Metalized Polyacrylates as Efficient Binder for a Sulfurized Polyacrylonitrile/Polydopamine Active Material in Sulfur Cathodes for Room Temperature Sodium–Sulfur Batteries

Promising binder systems with special chemical and mechanical functions are under extensive exploration to cope with serious volume change and harmful shuttle effect occurring during charge/discharge cycles of a sulfur cathode in sodium–sulfur (Na–S) batteries. In this aspect, sulfurized polyacrylonitrile (SPAN)/polydopamine (PDA) active materials are combined with different metalized polyacrylates (MPAAs) to result in a SPAN/PDA/MPAA binder system with peculiar morphology and superior mechanical and interfacial strengths. As the outer layer of SPAN/PDA/MPAA, MPAA can extend its long chains to interact with cathode components and, moreover, metal ions of MPAA can participate in the beneficial electron transport process. The results suggest that stability and electrochemical performance of the sulfur cathodes depend on the applied metal ions, which become better and better as the valence of metal ions change from mono (Na), di (Ca), and tri (Fe) to tetra (Ti). Cathode derived from SPAN/PDA/titanium polyacrylate (TiPAA) shows the best stability and electrochemical performance, exhibiting a rather high specific capacity of 1438 mAh g–1 at 0.2 C for 100 cycles and 1271 mAh g–1 at 1 C for 300 cycles. Hopefully, this study can provide a foundation on how to use different metal ions to manipulate the electrochemical performance of sulfur cathode in Na–S batteries.