Properties of polyacrylamide hydrogel enhanced by kaolinite with expanded layer structure

Flexible supercapacitors have attracted more and more attention due to their stable electrical properties under bending, twisting, folding and stretching conditions. However, ensuring the reliability of flexible supercapacitor hydrogel electrolytes under harsh conditions remains a challenge. Herein, we use the natural layered silicate mineral kaolinite as raw material and obtain the expanded kaolinite with a highly exposed layer surface by the intercalation-expansion method. 3-methacryloxypropyltrimethoxysilane (MPS) is grafted onto the surface of expanded kaolinite to obtain a modified expanded kaolinite sample (MPS-EK) with a crosslinker function. MPS-EK significantly enhances the properties of the polyacrylamide (PAM) hydrogel. The prepared PAM-MPS-EK hydrogel exhibits a more significant elongation at a break of 1960% with a tensile strength of 267 kPa. The electrolyte uptake and ionic conductivity are 1.5 times and 2 times higher than pure PAM hydrogel. The supercapacitor with PAM-MPS-EK hydrogel possesses outstanding cycling stability and excellent capacity retention of 91% after 16000 cycles at 5 A/g. Furthermore, this supercapacitor with PAM-MPS-EK hydrogel has excellent durability and flexibility, and it can withstand bending and hammering stimulation without evident performance degradation.