Hydrangea-like MnO2@sulfur-doped porous carbon spheres with high packing density for high-performance supercapacitor

The high packing density of electrode materials is crucial for the miniaturization and lightweighting of energy storage devices. Nevertheless, a structural contradiction among high packing densities, sufficient ion, and electron transport channels is a challenge. In this research, a unique hydrangea-like compose (MnO₂@S-PCS-5) is synthetized by a convenient and environmentally friendly method. The composite comprises a spherical carbon material matrix and MnO₂ nanosheets, resulting in a high packing density of 1.79 g cm⁻³. Furthermore, the hydrangea-like structure exhibits a high number of active sites, facilitating ion transport and exhibiting excellent specific capacitance (Cv: 328.7 F cm⁻³). The asymmetric supercapacitors (MnO₂@S-PCS-5//YP-50) exhibit a maximum energy density of 38.4 Wh kg⁻¹ at a power density of 500 W kg⁻¹, with a wide voltage window of 2.0 V. The results demonstrate densification is important for miniaturization of energy storage devices.