Defective oxygen inert phase stabilized high-voltage nickel-rich cathode for high-energy lithium-ion batteries

Pushing layered cathode to higher operating voltage can facilitate the realization of high-energy lithium-ion batteries. However, the released oxygen species initiate materials surface upon highly delithiated states will react severely with electrolyte, accelerating the structure deterioration and triggering the thermal degradation. Here we propose an inert phase of La2Mo2O9 with abundant oxygen vacancies (about 41%) by regulating the annealing temperature to engineer the cathode interface beyond conventional modifications. By employing LiNi0.8Co0.1Mn0.1O2 as a model system and extending to higher voltage-operated LiCoO2 and Li-rich cathode, we demonstrate that the introduced lanthanum and molybdenum ions will transfer electrons to enhance the surface oxygen electronegativities, thus served as “oxygen anchor” to alleviate oxygen evolution. Furthermore, the possible released oxygen can be operando captured and reserved by β-phase La2Mo2O9 depositor for the intrinsic high oxygen vacancy formation energy. The reaction involving oxygen species with electrolyte is fundamentally diminished, thus effectively mitigate the structure deterioration and elevate the electrochemical performances, enabling a 1.5-Ah pouch-type full cell to exhibit negligible 6.0% capacity loss after 400 cycles.

In this manuscript, the authors discuss the effect of stabilizing the oxygen-defective inert phase on the cathode properties of nickel-rich cathode material from various perspectives, such as bulk structure and surface structure, in addition to electrochemical properties.The discussion has many very interesting contents, but the reviewer had doubts about the following contents.
1.The Ni L-edge XAS spectrum of each cathode after 4.5 V charged state results are shown in Fig. 1 (h).The authors claim that Ni4+ is decreasing based on this result, but in addition to the initial results, I think that necessary information such as the shape of the Ni3+ spectrum is lacking.
2. Although the oxygen vacancies are discussed, it is presumed that the oxygen vacancies are affecting other electronic states of oxygen.The difference between P-NCM and L-NCM with EPR and XPS has been debated.If you measure O K-edge spectra using s-XAS, I think you can understand more details.You are measuring Ni L-edge spectra, but are you also measuring O results?DFT calculations have also been carried out, so I think we can understand the details further by discussing them in combination with the results.

Reviewer #2 (Remarks to the Author):
The article which I received to review from Dai et al. proposed a strategy of using electrondonating, oxygen-defect-rich La2Mo2O9 layer as surficial protection on lithium metal oxide cathodes to suppress the lattice oxygen evolution and capture it, if generated.This strategy improves the high-voltage cathode stability, as the protection layer mitigates the lattice rearrangement, stress accumulation and particle fracturing due to oxygen release.The results demonstrated improved performance.Many advanced characterization techniques with theoretical simulations verified the improved stability from interface to internal.It is a great work with novel design and decent understanding.But there are many places that remain ambiguous and confusing, which need improvements.I think this work can be published in Nature Communications but after a major revision based on the comments below.1.The authors observed improved stability from both interfacial and bulk characterizations from the L-NMC sample, while the material is only subjected to a surficial modification (LMO deposition).I think it will be meaningful if the authors can discuss and highlight how interfacial stability can propagate to a bulk structural stability.2. Page 5 line 9, the authors need to provide references for XPS peak assignments.And if LMO is highly enriched with O vac., why does the L-NCM vacancy signal only marginally increase in supplementary figure 6.As depth of XPS detection is several nm, the signal of L-NCM should largely originate from LMO.Also, why there is no lattice oxygen from P-NCM. 3. Page 5 line 19, is the O release due to receiving electron from transition metal or losing electron to it?And I guess the authors might meant to say "band" instead of "bond" there.4. Figure 1c EDS, why do the La and Mo signals completely overlap with Ni-Co-Mn, if the LMO is surficial deposition? 5.There is overall very little information on sample preparations for nearly all the characterizations.6.The coulombic efficiency must be included in Fig 2g-i as they are direct indicatives of the cathode side reaction extents, especially at high voltage.7. Supplementary Fig 18 .The LiF from L-NCM decreased, but the other F-containing compound largely increased.How did the authors conclude mitigated electrolyte decomposition from it?And why is there a large increase in the OCO2 signal from P-NCM? 8. Supplementary Fig 19 .It's very difficult to conclude there is noticeable decreasing at all, upon etching.9.The SEM Fig 4 g, h and the discussions are very misleading.First, it's very unlikely that any SEI can be observed at such magnification.The SEM images here can only show the Li deposition morphology.The top-view even needs zoon-in for just observing detailed Li morphology.Second, the LMA cycled in the carbonate electrolyte that the authors use in this work is highly impossible to deliver smooth deposition, even without any interference from cathode.The 4h-right figure does not indicate the SEI information.Instead, the observed layer is the porous Li deposition after long-term LMA cycling.Therefore, the smooth surface of 4h-left does not make sense.Here I do not suspect that mitigating the TM crosstalk can improve the Li deposition.But better images are needed with correct interpretations.10.What's the depth of detection from XANES and EXAFS used in this work?Are they suitable for detecting surficial changes without being affected by bulk information?11. Figure 5i.Where is the LMO deposition layer which is supposed to be on the NCM surface with the thickness at around 5 nm as indicated in Fig 1c ?Reviewer #3 (Remarks to the Author): 1) The manuscript reports an importance class of cathode materials in the field of Lithium-ion battery, with detailed and very insightful experimental and computational investigations.The results show clearly that the use of lanthanum molybdate improves the properties of P-NCM.However, it is necessary to compare these results with those similar-focused studies reported in the literature, especially experimental results, in order to better appreciate the importance of the present study.The following literature can help you: https://doi.org/10.1016/j.ensm.2021.06.018, https://doi.org/10.1038/s41560-021-00780-2,https://doi.org/10.1016/j.mattod.2020.01.019 2) A relationship must be established between experimental and theoretical results.Do the theoretical results agree with the experimental ones?If yes, specify in the manuscript.
3) Please the quality of your image should be improved.4) The slight challenges I encountered during the review has to do with the language.The English of the manuscript needs extensive revision.

