Silicon Whisker and Carbon Nanofiber Composite Anode
Physical Sciences Inc. (PSI) of Andover, Massachusetts, has been awarded a research contract from NASA Glenn Shared Services Center to develop silicon whisker and carbon nanofiber composite anode.
PSI has successfully developed a silicon whisker and carbon nanofiber composite anode for lithium ion batteries and has demonstrated a technology readiness level of 3 with an anode composite capacity of greater than 1100 mAh/g for over 200 cycles (100% depth-of-discharge) at 1C using 2 mAh cells. This anode provides high capacity, high power, and improved cycle life at a competitive cost. Silicon is low cost and has a theoretical capacity of 4200 mAh/g but it has a limited cycle life. The nanocomposite design provides a synergistic improvement in reversible capacity and electrochemical cycling as a result of the unique silicon architecture and structural reinforcement provided by the nanofibers. In the Phase II program, PSI will increase cell size to 2.5 mAh and optimize cell design to further improve cycle life. PSI will deliver to NASA 2.5 Ah lithium ion cells with an energy density greater than 220 Wh/kg that is required by NASA’s future robotic and human exploration missions. In collaboration with a battery manufacturer, PSI will also demonstrate that this anode technology is scaleable to reach industrial production level.
Energy storage with improved weight and volume performance are required for various NASA applications which are both orbital and planetary surface. Flight elements of the Exploration Vision initially include the Orion and ARES crew and launch vehicles, respectively. For lunar capability, additional elements include the Lunar Lander or Lunar Surface Access Module (LSAM), robotic missions, and surface systems. Surface systems include human habitats, Extravehicular Activities (EVA), science measurements, and the utilization of in situ resources. This lithium-ion battery system has the capability to provide an energy density of greater than 220 Wh/kg with a 1-year calendar year service life. The battery system contains no toxic materials and lends itself to being human rated for Exploration missions. These mission applications include portable power for landers, rovers, and astronaut equipment; storage systems for crew exploration vehicles and spacecraft; and stationary energy storage applications such as base power or peaking power applications.
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