Combinatorial Study of Tin-Transition Metal Alloys as Negative Electrodes for Lithium-Ion Batteries

A survey of the structural and electrochemical properties of combinatorially sputter deposited Sn-transition metal alloys [Sn 1-x M x (0 0.48 to at least x = 0.65 for M = Ti, x > 0.39 to at least x = 0.60 for M = V, 0.47 < x < 0.73 for M = Cr, and 0.28 < x < 0.43 for M = Co. Electrochemical tests using a 64 channel Li/Sn 1-x M x combinatorial electrochemical cell show that the specific capacity of the alloys drops with transition metal content, as expected. The Sn 1-x Co x system shows an amorphous phase with the largest specific capacity, primarily because the amorphous phase is reached at the lowest transition metal content for Sn 1-x Co x . Capacity retention vs cycle number is generally best for those compositions that are amorphous or highly nanostructured. Arguments are presented to suggest that amorphous Sn 1-x V x alloys are the best choice among Sn 1-x M x alloys. Comparison with literature results for samples prepared by mechanical alloying, electrodeposition, vacuum deposition, etc. is made.