The Technologies of Electrochemical Lithium Extraction Process from Lithium-Containing Solutions
Sasaki Kazuya
Zhenyu Zhang
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsGeneral comments
This review of the latest research on electrochemical lithium extraction processes is useful as a promising candidate technology for economically obtaining large amounts of lithium resources, which are consumed in large quantities by lithium-ion batteries, which are rapidly becoming popular as energy storage systems for electric vehicles, drones, robots, and new power supply systems with demand response. However, this manuscript has important issues that need to be improved in order to be published in this journal, as described in the Specific Comments.
Specific Comments
The introduction should explain more carefully and specifically why there is an urgent need for technological development for lithium resource extraction and recovery. The value of the research should be concretely demonstrated by referring to the future prospects for lithium resources with reference to the efforts of the US DOE and EU battery regulations.
The mention of the characteristics of the research introduced should be more detailed. At the very least, the purity of the lithium obtained should be mentioned.
The authors classified many of the studies into Electrochemical Deintercalation Method, Electrochemical ion pump, and Electrodialysis method, but the definitions of these classifications are unclear. They should be properly defined at the beginning and then classified. In this field, electrochemical ion pumps and electrodialysis are often treated as synonymous terms representing the same field, so a strict definition is necessary to avoid confusion.
There are some parts where the cited figures and the text do not match. For example, Figure 5 is cited as a figure of a two-power supply three-electrode electrochemical pumping system by Sasaki, K. et al. (reference number 40), but this citation is incorrect. It is a figure from a reference by Li, Z. et al. (reference number 41) that is unrelated to this newly designed system.
Only 51 papers are introduced, and many important reports that should be reported are missing. For example, the works of Kunugi, S., et al., Shin-mura, K., et al., and Hoshino. T., et al. on electrodialysis (electrochemical pumping) using LLTO should be covered.
Author Response
Reviewer #1: This review of the latest research on electrochemical lithium extraction processes is useful as a promising candidate technology for economically obtaining large amounts of lithium resources, which are consumed in large quantities by lithium-ion batteries, which are rapidly becoming popular as energy storage systems for electric vehicles, drones, robots, and new power supply systems with demand response. However, this manuscript has important issues that need to be improved in order to be published in this journal, as described in the Specific Comments.
- The introduction should explain more carefully and specifically why there is an urgent need for technological development for lithium resource extraction and recovery. The value of the research should be concretely demonstrated by referring to the future prospects for lithium resources with reference to the efforts of the US DOE and EU battery regulations.
Reply & Revision: Thank you for your suggestion. We have added the future prospects for lithium resources with reference to the efforts of the US DOE and EU battery regulations. The added content in introduction is as follows:
According to European battery regulation (2023) and The United States Department of Energy of Resource Recycling Policy: In view of the strategic importance of batteries, it is necessary to set out rules on the sustainability, performance, safety, collection, lithium recycling and second life of batteries. It is important to create a harmonized regulatory framework for dealing with the recovery rate, purity of lithium compound and costing of batteries that are placed on the market in the Union.
- The mention of the characteristics of the research introduced should be more detailed. At the very least, the purity of the lithium obtained should be mentioned.
Reply & Revision: Thank you very much for your valuable suggestion. The detailed of recovery rate and purity of the lithium compound is added in manuscript.
- The authors classified many of the studies into Electrochemical Deintercalation Method, Electrochemical ion pump, and Electrodialysis method, but the definitions of these classifications are unclear. They should be properly defined at the beginning and then classified. In this field, electrochemical ion pumps and electrodialysis are often treated as synonymous terms representing the same field, so a strict definition is necessary to avoid confusion.
Reply & Revision: Thank you very much for pointing it out. Electrochemical Deintercalation Method is using ion intercalation of electrode materials and achieving directional enrichment of lithium, such as LiFePO4/FePO4 electrolytic cell. Electrochemical ion pump is a technology with the positive and negative electrode chemical reaction, while the cation and cation ions are adsorbed on the corresponding electrodes. Electrodialysis method is that an electric filed driving ions migration across the membranes to achieve the enrichment of target ions. The definition has been added in manuscript.
- There are some parts where the cited figures and the text do not match. For example, Figure 5 is cited as a figure of a two-power supply three-electrode electrochemical pumping system by Sasaki, K. et al. (reference number 40), but this citation is incorrect. It is a figure from a reference by Li, Z. et al. (reference number 41) that is unrelated to this newly designed system.
