Swelling-resistant microgel-reinforced hydrogel polymer electrolytes for flexible all-in-one supercapacitors with high performances

In the past few years, in situ polymerization of polyaniline (PANI) on a hydrogel polymer electrolyte (HPE) has been usually employed to fabricate flexible all-in-one supercapacitors, but many HPEs suffer from severe swelling during in situ deposition, resulting in poor mechanical properties or low electrochemical performances of supercapacitors. Here, a swelling resistant poly(2-acrylamide-2-methylpropanesulfonic acid)/polyacrylamide microgel reinforced (PAMPS/PAM MR) double network HPE with high ionic conductivity, good mechanical properties and excellent anti-freezing properties was prepared by two-step radical polymerization and followed by soaking the hydrogel in H3PO4 solution. After the deposition of PANI on the HPE, an all-in-one flexible supercapacitor could be successfully prepared. The PAMPS/PAM MR HPE showed swelling resistance during long-time deposition of PANI. The prepared supercapacitor exhibited excellent tensile strength (234 kPa), high specific capacitance (441 mF cm−2 at 1.0 mA cm−2), high-power density (762.30 μW cm−2) and high flexibility. The supercapacitor also demonstrated outstanding anti-freezing properties. We believe the swelling resistance of the HPE as well as the all-in-one supercapacitor can provide new insights into the next generation of supercapacitors with high electrochemical performances.