Bulk synthesis of crystalline and crystalline core/amorphous shell silicon nanowires and their application for energy storage.

Abstract

Silicon nanowires (NWs) have stimulated significant interest and found numerous applications; however, many applications will require a bulk quantity of nanowires to be synthesized in a reliable way. In this paper, we report the bulk synthesis of silicon nanowires on millimeter scale Al(2)O(3) spheres with a thermal chemical vapor deposition system (CVD) via the vapor-liquid-solid (VLS) growth mechanism. The spherical substrates enable the realization of Si nanowire synthesis on three-dimensional surfaces in comparison with the synthesis on a planar, two-dimensional wafer substrate. By modifying temperature in the recipe of synthesis, both single-crystalline and crystalline core/amorphous shell Si nanowires were obtained with this nanowire-on-spherical-support method. Conspicuous distinction in crystallinity of the nanowires was revealed by transmission electron microscopy characterization. The crystalline core/amorphous shell Si nanowires were utilized to form the anode of Li-ion battery half-cells with the traditional slurry method. Galvanostatic measurement demonstrated that the maximum power capacity achievable by the electrodes was 3500 mAh/g and capacity sustained at 1100 mAh/g after 60 cycles of charging and discharging.