Detailed Responses to Reviewers' Comments
Reviewer #1: General comment: In this Manuscript, the authors discuss the effect of stabilizing the oxygendefective inert phase on the cathode properties of nickel-rich cathode material from various perspectives, such as bulk structure and surface structure, in addition to electrochemical properties.
The discussion has many very interesting contents, but the reviewer had doubts about the following contents.
Reply: Thanks for your valuable advice and professional comment to help us improving the manuscript.Your suggestions and comments have been carefully considered and addressed, and all the responses are listed in the following section, point by point.In addition, all changes in the revised Manuscript have been highlighted in yellow for your convenience.To elucidate the alleviated electrons transfer initiated from TMs and surface oxygens, the high surface-sensitive soft X-ray absorption spectroscopy (s-XAS) of Ni L3-edge at highly delithiated state (4.5 V, Fig. 1h) was detected and indicated that the Ni 4+ was decreased in P-NCM sample near-surface, manifesting that the bond gap in L-NCM might be regulated 16 .
Revision 2: (On page 7 in the revised Manuscript) To elucidate the alleviated electron transfer between TMs and surface oxygens, the s-XAS of Ni L3-edge with TEY mode at 1 st fully charged state (4.5 V, Fig. 1h) were detected.Based on the standard spectral of NiO, Ni2O3 and NiO2, the Ni 3+ and Ni 4+ were decreased in P-NCM sample near-surface, whereas the content of Ni 2+ was elevated compared with their counterpart, manifesting that the charge transfer in L-NCM near-surface were mitigated 16 .
Addition 1: (On page 11 in the revised Supplementary Information) Supplementary Fig. 10.s-XAS spectra for Ni L3-edge at uncharged state.
Addition 2: (On page 5 in the revised Manuscript) Additionally, the slightly decreased Ni 2+ near L-NCM surface (Supplementary Fig. 10) could induce the mitigated Li + /Ni 2+ cations disorder, consistent with the XPS results.
Addition 3: (On page 22 in the revised Manuscript, in the Physical characterizations section) The standard s-XAS spectral line for Ni 2+ , Ni 3+ and Ni 4+ were obtained by detecting the NiO, Ni2O3 and NiO2 samples.
2. Although the oxygen vacancies are discussed, it is presumed that the oxygen vacancies are affecting other electronic states of oxygen.The difference between P-NCM and L-NCM with EPR and XPS has been debated.If you measure O K-edge spectra using s-XAS, I think you can understand more details.You are measuring Ni L-edge spectra, but are you also measuring O results?DFT calculations have also been carried out, so I think we can understand the details further by discussing them in combination with the results.
Reply: Thanks for your valuable comment.As the reviewer suggested, the O K-edge s-XAS spectra for the uncharged, 1 st charged cycle and 200 th charged cycle samples were measured.
Combined with the XPS, EPR, in-situ DEMS and DFT calculations results, more detailed discussion and comparison have been strengthened in the revised Manuscript.
Addition 1: (On page 10 in the revised Supplementary Information) Supplementary Fig. 9. s-XAS spectra for O K-edge at uncharged state.
Addition 2: (On page 5 in the revised Manuscript) The high surface-sensitive O K-edge X-ray absorption spectroscopy (s-XAS) with total electron yield (TEY, with a detection depth ~ 15 nm) mode could provide the information of oxygen 2p orbital information 16 .As shown in Supplementary Fig. 9, the enhanced pre-edge (~ 529 eV) in uncharged L-NCM corresponding to the decreased charge density around the O ions and illustrating more oxygen vacancies 17 , which could be attributed to the oxygen defect in LMO layer.Furthermore, the high relative intensity of L-NCM electron paramagnetic resonance (EPR) spectroscopy (Fig. 1e) confirmed that the total oxygen vacancies were higher than their pristine counterpart.Additionally, slightly decreased Ni 2+ near L-NCM surface (Supplementary Fig. 10) could induce the mitigated Li + /Ni 2+ cations disorder, consistent with the XPS results.The O K-edge s-XAS spectra for the 1 st charged state (Supplementary Fig. 11a) exhibited that the TM 3d-oxygen 2p rehybridization in P-NCM was elevated, whereas the pre-edge in L-NCM was almost unchanged, demonstrating that the more oxygen vacancies were generated in P-NCM nearsurface and the mitigated oxygen activities in L-NCM, coinciding with the in-DEMS analysis and could be testified by the EPR tests (Supplementary Fig. 11b).Furthermore, the severely enhanced O s-XAS pre-edge and the relative intensity of EPR profile for 200 th charged P-NCM sample illustrated the abundant oxygen vacancies (Supplementary Fig. 13).Nevertheless, the intensities in L-NCM were slightly enhanced compared with the uncharged state, confirmed the decreased oxygen activities after LMO modification.

