Dual‐sites single atom catalysts hold promise for efficiently regulating multiple reaction processes and explicitly explaining the underlying mechanisms. However, delicate atomic engineering for dual‐site single atom catalysts remains a huge challenge. Herein, atomically dispersed Fe‐Ni single atoms embedded in a nitrogen‐doped carbon matrix (FeNi SAs/NC) are successfully developed with extraordinary activity for electrocatalytic oxygen reduction and evolution reactions (ORR/OER). The atomic FeNi SAs/NC catalyst displays high onset potential (0.98 V) and half‐wave potential (0.84 V) for the ORR, as well as, low overpotential of (270 mV) at 10 mA cm−2 for the OER. The density functional theory calculations indicate that the Fe site as the active center can facilitate the four‐electron reaction process, while Ni sites regulate the electronic structure of Fe sites and further reduce the energy barrier of the rate‐determining step. In addition, the nitrogen‐doped carbon matrix prevents the metal atoms from aggregation and corrosion, leading to the improvement of catalyst durability. As a proof of concept, flexible quasi‐solid‐state zinc– and aluminum–air batteries assembled with the FeNi SAs/NC catalyst exhibit superior peak power densities and discharging specific capacities outperforming the commercial Pt/C. This work provides rational guidance for the synthesis of bifunctional electrocatalysts in next‐generation energy devices for flexible consumer electronics.

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inferior battery performance, such as low practical energy density, and short-term stability, mainly ascribed to the limitation from cathodes. [14,15] Toward this challenge, sulfur, phosphorus, and selenium are promising candidates with a high theoretical capacity and energy density, although there still exists critical limitations such as the slow kinetics process and irreversible dissolution in the electrolyte. [16][17][18][19] The selenium-sulfur (Se x S y ) based cathodes, in which the introduction of high electrical conductivity of Se and its synergistic effect with S with multiplied ratios enable the fast kinetic process and relieved polysulfide shuttle effects, exhibit outstanding electrochemical performance in previous rechargeable Li/Na/K batteries. [20][21][22][23][24][25] This encourages us to envision the application of Se x S y in RABs. To the best of our knowledge, this new series cathode has not been reported to date in RABs. [26][27][28] Meanwhile, the charge redistribution process would also become much more complex toward the conversion reaction in multivalent ion RABs systems, which requires highly-conductivity electron pathway and fast ion diffusion. [29][30][31][32][33] Furthermore, the electrode disintegration, which is mainly ascribed to the side-reactions from binders and metallic current collector, is another critical issue of conversiontype electrodes in RABs. [14] Therefore, novel structured electrodes with high energy density/capacity, long-term stability, and enhanced kinetic process are highly desirable to state-ofthe-art RABs.Herein, we developed, for the first time, Se 2.9 S 5.1 cathode through a new insight via matching electrostatic interaction with Al 3+ in RABs. Furthermore, we also reveal that the sufficient valence electronic energy overlap between cathode materials and Al 3+ would drastically promote kinetic process and overall performance. Based on density functional theory (DFT) simulations and experimental characterization, the optimized Se 2.9 S 5.1 cathode achieves above 600% improved specific capacity and over 200% reduction diffusion barrier among other Se x S y in RABs, which is mainly ascribed to distinct valence bonds with Al 3+ and easily accessible structure. Furthermore, Se x S y with manipulated Se/S ratios were prepared in multi-channel carbon nanofiber (Se x S y @MCNF) as a binder-free and freestanding cathode in RABs to illuminate the side-reaction and electrode pulverization. The well-designed electrode endows amounts of active sites (606 mAh g −1 at 50 mA g −1 , six times 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 2.9 S 5.1 -based cathode with...

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