Heterostructures assembled from graphitic carbon nitride and Ti₃C₂T_x MXene as high-capacity cathode for aluminum batteries

As a compelling complement to lithium batteries, rechargeable aluminum batteries (RABs) have attracted considerable attention because of abundant natural resources, high volumetric capacity, and safety property of aluminum metal. However, the deployment of RABs is hampered by the lack of favorable cathodes with high capacity and rapid kinetics. To address the long-unresolved issue of aluminum-storage capacity and rate, here we design a heterostructured g-C₃N₄/Ti₃C₂T_x hybrid which offers a conductive supporting framework to maintain structural integrity and accelerate electronic transport. The energy storage mechanism of the heterostructured g-C₃N₄/Ti₃C₂T_x cathode was demonstrated as the reversible intercalation of AlCl₄⁻ during cycling. Moreover, the battery-capacitance model mechanism in the heterostructured g-C₃N₄/Ti₃C₂T_x hybrids may accelerate the kinetics of the electrode reactions. Furthermore, DFT calculations certify that heterostructured g-C₃N₄/Ti₃C₂T_x possesses enhanced electrical conductivity and Al trapping capability. Accordingly, the heterostructured g-C₃N₄/Ti₃C₂T_x cathode affords RABs with an excellent Al-storage property (237 mAh g^-1 at 0.5 A g^-1) and considerable rate capabilities (174 mAh g^-1 at 4 A g^-1) among state-of-the-art cathode materials for aluminum batteries.