Two Birds with One Stone: Hydrogel-Derived Hierarchical Porous Activated Carbon toward the Capacitive Performance for Symmetric Supercapacitors and Lithium-Ion Capacitors

Templates are known to serve as critical components for synthesizing porous materials; however, their removal in some cases is time-consuming and not eco-friendly. Inspired by the hydrogels, a hierarchical porous activated carbon (HPAC) material is successfully prepared in this study through a pyrolysis procedure of polyvinylpyrrolidone (PVP)-derived hydrogel under an argon atmosphere at 900 °C. The numerous water molecules captured within the PVP hydrogel matrix can be regarded as greener templates, thus significantly enhancing the specific surface area of the resultant HPAC to 2012 m2/g. In addition to the physicochemical and structural characterizations, the capacitive performances of hydrogel-derived HPAC electrode materials with 5.1 mg/cm2 of mass-loading are further explored as applied to symmetric supercapacitors and lithium-ion capacitors. As the results, their remarkable reversible capacitances outputted from the former (117.5 F/g at 0.13 A/g; 77.6 F/g at 1.3 A/g) and the latter (128.7 F/g at 0.1 A/g; 73.6 F/g at 10 A/g) are revealed. Such favorable results are attributed to distinctive textural properties of hydrogel-derived HPAC and synergistic features of the resulting electrode by the presence of a hydrophobic binder and one-dimensional conductive additive.