Morphology Variations in Copper Sulfide Nanostructures as Anode Materials for Na-Ion Capacitors

The electrochemical behavior of copper sulfide (CuS) as an electrode material for a Na-ion capacitor (NIC) is closely related to its morphology. Here, various CuS nanostructures, including nanoparticles (50100 nm), nanotubes (600-700 nm), hexagonal coins (100-150 nm), crosslinked nanotubes (600-700 nm), and nanoworms (200-250 nm), are synthesized by simple chemical routes and investigated for NICs in an aqueous system. For the first time, we are reporting the CuS cross-linked nanotubes (CLNTs) and various nanostructures' electrochemical performance for NICs. It is observed that CLNTs reveal a superior gravimetric capacitance of 275 F g(-1) at 0.5 A g(-1) in three-electrode configurations, as compared to the other investigated CuS nanostructures. The uniformly distributed hollow nature of CLNTs facilitates electrolyte infiltration and provides a more active surface for the interaction of more Na+ ions. The symmetric configuration of two electrodes with CLNTs shows a gravimetric capacitance of 315 F g(-1) at 1 A g(-1) followed by device fabrication with a maximum working potential of 2.5 V. The device lights up a red LED of 1.2 V and can hold a charge for similar to 111 s at 1 A g(-1). CuS CLNTs have high potential for large-scale energy storage devices due to their exceptional electrochemical performance and higher conversion reaction.