Highly Stretchable Organogel Ionic Conductors with Extreme

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Highly stretchable organogel ionic conductor with extreme temperature tolerance Yiyang Gao, Lei Shi, Shiyao Lu, Tianxiang Zhu, Xinyu Da, Yuhan Li, Huaitian Bu, Guoxin Gao, and Shujiang Ding Chem. Mater., Just Accepted Manuscript • DOI: 10.1021/acs.chemmater.9b00170 • Publication Date (Web): 11 Apr 2019 Downloaded from http://pubs.acs.org on April 16, 2019

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Chemistry of Materials

Highly stretchable organogel ionic conductor with extreme temperature tolerance Yiyang Gao,†, # Lei Shi,†, # Shiyao Lu,† Tianxiang Zhu,† Xinyu Da,† Yuhan Li,† Huaitian Bu, ‡,§ Guoxin Gao,*, † and Shujiang Ding*,† †Xi'an

Key Laboratory of Sustainable Energy Materials Chemistry, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory of Electrical Insulation and Power Equipment, Department of Applied Chemistry, School of Science, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of China. ‡SINTEF Industry, Forskningsvei 1, 0373 Oslo, Norway. §Shaanxi Key Laboratory of Chemical Additives for Industry, Shaanxi University of Science and Technology, Xi'an 710021, People’s Republic of China. ABSTRACT: Stretchable ionic conductors with multifunction provide new opportunities for flexible electronics, soft robots and wearable devices. However, the practical applications of the existing stretchable ionic conductors are hampered greatly due to their poor stability. In this research, we prepared a novel organogel ionic conductor (OIC) via a simple photo-curing method of 4Acryloylmorpholine (ACMO) in propylene carbonate (PC). After carefully optimized, the as-designed OICs demonstrate many unique advantages including high transparency (93 %) in the visible region, extreme temperature tolerance (from -100 to 100 oC), superb stretchability (elongation at break of 1219 %), high ionic conductivity (7.9×10-4 S cm-1 at 25 oC), wide voltage window (5.0 V) and perfect chemical stability, these properties are not simultaneously available in hydrogels. When used as ionic conductors for stress sensors and electrolyte for LiCoO2/Li batteries, such novel OICs deliver rapid current response and excellent electrochemical stability. OICs present the extensive potential applications in flexible and wearable devices.

■ INTRODUCTION The ever-increasing market requirements for flexible and wearable devices have stimulated numerous research interests to explore high-performance ionic conductors with some unique functions. Very different from electronic conductors, ionic devices utilize ions as charge carriers to transport signals, which have enabled diverse modern technologies such as fuel cells,1,2 rechargeable batteries,3-10 solar cells,11,12 13-15 16,17 electrochemical transistors, actuators and sensors.18-23 Ionic conductors can realize new functions that are extremely difficult or even impossible to be realized by electronic conductors. Remarkably, some polymer based ionic conductors even possess some unique features including flexibility,24-27 ionic conductivity28 and ultra-high transparency,29 which can be hardly achieved by electronic conductors simultaneously. Benefiting from such unique properties, ionic conductors usher some new opportunities for flexible electronics, soft robots and wearable energy devices.30,31 For example, Sun et al. designed a highly stretchable (more than 1000% areal strain) and transparent (98 % transmittance for visible light) touch panel by using a polyacrylamide hydrogel ionic conductor.32 Additionally, R. Shepherd et al. also developed a stretchable electroluminescent skin for optical signaling and tactile sensing via sandwiching ZnS phosphor-doped dielectric elastomer between transparent hydrogel electrodes.33 Therefore, developing high-performance stretchable ionic conductors with excellent mechanical properties, broad

extreme temperature tolerance, good transparency and perfect conductivity has become a hot topic currently. Stretchable ionic conductors play a critical role in the flexible devices.34-42 But the previously developed stretchable ionic conductors are difficult to be large-scale applied in reality mainly due to their intrinsic poor temperature tolerance. As one of the widely investigated ionic conductors, hydrogels still have to face some challenges in their practical applications. Firstly, hydrogels have to be used at room temperature usually because they are subject to the melting point and boiling point of water. As is well known, high temperature will lead to the serious dehydration of hydrogels, while low temperature causes them freezing. Therefore, all of the properties of hydrogels will fail once being used in extreme-temperature condition. Recently, Vlassak and coworkers designed an antifreeing hydrogel via introducing high concentration ionic compound (CaCl2) in the polyacrylamide network and found that it still presented high stretchability and fracture toughness. Consequently, the freezing point of resultant hydrogels decreased to as low as 57 oC.43 Unfortunately, the high temperature tolerances of such hydrogels have not been investigated. Secondly, such hydrogels are not stable in air since water will volatilize unavoidably. The loss of water in the hydrogels may lead to the rapid fading in their performances. More importantly, hydrogels are used with metals (e.g. Cu, Al) usually. The existence of water and oxygen within the hydrogels will accelerate the corrosion of those metals, thus hampering the service life of these hydrogels greatly. Obviously, it is necessary to explore new noncorrosive stretchable ionic

