The scaling of electronic devices also requires the evolution of high energy density power sources. By using nanowires, high charge storage materials, which otherwise have mechanical breakage problems due to large structure transformations and volume changes, can be adopted as electrode materials. High power operation can also be possible due to the short lithium insertion distances in the nanowires. We have studied Si and Ge nanowires and demonstrated charge storage capacities several times higher than the graphite anodes used in existing battery technology. LiMn 2O 4 nanorod cathodes were found to show much higher power rates than commercial powders. Detailed morphology and structure characterization have shown that these improvements are attributed to facile strain relaxation, good electronic contact and conduction, and short Li insertion distances in the nanowire battery electrode. We also developed a Langmuir-Blodgett assembly technique to produce nanowire pillars as battery electrodes, which opens up the possibility for the fabrication of on-chip battery power sources.