Structural battery
{{Short description|Battery that serves a structural function}}
{{Use dmy dates|date=July 2022}}
Structural batteries are multifunctional materials or structures, capable of acting as an electrochemical energy storage system (i.e. batteries) while possessing mechanical integrity.{{cite conference |first1=J. F. |last1=Snyder |first2=R.H. |last2=Carter |first3=E.L. |last3=Wong |first4=P. A. |last4=Nguyen |first5=K. |last5=Xu |first6=E. H. |last6=Ngo |first7=E. D. |last7=Wetzel |title=Multifunctional Structural Composite Batteries |date=November 2006 |conference=Proceedings of Society for the Advancement of Materiel and Process Engineering (SAMPE) 2006 Fall Technical Conference }}{{cite journal |last1=Johannisson |first1=Wilhelm |last2=Ihrner |first2=Niklas |last3=Zenkert |first3=Dan |last4=Johansson |first4=Mats |last5=Carlstedt |first5=David |last6=Asp |first6=Leif E. |last7=Sieland |first7=Fabian |title=Multifunctional performance of a carbon fiber UD lamina electrode for structural batteries |journal=Composites Science and Technology |date=November 2018 |volume=168 |pages=81–87 |doi=10.1016/j.compscitech.2018.08.044 |doi-access=free }}Richa Chaudhary, Johanna Xu, Zhenyuan Xia, Leif E. Asp, Unveiling the Multifunctional Carbon Fiber Structural Battery, 2409725, 2024, https://doi.org/10.1002/adma.202409725
They help save weight and are useful in transport applications{{cite news |last1=Bradburn |first1=David |title=Structural Batteries |url=https://www.materialstoday.com/energy/comment/structural-batteries/ |accessdate=30 January 2020 |publisher=Materials Today |date=12 February 2014}}{{cite news |title=Study links carbon fibre microstructure to Lithium insertion mechanism in structural batteries |url=https://www.greencarcongress.com/2018/10/20181018-chalmers.html |publisher=Green Car Congress |date=18 October 2018}} such as electric vehicles and drones,{{Cite web |title=Structural batteries lighten drones' loads |url=https://cen.acs.org/materials/energy-storage/Structural-batteries-lighten-dronesloads/97/i2 |access-date=2020-08-04 |website=Chemical & Engineering News |publisher=American Chemical Society}} because of their potential to improve system efficiencies. Two main types of structural batteries can be distinguished: embedded batteries and laminated structural electrodes.{{cite journal |last1=Asp |first1=Leif |title=Structural battery composites: a review |journal=Functional Composites and Structures |date=21 November 2019 |volume=1 |issue=4 |page=42001 |doi=10.1088/2631-6331/ab5571 |bibcode=2019FCS.....1d2001A |s2cid=210257472 |url=http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-282189 }}
Embedded batteries
Embedded batteries represent multifunctional structures where lithium-ion battery cells are efficiently embedded into a composite structure, and more often sandwich structures. In a sandwich design, state-of-the-art lithium-ion batteries are embedded forming a core material and bonded in between two thin and strong face sheets (e.g. aluminium). In-plane and bending loads are carried by face sheets while the battery core takes up transverse shear and compression loads as well as storing the electrical energy. The multifunctional structure can then be used as a load-bearing as well as an energy storage material.{{cite journal |last1=Pereira |first1=Tony |s2cid=13864856 |title=Energy Storage Structural Composites: a Review |journal=Journal of Composite Materials |date=29 January 2009 |volume=43 |issue=5 |page=549 |doi=10.1177/0021998308097682 |bibcode=2009JCoMa..43..549P }}
Laminated structural electrodes
