S and P Dual-Doped Carbon Nanospheres as Anode Material for High Rate Performance Sodium-Ion Batteries

Round 1

Reviewer 1 Report

I accurately reviewed the manuscript with the number of «applsci-1492881» Title: S and P dual-doped carbon nanospheres as anode material for high-rate performance sodium-ion batteries. Submitted to Applied Sciences. The synthesis of such S and P co-doped carbon is a common work and their electrochemical properties are also at the normal level. Particularly, it seems that manuscript has been prepared with a minimal accuracy. There are remarkable errors in the work. Therefore, I cannot recommend the publication on Applied Sciences. Below are my detailed comments and questions.

• I am not agree with this sentence: “From the SEM image (Fig. 2), it was confirmed that the particles of SP/C were ball-shaped, similar to carbon black, and were connected to each other.” This conclusion cannot be drawn from the figure, high-resolution SEM and TEM photos need to be added.
• Figure 3b shows that the specific surface area of SP/C material is very small, but the author's test results show up to 92.06 m² g^-1, I think the data is wrong.
• Figure 5b shows that the material has a very low Coulomb Efficiency at high current densities, which needs to be given an accurate interpretation.
• Figure 6 shows that the contribution of the pseudocapacitor hardly changes as the sweep speed increases, I think this result needs further verification.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The authors synthesized S and P co-doped carbon material (SP/C) using a simple and one-step plasma-in-liquid process and assembled it as anode material in the sodium-ion half-cell. Benefiting from the abundant macropores in SP/C, a remarkable cycling life of 3,000 cycles at a high current density of 10 A g^-1 with a high reversible capacity over 125 mAh g^-1 was achieved. The investigations on reaction kinetics showed that most of the capacity could be attributed to a fast capacitive process. Overall, this manuscript is well-written with sufficient findings. I would recommend the publication in Applied Sciences after minor revision. Here are some suggestions:

1. As the author mentioned, SP/C is a nanomaterial; it is better to include some high magnification SEM or TEM to demonstrate the diameter and morphology of SP/C.
2. It is also suggested to add the XRD pattern of undoped carbon in Figure 3 to check the structural changes caused by S and P doping.
3. Figure 5: Please provide the Coulombic efficiency as well in Figure 5.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

In this paper, the authors present the synthesis and characterisation of  S and P dual-doped carbon nanospheres using plasma-in-liquid process; the synthetized is material could be use as anode material for high-rate performance sodium-ion batteries.

The authors state that the synthetized S and P co-doped carbon material exhibits high initial coulombic efficiency and excellent reversible capacity with a long cycling life.

The characterization of the synthesized material was performed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD). Specific surface areas were evaluated using the Brunauer-Emmett-Teller (BET) method. Pore sizes were determined using the Barrett Joyner–Halenda (BJH) and micropore analysis (MP).

General comments

• Novelty or purpose of the study is not stated clearly. Please, clearly state the novelty of the presented paper at the end of the introduction part; reformulate the objective of the paper and indicate all the characterization methods of the synthetized material.
• The manuscript contains descriptions of studies that have been planned, carried out and interpreted. There are sufficient details given to replicate the proposed experimental procedures for synthesis of S and P dual-doped carbon nanospheres and electrochemical measurements.
• Interpretations based on the investigations of the synthesis of S and P dual-doped carbon nanospheres, obtained by X-ray diffraction and SEM-EDS need to be clarified.

 The specific comments are as follows:

 Material characterization

• Morphologies of the synthesis of S and P dual-doped carbon nanospheres were observed only by scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS). Transmission electron microscopy (TEM) and HRTEM determinations would be useful for the characterization of the S and P dual-doped carbon nanospheres.
• in the section Results and discussion there are information regarding the characterization of the material synthesized by X-ray diffraction (XRD) in this section there is no information about XRD characterization method and used device

Results and discussion

• Figure 2 - The SEM and elemental mapping images quality are poor and needs to be improved. It is recommended to take SEM images at less than 2 to support the statements presented in Line 96-104. Also, the elemental mapping images should be accompanied by elemental distributions of P, S and C.
• it is recommended to use the XRD results to calculate interlayer spacing, FWHM values and microcrystalline parameters and correlated with the BET information.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Accept in present form

Reviewer 3 Report

• the authors responded to the comments that I made at the first review
• I maintain the observation of too many self-citations by author Jun Kang