In Situ Gas-Phase Polymerization of Polypyrrole-Coated Lithium-Rich Nanotubes for High-Performance Lithium-Ion Batteries
, Beibei Sun 2, Xinchang Wang 1,*, Junmin Xu 1, Liwei Zhang 2,* and Jipeng Cheng 3,*
Round 1
Reviewer 1 Report
The dwindling supply of conventional fossil fuels for energy generation necessitates the search for alternative sources like solar energy and wind energy, with the development of storage devices. Therefore, the implementation of advanced Li-ion batteries seems mandatory. With the use of traditional electrode material, performance metrics is being limited, and hence the authors reported modification of the LMNCO electrode by using conducting polymers such as polypyrrole. Among the conducting polymers, polypyrrole exhibits excellent environmental stability, potentially low cost, higher conductivity, and accessible synthesis. Therefore, the reported work and the materials are novel. The manuscript is written OK but the main concern of this paper and the areas that require clarification are given below.
1. Line 39 what is LLO?
2. The part of line 39 and lines 41-42 is unclear. Please rewrite this sentence.
3. Line 49 “facilities” should read “facilitate” They have different meanings.
4. Line 50, not “destroy” but “deteriorate”
5. Line 56 – 58; authors need to be a bit mindful in claiming this. Not only PPY but biopolymer Chitosan has also been widely used for improving performance metrics. Ramya Ramkumar et al have widely published work on biopolymers. Please amend accordingly.
6. Before wrapping up the intro, the salient features of PPY and its properties can be detailed.
7. Why there is no charge/discharge profiles in the manuscript?
8. How to justify that the presence of PPY delayed the O2 release from the electrode?
9. In LMNCO electrode, does all the TM cations taken part in redox reaction?
10. Why in the CV profiles (Figs 4a-b) there is no distinct redox peaks for Ni, Mn, and CO? The key paper https://doi.org/10.1149/1.3561764 explaining the role of Co and Ni can be included.
11. Please provide the C-rate for cyclability experiments.
12. Figure 5b requires more explanation.
13. In Figure 6a, is the capacity shown on Y-axis (discharge/charge capacity?) What is the mass of the electrode?
14. Either in XRD, XPS or SEM, can one evidence the presence of PPY in the sample?
15. Section 6; line 228 “what is destroyed and collapse”?
16. Line 230, an increment from 202 to 209 very marginal, right? Please confirm.
Author Response
The authors thank reviewers for your comments and suggestions. These comments are all valuable and very helpful for revising and improving our work, as well as the important guiding significance to our research. We have gone through the reviewers’ comments carefully and have made revisions. The responses to the reviewers’ comments point by point are presented as below.
Reviewer 1
Comments and Suggestions for Authors
The dwindling supply of conventional fossil fuels for energy generation necessitates the search for alternative sources like solar energy and wind energy, with the development of storage devices. Therefore, the implementation of advanced Li-ion batteries seems mandatory. With the use of traditional electrode material, performance metrics is being limited, and hence the authors reported modification of the LMNCO electrode by using conducting polymers such as polypyrrole. Among the conducting polymers, polypyrrole exhibits excellent environmental stability, potentially low cost, higher conductivity, and accessible synthesis. Therefore, the reported work and the materials are novel. The manuscript is written OK but the main concern of this paper and the areas that require clarification are given below.
Line 39 what is LLO?
Response: Thank you for your advice. The LLOs materials are Layered Li-rich Manganese Oxides materials, with a chemical formula (xLi2MnO3·(1-x)LiMO2, M = Mn, Ni, Co...). (Line 30)
The part of line 39 and lines 41-42 is unclear. Please rewrite this sentence.
Response: Thank you for your advice for pointing out some problems in our manuscript. We have marked the revised content in red font in the text.
This sentence is modified as follows:
Moreover, the practical application of materials is hindered due to the cyclic phase transition and the low cycle performance and low rate capacity of low electronic/ ionic conductivity materials.
Line 49 “facilities” should read “facilitate” They have different meanings.
Response: The manuscript has been revised.
Line 50, not “destroy” but “deteriorate”
Response: The manuscript has been revised.
