Peer Review File

Tailoring superstructure units for improved oxygen redox
activity in Li-rich layered oxide battery’s positive electrodes
Corresponding Author: Dr Sylvio Indris

Version 0: 

Reviewer comments: 

Reviewer #1 

(Remarks to the Author) 
The authors revealed a direct correlation between oxygen redox activity and honeycomb superstructure units in Li-rich
layered oxides, specifically the fractions of LiMn6 and Ni4+ stabilized LiNiMn5 within the TM layer and an excess of
LiNiMn5 impedes the extraction/insertion of lithium ions during charging/discharging, resulting in incomplete oxygen redox
activity. It is generally agreed upon that the increase in Ni content will reduce the specific capacity and the first cycle
efficiency and result in an increase in Ni oxidation state from the reports from Qi et al (Electrochem 2023, 4, 21–30) and
Chong et al (RSC Adv. 2016, 6, 53662). Here the authors show the similar phenomenon but with a reasonable explanation
or mechanism for these conclusions, therefore I am unsure of the overall novelty - this should be addressed. 

Overall, this manuscript could be published after a minor revision. 

For Figure 2d and 2f, the signals are very weak, and the noise is higher, how much confidence you have for the data? Figure
2c, 2e and 2f, it seems that the authors only showed three points, where is the fourth point data/curve? 

To address these intrinsic properties in high-nickel Li-rich layered oxides, the authors proposed to reduce the Li content
during synthesis, please explain the rational design, why Li content determine the amount of the LINiMn5? Also, why not just
to optimize the Ni/Mn ratios instead? 

Reviewer #2 

(Remarks to the Author) 
Li-rich layered oxides have high capacity because of high-voltage oxygen redox activity. Li-rich cathodes with a high nickel
content exhibit improved voltage stability but suffer from poor discharge capacity. This work tailors the LiNiMn5
superstructure content by modification of Ni and Li contents. The study finds that an excess of LiNiMn5 impedes the
extraction/insertion of lithium ions during charging/discharging, resulting in incomplete oxygen redox activity (retention of
molecular O2) at low potential (~3.3 V, versus Li+/Li). If the evidence is sufficient, the work is more interesting to open a new
idea for enhanced oxygen redox of Li-rich layered oxides. There are several puzzling problems, so it is not recommended for
publication: 
1, In Li1.20NixMn0.8-xO2, x = 0.28, 0.32, 0.36, 0.40 materials, the content of Ni with +4 valence increases with the increase
of x or the decrease of Li content. The work finds that the LiNiMn5 superstructure content increases with the increase of x or
Li content. This is contradictory. The LiNiMn5 superstructure content is determined by the Li content or the ratio of Li/TM?
Please give a reasonable interpretation. 
2. In conventional LLOs such as Li1.2Ni0.2Mn0.6O2, generally, based on Pauling´s electrostatic valence rule, LiMn6
configurations are preferably aggregated in Li2MnO3 due to their special stability. So it is difficult to permeate Ni to
Li2MnO3. Many researches found that the breakdown of aggregated Li2MnO3, such as the permeation of TM with strong
TM-O bonds, benefited the enhanced oxygen redox. Though the work gives evidence of LiNiMn5 configurations, why can
the LiNiMn5 configurations exist in the work? Why is a reason that LiNiMn5 configurations result in incomplete oxygen redox
activity? 
3. The work does not provide TEM images, thus the other existence of Ni is unclear, and for example, the occupation of less
Ni at Li-layer sites reduced oxygen release and lowered voltage decay. 
4. The DOS of Li44Mn18Ni10O72 (Li1.22Mn0.50Ni0.28O2) is employed using DFT calculations. The state of Ni4 is +4, as



expected in the work’s model. Other models without the LiNiMn5 configurations are stable? 
5. In addition, 231.1 mAh g-1 at C/10 and a capacity retention of 84.8% after 200 cycles at C/3 is not high, such as 276.5
mAh g−1 at C/10 and 85.4% after 300 cycles at 1 C of Li1.2Ni0.2Mn0.6O2(Li J, ACS nano, 2023, 17, 16827-16839). 

Version 1: 

Reviewer comments: 

Reviewer #1 

(Remarks to the Author) 
After carefully reading the revised the manuscript, I have decided to approve the manuscript to proceed with the publication. 

Thanks and let me know if you have any questions. 

Best, 

Gongshin 

Reviewer #2 

(Remarks to the Author) 
The work is carefully modified. But there is one puzzling problem. 
--The DOS of Li44Mn18Ni10O72 (Li1.22Mn0.50Ni0.28O2) is employed using DFT calculations. The state of Ni4 is +4, as
expected in the work’s model. So the structural stability with one LiNiMn5 configuration instead of the state of Ni4 with +4
should be explored, because the chemical valence of Ni4 is related to the structure. 
In addition, to improve the redox reversibility of lattice oxygen and cycling performance, recently two works (ACS Nano
2023, 17, 16827−16839; Nano Energy, 2024, 123, 109390) are done though tuning the Li2MnO3 domain, please cite them. 

