Study of the reaction of lithium with isostructural A(2)B and various AlxBalloys

The electrochemical alloying reaction of Li with isostructural A(2)B acid A l-based alloys has been investigated. The binary A(2)B alloys we selected ( Sb2Ti, Sb2V, Sn2Co, Sn2Mn, Sn2Fe, Al2Cu, and Ge2Fe) are isostructural (Al2C u type) and comprise an active element (A) that alloys with lithium, and an inactive one (B) that does not. These compounds were prepared by mechanica l alloying and have small grain size (10-20 nm). With the exception of Al2C u, we observed a full reaction of A with lithium (A(2)B + 2xLi --> B + 2Li( x)A, where the theoretical values of x are 1 for Al, 3 for Sb, and 4.4 fur Si, Ge, and Sn). Extremely slow electrochemical cycling at 55 degrees C and potentiostatic tests at lithium potential proved the total inactivity of t he Al2Cu vs. lithium. However, thermodynamic considerations predict that th e reaction of A12Cu with Li should occur and that the formation of LiAl sho uld be observed. Other Ri-transition metal intermetallics were studied and were also found to be inert toward Li, suggesting that the,Al-transition me tal bond has unique features. (C) 2000 The Electrochemical Society. S0013-4 651(99)10-070-3. All rights reserved.