Micromachined Substrates with Thin-Film Base to Improve Power Density in Alkali Metal Systems

Our innovation is a composite component, consisting of a micromachined metal substrate overlaid with solid electrolyte, that will greatly increase the power density of AMTEC and sodium sulfur battery systems. The approach is to uniquely fabricate a porous substrate in part by micromachining with a laser and then to sputter-deposit a microscopically thin (10 micron) layer of b"-alumina solid electrolyte (BASE). A substrate structure which permits very thin (@ 10 micron) BASE is the key to development of the composite and will improve the power density (W/cm2) of the electrodes by 50%. It will enable the power conversion cells to be constructed with the electrodes as flat plates, resulting in a power-per-unit-volume four times greater (@ 2 kW/liter) for an AMTEC system module at a high conversion efficiency (3 35%). In Phase I, we will demonstrate the feasibility of fabricating our micromachined porous substrates and sputter-depositing micro-layers of BASE. In Phase II, we will complete the development of the micromachining and deposition processes, and we will demonstrate the improved power density in operating AMTEC modules.| Benefits: The benefits of the proposed composite substrate/thin-BASE configuration are 50% greater electrode power density in AMTEC cells or sodium-sulfur batteries. It enables a flat-plate electrode configuration which will improve the energy-per-unit volume (specific volume) by a factor of four in AMTEC systems for satellites and hybrid electric vehicles. The flat-plat electrode configuration will also reduce the size of sodium-sulfur batteries used in submarines and may be enabling technology for these batteries to meet the power density requirements for hybrid electric vehicles.|