Three-Dimensional Si-Based Composite Nanorods Array Applied in Energy Storage System

Abstract

The rapid development of the integrated circuit (IC) and Micro/Nano-Electro Mechanical System (M/NEMS) technologies are promoting the continued emergence or commercialization of the miniaturized autonomous devices such as wireless sensor networks (WSN) in smart grid.[1-4] In order to operate independently, the micro/nano autonomous electronic devices must have on-board power supply. However, the battery miniaturization still can not keep pace with the size scaling-down of the CMOS electronic technologies, due to the poor electrochemical performance of the micro/nano batteries or the un-compatible battery fabrication process with the IC technologies. Currently, the transition from two dimensional (2D) to 3D rechargeable LIBs with better electrochemical properties in a small areal footprint was found to cope well with state-of-the-art semiconductor technologies conceptually providing new opportunities for micro/nano power systems in the future. [5-7] In this work, the electrochemical performances of 3D hexagonal match-like Si/Ge nanorod (NR) arrays buffered by TiN/Ti interlayer, which were fabricated by a cost-effective, wafer scale and Si-compatible process, were demonstrated and systematically investigated as the anode in rechargeable batteries. The optimized Si/TiN/Ti/Ge composite NR array anode displays superior areal/specific capacities and cycling stability by reason of their favourable 3D nanostructures and the effective conductive layers of TiN/Ti thin films. Lithium/Sodium ion insertion behaviors were experimentally investigated in post-morphologies and elemental information of the cycled composite anode, and theoretically studied by the first principles calculation upon the adsorption and diffusion energies of sodium in Ge unit cell. The preferential diffusion of Lithium/sodium in Ge structure over in Si lattice was evidently proved.