Piezoelectrochemical transducer effect

The PECT effect was first reported by Dr. F Lincoln Vogel in 1981 when studying how intercalation voltages could be used to provide an actuation force in graphitized carbon fibres.{{Cite book|last=Kading|first=Glen|url=https://scholar.afit.edu/cgi/viewcontent.cgi?article=3634&context=etd|title=Piezo-Electrochemical Transducer Effect (PECT) Intercalated Graphite Micro-Electrochemical Actuators|publisher=Department of the Airforce, Air University|year=2007|location=Ohio|pages=3}} The research used sulphate (SO₄) ions from sulfuric acid to intercalate into the microstructure of carbon fibers, forming graphite intercalation compounds (GICs). It was hypothesized that an axial strain of up to 2% should be possible, however only 0.2% was observed due to experimental limitations.{{Cite book|last=Kading|first=Glen|url=https://scholar.afit.edu/cgi/viewcontent.cgi?article=3634&context=etd|title=Piezo-Electrochemical Transducer Effect (PECT) Intercalated Graphite Micro-Electrochemical Actuators|publisher=Department of the Air Force, Air University|year=2007|location=Ohio|pages=18}}

The effect is often explained by the theories of Larché and Cahn{{Cite journal|last1=Larché|first1=Francis|last2=Cahn|first2=John W.|date=January 1978|title=A nonlinear theory of thermochemical equilibrium of solids under stress|url=http://dx.doi.org/10.1016/0001-6160(78)90201-8|journal=Acta Metallurgica|volume=26|issue=1|pages=53–60|doi=10.1016/0001-6160(78)90201-8|issn=0001-6160|url-access=subscription}}{{Cite journal|last1=Larché|first1=F|last2=Cahn|first2=J.W|date=August 1973|title=A linear theory of thermochemical equilibrium of solids under stress|url=http://dx.doi.org/10.1016/0001-6160(73)90021-7|journal=Acta Metallurgica|volume=21|issue=8|pages=1051–1063|doi=10.1016/0001-6160(73)90021-7|issn=0001-6160|url-access=subscription}}{{Cite journal|last1=Larché|first1=F.C.|last2=Cahn|first2=J.W.|date=March 1985|title=Overview no. 41 The interactions of composition and stress in crystalline solids|url=http://dx.doi.org/10.1016/0001-6160(85)90077-x|journal=Acta Metallurgica|volume=33|issue=3|pages=331–357|doi=10.1016/0001-6160(85)90077-x|s2cid=97901429 |issn=0001-6160|url-access=subscription}} who derived mathematical formulations for the equilibrium relationships between the electric potential, chemical potential, and mechanical stress in solid materials. In summary the theory states that solid materials under mechanical stress undergo a change in chemical potential, which in turn affects their electrical potential.{{Cite journal |last1=Harnden |first1=Ross |last2=Carlstedt |first2=David |last3=Zenkert |first3=Dan |last4=Lindbergh |first4=Göran |date=2022-07-12 |title=Multifunctional Carbon Fiber Composites: A Structural, Energy Harvesting, Strain-Sensing Material |journal=ACS Applied Materials & Interfaces |volume=14 |issue=29 |language=en |pages=33871–33880 |doi=10.1021/acsami.2c08375 |pmid=35820025 |pmc=9335530 |issn=1944-8244|doi-access=free }}

