Using core-shell interlinked polymer@C-iodine hollow spheres to synergistically depress polyiodide shuttle and boost kinetics for iodine-based batteries

Rechargeable iodine-based batteries have attracted much attention owing to their high energy density and low cost, but the inferior kinetics and high iodine solubility severely restrict their practical applications. In the present study, hollow core-shell interlinked polymer@C-iodine spheres were developed to promote the comprehensive characteristics of the iodine electrode. A facile "top-down" synthesis process is used in the present study. The "top" precursor was prepared based on an n-doped hollow carbon sphere (NHCS)-iodine substrate, which was connected and filled with polyvinylpyrrolidone (PVP)-iodine polymer solution. After the solvent was evaporated, the polymer contracted and the shell-core interlinked units were fabricated, resulting in the "down" product, i.e. Polymer@C-iodine spheres. It not only has a highly conductive and porous substrate to accelerate electrochemical kinetics, but also possesses strong chemical interactions between PVP and iodine to restrict the polyiodide shuttle. Herein, for the first time, the redox mechanism of the polymer@C-iodine spheres is explained, and moreover, their synergistic effects on accelerating electrochemical kinetics and promoting thermal stability are demonstrated. The improved kinetic and thermal characteristics are favorable to their superior rate capability, long-term cycling stability and low polyiodide shuttle, which make them a good cathode candidate for iodine-based batteries. Moreover, the superior high-rate long-term cycling properties of four kinds of iodine-based batteries, namely lithium-iodine systems, sodium-iodine systems and iodine-carbon (lithium-ion and sodium-ion) full batteries, which are based on the polymer@C-iodine spheres further demonstrate their wide applicability and high efficiency. This work not only provides a new strategy to fabricate high-performance electrodes, but also provides some new insights into developing iodine-based electrochemical systems with low cost, high safety and high performance.