Activated porous carbon materials with ultrahigh specific surface area derived from banana peels for high-performance lithium-sulfur batteries

A series of banana peels derived porous carbon (BPPC) materials were fabricated by pyrolysis carbonization with different numbers of KOH activation. The Brunauer-Emmett-Teller tests indicated the number of activation effectively improves the specific surface area and pore volume of the BPPC. Amongst, the BPPC-2 (activated twice) possesses ultrahigh specific surface area (2044.57 m(2) g(-1)) and large pore volume (2.40 cm(3) g(-1)) on account of the improved hierarchical porous microstructure. After S loading process, the resultant C/S composites were introduced as cathode material in Li-S batteries. The S/BPPC-2 composite cathode exhibited a higher initial specific capacity (1481.54 mAh g(-1) at 0.1 C) and a better reversible capacity (351 mAh g(-1) after 300 cycles at 1 C) than those of others. It also exhibited excellent high rate performance even at 5 C. The enhanced electrochemical performances were ascribed to the improved specific surface area and larger pore volume of the BPPC-2, which effectively facilitated the intimate contact between sulfur and the conductive matrix, accommodating severe volume change. Besides, the micro/mesopores provided high adsorption power to inhibit the dissolution of polysulfides. This research suggested that the activation number played a key role in improving the electrochemical performance of composite cathode in Li-S batteries.