Since PECT materials expand and contract upon ion-insertion it is possible to use this effect for actuation. Several different materials have been proposed for this, including: carbon fibers inserted with lithium,{{Cite journal |last=Harnden |first=Ross |date=2021 |title=Lightweight multifunctional composites : An investigation into ion-inserted carbon fibres for structural energy storage, shape-morphing, energy harvesting & strain-sensing |url=http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-303558}} sodium, and potassium; lithium cobalt oxide; and vanadium oxide nanofibers inserted with lithium and sodium. Applications for PECT-based actuation range from microelectromechanical systems (MEMS),{{Cite journal|last1=Koyama|first1=Y.|last2=Chin|first2=T. E.|last3=Rhyner|first3=U.|last4=Holman|first4=R. K.|last5=Hall|first5=S. R.|last6=Chiang|first6=Y.-M.|date=2006-03-03|title=Harnessing the Actuation Potential of Solid-State Intercalation Compounds|url=http://dx.doi.org/10.1002/adfm.200500633|journal=Advanced Functional Materials|volume=16|issue=4|pages=492–498|doi=10.1002/adfm.200500633|s2cid=98388269 |issn=1616-301X|url-access=subscription}} to large morphing structures.{{Cite web|date=2020-05-13|title=Shape-Shifting Carbon Fiber Can Be Used in Aerodynamics, Robotics, and More|url=https://interestingengineering.com/shape-shifting-carbon-fiber-can-be-used-in-aerodynamics-robotics-and-more|access-date=2021-03-19|website=interestingengineering.com|language=en-US}}{{Cite journal|last1=Johannisson|first1=Wilhelm|last2=Harnden|first2=Ross|last3=Zenkert|first3=Dan|last4=Lindbergh|first4=Göran|date=2020-04-07|title=Shape-morphing carbon fiber composite using electrochemical actuation|journal=Proceedings of the National Academy of Sciences|language=en|volume=117|issue=14|pages=7658–7664|doi=10.1073/pnas.1921132117|issn=0027-8424|pmc=7149449|pmid=32213583|bibcode=2020PNAS..117.7658J |doi-access=free }}

Different materials exhibit different amounts of expansion/contraction, with a response that is dependent on the type of ion, as well as the amount of charge. For example, silicon expands by more than 300% when inserted with lithium, whereas graphite expands by around 13%. Carbon fibres expand by up to 1% when inserted with lithium, but only around 0.2% when inserted with potassium.

As PECT materials exhibit a change in voltage upon application of strain, it is possible to calibrate this change in voltage to the level of strain in a material. This has been proposed for applications in battery health monitoring,{{Cite book|last=Cannarella|first=John|url=https://www.worldcat.org/oclc/933783446|title=Coupled mechanical and electrochemical phenomena in lithium-ion batteries.|others=Princeton University. Department of Mechanical and Aerospace Engineering|isbn=978-1-321-98223-7|volume=76-12B(E)|oclc=933783446}} as well as structural health monitoring.

When mechanical strain is applied to a PECT material it changes the chemical potential, and therefore the electric potential of that material.{{Cite book |last=Preimesberger |first=Juliane Irine |url=https://dataspace-dev.princeton.edu/bitstream/99999/fk4bp1kz2b/1/Preimesberger_princeton_0181D_14131.pdf |title=Studying the Piezoelectrochemical Phenomenon Using Lithium-Ion Batteries |publisher=Princeton, NJ : Princeton University |year=2022 |language=English}} Since current flows from more negative materials to more positive materials, it is possible to induce a current flow between two ionically connected materials by simply applying a mechanical strain. It is therefore possible to harness and convert mechanical energy into electrical energy.

A number of materials have been demonstrated to be capable of PECT-based energy harvesting, including: carbon fibers inserted with lithium,{{Cite journal |last1=Harnden |first1=Ross |last2=Carlstedt |first2=David |last3=Zenkert |first3=Dan |last4=Lindbergh |first4=Göran |date=2022-07-27 |title=Multifunctional Carbon Fiber Composites: A Structural, Energy Harvesting, Strain-Sensing Material |journal=ACS Applied Materials & Interfaces |language=en |volume=14 |issue=29 |pages=33871–33880 |doi=10.1021/acsami.2c08375 |issn=1944-8244 |pmc=9335530 |pmid=35820025}} sodiated black phosphorus; lithiated aluminium; and lithiated silicon. A structural carbon fibre composite has also been shown to be capable of harvesting energy using the PECT effect. Conventional lithium-ion batteries have also been shown to be capable of PECT-based energy harvesting.{{Cite journal|last1=Cannarella|first1=John|last2=Arnold|first2=Craig B.|date=December 2015|title=Toward Low-Frequency Mechanical Energy Harvesting Using Energy-Dense Piezoelectrochemical Materials|url=http://doi.wiley.com/10.1002/adma.201502974|journal=Advanced Materials|language=en|volume=27|issue=45|pages=7440–7444|doi=10.1002/adma.201502974|pmid=26487160|bibcode=2015AdM....27.7440C |s2cid=205262921 |url-access=subscription}}

