Hierarchically pyridinic-nitrogen enriched porous carbon for advanced sodium-ion and lithium-sulfur batteries: Electrochemical performance and in situ Raman spectroscopy investigations

Sodium-ion batteries (SIBs) and Lithium-sulfur (Li-S) batteries are currently receiving research because they are considered as the most potential next-generation energy storage devices. Herein, hierarchically porous carbon with enriched pyridinic nitrogen (N-HPC) is fabricated via a simple acid treatment of oxide graphene, NH4+ electrostatic adsorption and subsequent thermal treatment. Benefiting from the hierarchically porous structure and high pyridinic nitrogen doping, N-HPC can improve sodium-ion storage and Li-S batteries. In the SIBs, N-HPC delivers a high reversible sodium storage capacity and an ultrahigh rate performance because the optimized surface area and optimal nitrogen doping can provide abundant active sites, defects, voids and excellent electrical/electron conductivity. Importantly, kinetic analysis and in situ Raman spectroscopy results reveal adsorption-intercalation mechanisms for Na+ storage in N-HPC. Furthermore, Li-S batteries, used N-HPC coated-separator, display high-rate capacity and excellent cycling stability because of effective physical shield, the strongest capture ability of the lithium polysulfides and low dissociated energy of Li2S. Moreover, in situ Raman spectroscopy investigation and theoretical calculation verify the effectively reduced polysulfides shuttling and electron-withdrawing pyridinic N of N-HPC.