Controllable Synthesis of Atomically Thin Type-II Weyl Semimetal WTe2 Nanosheets: An Advanced Electrode Material for All-Solid-State Flexible Supercapacitors

Compared with 2D S-based and Se-based transition metal dichalcogenides (TMDs), Te-based TMDs display much better electrical conductivities, which will be beneficial to enhance the capacitances in supercapacitors. However, to date, the reports about the applications of Te-based TMDs in supercapacitors are quite rare. Herein, the first supercapacitor example of the Te-based TMD is reported: the type-II Weyl semimetal 1Td WTe₂. It is demonstrated that single crystals of 1Td WTe₂ can be exfoliated into the nanosheets with 2–7 layers by liquid-phase exfoliation, which are assembled into air-stable films and further all-solid-state flexible supercapacitors. The resulting supercapacitors deliver a mass capacitance of 221 F g⁻¹ and a stack capacitance of 74 F cm⁻³. Furthermore, they also show excellent volumetric energy and power densities of 0.01 Wh cm⁻³ and 83.6 W cm⁻³, respectively, superior to the commercial 4V/500 µAh Li thin-film battery and the commercial 3V/300 µAh Al electrolytic capacitor, in association with outstanding mechanical flexibility and superior cycling stability (capacitance retention of ≈91% after 5500 cycles). These results indicate that the 1Td WTe₂ nanosheet is a promising flexible electrode material for high-performance energy storage devices.

The first Te-based transition metal dichalcogenide supercapacitor, 1Td WTe₂, is successfully fabricated by liquid exfoliation of bulk samples into nanosheets with 2–7 layers, and subsequent device assembly, which achieves mass and stack capacitances of 221 F g⁻¹ and 74 F cm⁻³, and volumetric energy and power densities of 0.01 Wh cm⁻³ and 83.6 W cm⁻³.

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