Thermal‐Gated Polymer Electrolytes for Smart Zinc‐Ion Batteries

Abstract

Smart self‐protection is essential for addressing safety issues of energy‐storage devices. However, conventional strategies based on sol‐gel transition electrolytes often suffer from unstable self‐recovery performance. Herein, smart separators based on thermal‐gated poly(N‐isopropylacrylamide) (PNIPAM) hydrogel electrolytes were developed for rechargeable zinc‐ion batteries (ZIBs). Such PNIPAM‐based separators not only display a pore structure evolution from opened to closed states, but also exhibit a surface wettability transition from hydrophilic to hydrophobic behaviors when the temperature rises. This behavior can suppress the migration of electrolyte ions across the separators, realizing the self‐protection of ZIBs at high temperatures. Furthermore, the thermal‐gated behavior is highly reversible, even after multiple heating/cooling cycles, because of the reversibility of temperature‐dependent structural evolution and hydrophilic/hydrophobic transition. This work will pave the way for designing thermal‐responsive energy‐storage devices with safe and controlled energy delivery.

Thermal Self‐Protection of Zinc‐Ion Batteries Enabled by Smart Hygroscopic Hydrogel Electrolytes

“…The conductivity (σ) of the hydrogel electrolyte can be calculated as: [ 26 ] where d and S are the thickness and area of hydrogel electrolyte, respectively. R 0 is the bulk resistance, which can be estimated on impedance spectra where the phase angle attains close to zero.…”

“…Among various methods, thermal-gated electrolytes are proved effective in mitigating this issue. [25,26] Here, we propose a new strategy using smart hygroscopic hydrogel electrolytes to achieve efficient thermal self-protection of zinc-ion batteries (see schematic in Figure 1). We first characterize the thermal response of the hydrogel followed by implementing the hydrogel electrolytes in a full Zn/MnO 2 battery.…”

Design Strategies for High‐Performance Aqueous Zn/Organic Batteries

“…[52][53][54][55][56] They often display bipolar-type redox chemistry in aqueous ZIBs.Inthe case of Zn/PANI batteries, Zn 2+ could serve as the cation species associated with the imine-related redox reaction, while the counter anions will participate in the reaction between the =NH + -a nd -NHmoieties during charge/discharge processes.A lthough they often deliver limited specific capacity (< 200 mAh g À1 )due to their low available doping level, they usually display more stable electrochemical performance in comparison with other most previous reported cathode materials.A saresult, they were usually utilized to act as the electrodes of flexible ZIBs with various configurations. [57][58][59][60][61][62] Thee lectrochemical performance of conductive polymers could be further improved by the optimization of electrolyte, [27,63] hybridization with inorganic materials, [28,[64][65][66][67] morphology regulation [68] and copolymerization. [38,[69][70][71] Forinstance,the conductive polymers could be intercalated into the interlayers of metal oxides to effectively eliminate the structural changes of them during discharge/charge processes,r esulting in excellent rate capability and long cycling life.…”

“…Although they often deliver limited specific capacity (<200 mAh g −1 ) due to their low available doping level, they usually display more stable electrochemical performance in comparison with other most previous reported cathode materials. As a result, they were usually utilized to act as the electrodes of flexible ZIBs with various configurations [57–62] . The electrochemical performance of conductive polymers could be further improved by the optimization of electrolyte, [27, 63] hybridization with inorganic materials, [28, 64–67] morphology regulation [68] and copolymerization [38, 69–71] .…”

Insights on Flexible Zinc‐Ion Batteries from Lab Research to Commercialization

“…As indicated in charge-discharge cycles (Figure 13a (ii)), a reversible thermal-induced cycling performance was observed where the charging process was inhibited by the increasing internal resistance when heating to 70 °C but reversed upon cooling. Leading on from the sol-gel transition, Niu et al [129] have proposed another strategy, which is thermoresponsive by volume shrink instead of the unstable sol-gel reaction. a-c) Reproduced with permission.…”