Peer review of: Lamella-nanostructured eutectic zinc–aluminum alloys as reversible and dendrite-free anodes for (2020)

Reviewers' comments: 
 
Reviewer #1 (Remarks to the Author): 
 
An easy alloy strategy was demonstrated in this work to develop highly stable zinc anode and the full 
zinc-ion battery. The overall idea is based on the prohibition of dendrite formation due to the special 
surface nanostructure induced by the alloy effect. The electrochemical performance of the full 
batteries was decent. However, many issues still exist in this paper, which makes it difficult to meet 
the requirement of Nature Communications: 
 
1. Why the alloy can show this lamellar structure and how it can influence the reversible Zn 
plating/stripping. Solid evidence and discussions should be provided. 
 
2. The polarization of CD curves of the symmetric batteries using ZnAl alloy was decreased compared 
to Zn/Zn batteries, though the enhancement was not obvious, and the reason of positive effect from 
the alloy should be included. 
 
3. Since the mixed solution of ZnSO4 and MnSO4 was used as the electrolyte, more experiments in 
terms of Zn/Zn batteries should be carried out, and new discussions of the electrolyte effect are 
needed. 
 
4. The calculation of energy density should also be based on the overall mass of anode and cathode, 
not just the mass of cathode. 
 
5. What about the self-discharge behavior of the Zn/KxMnO2 battery, since both tests in the absence 
and presence of O2 had been presented. The self-discharge mechanism should be discussed. 
 
6. In page 9, the authors mentioned that “This observation is probably due to the absence of 
passivation film on the electroactive Zn surface, which result in the less polarization.” What is the 
passivation film? XPS data before and after cycling test should be included. 
 
7. Has even the author even tried other metals to form Zn-based alloy (e.g., Li, Mg)? This strategy is 
potentially a universal way for Zn anodes. 
 
8. There was no capacity fading at 0.5 A g-1 in the ZnAl/KxMnO2 battery, but the Zn/KxMnO2 battery 
degraded extremely fast. What are the reason besides the effect from the anode? The cathode and 
electrolyte should be analyzed and discussed for both batteries. 
 
9. The XRD and XPS of the symmetric cells long-term Zn stripping/plating cycling measurements 
should be provided to see whether there are side reactions on the anodes. 
 
 
 
Reviewer #2 (Remarks to the Author): 
 
In this paper, the authors show that eutectic-composition alloying of zinc and aluminum could be an 
effective strategy to address the irreversibility of Zn anode. The lamellar structure composed of 
alternating Zn and Al is interesting. The dendrite formation seems to be suppressed in this alloy anode. 
The discussion of the effect of O2 in the electrolyte is also instructive. However, some important 
comments need to be addressed before this paper can achieve the high standard of this reputable 
journal. 

Here are some of my comments: 
1. In figure 3, EIS was used to reveal the oxidation resistances of Zn metal and Zn/Al alloys. To be 
honest, these results are confusing. First of all, the author did not demonstrate how they test the EIS. 
Are they symmetric cells or not? Did the immersion and oxidation process happen inside a sealed cell 
or outside in the electrolytes? The author should give the model of the equivalent circuit and calculate 
the resistance from different components separately. Simply comparing the value does not make 
sense. And also, charge transfer resistance does not mean the oxidation resistance. Actually, the 
author should also explain what the oxidation resistance is. 
2. In the discussion part of Figure 3 and Figure 4, the author should give more explanation about the 
reason for the different phenomenon, but not just present the results. 
3. When discussing the effect of O2, especially during the electrochemical process in a sealed cell, the 
author should consider more than just the O2 in the electrolyte. The author could calculate the 
amount of O2 that dissolved in the electrolyte and compare it with the anode to see whether there is 
enough O2 to oxidize the alloy. Besides that, the reaction between the alloy and the electrolyte and 
H2O also need to be taken consideration. 
4. The author claimed the high columbic efficiency of the alloy anode; however, no data was 
demonstrated for the columbic efficiency of the anode. 
5. As for the full cell performance, Figure 5b is a little confusing. How did the author get the specific 
capacity versus the Scan rate? 
6. Generally, when the loading of the cathode is only 1.0 mg/cm2, which is much less the anode, the 
electrochemical performance usually relies on the cathode part but anode part. As in many previous 
reports, Zn foil can also support a good electrochemical performance. So, in this paper, the author 
should give more strong and supportive data to demonstrate the superiority of the alloy anode, for 
example, limiting the anode/cathode mass ratio.