Armoring hydrophilic wood-structured ultrathick electrode with bimetallic nitride enables high energy-density supercapacitor

Thick electrodes can reduce the ratio of inactive constituents in a holistic energy storage system while improving energy and power densities. Unfortunately, traditional slurry-casting electrodes induce high-tortuous ionic diffusion routes that directly depress the capacitance with a thickening design. To overcome this, a novel 3D low-tortuosity, self-supporting, wood-structured ultrathick electrode (NiMoN@WC, a thickness of ~1400 μm) with hierarchical porosity and artificial array-distributed small holes was constructed via anchoring bimetallic nitrides into the monolithic wood carbons. Accompanying the embedded NiMoN nanoclusters with well-designed geometric and electronic structure, the vertically low-tortuous channels, enlarged specific surface area and pore volume, superhydrophilic interface, and excellent charge conductivities, a superior capacitance of NiMoN@WC thick electrodes (~5350 mF cm^-2 and 184.5 F g^-1) is achieved without the structural deformation. In especial, monolithic wood carbons with gradient porous network not only function as the high-flux matrices to ameliorate the NiMoN loading via cell wall engineering but also allow fully- exposed electroactive substance and efficient current collection, thereby deliver an acceptable rate capability over 75% retention even at a high sweep rate of 20 mA cm^-2. Additionally, an asymmetric NiMoN@WC//WC supercapacitor with an available working voltage of 1.0-1.8 V is assembled to demonstrate a maximum energy density of ~2.04 mWh cm^-2 (17.4 Wh kg^-1) at a power density of 1620 mW cm^-2, along with a decent long-term lifespan over 10,000 charging-discharging cycles. As a guideline, the rational design of wood ultrathick electrode with nanostructured transition metal nitrides sketch a promising blueprint for alleviating global energy scarcity while expanding carbon-neutral technologies.