Nanoscopic decoration of multivalent vanadium oxide on Laser-Induced graphene fibers via atomic layer deposition for flexible gel supercapacitors

Composite materials for high energy/power density supercapacitors are of very high importance. The precise well-defined nanoarchitectonics approach is a key element in the construction of high-performance devices. Surface redox reactions that frequently involve the exchange of oxygen atoms are fundamental to pseudocapa-citive reactions mostly mediated by transition metal oxides (TMO). This process often changes the surface stoichiometry and atomic rearrangement in case of uncontrolled growth of TMO. Atomic layer deposition (ALD) has proven to be a facile process for smooth and uniform decoration of TMO on the electrochemically active carbon material to form a binder-free flexible composite material for supercapacitor (SC) applications. Although active carbon materials can be fabricated using various printing and lithographic techniques, continued improvement of cost and scalability, and low dimensional matrix are required to realize their full potential. Here, we demonstrate the scalable fabrication of laser-induced graphene fibers (LIGF) followed by ALD of multivalent vanadium oxide (VOx) films on the LIGF network (VOx-LIGF). The resultant VOx-LIGF shows a specific areal capacitance as high as 99 mF cm-2 at 1 mA cm-2 (aqueous solution, three-electrode cell) and 2 mF cm-2 at 0.25 mA cm-2 (gel electrolyte, two electrode cell). Moreover, the miniaturized supercapacitor device delivers a power density of 244 mW cm-3 as well as long-term cycling stability (93 % capacitance retention after 11,500 cycles) which is among the highest values achieved for any SC. Despite mechanical stress, these flexible supercapacitors maintain excellent electrochemical aspects and thus hold promise for high-power flexible and wearable elec-tronics. Such a general, precise, well-defined, and low-cost route for atomic layer deposition-laser pulse-enhanced supercapacitor materials should find widespread applications.