Tuning nickel cobalt sulfides embedded in hierarchical porous carbon nanosheets/carbon nanotubes interpenetrating frameworks by in situ bimetallic MOF-derived engineering towards exceptional lithium storage

A Ni/Co-MOF-engaged bimetallic nickel cobalt sulfide nanoparticles encapsulating into a 3D interpenetrating hierarchical porous ultrathin carbon nanosheets/carbon nanotubes framework (NiCo2S4 @HPCS/CNTs) have been designed and fabricated via carbonization under the reducing atmosphere and further sulfurization processes. The in situ development of extruded CNTs from organic ligands in MOF templates is autocatalyzed by the metal nanoparticles created during the reduction process. Intriguingly, MOFs serve as periodically atom-dispersed self-sacrificial templates for the in situ formation of hierarchical porous carbon-encapsulated micro/nano heterostructure materials. NiCo2S4 nanocrystals are uniformly dispersed into the 1D CNTs/2D carbon nanosheets/3D carbon spheres conductive networks in this special compositional and hierarchical structure, effectively inhibiting volume expansion, enhancing the electronic conductivity, and further enabling ultrafast lithium ion diffusion kinetics. When used as anode materials of lithium-ion battery (LIB), the NiCo2S4 @HPCS/CNTs electrode delivers outstanding cycling stability with capacity retention of 782.4 mAh g-1 after 800 cycles at 1 A g-1 and excellent rate capability of 584.9 mAh g-1 at a high current density of 4 A g-1. This study provides a novel approach for preparing multi-metallic sulfide generated from MOF precursors with surprisingly heterostructures as the advanced anode materials for LIBs.