Energy‐Storage Electrodes: Room‐Temperature Metallic Fusion‐Induced Layer‐by‐Layer Assembly for Highly Flexible Electrode Applications (Adv. Funct. Mater. 30/2019)

Abstract

In article number 1806584, Seung Woo Lee, Jinhan Cho, and co‐workers report a room‐temperature metallic fusion‐induced layer‐by‐layer assembly that can produce highly flexible paper electrodes with bulk‐metal like electrical conductivity. The introduced small‐molecule linkers minimize the separation distance between neighboring silver nanoparticles (Ag NPs), and consequently induce the metallic fusion of multilayered Ag NPs at room temperature without additional treatment.

Nanoparticle‐Based Electrodes with High Charge Transfer Efficiency through Ligand Exchange Layer‐by‐Layer Assembly

“…Recently, Cho and co‐workers reported novel types of LbL self‐assembly for functional NPs based on the in situ ligand exchange reaction between the hydrophobic ligands of NP and amine (NH 2 )‐functionalized organic linkers in organic media. [ 50–57,104 ] In this process, the high affinity of amine moieties to metal surfaces (via covalent bonds) [ 105–108 ] effectively induces the replacement of insulating hydrophobic ligands of NPs with hydrophilic incoming ligands (i.e., HN 2 ‐functionalized dendrimers), showing dramatic changes in the surface chemistry ( Figure a). As the deposition time of the NH 2 ‐dendrimer layer increased, the characteristic peaks originating from the hydrophobic ligand (i.e., PA) gradually disappeared, and new peaks arising from the hydrophilic moiety NH 2 were observed, indicating the complete removal of insulating ligands from the NPs.…”

“…This unique characteristic also implies that the output performance of NP‐based electrodes, such as electrical conductivity, catalytic activity, and areal capacity, can be improved through consecutive deposition of NPs. [ 55,128–132 ] That is, by simply increasing the bilayer number ( n ), the thickness and mass of NP‐based multilayers are regularly increased without significant NP agglomeration, which can be expanded up to a micrometer‐scale thickness irrespective of substrate size and shape (Figure 3e). [ 104 ] The scalability of this approach is highly advantageous in achieving high volumetric and areal energy densities, which are considered valuable performance factors in practical and commercial energy storage systems.…”

“…Recently, it has been reported that various hydrophobic ligands on inorganic NPs (i.e., metal and TMO NPs) can be easily replaced by amine (NH 2 )‐functionalized small ligands (or linkers) with a low molecular weight ( M w ) through in situ ligand exchange reactions during the solution‐based electrode assembly process ( Figure a). [ 50–57 ] The ligand exchange reaction is induced by the differences in the binding energies of ligands to NPs using a short‐chain amine‐functionalized ligand having a higher binding energy and a long‐chain ligand attached to the NPs with a lower binding energy. Therefore, the short‐chain ligands can replace the long‐chain ligands on the NPs during the solution‐based layer‐by‐layer (LbL) deposition process to assemble bulk electrode materials consisting of 3D interconnected nanoparticles through molecule linkers.…”

Interfacial Design and Assembly for Flexible Energy Electrodes with Highly Efficient Energy Harvesting, Conversion, and Storage

“…This phenomenon can be explained by the metallic fusion behavior induced by a reduction in the interparticle distance. [ 140 ] Similarly, self‐sintering of PAA‐Ag NPs at room temperature could occur via ligand replacement of bulky PAA with the Cl – ions of dissolved NaCl during the drying of water‐based ink (Figure 3c). [ 139 ] This ligand exchange reaction occurred because the Ag NPs have a higher affinity for halides (especially the halogen atom), such as NaCl, HCl, and KCl, than for the native PAA ligand (i.e., the carboxylate ion).…”

High‐Resolution Printable and Elastomeric Conductors from Strain‐Adaptive Assemblies of Metallic Nanoparticles with Low Aspect Ratios

“…[ 31 ] Despite the high conductivity of the printed traces, sometimes even close to that of the bulk metal, they are not intrinsically stretchable owing to the lack of defect‐tolerating mechanism, unless they are wrinkled or shaped as origami structures. [ 32,33 ] Metallic NPs combined with elastomers are a potential solution to improve stretchability. With a presumption that NPs may easily lose contact during stretching, NPs are coated on elastomeric fibers [ 16,17 ] or serve as excellent complement to the high‐aspect‐ratio nanofillers [ 19,26 ] for enhancing the overall stretching conductance.…”