R-010

Yauhen Aniskevich

yaniskevich@polsl.pl

Centre for Organic and Nanohybrid Electronics, Silesian University of Technology, Gliwice, Poland

Seung-Taek Myung, Hybrid Materials Research Center, Department of Nanotechnology and Advanced Materials Engineering & Sejong Battery Institute, Sejong University, Seoul, South Korea

Proton-Assisted Reactions in Transition Metal-Based Zn-Metal Batteries

Research on aqueous zinc-metal and zinc-ion batteries (ZIBs) has intensified over the last decade due to the relative stability of Zn electrodes in Zn2+ mildly acidic aqueous electrolytes and the high capacity of transition metal-based positive electrodes. Although aqueous ZIBs exhibit promising charge/discharge behavior, the mechanisms usually involve a complex interplay of water- and proton-assisted processes, including proton co-insertion, dissolution-deposition, and amorphization of active materials.

Here, we discuss the impact of water- and proton-assisted reactions on Mn-based and V-based positive electrode materials based on several studies. The study on four (α, β, γ, δ)-MnO2 polymorphs in aqueous electrolyte indicated strong dissolution-deposition behavior leading to amorphization of electrode material and fading of differences between different polymorphs upon cycling.[1] However, our recent results demonstrate that such amorphization is absent for nonaqueous Zn-MnO2 cells, where the Zn2+ diffusion rather than the proton reactions define dis/charge behavior. Similarly to the amorphization of MnO2 electrodes in aqueous cells, we found the vanadium-containing hexacyanoferrate framework to demonstrate the leaching of V+5 into an electrolyte solution and the formation of electroactive amorphous VOx oxide.[2] Severe pH changes in the cell accompany the dissolution-deposition of the vanadium compounds. 

The similarity in deposition-dissolution chemistry for Mn- and V-based electrodes allows us to suggest a generalized mechanism for the aqueous ZIBs' water-assisted degradation behavior, which is triggered by the solubility of transition metal ions and their oxide/hydroxide electrochemistry.

Acknowledgments:

This research was supported by the International Research & Development Program of the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT of Korea (2022H1D3A2A02092011) and Ulam NAWA scholarship BNI/ULM/2024/1/00099/U/00001. 

References

1.        Journal of Power Sources, 2022, 523, 231023

2.        Energy Storage Materials 2023, 63, 103017