Intercalation‐Assisted In Situ Exfoliation of Cu₂Se Nanosheets as Anode for Ultralong‐Life Aqueous “Rocking‐Chair” Zinc‐Ion Batteries

Abstract Aqueous zinc ion batteries (AZIBs) are a potential energy storage device due to their low cost and environmental friendliness. However, the problems of Zn metal anode lead to low coulombic efficiency and safety problems, thus hindering the practical application of AZIBs. Therefore, developing zinc‐metal free anode materials can effectively avoid the problems. Herein, an intercalation‐assisted in situ exfoliation mechanism is reported to obtain Cu₂Se nanosheets (E‐Cu₂Se) during the electrochemical reaction. The good conductivity of Cu₂Se nanosheets ensures the rapid (de)intercalation of zinc ions and excellent charge transport properties in Cu₂Se. Furthermore, Cu₂Se not only has strong structural stability itself but also can effectively inhibit zinc dendrite through the conversion of copper between the cathode and anode. The results show that the E‐Cu₂Se electrode has a low intercalation potential (≈0.4 V) and a high specific capacity of 284.8 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹. Meanwhile, a “rocking‐chair” aqueous zinc‐ion battery assembled with Zn_xMnO₂ as cathode delivers a specific capacity of 40 mAh g⁻¹ after 60 000 cycles. The exfoliation mechanism of E‐Cu₂Se is discussed based on various characterization techniques and theoretical calculations. This study is expected to provide a new avenue for the development high‐performance “rocking‐chair” AZIBs.