PxSy nanoparticles encapsulated in graphene as highly reversible cathode for sodium ion batteries

Herein, phosphorus-mediated sulfur nanoparticles encapsulated in reduced graphene oxide nanosheets (P-SrGO-T) were successfully synthesized as the cathode for sodium ion battery by a ball milling and the following thermal treatment. A series of covalent bonds, such as P–S, C–S–C, C–O–P and C–S–P, are formed in this process, which are in favor of fixing the sulfur and suppressing the parasitic shuttle effect of polysulfide. Benefiting from the graphene sheets and these covalent bonds, a high reversible capacity of 637.4 mAh/g was achieved in P-SrGO-T after 100 cycles at the current density of 0.2 A/g. In addition, P-SrGO-T also delivers a high-rate capacity (330.7 mAh/g at 5 A/g) attributing to low charge transfer resistance and faster ion diffusion kinetic. This work pushes the progress forward in developing phosphosulfide cathode for sodium ion batteries.