Porous lithiophilic Cu-Sn solid solution current collector for dendrite-free lithium metal batteries

Lithium metal batteries (LMBs) have high energy density but suffer from the formation of Li dendrites and unstable solid electrolyte interface. Herein, a three-dimensional porous Cu-Sn solid solution was designed as current collector for LMBs and was fabricated through the combination of vapor phase alloying with subsequent vapor phase dealloying. The effect of the Sn addition on electrochemical performances and Li plating/stripping behaviors was investigated using in-situ X-ray diffraction, ex-situ scanning electron microscopy, as well as density functional theory calculations. As benchmarked with porous Cu (3D-Cu), the addition of lithiophilic Sn can efficiently improve the Li plating/stripping performance, especially for the 1.5 at.% Sn addition (3D-Cu98.5Sn1.5). The 3D-Cu98.5Sn1.5 current collector maintains coulombic efficiency of 95 % up to 200 cycles at 1 mA cm−2. Moreover, the existence of Sn in solid solution exhibits a much lower binding energy (-3.223 eV) and nucleation overpotential (28.9 mV) compared with those of 3D-Cu, indicating that the metallic Li is extremely susceptible to nucleation and growth on the surface. Additionally, the gas evolution scenarios were probed by on-line differential electrochemical mass spectrometry. Our findings show that the 3D-Cu98.5Sn1.5 current collector effectively enhances the uniformity of Li plating and suppresses the generation of dendrites in LMBs.