Mangosteen peel-derived porous carbon: synthesis and its application in the sulfur cathode for lithium sulfur battery

Porous carbon with various structures from micropores (< 2 nm) to hierarchical pores (0–4 nm) was synthesized from biomass waste mangosteen peels via KOH activation process. Microporous carbon was obtained mainly at a low activation temperature of 700 °C or a low alkali/carbon of 3. Hierarchical porous carbon with ultrahigh surface area (> 3000 m 2  g −1 ) and pore volume (> 1.4 cm 3  g −1 ) was obtained at alkali/carbon ratio higher than 3.5 and activation temperature of 800 °C. Sulfur with a high content of 65 wt% was able to be fully accommodated into the pores of hierarchical porous carbon to form C/S composite cathode for lithium sulfur battery while in the case of microporous carbon, residual sulfur on carbon surface was detected. High specific discharge capacities of more than 800 mAh g −1 were achieved from hierarchical porous carbon/S composites at 0.5 C, and the sample synthesized at alkali/carbon of 4 and activation of 800 °C exhibits the best cycling performance. After 500 cycles at 0.5 C, a high discharge capacity of 509 mAh g −1 was maintained, indicating an excellent capacity retention. Relationship between pore characteristics of porous carbon and the electrochemical performance of its sulfur composite was discussed.