Scalable approach to multi-dimensional bulk Si anodes via metal-assisted chemical etchingElectronic supplementary information (ESI) available: SEM images of etched bulk Si particles prepared at various etching conditions, and their characterization. See DOI: 10.1039/c1ee02310a

Specific design and optimization of the configuration of micro-scale materials can effectively enhance battery performance, including volumetric density. Herein, we employed commercially available low-cost bulk silicon powder to produce multi-dimensional silicon composed of porous nanowires and micro-sized cores, which can be used as anode materials in lithium-ion batteries, by combining a metal deposition and metal-assisted chemical etching process. Nanoporous silicon nanowires of 5-8 μm in length and with a pore size of ∼10 nm are formed in the bulk silicon particle. The silicon electrodes having multi-dimensional structures accommodate large volume changes of silicon during lithium insertion and extraction. These materials show a high reversible charge capacity of ∼2400 mAh g −1 with an initial coulombic efficiency of 91% and stable cycle performance. The synthetic route described herein is simple, low-cost, and mass producible (high yield of 40-50% in tens of gram scale), and thus, provides an effective method for producing high-performance anode materials. We demonstrate a scalable approach for preparing multi-dimensional bulk Si anodes via a metal-assisted catalytic etching process.