign my review report
( ) I would like to sign my review report
Quality of English Language
( ) The quality of English does not limit my understanding of the research.
(x) The English could be improved to more clearly express the research.
Comments and Suggestions for Authors
Comment 1. The paper presents an innovative synthesis method for the growth of crystalline SiO2 quantum dots (QDs) within a reduced graphene oxide (rGO) layer by a solution-mode chemical growth process at a relatively low temperature (100 °C) and its application to anode materials for lithium-ion batteries. However, in the introduction section, the unique features of the method in preparing SiO2-rGO nanocomposites compared with the existing studies, such as the key differences and advantages with the previously reported synthesis methods of SiO2/C composites, should be more emphasized to further highlight the novelty of the study.
Response 1. Many thank you for this constructive comment. We have done extensive revision to the introduction part to highlight the novelty of the study.
Changes in the revised manuscript:
Line 33-37,
and hollow and porous structures [7],[8] thereby … (@1C) over 500 cycles[6] and 919 mAhg-1 over 30 cycles[7].
Line 43-54,
and nanostructured silica/carbon … and 800 mAhg−1 @200 mAg−1 after 20 cycles [14].All
Line 60-66,
flexibility to accommodate … Therefore, we developed a solution mode low temperature
Comment 2. There is insufficient elaboration of the basis for the selection of key parameters in the experimental process. For example, parameters such as the amount of Si starting material (3 - aminopropyl) trimethoxysilane (APTMS), the concentration of ascorbic acid (AA), the reaction time and temperature, etc., it should be explained in detail how these parameters were determined and whether optimization studies were carried out on these parameters to ensure that the experimental conditions are reasonable and scientific.
Response 2. Many thank you for such a very good comment. Although, we submitted a compact paper for publication, we had done systematic experiments to optimize all the parameters. For example, we have changed the ascorbic acid (AA) concentration from 0. 1M to 0.6 M to prepare the SiOx/rGO nanocomposite keeping all other parameters such as GO concentration, APTMS concentration and the NaBH4 concentration fixed. The composite prepared by using 0.3M AA showed high crystallinity in the XRD spectra as shown below (Figure R1). Similarly, all other parameters were also optimized by series of experiments (not shown here). In the paper, we have reported the electrochemical properties of the 0.3M AA modified SiOx/rGO nanocomposite.
Figure R1. XRD Spectra of the SiOx/rGO composite prepared by changing the AA concentration.
Comment 3. In the XRD analysis, only the shift of the main peaks before and after annealing is pointed out, and the reasons for the shift of the peaks should be explained in depth, e.g., whether it is related to the change of the crystal structure (e.g., increase in crystallinity, change in the grain size, etc.), the interaction between SiO₂ and rGO.
Response 3. Many thanks for such an interesting comment. The main XRD peak at 26.56° for un-annealed sample shifted toward lower Bragg angle of 26.33° after annealing at 650°C. The peak shift is minor of 0.23° and therefore, we expect an increase in the crystallinity of SiO2 after annealing.
Comment 4. The writing style, grammar and language usage should be checked .
Response 4. Thanks a lot for the constructive comment. We have rechecked our manuscript several times to avoid any grammar error.
Comment 5. The analysis of the D and G bands in Raman spectroscopy can be more detailed, for example, by analyzing the peak shape, half-height width, and other parameters of the D and G bands, to further explore the changes in the carbon structure before and after annealing, as well as the intrinsic connection between such changes and the electronic conductivity and electrochemical properties of the composites, instead of limiting only to the changes in the ID/IG ratio.
Response 5. Thank you very much for such nice comment. We understand that Raman spectroscopy can be used to do several analysis about the phonon modes in various materials. However, we are not experts in Raman spectroscopy. We used the technique to analyze the materials. Therefore, we have revised the Raman analysis part as follows
The Raman spectra in GO or rGO usually show three peaks corresponding to D band (1342 cm−1), G band (1594.8 cm−1) and 2D band (2700 cm−1) respectively. The D band is usually a defect peak within the carbon structure that exhibit sp3 bonded carbon atoms, whereas the G band is sp2 bonded carbon atoms in the honey-comb lattice. The 2D band at 2700 cm−1 is the characteristic signature of graphene and is observed only in GO having stable layered structure. The ID/IG ratio for GO is 1.00 which increases to 1.12 with the addition of tin precursor without any reductant and this indicates the reduction of the sp2 bonded C atoms after addition of reductant. The intensity ratio (ID/IG) increased from 1.01 to 1.04 after annealing indicating a decrease in the average size of the sp2 domains due to the annealing induced reduction of the rGO.
