Role of high-defect biocarbon for achieving iodine efficient anchoring and rapid conversion in Zinc-iodine battery

Abstract Zinc-iodine (Zn–I 2 ) batteries are promising due to their safety and capacity, however, the system encounters challenges such as polyiodide shuttling and slow iodine kinetics. Here, four bio-based carbon materials with different defect densities were investigated to explore their effects on the rapid iodine conversion kinetics and polyiodide anchoring. In-situ testing indicates that abundant defects enhance the redox kinetics of I 2 /I − by achieving a highly reversible conversion process of I − /I 3 − /I 5 − /I 2 and facilitate the anchoring of polyiodides. Consequently, the peanut carbon loading with I 2 (I 2 @PEC) exhibits optimal performance, demonstrating a retention of 81.1% of its capacity when the current increases 80-fold to 16 A g −1 , and maintaining 97% of its initial capacity after 50,000 cycles. This work outlines design principles for electrodes to enable high-performance Zn-I 2 batteries, and the straightforward fabrication route readily enables large-scale production.