3D printed Au/rGO microlattice host for dendrite-free sodium metal anode

Sodium metal, featuring a high theoretical capacity and the lowest redox potential, is a promising anode for sodium metal batteries (SMBs). Nonetheless, issues related to the sodium metal's undesired volume expansion and dendrites formation upon cycling have greatly retarded its practical implementation. Herein, we report a robust substrate for Na metal via a novel 3D printing technology. The 3D printed Au/rGO electrodes are capable of delivering remarkable cycling lives over 2000 h (1 mA cm⁻², 1 mAh cm⁻²) and 1200 h (5 mAh cm⁻², 5 mAh cm⁻²) respectively. Even at 8 mAh cm⁻², 8 mAh cm⁻², an Au/rGO electrode still sustains a stable operation over 220 h. In-situ optical microscopy clearly demonstrates a dendrite-free Na ion deposition process on an Au/rGO electrode surface. Moreover, in-situ X-ray diffraction (XRD) characterization and theoretical calculations unraveled mechanisms for the stable Na ion deposition. Upon assembling with a 3D printed Na₃V₂(PO₄)₃@C cathode (∼15.2 mg cm⁻²), obtained SMBs deliver a reversible capacity of 84.95 mAh g⁻¹ at 100 mA g⁻¹ after 205 cycles. This work establishes an alternative 3D printing strategy for enhancing Na deposition chemistry for high-energy-density SMBs.