Kevlar‐Based Supercapacitor Fibers with Conformal Pseudocapacitive Metal Oxide and Metal Formed by ALD

Kevlar, poly(p-phenylene terephthalamide) (PPTA), yarns are modified for use as flexible supercapacitor electrodes by coating them with a nanometer-scale film of conductive platinum metal and pseudocapacitive V2O5 using atomic layer deposition (ALD). The PPTA yarns are incorporated into a solid-state supercapacitor through the use of a polyvinyl alcohol/lithium chloride gel electrolyte. Pseudocapacitive V2O5 films 11 nm thick provide up to a 5× increase in areal capacitance (18.4 mF cm−2) over the Pt-only-coated PPTA. Thicker films of V2O5 and wrapping the electrodes together into a single yarn result in decreased areal capacitance due to charge-transfer limitations. The work describes how ALD metal and metal oxide can be combined to add double layer and pseudocapacitive charge storage to mechanically robust PPTA creating unique multifunctional electronic fabric device systems.