3D amorphous silicon on nanopillar copper electrodes as anodes for high-rate lithium-ion batteries.

We present an amorphous Si anode deposited on a Cu nanopillar current collector, fabricated using a thermal roll-to-roll process followed by electroformation and LPCVD, for application in high-rate Li-ion batteries. Cu nanopillar current collectors with diameters of 250 and 500 nm were patterned periodically with 1 μm pitch and 2 μm height to optimize the diameters of the pillars for better electrochemical performance. Void spaces between Cu nanopillars allowed not only greater effective control of the strain caused by the Si expansion during lithiation than that allowed by a nonpatterned electrode but also significantly improved cycle performance even at 20 C measured after the same rate test: After 100 cycles at 0.5 C, the patterned electrodes with 250 and 500 nm diameter nanopillars showed high capacity retentions of 86% and 84%, respectively. These electrodes retained discharge capacities of 1057 and 780 mAh/g even at 20 C, respectively.