Peripheral octamethyl-substituted nickel(II)-phthalocyanine-decorated carbon-nanotube electrodes for high-performance all-solid-state flexible symmetric supercapacitors

Construction of advanced electrode materials with unique performance for supercapacitors (SCs) is essential to achieving high implementation in the commercial market. Here, we report a novel peripheral octamethyl-substituted nickel(II) phthalocyanine (NiMe2Pc)-based nanocomposite as the electrode material of all-solid-state SCs. The highly redox-active NiMe2Pc/carboxylated carbon nanotube (CNT-COOH) dendritic nanocomposite provides rapid electron/electrolyte ion-transport pathways and exhibits excellent structural stability, resulting in high-capacity activity and impressive cycling stability. The composite prepared with the optimized weight ratio of NiMe2Pc:CNT-COOH (6:10) showed the highest specific capacitance of 330.5 F g−1 at 0.25 A g−1. The constructed NiMe2Pc/CNT-COOH-based all-solid-state symmetric SC device showed excellent performance with a maximum energy density of 22.8 Wh kg−1 and outstanding cycling stability (111.6% retained after 35,000 cycles). Moreover, flexible carbon cloth significantly enhanced the energy density of the NiMe2Pc/CNT-COOH all-solid-state symmetric device to 52.1 Wh kg−1 with 95.4% capacitance retention after 35,000 cycles, and it could be applied to high-performance flexible electronics applications. These findings provide a novel strategy to design phthalocyanine-based electrode materials for next-generation flexible SC devices.