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An '''Ion gel''' is a relatively new material where an ionic conducting liquid is immobilized inside a polymer matrix. This allows the design of unique materials with high ionic conductivity combined with the easy handling properties of the solid state. To create an ion gel, a [[block copolymer]] is polymerized along with an [[ionic liquid]] so that self-assembled nanostructures where the ions are selectively soluble. Ion gels can also be made using non-copolymer polymers such as cellulose.
An '''Ion gel''' (or '''Iongel''') is a composite material consisting of an [[ionic liquid]] immobilized by an inorganic or a polymer matrix.<ref name=":0">{{Cite journal|last=Chen|first=Nan|last2=Zhang|first2=Haiqin|last3=Li|first3=Li|last4=Chen|first4=Renjie|last5=Guo|first5=Shaojun|date=2018-04|title=Ionogel Electrolytes for High-Performance Lithium Batteries: A Review|url=http://doi.wiley.com/10.1002/aenm.201702675|journal=Advanced Energy Materials|language=en|volume=8|issue=12|pages=1702675|doi=10.1002/aenm.201702675}}</ref><ref>{{Cite journal|last=Osada|first=Irene|last2=de Vries|first2=Henrik|last3=Scrosati|first3=Bruno|last4=Passerini|first4=Stefano|date=2016|title=Ionic-Liquid-Based Polymer Electrolytes for Battery Applications|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.201504971|journal=Angewandte Chemie International Edition|language=en|volume=55|issue=2|pages=500–513|doi=10.1002/anie.201504971|issn=1521-3773}}</ref> The material has the quality of maintaining high [[ionic conductivity]] while in the solid state. To create an ion gel, the solid matrix is mixed with the [[ionic liquid]] or synthesized in-situ with the ionic liquid. A common practice of utilizing [[block copolymer]] which are polymerized along with an [[ionic liquid]] so that self-assembled nanostructure is generated where the ions are selectively soluble. Ion gels can also be made using non-copolymer polymers such as cellulose, oxides such as [[silicon dioxide]] or refractory materials such as [[boron nitride]].


= Applications =
Ion gels have been successfully used as gate insulators for [[field effect transistors]] which reduces the voltage requirements.<ref>{{cite web|title=Ion Gel as a gate insulator|url=http://www.license.umn.edu/Products/Ion-Gel-as-a-Gate-Insulator-in-Field-Effect-Transistors__Z07062.aspx}}</ref>
[[Ion gel|Jump to navigationJump to search]]
Ion gels have been utilized in many electrical device systems such as in [[Capacitor|capacitors]] as [[Dielectric|dielectrics]]<ref>{{Cite journal|last=Yong|first=Hansol|last2=Park|first2=Habin|last3=Jung|first3=Cheolsoo|date=2020-01-31|title=Quasi-solid-state gel polymer electrolyte for a wide temperature range application of acetonitrile-based supercapacitors|url=http://www.sciencedirect.com/science/article/pii/S0378775319313837|journal=Journal of Power Sources|language=en|volume=447|pages=227390|doi=10.1016/j.jpowsour.2019.227390|issn=0378-7753}}</ref>, as [[Insulator (electricity)|insulators]] for [[field effect transistors]]<ref>{{Cite journal|last=Lodge|first=T. P.|date=2008-07-04|title=MATERIALS SCIENCE: A Unique Platform for Materials Design|url=https://www.sciencemag.org/lookup/doi/10.1126/science.1159652|journal=Science|language=en|volume=321|issue=5885|pages=50–51|doi=10.1126/science.1159652|issn=0036-8075}}</ref>, and as [[Electrolyte|electrolytes]] for [[Lithium-ion battery|lithium-ion batteries]].<ref name=":0" /> The solid state and yet flexible form of ion gels are attractive for modern mobile devices such as formable screens, health monitoring systems, and [[Solid-state battery|solid state batteries.]]<ref name=":1">{{Cite journal|last=Palchoudhury|first=Soubantika|last2=Ramasamy|first2=Karthik|last3=Gupta|first3=Ram K.|last4=Gupta|first4=Arunava|date=2019|title=Flexible Supercapacitors: A Materials Perspective|url=https://www.frontiersin.org/articles/10.3389/fmats.2018.00083/full|journal=Frontiers in Materials|language=English|volume=5|doi=10.3389/fmats.2018.00083|issn=2296-8016}}</ref> Especially for solid state battery applications, the high viscosity of ion gels provides sufficient strength to serve as both an electrolyte and separator between the anode and cathode.<ref name=":0" /> In addition, ion gels are sought after in battery applications as the viscoelastic flow of the gel under stress creates a high quality electrode/electrolyte contact compared to other solid state electrolytes.<ref>{{Cite journal|last=Wang|first=Ziqi|last2=Tan|first2=Rui|last3=Wang|first3=Hongbin|last4=Yang|first4=Luyi|last5=Hu|first5=Jiangtao|last6=Chen|first6=Haibiao|last7=Pan|first7=Feng|date=2018-01|title=A Metal-Organic-Framework-Based Electrolyte with Nanowetted Interfaces for High-Energy-Density Solid-State Lithium Battery|url=http://doi.wiley.com/10.1002/adma.201704436|journal=Advanced Materials|language=en|volume=30|issue=2|pages=1704436|doi=10.1002/adma.201704436}}</ref>

