Pillar[5]arene-supported viologen networks with enhanced rate capability and cycling stability for rechargeable organic batteries

Abstract

Organic redox-active compounds are promising alternatives to traditional inorganic counterparts because of their sustainable resources and highly tunable properties. However, their solubility in organic electrolyte solvents and the sluggish electrode reactions hinder their further development. Herein, an intrinsically microporous decabromopropyl pillar[5]arene (P5Br) was used to support the methyl viologen (MV) functionality to yield two non-crosslinked and crosslinked organic electrode materials, namely MV-P5Br and CMV-P5Br, respectively. When evaluating against Li metal counter electrode, the MV-P5Br and CMV-P5Br electrodes delivered high discharge capacities of 87.9 and 92.7 mAh g−1 at 0.1 C, respectively, which are close to their theoretical values. After galvanostatic cycling at 0.1 C for 100 cycles, the CMV-P5Br electrode maintained a discharge capacity of 82.3 mAh g−1, much higher than the 43.7 mAh g−1 of the MV-P5Br electrode. When the current rate was increased to 10 C, the CMV-P5Br electrode delivered a discharge capacity of 60.7 mAh g−1, also higher than the 41.3 mAh g−1 of the MV-P5Br electrode. The increased cycling stability and rate performance of the CMV-P5Br electrode were attributed to the diminished solubility and the enhanced ion diffusion coefficient of the active material. When the counter electrode was changed to Na metal, similar results were obtained, suggesting that the CMV-P5Br electrode can also be used in Na-ion systems. This study demonstrates that the combination of crosslinked and microporous structure is highly effective to boost the electrochemical performance of organic redox-active compounds for rechargeable batteries.