Essential Electronic Properties of Stage-1 Li/Li⁺-Graphite-Intercalation Compounds for Different Concentrations

Round 1

Reviewer 1 Report

The authors in this manuscript are trying to compare Li and Li⁺ graphite intercalation compounds by calculating various electronic properties such as band structures, the density of states, spatial charge distribution, etc. 

One of the major concerns in their study is the method opted. In the abstract, they do mention that "we find that there exists weak but significant Vander Waals interactions between interlayer of graphite"  but in the methodology section I don't see if they have considered Vander Waals correction in their calculation. I would suggest authors, for better accuracy, recalculate everything using Grimme's D3 correction as implemented in VASP the software they opted for this study. There is no mention of how Li⁺ is considered in the calculation. Is it a different POTCAR file or do they reduce the number of electrons by fixing the NELECT tag in the INCAR file? If the latter is true then obviously the Fermi energy will go down as compared to Li-GIC systems.

Moreover, there are many typos (e.g. see Table 1 it should be Li/Li⁺) and superscript/subscripts that are not used in the text can create confusion for readers. 

1) There is no need for Fig. 1 of their manuscript as it is standard and well known in the community. 

2) The caption in Fig. 2 is not properly written, I can't figure out what blue, green, and red colors mean.

 3) Line number 129: please mention how \rho and \delta rho are calculated? Keep the symbol of \rho same in Figures 6 and 7.

4) Line 164: There is a typo "5. Conclusions"

I cannot recommend this paper be published in this form. 

Author Response

Response to reviewer 1 comments

Point 1: One of the major concerns in their study is the method opted. In the abstract, they do mention that "we find that there exists weak but significant Vander Waals interactions between interlayer of graphite"  but in the methodology section I don't see if they have considered Vander Waals correction in their calculation. I would suggest authors, for better accuracy, recalculate everything using Grimme's D3 correction as implemented in VASP the software they opted for this study.  There is no mention of how Li⁺ is considered in the calculation. Is it a different POTCAR file or do they reduce the number of electrons by fixing the NELECT tag in the INCAR file? If the latter is true then obviously the Fermi energy will go down as compared to Li-GIC systems.

Response 1:  We consider the Vander Waals interactions with the IVDW=11 tag (under DFT-D3 method of Grimme). And we calculate the Li⁺ ion by fixing NELECT tag in the INCAR file.

Point 2:

1) There is no need for Fig. 1 of their manuscript as it is standard and well known in the community. 

2) The caption in Fig. 2 is not properly written, I can't figure out what blue, green, and red colors mean.

3) Line number 129: please mention how \rho and \delta rho are calculated? Keep the symbol of \rho same in Figures 6 and 7.

4) Line 164: There is a typo "5. Conclusions"

Response 2: All the problems about typo or captions are fixed. The ρ is directly obtained from the calculated charge density, but the Δρ is a value subtracting the charge density of the pure Li (or Li⁺) and of the pure C charge density from the charge density of Li-GIC (or Li⁺-GIC).

Reviewer 2 Report

This manuscript written by Wei-bang Le and co-authors is to report the first-principles DFT results the electronic properties on stage-1 Li- and Li+-graphite-intercalation compounds (GIC) for different concentrations, LiCx/Li+Cx for x taken as 6-36. 

This research is highly motivated by the search for new anode materials. The Introduction section can be improved by additional references and a detailed discussion of [10-13]. Whereas the modeled LiCx/Li+Cx compounds retain the semimetallic band structure, the significant van der Waals interactions between interlayer of graphite and charge transfer was found. There are some points to be clarified and corrected: 

• Line 6: fermi must be Fermi
• Lines 19, 105, etc.: pz, px needs z or x as a subscript
• Fig. 3b, Fig. 5: values of DOS and E_Fermi are needed
• The Bader analysis in Table 2 should be discussed in the text of the manuscript
• All references in the manuscript are not recent
• Line 165: carriers.5. Conclusions
• Other typos in the manuscript should be corrected
• A comparison with the previous studies [23,24] and [10-13] should be placed in the text of the manuscript, not in the Conclusions section 
• English of the manuscript must be improved

The manuscript should be revised to warrant publication in Condensed Matter journal. 

Author Response

Response to reviewer 2 comments

Point 1: This research is highly motivated by the search for new anode materials. The Introduction section can be improved by additional references and a detailed discussion of [10-13].

Response 1: The more discussion and introduction of references [10-13] are mentioned in the revised manuscript.

Point 2: 

• Line 6: fermi must be Fermi
• Lines 19, 105, etc.: pz, px needs z or x as a subscript
• Fig. 3b, Fig. 5: values of DOS and E_Fermi are needed
• The Bader analysis in Table 2 should be discussed in the text of the manuscript
• All references in the manuscript are not recent
• Line 165: carriers.5. Conclusions
• Other typos in the manuscript should be corrected

Response 2: The typo and superscript/subscript have been revised. And the Bader analysis is discussed in detail in the manuscript. 

Point 3: All references in the manuscript are not recent

Response 3: We hope to construct the complete theoretical framework, including the geometry and electronic properties, based on the DFT method. There are some recent papers related to the Li-GICs focusing on the electrochemical analysis such as redox potential, but seldom works mention the essential electronic properties.  If needed, we can modify the manuscript with recent ones.

Round 2

Reviewer 1 Report

The language of the manuscript is greatly improved now and the results can help the battery community to understand the interaction of Li-ion or atom with graphite. I can recommend this article to be published after appending the following comments.

Some comments and minor typos are:


1) In lines 7 and 9, there are typos in the affiliation, please check “Tainan”.

2) The introduction must be elaborated, I would suggest authors have a look at the following recent articles:

a) Varun Gopalakrishnan et al 2021 J. Electrochem. Soc. 168 040541

b) Jain, R. et al. Alloying of Alkali Metals with Tellurene. Adv. Energy Mater. 11, 2003248 (2021).

c) Lakhnot, A. S. et al. Aqueous lithium-ion batteries with niobium tungsten oxide anodes for superior volumetric and rate capability. Energy Storage Mater. 27, 506–513 (2020).

d) Ji, K., Han, J., Hirata, A. et al. Lithium intercalation into bilayer graphene. Nat Commun10, 275 (2019). https://0-doi-org.brum.beds.ac.uk/10.1038/s41467-018-07942-z



3)In figure 4 please mention what is the red and blue color in the graph, probably they are up and down spin channels.

4) Match the symbol for charge density used in the text with Figures 6 and 7. 

Reviewer 2 Report

The revised manuscript can be published