Reviewer #2:
General comment: The article which I received to review from Dai et al. proposed a strategy of using electron-donating, oxygen-defect-rich La2Mo2O9 layer as surficial protection on lithium metal oxide cathodes to suppress the lattice oxygen evolution and capture it, if generated.This strategy improves the high-voltage cathode stability, as the protection layer mitigates the lattice rearrangement, stress accumulation and particle fracturing due to oxygen release.The results demonstrated improved performance.Many advanced characterization techniques with theoretical simulations verified the improved stability from interface to internal.It is a great work with novel design and decent understanding.But there are many places that remain ambiguous and confusing, which need improvements.I think this work can be published in Nature Communications but after a major revision based on the comments below.
Reply: Thanks for your valuable advice and professional comment to help us improving the manuscript.Your suggestions and comments have been carefully considered and addressed, and all the responses are listed in the following section, point by point.In addition, all changes in the revised Manuscript have been highlighted in yellow for your convenience.
1.The authors observed improved stability from both interfacial and bulk characterizations from the L-NMC sample, while the material is only subjected to a surficial modification (LMO deposition).I think it will be meaningful if the authors can discuss and highlight how interfacial stability can propagate to a bulk structural stability.
Reply: Thanks for your professional suggestion.Actually, the performance degradation of Ni-rich cathode was caused by the cascade reaction of various failure mechanisms.Among them, the caxis collapse at high voltage have been believed to result in severely bulk structural instability.As In this work, the enhanced bulk structural stability of L-NCM could be ascribed to the strong La-O and Mo-O formed in the interface.The La and Mo ions would spontaneously transfer electrons to the coordinate oxygen, reducing its electronic states near the Fermi level Ef and improving the intrinsic stability, which has been proved by the DFT simulations (Fig. 6a-f).
Additionally, the H2-H3 redox peak (Fig. 2b) and c-axis (Fig. 3c) shrinkage of L-NCM was postponed to a higher voltage compared with P-NCM, which is a direct evidence that the interfacial electrons transfer has been involved and thus the decreased TMs 3d-oxygen 2p orbital overlap.Therefore, the LMO layer could not only inhibited the interface failure caused by side reactions through the physical barrier effect, but also weakened the change of lattice c through the electron transport between it with the bulk Ni-rich material, thus improving the bulk stability.For clearly, the corresponding description has been strengthened in the revised Manuscript.
Addition 1: (On page 12 in the revised Manuscript) The enhanced structural stability of L-NCM might be ascribed to the surface electrons transition from La and Mo ions to the coordinate oxygen, elevating the oxygen electronegativities and thus mitigating TMs 3d-oxygen 2p orbital overlap at highly delithiated state, eventually alleviated the lattice collapse resulted by the oxygen release from surface to bulk.
2. Page 5 line 9, the authors need to provide references for XPS peak assignments.And if LMO is highly enriched with O vac., why does the L-NCM vacancy signal only marginally increase in supplementary figure 6.As depth of XPS detection is several nm, the signal of L-NCM should largely originate from LMO.Also, why there is no lattice oxygen from P-NCM.
Reply 1: Thanks for your constructive suggestion, As the reviewer suggested, relevant references for XPS peak assignments have been provided in the revised Manuscript.Furthermore, detailed descriptions for the XPS peak assignments have been strengthened in the revised Supplementary Information.As shown in the fitted XPS spectra, the signals of La and Mo elements appeared in L-NCM surface (Supplementary Fig. 7a, b), which could be assigned to the 3d spin-orbit doublet 1,2 , demonstrating the successful LMO deposition.Furthermore, the ratio of O vacancy located at 532.2 eV was obviously elevated after LMO modification (Supplementary Fig. 7c) 3 , confirming an enriched oxygen vacancy interface were established in L-NCM near-surface.Moreover, the Ni 2p signals could be divided into two peaks at 854.7, and 856.5 eV (the purple is satellite peak, Supplementary Fig. 7d) 4 , which were ascribed to 2p3/2 of Ni 2+ and Ni 3+ cations 4 , respectively.Reply 2: Thanks for your valuable comment.We chose a more suitable baseline to refit the XPS peak and the results shown in the revised Supplementary Fig. 7c, the obviously enhanced oxygen vacancy could be observed in L-NCM surface, which could be attributed to the LMO deposition The high surface-sensitive O K-edge X-ray absorption spectroscopy (s-XAS) with total electron yield (TEY, with a detection depth ~ 15 nm) mode could provide the information of oxygen 2p orbital information 16 .As shown in Supplementary Fig. 9, the enhanced pre-edge (~ 529 eV) in uncharged L-NCM corresponding to the decreased charge density around the O ions and illustrate more oxygen vacancies 17 , which could be attributed to the intrinsic oxygen defect in LMO layer.
Furthermore, the high relative intensity of L-NCM electron paramagnetic resonance (EPR) spectroscopy (Fig. 1e) confirmed that the total oxygen vacancies were higher than their pristine counterpart.Additionally, slightly decreased Ni 2+ near L-NCM surface (Supplementary Fig. 10) could induce the mitigated Li + /Ni 2+ cations disorder, consistent with the XPS results.The O K-edge s-XAS spectra for the 1 st charged state (Supplementary Fig. 11a) exhibited that the TM 3d-oxygen 2p rehybridization in P-NCM was elevated, whereas the pre-edge in L-NCM was almost unchanged, demonstrating that the more oxygen vacancies were generated in P-NCM nearsurface and the mitigated oxygen activities in L-NCM, coinciding with the in-DEMS analysis and could be testified by the EPR tests (Supplementary Fig. 11b).Furthermore, the severely enhanced O s-XAS pre-edge and the relative intensity of EPR profile for 200 th charged P-NCM sample illustrated the abundant oxygen vacancies (Supplementary Fig. 13).Nevertheless, the intensities in L-NCM were slightly enhanced compared with the uncharged state, confirmed the decreased oxygen activities after LMO modification.
Reply 3: In the refitted XPS spectra, the surface oxygen (Li2CO3 /LiOH) in P-NCM surface was elevated, whereas the lattice oxygen was evidently mitigated compared with the modified sample.
