Shape-Assisted 2D MOF/Graphene Derived Hybrids as Exceptional Lithium-Ion Battery Electrodes

Herein, a novel polymer-templated strategy is described to obtain 2D nickel-based MOF nanosheets using Ni(OH)(2), squaric acid, and polyvinylpyrrolidone (PVP), where PVP has a dual role as a structure-directing agent, as well as preventing agglomeration of the MOF nanosheets. Furthermore, a scalable method is developed to transform the 2D MOF sheets to Ni7S6/graphene nanosheet (GNS) heterobilayers by in situ sulfidation using thiourea as a sulfur source. The Ni7S6/GNS composite shows an excellent reversible capacity of 1010 mAh g(-1) at 0.12 A g(-1) with a Coulombic efficiency of 98% capacity retention. The electrochemical performance of the Ni7S6/GNS composite is superior not only to nickel sulfide/graphene-based composites but also to other metal disulfide-based composite electrodes. Moreover, the Ni7S6/GNS anode exhibits excellent cycle stability (approximate to 95% capacity retention after 2000 cycles). This outstanding electrochemical performance can be attributed to the synergistic effects of Ni7S6 and GNS, where GNS serves as a conducting matrix to support Ni7S6 nanosheets while Ni7S6 prevents restacking of GNS. This work opens up new opportunities in the design of novel functional heterostructures by hybridizing 2D MOF nanosheets with other 2D nanomaterials for electrochemical energy storage/conversion applications.