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conductors which own good mechanical performance and extreme temperature tolerance simultaneously. Ionic gel is another kind of stretchable ionic conductors with high ionic conductivity and good mechanical stress, in which ionic liquids are employed as solvent.44-48 Liu and coworkers designed a novel double-network ionogel via locking ionic liquid (1-ethyl-3-methylimidazolium dicyanamide, [EMIm][DCA]) into charged poly(2acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS).49 Due to the strong electrostatic interaction between [EMIm][DCA] and PAMPS, the designed ionogels present ionic conductivity as high as 1.7~2.4 × 10-2 S cm-1 at 25 oC and can be used under harsh conditions (-70 oC). However, the stretchability is unsatisfied because the reported elongation at break is only 158%. Meanwhile, the fabrication process of such ionogels is complex and their shape cannot be accurately controlled, thus hindering the large-scale application of those ionogels. In this research, we develop a novel stretchable ionic conductor, namely, organogel ionic conductor (OIC), via a simple photo-curing method. During the preparation, we select an excellent organic solvent, propylene carbonate (PC), because it is a commonly used organic solvent with low biotoxicity, low melting point (-48.8 oC), high boiling point (242 oC), good dissolution ability to ionic salts, low viscosity (2.53 cP), high transparency at the whole visible region and low vapor pressure.50-52 As expected, the as-designed OICs possess high transparency (93 %) in visible region, extreme temperature tolerance (from -100 oC to 100 oC), superb stretchability (elongation at break of 1219 %), high ionic conductivity (7.9×10-4 S cm-1 at room temperature) and wide voltage window (5.0 V) as well as low modulus, high stretch ratio and no mechanical hysteresis. Remarkably, when employed as ionic conductor for stress sensor, such OICs can transport rapid current response under slight touch stress. Further evaluated as solid polymer electrolytes for LiCoO2//Li batteries, the designed OICs still deliver excellent electrochemical stability. Even exposing them on metallic collectors such as Cu and Al foils for a month in air, no corrosion can be observed, indicating good chemical stability and ultralong service life of as-prepared OICs. So our welldesigned OICs hold a great promise as stretchable ionic conductors in flexible and wearable devices.

■ RESULTS AND DISCUSSIONS To fabricate the highly stretchable and transparent organogels with excellent ionic conductivity, we employed propylene carbonate (PC) as solvent, 4-Acryloylmorpholine (ACMO) as monomer and bistrifluoromethanesulfonimide lithium (LiTFSI) as conductive lithium salt. Meanwhile, poly (ethylene glycol) diacrylate) (PEGDA) and 1-hydroxycyclohexyl phenyl ketone (photo-initiator 184) were adopted as crosslinker and photoinitiator in this fabrication, respectively (Figure 1a). The brief synthesis process of such OIC includes two facile steps: firstly, LiTFSI powder, ACMO monomer, PEGDA crosslinker and photo-initiator 184 were uniformly dispersed in PC solvent to form a transparent OIC precursor solution through violently magnetic stirring for about 30 min at room temperature. The molar percentage of PEGDA and photo-initiator 184 to ACMO were fixed at 0.1 % and 1.0 %, respectively. Correspondingly, the concentration of LiTFSI in PC solvent was controlled in 0.5 mol L-1. Then the precursor solution was injected into a glassy mold coated by PET (polyethylene

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terephthalate) paintcoat, and cured by ultraviolet (UV) light irradiation (365 nm, 400 W) for 10 min. The polymerization principle of OICs under UV light is schematically illustrated in Figure S1 (see Supporting Information). The choice of using LiTFSI as electrolyte lithium salt is mainly based on the compatibility consideration because LiTFSI can easily dissolve in most organic solvents and polymer, thus forming homogeneous transparent OICs. The photographs of cured OIC are shown in Figure 1b and Figure S1 (see Supporting Information). Distinctly, the as-prepared OICs demonstrate excellent transparency and stretchability. To disclose the feasibility of photo-cured process, we firstly tailored one pattern of Chinese word “高” with black background (Figure 1d). Then the pattern was covered onto the glass mold with organogel precursor solution and exposed under ultraviolet light for about 10 min (Figure 1c). As a result, the ultraviolet light is only allowed to pass through the blank region to make the precursor cured gradually, thus forming corresponding photo-cured organogels with the similar shape like the template with different colors (Figure 1e-g). It must be mentioned that the color of as-prepared OICs originates from the additives of colored pigments such as methylene blue (Figure 1f) and Rhodamine B (Figure 1g) during the curing process to highlight the cured samples.

