∼2.5 nm pores in carbon-based cathode promise better zinc-iodine batteries

Abstract

The relationship mechanism between the material pore structures and cathodic iodine chemistry plays a vital role in efficient Zn-I2 batteries, but is unclear, retarding further advances. This work innovatively indicates a great contribution of ∼2.5 nm pore structure of nanocarbons to efficient iodine adsorption, rapid I− ↔ I2 conversion, and polyiodide inhibition, via scrupulously designing catalysts with controllable pore sizes systematically. The I2-loading within the designed nitrogen-doped nanocarbons can reach up to as high as 60.8 wt%. The batteries based on the cathode deliver impressive performances with a large capacity of 178.8 mAh/g and long-term cycling stability more than 4000 h at 5.0 C. Notably, these is no polyiodide such as I3− and I5− detected during the charge-discharge processes from comprehensive electrochemical cyclic voltammetry, X-ray photoelectron spectroscopy, and Raman technique. This work provides a novel knowledge-guided concept for rational pore design, promising better Zn-I2 batteries, which is also hoped to benefit other advanced energy technologies, such as Li–S, Li-ion, and Al–I2 batteries.