Version 2: 

Reviewer comments: 

Reviewer #2 

(Remarks to the Author) 
it is recommended for publication. 



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REVIEWER COMMENTS 
Reviewer #1 (Remarks to the Author): 
The authors revealed a direct correlation between oxygen redox activity and honeycomb 

superstructure units in Li-rich layered oxides, specifically the fractions of LiMn6 and Ni4+ 

stabilized LiNiMn5 within the TM layer and an excess of LiNiMn5 impedes the 

extraction/insertion of lithium ions during charging/discharging, resulting in incomplete oxygen 

redox activity. It is generally agreed upon that the increase in Ni content will reduce the specific 

capacity and the first cycle efficiency and result in an increase in Ni oxidation state from the 

reports from Qi et al (Electrochem 2023, 4, 21–30) and Chong et al (RSC Adv. 2016, 6, 53662). 

Here the authors show the similar phenomenon but with a reasonable explanation or 

mechanism for these conclusions, therefore I am unsure of the overall novelty - this should be 

addressed. 

Overall, this manuscript could be published after a minor revision. 

 

For Figure 2d and 2f, the signals are very weak, and the noise is higher, how much confidence 

you have for the data? Figure 2c, 2e and 2f, it seems that the authors only showed three points, 

where is the fourth point data/curve? 

 

To address these intrinsic properties in high-nickel Li-rich layered oxides, the authors proposed 

to reduce the Li content during synthesis, please explain the rational design, why Li content 

determine the amount of the LINiMn5? Also, why not just to optimize the Ni/Mn ratios instead? 

 

Reviewer #2 (Remarks to the Author): 
Li-rich layered oxides have high capacity because of high-voltage oxygen redox activity. Li-

rich cathodes with a high nickel content exhibit improved voltage stability but suffer from poor 

discharge capacity. This work tailors the LiNiMn5 superstructure content by modification of Ni 

and Li contents. The study finds that an excess of LiNiMn5 impedes the extraction/insertion of 

lithium ions during charging/discharging, resulting in incomplete oxygen redox activity 

(retention of molecular O2) at low potential (~3.3 V, versus Li+/Li). If the evidence is sufficient, 

the work is more interesting to open a new idea for enhanced oxygen redox of Li-rich layered 

oxides. There are several puzzling problems, so it is not recommended for publication: 
1. In Li1.20NixMn0.8-xO2, x = 0.28, 0.32, 0.36, 0.40 materials, the content of Ni with +4 valence 

increases with the increase of x or the decrease of Li content. The work finds that the LiNiMn5 

superstructure content increases with the increase of x or Li content. This is contradictory. The 

LiNiMn5 superstructure content is determined by the Li content or the ratio of Li/TM? Please 

give a reasonable interpretation. 



2. In conventional LLOs such as Li1.2Ni0.2Mn0.6O2, generally, based on Pauling´s electrostatic 

valence rule, LiMn6 configurations are preferably aggregated in Li2MnO3 due to their special 

stability. So it is difficult to permeate Ni to Li2MnO3. Many researches found that the breakdown 

of aggregated Li2MnO3, such as the permeation of TM with strong TM-O bonds, benefited the 

enhanced oxygen redox. Though the work gives evidence of LiNiMn5 configurations, why can 

the LiNiMn5 configurations exist in the work? Why is a reason that LiNiMn5 configurations result 

in incomplete oxygen redox activity? 

3. The work does not provide TEM images, thus the other existence of Ni is unclear, and for 

example, the occupation of less Ni at Li-layer sites reduced oxygen release and lowered 

voltage decay. 

4. The DOS of Li44Mn18Ni10O72 (Li1.22Mn0.50Ni0.28O2) is employed using DFT calculations. The 

state of Ni4 is +4, as expected in the work’s model. Other models without the LiNiMn5 

configurations are stable? 

5. In addition, 231.1 mAh g-1 at C/10 and a capacity retention of 84.8% after 200 cycles at C/3 

is not high, such as 276.5 mAh g−1 at C/10 and 85.4% after 300 cycles at 1 C of 

Li1.2Ni0.2Mn0.6O2(Li J, ACS Nano, 2023, 17, 16827-16839). 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



Point-to-point Response to Reviewers’ Comments 
 

Tailoring Superstructure Units for Enhanced Oxygen Redox in Li-Rich Layered 
Oxides 

(Manuscript ID NCOMMS-24-16929) 
 
We sincerely thank the editor and all reviewers for their valuable review comments that we 

have used to improve the quality of our manuscript. The reviewer comments are laid out below 

and specific concern have been numbered, and all the responses are listed in the following 

section, point by point. 

