Wood based quasi-solid-state Zn-air battery with dual honeycomb-like porous carbon and cationic nanocellulose film

Conversion of low-value biomass to hierarchically porous carbon-based materials for oxygen reduction reactions (ORR), without using conventional template methods, is of particular significant for energy storage technology. Herein, dual honeycomb-like porous carbon inspired by multiscale structure of wood was assembled with cationic nanocellulose film into Zn-air battery. Nitrogen-doped hierarchically porous carbon was obtained by a simple two-step process involving alkaline extraction and pyrolysis with NH4Cl. Alkaline extraction was utilized for partially degrading lignin and heterosaccharide from unprocessed wood to create a porous wood with numerous nanopores and 3D loose structure. The inner and outer parts of obtained porous wood were further pore-optimized and doped with NH4Cl by a consequent pyrolysis step. The resulting carbon-based material (AHWC) possessed high specific surface area (1601.8 m2 g−1), well-developed hierarchical porosity, and high N content enabled excellent electrocatalytic oxygen reduction performance. Compared with commercial Pt/C catalysts in KOH electrolyte, AHWC exhibits nearly two times higher kinetic currents in the low overpotential region, comparable number of transferred electrons, and significantly higher operating stability. This carbon-based material also showed an excellent capacity and energy density equal to 792 mA h g−1 and 927 W h kg−1, together with superior long-term durability (200 h at the current density of 10 mA cm−2) when assembled as the active electrode material into a Zn-air battery. Additionally, cationic modified nanocellulose film (C-CNF-M), acting as a solid electrolyte, was assembled with AHWC for a quasi-solid-state Zn-air battery which exhibited excellent specific capacity (672.2 mA h g−1), energy density (644.11 W h kg−1) and cycling stability (500 min at 1 mA cm−2). The AHWC establish a bridge between papermaking and the field of energy storage by green conversion of biomass and fabrication of porous carbon-based materials and cellulose based electrolyte with excellent properties applicable to electrochemical energy devices.