Encapsulation of Metallic Zn in a Hybrid MXene/Graphene Aerogel as a Stable Zn Anode for Foldable Zn-Ion Batteries

A 3D host can effectively mitigate the dendritic growth of a zinc (Zn)-metal anode. However, the increased electrode/electrolyte reaction area using the 3D substrate accelerates the passivation and corrosion at the anode interface, ultimately degrading the electrochemical performance. Here, an oriented freezing process is used to create a flexible MXene/graphene scaffold. Based on the abundant zincophilic traits and micropores in the structure, Zn is densely encapsulated inside the host by the electrodeposition process. During cycling, the composite anode endows an in situ solid electrolyte interface with zinc fluoride at the electrode/electrolyte interface due to inherent fluorine terminations in MXene, efficiently inhibiting the dendritic growth. Furthermore, the design wherein bulk Zn is distributed in a 3D microscale manner suppresses hydrogen evolution reactions (3.8 mmol h⁻¹ cm⁻²) and passivation, through in/ex situ tests. As a result, in a symmetrical cell test, the electrode has a long-cycling life of over 1000 h at 10 mA cm⁻². After continuous single folding followed by double folding, a quasi-solid-state foldable cell with the composite anode and a LiMn₂O₄ cathode (60% depth of discharge) maintains high-capacity retention of over 91%. This research presents a revolutionary encapsulating idea for aqueous Zn-ion batteries, as well as foldable investigation.