Approaching the Theoretical Sodium Storage Capacity and Ultrahigh Rate of Layer-Expanded MoS2 by Interfacial Engineering on N-Doped Graphene

Molybdenum disulfide (MoS2) holds great potential for sodium storage due to its high theoretical capacity of 670 mAh g(-1). However, its theoretical capacity is hardly realized because of low conductivity, sluggish electrochemical kinetics, and unsatisfied structural stability. Herein, a polyaniline-mediated interfacial engineering strategy for the growth of interlayer-expanded MoS2 nanoflowers on N-doped graphene land (E-MoS2/NG) using Mo7O246- anions adsorbed on positively charged polyaniline as the seeds is reported. The strong interfacial interaction between MoS2 and graphene through Mo-N bonds as well as ultrathin interlayer-expanded MoS2 can significantly improve the electrochemical kinetics and structural stability. As a result, E-MoS2/NG with a high MoS2 content of 90 wt% shows a high capacity (620 mAh g(-1) at 0.1 A g(-1)), an ultrahigh rate capability (201 mAh g(-1) at 50 A g(-1)), and outstanding cycle performance (390 mAh g(-1) after 1000 cycles at 1 A g(-1)). Importantly, MoS2 in the composite approaches its theoretical capacity of 670 mAh g(-1). Furthermore, the assembled E-MoS2/NG//activated carbon sodium ion capacitor delivers high energy densities of 150 and 82 Wh kg(-1) at 35 and 14 421 W kg(-1), respectively, and a capacity retention of 78.1% after 1500 cycles at 10 A g(-1), demonstrating great potential for practical application.

Automated summary

By employing a novel polyaniline-mediated interfacial engineering strategy, the growth of interlayer-expanded MoS2 nanoflowers on N-doped graphene has been achieved, leading to enhanced electrochemical kinetics and structural stability. The resulting E-MoS2/NG composite exhibits outstanding electrochemical performance, approaching the theoretical capacity of MoS2 and demonstrating great potential for practical applications in sodium ion capacitors.