Preparation and electrochemical performance of N-doped NaCu2S2 for Na-ion supercapacitors

Na-ion supercapacitors have garnered significant interest due to their potential for reduced cost and non-toxicity, making them a promising alternative to Li-ion supercapacitors. This study explores the incorporation of Na ions into layered N-doped copper sulfide to synthesize nanometer-scale acicular N-doped NaCu2S2 via a hydrothermal reaction on nickel foam (NF). The N-doped NaCu2S2/NF electrode exhibits a specific capacitance of 3595.5 F g- 1 (2157.3C g- 1) at a current density of 9 A g- 1. Experimental and theoretical calculations show that the rapid embedding and de-embedding of sodium ions, combined with nitrogen doping in the N-doped NaCu2S2, contributes to its enhanced capacitance performance. Furthermore, an aqueous asymmetrical supercapacitor is assembled using N-doped NaCu2S2/NF as the positive electrode and N-doped NaCu2S2/graphitic felt (GF) as the negative electrode, with a 1 M NaOH electrolyte. The N-doped NaCu2S2/NF//N-doped NaCu2S2/GF configuration achieves an energy density of 96.3 Wh kg- 1 at a power density of 1800 W kg- 1. The pre-insertion method of Na ions demonstrates significant potential for the development of high-performance sodium-ion supercapacitors.