Copper-Nanoparticle-Induced Porous Si/Cu Composite Films as an Anode for Lithium Ion Batteries.

"Welcome-mat"-like porous Si/Cu composite amorphous films are fabricated by applying the predeposited Cu-nanoparticle-assembled film as the growth direction template for the subsequent deposition of a Si active layer with the cluster beam deposition technique. When used as the binder-free anodes for lithium ion batteries, the acquired single-layer porous Si/Cu composite film exhibits a large reversible capacity of 3124 mA h g-1 after 1000 cycles at 1 A g-1. Even when cycled at 20 A g-1 for 450 cycles, the porous Si/Cu composite film still delivers a decent reversible capacity of 2086 mA h g-1. Also, multilayer porous Si/Cu composite films are synthesized through layer-by-layer sputtering and exhibit outstanding cyclability and relatively high specific capacity and initial Coulombic efficiency irrespective of increasing the layer number from two to four layers. The reasons for the excellent electrochemical properties of single-layer and multilayer porous Si/Cu composite films are discussed in detail.