Reply & Revision: Thank you very much for pointing it out. The reference number of Figure 5 has been modified, and the full manuscript has been checked.
- Only 51 papers are introduced, and many important reports that should be reported are missing. For example, the works of Kunugi, S., et al., Shin-mura, K., et al., and Hoshino. T., et al. on electrodialysis (electrochemical pumping) using LLTO should be covered.
Reply & Revision: Thank you for your helpful comments. The application of LLTO in electrochemical pumping is extensive, and its working principle remains consistent across different studies. Therefore, the classical literature cited in the manuscript adequately explains its application principles and significance.
Reviewer 2 Report
Comments and Suggestions for AuthorsThis short review presents a good topic and adequate survey in the area of electrochemical lithium extraction. Expansion of scope (detailed comparison with other lithium extraction technologies), more critical comments of the technologies and major revision (listed as below) are suggested before the publication.
1. In the introduction, there should be necessity of the electrochemical extraction technology, by comparing it to other lithium extraction technologies. For example, clearly list the advantage and disadvantage of other methods such as high-grade ores and salt lake brines, employing processes like evaporation, chemical precipitation, solvent extraction, and adsorption/desorption, and so on.
2. The manuscript should be further checked carefully to remove repeating/confusion texts. For example, in introduction, second paragraph, hydrometallurgy is mentioned twice as main technology and primary technology, before and after introduction of electrochemical extraction technology.
3. Some of the presented figures are not explained well. For example, the text should mention and illustrate the river water and sea water functions in Figure 3 (line 143). What's the function of magnetic stirring in Figure 9 (lien 232).
4. Figure 4 (line 151), ''The performance of the LiFePO4 electrode was enhanced...'' What is the performance of LiFePO4? about releasing Li ions?
5. Figure 5 (line 157), ''This system comprises two power supplies, three electrodes,...'' But in the figure, there is no two power supplies, do you mean the power for pump circulation of liquid? And there is no three electrodes. This need to be explained.
6. Line 178, ''The success of this technology hinges on electrode materials that exhibit high selectivity and a robust ion exchange capacity.'' Please confirm here, that electrode materials? Or electrolyte materials (solid membrane)? Need explaination.
7. Line 195, the reason for why monovalent and divalent ions are separated by the membranes should be given.
8. Line 201-212, the H1.6Mn1.6O4 nanoparticle/rGO composite membrane, is used for Li+ adsorption material, but it's different from the ion exchange membrane in electrodialysis method. Is this work in the right position? This is misleading without enough explaination.
9. In addition to the 2 further research aspects, the review should provide a critical analysis in the end between the three methods by comparing their performance, and suggest which is most promising and future works.
10. Other topics such as seawater extraction, integration with renewable energy sources are suggested to be mentioned.
11. There are a lot of typing errors need carefully check, such as super/lower-scription (line 122), double comma (line142, 237), grammar error (line 220 its).
Comments on the Quality of English LanguageThe English language is good, but need careful check and modification.
Author Response
This short review presents a good topic and adequate survey in the area of electrochemical lithium extraction. Expansion of scope (detailed comparison with other lithium extraction technologies), more critical comments of the technologies and major revision (listed as below) are suggested before the publication.
- In the introduction, there should be necessity of the electrochemical extraction technology, by comparing it to other lithium extraction technologies. For example, clearly list the advantage and disadvantage of other methods such as high-grade ores and salt lake brines, employing processes like evaporation, chemical precipitation, solvent extraction, and adsorption/desorption, and so on.
Reply & Revision: Thanks for your helpful comments. The evaporation, chemical precipitation, solvent extraction, and adsorption/desorption are applied in lithium extraction. The evaporation technique can greatly reduce the use of chemicals and environmental impact, but high energy consumption and high carbon emissions restrict its future development. The chemical precipitation technique has advantages of operation simply, low costing; disadvantages include poor selectivity, low lithium recovery, and produce a large amount of wastewater requiring further treatment. The solvent extraction technique has advantages of simple process and the high lithium recovery rate; the disadvantage is that it is only suitable for high- content lithium brine with less magnesium impurities, so the use of solvent extraction is limited. The supplementary content has been added to the manuscript.
- The manuscript should be further checked carefully to remove repeating/confusion texts. For example, in introduction, second paragraph, hydrometallurgy is mentioned twice as main technology and primary technology, before and after introduction of electrochemical extraction technology.
Reply & Revision: Thank you very much for pointing it out. The manuscript has been further checked carefully, and the errors have been modified.