 
Reviewer #1 (Remarks to the Author): 
The authors revealed a direct correlation between oxygen redox activity and honeycomb 

superstructure units in Li-rich layered oxides, specifically the fractions of LiMn6 and Ni4+ 

stabilized LiNiMn5 within the TM layer and an excess of LiNiMn5 impedes the 

extraction/insertion of lithium ions during charging/discharging, resulting in incomplete oxygen 

redox activity. It is generally agreed upon that the increase in Ni content will reduce the specific 

capacity and the first cycle efficiency and result in an increase in Ni oxidation state from the 

reports from Qi et al (Electrochem 2023, 4, 21–30) and Chong et al (RSC Adv. 2016, 6, 53662). 

Here the authors show the similar phenomenon but with a reasonable explanation or 

mechanism for these conclusions, therefore I am unsure of the overall novelty - this should be 

addressed. 

Overall, this manuscript could be published after a minor revision. 

 

Response: Thank you for the high evaluation of our work. In the following, we will address all 

the comments sequentially.  

 

1. It is generally agreed upon that the increase in Ni content will reduce the specific capacity 

and the first cycle efficiency and result in an increase in Ni oxidation state from the reports from 

Qi et al (Electrochem 2023, 4, 21–30) and Chong et al (RSC Adv. 2016, 6, 53662). Here the 

authors show the similar phenomenon but with a reasonable explanation or mechanism for 

these conclusions, therefore I am unsure of the overall novelty - this should be addressed. 

 

Response: We appreciate the reviewer’s comment. As indicated by previous publications 

(Electrochem 2023, 4, 21–30; RSC Adv. 2016, 6, 53662; J. Mater. Chem. A. 2015, 3, 22199), 

there has been considerable interest in elucidating the role of nickel content in the 

electrochemistry of Li-rich layered oxides. Unfortunately, these studies primarily focused on 



electrochemical characterization and did not provide a satisfactory explanation for the poor 

electrochemical performance of high-nickel Li-rich layered oxides. Moreover, no universal 

solutions to address this issue have been identified. Our research fills this gap by offering a 

reasonable explanation and potential solutions to improve the electrochemistry of high-nickel 

Li-rich layered oxides. 

 

Based on earlier studies, our work innovatively employed a series of advanced techniques, 

including SXRD, PDF, SXAS, RIXS, TEM (addressing Question 3 from Reviewer #2), NMR, 

DFT calculations, and electrochemical investigations. This comprehensive approach provides 

definitive answers to critical questions. Firstly, we identified the types of superstructure units 

within the transition metal layer and, for the first time, elucidate the influence of the nickel ions' 

valence state on these units. More importantly, we successfully revealed the intrinsic 

correlation between oxygen redox activity and superstructure units, elucidating the mechanism 

behind the poor discharge capacity observed in high-nickel Li-rich cathodes. Additionally, 

beyond elucidating the mechanism, we proposed a potential solution to tailor superstructure 

units to enhance battery performance with reversible oxygen redox.  

 

Therefore, we believe that our conclusive evidence on tailoring superstructure units for 

enhanced oxygen redox in Li-rich layered oxides will be of significant interest to both the battery 

community and the broader readership of Nature Communications. 

 

Changes made: 
In the revision manuscript, we inserted additional references in the introduction on page 3. 

20. Qi, G. et al. Impact of Ni Content on the Electrochemical Performance of the Co-Free, Li 

and Mn-Rich Layered Cathode Materials. Electrochem 4, 21–30 (2023). 

21. Knight, J. C. & Manthiram, A. Effect of nickel oxidation state on the structural and 

electrochemical characteristics of lithium-rich layered oxide cathodes. J. Mater. Chem. A 3, 

22199–22207 (2015). 

 

2. For Figure 2d and 2f, the signals are very weak, and the noise is higher, how much 

confidence you have for the data? Figure 2c, 2e and 2f, it seems that the authors only showed 

three points, where is the fourth point data/curve? 

 

Response:  
We appreciate the reviewer’s comments and fully understand their concerns regarding the 

data quality in the manuscript. In Fig. 2, our primary aim is to identify the redox nature of the 

dQ/dV peak observed below 3.7 V and elucidate the mechanism contributing to the poor 



capacity in high-nickel Li-rich cathodes. As discussed in the manuscript, this peak is typically 

associated with the reduction of oxygen (O) or manganese (Mn). Therefore, understanding the 

redox evolution of O and Mn, represented by changes in the O K-edge and Mn L-edge spectra, 

is crucial during charge and discharge. 

 

In our study, we selected four points—pristine, charged to 4.45 V, charged to 4.7 V, and 

discharged to 2.0 V—during the first cycle to collect the Ni, Mn L-edge, and O K-edge spectra 

with soft-XAS spectroscopy (Fig. 2a-d). The spectra of the Mn L-edge significantly overlap in 

Fig. 2c. To enhance clarity, we present the stack of Mn L-edge spectra in Fig. R2. Combining 

these with the O K-edge SXAS results, we identify that the incomplete oxygen redox occurs at 

a low potential (3.3 V vs. Li+/Li) in Li-rich layered oxides for a high-nickel system. 

