Piezoelectrochemical (PEC) materials convert mechanical energy into electrochemical energy through Faradaic charge transfer, allowing energy harvesting at very low frequencies. Electric power is generated through micro-Hz cyclical compression of commercially available lithium-ion batteries with varying PEC effects. Difference in power generation between different PEC systems is analyzed based on standard charge/discharge curve and the relationship between the coupling of mechanical stress and voltage. This study experimentally demonstrates the varying energy converting properties between three different types of PEC systems and explores an important parameter space for controlling power generation behavior in ultra-low-frequency mechanical energy harvesting of PEC materials. (C) The Author(s) 2019. Published by ECS.