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

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 Na3V2(PO4)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 Na3V2(PO4)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.