Varying Power Generation in Ultra Low-Frequency Mechanical Energy Harvesting of Piezoelectrochemical Materials

Abstract

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.

Hydrogel Ionic Diodes toward Harvesting Ultralow‐Frequency Mechanical Energy

“…The concept of hydrogel ionic diode, with further optimization in material selection and architecture design, holds promise as a new form of efficient energy harvesting at ultralow frequencies, and can be also applied to other ion‐based energy devices including fuel cells and batteries. [ 41,42 ] It is anticipated that hydrogel ionotronics will enable novel ionic‐current‐based flexible and wearable devices for sensing, soft robotics, machine‐human interface, and energy harvesting. [ 43 ]…”

Figures of Merit for Piezoelectrochemical Energy-Harvesting Systems

“…However, in practice, only a few materials that harvest energy in this fashion have been evaluated in recent literature. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] Experimental demonstrations of this effect have been reported in lithium-cobalt-oxide-graphite, 5,7,8 sodium-phosphorus, 6 lithium-carbon, 9 lithiumsilicon, 10,11 and lithium-aluminum systems, 12 among others. Our group has previously demonstrated that commercially available lithium-ion pouch cells exhibit this effect and can be used in an energy-harvesting cycle by mechanically loading and unloading the cells.…”

“…A recently identified mechanical micro-energy-harvesting mechanism, called the piezoelectrochemical (PEC) effect, is used in one such harvester. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] PEC systems, also known as mechano-electrochemical systems or strain energy harvesters, among other names, have higher theoretical energy densities and much lower harvesting frequencies than other mechanical energy harvesters. 5 This makes them ideal for harvesting applications that require higher energy densities and lower frequencies than piezoelectrics can provide.…”

“…Our group has previously demonstrated that commercially available lithium-ion pouch cells exhibit this effect and can be used in an energy-harvesting cycle by mechanically loading and unloading the cells. 5,7,8,15 The voltage and current outputs of these harvesters are not high enough for most practical energy-harvesting applications. Significant work needs to be done to design a practical harvester that can be commercially viable.…”

“…Previous research has suggested a coupling factor K, which linearly relates the system's change in potential DU 0 with applied stress Ds. 5,7 Previously, this coupling factor was defined as an effective change in voltage with respect to stress, but this factor was dependent on many variables 5,7,15 :…”