Chitosan-derived biochars obtained at low pyrolysis temperatures for potential application in electrochemical energy storage devices.

N-rich biochars were obtained via pyrolysis treatment of chitosan (a low-cost biopolymer from natural biomasses) at mild conditions (in the 284 °C-540 °C range), thus offering an energy efficient and low carbon footprint synthesis. These low surface area N-doped biochars were morphologically and physicochemically characterized, and tested as hosting material in lithium-sulfur (Li-S) batteries. Sulfur/biochars cathodes thus obtained showed good capacity retention and improved Coulombic efficiency compared to a standard N-rich high surface area carbon and multiwalled carbon nanotubes (MWCNT) reference substrates. Such enhanced electrochemical properties are attributable to the better retention of Li polysulfides by means of the residual functionalities still present in the biochars, thus making the valorization of chitosan potentially appealing even in the industrial sector related to the development of energy storage devices.