 

Given this abnormal phenomenon, we additionally conducted O K-edge RIXS measurements 

(Fig. 2e,f) to further validate our findings. As depicted in Fig. 2e-f, a distinct characteristic peak 

C (around 7.8 eV) and a vibrational peak D around the elastic region (0 eV) are still observed 

at discharge to 2.0 V. This finding is consistent with previous O K-edge SXAS results, further 

supporting incomplete oxygen redox. Our data and findings are reasonable and well-justified. 

Additionally, similar O K-edge RIXS signals are documented in previous studies (Nat Commun. 

2021, 12, 3071; Nat Commun. 2022, 13, 1123; J. Am. Chem. Soc. 2023, 18, 10208-10219; 

Nat Energy. 2024, 9, 184–196). 

 

The absence of data at 4.45 V for the RIXS measurements does not influence the conclusion 

of this work. Therefore, we selected three of the most critical states for RIXS measurements 

(excluding the point at 4.45 V) to address our research questions. We hope for the reviewer’s 

understanding. 

 

 



Fig. R2. SXAS results of the Mn L-edge collected at pristine, charge to 4.45 V, charge to 4.7 

V, and discharge to 2.0 V states.  

 

3. To address these intrinsic properties in high-nickel Li-rich layered oxides, the authors 

proposed to reduce the Li content during synthesis, please explain the rational design, why Li 

content determine the amount of the LINiMn5? Also, why not just to optimize the Ni/Mn ratios 

instead? 

 

Response: We appreciate the reviewer for the careful review on our submitted work. 

Regarding why Li content determine the amount of the LINiMn5, our findings reveal that the 

LiNiMn5 superstructure units are exclusively stabilized by Ni4+ and not by Ni2+ or Ni3+. 

Therefore, to reduce the presence of LiNiMn5 units, the overall Ni valence state in Li-rich 

cathodes must be decreased. In our work, reducing the lithium content during synthesis 

effectively increases the overall transition metal (TM) content in the TM layer, as demonstrated 

by the increase from 0.80 in LM15 (Li1.2Ni0.36Mn0.44O2) to 0.87 in LM13 (Li1.13Ni0.39Mn0.48O2). 

XAS results confirm the decrease in the valence state of Ni, leading to a corresponding change 

in superstructure units. Specifically, the LiNiMn5/(LiNiMn5 + LiMn6) peak ratio decreases to 

42.7% for LM13, compared to 58.2% for LM15, as evidenced by NMR. As described in the 

response to Question 1 from reviewer #2, for a given Ni/Mn ratio, the LiNiMn5 superstructure 

content is determined by the Li content. This is because the Ni valence state changes as the 

Li content changes. 

 

Regarding, why not just to optimize the Ni/Mn ratios instead, we thank the reviewer for pointing 

out this method for tailoring LiNiMn5 units. We fully acknowledge the reviewer's suggestion to 

tailor LiNiMn5 units by further optimizing the Ni/Mn ratios in Li-rich cathodes. As evident from 

the electrochemical data (Fig. 1c-d) and the changes in superstructure units (Fig. 3a) observed 

in these cathodes with varying nickel contents, there may indeed be an optimal Ni/Mn ratio that 

can achieve both high capacity and high voltage.  

 

However, our primary aim is to elucidate the underlying mechanism behind the unsatisfactory 

electrochemistry observed in high-nickel Li-rich layered oxides. Therefore, we have chosen a 

practical and simple approach to validate the accuracy of our theoretical findings. Additionally, 

implementing the method of optimizing Ni/Mn ratios may require a significant number of 

precursor synthesis experiments, which falls beyond the scope of the current manuscript. 

Moreover, adjusting the lithium content provides additional benefits, such as modifying the 

superstructure content to fine-tune cation/anion redox contributions. This adjustment promotes 

higher cation redox, thereby enhancing structural stability compared to the instability 



associated with anion redox at high voltage. Moreover, moderate Li/Ni disordering promotes 

structural reversibility due to the pillar effect. Finally, this approach represents a practical and 

simple solution for industry applications when compared to other complex modification 

processes. Considering all these factors, the rationale for reducing Li content is reasonable 

and easily justified. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



Reviewer #2 (Remarks to the Author): 
Li-rich layered oxides have high capacity because of high-voltage oxygen redox activity. Li-

rich cathodes with a high nickel content exhibit improved voltage stability but suffer from poor 

discharge capacity. This work tailors the LiNiMn5 superstructure content by modification of Ni 

and Li contents. The study finds that an excess of LiNiMn5 impedes the extraction/insertion of 

lithium ions during charging/discharging, resulting in incomplete oxygen redox activity 

(retention of molecular O2) at low potential (~3.3 V, versus Li+/Li). If the evidence is sufficient, 

the work is more interesting to open a new idea for enhanced oxygen redox of Li-rich layered 

oxides. There are several puzzling problems, so it is not recommended for publication: 

 
Response: Thank you for the careful and in-depth review of our manuscript. In the following, 

we will address all the comments and revise the manuscript accordingly.  

