Waste Hemp Hurd as a Sustainable Precursor for Affordable and High-Rate Hard Carbon-Based Anodes in Sodium-Ion Batteries
Daniel Antorán, Darío Alvira, Mehmet Peker, Hugo Malón, Silvia Irusta, Víctor Sebastián, Joan J. Manyà
Abstract
High Resolution Image Download MS PowerPoint Slide The present study reports the promising potential of waste hemp-hurd-derived carbons as anodes in sodium-ion batteries (SIBs). Carbons were produced through an easily scalable process consisting of pyrolysis of raw biomass at 500 °C followed by mild chemical activation of the resulting char through wet impregnation with K 2 CO 3 and subsequent heating of the solid phase (after filtration and drying) up to 700 or 800 °C under nitrogen. The best electrochemical performance was observed for the hard carbon activated at a char-K 2 CO 3 mass ratio of 1:4 and heated up to 800 °C, which exhibited an excellent initial coulombic efficiency (73%) and achieved reversible charge capacities of 267 and 79 mAh g –1 at 0.03 and 1 A g –1, respectively. This material also exhibited an impressive cyclic stability and rate capability, with a capacity retention of 96% after 300 cycles at a current density of 2 A g –1 . This more than satisfactory performance could be related to the textural and structural features of the hard carbon, which include moderate interconnected microporosity (with pore sizes below 1 nm), an appropriate concentration of defects in the carbon structure, relatively large interplanar distances, and a certain number of closed pores.