Carbon Coated Bimetallic Sulfide Hollow Nanocubes as Advanced Sodium Ion Battery Anode

Sodium ion battery (SIB) as a next-generation battery has been drawing much attention due to the abundance and even distribution of sodium source. Metal sulfides with high theoretical capacity and good electrical conductivity are promising anode candidates for SIB, however, the structural collapse caused by severe volume change during the de/sodiation process typically results in a fast capacity decay, limited rate capability, and cycling stability. In this work, by careful composition and structure design, polydopamine coated Prussian blue analogs derived carbon coated bimetallic sulfide hollow nanocubes (PBCS) are prepared with distinguished morphology, higher surface area, smaller charge transfer resistance, and higher sodium diffusion coefficient than the uncoated bimetallic sulfides. An optimum carbon coated bimetallic sulfide hollow nanocube anode delivers a specific capacity of ≈500 mA h g⁻¹ at 50 mA g⁻¹ with ethylene carbonate/dimethyl carbonate (1:1, vol%) electrolyte in the presence of fluoroethylene carbonate additives. A capacity of 122.3 mA h g⁻¹ can be realized at 5000 mA g⁻¹, showing good rate performance. In addition the carbon coated bimetallic sulfide hollow nanocubes can maintain capacity of 87 mA h g⁻¹ after being cycled at 500 mA g⁻¹ for 150 times, indicating its good cycling stability. The structure integrity, high specific capacity, good rate performance, and cycling stability of PBCS render it a promising anode material for advanced SIB.