Porous carbon derived from rice husks as sustainable bioresources: insights into the role of micro-/mesoporous hierarchy in hosting active species for lithium-sulphur batteries

The exploration of natural resources as sustainable precursors affords a family of green materials. Exploring highly abundant and available biowaste precursors remaining from food processing throughout a scalable and cost-effective material synthesis path is highly important especially for new materials discovery in emerging energy storage technologies such as lithium-sulphur (Li-S) batteries. Herein, we have produced a series of carbon materials with hierarchical micro-/mesopores from a very cheap and abundant lignocellulosic bio-waste, namely rice husk. The carbonisation of the lignocellulosic fraction leads to the formation of micropores while the removal of the silica present naturally in the rice husk composition allows the formation of mesopores. We can easily tune the ratio of micropores to mesopores by simply tuning the synthesis conditions in order to achieve an optimal performance in Li-S batteries after sulphur infiltration into the resulting porous carbons. Our optimal cathode scaffold for Li-S batteries exhibited a high capacity of 1032 mA h g(-1) at a current density of 0.1 C. An ultralow decay rate of 0.055% per cycle was achieved. The appearance of abundant micropores with a higher surface area renders a high initial capacity of sulphur to polysulphides; however, the sufficient mesopore volume is more vital for a lower cyclic decay, which is prerequisite for the generation of solid products and smooth ion diffusion. This work, besides reporting on an efficient method to produce efficient electrode materials from waste to be used in energy storage technologies also provides fresh insights into the required structural features to allow effective cathode materials for high-performance Li-S batteries.