A wearable fiber-shaped supercapacitor based on a poly(lactic acid) filament and high loading polypyrrole

There is a growing interest in fiber-shaped supercapacitors, which are likely to meet the demands of wearable electronics. However, the loading of active material is so small that the energy density of fiber supercapacitors is low. In this research, a graphene oxide/poly(pyrrole) (GO/PPy) hybrid was applied as the active material and a novel method to accomplish a high loading of the active material on poly(lactic acid) (PLA) filaments is proposed. Iron ions, as positive ions, are intercalated into GO sheets to form complexes which can be absorbed on the surface of the PLA. Furthermore, iron ions can be used as initiators to initiate pyrrole polymerization. Using complexes in which iron ions are intercalated into GO, instead of pure GO, then coated onto PLA and then polymerized using pyrrole, this method could effectively increase the loading of PPy. As a result, the active material loading is 0.121 mg cm^-1, and the weight gain rate even reached 72.4%. A high areal specific capacitance of 158.8 mF cm^-2 and energy density of 3.5 μW h cm^-2 are achieved using the proposed fiber-shaped supercapacitor. Meanwhile, it shows great potential for textile shaped electronics because of its fiber format.