Nickel and Sulfur Coconfined Nitrogen-Rich Carbon Nanofibers as Anode Materials for Pseudocapacitive Sodium Storage

For sodium-ion batteries (SIBs), carbon materials have generated significant interest based on their rich reserves, low cost, green credentials, and excellent performance as anode materials. However, both capacity value and efficiency are far below expectations as the relatively large ion radius of Na+. In this work, 1D nickel and sulfur coconfined nitrogen-rich carbon materials (S–Ni–NC) are synthesized through electrospinning and vapor sulfuration. The formation of nickel sulfide (NiS) is beneficial for enhancing the specific capacity of sodium-ion batteries due to pseudocapacitive charge storage processes. Forming C–S–C covalent bonds efficiently exposes more active sites, increasing the electrical conductivity and reducing the ion transfer resistance. Thus, the S–Ni–NC electrode displays favorable sodium storage performance, which includes outstanding capacity value (320 mAh g–1 at 0.1 A g–1), rate capability (169.6 mAh g–1 at 5 A g–1), and superior long-cycle property (172.1 mAh g–1 over 1000 cycles at 2 A g–1).