3D-printed binder-free Na3V2(PO4)3 3D cathode with adjustable porosity for sodium-ion batteries

Abstract

Designing a three-dimensional (3D) electrode structure to achieve high areal capacity in electrochemical power sources is crucial for micro-battery applications with a limited footprint. In this study, a porous 3D Na₃V₂(PO₄)₃ cathode was fabricated via 3D printing a molecular level precursor mixed with a photopolymerizable resin and subsequent pyrolysis. Compared with conventional two-dimensional (2D) electrodes, the 3D architecture without a binder allows higher loading of the active material per unit area. Moreover, the custom-designed star-shaped unit cell in the 3D architecture provides an effective electrolyte-accessible surface area and more efficient ion transport pathways, along with robust mechanical strength. By varying the beam diameter of star-shaped cells within the same cubic volume, the porosity of the 3D architecture was adjusted to realize a balance between fine mass transport and high mass loading. All these enable the 3D electrode to deliver a high areal capacity exceeding 2 mAh cm⁻² at 0.5C and a 95.9% capacity retention after 500 cycles at 5C. This work demonstrates that 3D printing is a promising strategy for fabricating 3D electrodes with customized microstructure, porosity, mass loading, and mechanical strength.