In laminated structural electrodes the electrode material possesses an intrinsic load-bearing and energy storage function. Such batteries are also called massless batteries, since in theory vehicle body parts could also store energy thus not adding any additional weight to the vehicle as additional batteries would not be needed.{{cite web |url=https://www.azocleantech.com/amp/article.aspx?ArticleID=1208 |title=Massless Energy Storage: The Next Step in Battery Technology |website=www.azocleantech.com |access-date=22 February 2022 |archive-url=https://web.archive.org/web/20211025105025/https://www.azocleantech.com/amp/article.aspx?ArticleID=1208 |archive-date=25 October 2021 |url-status=dead}} An example for such batteries are those based on a zinc anode, manganeseoxide cathode and a fiber/ polymer composite electrolyte.{{cite journal |last1=Wang |first1=Mingqiang |title=Biomimetic Solid-State Zn2+ Electrolyte for Corrugated Structural Batteries |journal=ACS Nano |date=4 January 2019 |volume=13 |issue=2 |pages=1107–1115 |doi=10.1021/acsnano.8b05068 |pmid=30608112 |s2cid=58589418 }} The structural electrolyte enables stable charge and discharge performance. This assembly has been demonstrated in an unmanned aerial vehicle. A commonly proposed structural battery is based on a carbon fiber reinforced polymer (CFRP) concept. Here, carbon fibers serve simultaneously as electrodes and structural reinforcement. The lamina is composed of carbon fibers that are embedded in a matrix material (e.g. a polymer). Multiple layers of carbon fibers are impregnated with a matrix that enables load transfer between the fibers but also lithium-ion transport, unlike commonly used vinylester or epoxy matrices. This type of energy storage system can be based on a nickel{{cite news |title=BAE provides details of 'structural battery' technology |url=https://www.bbc.com/news/technology-17014808 |accessdate=30 January 2020 |publisher=BBC |date=8 March 2012}} or on lithium-ion chemistry.{{cite journal |last1=Asp |first1=Leif |title=Structural battery composites: a review |journal=Functional Composites and Structures |date=21 November 2019 |volume=1 |issue=4 |page=42001 |doi=10.1088/2631-6331/ab5571 |bibcode=2019FCS.....1d2001A |s2cid=210257472 |url=http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-282189 }} The laminate is made of the combination of a negative electrode, a separator and a positive electrode, embedded in an ionically conductive and structural electrolyte. In the laminated structural electrodes concept, carbon fibers can be used to intercalate e.g. lithium-ions (structural anode); similarly, to commercially available graphite anodes. The structural cathode consists of carbon fibers coated with electrochemically active species, e.g. lithium oxide particles. An example of a structural battery exploiting a carbon fiber negative electrode and lithium iron phosphate positive electrode was demonstrated to be capable of lighting an LED.{{Cite journal|last1=Asp|first1=Leif E.|last2=Bouton|first2=Karl|last3=Carlstedt|first3=David|last4=Duan|first4=Shanghong|last5=Harnden|first5=Ross|last6=Johannisson|first6=Wilhelm|last7=Johansen|first7=Marcus|last8=Johansson|first8=Mats K. G.|last9=Lindbergh|first9=Göran|last10=Liu|first10=Fang|last11=Peuvot|first11=Kevin|title=A Structural Battery and its Multifunctional Performance|journal=Advanced Energy and Sustainability Research|year=2021|volume=2|issue=3|language=en|pages=2000093|doi=10.1002/aesr.202000093|issn=2699-9412|doi-access=free|bibcode=2021AdESR...200093A }} Some separator material is used in between the two structural electrodes to prevent short-circuits.{{cite journal |last1=Asp |first1=Leif |title=Structural battery composites: a review |journal=Functional Composites and Structures |date=21 November 2019 |volume=1 |issue=4 |page=42001 |doi=10.1088/2631-6331/ab5571 |bibcode=2019FCS.....1d2001A |s2cid=210257472 |url=http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-282189 }}{{cite news |last1=Hurst |first1=Nathan |title=Let's Build Cars Out of Batteries |url=https://www.smithsonianmag.com/innovation/lets-build-cars-out-batteries-180970693/ |accessdate=30 January 2020 |publisher=Smithsonian Magazine |date=2 November 2018}} However, the CFRC concept described above is still being researched.{{cite news |last1=Bradburn |first1=David |title=Structural Batteries |url=https://www.materialstoday.com/energy/comment/structural-batteries/ |accessdate=30 January 2020 |publisher=Materials Today |date=12 February 2014}}