Sustainable pyrolytic carbon negative electrodes for sodium-ion batteries

Considering both sustainability and potential applications in various industrial sectors, pyrolytic carbon from the recycling of organic solid wastes can play a significant part in the unfolding energy revolution. Further innovations in circular-economy waste loops can facilitate higher economic benefits and lower environmental impacts, where a number of opportunities for improving pyrolytic carbon by choices of precursors, easy regulation of pyrolysis conditions and potential post-treatments. Here we propose a method to synthesize sustainable high-quality nanotube-like pyrolytic carbon using waste pyrolysis gas from the decomposition of waste epoxy resin as precursor, and conduct the exploration of its properties for possible use as a negative electrode material in sodium-ion batteries. The obtained pyrolytic carbon shows better cycling and rate performance than benchmark commercial hard carbon, retaining ∼105 mA h g−1 after 2000 cycles at 100 mA g−1 and exhibiting ∼57 mA h g−1 at 1 A g−1. Since the slope-dominated nature of pyrolytic carbon leads to high performance dependence on defects and pore structure, we therefore also investigate the preferred design of pore structure via pore-forming by post-treatment. It is found that reversible adsorption/desorption on defect sites and optimal pore structure are highly needed for pyrolytic carbon toward practical applications. This work highlights the potential of waste pyrolysis gas itself as a valuable feedstock for the production of value-added carbon materials. [Display omitted] •A sustainable pyrolytic carbon from waste pyrolysis gas is developed.•The resultant carbon shows higher reversible capacity than commercial hard carbon.•Investigation of closed pores provides new insights for “slope-dominated” carbon.