Figure 1. Synthesis and properties of as-prepared OICs: (a) Molecular structures of reactants used in this research; (b) Photographs of as-prepared OICs to demonstrate excellent transparency and good stretchability; (c) Schematic illustration of photo-curing process. (d) Photograph of photo-curing template that the light is only allowed to pass through the blank area with the shape of “高”. (e-g) Photograph of photocured OICs with various colors: (e) colorless because no pigments were added, (f) blue color by adding methylene blue and (g) magenta color by adding Rhodamine B. In order to further demonstrate the good stretchability of our designed OIC, the dumbbell-like samples with the dimension of 12 mm × 2 mm × 2 mm were stretched by an electronic tensile machine (CMT 6503, MTS) with a 50 N sensor at the stretching speed of 100 mm min-1. Figure 2a presents the representative stress-strain curves of as-prepared OIC with various molar percentages of PEGDA crosslinker to ACMO monomer. Apparently, when 0.1 % of PEGDA is used as crosslinker, the as-prepared OIC demonstrates perfect stretch-ability. Its elongation at break and tensile strength

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reach 1219 % and 48.1 kPa, respectively. However, the stretchability of the OICs gradually becomes worse once the molar percentages of PEGDA increase to 0.2 % and 0.5 %, mainly due to the great

Figure 2. (a) Stress-strain curves and (b) elastic modulus of as-prepared OICs added 0.1 %, 0.2 % and 0.5 % of PEGDA crosslinker (molar ratio to monomer); (c) Tensile recovery test with the stretched ratio of 100 %, 300 %, 500% and 700 %, (d) transmittance test in the visible range and (e) Plot of impedance magnitude (|Z|) and phase angle (φ) versus testing frequency of the OICs added 0.1 % of PEDGA crosslinker; (f) Ionic conductivity of the OICs with various LiTFSI concentrations. All the measurements mentioned here are carried out at 25 oC. enhancement of the crosslinked density, which hampers their chain-segment movement and decreases their structural flexibility. Consequently, their elongations at break sharply decrease to 656 % and 171 %, respectively. Additionally, the gradients of stress-strain curves rise gradually upon the increasing of crosslinker contents, implying the enhancement of elastic modulus of as-prepared OICs. Figure 2b reveals the changes of OICs in elastic modulus through adding 0.1 %, 0.2 % and 0.5 % of PEGDA crosslinker in the system. Surprisingly, three samples all present very low elastic modulus (less than 17 kPa), implying our designed OICs own good strain resilience. Therefore, as a representative example, we tested the elasticity restore capability of the sample with 0.1 % PEGDA (Figure 2c) at room temperature. It can be seen that even when the tensile sample was stretched to 100 %, 300 %, 500 % and 700 %, respectively, it can recover quickly to its initial strain. Besides, the stretch and recovery curves overlap very well and no distinct stress hysteresis can be found between the couple curves, suggesting the superb stretch reversibility of as-designed OICs. Additionally, we also investigated the compression recovery behavior of our OICs under different temperature with the compression and recovery rate of 20 mm min-1 (Figure S3, see Supporting Information). Obviously, our designed flexible OICs can recover to their initial strain rapidly with a slightly hysteresis from -40 oC to 60 oC, presenting superb strain reversibility. Since Figure 1b implies that the designed OICs possess high transmittance, we further tested their transmittance using an UV-Vis spectrophotometer in the wavelength range of 400~800 nm. As revealed in Figure 2d, the 1-mm thick

