Metallic Few-Layered VS₂ Ultrathin Nanosheets: High Two-Dimensional Conductivity for In-Plane Supercapacitors

TLDR

Portable electronics demand ultrathin power sources, and in‑plane supercapacitors are emerging as a competitive candidate that requires two‑dimensional materials with high conductivity, surface area, and permeable channels; vanadium disulfide (VS₂) offers metallic conductivity and exfoliable S–V–S layers, making it an ideal platform. The authors developed an ammonia‑assisted exfoliation method to produce ultrathin VS₂ nanosheets comprising fewer than five S–V–S layers, creating a new two‑dimensional metallic material. They fabricated highly conductive VS₂ thin‑film electrodes for in‑plane supercapacitors using the exfoliated nanosheets. The resulting device achieved a specific capacitance of 4,760 µF cm⁻² in a 150 nm configuration and retained performance after 1,000 charge–discharge cycles, demonstrating high‑performance in‑plane supercapacitors based on quasi‑two‑dimensional materials.

Abstract

With the rapid development of portable electronics, such as e-paper and other flexible devices, practical power sources with ultrathin geometries become an important prerequisite, in which supercapacitors with in-plane configurations are recently emerging as a favorable and competitive candidate. As is known, electrode materials with two-dimensional (2D) permeable channels, high-conductivity structural scaffolds, and high specific surface areas are the indispensible requirements for the development of in-plane supercapacitors with superior performance, while it is difficult for the presently available inorganic materials to make the best in all aspects. In this sense, vanadium disulfide (VS2) presents an ideal material platform due to its synergic properties of metallic nature and exfoliative characteristic brought by the conducting S–V–S layers stacked up by weak van der Waals interlayer interactions, offering great potential as high-performance in-plane supercapacitor electrodes. Herein, we developed a unique ammonia-assisted strategy to exfoliate bulk VS2 flakes into ultrathin VS2 nanosheets stacked with less than five S–V–S single layers, representing a brand new two-dimensional material having metallic behavior aside from graphene. Moreover, highly conductive VS2 thin films were successfully assembled for constructing the electrodes of in-plane supercapacitors. As is expected, a specific capacitance of 4760 μF/cm2 was realized here in a 150 nm in-plane configuration, of which no obvious degradation was observed even after 1000 charge/discharge cycles, offering as a new in-plane supercapacitor with high performance based on quasi-two-dimensional materials.