Self‐Recovering Tough Gel Electrolyte with Adjustable Supercapacitor Performance

Abstract

Tough and self-healable hydrogels have been prepared by the multiple supramolecular interactions of clay nanosheets with dendritic polymers or in situ-formed polymer. [ 10 ] Many workers have studied ionic gels formed by the supramolecular effect of ionic liquids and block copolymers with/without SiO 2 nanofi ller, which also demonstrate the high mechanical modulus. [ 11 ] Here, we employ a mild self-initiated UV polymerization to prepare an ionic conducting polymer gel, whose non-covalent crosslinking interaction can endow the conducting gel compressive toughness and self-recovering ability.Our system consists of four components: 1-ethyl-3-methylimidazolium chloride (EMIMCl), hydroxyethyl methacrylate (HEMA), chitosan (CS) and water, whose molecular structures have been shown in Figure 1 A. At fi rst, CS and HEMA are dissolved in EMIMCl via heating and cooling process, which forms a viscous solution from the solid of EMIMCl (Figures S1a and 1C). The destroy of crystal structure of EMIMCl is the main reason to form such homogeneous solution, which is caused by the dissolution of CS and HEMA through hydrogen bond. [ 12 ] Then, tough EMIMCl gels can be formed by irradiating the asprepared homogeneous solution with UV light (Figures S1b and S2; Figure 1 D). The UV-generated Cl radicals from EMIMCl (Figure 1 B) are the initiator for the polymerization of HEMA. [ 13 ] The physical gelation of our EMIMCl gel without crosslinker should be ascribed to the hydrogen bonding interactions between the hydroxyl group in PHEMA, the amine group of CS and imidazolium group in solvent. Interesting is that our EMIMCl gel is miscible with water, which has a slightly decrease strength but a sharply increase ionic conductivity (Figure 1 E). As shown in Figure S3, water exists in the form of free water and bound water, and is relatively stable at room temperature ( Figure S4). The fi nal EMIMCl/water gel exhibits the water and pressure controlled ionic conductivity, which is suitable as an appropriate electrolyte and separator in fl exible supercapacitors. The detailed preparation, mechanism and properties are shown as followed.The EMIMCl gels can be formed by irradiating the as-prepared homogeneous solution under 45 minutes UV light with intensity of 22.4 mw/cm 2 at 365 nm. The component ratio of the conducting gel is optimized by the comprehensive evaluation of the electrochemical performances and mechanical strength. Finally, a varying amount of water was injected into the EMIMCl gel to form EMIMCl/water gels with 5 to 50 wt% (by mass) water content (Figure 1 E). If the water was added in advance, the fi nal gel could not be obtained. The EMIMCl/water gel shows high toughness when they underwent large deformations and show good strength under compression ( Figure 2 Flexible devices are a mainstream direction in modern electronics and related multidisciplinary fi elds. [ 1 ] Concerning fl exible capacitors and batteries, the current research is mainly focused on the fabrication of fl exible electrode materials; [ 2 ] however, ele...

A Flexible Ionic Liquid Gelled PVA‐Li2SO4 Polymer Electrolyte for Semi‐Solid‐State Supercapacitors

“…Therefore, PVA:BMIMCl:Li 2 SO 4 = 1:3:2.2 is optimal proportion in PVA-BMIMCl-Li 2 SO 4 FGPE, which is selected for further investigations. The maximum ionic conductivity value (37 mS cm −1 ) is higher than that of any other reported lithium salt GPEs, [32][33][34][35][36] and IL GPEs [ 1,37 ] ( Table 1 ).…”

“…The results clearly demonstrate that this fl exible electrolyte is mechanically robust. The concentration of water is also another crucial factor for the electrical performance of PVA-BMIMCl-Li 2 SO 4 FGPE, which highly depends on the amount of Li 2 SO 4 , as is shown in Figure 1 250 °C), [ 1 ] proportionally increases when the Li 2 SO 4 content rises. The trace water also contributes to the ionic conductivity without infl uencing the cycle stability of the PVA-BMIMClLi 2 SO 4 FGPE.…”

“…[ 1,2 ] Flexible semi-solidstate electric double-layer supercapacitors (EDLCs or SCs) have emerged as a new class of energy storage devices and attracted considerable attention in recent years due to their small size, low weight, ease of handling, and excellent reliability. They can be used as energy storage devices for fl exible and wearable electronics in a wider range of operating temperatures compared with conventional EDLCs.…”

“…However, their low conductivities restrict the electrochemical performance in semi-solid-state supercapacitors. [ 1,16,17 ] The ionic conductivity can be improved further with a wide operation electrochemical window after the addition of neutral inorganic salts in the GPE, which opens up new access to high-performance EDLCs, but related researches are lacked. …”

Hydrogel with Aligned and Tunable Pore Via “Hot Ice” Template Applies as Bioscaffold

“…The conductivity ( σ ) was measured using alternating-current impedance. [ 29 ] Amazing is that the conductivity is anisotropic in the aligned AG gel, which meanwhile confi rms an anisotropic inner structure. The aligned gel has a high ionic conductivity (71.9 ± 0.7 mS cm −1 ) when treated with an electric fi eld parallel to pore axis.…”