Stretchable alkaline quasi-solid-state electrolytes created by super-tough, fatigue-resistant and alkali-resistant multi-bond network hydrogels

Hydrogel-based quasi-solid-state electrolytes (Q-SSEs) swollen with electrolyte solutions are important components in stretchable supercapacitors and other wearable devices. This work fabricates a super-tough, fatigue-resistant, and alkali-resistant multi-bond network (MBN) hydrogel aiming to be an alkaline Q-SSE. To synthesize the hydrogel, a 2-ureido-4[1H]-pyrimidone (UPy) motif is introduced into a poly(acrylic acid) polymer chain. The obtained MBN hydrogels with 75 wt% water content exhibit tensile strength as high as 2.47 MPa, which is enabled by the large energy dissipation ability originated from the dissociation of UPy dimers due to their high bond association energy. Owing to the high dimerization constant of UPy motifs, the dissociated UPy motifs are able to partially re-associate soon after being released from external forces, resulting in excellent fatigue-resistance. More importantly, the MBN hydrogels exhibit excellent alkali-resistance ability. The UPyGel-10 swollen with 1 mol/L KOH display a tensile strength as high as ∼1.0 MPa with elongation at break of ∼550%. At the same time, they show ionic conductivity of ∼17 mS/cm, which do not decline even when the hydrogels are stretched to 500% strain. The excellent mechanical property and ionic conductivity of the present hydrogels demonstrate potential application as a stretchable alkaline Q-SSE.