A mechanically strong and self-adhesive all-solid-state ionic conductor based on the double-network strategy

Abstract

Ionic conductors have great application prospects in the field of flexible electronics, but the widely used hydrogels and ionic gels suffer from water loss of hydrogels and leakage of ionic liquids, so all-solid-state ionic conductors are more adaptable to complex and variable environments. Nevertheless, material design solutions for all-solid-state ionic conductors that can balance mechanical strength and tensile properties and cohesion and adhesion simultaneously are still rare. The lack of excellent self-adhesive and mechanical properties will limit the applicability and stability of all-solid-state ionic conductors for various applications (e.g., in the field of self-adhesive flexible sensing). Therefore, based on the double-network strategy, the stretchable and self-adhesive poly(AA-CDC) type supramolecular deep eutectic polymer was selected as the first network and the rigid and adhesive lignin as the second network to synthesise high-strength, high-stretch and high-adhesive all-solid-state double-network ionic conductors (ADNICs). Among them, ADNICs are rich in polymer networks with dynamic hydrogen bonding and have extremely strong mechanical properties (tensile strength, strain at break and toughness of ADNIC-0.5 can reach 13.59 MPa, 1013% and 115.04 MJ m⁻³, respectively), and can instantly form various interfacial interactions with various substrates (adhesion strength reaches 5500 N m⁻¹) and firmly adhere to various substrates. At the same time, the decrease in its adhesion strength is less than 15% after 5 cycles of separation-re-adhesion. In addition, it has strong self-healing properties (electrical self-healing efficiency up to 90% in 0.4 s at room temperature), good electrical conductivity (9.63 × 10⁻³ S m⁻¹), and adequate transparency (∼85% in the visible range). Due to their ease of preparation and exceptional comprehensive performance, ADNICs would facilitate the exploration of utilizing all-solid-state ionic conductors in flexible electronic devices.