 

1. In Li1.20NixMn0.8-xO2, x = 0.28, 0.32, 0.36, 0.40 materials, the content of Ni with +4 valence 

increases with the increase of x or the decrease of Li content. The work finds that the LiNiMn5 

superstructure content increases with the increase of x or Li content. This is contradictory. The 

LiNiMn5 superstructure content is determined by the Li content or the ratio of Li/TM? Please 

give a reasonable interpretation. 

 

Response: We appreciate the reviewer's comment. Our findings reveal that the LiNiMn5 

superstructure units are exclusively stabilized by Ni4+, rather than by Ni2+ or Ni3+. This 

stabilization is facilitated by the presence of Ni4+, which promotes the formation of LiNiMn5 

units in Li-rich cathodes. 

 

In materials such as Li1.20NixMn0.8-xO2 (x = 0.28, 0.32, 0.36, 0.40), with a Li/TM ratio of 1.5, an 

increase in x results in an increase in the valence state of Ni. As a consequence, 

Li1.2Ni0.40Mn0.40O2 (N40), with a higher Ni valence state, contains a greater proportion of 

LiNiMn5 units compared to Li1.2Ni0.28Mn0.52O2 (N28). 

 

Furthermore, for a given Ni/Mn ratio, reducing the lithium content during synthesis effectively 

increases the overall transition metal (TM) content in the TM layer, as demonstrated by the 

increase from 0.80 in LM15 (Li1.2Ni0.36Mn0.44O2) to 0.87 in LM13 (Li1.13Ni0.39Mn0.48O2). As a 

result, there are fewer LiNiMn5 units in the LM13 with lower valence state of Ni. 

 

Therefore, the LiNiMn5 superstructure content in Li-rich cathodes is not simply determined by 

the Li content or the ratio of Li/TM; rather, it changes only when the Ni valence state changes. 

 



2. In conventional LLOs such as Li1.2Ni0.2Mn0.6O2, generally, based on Pauling´s electrostatic 

valence rule, LiMn6 configurations are preferably aggregated in Li2MnO3 due to their special 

stability. So it is difficult to permeate Ni to Li2MnO3. Many researches found that the breakdown 

of aggregated Li2MnO3, such as the permeation of TM with strong TM-O bonds, benefited the 

enhanced oxygen redox. Though the work gives evidence of LiNiMn5 configurations, why can 

the LiNiMn5 configurations exist in the work? Why is a reason that LiNiMn5 configurations result 

in incomplete oxygen redox activity? 

 

Response: We are grateful to the reviewer for pointing out Pauling's electrostatic valence 

principle as a demonstration of the stability of the superstructure configuration. Indeed, we fully 

agree with the reviewer that the LiMn6 units are more likely to form in Li2MnO3 compared to 

other superstructure units. Furthermore, previous studies (Matter. 2022, 5, 3869-3882; 

Materials Today. 2021, 51, 15-26) also suggest that the Ni is difficult to detect within Li2MnO3-

like domains. However, the above conclusion is only based on the case in which Ni has a 

valence state of 2 or 3. The possibility of the presence of Ni4+ in LiNiMn5 superstructure units 

has been previously overlooked. Note that while Ni4+ is atypical in conventional layered 

cathodes, its presence in Li-rich cathode systems is plausible due to the lithium excess 

structural configuration (Chem. Mater. 2020, 32, 9211–9227).  

Based on Pauling’s electrostatic valence principle (J. Am. Chem. Soc. 1929, 51, 1010-1026) 

we can apply a semiquantitative equation to evaluate the stability of a coordination 

configuration (Materials Today. 2021, 51, 15-26): 

∆𝛧 = |𝛧𝛢 − Σ
𝛧𝑐

𝑛
| 

According to the principle of local electrical neutrality, a structure may become unstable if ∆𝛧 >

0. In Li-rich cathodes, three Li ions in the Li layer are consistently coordinated with central 

oxygen atom, while the coordination environments of cations in the transition metal layer may 

have different combinations. The most common LiMn6 units, equivalent to Li3-O-LiMn2, exhibit 

stable state with ∆Ζ = 0. In our work, LiNiMn5 units (Li3-O-LiNiMn) also demonstrate ∆Ζ = 0, 

attributed to the presence of Ni4+ rather than Ni2+ (∆Ζ = 1/3) and Ni3+ (∆Ζ = 1/6). Moreover, 

our 6Li NMR results clearly demonstrate the presence of these LiNiMn5 units in these Li-rich 

cathodes. 

