One-Step Fabrication of Ice-Templated Pure Polypyrrole Nanoparticle Hydrogels for High-Rate Supercapacitors

Conducting polymer hydrogels with high conductivity, excellent electroactivity, and good mechanical strength are desirable for the design of high-performance energy storage devices. However, they suffer from the issue of low porosity, which hinders electrolyte diffusion and leads to poor rate performance. In this work, we developed a one-step, in situ chemical polymerization approach to fabricate a porous pure polypyrrole hydrogel (PPH) with a desirable nanostructure via an ice-templating strategy. This simple synthetic approach offers the PPH tunable porosity, ultrahigh conductivity, and good mechanical strength. Owing to these notable advantages, functioning as a supercapacitor electrode, PPH displays a high specific capacitance of 265 F g–1 (1961 mF cm–2) at 1.35 A g–1 (10 mA cm–2) and maintains 85% capacitance retention even up to 67.6 A g–1 (500 mA cm–2). We also found that PPH without an ice-templated nanostructure possesses poor rate capability due to slow and blocked electrolyte diffusion because of the less-porous nanostructure. This facile, ice-templated strategy to structurally design a porous nanostructure for high-rate performance opens up the possibility for advanced energy storage applications.