Due to the unique electronic structure of aluminum ions (Al 3+) with strong Coulombic interaction and complex bonding situation (simultaneously covalent/ionic bonds), traditional electrodes, mismatching with the bonding orbital of Al 3+, usually exhibit slow kinetic process with inferior rechargeable aluminum batteries (RABs) performance. Herein, to break the confinement of the interaction mismatch between Al 3+ and the electrode, a previously unexplored Se 2.9S 5.1‐based cathode with sufficient valence electronic energy overlap with Al 3+ and easily accessible structure is potentially developed. Through this new strategy, Se 2.9S 5.1 encapsulated in multichannel carbon nanofibers with free‐standing structure exhibits a high capacity of 606 mAh g −1 at 50 mA g −1, high rate‐capacity (211 mAh g −1 at 2.0 A g −1), robust stability (187 mAh g −1 at 0.5 A g −1 after 3,000 cycles), and enhanced flexibility. Simultaneously, in/ex‐situ characterizations also reveal the unexplored mechanism of Se xS y in RABs.