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Traditional Electrochemical Zn 2+ Intercalation/Extraction Mechanism Revisited: Unveiling Ion‐Exchange Mediated Irreversible Zn 2+ Intercalation for the δ‐MnO 2 Cathode in Aqueous Zn Ion Batteries

2024; Wiley; Volume: 14; Issue: 7 Linguagem: Inglês

10.1002/aenm.202302655

1614-6840

Shuangshuang Cui, Dan Zhang, Yang Gan,

Supercapacitor Materials and Fabrication

Abstract Rechargeable aqueous Zn/δ‐MnO 2 batteries are extensively investigated owing to the low cost, safety and eco‐friendliness. However, the charge storage mechanism of δ‐MnO 2 electrode is still in debate. In this paper, it is revealed that the Zn 2+ intercalation in δ‐MnO 2 electrode is an ion exchange process rather than the commonly‐conceived electrochemical process for the first time. Before the discharge/charge process, Zn 2+ irreversibly intercalates into the structure of δ‐MnO 2 . The ion‐exchange mediated irreversible Zn 2+ intercalation in δ‐MnO 2 has no contribution to the capacity of δ‐MnO 2 electrode during cycles. This study further reveals that the electrochemical H + intercalation/extraction, the electrodissolution of δ‐MnO 2 and the electrodissolution‐electrodeposition of vernadite dominate the charge storage process of δ‐MnO 2 electrode. These findings shed new light on the fundamental understanding for the reaction mechanism of δ‐MnO 2 electrode in aqueous batteries.