 

Regarding Why the LiNiMn5 configurations result in incomplete oxygen redox activity, previous 

theoretical calculations (Matter. 2022, 5, 3869-3882) indicate that the Li4MnNi-coordinated O, 

referred to as LiNiMn5 in our work, has a much lower cationic and anionic redox activity 

compared to LiMn6 units, suggesting a poor electrochemical activity. Additionally, Li moves 

from one octahedral site to another octahedral site by passing through an intermediate 



tetrahedral site where it encounters strong repulsion from a nearby transition metal. The 

associated activation barriers for Li movement with Ni4+, Ni3+ and Ni2+ are 490, 310, and 210 

meV, respectively (Science. 2006, 311, 977-980). Therefore, these theoretical findings suggest 

that Ni4+-stabilized LiNiMn5 may impede the movement of lithium ions during 

charging/discharging. Moreover, Li-rich cathodes undergo a cationic–anionic redox inversion 

with significant chemical and electrochemical asymmetry between charge and discharge 

(Nature Mater. 2022, 21, 1165-1174). Consequently, at low potential during discharge, some 

Li ions fail to return to the transition metal layer to coordinate with O, resulting in incomplete 

oxygen redox. This observation is further supported by our experimental results, including 

SXAS, RIXS, ex-situ NMR, in-situ XRD, and electrochemistry. 

 

Changes made: 
In the revised manuscript, we have included additional content on page 10: “In addition, 

Pauling's electrostatic valence principle33 and semi-quantitative equation34 can be used to 

evaluate the possibility of a coordination configuration. According to principle of local electrical 

neutrality, a structure may become unstable if the local difference in valences of anions/cations 

∆𝛧 > 0. The most common LiMn6 units, equivalent to Li3-O-LiMn2, exhibit a stable state with 

∆Ζ = 0 . Similarly, LiNiMn5 units (Li3-O-LiNiMn) also demonstrate ∆Ζ = 0 , attributed to the 

presence of Ni4+ rather than Ni2+ (∆Ζ = 1/3) and Ni3+ (∆Ζ = 1/6). This elucidates why prior 

investigations failed to detect nickel within Li2MnO3-like domains, given that the possibility of 

the presence of Ni4+ in LiNiMn5 superstructure units has been previously overlooked34,35. 

Previous theoretical calculations35 indicate that the Li4MnNi-coordinated O, referred to as 

LiNiMn5 in our work, exhibits significantly lower cationic and anionic redox activity compared 

to LiMn6 units, indicating limited electrochemical activity. Moreover, lithium ions move from one 

octahedral site to another one, passing through an intermediate tetrahedral site where they 

encounter strong repulsion from nearby transition metals. The associated activation barriers 

for lithium movement with Ni4+, Ni3+ and Ni2+ have been calculated to be 490, 310, and 210 

meV, respectively36. These theoretical findings imply that LiNiMn5 may impede the 

extraction/insertion of lithium ions. During charging/discharging, Li-rich cathodes experience a 

cationic–anionic redox inversion, leading to electrochemical asymmetry23. As a consequence, 

at low discharge potentials, some lithium ions fail to return to the transition metal layer to 

coordinate with O, resulting in incomplete oxygen redox. This analysis is consistent with the 

findings from our O K-edge SXAS and RIXS experiments.” 

 

23. Li, B. et al. Capturing dynamic ligand-to-metal charge transfer with a long-lived cationic 

intermediate for anionic redox. Nat. Mater. 21, 1370–1379 (2022). 



33. Pauling, L. The principles determining the structure of complex ionic crystals. J. Am. Chem. 

Soc. 51, 1010–1026 (1929). 

34. Yin, C. et al. Structural insights into composition design of Li-rich layered cathode materials 

for high-energy rechargeable battery. Materials Today 51, 15–26 (2021). 

35. Yang, Y. et al. Cation configuration in transition-metal layered oxides. Matter 5, 3869–3882 

(2022). 

36. Kang, K., Meng, Y. S., Bréger, J., Grey, C. P. & Ceder, G. Electrodes with High Power and 

High Capacity for Rechargeable Lithium Batteries. Science 311, 977–980 (2006). 

 

3. The work does not provide TEM images, thus the other existence of Ni is unclear, and for 

example, the occupation of less Ni at Li-layer sites reduced oxygen release and lowered 

voltage decay. 

 

Response: We appreciate the reviewer's comment and suggestion. To investigate the 

potential influence of cation mixing (where Ni occupies Li sites) on the electrochemistry of Li-

rich cathodes with varying nickel contents, we conducted transmission electron microscopy 

(TEM) measurements. The high-resolution TEM (HRTEM) images of N28, N32, N36, and N40, 

as depicted in Fig. R3, reveal clear lattice fringes without obvious evidence of cation mixing. 