In this detection depth (~ 5 nm), the more relative content of surface oxygen in P-NCM was ascribed to the intrinsic residual lithium (Cho et al.Adv.Mater.2018, 5, 30) in Ni-rich material, and the decreased content in L-NCM surface could be attributed to the alcohol cleaning effect during the modification process (Arumugam et al.ACS Energy Lett. 2021, 6, 941).To confirm the alleviated residual lithium species in L-NCM, a well-designed neutralization titration experiment has been carried out, the results unambiguously exhibited the decreased residual lithium in L-NCM sample.For clearly, the corresponding results and descriptions have been strengthened in the modified Manuscript and Supplementary Information.
Addition 1: (On page 9 in the revised Supplementary Information) appropriate, and all the inappropriate corresponding description have been corrected in the revised Manuscript.Furthermore, corresponding literatures have been added to strengthen the description.
Origin 1: (On page 5 in the original Manuscript) resulting in the electrons transport to oxygen and thus the gas liberation would be happened.
Revision 1: (On page 5 in the revised Manuscript) resulting in the electrons transport from oxygen and thus the gas liberation would be happened.Reply 2: Thanks for your professional reminding.As the reviewer suggested, the "bond" there have been revised as "band".Furthermore, all the inappropriate corresponding description have been corrected in the revised Manuscript.Reply: Thanks for your kind reminding.As the reviewer recommend, the detailed sample preparations for all the characterizations have been strengthened in the revised Manuscript.
Origin 1: (On page 22 in the original Manuscript) Crystal structural was monitored by X-ray diffraction (XRD, Bruker D8 Advance) and quantified by Rietveld refinement (Fullprof soft-ware).
Revision 1: (On page 22 in the revised Manuscript) Crystal structural was monitored by X-ray diffraction (XRD, Bruker D8 Advance) with Cu-Kα radiation at a scan increment of 0.020°, wherein the sample were pressed and flat on a high-purity quartz wafer, then the crystal structural was quantified by Rietveld refinement (Fullprof soft-ware).
Origin 2: (On page 22 in the original Manuscript) In-situ XRD test was performed in the scanning range of 10-55º with Be window.
Revision 2: (On page 22 in the revised Manuscript) For in-situ XRD characterization, the slurry was firstly coated and dried on a beryllium window (for X-ray penetration), whereafter assembled into a Bruker specially made chamber to carried out the test with the increment of 0.020º in the scanning range of 10-55º.As for scanning electron microscopy (SEM) characterizations, the samples were stick directly to conductive adhesive for testing.Whereas in transmission electron microscopy (TEM) detections, the materials were firstly dispersed in alcohol and then drop into carbon-based porous film, the tests could be proceeded until its completely dried.
6.The coulombic efficiency must be included in Fig. 2g-i as they are direct indicatives of the cathode side reaction extents, especially at high voltage.
Reply: Thanks for your constructive suggestion.As the reviewer suggested, the coulombic efficiency has been included in the revised Fig. 2g-i 18b.Actually, the red peak (687.1 eV) was more properly assigned to C-F bonds and could be ascribed to the PVDF binder deposited on electrode surface, thus their relative amount for analyze the electrolyte decomposition could be ignored.The green (685.2 eV) and purple (683.8 eV) peaks were index to the LixPOyFz/LixPFy and LiF, respectively, which were derived from the parasitic reactions at the electrode/electrolyte interface and were widely identified as the components of CEI films.
Therefore, the almost disappeared LixPOyFz/LixPFy and LiF peaks in L-NCM surface compared with P-NCM could be demonstrated the mitigated electrolyte decomposition.
As discussed and analyzed in the preceding text, relevant clearly description and graphs have been accordingly added and revised in the revised Supplementary Information.
Origin: (On page 19 in the Supplementary Information) Revision: (On page 24 in the revised Supplementary Information) Addition 1: (On page 24 in the Supplementary Information) Additionally, as shown in Supplementary Fig. 23b, the LiF (684.3 eV) and LixPOyFz/LixPFy (685.2 eV) in F 1s peaks were derived from the parasitic reactions at the electrode/electrolyte interface and were identified as the components of cathode-electrolyte interface (CEI) 7,8 .The C-F (687.1 eV) bonds could be ascribed to the PVDF binder deposited on electrode surface.Therefore, the almost disappeared LixPOyFz/LixPFy and LiF peaks in L-NCM surface compared with P-NCM demonstrated the mitigated electrolyte decomposition, coinciding with abovementioned C 1s peaks analysis.Reply 2: The OCO2 could be also denoted as CO3, according to the in-depth analysis for the Reply 2: Based on above analysis, as described in the original Manuscript (page 16, line 12), the EXAFS and EXAFS results (Fig. 5a-d) illuminated the overall valence of Ni element and the interaction between Ni and other elements (O, Co, Mn) after repeat cycles at fully charged state.
However, due to the heterogeneous reaction inside electrode particles and the connection between various failure mechanisms, multi-scale (from surface to bulk) characterizations should be simultaneously carried out.Therefore, the s-XAS spectra with TEY mode (with a detection depth ~ 15 nm) have been employed (Fig. 1h, Supplementary Fig. 9-11, Supplementary Fig. 13) to elucidated the near-surface coordination environment.Furthermore, the TOF-SIMS (Fig. 4a-f) and HAADF-STEM (Fig. 5g-l) characterizations were also applied to illuminate the surface and the surface-to-bulk chemical environments in this work.As a result, combined the series of characterizations and theoretical simulations, the mechanism of LMO modifications on Ni-rich material could be effectively elucidated.To clarify the XANES and EXAFS were revealed the overall valence state of Ni element, the corresponding description has been carefully clarified in the revised Manuscript.
Origin: (On page 16 in the original Manuscript) Therefore, X-ray absorption near edge structure (XANES) spectra were collected to investigate the overall Ni valence state and the coordination environment (Fig. 5a, b).
Revision: (On page 16 in the revised Manuscript) X-ray absorption near edge structure (XANES) technique with a high energy hard X-ray could be facilely penetrating the Ni-rich materials 28 , thus was employed to investigate the overall Ni valence state and the coordination environment (Fig. 5a, b).

