A NiCoSe/CG heterostructure with strong interfacial interaction showing rapid diffusion kinetics as a flexible anode for high-rate sodium storage.

Flexible sodium-ion batteries (SIBs) have aroused great interest in energy storage devices. However, the choice of suitable anode materials is a key step in the application of SIBs. Here, a simple vacuum filtration method is reported to obtain a bimetallic heterojunction structure. The heterojunction exhibits better performance than any single-phase material in sodium storage. The results show that the electron rich Se site and the internal electric field generated by the electron transfer in the heterojunction structure can provide rich electrochemically active areas and effectively promote the electron transport during sodiation/desodiation. More attractively, the strong interfacial interaction in the interface on the one hand maintains the stability of the structure and on the other hand promotes the diffusion of electrons. The NiCoSe/CG heterojunction with a strong oxygen bridge exhibits a high reversible capacity of 338 mA h g at 0.1 A g, and an ignorable capacity attenuation at 2 A g for 2000 cycles. The flexible full battery still shows good reversibility and output stability under bending and crimping. This idea of obtaining high-performance anodes by designing a heterojunction structure and constructing an oxygen bridge can provide a new vision for the design of other materials.