Moreover, the observed average interplanar spacing of approximately 0.47 nm corresponds to 

the (003)R or (001)M plane of the layered rhombohedral (R-3m) or monoclinic (C2/m) structure. 

Additionally, integrating the previously conducted high-resolution synchrotron X-ray diffraction 

(SXRD) measurements, we conclude that cation mixing has little impact on the 

electrochemistry of these cathodes. This further underscores the close correlation between 

honeycomb superstructure units and electrochemistry in our work. 

 

Changes made: 
In the revised manuscript, we have included additional content on page 6 in the manuscript 

and page 5 in the supporting information “The high-resolution transmission electron 

microscopy (HRTEM) images of N28, N32, N36, and N40, as shown in Supplementary Fig. 4, 

reveal clear lattice fringes without obvious evidence of cation mixing. Moreover, the observed 

average interplanar spacing of approximately 0.47 nm corresponds to the (003)R or (001)M 

plane of the layered rhombohedral (R-3m) or monoclinic (C2/m) structure.” 

 

Additionally, we have included additional content on the page 20 in the Methods section 

“Structural information about the samples was obtained by high-resolution transmission 

electron microscopy (HRTEM). Each specimen was examined using Thermofisher Talos 

F200X TEM operated at 200 kV.” 



 
Fig. R3. HRTEM images of N28 (a-b), N32 (c-d), N36 (e-f), and N40 (g-h) powder. 

 

4. The DOS of Li44Mn18Ni10O72 (Li1.22Mn0.50Ni0.28O2) is employed using DFT calculations. The 

state of Ni4 is +4, as expected in the work’s model. Other models without the LiNiMn5 

configurations are stable? 

 

Response: We appreciate the reviewer's comment. We also performed calculations on a 

model without the LiNiMn5 unit of Li44Mn18Ni10O72 (Li1.22Mn0.50Ni0.28O2). The energy difference 

between this model and the one containing the LiNiMn5 unit was minimal, approximately 0.005 



eV/atom. As a result, it can be concluded that their energies are the same, and they can be 

stable. 

 

5. In addition, 231.1 mAh g-1 at C/10 and a capacity retention of 84.8% after 200 cycles at C/3 

is not high, such as 276.5 mAh g−1 at C/10 and 85.4% after 300 cycles at 1 C of 

Li1.2Ni0.2Mn0.6O2(Li J, ACS Nano, 2023, 17, 16827-16839). 

 

Response: We appreciate the reviewer for the careful review on our submitted work. We fully 

agree with the reviewer that our cathode (LM13) exhibits lower discharge capacity compared 

to the classical Li-rich cathode (Li1.2Ni0.2Mn0.6O2). Despite achieving high capacity and stability 

by various modification in recent years, these Li-rich cathodes still encounter substantial 

voltage decay during cycling. As highlighted in the introduction, optimizing the chemical 

composition has emerged as a promising approach to mitigate voltage decay in layered Li-rich 

cathodes (Adv. Energy Mater. 2018, 8, 1800606; ACS Appl. Mater. Interfaces. 2016, 8, 20138–

20146). Additionally, high-nickel Li-rich layered oxides offer several advantages in stabilizing 

voltage and reducing oxygen release (Nat. Mater. 2023, 22, 1370–1379). However, high-nickel 

Li-rich cathodes, such as Li1.2Ni0.4Mn0.4O2, have garnered less attention due to their lower 

discharge capacity (less than 200 mAh g-1 at C/10) compared to low-nickel Li-rich cathodes 

(Electrochem 2023, 4, 21–30; RSC Adv. 2016, 6, 53662; J. Mater. Chem. A. 2015, 3, 22199). 

Thus, the key to advancing Li-rich cathodes is achieving voltage stability in high-nickel systems 

without compromising discharge capacity. 

Therefore, the primary aim of this work is to elucidate the underlying mechanism behind the 

unsatisfactory electrochemistry observed in high-nickel Li-rich layered oxides. Building on the 

insights gained from the mechanism, we propose a practical and straightforward solution to 

tailor superstructure units, thereby enhancing oxygen redox reversibility and improving battery 

performance (from 199.0 to 231.1 mAh g-1 at C/10). Our strategy has proven to be efficient 

compared to pristine high-nickel Li-rich cathodes. As described in the discussion in the 

manuscript, adjusting the lithium content during synthesis, in addition to changes in 

superstructure units, affects other parameters such as superstructure content, Li/Ni disorder, 

and stacking faults. Therefore, future research endeavours may focus on exploring these 

parameters and achieving a balance to further enable high-energy-density, high-nickel Li-rich 

layered oxides. 

 

 



REVIEWER COMMENTS 
Reviewer #1 (Remarks to the Author): 
After carefully reading the revised the manuscript, I have decided to approve the manuscript 

to proceed with the publication. 

