Uniformly MXene‐Grafted Eutectic Aluminum‐Cerium Alloys as Flexible and Reversible Anode Materials for Rechargeable Aluminum‐Ion Battery

Abstract Aluminum is an attractive anode material in aqueous multivalent‐metal batteries for large‐scale energy storage because of its high Earth abundance, low cost, high theoretic capacity, and safety. However, state‐of‐the‐art aqueous aluminum‐ion batteries based on aluminum anode persistently suffer from poor rechargeability and low coulombic efficiency due to irreversibility of aluminum stripping/plating and dendrite growth. Here eutectic aluminum‐cerium alloys in situ grafted with uniform ultrathin MXene (MXene/E‐Al 97 Ce 3 ) as flexible, reversible, and dendrite‐free anode materials for rechargeable aqueous aluminum‐ion batteries is reported. As a result of the MXene serving as stable solid electrolyte interphase to inhibit side reactions and the lamella‐nanostructured E‐Al 97 Ce 3 enabling directional Al stripping and deposition by making use of symbiotic α‐Al metal and intermetallic Al 11 Ce 3 lamellas, the MXene/E‐Al 97 Ce 3 hybrid electrodes exhibit reversible and dendrite‐free Al stripping/plating with low voltage polarization of ± 54 mV for ≥1000 h in a low‐oxygen‐concentration aqueous aluminum trifluoromethanesulfonate (Al(OTF) 3 ) electrolyte. These superior electrochemical properties endow soft‐package aluminum‐ion batteries assembled with MXene/E‐Al 97 Ce 3 anode and Al x MnO 2 cathode to have high initial discharge capacity of ≈360 mAh g −1 at 1 A g −1 , and retain ≈85% after 500 cycles, along with the coulombic efficiency of as high as 99.5%.