Efforts to harvest human-induced energies into electricity has garnered a significant amount of research attention, with potential applications in powering wireless sensors or Internet of Things (IoT) devices. Successful integration of energy harvesters into small-scale sensor systems may operate sensors without battery exchange for years or in remote environments where battery charging is not applicable. Energy harvesters may also provide additional efficiency to the overall electric grid, since the amount of generated electricity scales directly with human activities; providing electricity at the peak time and location where electricity is needed the most alleviates the burden from the electric grid.To realize successful energy harvesters, researchers have developed energy harvesters from different sources such as thermal, vibrational, acoustic or contact electrification-based energies. Many of these types, however, face severe challenges to commercialization due to the limited efficiencies linked to their fundamental working mechanisms. For instance, piezoelectric and triboelectric generators suffer from the mismatch between their natural output frequencies and human motion timescales. The generated electricity from these two types often has current peak widths below 100 msec, making them limited in the human activities timescales of 0.55 Hz[1,2].In this talk, we develop and demonstrate an electrochemically driven mechanical energy harvesters based on stress-composition coupling in Li binary alloys[3]. We first demonstrate the presence of stress-composition coupling among Li-alloys, by using in situ graphene liquid cell electron microscopy.[3] With the unveiled stress-composition coupling, we demonstrate two distinct device concepts utilizing this stress-composition coupling, with Li x Si thin films and yolk-shell nanoparticles[4].[1] Chun J., Ye B. U., Lee J. W., Choi D., Kang C.-Y., Kim S.-W., Wang Z. L., Baik J. M., “Boosted output performance of triboelectric nanogenerator via electric double layer effect” Nature Communications 7, 12985 2016.[2] Hwang G.-T., Park H., Lee J.-H., Oh S., Park K.-I., Byun M., Park H., Ahn G., Jeong C. K., No K., Kwon H., Lee S.-G., Joung B., Lee K. J., “Self-powered cardiac pacemaker enabled by flexible single crystalline PMN-PT piezoelectric energy harvester” Advanced Materials 26, 4880 2014.[3] Seo H., Park J.Y., Chang J.H., Dae K.S., Noh M.S., Kim S.S., Kang C.-Y., Zhao K., Kim S., Yuk J., "Strong stress composition coupling in Lithium alloy nanoparticles" Nature Communications 10, 3428 2019[4] Kim S., Choi S.J., Zhao K., Yang H., Gobbi G., Zhang S., Li J., “Electrochemically driven mechanical energy harvesting” Nature Communications 7, 10146 2016