Changes in revised manuscript
Line 114-122,
G band (graphitic carbon),… induced reduction of the rGO[20, 21].
Comment 6. Comments on the Quality of English Language
The writing style, grammar and language usage should be checked.
Response 6. We have done a serious recheck of the full manuscript and we hope that the revised manuscript is suitable for publication.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors prepared crystalline SiO2 quantum dots over rGO composite for lithium ion batteries. I cannot find enough statements and evidence for the above clarifications in the present paper version. There are missing the content of SiO2 quantum dots in the composite, as well as the cell assembly process. Additionally, the authors should provide high quality of images in the paper.
Author Response
Response to the Reviewer 2
Many thanks to all the reviewers for reviewing our manuscript and the constructive comments. These comments were very useful improve the quality of our manuscript. We have carefully read all the comments and made necessary modifications marked in red and underlined in the manuscript. Following is the point-to-point response to the reviewers’ comments.
Open Review
(x) I would not like to sign my review report
( ) I would like to sign my review report
Quality of English Language
(x) The quality of English does not limit my understanding of the research.
( ) The English could be improved to more clearly express the research.
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Yes |
Can be improved |
Must be improved |
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Does the introduction provide sufficient background and include all relevant references? |
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Is the research design appropriate? |
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Are the methods adequately described? |
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Are the results clearly presented? |
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Are the conclusions supported by the results? |
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Comments and Suggestions for Authors
The authors prepared crystalline SiO2 quantum dots over rGO composite for lithium ion batteries. I cannot find enough statements and evidence for the above clarifications in the present paper version. There are missing the content of SiO2 quantum dots in the composite, as well as the cell assembly process. Additionally, the authors should provide high quality of images in the paper.
Response. Many thanks to the reviewer for the constructive comments. We are sorry for any confusion. We have done a series of XRD, TEM analysis to confirm the formation of the SiO2 quantum dots over rGO as shown in Figure 1 a-f. We have added the cell assembly process in the revised manuscript. We hope that the revised manuscript is suitable for publication. Thank you very much.
Reviewer 3 Report
Comments and Suggestions for AuthorsIn this manuscript, crystalline SiO2 quantum dots (QDs), ranging from 3-5 nm, were synthesized within the layers of reduced graphene oxide (rGO) via a solution-based chemical growth process at a relatively low temperature (100℃). The composites demonstrate promising electrochemical performance for lithium-ion storage. This manuscript meets the standard of C-Journal of Carbon Research pending major revisions.
1. In the field of lithium-ion batteries, it is recommended to incorporate recent works, such as Energy Mater., 2024;4:400064 and Advanced Functional Materials, 2024;2414714.
2. Please provide additional details regarding the electrolyte, separator, and electrode preparation used in the electrochemical tests.
3. There appear to be additional physical phases present in Figure 2a, aside from SiO2. Please elaborate.
4. Cyclic voltammetry, a widely used electrochemical technique, provides valuable information. It is recommended to include this technique in the study.
5. It is recommended to include the electrochemical performance of pure SiOx (without rGO) to better highlight the advantages of the SiOx/rGO composites.
6. The authors mention, “The intensity ratio (ID/IG) increased from 1.01 to 1.04 after annealing, indicating an increase in amorphous carbon content and consequently the electronic conductivity of the composite.” Please clarify why a higher ID/IG ratio correlates with increased electronic conductivity.
7. SiOx is widely studied as an anode material for lithium-ion batteries. Please include a comparison of the electrochemical performance of this work with others to emphasize the superiority of SiOx/rGO.
Comments on the Quality of English LanguageIt can be polished.
Author Response
Response to the Reviewer 3
Many thanks to all the reviewers for reviewing our manuscript and the constructive comments. These comments were very useful improve the quality of our manuscript. We have carefully read all the comments and made necessary modifications marked in red and underlined in the manuscript. Following is the point-to-point response to the reviewers’ comments.
Open Review
(x) I would not like to sign my review report
( ) I would like to sign my review report
Quality of English Language
( ) The quality of English does not limit my understanding of the research.
