Boosting Electrochemical Performances of Li-Rich Mn-Based Cathode Materials by La Doping via Enhanced Structural Stability

Comments 1: In this manuscript, the author has successfully synthesized La-doped Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ cathode materials by a sol-gel method, which shows its effectiveness in LIBs. Different characterization techniques, including XRD, XPS, TEM, and electrochemical measurements, are used to study the structural, morphological, and electrochemical properties of the materials. La-doped electrode provides a higher I(003)/I(104) ratio, further reflecting well-ordered layered structures compared with the electrode without La. SEM images show that the samples consist of lamellar-like particles with rough surfaces. TEM analysis also shows that the TM spacing increases with La³⁺ doping. From battery characteristics, it has been observed that the capacity retention was enhanced from 54.4% to 87.8% with a 100 mA g^-1 current density value after 100 cycles for the pristine and doped La with 1/100 samples. When compared with the pristine material, the La-doped electrode shows a decrease in crystal lattice change during the charge-discharge process, increasing specific capacity. La-based samples provide lower Rct values evaluated from impedance analysis, confirming the modification effect of La³⁺ to the LRMO sample. This methodology is highly crucial for developing lithium-rich Mn-based layered cathode materials and can act as an alternative to traditional cathodic materials. Therefore, I recommend the acceptance of this paper. I recommend revising the abstract and conclusion, as they currently lack clear insights into the main findings of the paper.

Response 1: Thank you for your recognition of our work and for pointing out our shortcomings in this article, we have made modifications according to your comments.

Abstract: La-doped Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ cathode materials were successfully synthesized by sol-gel method. The structure, morphology, elements valence states, cyclic voltammetry, cyclic properties were characterized to investigate the properties of the synthesized materials. The as-prepared La-doped Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ materials exhibit well crystalline hexagonal layered structures with lamellar-like particles featuring a rough surface. The optimal sample, designated as LLRMO-2 with 1/100 La³⁺ doping, delivers an impressive discharge capacity of 271.2 mAh g^-1 with capacity retention of 87.8 % after 100 cycles at the current density of 100 mA g^-1 compared with that of 203.5 mAh g^-1 with only 110.6 mAh g^-1 after 100 cycles for the pristine sample. Furthermore, the LLRMO-2 cathode exhibits superior rate capability compared to the pristine sample and shows excellent cyclic performances with the capacity retention of 48.1% after 400 cycles. The voltage decay per cycle is only 1.60 mV, less than 3.70 mV of the pristine one. The enhanced capacity, rate capability and cyclic performance observed in La-doped Li-rich layered cathode can be attributed to the improved structural stability as well as higher diffusion coefficient of lithium ions. This results suggested that the strategy of introducing La³⁺ into the transition metal slabs is an efficient approach for boosting electrochemical performances of Li-rich Mn-based cathode materials via enhancing structural stability.

Conclusion: The doping of the La³⁺ ions in the Li-rich Mn-based cathode materials was achieved by a simple sol-gel method, significantly enhancing cyclic stability. Various characterization techniques including XRD, XPS, TEM, and electrochemical measurements, are employed to investigate the structure, morphology and electrochemical properties of the materials. The Rietveld refinement results of the parameters of the La doped samples are larger than those of pristine sample. And the increased interatomic layer spacing facilitates lithium ion diffusion, thereby improving rate capability and cyclic stability. Notably, the capacity retention improved from 54.4% to 87.8% at the current density of 100 mA g^-1 after 100 cycles for the pristine and doped La with 1/100 samples. Specially, the LLRMO-2 shows 48.1% capacity retention after 400 cycles. With the increased of current density, the doping effect gets more noticeable. At the high discharge rate of 800 mA g^-1 and 1000 mA g^-1, LLRMO-2 delivers impressive capacities of 155.3 and 138.9 mAh g^-1, respectively, in contrast to the capacity of 127.8 and 103.3 mAh g^-1 for pristine material. Furthermore, compared to the pristine material, the La-doped cathode material exhibits reduced crystal lattice change during charge-discharge process and enhanced the structural stability. Simultaneously, La-doped samples exhibit significantly lower charge transfer resistances and higher Li⁺ diffusion coefficient compared to the pristine sample. Therefore, the sol-gel strategy for La doping is crucial for designing next-generation high-performance lithium-rich Mn-based layered cathode materials.

Comments 1: The article manuscript entitled “Boosting electrochemical performances of Li-rich Mn-based 2 cathode materials by La doping via enhanced structural stability” is good and of interest manuscript, but before publishing some modifications are necessary.

Turnitin find a 40% similarity of the text, that’s too big.

Response 1: Thank you very much for the suggestion. And we have modified the We have modified the parts with high repetition rate, and the Revised portion are marked in red in the the revised manuscript.