sample was completely transparent in visible light region. Its transmittance reaches up to 93 % once the tested wavelength is over 600 nm. Remarkably, even when covered by the 1-mm OIC film, the QR code pattern still can be observed clearly (insert of Figure 2d). In order to obtain the ionic conductivity of as-designed OICs, we firstly measured their alternatingcurrent (Ac) impedances on an electrochemical workstation (CHI660E) in the frequency range of 0.1 Hz and 1.0 MHz via sandwiching a 1-mm thick sample between two stainless steels. The diameters of organogel sample and stainless steel electrodes are all 30.0 mm. As shown in Figure 2e, the obtained organogel with 0.1 % of PEGDA and 0.5 mol L-1 of LiTFSI presents distinct impedance frequency dependency, which is much similar to the commercial liquid electrolytes.38 The impedance magnitude (|Z|) sharply decreases from 738 Ω to 27 Ω at low frequency range from 10 Hz to 1 kHz, while maintains invariable at about 20 Ω at high frequency region (1 kHz-100 kHz). Meanwhile, the negative phase angle (-φ) also reveals a similar change tendency like |Z| in the total frequency range. The –φ value attenuates quickly from 70 o to about 5 o upon the frequency increasing from 10 Hz to 10 kHz, and then decreases slightly in the high frequency range of 10100 kHz. When using such organogels as ionic conductors, the practical applying frequency must be well considered. Figure S4 (see Supporting Information) reveals the Nyquist plots of as-prepared OICs with the LiTFSI concentrations of 0.1, 0.2, 0.5, 1.0 and 2.0 mol L-1. Obviously, with the LiTFSI concentrations increasing from 0.1 mol L-1 to 0.5 mol L-1, the intrinsic bulk resistances of as-prepared OICs decrease sharply from 69.0 Ω to 17.8 Ω, implying the gradual enhancement of



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ionic conductivities through improving the concentration of lithium salt. Once its concentration is over 0.5 mol L-1, however, the bulk resistance slightly increases, probably due to the worse dispersibility of LiTFSI in the whole organogel system. Correspondingly, the ionic conductivity (σ) of asprepared OICs is further calculated according to the equation: σ = L/(R·S), where L, R and S refer to thickness, contract area and bulk resistance of the tested samples, respectively. As shown in Figure 2f, the OICs present the highest ionic conductivity

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Figure 3. Thermal and electrochemical stabilities of as-prepared OICs: (a) Differential scanning calorimeter curve. (b) Dynamic thermomechanical analysis curve. (c) Thermo gravimetric analysis curve. (d) Photographs of hydrogel and organogel in -20 °C. (e) Linear sweep voltammetry curve and schematic illustration of the blocking battery. (f) The ionic conductivity test of the OICs at 50 - 75 °C. of 7.90×10-4 S cm-1 at 25 oC when the concentration of LiTFSI is 0.5 mol L-1, indicating the optimal dosage of LiTFSI in the organogel system should be 0.5 mol L-1 in order to obtain the highly conductive OICs. Furthermore, we also introduced some commonly-used lithium salts as electrolyte in the OICs to investigate their effects on the ionic conductivity. The concentrations of them are all fixed in 0.5 mol L-1. As shown in Figure S5 (see Supporting Information), only LiTFSI and LiClO4 can endow the as-prepared OICs with relatively high ionic conductivity. Further, we increased the concentration of LiClO4 from 0.5 to 1.0 mol L-1, but found that the ionic conductivities of OICs were enhanced very little. The values are 5.7×10-4 and 6.2×10-4 S cm-1, respectively. Obviously, they are both lower than that of the OICs added 0.5 mol L-1 of LiTFSI (Figure S6, see Supporting Information). Therefore, in the following discussion, unless otherwise specified, the lithium salts in the prepared OICs all refer to LiTFSI with the concentration of 0.5 mol L -1. Moreover, the influences of PEGDA crosslinker dosage on ionic conductivity are also discussed carefully as shown in Figure S7 (see Supporting Information). Distinctly, with the molar ratio of PEGDA to ACMO increasing from 0.1 % to 5.0 %, the crosslinking densities of OICs are increased quickly and thus hamper the ionic migration seriously. That leads to the quick fading in ionic conductivity once the molar ratio is over 0.1 %, further