(x) The English could be improved to more clearly express the research.
|
Yes |
Can be improved |
Must be improved |
Not applicable |
|
|
Does the introduction provide sufficient background and include all relevant references? |
( ) |
(x) |
( ) |
( ) |
|
Is the research design appropriate? |
( ) |
(x) |
( ) |
( ) |
|
Are the methods adequately described? |
( ) |
(x) |
( ) |
( ) |
|
Are the results clearly presented? |
( ) |
(x) |
( ) |
( ) |
|
Are the conclusions supported by the results? |
( ) |
(x) |
( ) |
( ) |
Comments and Suggestions for Authors
In this manuscript, crystalline SiO2 quantum dots (QDs), ranging from 3-5 nm, were synthesized within the layers of reduced graphene oxide (rGO) via a solution-based chemical growth process at a relatively low temperature (100℃). The composites demonstrate promising electrochemical performance for lithium-ion storage. This manuscript meets the standard of C-Journal of Carbon Research pending major revisions.
Comment 1. In the field of lithium-ion batteries, it is recommended to incorporate recent works, such as Energy Mater., 2024;4:400064 and Advanced Functional Materials, 2024;2414714.
Response 1. Thank you for this very important suggestions. I could find the first reference Energy Mater., 2024;4:400064 and cited the reference in the text as reference 2. I did not find the other reference from the website.
Changes in revised manuscript:
New reference added as reference 2.
Line 223-225, A. Nelson, S. Mateti, Y. Chen, N. Sharma, Q. Han, M.M. Rahman, Creating value added nano silicon anodes from end-of-life photovoltaic modules: recovery, nano structuring, and the impact of ball milling and binder on its electrochemical performance, Energy Materials, 4 (2024) 400064.
Comment 2. Please provide additional details regarding the electrolyte, separator, and electrode preparation used in the electrochemical tests.
Response 2. Many thanks for this valuable comment. We have added the details about the cell fabrication in the experimental procedure.
The slurry was prepared by combining the solid components as 65 wt. % of active materials, 20 wt. % Super P (MMM Carbon, Belgium), 9 wt.% poly (acrylic acid) (PAA, Sigma-Aldrich Co.), 3.5 wt. % styrene butadiene rubber (SBR, Zeon Co.), and 2.5 wt. % carboxymethyl cellulose (CMC, Sigma-Aldrich Co.). Mixing was performed in a planetary mixer (G-Mixer 400S, Gold Max Applied Materials Co.). The electrodes were prepared by casting the slurry onto a sheet of copper foil (Nippon Foil Co.) followed by drying in an oven at 90°C for 1 h. The composite anode was stored in a glove box (with oxygen and humidity maintained below 10 ppm) for more than 24 h before electrochemical testing. For the cycle test, the cells underwent galvanostatic charge/discharge tests between 0.002 and 1.5 V versus Li+/Li using a multichannel battery testing system (AcuTech Systems BAT-750B).
Changes in the revised manuscript:
Line 90-100,
The slurry was prepared …sting system (AcuTech Systems BAT-750B).
Comment 3. There appear to be additional physical phases present in Figure 2a, aside from SiO2. Please elaborate.
Response 3. Many thanks for this important comment. We agree with the reviewer comment about the presence of additional phases. However, it is difficult to identify all of them due to very low intensity. However, majority of the peaks in the XRD patern belong to SiO2 quantum dots.
Comment 4. Cyclic voltammetry, a widely used electrochemical technique, provides valuable information. It is recommended to include this technique in the study.
Response 4.Thank you very much for this very good comment. We strongly agree that cyclic voltammetry is a very important analysis to understand various chemical reactions taking place during the charge/discharge process. However, this experiment is time consuming which involves the composite preparation, battery fabrication and cyclic voltammetry analysis. So, we will not be able to complete it within this time frame. We are sorry for this.
Comment 5. It is recommended to include the electrochemical performance of pure SiOx (without rGO) to better highlight the advantages of the SiOx/rGO composites.
Response 5. Many thank you for this very good comment. The as obtained SiO or SiOx usually does not show great electctrochemical properties (Ref 1, Ref 2) without any special modification. We have prepared SiOx and the electrochemical data do not show good electrochemical properties as shown below. The specific capacity after 100 charge/discharge cycles is below 100 mAhg-1.
Ref 1. Yoon Hwa, Cheol-Min Park, Hun-Joon Sohn,*Modified SiO as a high performance anode for Li-ion batteries, Journal of Power Sources 222 (2013) 129e134
Ref 2. Cheol-Min Park, Woongchul Choi, Yoon Hwa, Jae-Hun Kim, Goojin Jeong and Hun-Joon Sohn*, Characterizations and electrochemical behaviors of disproportionated SiO, and its composite for rechargeable Li-ion batteries, J. Mater. Chem., 2010, 20, 4854–4860
Comment 6. The authors mention, “The intensity ratio (ID/IG) increased from 1.01 to 1.04 after annealing, indicating an increase in amorphous carbon content and consequently the electronic conductivity of the composite.” Please clarify why a higher ID/IG ratio correlates with increased electronic conductivity.
