Ion-exchange strategy of CoS2/Sb2S3 hetero-structured nanocrystals encapsulated into 3D interpenetrating dual-carbon framework for high-performance Na+/K+ batteries

Abstract Combining the advantages of cobalt and zinc-based imidazolate frameworks (ZIF-67 and ZIF-8), CoS2/Sb2S3 hetero-structured nanocrystals encapsulated into interpenetrating dual-carbon framework of nitrogen-doped carbon and carbon nanotubes (CoS2/Sb2S3@NC/CNT) were successfully prepared by ion-exchange reaction between Co and Sb3+ and subsequent sulfidation reaction process. The supported dual carbon framework derived from ZIF-8 and ZIF-67 not only buffers volume expansion during repeated discharge/charge to prevent polyhedron from collapsing but also significantly enhances electronic conductivity which is beneficial to optimize rate performance and cycle stability. Besides, introducing of Sb2S3 to form heterostructure greatly improves electrochemical properties. As a result, the CoS2/Sb2S3@NC/CNT heterostructure exhibits favorable rate capability and cycle stability in both sodium-ion battery (SIBs) and potassium-ion battery (PIBs). The CoS2/Sb2S3@NC/CNT anode in SIBs delivers the reversible specific capacity of 360.1 mAh g−1 at the current density of 0.5 A g−1 after 200 cycles, while the CoS2/Sb2S3@NC/CNT anode in PIBs exhibits the specific capacity of 453.5 mAh g−1 at the current density of 0.2 A g−1 after 50 cycles. The complex heterostructure consisting of CoS2/Sb2S3 core and coated carbon shell easily promotes electrolyte penetration and further accelerates ions diffusion and electrochemical reaction kinetics. This material will provide a novel alternative method for the preparation of heterogeneous structure anode materials, paving the way for being applied in high-efficiency energy storage devices.