Benchmarked capacitive performance of a 330 μm-thick Na _x V ₂ O ₅ /CC monolithic electrode via synergism of a hierarchical pore structure and ultrahigh-mass-loading

To address the longstanding issue of conventional supercapacitors, viz. their energy and power deliveries are largely attenuated by the poor packing density of particularly the active electrodes, an ultracompact yet porous monolithic electrode is put forward in the present study. Particularly, it is built on electroactive α'-Na_xV₂O₅ with the areal mass loading amounting to 33.24 mg cm^-2 densely packed into a 330-μm-thick carbon cloth and more importantly, with a hierarchical meso-/nano-pore structure in favor of the ion transport throughout this 330 μm-thick α'-Na_xV₂O₅/CC heavy electrode. In such context, a series of superior performances including the areal, gravimetric and volumetric capacitances reaching 12.47 F cm^-2, 375.2 F g^-1 and 377.93 F cm^-3, and the energy and power densities amounting to 1.38 mW h cm^-2 and 34.1 mW cm^-2 are successfully delivered by this compact monolith at the electrode- and device-level, respectively, altogether outperforming significantly those of additional modern and promising electrodes and energy storage devices reported in the literature.