- Some of the presented figures are not explained well. For example, the text should mention and illustrate the river water and sea water functions in Figure 3 (line 143). What's the function of magnetic stirring in Figure 9 (line 232).
Reply & Revision: Thank you very much for your insightful feedback. In Figure 3, the river water represents low salinity, while the sea water represents high salinity. The salt content in seawater can be significantly reduced using electrochemical ion pump technology. Additionally, magnetic stirring is commonly employed to enhance liquid dispersion. The relevant details have been incorporated into the manuscript.
- Figure 4 (line 151), ''The performance of the LiFePO4 electrode was enhanced...'' What is the performance of LiFePO4? about releasing Li ions?
Reply & Revision: Thanks for your helpful comments. The performance of FePO4/K2NiFe(CN)6[FPO/KNiFC] system is electrochemical ion pump technique to recover lithium from low-concentration sources in geothermal water. The relevant content has been added to the manuscript.
- Figure 5 (line 157), ''This system comprises two power supplies, three electrodes,...'' But in the figure, there is no two power supplies, do you mean the power for pump circulation of liquid? And there is no three electrodes. This need to be explained.
Reply & Revision: Thank you for your valuable comments. The phrase, "The system comprises two power supplies, three electrodes,..." is derived from Ref 39, and Figure 5 is used to supplement the content from reference 40. The appropriate references have been added to the manuscript.
- Line 178, ''The success of this technology hinges on electrode materials that exhibit high selectivity and a robust ion exchange capacity.'' Please confirm here, that electrode materials? Or electrolyte materials (solid membrane)? Need explanation.
Reply & Revision: Thank you for your insightful feedback. The statement, "The success of this technology hinges on electrode materials that exhibit high selectivity and a robust ion exchange capacity," indicates that both the selectivity of the electrode material and the transmissibility of the exchange membrane are critical factors for the success of the technology. We have added the relevant content to the manuscript to clarify this point.
- Line 195, the reason for why monovalent and divalent ions are separated by the membranes should be given.
Reply & Revision: Thank you for your valuable feedback. You correctly noted that the mechanism of action, as well as the differences in size and charge, necessitate the use of monovalent and divalent ion exchange membranes. We have incorporated this important information into the manuscript.
- Line 201-212, the H1.6Mn1.6O4 nanoparticle/rGO composite membrane, is used for Li+ adsorption material, but it's different from the ion exchange membrane in electrodialysis method. Is this work in the right position? This is misleading without enough explaination.
Reply & Revision: Thanks for your helpful comments. According to the interpretation of the H1.6Mn1.6O4 nanoparticle/rGO composite membrane from original text, we have added some content, and the relevant content has been updated in the manuscript.
- In addition to the 2 further research aspects, the review should provide a critical analysis in the end between the three methods by comparing their performance, and suggest which is most promising and future works.
Reply & Revision: Thanks for your helpful comments. The application of three methods in electrochemical lithium extraction is widely, but the raw material and initial liquid concentrations targeted by the researchers were not consistent. Thus, it is difficult to compare performance consistently. At present, the three methods are widely used in laboratory research, and the future industrial development needs to be further expanded.
- Other topics such as seawater extraction, integration with renewable energy sources are suggested to be mentioned.
Reply & Revision: Thank you for your insightful comments. This review offers a comprehensive examination of the research progress in lithium recycling using electrochemical methods, while also discussing future prospects for these technologies, particularly in addressing the growing demand for lithium. Although lithium extraction from seawater is an intriguing area of research, as highlighted in articles such as Joule 2018, 2, 1648–1651; Journal of Electroanalytical Chemistry 2019, 850, 113389; and Joule 2020, 4, 1459–1469, our primary focus is on recycling lithium from used lithium-ion batteries rather than extracting it from natural sources. We may explore the potential of lithium extraction from seawater in future work.
- There are a lot of typing errors need carefully check, such as super/lower-scription (line 122), double comma (line142, 237), grammar error (line 220 its).
Reply & Revision: Thank you very much for pointing it out. The corner marks in the manuscript have been checked and revised, including super/lower-scription (line 122), double comma (line142, 237), grammar error (line 220 its) and so on.
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe discription about the figures could be more sufficient and clear.
Comments on the Quality of English Language
Good.
Author Response
1. The description about the figures could be more sufficient and clear.
Reply & Revision: Thank you for your suggestion. We have added the more description of figures in manuscript. The added content in manuscript is highlighted.
