Flexible Antifreeze Zn-Ion Hybrid Supercapacitor Based on Gel Electrolyte with Graphene Electrodes

Abstract

Zn-ion energy storage devices employing hydrogel electrolytes are considered as promising candidates for flexible and wearable electronics applications. This is because of their safe nature, low cost, and good mechanical characteristics. However, conventional hydrogel electrolytes face limitation at subzero temperatures. Herein, we report an antifreezing, safe, and nontoxic gel electrolyte based on the poly­(vinyl alcohol) (PVA)/Zn/ethylene glycol system. The optimal gel electrolyte membrane exhibits a high ionic conductivity (15.03 mS cm–1 at room temperature) and promising antifreezing performance (9.05 mS cm–1 at −20 °C and 3.53 mS cm–1 at −40 °C). Moreover, the antifreezing gel electrolyte can suppress the growth of Zn dendrites to display a uniform Zn plating/stripping behavior. Also, a flexible antifreezing Zn-ion hybrid supercapacitor fabricated with the optimum antifreezing gel electrolyte membrane exhibits excellent electrochemical properties. The supercapacitor possesses a high specific capacity of 247.7 F g–1 at room temperature under a high working voltage of 2 V. It also displays an outstanding cyclic stability at room temperature. Moreover, the supercapacitor shows an extraordinary electrochemical behavior and cyclic stability over up to 30 000 cycles at −20 °C under a current load of 5 A g–1, demonstrating its outstanding low-temperature electrochemical performance. Besides, the antifreezing supercapacitor device also offers high flexibility under different deformation conditions. Therefore, it is believed that this work provides a simplistic method of realizing the application of flexible antifreezing Zn-ion energy storage devices in a subzero-temperature environment.

Regulating Interfacial Ion Migration via Wool Keratin Mediated Biogel Electrolyte toward Robust Flexible Zn‐Ion Batteries

“…In Figure 2c, we systematically summarized the comparison of the cycling lifespan, voltage hysteresis at low current density and fixed areal capacity between CWK biogel electrolyte and some literatures reported gel electrolyte or modified separator adopted symmetric Zn batteries. [23,27,[35][36][37][38][39] Overall, the CWK hybrid biogel electrolyte enhanced Zn anode manifests distinguishing cycling stability among all reported systems, [17,[40][41][42][43][44][45][46][47][48][49] which also beyond that of other enhancement strategies, including electrolyte additives and Zn anode direct decoration (Tables S1-S4, Supporting Information). Furthermore, the power density of the Zn-ion battery is also imposed by the rate performance of Zn anode, which verified via Zn symmetric batteries under increased current density.…”

Flexible and Wearable Zinc-Ion Hybrid Supercapacitor Based on Double-Crosslinked Hydrogel for Self-Powered Sensor Application

“…At a current density of 1.0 mA cm −2 , the discharge capacitance of the ZHS device is as high as 1.364 F cm −2 , while the capacitance remained at 1.244 F cm −2 when the current density was further increased to 2.0 mA cm −2 . The calculated energy density for the ZHS device was 242 Wh kg −1 at a power density of 228 W kg −1 , i.e., superior to those of other sandwich-structure supercapacitors ( Figure 3 d) [ 25 , 26 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. The cyclic stability test of the ZHS ( Figure S6 ) showed 90% retention after 1000 cycles, indicating stable charge–discharge performance.…”

“…( d ) Comparison of energy density and power density among reported cutting-edge supercapacitors. (Yang, 2020 [ 25 ]; Liu, 2021 [ 26 ]; Chen, 2019 [ 33 ]; Zhang, 2021 [ 34 ]; Ding, 2021 [ 35 ]; Sandhiya, 2020 [ 36 ]; Khazaeli, 2020 [ 37 ]; Li, 2020 [ 38 ]; Sun, 2018 [ 39 ]) ( e ) Ragone plots of the ZHSs with the hydrogel prepared with different Zn 2+ concentrations. ( f ) Discharge capacitance of ZHS at different temperatures.…”

“…Liu et al designed a gel electrolyte based on a polyvinyl alcohol (PVA)/Zn/ethylene glycol system. This electrolyte exhibited an ionic conductivity of 15.03 mS cm −1 at room temperature and maintained good ionic conductivity properties at low temperatures (9.05 mS cm −1 at −20 °C and 3.53 mS cm −1 at −40 °C) [ 26 ]. Moreover, through a solid-state zwitterionic hydrogel electrolyte design, Lu et al fabricated the ZHS with a voltage window of 2.4 V and a maximum energy density of 286.6 Wh kg −1 at a power density of 220 W kg −1 [ 27 ].…”

Flexible Quasi‐Solid‐State High‐Performance Aqueous Zinc Ion Hybrid Supercapacitor with Water‐in‐Salt Hydrogel Electrolyte and N/P‐Dual Doped Graphene Hydrogel Electrodes

“…To date, there are two strategies proposed to enhance the anti-freezing abilities of hydrogel electrolytes. One is to introduce freezetolerant agents, [39] and the other is to use the concentrated salts [17b] confirmed in the aforementioned DSC analysis. As depicted in Figure 6d and Figure S13 (Supporting Information), the flexible ZHSC can keep powering the LED and the timer which were connected in parallel even at − 15 and 65 °C.…”