Line 56-58; authors need to be a bit mindful in claiming this. Not only PPY but biopolymer Chitosan has also been widely used for improving performance metrics. Ramya Ramkumar et al have widely published work on biopolymers. Please amend accordingly.
Response: The manuscript has been revised.
Recently, organic polymers such as polypyrrole (PPy) and biopolymer chitosan (CHIT) have been reported to improve the rate performance and the cyclic stability of LiMn1/3Co1/3Ni1/3O2 [25] and CoMoO4 [26].
Before wrapping up the intro, the salient features of PPY and its properties can be detailed.
Response: Thank you for your advice. We have added the feature of PPY and marked the revised content in red font in the text.
Why there is no charge/discharge profiles in the manuscript?
Response: In Figure 5b and 5c, we show the charge/discharge capacity data in the form of differential capacity curves, which can show more redox peaks and display more rich content.
How to justify that the presence of PPY delayed the O2 release from the electrode?
Response: Normally, the LiMn2O3 component of lithium rich cathode materials will release oxygen during the first cycle of charging. It can be seen that the peak at 4.5V is the oxidation peak of LiMn2O3 in Fig 4, and the oxidation peak of PLMNO sample is obviously lower than that of LMNCO sample, which infers that PPY delayed the process of oxygen release.
In LMNCO electrode, does all the TM cations taken part in redox reaction?
Response: During the first cycle of charging and discharging, all TM cations participate in the redox reaction.
Why in the CV profiles (Figs 4a-b) there is no distinct redox peaks for Ni, Mn, and CO? The key paper https://doi.org/10.1149/1.3561764 explaining the role of Co and Ni can be included.
Response: Thank you for your advice, we have cited the paper that you commend.
Please provide the C-rate for cyclability experiments.
Response: The cyclability experiment is 1 C (250 mAh g-1). The data is available in the text.
In Figure 6a, is the capacity shown on Y-axis (discharge/charge capacity?) What is the mass of the electrode?
Response: The capacity of Y-axis in Figure 6a is the discharge capacity. The mass of the electrode is about 1.5 mg.
Either in XRD, XPS or SEM, can one evidence the presence of PPY in the sample?
Response: Due to the extremely low content of PPy, it cannot determine whether the samples contain the PPy components through XRD, XPS and SEM measurements. PPy is determined by the HRTEM test in this experiment.
Section 6; line 228 “what is destroyed and collapse”?
Response: During the charge and discharge cycle, the LMNCO tubular structure will be destroyed and collapse. The manuscript has been revised.
Line 230, an increment from 202 to 209 very marginal, right? Please confirm.
Response: Thank you for your advice. We have marked the revised content in red font in the text.
Author Response File: 
Author Response.docx
Reviewer 2 Report
1. information in the summary of this study in the introduction.
2. I would like to confirm with the author about heating the sample at 800oC under air atmosphere condition because under this condition PAN will be completely decomposed and no sample will be obtained after calcination. (In many cases will be fired under Argon or N2).
3. Please clearly caption the mapping image. (Figure 3)
4. What is the meaning of 1st, 2nd, 3rd in figure 4?
Authors should clearly divide between material morphology and material characteristic. If not, please explain more clearly in this section. The author This manuscript describes the successful synthesis of conductive polypyrrole (PPy) nanotubes coated with Manganese-rich Lithium as cathode. The morphological structure has been determined and the ability to determine the discharge capacity of Ppy-coated LMNCO cells is enhanced. I have not seen the breakthrough and novelty in this research. The authors claim that the rate of capacity is also improved at high current densities due to higher electron and ionic conductivity, but compared with other studies it is not really much of an improvement. Besides, the author has not clearly demonstrated in this manuscript. In my opinion, this manuscript needs to have major revision and I do not suggest to be published in this journal, the following reasons:
5. The author should include more only describes and has not given specific evidence for the successful synthesis of materials.
6. The author should restate the XRD, too sketchy.
7. FE-SEM images should be mentioned in the morphology section and the author should give clearer images.
In my opinion, I haven’t recommended this manuscript to be published in this journal.