confirming the optimal molar ratio of PEGDA to ACMO is 0.1 % in the designed OICs. In this research, we find the designed OICs show good thermal stability especially in extreme temperature. According to the DSC curve demonstrated in Figure 3a, the glasstransition temperature (Tg) of designed OICs is about -99 oC, which was further confirmed by the dynamic mechanical analysis (DMA) shown in Figure 3b. The thermal stability of as-prepared OICs was further estimated by thermogravimetric analysis (TGA) depicted in Figure 3c between 30 and 150 oC with a heating rate of 10 oC min-1 in air flow. Notably, our designed OICs only suffer from a little weight loss (about 6.5 wt%) before 100 oC, owing to the slight volatilization of PC solvent. We further put the OIC and the hydrogel at -20 oC to compare their low-temperature tolerance (Figure 3d). Distinctly, the OIC film still maintains its original transparency and flexibility, implying the excellent lowtemperature tolerance. However, the hydrogel film was frozen seriously and lost its flexibility and transparency. Therefore, our designed OICs might be used in extreme condition ranging from about -100 oC to 100 oC. Subsequently, we tested the decomposition voltage of our designed OICs for the applications such as sensors or polymer solid electrolyte in batteries. As shown in Figure 3e, the blocking battery is used in the linear sweep voltammetry test, and the current almost


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maintains constant only when the voltage is over 5 V, revealing a wide electrochemical voltage window (5 V) of our designed OICs. Meanwhile, the temperature dependence of our OICs in ionic conductivity is also investigated as shown in Figure 3f. With the tested temperature increasing from -50 oC to 75 oC, the ionic conductivities of as-prepared OICs are sharply enhanced and span several orders of magnitude. Surprisingly, the ionic conductivity can reach as high as 2.9×10-3 S cm-1 at 75 oC. Importantly, even at the extreme low temperature such as -50 oC, our OICs also provide a promising ionic conductivity of about 10-5 S cm-1. Such high ionic conductivity indicates that our OICs possess great potential as ionic conductors in sensors or energy storage devices. For example, as shown in Figure S8 (see Supporting Information), we fabricated tens of LED lamp slice arrays on our designed organogel and hydrogel substrate, respectively. As expected, the organogel can light those LED lamp slice very well at 11.7 oC in Ac electrical field, while the hydrogel cannot, owing to the electrical signal interrupt in hydrogel substrate at such low temperature. In the meantime, we exposed our OICs in air at room temperature for 30 days

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Figure 4. Using the OICs for flexible electronics: (a) The wires of the bulb is replaced with OICs and the bulb lighted up by Ac voltage of 220 V. (b) Schematic illustration and photograph of the lighted LED lamps via using as-designed OICs as flexible conductive substrates. (c) More LED lamps than (b) on the OICs. Bending the OICs, the LED lamps can still work very well. (d) Resistance-stretch time curves of OICs under Dc voltage of 3.0 V at 20 oC at 20 oC with the stretch speed of 100 mm min-1, (e)


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Gauge factors measured as a function of applied strains. (f, g) Current-strain cycling curves in the strain range of 0-100 % of the OICs at 20 oC and -20 oC, respectively. (h) Schematic illustration of an electric-double-layered-capacitive sensor by employing OICs and activated carbon sponges. (i) Chronoamperometry test of the sensor’s current changes in constant voltage through intermittent pressing the sensor. and found they can keep their origin shapes very well and hardly corrode Al or Cu foils, further showing outstanding chemical stability in air (Figure S9, see Supporting Information). Such excellent chemical stability ensures the good connection at the electrolyte-metal junctions when used as ionic conductors (e.g. solid electrolyte) in sensors or batteries, thus facilitating the organogel electrolyte to receive electrical stimuli or output electric signals rapidly. In order to highlight the advantages of our designed OICs, we also made a comparison with other reported conductive polymers in the transparency, stretchability, conductivity and temperature tolerance in Table S1 (see Supporting Information). It can be seen that our designed OICs present excellent performance. Inspired by the excellent stretchability, good transparency, extreme temperature tolerance, wide voltage window and high ionic conductivity, we subsequently applied our OICs as flexible electronic devices. We replaced the wires of a blub with OICs (Figure 4a), and the blub can work in the Ac voltage of 220 V. Furthermore, the OICs can be used as flexible conductive substrates. As shown in Figure 4b, the LED lamps are put onto the surface of the OICs and lighted by the Ac voltage successfully. Then we increased the amount of the LED lamps, and bent the OICs (Figure 4c), the LED lamps can still work very well. Besides, the OICs also present superior sensibility as sensors. As shown in Figure 4d, we applied a fixed direct current (Dc) voltage (3 V) to the OICs and stretched them at a fixed stretch speed (100 mm min-1), the resistances of OICs linearly increased at a constant speed correspondingly. Remarkably, once the OICs restored to their original length, the resistance recovered to its initial value quickly, exhibiting superior strain sensibility and excellent reversiblity. We further calculated the gauge factor (GF) of our OICs according to the reported method.53 As shown in Figure 4e, the GF value is about 1.98 within 60 % strain. It can be increased to 2.86 once the strain is over 60 %. Obviously, the as-prepared OICs-based strain sensors possess a wide sensing range with high sensitivity. Additionally, when stretched in the strain range of 0–100 % over 80 cycles at 20 oC, the sensitivity of OICs-based sensor to the current hardly changed (Figure 4f), and the signal can still be tested at -20 oC distinctly (Figure 4g). And the OICs can also monitor the signal accurately at Ac voltage (Figure S10, see Supporting Information). It is well known that the resistance change tendency is an important index for temperature sensor. So we further investigated the influence of tested temperature on the resistance of as-prepared OICs-based sensor at the Ac frequency ranges of 1, 10 and 100 kHz with a heating rate of 5 oC min-1, respectively. As shown in Figure S11 (see Supporting Information), the resistance of OICs fades rapidly with the increasing of temperature from -50 oC to 75 oC and frequency from 1 kHz to 100 kHz, disclosing outstanding temperature sensitivity of our OICs. Furthermore, an electricdouble-layered-capacitive sensor was designed via sandwiching a piece of organogel film between two pieces of activated carbon (AC) sponges/organogel composites (Figure 4h). The composites are prepared by dropwise adding the organogel precursor thermal initiator azodiisobutyronitrile (AIBN) into AC sponges uniformly, and curing them at the

