Few-layered Ti3C2 MXene anchoring bimetallic selenide NiCo2Se4 nanoparticles for superior Sodium-ion batteries

In order to facilitate the sluggish Na+ insertion/extraction kinetics and improve the poor structural durability of sodium-ion batteries (SIBs) anodes, we for the first time rationally fabricate few-layered Ti3C2/NiCo2Se4 3D architectures (f-Ti3C2/NiCo2Se4) as anodes for SIBs via a facile solvothermal approach with assistance of solution-phase flocculation strategy to avoid restacking issue of few-layered Ti3C2 MXene nanosheets (f-Ti3C2 MXene). The 0D bimetallic selenide NiCo2Se4 nanoparticles as a Na+ reservoir with higher redox activity are uniformly decorated on f-Ti3C2 MXene, effectively preventing the self-restacking of f-Ti3C2 MXene. A fast electron/Na+ transport ability and high surface-to-volume ratio provided by the unique f-Ti3C2 MXene substrate endow the composites with rapid charge transfer kinetics and intimate contact between electrolyte and electrode. Meanwhile, f-Ti3C2 MXenes are able to act as a flexible skeleton to facilitate strain relief and restrain pulverization of NiCo2Se4 nanoparticles during cycling. As a result, the 0D/2D NiCo2Se4/f-Ti3C2 hybrids exhibit superior cyclic stability and outstanding rate performance when applied in SIBs. Furthermore, dual sodium storage mechanisms of conversion reaction for NiCo2Se4 and intercalation/de-intercalation for f-Ti3C2 MXene among the hybrids have been verified by ex-situ XRD technique. The presented strategy can also be used to tackle the intrinsic problems of various bimetallic selenides by integrating them with few-layered MXene to fabricate hybrids for SIBs anodes.