Homogeneous guiding deposition of sodium through main group II metals toward dendrite-free sodium anodes.

Metallic sodium is a potential anode material for rechargeable sodium-based batteries because of its high specific capacity and low cost. However, sodium commonly suffers from severe sodium dendrites and infinitely huge volume change, hampering its practical applications. Here, we demonstrate that sodium can be controllably deposited through main group II metals such as Be, Mg, and Ba since they have definite solubility in sodium and thus enable a marked reduction of the nucleation barriers of sodium, guiding the parallel growth of sodium on the metal substrates. By further homogeneously dispersing Mg clusters in a three-dimensional hierarchical structure on the basis of a carbonized Mg-based metal-organic framework-74 membrane, the nucleation barriers of sodium can be eliminated, owing to the plentiful Mg nucleation seeds. Hence, a dendrite-free sodium metal anode with a very low overpotential of 27 mV and a superior cycling stability of up to 1350 hours is achieved.