Engineering biomass into advanced carbon-based materials for Zn-air batteries

Facing the challenges of energy crisis and global warming, the development of renewable energy sources is getting more important. Zinc-air batteries (ZABs) have attracted much attention due to their high theoretical specific energy density, low manufacturing cost, safety and environmental benignity. Biomass-derived carbon materials have been developed as promising electrocatalysts for ZABs, due to their chemical and thermal stability, rich morphological structure, easily-modulated electronic structure, and sustainable resources. In this comprehensive review, we summarized the recent progress in the design and engineering of biomass into carbon-based oxygen electrocatalysts for ZABs, including metal-free materials, carbon materials with M-N-x-C sites, and composites of carbon and transition-metal-based materials. We discussed the construction of air electrodes from biomass-derived carbon-based materials for high-performance ZABs, and then highlighted their applications in flexible ZABs with different configuration designs.