Enhanced Na+ pseudocapacitance in P, S co-doping carbon anode: raising from the surface modification by sulfur and phosphorus with C-S-P coupling

Enhanced phosphorus (7.2 wt%) and sulfur (15.7 wt%) co-doped carbon (PSC) is synthesized via one step sintering the carbon disulfide and red phosphorus in vacuum. It is found that S atoms can act as immobilization sites for phosphorus by covalently bonding with P atoms in the form of C-S-P, thus high-level doping of phosphorus can be realized. Owing to the high-level doping, this co-doped carbon shows enlarged interlayer spacing, improved charge transfer capability and strong adsorption of Na+ ions. When tested as anode for sodium ion batteries, this PSC delivers a high reversible capacity of 513.8 mAh g-1 at 100 mA g-1, excellent rate capability of 181.8 mAh g-1 at 10 A g-1 and superior cycling stability of a capacity of 290.1mAh g-1 after 1000 cycles at 1A g-1.