SnO2 Quantum Dots Enabled Site-Directed Sodium Deposition for Stable Sodium Metal Batteries.

Dendrite growth has been severely impeding the implementation of sodium (Na) metal batteries, which is regarded as one of the most promising candidates for next-generation high-energy batteries. Herein, SnO2 quantum dots (QDs) are homogeneously dispersed and fully covered on a 3D carbon cloth scaffold (SnO2-CC) with high affinity to molten Na, given that SnO2 spontaneously initiates alloying reactions with Na and provides low nucleation barrier for Na deposition. Molten Na can be rapidly infused into the SnO2-CC scaffold as a free-standing anode material. Because of the affinity between SnO2 and Na ion, SnO2 QDs can effectively guide Na nucleation and attains site-directed dendrite-free Na deposition when combined with the 3D CC scaffold. This electrochemically stable anode enables almost 400 cycles at ultrahigh current density of 20 mA cm-2 in Na symmetric battery and delivers superior cycling performance and reversible rate capability in Na-Na3V2(PO4)3 full batteries.