Facet selectivity of Cu current collector for Li electrodeposition

Abstract

Fabricating a uniform thin-film Li metal anode on a heterogeneous Cu substrate is a critical step toward high energy density lithium metal batteries. Here, we explore a facet selective lithium (Li) nucleation and growth phenomenon on copper (Cu) substrate and demonstrate that controlling the facet structure can improve the uniformity in electro-deposition of Li and the electrochemical performances of the resulting thin Li electrode. Preferential Li deposition on the Cu(100) plane is demonstrated by electrochemical analysis of the Cu single crystal surfaces and by electron-backscatter diffraction analysis of the Li-deposited Cu surfaces. DFT calculations show that a difference in the Li adsorption energy among the Cu facets during the initial Li deposition process is responsible for the facet selectivity. A majorly (100) plane-orientated Cu foil fabricated by a simple annealing method exhibits more uniform Li nucleation and leads to a 10-fold higher nuclei density and a two-fold enhancement in the Li cycling stability compared with a conventional Cu foil with randomly oriented surface facets. The control of the surface facet provides a new design principle for the thin-film Li metal anode used in lithium metal batteries.