Biomaterial-derived porous carbon doped with heteroatoms as a separator coating for high-energy–density Zn-I batteries

Abstract Chitin and phytic acid are abundant sustainable resources commonly found in shrimp shells, crab shells, and various plants. However, they are underutilized, and their biomass value is frequently underestimated. To address this, the current study developed a strategy to synthesize efficient separator coatings for zinc-iodine (Zn-I) batteries using chitin and phytic acid as carbon sources (biochar). First, nanosheets of porous carbon doped with N and P (NP-PC), featuring multiple active sites, are synthesized through in situ carbonization of chitin and phytic acid. Subsequently, the synthesized materials are coated onto the surfaces of glass fiber (GF) separators, effectively addressing several persistent challenges associated with Zn-I batteries. Notably, the modified separator (NP-PC@GF) enhanced the rapid-discharge capability of the involved battery, effectively inhibited the diffusion of intermediate polyiodide species, stabilized the electrolyte interface, suppressed irreversible dendrite formation, and increased I utilization efficiency. Consequently, the battery demonstrated high electrochemical performance, with an initial capacity of 7.8 mAh cm–2 at 20 mA cm–2, an initial specific capacity of 8.9 mAh cm–2 under high I loading, and a retention rate of 56% (5.1 mAh cm–2) at the 174th cycle. Overall, this research demonstrates the effective use of biochar for separator modification, facilitating the development of high-performance Zn-I batteries. Graphical Abstract