Development of flame-retardant ion-gel electrolytes for safe and flexible supercapacitors

• Published in: Science China materials 2023-08, Vol.66 (8), p.3129-3138
• Main Authors: Wang, Zhe, Wang, Lin, Jiang, Wanyuan, Jian, Xigao, Hu, Fangyuan
• Format: Article
• Language: English
• Subjects: Ambient temperature; Chemistry and Materials Science; Chemistry/Food Science; Crosslinking; Dimensional stability; Electrochemical analysis; Electrodes; Electrolytes; Flame retardants; Flexibility; Ion currents; Materials Science; Mechanical properties; Nonaqueous electrolytes; Supercapacitors; Thermal stability
• ISSN: 2095-8226; 2199-4501
• DOI: 10.1007/s40843-023-2470-3

The presence of organic electrolytes in typical liquid supercapacitors ultimately results in inadequate safety and poor flexibility, which limits the development and application of supercapacitors. Thus, we developed an easy-to-prepare ion-gel supercapacitor with strong flame-retardant properties, thermal stability, flexibility, and good electrochemical characteristics. Specifically, this ion-gel supercapacitor provides excellent performance by using the in situ cross-linking of ion-gel electrolytes on electrodes. The introduction of ether-containing flexible chain segments to the ion-gel electrolyte results in a high ionic conductivity (6.5 × 10 −3 S cm −1 ) at an ambient temperature, and the in situ cross-linking results in a tight interfacial contact between the electrolyte and electrode. The ion-gel supercapacitor retains a stable electrochemical performance while bending due to the tight interfacial contact and excellent mechanical characteristics. Furthermore, incorporating the diazonaphthone structure in the cross-linked electrolyte renders the ion-gel electrolyte excellent flame-retardant properties and thermal stability, allowing it to sustain dimensional stability at 150°C for 30 min. The supercapacitor with the optimized ion-gel electrolyte has a specific capacity of 105 F g −1 and an energy density of 41.6 W h kg −1 . The results of this study provide a practical method for preparing and optimizing ion-gel cross-linked electrolytes.