Lithium-Conducting Organic Solid Electrolyte for Organic Rechargeable Batteries: Boronated Benzoimidazole-Linked Polymer

Abstract

Some of the Benzimidazole-linked polymers (BILPs) are a class of porous organic polymers that have high porosities, large specific surface areas, and high thermal and chemical stability. Owing to these properties, BILPs can be used in various applications including solid electrolytes for renewable energy utilization. In this study, we carried out the boran-modification of a kind of BILPs, in order to increase the Li ion conductivity by decreases the interaction between lithium ions and the anion backbone. The resulting B-TFB-HAB-BILP materials have an ionic conductivity of 2.9 × 10−6 S cm−1 at 30 °C, which increases to 1.4 × 10−4 S cm−1 at room temperature with the addition of the ionic liquid, PP13[TFSA]. This can be attributed to the suppression of resistance at the grain boundary. A coin cell with an organic cathode active material, B-TFB-HAB-BILP/PP13[TFSA] as the quasi-solid electrolyte, and Li foil as the anode exhibited an initial discharge capacity of 223 mAh g−1 (76 % of theoretical capacity). Our study can aid in the realization of organic rechargeable batteries with high gravimetric energy density.