Mediating iodine cathodes with robust directional halogen bond interactions for highly stable rechargeable Zn-I2 batteries

Abstract

The ease of I2 sublimation and dissolution into aqueous electrolyte media impedes the validity for the further utilization of rechargeable Zn-I2 batteries. To overcome such constraints, we herein put forward a valid strategy by strengthening interactions between I and host reservoirs with -I···Y- halogen bonds (Y refers to O, S, N etc.). Distinct vibrational shifts in spectroscopy detections and markedly elevated thermostability have verified the presence of halogen bonds bridged between I2 and biomass-evolved graphitic/porous carbon microtubes (GP-CMTs). Notably, GP-CMTs exhibit far more robust I2/I−-anchoring ability than conventional carbon hosts, capable of preventing undesired actives dissolution. The derived I2@GP-CMTs cathodes show an output capacity of 285 mAh g−1, good Columbic efficiency, salient rate capabilities (101 mAh g−1 at 12 A g−1) and cyclic durability (86.8% capacity retained after 103 cycles). In-situ Raman detection affirms the cathode charge storage relies on direct reversible I−/I2 transition, and operando microscope observations reveal there exist paralleled changes in electrolyte phase. Packed full cells also show excellent cyclic behaviors, suppressed self-discharge rate and impressive energy density. Our work offers a fresh/effective strategy to upgrade electrode systems, for not only metal-I batteries but also other prototype cells with similar kinetic issues.