Dendrite-Free and Long-Cycling Sodium Metal Batteries Enabled by Sodium-Ether Cointercalated Graphite Anode

Stable and dendrite-free Na metal plating–stripping is achieved on the graphite electrode. The sodium-ether cointercalated graphite exhibits ultrahigh Na deposition efficiency of 99.86% over 900 cycles at a current density of 2 mA cm^?2. The discharge process involves the Na-ether]⁺ cointercalation and Na deposition. Density functional theory calculations demonstrate that the cointercalated graphite is critical for uniform Na deposition and stable Coulombic efficiency, which is ascribed to both the robust binding sites to Na by the diglyme molecules and a low lattice mismatch for Na growth on the cointercalated graphite. Also, a full cell consisting of Na₄Fe₃(PO₄)₂(P₂O₇) cathode and 0.5 mAh cm^?2 Na predeposited graphite anode shows excellent cycling stability. The full cell delivers a capacity of 95 mAh g^?1 based on the weight of cathode materials, with a high capacity retention of 91% over 300 cycles.