A shuttle mechanism for molten-electrolyte lithium batteries
The lithium-transport rates arising from a lithium shuttle mechanism (LSM) were examined by potentiometric control of a lithium-alloy electrode in a temperature range of 400 to 515{degrees}C in three electrolytes: LiCl-KCl, LiCl-LiBr-KBr, and LiF-LiCl-LiBr. Lithium transport in Li/FeS{sub x} cells by LSM was found to occur by diffusion of reduced lithium species across the separator layer, which was controlled by the Li-activity of the Li-alloy electrode. Solubility of lithium was strongly affected by electrolyte composition, especially K{sup +} content, which in turn regulated the lithium transport rate. As evidenced by LSM rates, the solubilized lithium would appear to form dimers (e.g. Li{sub 2}{sup +} or LiK{sup +}). The half-cell self-discharge rates, which were measured, correlate well with self-discharge rates in developmental cells ranging from 0.1 to 10 mA/cm{sup 2}. Innovative application of the LSM has led to the development of overcharge tolerant Li/FeS{sub x} cells. A bimodal self-discharge characteristic (a 20-fold increase toward the end of charge) results from a 150-250 mV step increase in lithium activity of a two-phase Li-alloy electrode (Li-Al plus Li-Al{sub 5}Fe{sub 2}). Three versions of the battery cell (100 cm{sup 2} separator area) have been demonstrated: LiAl+Li{sub 5}Al{sub 5}Fe{sub 2}(10% of capacity)/LiCl-LiBr-KBr(MgO)/FeS{sub 2}, as well as a FeS-type, (both operated at 400{degrees}C) and LiAl+Li{sub 5}Al{sub 5}Fe{sub 2}(10% of capacity)/LiF-LiCl-LiBr(MgO)/FeS (operated at 475{degrees}C). These cells exhibit a unique combination of overcharge capacity and extended trickle-charge tolerance at 2-5 mA/cm{sup 2}. Additionally, Li/FeS{sub 2} cells having overcharge tolerance have operated with stable performance for greater than 500 cycles. The overcharge tolerance rates are sufficient for battery cells to exhibit built-in charge/equalization capability by way of full-battery trickle charging.
- Research Organization:
- Argonne National Lab., IL (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 10105073
- Report Number(s):
- ANL/CMT/CP--79729; CONF-931024--5; ON: DE94002914
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
250900
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400
BATTERIES
ELECTRIC BATTERIES
ELECTRICAL PROPERTIES
ELECTROCHEMISTRY
ELECTROLYTIC CELLS
EXPERIMENTAL DATA
IRON SULFIDES
LITHIUM BROMIDES
LITHIUM CHLORIDES
LITHIUM HALIDES
MOLTEN SALTS
POTASSIUM BROMIDES
POTENTIOMETRY
SOLUBILITY
TEMPERATURE RANGE 0400-1000 K
TOLERANCE