EMF Studies of Lithium‐Rich Lithium‐Aluminum Alloys for High‐Energy Secondary Batteries

Abstract

Emf measurements were made across the lithium-rich half of the lithiumaluminum system at temperatures from 390 ~ to 550~ using a cell of the type Li/LiC1-KC1 (or LiF-LiC1-LiBr)/Li-A1. The lithium activity increases from 0.007 to approximately 0.7 over the composition range of 48-56 atomic percent (a/o) lithium (the E-phase region). A compound, Li3A12, rather than Li2A1, as reported in standard compilations, exists at temperatures up to the peritectic decomposition at 520r and forms a two-phase region of high lithium activity (>0.85) with the lithium-rich liquid phase. This compound has an estimated free energy of formation of --58 kJ/mole at 700~ The emf data indicate that the lithium-rich liquidus is about 2 a/o richer in lithium than the composition shown in standard compilations of binary phase diagrams.

Li-alloy/FeS cell design and analysis report

“…% into the B-LiAl phase, the potential decreases very rapidly and approaches that of lithium. 3 The theoretical capacity of Li-Al containing 47 at. % lithium, which has a density of 1.75 g/cm3, is approximately 0.74 Ah/g or 1.3 Ah/cm 3 when the material is discharged to 10 at.…”

“…The theoretical capacity of these multiplate cells (two positive and three negative plates) was about 200 Ah. The negative electrodes of LiAl + Al were pressed to a capacity loading density of about 1.3 Ah/cm 3 , based on the fully charged state (and no expansion).…”

“…Five phases have been identified in the positive electrode of Li-Al/FeS cells with LiCl-KC1 electrolyte. 3 2 - 3 8 These phases are "eS, LiK 6 Fe 2 4 S 26 C1 ("J-phase"), Li 2 FeS 2 ("X-phase"), Li 2 S, and Fe.…”

New battery materials. Progress report, April 1,--September 30, 1977. [Far high-temperature Li cells]

“…However, in any actual battery there will be an excess of lithium present, able to dissolve the aluminum or silicon produced by these reactions. In order to estimate the magnitude of this extra free energy of solution, calculations were performed based on available literature data for the activities of silicon [9] and aluminum [10], in molten lithium. Thus, under these conditions the silicate seems certain to dissolve in molten lithium at 700 K, and the aluminate case is finally balanced but attack by the lithium is a possibility.…”

“…Emf measurements by Yao et al [ 16 ] showed a constant voltage of 300 mV versus pure lithium for this two phase region; more recent measurements of Selman [ 10 ] was used for the measurements. Lithium was added to, or removed from, the beta lithium aluminum working electrode and the emf versus composition curve shown in Figure 2 was obtained.…”