Spirulina-derived nitrogen-doped porous carbon as carbon/S composite cathodes for high cyclability lithium-sulphur batteries

Spirulina was used for the first time as a raw nitrogen-doped porous carbon source to synthesize carbon/sulphur (carbon/S) composite cathodes for lithium-sulphur batteries. The composites consisting of sulphur and spirulina-derived carbon with micro- and meso-pores showed an obvious carbon encapsulating sulphur structure. The carbon/S cathodes exhibited much better electrochemical performance than pristine sulphur, delivering an initial discharge capacity of 662 mAh g −1 with nearly 60% capacity retention after 100 cycles at 1 C current density (1670 mA g −1 ). The improved electrochemical stability of the composites can be ascribed to the synergistic effects between the encapsulation of sulphur by spirulina-derived carbon and adsorption of polysulfides on N doped carbon lattice. These effects successfully prevented or retarded the shuttle effect of sulphur cathodes.