| AVS 58th Annual International Symposium and Exhibition | |
| Energy Frontiers Focus Topic | Thursday Sessions |
| Session EN+NS-ThM |
| Session: | Nanostructures for Energy Storage and Fuel Cells I |
| Presenter: | Florencia Rusli, Georgia Institute of Technology |
| Authors: | F. Rusli, Georgia Institute of Technology V. Chakrapani, Georgia Institute of Technology M.A. Filler, Georgia Institute of Technology P.A. Kohl, Georgia Institute of Technology |
| Correspondent: | Click to Email |
Silicon nanowires have recently garnered significant attention as a potential candidate to replace graphite as the negative electrode in a lithium-ion battery. Silicon’s earth abundance, extensive knowledge base, and its theoretical capacity of 4200 mAh/g make it an attractive material for this purpose. While the high incorporation of lithium presents a problem as silicon undergoes a significant specific volume expansion upon intercalation (up to 400%), nanowires permit facile radial strain relaxation and allow lithiation without pulverization. In this work, we report on the first systematic study of nanowire length and doping on the cycling performance of NW electrodes. Silicon nanowires were grown on stainless steel substrates via the vapor-liquid-solid technique in a cold-wall low pressure chemical vapor deposition reactor. Growth times ranging from 5-60 minutes and doping concentrations between 1018 – 1020 atoms cm-3 were studied. The half cells were cycled against lithium metal between (1) 0.01 and 2.0 V and (2) 0.07-0.7 V at a C/20 rate for 20 cycles. Cycling performance at different depths of discharge was also studied. Nanowires grown at short and long times both exhibit lower capacities than those grown at intermediate times. We attribute this effect to the loss of nanowire contact at the interface between the stainless steel and nanowire array for long nanowires, while the percolation network formed by short nanowires is not sufficiently robust to prevent loss of electrical connectivity upon wire breakage further from this interface. Nanowires at higher doping concentrations were not found to improve cycling performance drastically, which we attribute to the dopant effects on the growth mechanism of the nanowires and placement of dopant atoms in the silicon matrix that may have inhibited lithium atom insertion. We will present novel electrode fabrication routes that overcome these two challenges.