In situ monitoring nanoscale solid-state phase transformation of Ag nanowire during electrochemical reaction

Abstract

Nanoscale solid-state transformation of metals and alloys during electrochemical processes are critical for applications including corrosion, electrochemical machining and alkali metal batteries. However, these nanoscale phase and chemical transformations at metal surface and interface cannot be probed by conventional characterization techniques lacking of site-specific information with high spatial resolution. Here, we use in situ transmission electron microscopy to demonstrate a unique phase transformation upon electrochemical alloying of Ag nanowire with Li. It features a surface reaction of electrochemical lithiation of Ag followed by a fast redistribution of Ag into small nanoparticles embedded in Li2O. The Ag-Li alloying reaction proceeds through a surface reaction mode with a strong dependence of surface facets. The weak bonding between AgLi and the presence of residual O2 in TEM column causes the as-formed Ag-Li alloy instantly transform to a Li2O shell with well-dispersed Ag nanoparticles.