Phosphoric acid involved laser induced microporous graphene via proton conducting polybenzimidazole for high-performance micro-supercapacitors

Abstract

Functional electrodes with unique ion storage and rapid ion migration properties through microstructure and chemical-doping modulation are always crucial for rapid charging devices such as micro-supercapacitors (MSCs). In this work, proton exchange membrane named phosphoric acid (PA) doped polybenzimidazole membrane (PA-PBI) is studied as a unique precursor for assembling laser induced graphene (LIG) based electrodes (PA-PBI-LIG) in MSCs, toward the enhancement of energy storage performance via simultaneous heteroatoms doping, microporous structure improving and proton-conducting substrate introducing. By tuning PA concentration, the microporous structures perform adjustable specific surface area from 20.2 to 384.46 m2 g−1, thereby enhancing changeable capacitance from 2.44 mF cm−2 to 149 mF cm−2, with highest specific energy density of 20.7 μWh cm−2. To understand the mechanism, PA and the initiated free radicals are proposed to motivate microporous formation and heteroatoms doping during laser fabrication via unique laser absorption properties of PA. Additionally, PA-PBI substrates work synergistically on ions migration with microporous graphene, potentially promoting energy storage efficiency especially in the acid-based electrolyte. Overall, the raised PA-PBI-LIG electrodes simultaneously promote microporous, heteroatomic and multilayered graphene with proton conducting substrate, which show great potentials in micro energy storage devices.