Magnesium-substituted birnessite and zinc chalcophanite have been synthesized througha novel procedure based on a combination of coprecipitation and metal ion intercalationtechniques. The materials showed very promising performance as hosts for lithiumintercalation. Upon galvanostatic discharge, Mg-birnessite and Zn-chalcophanite compositecathodes were able to intercalate >2 equiv of lithium per mole.