Uniform SnSe nanoparticles on 3D graphene host enabling a dual-nucleation-site interface for dendrite-free sodium metal batteries

The practical application of naturally abundant sodium (Na) metal anodes with high energy densities is hindered by large volume expansion and dendrite formation during battery operation. This work reports the synthesis of tin selenide nanoparticles uniformly grown on highly conductive, porous 3D graphene foam (SnSe@GF) as a stable host for Na metal anodes and the underlying conversion reactions as their energy storage mechanism. The SnSe@GF electrode prepared via hydrogel coating and phase transformation sustains remarkable reversibility after 1500 cycles in asymmetric cells and delivers extraordinary cyclic stability and low overpotentials for 2000 h at 1 mA cm-2 and 1 mAh cm-2 in symmetric cells. The conversion of crystalline SnSe into low-crystallinity Na15Sn4 and Na2Se dual nucleation sites after pre-sodiation is responsible for the outstanding performance according to the in-situ microscopy and density functional theory calculations. The conversion enables the in-situ formation of a unique interface that possesses high Na affinity featured by abundant active sites, contributing to uniform Na nucleation/plating and dendrite suppression, thus give rising to superior stability and electrochemical performance of the SnSe@GF electrode. The rational design of the current 3D architecture can shed new insights into the development of Na hosts for next-generation rechargeable batteries.