Lithium–magnesium solid solution alloys with compositions between Li0.6Mg0.4 and Li0.8Mg0.2 were prepared by melting the component metals in argon. Experiments carried out in a transparent cell confirmed the suppression of dendrite formation on the alloy surface. Diffusion kinetics within the bulk alloy limit the practical current density, particularly during discharging. Heating mixtures of lithium nitride and magnesium provides a convenient method of preparing ceramic–metal composites (“cermets”) containing the solid solution alloy and inert magnesium nitride. The cermets can be formed into a desired shape before or after reaction and may offer a route to higher surface area metallic anodes with improved rate capability.