Absolute Local Quantification of Li as Function of State-of-Charge in All-Solid-State Li Batteries via 2D MeV Ion-Beam Analysis

Round 1

Reviewer 1 Report

In the current work, Moller at al. have demonstrated a MeV ion beam technique to quantitatively analyze the Li content in an ASSB. Overall, the work is very interesting and the authors have performed thorough experimentations to support their hypothesis. The discussions are appropriate. This reviewer has a couple of minor suggestions for the authors as below:

1. The introduction is very lengthy, and can be shortened appropriately.
2. There are several grammatical and typo errors throughout the manuscript. For instance: Line 90: “calls”. Line 91, what do the authors mean by “percent precision”? Hence, thorough English language editing is necessary.  

Author Response

• The introduction is very lengthy, and can be shortened appropriately.

Intro was slightly shortened. Reviewer 3 requested even more points for the intro, hence, as a compromise, we tried to keep the content while making the wording more concise

• There are several grammatical and typo errors throughout the manuscript. For instance: Line 90: “calls”. Line 91, what do the authors mean by “percent precision”? Hence, thorough English language editing is necessary. 

The two mentioned and other errors were corrected after reading through the whole text.

Reviewer 2 Report

This is an interesting work on the characterization of lithium concentration in the solid-state-batteries as a function of state-of-charge using ion-beam-analysis. The authors have obtained interesting 1D profiles and 2D mapping of the cross section of the solid-state batteries, including operando results from the polymer-based cells. However, the way that the authors write this paper needs improving.

I would suggest this manuscript being published after a minor revision.

(1) All the figures should be mentioned in the main text sequentially.

(2) To save efforts for the reads and avoid confusion, I would suggest the experimental section being moved after the introduction. This is because many experimental details that are essential to understand the figures (for example, Figure 1) in this paper are being given in the experimental section.

(3) Some abbreviations (MEEP, PID) are not defined when appeared first time in the manuscript.

(4) Page 6, line 296: Should the 100% state of charge correspond to a cell voltage of 4.2 V?

(5) Page 8, line 346, “bule parts are made from PEEK”, is this correct?. Line 347, there are no cell A or B shown in the figure.

(6) Why did the authors not perform the operando characterization on the ceramic cell?

(7) Page 13, line 443, the authors state that the theoretical capacity of LiCoO2 is 136 mAh g-1, which is in contradiction with the literature values (274 mAh g-1).

(8) Would the high energy ion beam damage the cell used for characterization?

Author Response

(1) All the figures should be mentioned in the main text sequentially.

Changed.

(2) To save efforts for the reads and avoid confusion, I would suggest the experimental section being moved after the introduction. This is because many experimental details that are essential to understand the figures (for example, Figure 1) in this paper are being given in the experimental section.

The MDPI templates suggest otherwise. Reviewer 3 had a similar remark. The editors clearly encouraged using the journal specific structure. A remark was added after the introduction to point out the article structure.

(3) Some abbreviations (MEEP, PID) are not defined when appeared first time in the manuscript.

Added the corresponding definitions.

(4) Page 6, line 296: Should the 100% state of charge correspond to a cell voltage of 4.2 V?

For the polyer cells, the polymer limited the voltage. 100% SOC is limited not by the LCO reversible but by the electrolyte in this case. Two sentences were added in section 4.2

(5) Page 8, line 346, “bule parts are made from PEEK”, is this correct?. Line 347, there are no cell A or B shown in the figure.

Corrected

(6) Why did the authors not perform the operando characterization on the ceramic cell?

Our experimental time at the accelerator was limited and we had to decide. We expected a higher charging rate for the MEEP cell, saving us some waiting time. Unfortunately the charging rate was still low. It is not an IBA limitation, but originates from the difficulties of the ASB cells.

(7) Page 13, line 443, the authors state that the theoretical capacity of LiCoO2 is 136 mAh g-1, which is in contradiction with the literature values (274 mAh g-1).

136 mAh/g is the reversible part, since only half of the lithium can be reversibly extracted. A sentence was added to section 4.1

(8) Would the high energy ion beam damage the cell used for characterization?

Our experience revealed two relevant aspects in practice which are also shortly mentioned in the introduction. The beam induces heat, in particular with µm spot sizes which can potentially induce >100K of temperature increase, in particular under vacuum. With our sealed atmosphere holder and reduced beam currents this becomes negligible. Secondly, the ion displace atoms in the cell altering its conductivity and structure. SRIM calculations show this becomes negligible with proper optimisation of detectors and beam settings. Sparking due to charge-up, the implantation of H, and the injected ion charges are also potential problems which were solved.

Reviewer 3 Report

The presented article has been making the double impression, at least on me. On the one hand, this is a serious and in-depth study devoted to the application of IBA analytical techniques to all-solid-state Li batteries. On the other hand, this is an unstructured manuscript, in which after the Introduction section immediately starts the presentation of the Results. And only after the Discussion, at the end of the manuscript, the authors have put the description of Materials and Methods. In my opinion, first and foremost the manuscript should be brought to normal (standard) form and only after that it can be reviewed. Also, in the Introduction I recommend to assess an analytical potential of Atom Probe Tomography (APT) and 3D-SIMS for Li investigation in such batteries.

Author Response

The presented article has been making the double impression, at least on me. On the one hand, this is a serious and in-depth study devoted to the application of IBA analytical techniques to all-solid-state Li batteries. On the other hand, this is an unstructured manuscript, in which after the Introduction section immediately starts the presentation of the Results. And only after the Discussion, at the end of the manuscript, the authors have put the description of Materials and Methods. In my opinion, first and foremost the manuscript should be brought to normal (standard) form and only after that it can be reviewed. Also, in the Introduction I recommend to assess an analytical potential of Atom Probe Tomography (APT) and 3D-SIMS for Li investigation in such batteries.

 

Thanks for your review. The somewhat untypical structure of the article relates to the MDPI style/templates. After asking the editors, the journal wants to keep the given structure, but we added a hint on the article structure after the introduction.

Reviewer 1 requested shortening the introduction which is in contradiction to discussing additional methods. We are willing to add relevant methods to the introduction, but please consider/detail how to implement this.

The order of figures was revised.

Round 2

Reviewer 3 Report

The manuscript has been carefully edited and improved. In my view, it can be published in Batteries in present form. But, as before, the "reversed" form of the manuscript presentation (namely, Results-Discussion-Materials and Methods) looks very strange, at least for me. See “When the driver looks for new tracks, the tram derails" by Stanislav Jerzy Lec.