Redox Evolution of Li-Rich Layered Cathode Materials

Round 1

Reviewer 1 Report

Title: Redox evolution of Li-rich layered cathode materials

Manuscript ID: batteries-1898395

The current review article discusses the usage of various synchrotron X-ray spectroscopy techniques to identify the redox behavior of Li-rich layered cathodes for high-energy-density Li-ion batteries. The article is well structured and explained case-by-case the different redox evolution processes for several transition metals. The present article is suited for the batteries journal readership and is useful for budding researchers who are focusing their research on advanced batteries. Hence, I would recommend the article for publication in the batteries journal. However, the authors should pay attention to the following comments and are needed to be resolved before its definitive publication.

1.      PDF page 2, line 76, the authors stated, “Because a structural rearrangement occurs during the activation of anionic redox in the first cycle……”. The authors are suggested to provide credible evidence to prove their statement. 

2.      In Fig. 3 (c), I believe that the EXAFS results of Ni and Mn are not presented even though mentioned in the figure caption. The authors are suggested to add the missing figures.

3.      The authors are suggested to tabulate key advantages and disadvantages of each characterization technique which I believe will strengthen the quality of the current review article.

4.      The quality of Fig. 5 (d) is poor. The authors are suggested to present the zoomed picture as it is difficult to grasp the numbers.

 

 

Comments for author File: Comments.docx

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript provides a concise and easy to understand review of current understanding of anion vs. cation redox in Li-rich layered cathode materials. There are some improvements that could be made to increase the impact of this contribution, as suggested below.

1. Given the strong focus on synchrotron X-ray derived understanding, the authors could consider incorporating this into the title to appeal to those working in such fields.

2. This work focuses on layered cathodes, although there are other types of Li-rich cathodes that employ oxygen (or other anion) redox. In the spirit of the review format, the authors should make some references to such materials and point out any significant generalities or differences in behavior/understanding that exist.

3. In the paragraph beginning on line 228, it is concluded that the impact of transition metals on oxygen redox is a complicated mystery that goes beyond electronic energy levels. Surely there are some current hypotheses regarding their impact that could be provided so as to point readers in fruitful directions. 

4. In figures 2-5, the specific material being measured is not mentioned in the caption. It would be helpful to add this information to the captions.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Thank you for the intersting and short/compact review of methods used and meterials in this specific field, that is helpful for further investigation

Some minor remarcs:

Fig. 3 c. text says Ni Co Mn but in the figure Co-0  Co-M is shown, maybe this figure could be descibted in more detail what can be seen here.

Fig. 4 b, c would be nice to use uniform labels (norm. Abs or normalized Abs)

 

221 stabilize an/or activate ! ?

230 activating and stabilizing !?

Author Response

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Reviewer 4 Report

The manuscript entitled "Redox evolution of Li-rich layered cathode materials" is very well organised and written. The review provides good overview of various characterisation techniques to understand the redox behaviour of Li-rich layered materials. This work would help to further the research activities to develop high energy density cathode materials based on Li-rich compounds, which is an important research area. I find the manuscript suitable for publication in 'Batteries' in its preset form.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have addressed all of the concerns raised. Hence, I would recommend publishing the article in its present form.

Reviewer 2 Report

No further comments.