New battery materials. Progress report, April 1,--September 30, 1977. [Far high-temperature Li cells]
Lithium ion conductivities of solid solutions formed between Li. SiO. 4 4 and LipAlO, have been measured. The conductivity of Li. ,.A1 Si ^0. is comparable to the best previously known lithium ion conductors. The structural type is that of Li.SiO" and x-ray lattice parameters were determined across the range of solid solution . No solid solutions were found which had the Li c A10. (antiflourite structure). 4 Thermodynamic calculations based on available and estimated data suggest that lithium
... licate is unstable with respect to attack by molten lithium at 700 K, and that Li,-A10, may also be marginally unstable. Experimentally, the materials appear to have quite good stability at lower temperatures (300°C), but both Li^AlO, and Li, ,A1 ,Si fi 0, were attacked at 720K within a period of a few hours. The intermetallic systems Li-Sb and Li-Bi, and the oxide systems Li-Li 9 Ti_0 have been studied as possible positive electrode systems for lithium batteries. Large lithium chemical diffusion coefficients were found in all 3 systems. Associated kinetic data (particle diffusion coefficients, partial conductivities, etc.), were calculated and thermodynamic data (emf versus composition) were obtained. Beta LiAl was studied in considerable detail by coulometric titration and potentiostatic and galvaostatic transient techniques. Its range of existence was found to extend from 47 atom % to 55 atom % of lithium, between the voltages 300 to 70 mV with respect to pure lithium. Chemical diffusion coefficients in this phase are very large, lying between 2 x 10 2 -4 2 cm /sec at the lithium rich end and 10 cm /sec at the lithium deficit end of its range of existence.