Electronegativity-Induced Single-Ion Conducting Polymer Electrolyte for Solid-State Lithium Batteries

The application of solid polymer electrolytes (SPEs) is severely impeded by the insufficient ionic conductivity and low Li+ transference numbers (t(Li)(+)). Here, we report an iodine-driven strategy to address both the two long-standing issues of SPEs simultaneously. Electronegative iodine-containing groups introduced on polymer chains effectively attract Li+ ions, facilitate Li+ transport, and promote the dissociation of Li salts. Meanwhile, iodine is also favorable to alleviate the strong O-Li+ coordination through a Lewis acid-base interaction, further improving the ionic conductivity and t(Li)(+). As a proof of concept, an iodinated single-ion conducting polymer electrolyte (IPE) demonstrates a high ionic conductivity of 0.93 mS cm(-1) and a high t(Li)(+) of 0.86 at 25 degrees C, which is among the best results ever reported for SPEs. Moreover, symmetric Li/Li cells with IPE achieve a long-term stability over 2600 h through the in-situ formed LiF-rich interphase. As a result, Li-S battery with IPE maintains a high capacity of 623.7 mAh g(-1) over 300 cycles with an average Coulombic efficiency of 99%. When matched with intercalation cathode chemistries, Li/IPE/LiFePO4 and Li/IPE/LiNi0.8Mn0.1Co0.1O2 solid-state batteries also deliver high-capacity retentions of 95% and 97% at 0.2 C after 120 cycles, respectively.

Automated summary

This study presents an iodine-driven strategy to address the issues of insufficient ionic conductivity and low Li+ transference numbers in solid polymer electrolytes (SPEs). The introduction of electronegative iodine-containing groups effectively attracts Li+ ions, facilitates Li+ transport, and promotes the dissociation of Li salts. The iodinated single-ion conducting polymer electrolyte (IPE) demonstrates excellent ionic conductivity and Li+ transference numbers, as well as high stability in Li/Li cells and Li-S batteries, achieving high-capacity retentions when matched with intercalation cathode chemistries.