Robust and Flexible Aramid Nanofiber/Graphene Layer-by-Layer Electrodes

Abstract

Aramid nanofibers (ANFs), or nanoscale Kevlar fibers, are of interest for their high mechanical performance and functional nanostructure. The dispersible nature of ANFs opens up processing opportunities for creating mechanically robust and flexible nanocomposites, particularly for energy and power applications. The challenge is to manipulate ANFs into an electrode structure that balances mechanical and electrochemical performance to yield a robust and flexible electrode. Here, ANFs and graphene oxide (GO) sheets are blended using layer-by-layer (LbL) assembly to achieve mechanically flexible supercapacitor electrodes. After reduction, the resulting electrodes exhibit an ANF-rich structure where ANFs act as a polymer matrix that interfacially interacts with reduced graphene oxide sheets. It is shown that ANF/GO deposition proceeds by hydrogen bonding and π-π interactions, leading to linear growth (1.2 nm/layer pairs) and a composition of 75 wt % ANFs and 25 wt % GO sheets. Chemical reduction leads to a high areal capacitance of 221 μF/cm, corresponding to 78 F/cm. Nanomechanical testing shows that the electrodes have a modulus intermediate between those of the two native materials. No cracks or defects are observed upon flexing ANF/GO films 1000 times at a radius of 5 mm, whereas a GO control shows extensive cracking. These results demonstrate that electrodes containing ANFs and reduced GO sheets are promising for flexible, mechanically robust energy and power.

Highly Multifunctional Dopamine-Functionalized Reduced Graphene Oxide Supercapacitors

“…39 ANFs have been used in a variety of applications including energy storage. 22,[40][41][42][43][44][45][46][47][48][49][50][51] ANF/PEDOT:poly(styrene sulfonate) electrodes exhibited specific capacitance of 112 F/g, Young's modulus of 5 GPa, and tensile strength of 76 MPa. 48 Last year, branched aramid nanofibers (BANFs) were first reported and were shown to bear further improved mechanical properties over ANFs.…”

In Situ Complex with by‐product HCl and Release Chloride Ions to Dissolve Aramid

“…According to Figure a, similar results can also be found that peaks at δ (5.97)(a), δ (6.56)(b) and δ (7.26)(c) which belongs to H of imidazole compound all move to low field after adding PBA‐HCl and it moves more obviously with increasing amount of PBA‐HCl. Moreover, pK a of imidazole compound is nearly at 6.95 and it is larger than that of benzimidazole moiety whose pK a is nearly at 5.49 . Larger pK a brings about stronger proton affinity and makes imidazole compound more easier to complex with HCl.…”

“…Moreover, pK a of imidazole compound is nearly at 6.95 and it is larger than that of benzimidazole moiety whose pK a is nearly at 5.49. [7] Larger pK a brings about stronger proton affinity and makes imidazole compound more easier to complex with HCl. Therefore, formation of IDC is confirmed in presence of PBA-HCl and imidazole compound.…”

Fabrication, Applications, and Prospects of Aramid Nanofiber

“…Although ANF shows impressive insulation properties, its superior mechanical properties, high aspect ratio, good film‐forming property, and excellent thermal stability make it a perfect alternative to be integrated with conductive nanomaterials to construct flexible, robust, and conductive ANF‐based electronics that have promising applications in nanofluidic osmotic power generators, [ 102 ] composite electrodes, [ 103,104 ] and electromagnetic interference (EMI) shielding. [ 17 ] For example, current 2D nanofluidic architectures show low‐efficiency transport dynamics and undesirable power densities due to the insufficient charge densities of the components.…”

“…In addition, flexible graphene‐based supercapacitors have attracted increasing attention due to their outstanding electrical properties, but they suffer from inferior mechanical strength (tensile strength <15 MPa). Kwon et al [ 103,104 ] utilized ANF as a guest material to construct a reduced graphene oxide (RGO)‐based paper supercapacitor electrode, which exhibited extraordinary tensile strength (100.6 MPa) and superior electrochemical stability. As shown in Figure 18B, the abundant hydrogen bonding and π−π interactions between the RGO and ANF accounted for the impressive strength.…”