Selenium‐Bridged Bimetallic Selenide Heterostructure for Superior Sodium Storage

The development of anode materials with tailored architectures, high capacity, and robust structural stability is crucial for balancing anode-cathode kinetics and capacity in sodium-ion hybrid capacitors (SIHCs). In this work, a carbon-coated bimetallic selenide heterostructure (Fe₃Se₄/MnSe@C, denoted as FMSC) with interfacial selenium-bridged bonds is constructed through interface engineering using a Fe-Mn Prussian blue analogue as the precursor. A built-in electric field arises from the interfacial band offset and electronegativity difference, thereby driving charge redistribution and facilitating the stabilization of the heterostructure. Enhanced electrical conductivity from carbon coating, coupled with reinforced structural integrity and improved charge transport enabled by selenium-bridged bonds, collectively allow the FMSC electrode to deliver stable cycling performance in sodium-ion batteries (SIBs), with retained capacities of 336 and 367 mA h g^-1 after 1000 cycles at 5 and 10 A g^-1, respectively. Electrochemical kinetics analysis and theoretical calculations confirm that the synergy between selenium-bridged bonds and heterostructures stabilizes the material structure, promotes charge transfer, and accelerates reaction kinetics. As a result, the SIHC full cell incorporating an AC cathode and the FMSC anode achieves an energy density of 104 W h kg^-1 at a power density of 101 W kg^-1, while also maintaining 90% of its capacity after 3000 cycles under 2 A g^-1, demonstrating significant potential for practical sodium-based energy storage.