ZnS nanoparticles embedded in N-doped porous carbon xerogel as electrode materials for sodium-ion batteries

zinc sulfide (ZnS) has attracted extensive attention as an electrode material for sodium-ion batteries (SIBs) due to its high capacity and abundant resource. In order to improve the cycling stability, ZnS nanoparticles embedded in N-doped porous carbon xerogel (ZnS/N-CX) were prepared via a facile electrostatic assembly, followed by a high-temperature sintering treatment. In contrast to the retention rate of bare ZnS electrode (6.4%), the ZnS/N-CX electrode shows better capacity retention (51.8%) at a current density of 0.5 A g−1, and delivers a reversible capacity of 312 mAh g−1 at a current density of 0.1 A g−1. This is because the porous N-CX derived from polyelectrolytes can enhance the ZnS nanoparticles' conductivity during long-term cycling. Besides, X-ray diffraction analysis is used to confirm the (de)sodiation mechanism during the 1st cycle of the ZnS/N-CX electrode. In addition, X-ray photoelectron spectroscopy analysis indicates that polymeric components in the solid electrolyte interphase (SEI) prefer to form on the surface of loaded N-CX, resulting in a massive Na+ consumption and rapid decrease of initial Coulombic efficiency (CE). The analysis of electrochemical impedance spectroscopy reveals that the increase of interface resistance is suppressed in long-term cycling, with respect to the bare ZnS electrode. Therefore, these results prove that the synergistic approach of supporting/coating N-CX can be applied in the metal sulfides to achieve improved performance in terms of Na+ storage capacity.