Redox active polymer metal chelates for use in flexible symmetrical supercapacitors: Cobalt-containing poly(acrylic acid) polymer electrolytes

The novel polymer metal chelate electrolytes (polychelates) were prepared by incorporation of cobalt sulfate (Co) into poly(acrylic acid) (PAA) host matrix. Quasi-solid state supercapacitor devices were fabricated using polychelates, PAA-CoX (X: 3, 5, 7, and 10) where X represents the doping fraction (w/w) of Co in PAA. All polymer metal electrolytes were showed excellent bending-stretching properties, thermal stability and electrochemical durability with an optimum ionic conductivity of 3.15 × 10−4 S cm−1. Hierarchically porous activated carbon and nano-sized conductive carbon were used to form carbon composite symmetrical device electrodes. The electric double-layer capacitor (EDLC) and redox reactions of Co-incorporated polychelates at the interfaces of porous activated carbon provided an optimum specific capacitance of 341.33 F g−1 with a device of PAA-Co7, which is at least 15 times enhancement compared to the device of pristine PAA. The PAA-Co7 device also provided energy density of 21.25 Wh kg−1 at a power density of 117.69 W kg−1. A prolonged cyclic stability of the device exhibited superior capacitive performance after 10,000 charge–discharge cycles and the maintained 90% of its initial performance. In addition, the supercapacitor with a dimension of 1.5 cm × 3 cm containing PAA-Co7 successfully operated the red-blue-green (RGB) LED light.