Gold-coated porous silicon films as anodes for lithium ion batteries

Silicon has the highest known theoretical charge capacity for lithium, making it a promising material for rechargeable lithium ion batteries (LIB). A significant drawback of silicon anodes is the large volume change associated with the insertion and extraction of lithium, which oftentimes leads to cracking and pulverization of the anode, limiting its cycle life. We present a layered architecture consisting of a gold-coated porous silicon film attached to a bulk silicon substrate. This structure demonstrates an enhanced ability to alloy with lithium ions over several charge/discharge cycles while maintaining mechanical integrity. With this structure we show that a specific capacity of over 3000 mAh g(-1) can be achieved for over 50 charge-discharge cycles at 100 mu A cm(-2), and 2500 mAh g(-1) can be achieved for over 75 cycles with coulombic efficiencies over 95%. This is a significant improvement over a gold-coated, non-porous silicon sample, which had a maximum capacity of 1 mAh g(-1) before failing after 10 cycles at 0.25 mAh g(-1) when cycled at a constant current of 100 mu A cm(-2), illustrating the benefit of internal pores. Gold-coated porous silicon out-performed non-gold-coated porous silicon, which had a first cycle discharge capacities of 500 mAh g(-1), which quickly faded to 76 mAh g(-1) after the 10th cycle when cycled at a constant current of 50 mu A cm(-2). The combination of internal pores and a gold-coating points to a new approach to improving the long-term cycleability and high-capacity performance metrics of LIB anodes. (C) 2012 Elsevier B.V. All rights reserved.