Advanced high power density rechargeable batteries are currently under development. These batteries have the potential of greatly increasing the power and energy densities available for space applications. Depending on whether the system is optimized for high power or high energy, values up to 150 Wh/kg and 2100 W/kg (including hardware) are projected. This is due to the fact that the system uses a high conductivity molten salt electrolyte. The electrolyte also serves as a separator layer with unlimited freeze thaw capabilities. Life of 1000 cycles and ten calendar years is projected. The electrochemistry consists of a lithium aluminum alloy negative electrode, iron disulfide positive electrode, and magnesium oxide powder immobilized molten salt electrolyte. Processed powders are cold compacted into circular discs which are assembled into bipolar cell hardware with peripheral ceramic salts. The culmination of the work will be a high energy battery of 40 kWh and a high power battery of 28 kWh

Briscoe, J. Douglass

Embrey, J.

Oweis, S.

Press, K.

English

NASA Technical Reports Server

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https://ntrs.nasa.gov/search.jsp?R=19920013520 2020-03-17T11:39:20+00:00Z
The LiAI/FeS2 Battery
Power Source for the Future
J.D. Briscoe, J. Embrey, S. Oweis, K. Press
SAFT R&D Center
Cockeysville, MD 21030
Abstract:
Advanced high power density rechargeable batteries are currently under
development at SAFT. These batteries have the potential of greatly increasing the
power and energy densities available for space applications. Depending on
whether the system is optimized for high power or high energy, values up to 150
Wh/kg and 2,100 W/kg (including hardware) are projec'ted. This is duc to the fact
that the system employsa high conductivity molten salt electrolyte. The electrolyte
also serves as a separator layer with unlimited freeze thaweapabilities. Life or
1,000 cycles and ten calendar years is projected. The electrochemistry consists of a
lithium aluminum alloy negative electrode, iron disulfide positive electrode, and
magnesium oxide powder immobilized molten salt electrolyte. Processed powders
are cold compacted into circular discs which are assembled into bipolar cell
hardware with peripheral eeramic seals. The culmination of SAFT'sdevelopment
work will be a high energy battery of 40 kwh and a high power battery or 28 kwh.
Introduction:
Advanced rechargeabl¢ high energy batteries are desirable for a number of
applications where the performance of present day lead acid batteries is
1991 NASA Aerospace Battery l¥orkst_op -486- Advanced Technologies Session
inadequate. Such applications as electric vehicle propulsion, utility load leveling,
military and space demand high power and energy from reliable power sources.
Rechargeable high temperature electrochemistries employing molten salt
electrolytes and high energy electrodes offer promise for fulfilling present and
future requirements in lower weight and volume packages.
Today, SAFT is developing LiAI/FeS 2 batteries in sealed bipolar configuration
having superior energy and power densities. Such batteries promise to give
improved performance with lower weight for future space applications.
Space Power Systems:
At the 1989 IECECconference, a paper was presented entitled: "Advanced
Electrochemical Concepts for NASA Applications "C1). Presented in that paper wcrc
the results of a Jet Propulsion Laboratory survey of 23 electrochemical systems for
space applications. The highest ranked advanced systems for operation in
planetary inner-orbit spacecraft included Na/beta"alumina/z (where z = S, FeCl 2,
or NiC12) , upper plateau (U.P.) Li(AI)/FeS 2 and H20 2 alkaline regenerative fucl
cell (RFC). The achievable specific energy for these as operational batteries was
estimated to be 130, 180, and 100 Wh/kg respectively. Energy storage requirements
of six anticipated space missions are tabulated as shown in Figure 1. GEO,
planetary rover, and lunar based applications were designated as shown to be good
candidates for LiAI/FeS 2 primarily because of moderate cycles and large energy
requirements.
As compared to present state-of-the-art nickel/cadmium and nickel/hydrogen
batteries, the projected specific energy (Wh/kg) for bipolar constructed lithium
1991 NASA Aerospace Battery Workshop -487- Advanced Technologies Session
aluminum/iron disulfide batteries is three times that of nickel hydrogen with five