Reviewer #3:
Reply: Thanks for your valuable advice and professional comment to help us improving the manuscript.Your suggestions and comments have been carefully considered and addressed, and all the responses are listed in the following section, point by point.In addition, all changes in the revised Manuscript have been highlighted in yellow for your convenience.
1) The manuscript reports an importance class of cathode materials in the field of Lithium-ion battery, with detailed and very insightful experimental and computational investigations.The results show clearly that the use of lanthanum molybdate improves the properties of P-NCM.
Reply: Thanks for your positive comment.As the reviewer suggested, the electrochemical performance of L-NCM in the present study have been compared with the reviewer suggested and the similar-focused studies to highlight the importance, which was found superior than the reported literatures.For clearly, the corresponding description and comparison were complemented, and the reviewer suggested as well as the similar-focused literatures have been added in the revised Manuscript and Supplementary Information.
Addition 1: (On page 10 in the revised Manuscript) and was found superior compared with the recent similar-focused studies (Supplementary Table 4).according to the demand of Nature Communications editorial office, if this Manuscript could be accepted, the highly-quality vector images should be submitting individually for the final publications.
4) The slight challenges I encountered during the review has to do with the language.The English of the manuscript needs extensive revision.
Reply: Thanks for your constructive suggestion.As the reviewer suggested, the English of this Manuscript has been carefully revised and highlighted in yellow color for your convenience (The revisions have been presented in the revised Manuscript).

