In　an　electrochemical　cell,　unequal　mechanical　work　due　to　mass　action　into　the　two　electrodes　can　generate　chemical　potential　difference　that　drives　Li+　flow　across　the　electrolyte,　constituting　the　fundamental　basis　for　electrochemically　driven　mechanical　energy　harvesting.　The　diffusional　time　scale　inherent　to　the　electrochemical　setting　renders　efficient　low-frequency　energy　conversion.　From　thermodynamic　analyses　we　reveal　that　there　exist　two　distinct　paradigms　for　electrochemically　driven　mechanical　energy　harvesting,　enabled　by　pressure　or　molar-volume　asymmetry　of　the　electrodes.　Guided　by　the　thermodynamic　framework,　we　prototype　the　first　molar-volume　asymmetry　based　energy　harvester　consisting　of　an　intercalation-conversion　electrode　couple.　The　harvester　can　operate　under　globally　uniform　pressure　and　deliver　a　high　power　density　of　~0.90　µW　cm−2　with　long-term　durability.　Under　an　open-circuit　condition,　the　device　operates　in　a　novel　ratchetting　mode　under　which　compression/decompression　cycling　causes　continuous　rise　in　voltage,　yielding　a　blasting　power　output　of　~143.60　µW　cm−2.　Such　a　ratchet　effect　arises　due　to　the　chemomechanically　induced　residual　stress　in　the　electrodes　during　cycling.　Compared　to　the　pressure-asymmetry　based　harvesters,　the　new　harvester　offers　high　scalability,　processability,　safety,　and　large　working　area,　which　make　it　easy　to　increase　the　output　power　through　synchronizing　multilayer　with　large　areas.　Our　device　enables　mechanical　energy　harvesting　from　low-frequency　resources,　including　human　daily　activities.　©　2020　Elsevier　Ltd