Constructing an artificial cathode-electrolyte interface to stabilize high-loading iodine electrode based on positively charged chitosan for high-energy and stable flexible zinc-iodine batteries

Flexible zinc-iodine batteries (FZIBs) are promising flexible power supply devices due to their intrinsic safety and high theoretical energy density. However, the relatively low mass loading and the simultaneous shuttling phenomenon of the active iodine species in the iodine cathode jointly result in limited areal capacity and areal energy density of the FZIBs. Herein, we construct a cathode-electrolyte interface (CEI) layer based on bio-sustainable positively charged chitosan (p-Chitosan) on the iodine cathode to locate iodine species and restrict the polyiodide shuttling effect through strong electrochemical interaction. Under the ultra-high iodine loading of 14.6 mg cm −2 , the FZIBs delivered a high specific capacity of 209.1 mAh g −1 at a current density of 0.2 A g −1 , thus presenting a high areal capacity (2.56 mAh cm −2 ) and high areal energy density (2.96 mWh cm −2 ). Additionally, the capacity of the flexible battery based on the p-Chitosan CEI layer remains nearly unchanged when bending at various angles of 0°, 30°, 60°, 90°, 120°, and 150°, respectively. The flexible battery bending at an angle of 60° can stably operate over 1100 cycles, suggesting its potential as a flexible power supply.