Advanced nanoarchitectural superstructure hybridized with covalent organic nanosheets and 2H-MoS2 to boost the performance of sodium-ion batteries

초록

Push-pull structured covalent organic nanosheets (CONs) are promising anode materials for sodium-ion batteries (SIBs) owing to their flexible pi-conjugated frameworks and tunable porosity. In contrast, MoS2 anodes have a high capacity but suffer from capacity degradation owing to their low intrinsic conductivity and volume expansion. To address these limitations, we developed a composite of 2H-MoS2 nanosheets and multi-layered hollow CON spheres (CON/MoS2-HS). This composite was fabricated via the solvothermal synthesis of 2H-MoS2 using CONs stacked on polystyrene beads as a template. CON/MoS2-HS exhibited improved electrical and ionic conductivities and reversible capacity, while its robust structural integration limited the changes in volume and mechanical stress during cycling, resulting in excellent long-term cycling stability. In contrast, reduced graphene oxide (rGO)/MoS2-HS was characterized by weaker interactions between rGO and 2H-MoS2, meaning that MoS2 aggregation and volume expansion could not be prevented, thus compromising cycle stability and capacity. The CON/MoS2-HS electrode delivered a high reversible capacity of 671.8 mAh g(-1) (similar to 97% of the theoretical capacity) after 600 cycles at 100 mA g(-1) and retained a capacity of 203.1 mAh g(-1) after 5000 cycles at 5000 mA g(-1). The rate performance and long-term cycling stability of the CON/MoS2-HS electrode outperformed those of conventional MoS2-based anodes, demonstrating the strong synergistic relationship between the multilayered CON architecture and 2H-MoS2 nanosheets.

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