Enhanced reversible lithium storage in germanium nano-island coated 3D hexagonal bottle-like Si nanorod arraysElectronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05181a

The rapid development of numerous microscale electronic devices, such as smart dust, micro or nano bio-sensors, medical implants and so on, has induced an urgent demand for integratable micro or nano battery supplies with high energy and power densities. In this work, 3D hexagonal bottle-like Si/Ge composite nanorod (NR) array electrodes with good uniformity and mechanical stability potentially used in micro or nano rechargeable Li-ion batteries (LIBs) were fabricated on Si substrates by a cost-effective, wafer scale and Si-compatible process. The optimized Ge nano-islands coated Si NR composite arrays as anode materials exhibit superior areal capacities and cycling performances by virtue of their favourable structural and improved conductivity features. The unique Si-based composite electrode in nanostructures can be technically and fundamentally employed to configurate all-solid-state Li-ion micro-batteries as on-chip power systems integrated into micro-electronic devices such as M/NEMS devices or autonomous wireless microsystems. Single crystalline Ge nano-islands embedded in wafer scale 3D hexagonal bottle-like Si NR arrays were fabricated by the NSL method combined with ICP dry etching and subsequent UHVCVD growth.