Scalable Fabrication of Si-Graphene Composite as Anode for Li-ion Batteries
, Weibing Xing 3, Tim Lin 2,5 and Haiping Hong 4,*
Round 1
Reviewer 1 Report
1. To show the advance of the as-prepared Si-graphene anode and the creativity of this work, the authors should compare the performances of Si-graphene with other Si-based anode reported in literatures recently.
2. The authors claim that the improved cycling performance of the Si-graphene anode is attributed to the graphene structure that accommodates the volume expansion of the Si nanoparticles. But, this conclusion is not supported by experiments. TEM and HRTEM images of the anodes before and after cycling should be provided to support the conclusion.
3. Why is the coulombic efficiency of the cells greater than 100%?
4. The rate capabilities of the anodes should be compared.
5. The actual weight ratio of Si and graphene should be tested.
6. The authors should provide the Raman spectrum of Si nanoparticles.
7. Some typos and mistakes should be corrected. Such as “S-graphene” ( page 7, line 246).
Author Response
Reviewer #1
- To show the advance of the as-prepared Si-graphene anode and the creativity of this work, the authors should compare the performances of Si-graphene with other Si-based anode reported in literatures recently.
Answer: Thanks for the comment. Table 2 (in the revised manuscript) has been added to compare the results of this work with other Si/graphene related anodes reported in the literature.
- The authors claim that the improved cycling performance of the Si-graphene anode is attributed to the graphene structure that accommodates the volume expansion of the Si nanoparticles. But, this conclusion is not supported by experiments. TEM and HRTEM images of the anodes before and after cycling should be provided to support the conclusion.
Answer: Thanks for the comment. The authors agree with the reviewer that TEM is an appropriate tool to observe the volume expansion of Si nanoparticles after cycling test. However, the TEM instrument is not available at this moment. It is well known in the research community that the main problem of Si anode is its volume expansion and graphene structure can tolerate the volume change of Si nanoparticle.
- Why is the coulombic efficiency of the cells greater than 100%?
Answer: Thanks for the comment. Actually, the reason of the coulombic efficiency being greater than 100% has been explained in the manuscript (page 8 line 286, clean version). The coulombic efficiency being greater than 100% is mainly attributed to the uncontrolled temperature during the test. A relatively higher room temperature during the discharge process would deliver a discharge capacity that is higher than the charge capacity, resulting in the columbic efficiency going beyond 100%.
- The rate capabilities of the anodes should be compared.
Answer: Thanks for the comment. The capacities of the Si-graphene electrode at different current rates (0.05C, 0.1C, and 0.5C) have been compared in the manuscript (page 7 line 250, clean version).
- The actual weight ratio of Si and graphene should be tested.
Answer: Thanks for the comment. In the sample preparation procedure, Si nanoparticle and graphene nanosheet were added in a ratio of 1:1 by weight and the excess surfactant was washed in the filtration process. The EDS results indicated the actual weight ratio agrees with the theoretical ratio.
- The authors should provide the Raman spectrum of Si nanoparticles.
Answer: Thanks for the comment. The Raman spectrum of Si nanoparticles have been provided in the revised figure 4b.
- Some typos and mistakes should be corrected. Such as “S-graphene” ( page 7, line 246).
Answer: Thanks for catching that. The typo has been corrected and the whole manuscript has been checked.
Reviewer 2 Report
In the current manuscript, Lou et al. have presented a scalable method to prepare Si-graphene nanocomposite. They characterized the material using appropriate techniques and evaluated it as a potential anode for Li-ion batteries. Overall, the results support the discussion and the manuscript is well-written. Hence, I recommend the acceptance of this work in its current form.
Author Response
Answer: The authors thank the reviewer for the comment.
Reviewer 3 Report
Dear Editor
This study investigated the fabrication of Si-graphene nanocomposite as anode material for Li-ion batteries.
1. Introduction needs new references from the Applied Sciences Journal
2. Table.1 and the comparison of results of this work with other reports move to the discussion section.
3. The specific charge and discharge capacities were calculated based on the total weight of the Si-graphene composite used to fabricate the half cell….The specific capacity should be defined with a formulation.
