Comparison of Carbon and Metal Oxide Anode Materials for Rechargeable Li-Ion Cells
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Wh/kg and operate at temperatures < -20 °C, whereas, the cycle life requirement is < 500 cycles (50-70% DOD). Penetraters require batteries that can operate at temperatures lower than -60 °C and withstand high shock levels. The lithium-ion system was selected for near term missions as this technology was more mature compared to the lithium metal based and lithium polymer battery systems . The specific objectives of the JPL lithium ion cell effort are : 1) lImprove the low temperature performance of lithium-ion cells and demonstrate their applicability to lander, rover and penetrater missions, 2) Improve the cycle life performance of lithium-ion cells and demonstrate the ability to meet life requirements of the Mars orbiters and 3) Establish effective charge methodology and reconditioning methods for on-board battery management. To realize these objectives work is in progress in areas such as chemistry and material development, design optimization and data base development. The prime objective of the chemistry and materials subtask is to develop/select electrode materials and electrolytes that are capable of providing long cycle life and improved low temperature performance. The SOA Ni-Cd and Ni-H 2 batteries are quite heavy and bulky and can not meet mass and volume requirements of future Mars missions. Furthermore, they have very poor low temperature performance capability as they use aqueous electrolytes. Rechargeable lithium-ion batteries offer significant weight, volume and cost advantages compared to SOA Ni-Cd and NiII batteries and are especially attractive for future Mars Missions. The performance advantages include: higher specific energy (2 to 3 times greater than Ni-Cd and Ni-H 2 ), energy density (3-4 times greater than Ni-Cd and Ni-H 2 ), higher cell voltage, coulombic and energy efficiency, low self-discharge rate, and lower battery costs compared to the SOA Ni-Cd and Ni-H 2 batteries. These advantages translate into several benefits for Mars Missions including: reduced weight and 519 Mat. Re$. Soc. Syrup. Proc. Vol. 496 © 1998 Materials Research Society
volume of the energy storage subsystem, improved reliability, extended mission life, and lower power system life cycle costs. Four types of lithium cells are presently under development in the US, Europe and Japan: 1) lithium metal with liquid electrolyte, 2) lithium metal with polymer electrolyte 3) lithium-ion containing liquid electrolyte, and 4) lithium-ion containing polymer electrolyte. Among these four types of technologies, lithium-ion battery technology is the most advanced and likely candidate for future space missions (1998 and beyond). This system is also being considered by other aerospace organizations for GEO and LEO spacecraft applications. These cells employ a carbon/graphite anode (instead of metallic lithium) and liquid organic electrolytes. LiCoO 2, LiNiO2 , and LiMn2O4 are presently being evaluated by several commercial vendors as candidate cathode materials for these cells. Small capacity cylindrical cells have been introduced i
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