Sodium‐Ion Pump Enhanced Composite Sodium Anode Toward Fast‐Charging and Practical N/P Ratio Solid‐State Sodium Metal Batteries

Abstract Solid‐state sodium metal batteries (SSSMBs) employing NASICON‐type solid‐state electrolytes and sodium metal anodes promise enhanced safety and high‐energy density, yet the poor anodic interface compatibility induced growth of Na dendrites and excessive consumption of sodium metal still hinder their application. In this work, a 3D porous carbon‐supported ultrathin sodium anode with superionic conductivity and high diffusivity is designed on the surface of the NASICON electrolytes, which serve as sodium‐ion pump to improve the sodium‐ion‐transfer kinetics. The fast ion/electron transfer within the composite anode effectively solved the problem of rapid consumption of Na + and local charge accumulation at the anodic interface, thereby achieving dendrite‐free Na deposition. A high critical current density of 3.5 mA cm −2 and a long cycling life of 6000 h at 0.2 mA cm −2 are achieved for the symmetrical cells. Coupled with Na 3 V 2 (PO 4 ) 3 cathode, the full cells exhibit a high‐capacity retention of 90.2% after 5100 cycles at 10 C. Most importantly, SSSMBs using a limited Na metal anode paired with 17.3 mg cm −2 Na 3 V 2 (PO 4 ) 3 cathode (1.05 negative/positive capacity ratio) deliver an outstanding capacity retention of 97% for 100 cycles. This work demonstrates a promising ultrathin Na anode toward the development of practical and sustainable high‐performance SSSMBs.