A Comprehensive Review of Lithium-Ion Battery (LiB) Recycling Technologies and Industrial Market Trend Insights

Round 1

Reviewer 1 Report

As written in this review paper, the recycling technology of lithium-ion batteries is becoming more and more important recently. In this situation, this paper covers many aspects very well containing relating technologies and industrial movements. I just suggest some minor comments as listed below.

1.       In Introduction, the authors describe the contents of other previous reviews with their strong and weak points. I think it is not necessary to point out such weak points in detail.  

2.       The texts in Figures 1 and 4 are difficult to read. I want the authors to make them bigger.

3.       In Fig. 2, there are two “Li2O vapor” boxes. I think the bottom one is not necessary.

4.       As for the Figure 4, the procedure in the direct recycling is not clear. It is better to have the same format with Figures 2 and 3.

5.       In Fig.5, since the data for 2023 is only for Q1, it is not fair to put it on the graph with the data of other years.

6.       The format of the chemical formula (superscript, subscript, uppercase, lowercase, etc) is not consistent. Please correct them.

Some minor editing would be necessary.

Author Response

Please see attached file.

Thanks!

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript started from the introduction about the spent battery situation and then discussed 3 main battery recycling strategies, including pyrometallurgical, hydrometallurgical, and direct recycling methods. Their individual process, advantages/disadvantages and the progress have been discussed and compared in the manuscript. Finally, the author gave a brief discussion about the current market situation and industrial layout, which is comprehensive for a review. However, there are still some major concerns before the manuscript can be considered for publication.

Some major comments

1. The authors mentioned many different strategies for pyrometallurgical, hydrometallurgical, and direct recycling methods, and mentioned many times the environmental effects, such as energy consumption, and secondary pollution, as well as the economic effects for different methods. It will be helpful if the life cycle analysis (LCA) can be given, then it can be clearer to compare different strategies.

2. The manuscript used many examples from different papers to compare different strategies. To help the reader to understand the difference in various methods, maybe a table can be added for each strategy, including pyrometallurgical, hydrometallurgical, and direct recycling methods. The comparison includes but is not limited to treatment conditions, sources and final products for each component, like electrolyte, anode, separators, cathode and so on, the application of the products (if the cathodes were resynthesized, the performance of them).

3. The section 3.3 should be well organized, like section 3.2 and its subsection, therefore a more clear idea can be obtained by the reader.

4. Some discussion or opinion should be provided in Section 3, beyond listing all the papers and what they did.

For example, what can be the current and best solution based on all of this information and why.

Due to the gap between the academic and industry, what should be solved before we can achieve the technical shift from current to best solution about battery recycling?

5. Figure 2 and Figure 3 can be better designed to avoid misleading.

The material flow and the operation can be distinguished to be clear, and for some procedures, the extra reagents are listed like coke and limestone in the Figure 2, but the other are not, like the acid used in the Figure 3.

Also, not all the waste streams are listed, for example, after discharging and dismantling, where are the other parts other than electrode materials?

For the alloy in Figure 2, if general spent LIB is used, where are Mn and Ni?

Some small comments

6. For the introduction part. “In 2016, the global LiB market was reported to exceed $20 billion at the cell level, and the sales have increased by an average of 16% per year since 1996 (Chen et al., 2019)…” All the information is based on data from 5 to 10 years ago, and is a little out of date. Since this review is written in 2024, I feel updated information can be provided to show the trend.

7. The words in Figure 1 are too small to read.

8. Equation 1 seems wrong to me. It is impossible to get Fe⁶⁺ for oxidizing roasting.

9. Figure 2, the slag should be listed in the figure as the waste stream.

10. Some mistakes, including chemical names, valance states and so on in the manuscript can lead to misunderstanding, the author should read through the paper to correct them. For example, CO²⁺ in equation 4, CoNO3 and FeNO3, LiFePo4, HCL and so on

The quality of English is OK for me.

Author Response

Please see attached file.

Thanks!

Author Response File: Author Response.docx

Reviewer 3 Report

The review submitted by Bowen He focuses on LIBs recycling technology, encompassing insights into recycling market trends and an overview of global players in LIBs recycling. Personally, I appreciate the attention given to emerging direct recycling technology. However, to enhance the review's relevance to readers, the following points should be addressed:

-General: While the authors include relevant references, they appear to be dated especially in sections 3.1 and 3.2 (including subsections).

-It would be valuable to add information about an emerging pretreatment method for selectively recovering lithium before metal leaching, involving electrochemical extraction. (https://doi.org/10.1021/acssuschemeng.0c04960, https://doi.org/10.1016/j.jechem.2023.09.040)

-Section 3.2.3.: Consider adding a brief paragraph about leaching using Deep Eutectic Solvents. (https://doi.org/10.1002/cssc.202200966, https://doi.org/10.1016/j.cej.2021.129249)

Author Response

Please see the attached file.

Thanks!

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

I am OK with the current version.

The quality of English is OK for me.

Reviewer 3 Report

Comments have been addressed, paper can now be published.