Biomass-derived robust three-dimensional porous carbon for high volumetric performance supercapacitors

The inherent low volumetric performance of two-dimensional (2D) carbon materials hinders their practical usage in portable devices. Three-dimensional (3D) carbon materials derived from sustainable biomass have been widely investigated but also suffer from the moderate volumetric performance. In this work, using biomass (jujube) as carbon precursor, robust 3D porous carbon with a high particle density of 1.06 g cm⁻³ is synthesized through high-temperature carbonization and subsequent activation. In three-electrode system, the electrode exhibits an ultrahigh volumetric capacitance of 476 F cm⁻³ in 6 M KOH electrolyte, which is much higher than previously reported results. The symmetrical two-electrode supercapacitor delivers excellent rate capability (75% capacitance retention at 20 A g⁻¹) as well as superior cycle stability (91% capacitance retention after 10,000 cycles) in 1 M H₂SO₄ electrolyte. Furthermore, an energy density as high as 13 Wh L⁻¹ at a power density of 477 W L⁻¹ is demonstrated in 1 M Li₂SO₄ electrolyte. The high volumetric performance of our biomass-derived porous carbon meets the requirements of portable devices and the fabrication process can be scaled up easily to industrial levels.