Prussian Blue Analogue-Derived Cobalt Sulfide Nanoparticles Embedded in N/S-Codoped Carbon Frameworks as a High-Performance Anode Material for Sodium-Ion Batteries

Metal sulfides display considerable theoretical capacities as anode materials in sodium-ion batteries (SIBs), but their application is limited by their large volume expansion, sluggish charge-transfer kinetics, and poor cycling performances. In this study, unlike the traditional coprecipitation method to prepare the Prussian blue analogue (PBA), PBA with a tremella-like microflower structure is first synthesized by the hydrothermal method under the synergistic effect of trisodium citrate dihydrate (TSC, Na3C6H5O7·2H2O) and K3[Co(CN)6], and two kinds of cobalt sulfide nanoparticles embedded in N/S-codoped carbon frameworks (namely, Co3S4@C–N/S and Co9S8@C–N/S) are successfully synthesized by a subsequent solid sulfidation process. Herein, N/S-codoped carbon frameworks improve the electronic conductivity and provide more active sites for sodium storage. As the anode material in SIBs, the Co3S4@C–N/S 1.8-based anode exhibits an excellent initial charge/discharge specific capacity of 685.3/745.2 mAh g–1 with a high initial Coulombic efficiency of 91.97% at 0.1 A g–1 and a superior cycling performance (599.1 mAh g–1 in the 600th cycle at 1 A g–1 with a capacity retention of 89.4%). However, the Co9S8@C–N/S 1.8-based anode also delivers considerable initial Coulombic efficiency (86.1% at 0.1 A g–1) with high cycling stability (391.9 mAh g–1 even in the 1200th cycle at 2 A g–1 with a capacity retention of 78.1%). This study provides a material synthesis route for high-performance anode materials used in SIBs and other alkali metal-ion batteries.