4. As expected, the Si-based coin cell shows a much higher specific capacity than the S-graphene composite coin cell for the initial cycle….” S-graphene” should be corrected.
5. Therefore, the columbic efficiencies of the first charge/discharge cycle were calculated to be 84.7% at 0.05C, 100.5% at 0.1C, and 118.5% at 0.5C… more explain in the manuscript how measured the columbic efficiencies.
6. The discussion section needs to be improved
7. Calculate the energy density of the battery and add it to the manuscript
8. Graphene and reduced graphene oxide (rGO) have been extensively investigated to synthesize composite anode materials in various ways to explore better electrochemical performance [22,23]… Graphene is also used in different energy storage supercapacitors such as the following references: High-performance supercapacitors based on the carbon nanotubes, graphene and graphite nanoparticles electrodes, Flexible graphene supercapacitor based on the PVA electrolyte and BaTiO 3/PEDOT: PSS composite separator
Author Response
Reviewer #3
Dear Editor
This study investigated the fabrication of Si-graphene nanocomposite as anode material for Li-ion batteries.
- Introduction needs new references from the Applied Sciences Journal
Answer: Thanks for the comment. References from the Applied Sciences journal have been cited in the introduction section (reference 3, 4, and 5).
- Table 1 and the comparison of results of this work with other reports move to the discussion section.
Answer: Thanks for the comment. Table 1 and the comparison of results of this work with other reports has been moved to the discussion section.
- The specific charge and discharge capacities were calculated based on the total weight of the Si-graphene composite used to fabricate the half cell….The specific capacity should be defined with a formulation.
Answer: Thanks for the comment. For the coin cell with Si-graphene electrode, the specific charge and discharge capacities were calculated based on the total mass of Si-graphene in the cell (e.g. the specific discharge capacity = discharge capacity/total weight of Si-graphene in the cell). The electrode was weighed before the cell assembly. After deducting the weight of the corresponding current collector, the Si-graphene weight ratio (80wt%) is applied to calculate the weight of the actual active material in the cell.
- As expected, the Si-based coin cell shows a much higher specific capacity than the S-graphene composite coin cell for the initial cycle….” S-graphene” should be corrected.
Answer: Thanks for catching that. The typo has been corrected.
- Therefore, the columbic efficiencies of the first charge/discharge cycle were calculated to be 84.7% at 0.05C, 100.5% at 0.1C, and 118.5% at 0.5C… more explain in the manuscript how measured the columbic efficiencies.
Answer: Thanks for the comment. The coulombic efficiency (CE) was calculated by the formula: CE = charge capacity/discharge capacity. The text has been revised in the manuscript (page 7 line 252, clean version).
- The discussion section needs to be improved
Answer: Thanks for the comment. The discussion section has been improved.
- Calculate the energy density of the battery and add it to the manuscript
Answer: Thanks for the comment. Normally for half coin cell test, people calculate the energy density of Si-based anode or the active material. Therefore, in this work, the energy density of the Si-graphene active material at 0.1C is calculated to be 522.8 Wh/Kg.
Energy density =CV,
Where C is specific discharge capacity, V is nominal voltage (voltage @50% state of charge).
Therefore, the energy density = 1307 mAh g-1 × 0.4 V = 522.8 Wh/Kg).
- Graphene and reduced graphene oxide (rGO) have been extensively investigated to synthesize composite anode materials in various ways to explore better electrochemical performance [22,23]… Graphene is also used in different energy storage supercapacitors such as the following references: High-performance supercapacitors based on the carbon nanotubes, graphene and graphite nanoparticles electrodes, Flexible graphene supercapacitor based on the PVA electrolyte and BaTiO 3/PEDOT: PSS composite separator
Answer: Thanks for the comment. The authors completely agree that graphene is also used as electrode materials in supercapacitors. The mentioned references have been cited in the revised manuscript.
Round 2
Reviewer 1 Report
Accept
Reviewer 3 Report
Dear Editor
The manuscript well has been revised.
