Inclusion complexation enhanced cycling performance of iodine/carbon composites for lithium-iodine battery

High-performance lithium-iodine (Li-I-2) battery has gained increasing attention because of its high energy density, high power density, and low cost. However, the high solubility of iodine species in electrolyte severely deteriorates the electrochemical performance of a Li-I-2 cell. Realizing stable cycling performance of iodine cathode while retaining its high specific capacity and high Coulombic efficiency remains a huge challenge. In this work, three water-soluble nonionic polymers, including methyl-beta-cyclodextrin (M beta CD), polyvinylpyrrolidone (PVP) and amylose corn starch (ACS), are employed for coating iodine/carbon composites with a high content of iodine. The results reveal that inclusion complexes with linear iodine crystal can be formed on the surface of composites. Li-I-2 batteries using these polymer-modified iodine/carbon composites as cathode materials show enhanced electrochemical performance in terms of cycling stability and Coulombic efficiency. This study sheds light on the importance of inclusion compounds of iodine and therefore sets a pathway to fabricate high-performance Li-I-2 battery.