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 (50–100 nm), nanotubes (600–700 nm), hexagonal coins (100–150 nm), cross-linked 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 ∼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.