Three-dimensionally engineered porous silicon electrodes for Li ion batteries.

The ultimate goal of Li ion battery design should consist of fully accessible metallic current collectors, possibly of nanoscale dimensions, intimately in contact with high capacity stable electrode materials. Here we engineer three-dimensional porous nickel based current collector coated conformally with layers of silicon, which typically suffers from poor cycle life, to form high-capacity electrodes. These binder/conductive additive free silicon electrodes show excellent electrode adhesion resulting in superior cyclic stability and rate capability. The nickel current collector design also allows for an increase in silicon loading per unit area leading to high areal discharge capacities of up to 0.8 mAh/cm(2) without significant loss in rate capability. An excellent electrode utilization (∼85%) and improved cyclic stability for the metal/silicon system is attributed to reduced internal stresses/fracture upon electrode expansion during cycling and shorter ionic/electronic diffusion pathways that help in improving the rate capability of thicker silicon layers.