This effect has most often been demonstrated using a two-electrode bending setup:

1. Two electrodes of the same material are connected ionically through an electrolyte, and electrically via an outer circuit.
2. A bending deformation is applied causing tension in one electrode and compression in the other.
3. The resulting change in chemical potential results in current flow in the outer circuit, which can be used to power an external device.

PECT energy harvesting is limited by the rate of ionic diffusion, and therefore is only efficient at low frequency (typically below around 1 Hz).

Figures of merit for comparing different PECT-based energy harvesters were formulated by Preimesberger et al.{{Cite journal|last1=Preimesberger|first1=Juliane I.|last2=Kang|first2=SeungYeon|last3=Arnold|first3=Craig B.|date=September 2020|title=Figures of Merit for Piezoelectrochemical Energy-Harvesting Systems|journal=Joule|language=en|volume=4|issue=9|pages=1893–1906|doi=10.1016/j.joule.2020.07.019|doi-access=free|bibcode=2020Joule...4.1893P }}

The PECT effect is also present in typical ion-insertion-based battery electrodes (e.g. Li-ion).{{Cite journal|last1=Funayama|first1=Keita|last2=Nakamura|first2=Takashi|last3=Kuwata|first3=Naoaki|last4=Kawamura|first4=Junichi|last5=Kawada|first5=Tatsuya|last6=Amezawa|first6=Koji|date=2015|title=Effect of Mechanical Stress on Lithium Chemical Potential in Positive Electrodes and Solid Electrolytes for Lithium Ion Batteries|url=https://www.jstage.jst.go.jp/article/electrochemistry/83/10/83_15-E00083/_article|journal=Electrochemistry|language=en|volume=83|issue=10|pages=894–897|doi=10.5796/electrochemistry.83.894|issn=1344-3542|doi-access=free}}{{Cite book|last1=Cannarella|first1=John|last2=Leng|first2=Collen Z.|last3=Arnold|first3=Craig B.|title=Energy Harvesting and Storage: Materials, Devices, and Applications V|date=2014-06-05|editor-last=Dhar|editor-first=Nibir K.|editor2-last=Balaya|editor2-first=Palani|editor3-last=Dutta|editor3-first=Achyut K.|chapter=On the coupling between stress and voltage in lithium-ion pouch cells|volume=9115|chapter-url=http://proceedings.spiedigitallibrary.org/proceeding.aspx?doi=10.1117/12.2055152|location=Baltimore, Maryland, USA|pages=69–76|doi=10.1117/12.2055152|s2cid=15700625}} The electrodes expand and contract when inserted with ions, which is one of the issues that leads to battery ageing and capacity loss over time.{{Cite journal|last1=Pender|first1=Joshua P.|last2=Jha|first2=Gaurav|last3=Youn|first3=Duck Hyun|last4=Ziegler|first4=Joshua M.|last5=Andoni|first5=Ilektra|last6=Choi|first6=Eric J.|last7=Heller|first7=Adam|last8=Dunn|first8=Bruce S.|last9=Weiss|first9=Paul S.|last10=Penner|first10=Reginald M.|last11=Mullins|first11=C. Buddie|date=2020-02-25|title=Electrode Degradation in Lithium-Ion Batteries|journal=ACS Nano|language=en|volume=14|issue=2|pages=1243–1295|doi=10.1021/acsnano.9b04365|pmid=31895532|s2cid=209677531 |issn=1936-0851|doi-access=free}} The PECT effect in battery electrodes could be an issue in situations where battery electrodes are mechanically stressed (e.g. in structural batteries), causing a change in electrical potential when the stress-state changes.

It has been proposed that the PECT effect in Li-ion batteries could be exploited to measure battery health., and to harvest mechanical energy.

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Category:Electrochemistry

Category:Piezoelectric materials