REVIEWERS' COMMENTS
Reviewer #2 (Remarks to the Author): I believe the authors did a great job revising the manuscript.The additional experiments and discussions provided thorough answers to my comments.The quality of this manuscript was dramatically improved by the careful revision from the authors.I don't have any further questions.I recommend the publication of this revised manuscript in Nature Communications.
Reviewer #4 (Remarks to the Author): I suppose the author has done a great job.I feel like it can be accepted directly.The responses have appropriately addressed those concerns from referee 1.
Fig. 1 (h).The authors claim that Ni4+  is decreasing based on this result, but in addition to the initial results, I think that necessary information such as the shape of the Ni 3+ spectrum is lacking.

Origin 1 :
(On page 6 in the original Manuscript) Revision 1: (On page 6 in the revised Manuscript) Origin 2: (On page 7 in the original Manuscript)

Addition 3 :
(On page 25 in the revised Manuscript) 16 Lin, F. et al.Synchrotron X-ray analytical techniques for studying materials electrochemistry in rechargeable batteries.Chem.Rev. 117, 13123 (2017).17 Lin, F. et al.Phase evolution for conversion reaction electrodes in lithium-ion batteries.Nat.Commun.5, 3358 (2014).Addition 4: (On page 12 in the revised Supplementary Information) Supplementary Fig. 11. a s-XAS spectra for O K-edge at 1 st charged state.b EPR profile at 1 st charged state.Addition 5: (On page 7 in the revised Manuscript)

Addition 6 :
(On page 13 in the revised Supplementary Information) Supplementary Fig. 13. a s-XAS spectra for O K-edge at 200 th charged sate.b EPR profile at 200 th charged state.Addition 7: (On page 7 in the revised Manuscript) widely reported in previous literatures (e.g., Peter et al.Nat.Chem.2016, 8, 684; Meng et al.Nat.Rev. Mater.2022, 7, 522), the shrinkage of lattice c in layered materials at highly delithiated state could be attributed to the rehybridization of high valence transition metal ions (TMs, particularly for Ni 4+ in Ni-rich material) with oxygen.In this process, the high valence and strong oxidizing TMs would receive electrons from the coordinate oxygen, promoting the oxygen p orbitals approaching to the Fermi level Ef, which leading to the TMs 3d-oxygen 2p orbital overlap and thus the oxygen instability.The oxygen release in layered material would decrease the coulomb repulsion of oxygen plane in LiO layer, thus resulting in the c-axis shrinkage, and it was generally believed that the oxygen release was initiated from surface and extended to the bulk (e.g., Sun et al.Adv.Energy Mater. 2022, 2200569; Wang et al.Nat.Commun.2018, 9, 2437).Therefore, the suppression of oxygen release from the surface could effectively improve the bulk stability of Nirich material.

(
enriched oxygen vacancy) as the depth of XPS detection in this work is ~ 5 nm (detection depth for this device are 5-10 nm).Furthermore, the O K-edge s-XAS (detection depth: ~ 15 nm) and EPR (could reflect the total oxygen vacancy) spectra for the uncharged, 1 st charged cycle and 200 th charged cycle samples were measured.Combined with the XPS, EPR and in-situ DEMS results, more detailed discussion and comparison of oxygen vacancies in L-NCM and P-NCM have been strengthened in the revised Manuscript.Origin 1: (On page 7 in the original Supplementary Information) Revision 1: (On page 8 in the revised Supplementary Information) Addition 1: (On page 5 in the revised Manuscript) which might originate from the LMO (enriched oxygen defect) layer.Addition 2: (On page 10 in the revised Supplementary Information) Supplementary Fig. 9. s-XAS spectra for O K-edge at uncharged state.Addition 3: (On page 5 in the revised Manuscript)

Addition 4 :
(On page X in the revised Manuscript) 16 Lin, F. et al.Synchrotron X-ray analytical techniques for studying materials electrochemistry in rechargeable batteries.Chem.Rev. 117, 13123 (2017).17 Lin, F. et al.Phase evolution for conversion reaction electrodes in lithium-ion batteries.Nat.Commun.5, 3358 (2014).Addition 5: (On page 12 in the revised Supplementary Information) Supplementary Fig. 11. a s-XAS spectra for O K-edge at 1st charged state.b EPR profile at 1st charged state.Addition 6: (On page 7 in the revised Manuscript)

Addition 7 :
(On page 13 in the revised Supplementary Information) Supplementary Fig. 13. a s-XAS spectra for O K-edge at 200th charged sate.b EPR profile at 200th charged state.Addition 8: (On page 7 in the revised Manuscript)

Origin 2 :
(On page 25 in the original Manuscript) was primarily ascribed to the electrons transferred from high valence TMs with the coordinated oxygen.Revision 2: (On page 25 in the revised Manuscript) was primarily ascribed to the high valence TMs received electrons from the coordinated oxygen 19,20 .Addition: (On page X in the revised Manuscript) 19 Liu, X. et al.Origin and regulation of oxygen redox instability in high-voltage battery cathodes.Nat.Energy 7, 808-818 (2022).20 Wang, C. et al.Resolving complex intralayer transition motifs in high-Ni-content layered cathode materials for lithium-ion batteries.Nat.Mater.22, 235-241 (2023).