temperature of 60 oC for 10 hours. When an intermittent touch pressure is given onto the surface of double capacitance touch sensors, a series of strong current peaks can be observed at the same time (Figure 4i), implying the strong stress sensitivity behavior of our designed OICs, thus enabling to be applied as pressure-sensitive sensors. As shown in movie S1, after the OICs were stuck to the finger, the movements of the finger can be monitored in real-time, also showing rapid strain sensitivity behavior of our designed OICs. Besides the applications as ionic conductor in sensors and electrical circuits, we further tried to apply them as solid electrolyte in lithium batteries, in which commercial LiCoO2 is used as anode and metallic lithium foil as cathode (Figure S12, see Supporting Information).

■ CONCLUSIONS In summary, we develop a novel organogel via a simple photo-cured process, in which PC, ACMO, PEGDA, photoinitiator 184 and LiTFSI were employed as solvent, monomer, crosslinker, photo-initiator and ionic conductive salt, respectively. When the concentration of LiTFSI is 0.5 mol L-1, and the molar percentages of PEGDA and photo-initiator 184 to ACMO are 0.1 % and 1.0 %, the as-prepared OICs possess excellent stretchability (elongation at break of 1219 %), high transparency (93 %), extreme temperature range (from -100 oC to 100 oC), wide voltage window (5 V), high ionic conductivity (7.9×10-4 S cm-1 at 25 oC) and superb chemical stability. Remarkably, when used as ionic conductors for sensors and electrolyte for lithium-ion batteries, the asprepared OICs demonstrate rapid stress sensor behavior and excellent electrochemical cycle stability, indicating a great promise in flexible and wearable devices.

■ ASSOCIATED CONTENT Supporting Information Experimental methods, supporting figures, tables, discussion, and references. Supporting figures of OICs include illustration of the polymerization principle under UV light, photograph, Nyquist plots, compression recovery curves at various temperature, ionic conductivity using different lithium salts and different molar ratio of PEGDA to ACMO, low temperature electrical performance display, current-strain cycling curves at Ac voltage, resistance changes at various temperature and frequency with a heating rate of 5 oC min-1, and electrochemical properties of as-assembled LiCoO2//Li cells using as-prepared OICs as electrolytes. This material is available free of charge via the Internet at http://pubs.acs.org.

■ AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]; E-mail: [email protected] ORCID


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Guoxin Gao: 0000-0002-1202-7281 Shujiang Ding: 0000-0002-5683-0973 Author contribution #These

authors contributed equally to this work.

Notes The authors declare no competing financial interest.

■ ACKNOWLEDGMENT This research was supported by the National Natural Science Foundation of China (No. 51773165), Project of National Defense Science and Technology Innovation Special Zone (JZ-20171102), Shaanxi Post-doctoral Foundation (2016BSHYDZZ20), Key Laboratory Construction Program of Xi'an Municipal Bureau of Science and Technology (201805056ZD7CG40). We also thank Miss Ying Hao and Miss Jiamei Liu at Instrument Analysis Center of Xi’an Jiaotong University for their assistance with UV-Vis spectrophotometer and DSC analysis.

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Highly Stretchable Organogel Ionic Conductors with Extreme

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