Comments 2:  Nothing is mentioned about the economic aspects of incorporating La into NMC. Is such an addition justified? Please address this topic.

Response 2: It can be seen from the literature reported and our work that the La doping strategy has been used to improve the performance of lithium-rich cathode materials. Appropriate amount of La doping can significantly improve the cyclibility and rate capability of the cathode material by stabilizing the crystal structure, inhibiting the voltage fading and enhancing diffusion coefficient of lithium ions. Although lanthanum as a rare earth element is rather expensive , the enhanced capacity, rate capability and cyclic performance observed in La-doped Li-rich layered cathode can extend the service of lithium batteries and has certain economic benefits, which can reduce the adverse factor of high price brought by lanthanum.

Comments 3: Is Lanthanum for the first time studied in this article?

Response 3: This is not the first time for the La-doped in the Li-rich cathode materials. However, the electrochemical performances of the layered cathode materials doped with La3+ prepared in this work and reported in the literature were compared and the results are illustrated in Table 3 in the revised manuscript. It can be found that the La-doped lithium-rich layered oxides synthesized with sol-gel method in this work do have advantages in cyclic performance.

Comments 4: Is the experimental synthesis new?

Response 4: La was proposed as a dopant in Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ (LRMO) to enhance the electrochemical performances through a facile sol-gel method. Though it is not a new method, it does not require inert gas protection or the preparation of precursors. The layered cathodes can be successfully synthesized through simple evaporation concentration and subsequent calcination process, saving energy and time over other synthesis methods.

Comments 5: Please explain, evidence the novelty in this manuscript. If is already in the manuscript, please evidence it.

Response 5: Thanks for pointing the novelty issues. In this work, La was proposed as a dopant in Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ to enhance the electrochemical performances through a facile sol-gel method, which does not require inert gas protection or the preparation of precursors. The layered cathodes can be successfully synthesized through simple evaporation concentration and subsequent calcination process, saving energy and time over other synthesis methods. The Rietveld refinement results of the parameters of the La doped samples are larger than those of pristine sample. And the increased interatomic layer spacing facilitates lithium ion diffusion, thereby improving rate capability and cyclic stability. Notably, the capacity retention improved from 54.4% to 87.8% at the current density of 100 mA g^-1 after 100 cycles for the pristine and doped La with 1/100 samples. Specially, the LLRMO-2 shows 48.1% capacity retention after 400 cycles. With the increased of current density, the doping effect gets more noticeable. At the high discharge rate of 800 mA g^-1 and 1000 mA g^-1, LLRMO-2 delivers impressive capacities of 155.3 and 138.9 mAh g^-1, respectively, in contrast to the capacity of 127.8 and 103.3 mAh g^-1 for pristine material. Furthermore, compared to the pristine material, the La-doped cathode material exhibits reduced crystal lattice change during charge-discharge process and enhanced the structural stability. Simultaneously, La-doped samples exhibit significantly lower charge transfer resistances and higher Li⁺ diffusion coefficient compared to the pristine sample.

Comments 6: The citrat method is rather old, can you give credit to literature?

Response 6: Citric as a chelating agent is widely used in the sol-gel method to synthesize cathode materials for lithium-ion batteries. Although the sol-gel method is rather old, it still used in the literature in recent years, such DL-lactic acid (https://doi.org/10.1016/j.ceramint.2020.10.205), EDTA, glycine and citric acid as complexing agents (https://doi.org/10.20964/2017.01.29), bio-derived natural agar (https://doi.org/10.1016/j.ceramint.2019.03.128), and citric acid (https://doi.org/10.1016/j.jelechem.2022.116762) and so on because it does not require inert gas protection or the preparation of precursors, through simple evaporation concentration and subsequent calcination process, saving energy and time over other synthesis methods.

Comments 7: “When comparing the intensity 141 ratio of I(003)/I(104) for both the pristine LRMO and LLRMO, it is evident that the La-142 doped cathode exhibits a higher I(003)/I(104) ratio, signifying that well-ordered layered 143 structures have been effectively preserved after cation doping [43]. “ Please consider the literature and check if the intensity ratio between this peaks is due to the doping or to the citrate precursor, or to the thermal treatment.

Response 7: Thank you for your valuable advise. concerning the (003)/(104) intensity ratio, we have made detailed analysis through experimental data. In this study, we designed a series comparative experiments with the same amount of citric acid, the same calcination conditions, and different amounts of La doping. The results showed that with the increasing amounts of the La doping cathode exhibits a enlargement I(003)/I(104) ratio. Since all samples prepared using the same citric acid precursor and calcination conditions, it can be clearly illustrated that the the La doping is the dominant factor causing this change.

Comments 8: Please remove the reference which are not related to this study.

Response 8: Thank you for pointing out the problem of the references. We have carefully reviewed the full text of the references and removed those irrelated to the content in this work.