Response 6. Many thanks to the reviewer for such insightful comment. We are sorry for the confusion and we have removed the relationship of the Id/Ig ratio with electronic conductivity in the revised manuscript.
The Raman spectra in GO or rGO usually show three peaks corresponding to D band (1342 cm−1), G band (1594.8 cm−1) and 2D band (2700 cm−1) respectively. The D band is usually a defect peak within the carbon structure that exhibit sp3 bonded carbon atoms, whereas the G band is sp2 bonded carbon atoms in the honey-comb lattice. The 2D band at 2700 cm−1 is the characteristic signature of graphene and is observed only in GO having stable layered structure. The ID/IG ratio for GO is 1.00 which increases to 1.12 with the addition of tin precursor without any reductant and this indicates the reduction of the sp2 bonded C atoms after addition of reductant. The intensity ratio (ID/IG) increased from 1.01 to 1.04 after annealing indicating a decrease in the average size of the sp2 domains due to the annealing induced reduction of the rGO [Ref 1, Ref 2]
Ref 1. Junfei Liang, Wei Wei, Da Zhong, Qinglin Yang, Lidong Li, and Lin Guo, One-Step In situ Synthesis of SnO2/Graphene Nanocomposites and Its Application As an Anode Material for Li-Ion Batteries, ACS Appl. Mater. Interfaces 2012, 4, 454−459
Ref 2. Yueming Li, Xiaojun Lv, Jin Lu, and Jinghong Li, Preparation of SnO2-Nanocrystal/Graphene-Nanosheets Composites and Their Lithium Storage Ability, J. Phys. Chem. C 2010, 114, 21770–21774
Comment 7. SiOx is widely studied as an anode material for lithium-ion batteries. Please include a comparison of the electrochemical performance of this work with others to emphasize the superiority of SiOx/rGO.
Response 7. Many thanks for this very important comment. A brief revision was done in the manuscript and we have added the following.
Unlike in earlier literature [22-24], where the specific capacity of milled SiO droped drastically with the cycle numbers, the capacity of the SiOx/rGO nanocomposite is very stable after several charge discharge cycles.
Comments on the Quality of English Language
It can be polished.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe paper has been thoroughly revised to improve scientific validity and readability. Agreed to be published in present form.
Author Response
Comment 1: The paper has been thoroughly revised to improve scientific validity and readability. Agreed to be published in present form.
Response 1: Thank you very much for accepting our manuscript.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe author should further elaborate its innovation in the research background.
Comments on the Quality of English LanguageThe english should be improved.
Author Response
Comment 1: The author should further elaborate its innovation in the research background.
Response 1: Many thanks for such a good comment. Growth of crystalline SiO2 quantum dots over reduced graphene oxide (rGO) might be one of the preferable choice to enhance active surface area, electrical conductivity and flexibility to accommodate the volume change and achieve high capacity. Besides, the synthesis of SiO2 quantum dots directly from the Si precursor having direct Si-O bond by using a low temperature and bottom up approach might be economic and energy efficient method as compared to high temperature processes and is worth investigating. For example, Si starting materials such as APTMS (3-(aminopropyl)-trimethoxysilane) has a direct Si-O bond in the complex which makes it a very suitable starting precursor material for the production of SiO2. Therefore, we developed a solution mode low temperature (100°C) growth process for the production of SiO2-rGO nanocomposite where crystallization of SiO2 from Si precursor and chemical reduction of GO to rGO take place at the same time.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe other reference can be found at: https://doi.org/10.1002/adfm.202414714. It can be added during the proof stage.
Author Response
Comment 1: The other reference can be found at: https://doi.org/10.1002/adfm.202414714. It can be added during the proof stage.
Response 1: Thank you very much for providing the correct web link for the above paper. I have added this in the manuscript as
[3] G. Xie, X. Tan, Z. Shi, Y. Peng, Y. Ma, Y. Zhong, F. Wang, J. He, Z. Zhu, X.B. Cheng, SiOx Based Anodes for Advanced Li‐Ion Batteries: Recent Progress and Perspectives, Adv Funct Mater, (2024) 2414714.
Hope that our manuscript is now suitable for publication.
