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

Abstract

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.

Constructing Advanced Aqueous Zinc‐Ion Batteries with 2D Carbon‐Rich Materials

“…Symmetric battery based on MGA anode delivered a long cycling lifespan of over 1000 h at 10 mA cm −2 (Figure 7b). [ 81 ] Moreover, new concepts of anode designing were proposed by researchers. In 2019, Archer et al achieved well‐oriented epitaxial growth of zinc platelets on parallelly aligned graphene flakes.…”

“…Reproduced with permission. [ 81 ] Copyright 2021, John Wiley and Sons. c) Schematic illustration of the stacked epitaxial deposition of zinc on graphene.…”

Nitrogen‐Doped Carbon Fibers Embedded with Zincophilic Cu Nanoboxes for Stable Zn‐Metal Anodes

“…[18,19] Compared with the hostless Zn plate with planar surface, 3D porous frameworks can not only reduce the local current density and homogenize electric field distribution, but also offer sufficient internal space to confine the plated Zn and mitigate huge volume variation. [20,21] Recently, considerable efforts have been devoted to developing 3D conductive hosts (carbon nanotubes, [22,23] graphene, [24,25] Cu mesh/foam, [26,27] MXene, [28,29] etc.) for ZMAs, and much progress has been achieved.…”

Foldable batteries: from materials to devices

“…Chen and co-workers used Mxene to fabricate an aerogel with 2D graphene (MGA) for a foldable electrode (Figure 5c). 83 The resulting Mxene/rGO composites provided a large surface area for the dense deposition of active materials. Their integrating strategy provided mechanical strength and a large electrode/electrolyte contact area for high flexibility.…”

“…However, the low operating voltage resulting from the irreversible decomposition (oxygen evolution reaction and hydrogen evolution reaction) of aqueous electrolytes hinders realization of high energy density foldable systems. 83,197,198 Replacing conventional ammable liquid electrolytes with solid-state electrolytes can provide improved safety and integrity but challenges such as low ionic conductivity and side reactions between the electrode/electrolyte interfaces are encountered. 20,109,112,153,199 In summary, although numerous efforts have been made to develop foldable ESDs for commercialization, many hurdles still remain to hamper the further approaches near to commercialization.…”