Self-supporting network-structured MoS2/heteroatom-doped graphene as superior anode materials for sodium storage.

Abstract

Layered graphene and molybdenum disulfide have outstanding sodium ion storage properties that make them suitable for sodium-ion batteries (SIBs). However, the easy and large-scale preparation of graphene and molybdenum disulfide composites with structural stability and excellent performance face enormous challenges. In this study, a self-supporting network-structured MoS2/heteroatom-doped graphene (MoS2/NSGs-G) composite is prepared by a simple and exercisable electrochemical exfoliation followed by a hydrothermal route. In the composite, layered MoS2 nanosheets and heteroatom-doped graphene nanosheets are intertwined with each other into self-supporting network architecture, which could hold back the aggregation of MoS2 and graphene effectively. Moreover, the composite possesses enlarged interlayer spacing of graphene and MoS2, which could contribute to an increase in the reaction sites and ion transport of the composite. Owing to these advantageous structural characteristics and the heteroatomic co-doping of nitrogen and sulfur, MoS2/NSGs-G demonstrates greatly reversible sodium storage capacity. The measurements revealed that the reversible cycle capacity was 443.9 mA h g-1 after 250 cycles at 0.5 A g-1, and the rate capacity was 491.5, 490.5, 453.9, 418.1, 383.8, 333.1, and 294.4 mA h g-1 at 0.1, 0.2, 0.5, 1, 2, 5 and 10 A g-1, respectively. Furthermore, the MoS2/NSGs-G sample displayed lower resistance, dominant pseudocapacitive contribution, and faster sodium ion interface kinetics characteristic. Therefore, this study provides an operable strategy to obtain high-performance anode materials, and MoS2/NSGs-G with favorable structure and excellent cycle stability has great application potential for SIBs.