Author Response
The authors thank reviewers for your comments and suggestions. These comments are all valuable and very helpful for revising and improving our work, as well as the important guiding significance to our research. We have gone through the reviewers’ comments carefully and have made revisions. The responses to the reviewers’ comments point by point are presented as below.
Reviewer 2
- I would like to confirm with the author about heating the sample at 800oC under air atmosphere condition because under this condition PAN will be completely decomposed and no sample will be obtained after calcination. (In many cases will be fired under Argon or N2).
Response: In the experiment, PAN was used to prepare composite nanofibers as polymer spinning agent and obtain LMNCO tube nanofibers after calcination. The purpose of the experiment was not to obtain PAN or PAN calcination to obtain the carbon materials.
- Please clearly caption the mapping image. (Figure 3)
Response: Thank you for your advice. However, the campus has been closed due to the COVID-19. We are very sorry that we cannot be able to add the mapping image as required by the reviewers.
- What is the meaning of 1st, 2nd, 3rd in figure 4?
Response: The 1st, 2nd and 3rd cycles in Figure 4 are the first cycle, the second cycle and the third cycle of Cyclic voltammograms (CVs) tests respectively.
Authors should clearly divide between material morphology and material characteristic. If not, please explain more clearly in this section. The author This manuscript describes the successful synthesis of conductive polypyrrole (PPy) nanotubes coated with Manganese-rich Lithium as cathode. The morphological structure has been determined and the ability to determine the discharge capacity of Ppy-coated LMNCO cells is enhanced. I have not seen the breakthrough and novelty in this research. The authors claim that the rate of capacity is also improved at high current densities due to higher electron and ionic conductivity, but compared with other studies it is not really much of an improvement. Besides, the author has not clearly demonstrated in this manuscript. In my opinion, this manuscript needs to have major revision and I do not suggest to be published in this journal, the following reasons:
- The author should include more only describes and has not given specific evidence for the successful synthesis of materials.
Response: Thank you for your advice. Because the PPy coating is very thin, the low content of PPy cannot be measured by XRD, SEM and XPS. In this measurement, we mainly analyzed the presence and the thickness of PPy by HRTEM measurement. It can be found that the surface of LMNCO nanofibers was covered with a thin layer of PPy, and the thickness of PPy is about 2 nm.
- The author should restate the XRD, too sketchy.
Response: According to your comments, we have modified the XRD section and marked the revised content in red font in the text.
Fig. 2a shows the XRD patterns of LMNCO and P-LMNCO samples. Apparently, both of the patterns have fundamental diffraction peaks, which are ascribed to the layered component of hexagonal α-NaFeO2 structure (space group: R3m). Additionally, no PPy peaks are observed in the pattern of P-LMNCO sample, which may be due to PPy being an amorphous structure with low content in composite materials. From Fig. 2a, the small peaks of all samples from 20 to 23° belong to the superlattice diffraction of the monoclinic Li2MnO3 phase (space group: C2/m) [10,28]. Moreover, the diffraction peaks of both samples are not obvious change, indicating that PPy coating does change the crystal structure of LMNCO nanofibers.
- FE-SEM images should be mentioned in the morphology section and the author should give clearer images.
Response: Thank you for your advice. However, the raw data of this experiment was kept in the laboratory computer, and the campus has been closed due to the COVID-19. We are very sorry that we are not able to process SEM images as required by the reviewer.
Author Response File: Author Response.docx
Reviewer 3 Report
The Yangwen and coworkers detail a new method to prepare stable and high capacity lithium-based cathode via coating LMNCO with PPy. In particular, the authors demonstrate the electrochemical performance of the new cathode and propose a possible mechanism for the enhancement of stability. The data is generally clearly and concisely presented. The paper is well organized. I believe the work is well suited for Surfaces. A couple minor points for consideration on revision are listed below.
1. The author mention “… lithium can extracted from the Li2MnO3 component leads to a high reversible capacity …”. I believe the author want to say “lithium can be extracted”
I encourage the authors to take one more pass of the manuscript to avoid this kind of issues.
