3D-printed binder-free Na 3 V 4 (PO 4 ) 3 3D cathode with adjustable porosity for sodium-ion batteries

Abstract

Designing a three-dimensional (3D) electrode structure to achieve high areal capacity of electrochemical power sources is crucial for micro-battery applications with limited footprint.In this study, a porous 3D Na 3 V 2 (PO 4 ) 3 cathode was fabricated via 3D printing a molecular-level precursor-mixed photopolymerizable resin with subsequent pyrolysis.Compared with conventional two-dimensional (2D) electrodes, The 3D architecture without binder allows higher active material loading on 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 in 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 delivery a high areal capacity exceeding 2 mAh•cm - 2 at 0.5 C and a 95.9% capacity retention after 500 cycles at 5 C. This work demonstrates that 3D printing is a promising strategy for fabricating 3D electrodes with customized microstructure, porosity, mass loading, and mechanical strength.