Enhancing Performance Stability of Electrochemically Active Polymers by Vapor‐Deposited Organic Networks

Abstract

Performance stability of electrochemically active polymers (EAPs) remains one of the greatest and long-standing challenges with regard to EAP-based technologies for a myriad of energy, biomedical, and environmental applications. The performance instability of EAPs originates from their structural alteration under repeated charge-discharge cycling and/or flexing. In this work, a conceptually new "soft confinement" strategy to enhance EAP performance stability, including cyclic and mechanical, by using rationally designed, vapor-deposited organic networks is presented. These chemically cross-linked networks, when in contact with an electrolyte solution, turn into ultrathin, elastic hydrogel coatings that encapsulate conformally the EAP micro-/nanostructures. Such hydrogel coatings allow easy passage of ions that intercalate with EAPs, while simultaneously mitigating the structural pulverization of the EAPs and/or their detachment from substrates. Fundamentally distinct from extensively studied "scaffolding" or "synthetic" approaches to stabilizing EAPs, this soft confinement strategy relies on a postmodification step completely decoupled from the EAP synthesis/fabrication, and enjoys the unique advantage of substrate-independency. Hence, this strategy is broadly applicable to various types of EAPs. The proposed stability enhancement strategy is demonstrated to be effective for a range of EAP systems with differing chemical and morphological characteristics under various testing conditions (repeated charging/discharging, bending, and twisting). electronic devices. [14][15][16] Possible mecha nisms causing the cycling instability of EAPs include structural pulverization due to repeated swelling and shrinkage of polymer backbones, and collapse of initially present ion channels resulting in difficulty of subsequent redoping. [14,[17][18][19][20] A widely adopted approach to enhancing EAP stability is integration of the EAPs with conductive scaffolds, such as porous graphite foams, [21] carbon nanotube sponges, [22] nickel foams, [23] and partially exfoliated graphite. [18] These scaffolds are usually porous and dimensionally stable, and thus act as robust supports for EAP films to reduce their structural alteration. Such a "scaffolding" approach relies on effective hybridization of the EAP with the underlying conductive substrate, a non trivial task. The integration process often requires judicious surface modification of the scaffold materials to create specific interactions (e.g., covalent bonding, π-π stacking) with the EAP, and a lengthy screening process to determine the reac tion conditions for the growth of a certain EAP on the scaffold. A few less common methods based on deliberate synthetic strategies for improving EAP stability have also been dem onstrated, such as creation of supramolecular structures, [24] synthesis of hyperbranched EAPs, [25] and dopant/EAP engi neering. [26,27] These scaffolding and synthetic approaches have shown great promise when applied to certain types of EAP sys tems, but are highly...

Oxidative Molecular Layer Deposition of Amine-Containing Conjugated Polymer Thin Films

“…The 5:1 and 20:1 cycle ratios would be expected to result in the highest electrochemical capacity in an aqueous electrolyte by disrupting azo formation, but we expect that the hydrophilic nature of the resulting branched structure depicted schematically in Figure e may facilitate dissolution in the aqueous electrolyte employed in Figure , giving rise to the lower capacity and more rapid capacity loss for these cycle ratios in Figure g. We note that the capacity loss we observe for all of the compositions in Figure g is common for redox-active polymers and is typically attributed to densification and/or chemical decomposition. , The capacity loss may be addressed in future work by adjusting the potential window, ,, introducing monomer substituents, and/or modifying the polymer surface. , …”

“…92,93 The capacity loss may be addressed in future work by adjusting the potential window, 32,94,95 introducing monomer substituents, 96 and/or modifying the polymer surface. 93,97 To further confirm our understanding of how altering the Py/PDA cycle ratio impacts the molecular structure within the polymer films, we performed nonaqueous CV measurements on pure PDA/MoCl 5 oMLD films (0:1 Py/PDA cycle ratio) and the 1:1 and 5:1 cycle ratio copolymers, as depicted in Figure 7. In these measurements, we observe that as we increase the number of Py cycles, we observe a decrease in the redox activity in the potential window for azo formation (i.e., more reducing potentials of 1.7−0.9 V vs Na/Na + in Figure 7).…”

Conductive Hydrogel‐Based Electrodes and Electrolytes for Stretchable and Self‐Healable Supercapacitors

“…In addition to conductive PANI hydrogel, conductive PPY hydrogel is also feasible for energy storage because of its various attractive features, including decent electrical conductivity, superior redox reversibility, excellent biocompatibility, facile synthesis as well as high durability. [ 158,197–199 ] As mentioned above, by virtue of direct cross‐linking of PA without insulating polymer matrix, similar to that for preparing PANI hydrogel, pure PPY CHs can be obtained. [ 88 ] Due to the 3D hierarchical porous structure and the excellent conductivity of the PPY hydrogel, the assembled SCs showed excellent charge transfer and storage capability as well as excellent endurance against bending and folding.…”

Multifunctional Cement‐Based Composite with Advanced Self‐Sensing, Electrothermal, and Electrochemical Properties

“…Furthermore, new peaks at 171 and 234 eV, corresponding to the S 2p and S 2s, respectively, are observed, indicating the incorporation of sulfate dopants within the PPy coating. [51][52][53] To enhance the understanding of surface modification, high-resolution XPS analyses of the C 1s and N 1s peaks were conducted. Figure 5f-g presents the high-resolution XPS spectra of the C 1s region of the brick substrate before and after the PPy coating, respectively.…”