Study of the reaction of lithium with isostructural A2B and various AlxB alloys

The electrochemical alloying reaction of Li with isostructural A(2)B acid Al-based alloys has been investigated. The binary A(2)B alloys we selected (Sb2Ti, Sb2V, Sn2Co, Sn2Mn, Sn2Fe, Al2Cu, and Ge2Fe) are isostructural (Al2Cu type) and comprise an active element (A) that alloys with lithium, and an inactive one (B) that does not. These compounds were prepared by mechanical alloying and have small grain size (10-20 nm). With the exception of Al2Cu, 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 the Al2Cu vs. lithium. However, thermodynamic considerations predict that the reaction of A12Cu with Li should occur and that the formation of LiAl should be observed. Other Ri-transition metal intermetallics were studied and were also found to be inert toward Li, suggesting that the,Al-transition metal bond has unique features. (C) 2000 The Electrochemical Society. S0013-4651(99)10-070-3. All rights reserved.