Two-dimensional nanosheets of bimetallic chalcogenide-tagged nitrogen-doped carbon as a cathode for high-performance and durable zinc-ion capacitors

Abstract

Zn-ion capacitors (ZICs) are thought to be potential electrochemical energy storage devices due to their complementary energy density, which is comparable to that of batteries, and superior power characteristics when compared to capacitors. However, the electrochemical stability of current ZICs is inadequate due to the structural instability of the Zn anode associated with the dissolution of conventional cathode materials in conventional aqueous electrolytes. Given the rapid growth of metal chalcogenides in electrochemical energy storage applications, the use of bimetallic chalcogenide-based cathodes in ZICs are desirable. Two-dimensional (2D) bimetallic chalcogenide-tagged nitrogen-doped carbon (NbMo₆S₈/NC) was prepared as a cathode for use with modified conventional electrolytes in ZICs, affording a maximal specific capacity of 167.89 mA h g⁻¹ at 0.25 A g⁻¹ and superior rate capability. The developed NbMo₆S₈/NC ZIC delivered a battery-like specific energy of 188.87 and 50.22 W h kg⁻¹ at supercapacitor-like power densities of 250 and 2500 W kg⁻¹, respectively. In a flexible ZIC, the resulting NbMo₆S₈/NC nanosheets (∼10 nm) could withstand 15 000 charge–discharge cycles with an initial capacitive retention of 87.60%. A pair of flexible NbMo₆S₈/NC ZICs connected in series successfully powered light-emitting diodes, demonstrating high potential applications. These findings suggest that NbMo₆S₈/NC ZIC is capable of driving portable and smart electronics, demonstrating its functionality in real-world applications.