Highly Stretchable, Self-Recoverable, and Conductive Double-Network Gels Containing Deep Eutectic Solvent for a Flexible Supercapacitor and Strain Sensor

Due to the advantages of high ion density, low volatility, non-toxicity, and low cost, deep eutectic solvent gels have attracted widespread interest as novel solid-state ionic conductors for flexible devices. However, most of the currently developed deep eutectic solvent gels have weak mechanical properties, which seriously hinder their large-scale application. Herein, tough and ultrastretchable agar-based double-network deep eutectic solvent gels were successfully fabricated through the self-assembly of agar at a concentration range of 2% to 6% in a choline chloride/urea/water eutectic mixture (ChCl:urea:H 2 O = 1:2:1) by heating–cooling to form the first physical dissipative network and combination with the second Al 3+ -cross-linked hybrid poly(acrylic acid) (PAA) network. Such a double-network and multi-bond design endow the obtained 22 wt.% polymer scaffold-supported deep eutectic solvent gels with good mechanical properties (high tensile strength of 216 kPa and toughness of 2112 kJ m −3 ), stretchability (breaking strain of 1566%), good self-recovery ability (91% recovery efficiency after 600% strain deformation), and high room-temperature ionic conductivity of 2.1 mS cm −1 . Furthermore, agar-based double network deep eutectic solvent gels were successfully used as stretchable gel electrolytes for the fabrication of electric double-layer capacitors and reliable flexible sensors with excellent electrochemical performance over a wide strain range. Graphical Abstract A nonvolatile agar-based double-network gel containing a deep eutectic solvent with high toughness of 2112 kJ m −3 , high stretchability of 1595%, excellent recovery property, and ionic conductivity of 2.1 mS cm −1 is fabricated for flexible electronics by the self-assembly of agar in a choline chloride/urea/water eutectic mixture (ChCl:urea:H 2 O = 1:2:1) to form the first physical dissipative network and combination with a second Al 3+ -cross-linked hybrid PAA network.