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

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-Al97Ce3) 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-Al97Ce3 enabling directional Al stripping and deposition by making use of symbiotic alpha-Al metal and intermetallic Al11Ce3 lamellas, the MXene/E-Al97Ce3 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-Al97Ce3 anode and AlxMnO2 cathode to have high initial discharge capacity of approximate to 360 mAh g(-1) at 1 A g(-1), and retain approximate to 85% after 500 cycles, along with the coulombic efficiency of as high as 99.5%.