Strong heterointerface coupling and dual carbon confinement for construction of hollow bimetallic nickel copper sulfide spheres enabling high-rate and ultra-stable sodium storage

Nickel disulfide (NiS2) is recognized as one type of perspective anode materials for sodium-ion batteries (SIBs) because of its exceptional theoretical capacity. Nonetheless, the application of NiS2 is mainly restricted by its poor cycling and rate performances, which stem from low electronic conductivity, slow sodium diffusion kinetics and severe volume changes during cycling. Constructing heterostructures from metal-organic frameworks (MOFs) as functional precursor represents an emerging and effective approach to mitigate these critical issues. Herein, we present the design and fabrication of hollow NiS2/CuS@C hybrid spheres with strongly coupled heterogeneous interfaces and dual carbon confined structure using Ni-MOF as precursor through a combination of solvothermal/ion exchange reactions, glucose coating, and subsequent calcination processes. Through the strong coupling effect of bimetallic sulfides with optimized charge redistribution at the heterointerfaces, along with the dual carbon confinement derived from the decomposition of internal MOF ligands and external glucose, the delicately designed hollow NiS2/CuS@C hybrid spheres afford enhanced structural integrity and electronic conductivity, alleviated mechanical stress, as well as accelerated Na+ ion transport kinetics in the composite. Benefiting from these merits, the resulting NiS2/CuS@C anode delivers prominent sodium storage properties with high capacity (810 mAh g- 1 at 1.0 A g- 1), impressive rate capability (658 mAh g- 1 at 5.0 A g- 1) and ultrastable long-cycling stability (125 % retention after 3500 cycles at 5.0 A g- 1), indicating its development prospect in high-rate and durable SIBs applications.