times improvement in energy density (Wh/l) as shown in Figure 2.
Lithium/Metal Sulfide System Description:
During the 1970s, work was performed at Argonne National Laboratory (ANL) to
develop batteries for electric vehicle propulsion and utility load leveling ¢2_. Both
lithium aluminum/iron disulfide and iron sulfide couples were investigated. The
complete discharge (two plateaus) of lithium aluminum/iron disulfide can be
written as
4LiAI + FeS 2 _ 2Li2S + Fe + 4AI
Failure to achieve good cycle life with this couple caused development emphasis to
shift heavily in favor of the lower energy and less corrosive lithium
aluminum/iron sulfide system. The discharge has a theoretical specific energy of
460 Wh/kg and can be written as
2LiAI + FeS _ Li2S + Fe + 2AI (1.34V)
Full scale prismatic multiplate cells and small batteries were built at Eagle Pitcher,
Gould, and ANL.
In the 1980s, some work was continued at ANL on LiAI/FeS 2 by Kaun and others.
Success was achieved in 1986 by cycling only the upper plateau
2LiAI + FeS 2 _ Li2S + FeS + 2A! (1.66V)
with a theoretical specific energy of 490 Wh/kg. Over 1,000 cycles was
demonstrated in LiAI/FeS 2 prismatic bicell configuration ¢3_. Further developments
in 1988 of an electrochemical overcharge tolerance ¢4_ and in 1990 of a peripheral
seal material ¢5_ make bipolar stack construction both workable and practical.
1991 NASA Aerospace Battery Workshop -488- Advanced Technologies Session
At SAFT, primary reserve thermal batteries containing bipolar LiAI/FeS 2 have
been manufactured since 1978, and research and development on rechargeablc
prismatic LiAI/FeS and bipolar LiAI/FeS 2 has been conducted since 1990.
The LiAI/FeS 2 electrochemistry consists of components fabricated from cold
uniaxial pressed dry mixed powders. Three cell components are the negative
electrode, electrolyte/separator, and positive electrode, all containing molten salt
electrolyte. The negative electrode contains LiAI alloy and the positive electrode
FeS 2. The electrolyte/separator consists of molten salt immobilized by MgO
ceramic powder which acts as a binder-separator at operating temperature.
Cell components are fabricated in prismatic or disc geometries for either prismatic
multiplate cells (Figure 3) or cylindrical bipolar configurations (Figure 4). The
bipolar battery is a triple seal construction.
around the periphery as shown in Figure 4.
sealed inside a steel case to form a module.
First, all cells are individually sealed
Second, arrays of series cells are
And finally, the modules are
contained insidea sealed thermally insulated enclosure (Figure 5). Integral cooling
and heating systems maintain the modules ata constant temperature. The thermal
enclosure is double walled construction with vacuum and multifoil insulation.
Heaters are powered by the charging source during charge and the battery during
discharge. Heat loss is limited to approximately 16% of battery capacity per day.
System Advantaees:
As compared to other advanced battery chemistries, the LiAI/FeS 2 system offers
some distinct advantages. In addition to high volumetric power and energy
1991 NASA Aerospace Battery Workshop -489- Advanced Technologies Session
densities, the systcmoffers high reliability with intrinsic safety. Ceils have
performed for over 1,000 cycles with negligable performance degradation.
Single cell and battery tests have demonstrated that cells always fail short circuit.
Configured as series arrays of bipolar cells, remaining series cells will continuc to
operate normally even with shorted cells included in the string. This is in contrast
to the sodium/sulfur system where cells fail open circuit and the remaining scrics
cells are inoperable.
The battery is intrinsically safe because it contains no liquids or gases. Unlike
most lithium batteries, the negative electrode is not pure lithium but an alloy
containing approximately 20 weight percent lithium which is less reactive and solid
at the battery operating temperature. During operation the salt is molten in the
electrodes and "wets" the active particles. If the container is punctured exposing
the chemistry to the atmosphere, the salt freezes forming a protective coating over
the lithium aluminum particles.
The electrochemistry in bipolar configuration is tolerant to dynamic environments
as has been demonstrated for over 14 years in thermal batteries. These are primary
