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Sodium-ion batteries (SIBs) represent a highly promising class of energy storage devices. Enhancing SIBs performance necessitates innovative anode material development to overcome persistent challenges associated with the large ionic radius of Na + , namely significant electrode volumetric expansion and sluggish reaction kinetics. Herein, a macroporous bimetallic (Co, Fe) selenide containing abundant heterojunction interfaces encapsulated into a carbon framework (M-CoSe 2 /FeSe 2 @C) is prepared by combining an in-situ crystallization strategy with carbonization-selenization treatment. The structural characterization reveals that the resulting M-CoSe 2 /FeSe 2 @C possesses a well-defined porous architecture with internal CoSe 2 -FeSe 2 nanoparticles encapsulated by an external carbon matrix. This configuration not only enhances electrical conductivity but also stabilizes the composite structure throughout sodiation/desodiation cycling. Evaluated as an anode in SIBs, the M-CoSe 2 /FeSe 2 @C electrode delivers outstanding cycling stability (retaining 455.0 mA h g −1 at 0.2 A g −1 after 100 cycles) and exceptional rate capability (285.6 mA h g −1 at 10 A g −1 ). These superior properties are primarily attributed to the high density of interphase boundaries generated by the dual-phase configuration. Combined experimental and theoretical investigations demonstrate that these boundaries, particularly regions of high electron density on the FeSe 2 side, kinetically favor Na + adsorption, thereby accelerating sodium storage kinetics. Furthermore, multi-step electrochemical reaction mechanisms within the composite were elucidated through in-situ and ex-situ characterization analyses.
Zhu et al. (Thu,) studied this question.