Editing Solid oxide fuel cell (section)

===Electrolyte===
The electrolyte is a dense layer of ceramic that conducts oxygen ions. Its electronic conductivity must be kept as low as possible to prevent losses from leakage currents. The high operating temperatures of SOFCs allow the kinetics of oxygen ion transport to be sufficient for good performance. However, as the operating temperature approaches the lower limit for SOFCs at around {{nowrap|600 °C,}} the electrolyte begins to have large ionic transport resistances and affect the performance. Popular electrolyte materials include [[yttria-stabilized zirconia]] (YSZ) (often the 8% form 8YSZ), scandia stabilized zirconia ([[ScSZ]]) (usually 9&nbsp;mol%&nbsp;Sc<sub>2</sub>O<sub>3</sub> – 9ScSZ) and [[gadolinium doped ceria]] (GDC).<ref>{{cite journal |author1=Nigel Sammes |author2=Alevtina Smirnova |author3=Oleksandr Vasylyev | title=Fuel Cell Technologies: State and Perspectives | journal=NATO Science Series, Mathematics, Physics and Chemistry | year=2005 | volume=202 | pages=19–34 | doi=10.1007/1-4020-3498-9_3|bibcode=2005fcts.conf.....S }}</ref> The electrolyte material has crucial influence on the cell performances.<ref name="elmater">{{cite journal | doi=10.1038/35104620 | author=Steele, B.C.H., Heinzel, A. | title=Materials for fuel-cell technologies | journal=Nature | year=2001 | volume=414 | issue=15 November | pages=345–352 | pmid=11713541| bibcode=2001Natur.414..345S | s2cid=4405856 }}</ref> Detrimental reactions between YSZ electrolytes and modern cathodes such as [[lanthanum strontium cobalt ferrite]] (LSCF) have been found, and can be prevented by thin (<100&nbsp;nm) [[ceria]] diffusion barriers.<ref>{{cite journal |author1=Mohan Menon |author2=Kent Kammer | title= Processing of Ce<sub>1-x</sub>Gd<sub>x</sub>O<sub>2-δ</sub> (GDC) Thin Films from Precursors for Application in Solid Oxide Fuel Cells| journal= Advanced Materials Research| year=2007 | volume=15–17 | pages=293–298 | doi=10.4028/www.scientific.net/AMR.15-17.293|s2cid=98044813 |display-authors=etal}}</ref>

If the conductivity for oxygen ions in SOFC can remain high even at lower temperatures (current target in research ~500&nbsp;°C), material choices for SOFC will broaden and many existing problems can potentially be solved. Certain processing techniques such as thin film deposition<ref name="Charpentier2000">{{cite journal|last1=Charpentier|first1=P|title=Preparation of thin film SOFCs working at reduced temperature|journal=Solid State Ionics|volume=135|issue=1–4|year=2000|pages=373–380|issn=0167-2738|doi=10.1016/S0167-2738(00)00472-0|s2cid=95598314}}</ref> can help solve this problem with existing materials by:

* reducing the traveling distance of oxygen ions and electrolyte resistance as resistance is proportional to conductor length;
* producing grain structures that are less resistive such as columnar grain structure;
* controlling the microstructural nano-crystalline fine grains to achieve "fine-tuning" of electrical properties;
* building composite possessing large interfacial areas as interfaces have been shown to have extraordinary electrical properties.