 

Thanks and let me know if you have any questions. 

 

Best, 

 

Gongshin 

 

Reviewer #2 (Remarks to the Author): 
The work is carefully modified. But there is one puzzling problem. 

--The DOS of Li44Mn18Ni10O72 (Li1.22Mn0.50Ni0.28O2) is employed using DFT calculations. The 

state of Ni4 is +4, as expected in the work’s model. So the structural stability with one LiNiMn5 

configuration instead of the state of Ni4 with +4 should be explored, because the chemical 

valence of Ni4 is related to the structure. 

In addition, to improve the redox reversibility of lattice oxygen and cycling performance, 

recently two works (ACS Nano 2023, 17, 16827−16839; Nano Energy, 2024, 123, 109390) are 

done though tuning the Li2MnO3 domain, please cite them. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



Point-to-point Response to Reviewers’ Comments 
 

Tailoring Superstructure Units for Enhanced Oxygen Redox in Li-Rich Layered 
Oxides 

(Manuscript ID NCOMMS-24-16929A) 
 
We sincerely thank the editor and all reviewers for their valuable review comments that we 

have used to improve the quality of our manuscript. The reviewer comments are laid out below 

and specific concern have been numbered, and all the responses are listed in the following 

section, point by point. 

 
Reviewer #1 (Remarks to the Author): 
After carefully reading the revised the manuscript, I have decided to approve the manuscript 

to proceed with the publication. 

 

Thanks and let me know if you have any questions. 

 

Best, 

 

Gongshin 

 

Response: We highly appreciate the reviewer’s positive comments. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



Reviewer #2 (Remarks to the Author): 
The work is carefully modified. But there is one puzzling problem. 

--The DOS of Li44Mn18Ni10O72 (Li1.22Mn0.50Ni0.28O2) is employed using DFT calculations. The 

state of Ni4 is +4, as expected in the work’s model. So the structural stability with one LiNiMn5 

configuration instead of the state of Ni4 with +4 should be explored, because the chemical 

valence of Ni4 is related to the structure. 

In addition, to improve the redox reversibility of lattice oxygen and cycling performance, 

recently two works (ACS Nano 2023, 17, 16827−16839; Nano Energy, 2024, 123, 109390) are 

done though tuning the Li2MnO3 domain, please cite them. 

 
Response: Thank you for the careful and in-depth review of our manuscript. In the following, 

we will address all the comments and revise the manuscript accordingly.  

 

1. The DOS of Li44Mn18Ni10O72 (Li1.22Mn0.50Ni0.28O2) is employed using DFT calculations. The 

state of Ni4 is +4, as expected in the work’s model. So the structural stability with one LiNiMn5 

configuration instead of the state of Ni4 with +4 should be explored, because the chemical 

valence of Ni4 is related to the structure. 

 

Response: We appreciate the reviewer's comment. We have calculated the oxidation state of 

Ni in the LiNiMn5 configuration without a priori assumptions on the Ni oxidation state. The 

relaxed structure shows that Ni possesses the oxidation state +4. In addition, we have 

calculated models with the same overall composition but without the LiNiMn5 configuration 

(always without assuming the oxidation state a priori), in which we find that Ni has an oxidation 

state lower than +4. Based on that we conclude the LiNiMn5 configuration stabilize Ni in the 

oxidation state +4 in the structure. 

 

2. In addition, to improve the redox reversibility of lattice oxygen and cycling performance, 

recently two works (ACS Nano 2023, 17, 16827−16839; Nano Energy, 2024, 123, 109390) are 

done though tuning the Li2MnO3 domain, please cite them. 

 

Response: We are grateful to the reviewer for pointing out the importance of the tuning of 

Li2MnO3 domain size or distribution to the oxygen redox reversibility of Li-rich cathodes. To 

better reflect this recent progress, we have added the relevant content in the Introduction and 

cited the relevant studies. 

 

Changes made: 



In the revised manuscript, we have included additional content on page 3: “For instance, a 

consensus has emerged form relevant studies, highlighting the detrimental role of localized 

superstructure domains characterized by in-plane Li/Mn order of Li-rich cathodes, while 

delocalized or dispersed domains characterized by in-plane Li/Mn disorder effectively improve 

the oxygen redox reversibility and voltage stability10–12.” 

 

10. Li, J. et al. Tuning Li2MnO3-Like Domain Size and Surface Structure Enables Highly-

stabilized Li-Rich Layered Oxide Cathodes. ACS Nano 17, 16827–16839 (2023). 

11. Guo, X. et al. Weak σ–π–σ interaction stabilizes oxygen redox towards high-performance 

Li-rich layered oxide cathodes. Nano Energy 123, 109390 (2024). 

12. Zhang, M. et al. Formulating Local Environment of Oxygen Mitigates Voltage Hysteresis in 

Li-Rich Materials. Advanced Materials 36, 2311814 (2024). 


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