Stress-induced Solute Segregation at the Edge of Nano-scale Thin-film Electrodes on Thick Substrates

High-capacity anodes such as Si are gaining critical importance for energy-storage purposes in a variety of industries. However, they are well known to suffer from capacity fading which is induced by loss of mechanical integrity during cycling. Among various nano-structured electrodes, nano-scale thin films deposited on thick substrates have been widely studied through experimental and theoretical methods. Experiments show that even nano-scale thin-film electrodes could undergo extensive fracture and delamination from the underneath current collector. In this paper, we examine the effect of interaction between chemical and mechanical driving forces on the solute distribution in the vicinity of the edge of an elastic semi-infinite nano-film which is bonded onto the surface of a thick elastic substrate. The film as opposed to the substrate is considered chemically active, and in chemical equilibrium with an external infinitely large mass reservoir which maintains a uniform chemical potential everywhere in the film. Mechanical deformation of the film is studied using the membrane approximation theory, and the thick substrate is modelled as an elastic half space. It is shown that solute distribution is highly non-uniform close to the film edge. The effect of solute segregation on the axial stress distribution in the film is also examined.