Origin 1 :
(On page 5 in the original Manuscript) the bottom of TMs 3d bond might be contact with the oxygen 2p bond.Revision 1: (On page 5 in the revised Manuscript) the bottom of TMs 3d band might be contact with the oxygen 2p band.Origin 2: (On page 2 in the original Manuscript) when it contacts with the bond of lattice oxygen.Revision 2: (On page 2 in the revised Manuscript) when it contacts with the band of lattice oxygen.4. Figure 1c EDS, why do the La and Mo signals completely overlap with Ni-Co-Mn, if the LMO is surficial deposition?Reply: Thanks for your meticulous comment.The EDS mapping images in Fig. 1c were obtained by the energy spectrum of surface distribution, thus the uniformed La and Mo signals has been detected in the surface (overlap with Ni-Co-Mn).To demonstrate the LMO compound were only deposited on L-NCM surface, a focused ion beam etching combined with scanning electron microscope (FIB-SEM) technique was employed.The cross-sectional mapping images shown in the following Fig. (added as Supplementary Fig. 6 in the revised Supplementary Information)unambiguously demonstrated that the LMO is surficial deposition.To clarify more clearly, the corresponding result and explanation has been strengthened in the revised Manuscript and Supplementary Information.

Addition 1 :
(On page 4 in the revised Manuscript) Specially, cross-section morphology of L-NCM obtained by focused ion beam etching combined with SEM (FIB-SEM) and the corresponding energy dispersive spectra (EDS) mapping images (Supplementary Fig. 6) demonstrated that La and Mo elements were uniformly distributed on the materials surface, illuminating the homogeneous LMO surface deposition.Addition 2: (On page 7 in the revised Supplementary Information) Supplementary Fig. 6.Cross-section morphology and the corresponding EDS mapping images for L-NCM, scale bars, 3 μm. 5.There is overall very little information on sample preparations for nearly all the characterizations.

Origin 3 :
(On page 22 in the original Manuscript) In-situ heating XRD (HT-XRD) was carried out on delithiated electrodes with the temperature elevated from 25 to 600 °C.Revision 3: (On page 22 in the revised Manuscript) In-situ heating XRD (HT-XRD) was carried out with the increment of 0.020º in the scanning range of 10-70º for the disassembled delithiated (4.5 V) electrodes with the temperature elevated from 25 to 600 °C.Origin 4: (On page 22 in the original Manuscript) Chemical environments were detected by X-ray photoelectron spectroscopy (XPS, PHI 5000 Versa Probe-III), X-ray absorption near edge structure (XANES, Shanghai Synchrotron Radiation Facility), soft X-ray absorption spectroscopy (s-XAS, Hefei, National synchrotron radiation Laboratory), postmortem electron paramagnetic resonance (EPR, Bruker A300-10), and time-offlight secondary ion mass spectroscopy (TOF-SIMS, PHI Nano Tof I).

Revision 4 :
(On page 22 in the original Manuscript) Chemical environments were detected by X-ray photoelectron spectroscopy (XPS, PHI 5000 Versa Probe-III) and calibrated with C 1s posited at 284.8 eV.The argon-ion etching for Li metal anode in-depth XPS characterizations were corresponding to 1 s ~ 100 nm.The fine structure for the original powers and cycled electrodes (disassemble the coin-cell) were measured by soft Xray absorption spectroscopy (s-XAS, Hefei, National Synchrotron Radiation Laboratory) in total electron yield mode (TEY, with a detection depth ~ 15 nm), postmortem electron paramagnetic resonance (EPR, Bruker A300-10), and high-energy X-ray absorption near edge structure (XANES, Shanghai, Synchrotron Radiation Facility).The cycled cathodes (disassemble the coincell) surface chemical compositions were then identified by time-of-flight secondary ion mass spectroscopy (TOF-SIMS, PHI Nano Tof I).Addition 1: (On page 22 in the revised Manuscript) focused ion beam etching combined with SEM technique (FIB-SEM) Addition 2: (On page 22 in the revised Manuscript)

