High-strength, stretchable, and self-recoverable copolymer-supported deep eutectic solvent gels based on dense and dynamic hydrogen bonding for high-voltage and safe flexible supercapacitors

Deep eutectic solvent (DES)-based gels, with their biocompatibility, non-volatility, low cost, and electrochemical stability, have attracted widespread interest as novel solid-state ionic conductor for flexible devices. However, fabrication of tough and stretchable DES gels is challenging due to the insufficient understanding of the interactions between polymers and DES. The development of tough DES gels based on hydrogen bonding is attractive but also challenging due to the possible competitive hydrogen bonds between the hydrogen bond-rich choline chloride-based polar DES and polymers. Herein, tough copolymer-supported DES gels with dual-cross-linked dissipative network were fabricated through copolymerization of methacrylic acid and N, N-dimethylacrylamide monomers with good and poor compatibility with DES to promote the formation of stable hydrogen bonds between polymers in the DES. The resulting DES gels were stiff, tough, stretchable, and self-recoverable, with tensile strength, breaking strain, Young's modulus, toughness, and recovery ratio being 2.08 MPa, 792%, 1.76 MPa, 12.88 MJ m−3, and 76%, respectively. The mechanical properties of DES gels could be widely tuned by varying the monomer ratio and solvent structure changes. The carbon-based supercapacitor based on the DES gel shows stable voltage window to 2 V and exhibits the specific capacitance of 93.25 F g−1 at 2 A g−1.Graphical abstractAn ultratough and stretchable copolymer-supported DES gel ionic conductor with high tensile strength of 2.08 Mpa, high toughness of 12.88 MJ m−3, stretchability of 792%, and excellent recovery properties are facile fabricated for flexible electronics through copolymerization of two monomer pairs of methacrylic acid and N, N-dimethylacrylamide that can form stable hydrogen bonds in the DES environment with a small amount of chemical cross-linker to form a dual-crosslinked dissipative network.