NiCo2S4 nanocores in-situ encapsulated in graphene sheets as anode materials for lithium-ion batteries

Bimetallic sulfides were extensively studied as an advanced electrode material for lithium-ion batteries because of their high conductivity and superior capacity compared to metal oxides. We herein have successfully fabricated ultrafine NiCo2S4 nanocores in-situ encapsulated in graphene sheets (NiCo2S4@GS) with three-dimensional porous network structures through a cation adsorption process and subsequent hydrothermal-annealing reaction. In the NiCo2S4@graphene sheets nanohybrids, graphene sheets with abundant mesoporous network structure can be served as a conductive matrix and also be a protective buffer layer to suppress the volume expansion of NiCo2S4 nanoparticles. The NiCo2S4@GS-1 electrodes deliver a high reversible capacity of 813 mAh g(-1) upon 200 cycles at 0.2 A g(-1), ultralong cycling life of 535 mAh g(-1) upon 1000 cycles at 2 A g(-1), and excellent rate capability. Additionally, the advanced button-type full batteries were assembled via coupling NiCo2S4@GS-1 anodes with commercial LiFePO4 cathodes showing superior cycle stability and practicability. This work points out an innovative and scalable strategy for preparing composite electrode materials for lithium-ion batteries.