Hydrogel‐Based Flexible Energy Storage Using Electrodes Based on Polypyrrole and Carbon Threads

Abstract

Developing new flexible and electroactive materials is a significant challenge to producing safe, reliable, and environmentally friendly energy storage devices. This study introduces a promising electrolyte system that fulfills these requirements. First, polypyrrole (PPy) nanotubes are electropolymerized in graphite‐thread electrodes using methyl orange (MO) templates in an acidic medium. The modification increases the conductivity and does not compromise the flexibility of the electrodes. Next, flexible supercapacitors are built using hydrogel prepared from poly(vinyl alcohol) (PVA)/sodium alginate (SA) obtained by freeze–thawing and swollen with ionic solutions as an electrolyte. The material exhibits a homogenous and porous hydrogel matrix allowing a high conductivity of 3.6 mS cm−1 as‐prepared while displaying great versatility, changing its electrochemical and mechanical properties depending on the swollen electrolyte. Therefore, it allows its combination with modified graphite‐thread electrodes into a quasi‐solid electrochemical energy storage device, achieving a specific capacitance (Cs) value of 66 F g−1 at 0.5 A g−1. Finally, the flexible device exhibits specific energy and power values of 19.9 W kg−1 and 3.0 Wh kg−1, relying on the liquid phase in the hydrogel matrix produced from biodegradable polymers. This study shows an environment friendly, flexible, and tunable quasi‐solid electrolyte, depending on a simple swell experiment to shape its properties according to its application.

3D-Polyacrylamide/Ti-MXene: A Newer Hybrid Hydrogel Electrolyte Featuring High Mechanical Strength and Durability for Flexible Aqueous Zinc-Ion Batteries

“…After 30 days, the OCP of 2 M ZnSO 4 LE rapidly falls to 0.4 V due to the poor interface between the electrode and the electrolyte and also rapid dendrite growth formation (Figure a). However, in the case of HHGE, it exhibits an OCP of 1.7 V, indicating its improved stability of the cell over time and reduced degradation of the electrolyte and electrode interface, leading to a more durable energy storage system (Figure b). , …”

“…However, in the case of HHGE, it exhibits an OCP of 1.7 V, indicating its improved stability of the cell over time and reduced degradation of the electrolyte and electrode interface, leading to a more durable energy storage system (Figure 9b). 49,55 Its corresponding charge−discharge studies at different current densities are shown in Figure 10a. The long-term cycling stability of 0.5 Ag −1 was performed over 500 cycles and exhibited a stable performance with a capacity retention of 82% over 500 cycles and a Coulombic efficiency of 100% (Figure 10b).…”

3D printing of hydrogels for flexible micro‐supercapacitors

“…Utilizing aqueous electrolytes characterized by high ionic conductivity can greatly enhance the conductivity of hydrogels. 57 The hydrophilic functional groups within the polymer networks contribute to the water retention capability of hydrogels, allowing them to absorb a significant volume of aqueous electrolytes. Aqueous electrolytes consist of both cations and anions charge carriers and water as a solvent, as depicted in Figure 4B.…”

“…Hydrogels exhibit high ionic conductivity, rendering them well‐suited for energy storage applications, particularly as electrolytes. Utilizing aqueous electrolytes characterized by high ionic conductivity can greatly enhance the conductivity of hydrogels 57 . The hydrophilic functional groups within the polymer networks contribute to the water retention capability of hydrogels, allowing them to absorb a significant volume of aqueous electrolytes.…”

Functional Gel-Based Electrochemical Energy Storage

“…Physical cross-linking preparation methods are based on hydrogen bonds and electrostatic interactions. 138 In this case, the precursors must interact with water molecules between the chains while allowing the diffusion of the liquid phase. 139 Differently, chemical cross-link methods form stronger networks than physical methods and are based on forming covalent bonds between the polymer and a crosslinker.…”