Interfacial-synergy-driven in-situ carbon-coated Cu1.8Se/CoSe2 heterostructures for sodium storage

Transition metal selenides, featuring high theoretical capacity, superior electrical conductivity, and abundant active sites, are regarded as promising anode candidates for sodium-ion batteries (SIBs) by balancing energy density and reaction kinetics. However, they typically suffer from severe volume expansion, dissolution of active phases, and inadequate conductive networks under fast-charging conditions, making it difficult to achieve stable cycling at high rates. In this work, a Cu 1.8 Se/CoSe 2 @C bimetallic heterostructure is constructed via a MOF-derived strategy, in which microwave-assisted hydrothermal synthesis combined with solid-state selenization enables in-situ carbon coating, forming a continuous conductive network and buffering volume stress. The Cu 1.8 Se/CoSe 2 heterointerface generates an internal electric field that induces electron redistribution and reduces the Na + diffusion barrier, thereby significantly enhancing interfacial kinetics and reaction reversibility. Benefiting from the synergistic structural design and interfacial mechanism, the material exhibits outstanding fast-charging performance: even at an ultrahigh current density of 50 A g −1 (within 20 s), a reversible capacity of 297.5 mAh g −1 is still maintained. When paired with an Na 3 V 2 (PO 4 ) 3 (NVP) cathode for full cell assembly, a discharge capacity of 300.4 mAh g −1 is retained after 5000 cycles at 2 A g −1 with a retention of 82.3%, and the average discharge voltage reaches 1.46 V, ensuring higher safety by helping reduce the risk of Na dendrite formation during fast charging. This MOF-derived carbon network and bimetallic heterointerface engineering strategy effectively addresses the structural and kinetic limitations of selenide anodes under fast-charging conditions, providing a feasible pathway for designing fast-charging-oriented anode materials for SIBs.