The volume expansion behavior and volumetric energy densities of metal alloy negative electrodes (A(x)M) for metal-ion batteries based on A = Li, Na, K, Mg, Ca and Al are compared. It was found that each metal ion, A, occupies a characteristic volume in alloys which is almost insensitive to the host metal, M. All alloy systems, with the exception of K(x)M alloys, were found to have similar or greater volumetric energy density than conventional graphitic anodes in Li-ion cells. It is predicted that both the Mg(x)M and Al(x)M systems might achieve higher energy densities than possible with any Li-ion negative electrode known and operate at potentials at which organic electrolytes are known to be stable. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.083112jes] All rights reserved.