A High Temperature (400 to 650oC) Secondary Storage Battery Based on Liquid Sodium and Potassium Anodes
This STTR Phase I research program was on the development of high temperature (400 to 650 C), secondary batteries with roundtrip efficiency > 90% for integration with a 3 to 10 kW solid oxide fuel cell (SOFC) system. In fulfillment of this objective, advanced planar high temperature rechargeable batteries, comprised of an alkali metal ion conducting, highly refractory, beta'' alumina solid electrolyte (BASE) sandwiched between liquid sodium (or potassium) anode and liquid metal salt cathode, were developed at MSRI. The batteries have been successfully demonstrated at a working temperature as high as 600 C. To our knowledge, so far no work has been reported in the literature on planar rechargeable batteries based on BASE, and results obtained in Phase I for the very first time demonstrated the viability of planar batteries, though relatively low temperature tubular-based sodium-sulfur batteries and ZEBRA batteries have been actively developed by very limited non U.S. companies. The results of this Phase I work have fulfilled all the goals and stated objectives, and the achievements showed much promise for further, substantial improvements in battery design and performance. The important results of Phase I are briefly described in what follows: (1) Both Na-BASE and K-BASE discs and tubes have been successfully fabricated using MSRI's patented vapor phase process. Ionic conductivity measurements showed that Na-BASE had higher ionic conductivity than K-BASE, consistence with the literature. At 500 C, Na-BASE conductivity is 0.36 S/cm, which is more than 20 times higher than 8YSZ electrolyte used for SOFC at 800 C. The activation energy is 22.58 kJ/mol. (2) CuCl{sub 2}, FeCl{sub 2}, ZnCl{sub 2}, and AgCl were identified as suitable salts for Na/metal salt or K/metal salt electrochemical couples based on thermochemical data. Further open circuit voltage measurements matched those deduced from the thermochemical data. (3) Tubular cells with CuCl{sub 2} as the cathode and Na as the anode were constructed. However, it was discovered that CuCl{sub 2} was somewhat corrosive and dissolved iron, an element of the cathode compartment. Since protective coating technology was beyond this Phase I work scope, no further work on the CuCl{sub 2} cathode was pursued in Phase I. Notwithstanding, due to its very high OCV and high specific energy, CuCl{sub 2} cathode is a very attractive possibility for a battery capable of delivering higher specific energy with higher voltage. Further investigation of the Na-CuCl{sub 2} battery can be done by using suitable metal coating technologies developed at MSRI for high temperature applications. (4) In Phase I, FeCl{sub 2} and ZnCl{sub 2} were finalized as the potential cathodes for Na-metal salt batteries for delivering high specific energies. Planar Na-FeCl{sub 2} and Na-ZnCl{sub 2} cells were designed, constructed, and tested between 350 and 600 C. Investigation of charge/discharge characteristics showed they were the most promising batteries. Charge/discharge cycles were performed as many as 27 times, and charge/discharge current was as high as 500 mA. No failure was detected after 50 hours testing. (5) Three-cell planar stacks were designed, constructed, and evaluated. Preliminary tests showed further investigation was needed for optimization. (6) Freeze-thaw survival was remarkably good for planar BASE discs fabricated by MSRI's patented vapor phase process.
- Research Organization:
- Materials and Systems Research, Inc.
- Sponsoring Organization:
- DOE SBIR/STTR
- DOE Contract Number:
- FG02-06ER86280
- OSTI ID:
- 908547
- Report Number(s):
- DOE/ER/86280- Final Report; TRN: US201211%%59
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
30 DIRECT ENERGY CONVERSION
ACTIVATION ENERGY
ALKALI METALS
ANODES
CATHODES
COATINGS
ELECTRIC BATTERIES
ELECTRIC POTENTIAL
ELECTROLYTES
IONIC CONDUCTIVITY
LIQUID METALS
OPTIMIZATION
POTASSIUM
PROTECTIVE COATINGS
RESEARCH PROGRAMS
SODIUM
SODIUM-SULFUR BATTERIES
SOLID ELECTROLYTES
SOLID OXIDE FUEL CELLS
STORAGE
Storage battery
beta" alumina solid electrolyte
solid oxide fuel cell
potassium
sodium
metal salt cathodes