Synergetic effect of nitrogen and sulfur co-doping in mesoporous graphene for enhanced energy storage properties in supercapacitors and lithium-ion batteries

Abstract

Nitrogen and sulfur co-doped mesoporous graphene (NSMG) was fabricated via a hydrothermal method followed by heat treatment utilizing graphite oxide (GO), tri-block co-polymer P123 and thiourea as the N and S source. The porous structure of the NSMG was controlled by heat treatment at 600 ​°C and 800 ​°C thus obtaining NSMG600 and NSMG800 which had specific surface areas of 966 and 1335 ​m2 ​g−1, respectively. X-ray photoelectron spectroscopy (XPS) of the NSMGs demonstrated the presence of active pyridinic-N, pyrrolic-N, graphitic-N, pyridinic N- oxide, thiophene and –SOx groups in the structure. The N and S contents and configurations were controlled by annealing temperature hence influencing the performance in supercapacitors (SC) and lithium-ion batteries (LIBs). There was improved electrolyte ion mobility and lithium-ion diffusion for both SCs and LIBs respectively. The improved performance could be attributed to the unique structural features such as plentiful defects, wrinkles, abundant pores, and N/S co-doping. NSMG600 exhibited the highest capacitance of 261 ​F ​g−1 at 0.5 ​A ​g−1 in SCs while NSMG800 showed the best performance in LIBs with a discharge capacity of 460 mAh g−1 at 100 ​mA ​g−1 with good cycling stability (440 mAh g−1) and superior rate capability. Thus NSMGs exhibit potential application in high-performance energy storage devices.