reserve LiAI/FeS 2 batteries designed for military application. Installed in missiles,
guided bombs, and projectiles, these batteries withstand severe environments of
shock, vibration, and acceleration in both non-operating and operating conditions.
The dense paste-like electrolyte/separator is not subject to cracking typical of solid
ceramic separators. For secondary applications, this separator property provides
unlimited freeze thaw capability.
1991 NASA Aerospace Battery Workshop -490- Advanced Technologies Session
An advantage over ambient temperature batteries is that the electrochemistry is
always operating at optimum temperature independent of environmental changes.
Development Goals:
Currently, SAFT is working on development of two batteries utilizing LiA1/FcS 2
electrochemistry in bipolar construction. One battery will be optimized for high
energy utilizing thick electrodes at moderate current densities to achieve 150
Wh/kg with power of 340 W/kg. This battery is being developed for electric
vehicle propulsion. The second battery will be optimized for high power utilizing
thin electrodes at high current densities up to 5.0 amperes/cm 2 to achieve
extremely high specific power of 2.9 kW/kg at a relatively low specific energy of
39 Wh/kg. This battery will provide high power fc.r an electric weapon
application. A comparison of development goals for these batteries is shown in
Figure 6.
Development Status:
At SAFT, bipolar primary thermal batteries have been made since the 1950s. In
1978, SAFT introduced the LiAI/FeS 2 technology developed by ANL into thermal
batteries. Since 1990, work on rechargeable lithium metal sulfide technology has
been conducted at SAF'I"s Baltimore facility. This work included LiAI/FeS
prismatic multiplate cells (200 Ah), LiAI/FeS 2 prismatic bicells (40 Ah), and
LiAI/FeS 2 bipolar cells (0.3 to 3.2 Ah).
A number of recent accomplishments are noteworthy. Specific energy of 89 Wh/kg
was achieved for LiAI/FeS prismatic multiplate cells tested at the C/3 rate.
1991 NASA Aerospace Battery Workshop -491- Advanced Technologies Session
Battery hardware was developed to accommodate 27 multiplate cells. Bipolar
LiAI/FeS 2 cells and batteries have achieved 2,100 W/kg, and 6,700 W/l, at very
high rates of charge (3C) and discharge (75C).
Development Issues:
A target of 1993 has been set to develop a 7 kW high power bipolar LiAI/FeS 2
scaleable module for test. A 5 kWh high energy module is targeted for
development by 1994.
In order to achieve these development goals, work must progress towards
improvement and scale up of peripheral seals, chemical equalization, and corrosion
resistant materials at the cell and cell stack level. Engineering of stack
pressure/restraint and current collection systems and methods for electrical
isolation need development.
At the battery level, development of an optimized thermal management system that
is reliable and producible at minimum cost is essential. The high battery volumes
required for electric vehicles require development of a recycling program.
1991 NASA Aerospace Battery Workshop -492- Advanced Technologies Session
References:
1° G. Hatpert and A. Atria, "Advanced Etectrochemicat Concepts for NASA Apptications," 24th
IECEC Meeting, _/ashington, DC, August fi o 11, 1989, rot 3, pp 1429 - 1434.
2° P.A. Netson, et at, :High Performance Batteries For Off-Peak Energy Storage and Etectric
Vehic|e Proputsion," Argonne Nationat Laboratory Report ANL-75-1.
3. T.D. Kaun, et at, ,Lithium/Disutfide Cetts Capable of Long Cycte Life," Proc. of the Symp,
on Materia( and Processes for Lithium Batteries, ed., K.M. Abraham, Etectrochem. Soc.
Meeting, Vo[ 89-4, p. 373 (1989).
4. T.D. gaun, T.F. Hotifietd, M. Nigohosian, and P.A. Nelson, "Development of Overcharge
Toterance in Li/FeS and Li/FeS2 CeLLs," Proc. of the Symp. on Materiat and Processes for
Lithium Batteries, ed., K.M. Abraham, Etectrochem. Soc. Meeting, Vot 89-4, p. 383 (1989).
5. T.D. Kaun, N.J. Duoba, K.R. Gillie, and J.A. Smaga, "Seating Li-A[toy/FeS2 Celts for a
Bipotar Battery," Proc. of the Symp. on Rechargeabte Lithium Batteries, ed., S. Subbaro,
Etectrochem. Soc. Meeting, Vot 90-5, p. 315 (1990).
1991 NASA Aerospace Battery Workshop -493- Advanced Technologies Session
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The LiAl/FeS2 battery power source for the future

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