3D-Printed Carbon Nanoparticle Monoliths Enabling Ultrahigh Mass Loading of NiCoAl Layered Double Hydroxides for Asymmetric Supercapacitors

Abstract

Supercapacitors are promising energy storage devices due to their high power density and exceptional cycling durability. However, conventional thin-film electrodes must remain limited in thickness to avoid sluggish ion transport, thereby restricting their overall charge storage capability. To overcome this challenge, we report a three-dimensional printed electrode (3D-PE) composed of hierarchically orthogonal strings interconnected by carbon nanoparticles, serving as a robust substrate for the electrodeposition of NiCoAl-layered double hydroxide (NiCoAl-LDH@3D-PE) as the cathode in an asymmetric supercapacitor. The unique 3D-PE architecture ensures efficient ion transport, enabling the fabrication of thick, monolithic electrodes with a high mass loading of up to 28.28 mg cm⁻² without compromising electrochemical performance. Furthermore, the role of Al in the NiCoAl-LDH framework was systematically investigated. Al incorporation enlarges the LDH interlayer spacing, thereby enhancing ion diffusion, electrochemical activity, and cycling stability. Among the tested compositions, NiCoAl-2-LDH@3D-PE (Ni:Co:Al = 1:1:0.2 in the deposition electrolyte) delivered a remarkable specific capacitance of 1968 F g⁻¹ at 2.5 A g⁻¹ and retained 94% of its capacity after 5,000 cycles. When paired with acid-treated carbon cloth (ATCC), the NiCoAl-2-LDH@3D-PE cathode achieved an excellent areal energy density of 0.76 mWh cm⁻² at a power density of 9.3 mW cm⁻². These results highlight the synergistic effect of 3D-printed electrode architectures and Al-modified NiCoAl-LDH, offering a promising pathway toward the design of high-performance monolithic electrodes for advanced supercapacitors and related electrochemical energy storage applications.