.
Origin: (On page 8 in the original Manuscript) Revision: (On page 9 in the revised Manuscript) 7. Supplementary Fig 18.The LiF from L-NCM decreased, but the other F-containing compound largely increased.How did the authors conclude mitigated electrolyte decomposition from it?And why is there a large increase in the OCO2 signal from P-NCM? Reply 1: Thanks for your careful review.After referring the literatures (e.g., Jiang et al.Nat.Commun.2021, 12, 4564; Lucht et al.Energy Environ.Sci.2016, 9, 1308), the F-contained XPS spectra have been re-fitted and shown in the following revised Supplementary Fig.
Revision: (On page 25 in the revised Supplementary Information) 9.The SEM Fig.4g, h and the discussions are very misleading.First, it's very unlikely that any SEI can be observed at such magnification.The SEM images here can only show the Li deposition morphology.The top-view even needs zoon-in for just observing detailed Li morphology.Second, the LMA cycled in the carbonate electrolyte that the authors use in this work is highly impossible to deliver smooth deposition, even without any interference from cathode.The 4h-right figuredoes not indicate the SEI information.Instead, the observed layer is the porous Li deposition after long-term LMA cycling.Therefore, the smooth surface of 4h-left does not make sense.Here I do not suspect that mitigating the TM crosstalk can improve the Li deposition.But better images are needed with correct interpretations.Reply 1: Thanks for your very professional comment.As the reviewer suggested, the SEM images with appropriate magnifications have been provided to clearly identify the SEI layer.Furthermore, the top-view has been zooned-in and the results were displayed as an inset in the Top-view images.The results unambiguously revealed the detailed Li morphology.Original: (On page 12 in the revised Manuscript) g, h Top-view, and cross-sectional morphology images of LMA, scale bars, 100 μm.(g) coupled with P-NCM and (h) coupled with L-NCM.Revision: (On page 13 in the revised Manuscript) g Top-view (left, scale bars, 20 μm) and cross-sectional morphology (right, scale bars, 5 μm) images of LMA coupled with P-NCM.h Top-view (left, scale bars, 20 μm) and cross-sectional morphology (right, scale bars, 5 μm) images of LMA coupled with L-NCM.Reply 2: Thanks for your very careful reviewing.The electrolyte in this work was purchased by Shandong Hirong Power Supply Material Co., LTD.As the reviewer mentioned that the carbonate electrolyte (ethylene/diethyl carbonate=3:7 in volume ratio) in this work is impossible to deliver smooth deposition, we reconfirmed that the electrolyte contained 3 wt% fluoroethylene carbonate (FEC) as an additive with the manufacturer.Therefore, the uniformed SEI layer in LMA surface could be attributed that the FEC compound facilitated the homogeneous deposition of Li metal (Zhang et al.Angew.Chem.Int.Ed. 2020, 59, 3252, Fig. 2).As established in the previous literature (Cho et al.Nat.Energy 2021, 6, 362, Fig. 5), the dissolved TMs from Ni-rich cathode could deposit on the LMA surface, which would impede the Li deposition and affect the morphology and electrochemical performance.Therefore, the smooth LMA surface for those paired with L-NCM demonstrated that the LMO depositor has been effectivity mitigated the TMs dissolution, corresponding to the excellent electrochemical performances.Addition 1: (On page 22 in the revised Manuscript) and 3 wt% fluoroethylene carbonate (FEC) Addition 2: (On page 16 and 24 in the revised Manuscript) 3 Yoon, M. et al.Reactive boride infusion stabilizes Ni-rich cathodes for lithium-ion batteries.Nat.Energy 6, 362-371 (2021).10.What's the depth of detection from XANES and EXAFS used in this work?Are they suitable for detecting surficial changes without being affected by bulk information?Reply 1: Thanks for your careful reviewing.The Ni XANES and EXAFS profiles in this work were detected from Shanghai Synchrotron Radiation Facility with hard X-ray and the energy range of 4000 ~ 23000 eV.Such a high energy could be facilely penetrating the Ni-rich materials, thus the XANES and EXAFS profiles revealed the overall element valence state, which has been widely established in previous literatures (e.g., Xin et al.Nature 2022, 6, 610; Lu et al.Nat.Commun.2022, 13, 2319).
Addition: (On page 26 in the revised Manuscript) 28 Li, S. et al.Mutual modulation between surface chemistry and bulk microstructure within secondary particles of nickel-rich layered oxides.Nat.Commun.11, 4433 (2020).11.Figure5i.Where is the LMO deposition layer which is supposed to be on the NCM surface with the thickness at around 5 nm as indicated in Fig.1c?Reply 1: Thanks for your careful reviewing.The accelerating voltage applied for HR-TEM test in Fig. 1c was ~ 200 kV (voltage range for this device are 20 -200 kV), whereas for HAADF-STEM in Fig. 5i was ~ 280 kV (voltage range: 60 -300 kV).Therefore, the almost disappeared LMO layer in NCM surface (Fig. 5i) might be attributed to the high energy electrons bombardment, resulting in the chemical bonds breakage between the bulk NCM and LMO layer (e.g., Mary et al.Sci.Adv.2023, 9, 3285; Nie et al.Nat.Commun.2019, 10, 3243).To obtain the LMO layer involved in L-NCM HAADF-STEM image, the accelerating voltage was decreased to 200 kV, the result shown in the revised Fig. 5i clearly demonstrated that the LMO was still deposited on the cycled L-NCM surface.For consistency, the HAADF-STEM image for cycled P-NCM was also carried out with an accelerating voltage of 200 kV, and the corresponding images and descriptions have been strengthened in the revised Manuscript.Origin: (On page 15 in the revised Manuscript) Addition 1: (On page 19 in the revised Manuscript) Furthermore, the intact LMO shielding layer with a P123 space group were tightly attached to its surface and proved by FFT 32 .Addition 2: (On page 26 in the revised Manuscript) 32 Goutenoire, F. et al.Crystal structure of La2Mo2O9, a new fast oxide-ion conductor.Chem.Mater.12, 2575 (2000).
Addition 2: (On page 35 in the revised Supplementary Information) Supplementary Table4.Comparison in electrochemical performances of L-NCM on different voltages with the recent similar-focused literatures.