2. In 3.1, the author mention “Both of the patterns correspond to hexagonal α-NaFeO2 structure”. I’d like to ask if the author can provide standard XRD pattern of hexagonal α-NaFeO2 structure in the graph Fig. 2a.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The revised manuscript is OK to publish.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 2 Report
The author's answer to this paper did not fully explain my question.
So I propose this paper's review as a rejection once again.
Author Response
Response to the reviewers’ comments
The authors thank reviewers for your comments and suggestions. These comments are all valuable and very helpful for revising and improving our work, as well as the important guiding significance to our research. We have gone through the reviewers’ comments carefully and have made revisions. The responses to the reviewers’ comments point by point are presented as below.
Reviewer 2
- I would like to confirm with the author about heating the sample at 800oC under air atmosphere condition because under this condition PAN will be completely decomposed and no sample will be obtained after calcination. (In many cases will be fired under Argon or N2).
Response: In the experiment, PAN was used to prepare composite nanofibers as polymer spinning agent and obtain LMNCO tube nanofibers after calcination. The purpose of the experiment was not to obtain PAN or PAN calcination to obtain the carbon materials.
- Please clearly caption the mapping image. (Figure 3)
Response: According to your comments, we have added the caption of the mapping images (Fig. 3 e-h) and marked the revised content in red font in the text.
- What is the meaning of 1st, 2nd, 3rd in figure 4?
Response: The 1st, 2nd and 3rd cycles in Figure 4 are the first cycle, the second cycle and the third cycle of Cyclic voltammograms (CVs) tests respectively.
Authors should clearly divide between material morphology and material characteristic. If not, please explain more clearly in this section. The author This manuscript describes the successful synthesis of conductive polypyrrole (PPy) nanotubes coated with Manganese-rich Lithium as cathode. The morphological structure has been determined and the ability to determine the discharge capacity of Ppy-coated LMNCO cells is enhanced. I have not seen the breakthrough and novelty in this research. The authors claim that the rate of capacity is also improved at high current densities due to higher electron and ionic conductivity, but compared with other studies it is not really much of an improvement. Besides, the author has not clearly demonstrated in this manuscript. In my opinion, this manuscript needs to have major revision and I do not suggest to be published in this journal, the following reasons:
- The author should include more only describes and has not given specific evidence for the successful synthesis of materials.
Response: Thank you for your advice. Because the PPy coating is very thin, the low content of PPy cannot be measured by XRD, SEM and XPS. In this measurement, we mainly analyzed the presence and the thickness of PPy by HRTEM measurement. It can be found that the surface of LMNCO nanofibers was covered with a thin layer of PPy, and the thickness of PPy is about 2 nm.
- The author should restate the XRD, too sketchy.
Response: According to your comments, we have modified the XRD section and marked the revised content in red font in the text.
Fig. 2a shows the XRD patterns of LMNCO and P-LMNCO samples. Apparently, both of the patterns have fundamental diffraction peaks, which are ascribed to the layered component of hexagonal α-NaFeO2 structure (space group: R3m). Additionally, no PPy peaks are observed in the pattern of P-LMNCO sample, which may be due to PPy being an amorphous structure with low content in composite materials. From Fig. 2a, the small peaks of all samples from 20 to 23° belong to the superlattice diffraction of the monoclinic Li2MnO3 phase (space group: C2/m) [10,28]. Moreover, the diffraction peaks of both samples are not obvious change, indicating that PPy coating does change the crystal structure of LMNCO nanofibers.
- FE-SEM images should be mentioned in the morphology section and the author should give clearer images.
Response: According to your comments, we have provided the clearer images of FE-SEM (Figure 5 d,e) and TEM (Figure 3a-d). Because the hollow structure of the nanofiber cannot be judged by FE-SEM test, so we used TEM measurement to test the morphology of LMNCO nanomaterials.
Author Response File: Author Response.docx
Round 3
Reviewer 2 Report
Through the kind and adequate responses of authors, the doubts are dispelled and the errors of the manuscript are correctly revised. I think the authors provide quite reasonable changes.
Thus, I gladly recommend that this manuscript might be suitable to publish to this journal.