= Thermal Stability =
[[Ion gel|Jump to navigationJump to search]]
Ion gels have been known to be able to sustain upwards of 300 °C before onset of degradation.<ref name=":2">{{Cite journal|last=Zhao|first=Kang|last2=Song|first2=Hongzan|last3=Duan|first3=Xiaoli|last4=Wang|first4=Zihao|last5=Liu|first5=Jiahang|last6=Ba|first6=Xinwu|date=2019/3|title=Novel Chemical Cross-Linked Ionogel Based on Acrylate Terminated Hyperbranched Polymer with Superior Ionic Conductivity for High Performance Lithium-Ion Batteries|url=https://www.mdpi.com/2073-4360/11/3/444|journal=Polymers|language=en|volume=11|issue=3|pages=444|doi=10.3390/polym11030444|pmc=PMC6473542|pmid=30960428}}</ref> The high temperature capability is typically limited by the underlying [[ionic liquid]], which can have a wide range of thermal stability, but are typically stable to at least 250 °C.<ref>{{Cite journal|last=Lewandowski|first=Andrzej|last2=Świderska-Mocek|first2=Agnieszka|date=2009-12|title=Ionic liquids as electrolytes for Li-ion batteries—An overview of electrochemical studies|url=https://linkinghub.elsevier.com/retrieve/pii/S0378775309011616|journal=Journal of Power Sources|language=en|volume=194|issue=2|pages=601–609|doi=10.1016/j.jpowsour.2009.06.089}}</ref> This high temperature stability has been exploited to operate lithium ion battery cells at lab scale up to 175 °C, which is well beyond the capabilities of current commercial electrolytes.<ref name=":3">{{Cite journal|last=Hyun|first=Woo Jin|last2=de Moraes|first2=Ana C. M.|last3=Lim|first3=Jin-Myoung|last4=Downing|first4=Julia R.|last5=Park|first5=Kyu-Young|last6=Tan|first6=Mark Tian Zhi|last7=Hersam|first7=Mark C.|date=2019-08-27|title=High-Modulus Hexagonal Boron Nitride Nanoplatelet Gel Electrolytes for Solid-State Rechargeable Lithium-Ion Batteries|url=https://pubs.acs.org/doi/10.1021/acsnano.9b04989|journal=ACS Nano|language=en|volume=13|issue=8|pages=9664–9672|doi=10.1021/acsnano.9b04989|issn=1936-0851}}</ref>

= Mechanical Properties =
[[Ion gel|Jump to navigationJump to search]]
Given the variety of ion gels, the mechanical properties of this broad class of materials spans a wide range. Often mechanical properties are tailored towards the desired application. Applications that require high flexibility target a highly elastic matrix material such as a [[Cross-link|cross-linked polymer]].<ref name=":1" /><ref name=":2" /> These types of [[Elastomer|elastomeric]] materials offer high degree of [[Elasticity (physics)|elastic]] strain with full recovery, which is desirable in wearable devices that will undergo many stress cycles during their lifetime. Additionally, these types of materials can achieve up to 135% strain at failure indicating a degree of [[ductility]].<ref>{{Cite journal|last=Guo|first=Panlong|last2=Su|first2=Anyu|last3=Wei|first3=Yingjin|last4=Liu|first4=Xiaokong|last5=Li|first5=Yang|last6=Guo|first6=Feifan|last7=Li|first7=Jian|last8=Hu|first8=Zhenyuan|last9=Sun|first9=Junqi|date=2019-05-29|title=Healable, Highly Conductive, Flexible, and Nonflammable Supramolecular Ionogel Electrolytes for Lithium-Ion Batteries|url=https://pubs.acs.org/doi/10.1021/acsami.9b02182|journal=ACS Applied Materials & Interfaces|language=en|volume=11|issue=21|pages=19413–19420|doi=10.1021/acsami.9b02182|issn=1944-8244}}</ref> Applications that require higher strength ion gel will often use a refractory matrix to generate composite strengthening. This is particularly desirable in [[lithium-ion battery]] applications, which seek to deter the growth of lithium [[Dendrite (crystal)|dendrites]] in the cell that can result in an internal [[Short circuit|short-circuit]]. A relationship has been established in lithium-ion batteries between high modulus, strong, solid electrolytes and a reduction in lithium dendrite growth.<ref name=":4">{{Cite journal|last=Lu|first=Yingying|last2=Korf|first2=Kevin|last3=Kambe|first3=Yu|last4=Tu|first4=Zhengyuan|last5=Archer|first5=Lynden A.|date=2014-01-07|title=Ionic-Liquid-Nanoparticle Hybrid Electrolytes: Applications in Lithium Metal Batteries|url=http://doi.wiley.com/10.1002/anie.201307137|journal=Angewandte Chemie International Edition|language=en|volume=53|issue=2|pages=488–492|doi=10.1002/anie.201307137}}</ref> Thereby, a strong ion gel composite can improve the longevity of lithium-ion batteries through reduced internal short circuit failures.

The elastic resistance to flow of ion gels is often measure via [[Dynamic mechanical analysis|Dynamic Mechanical Spectroscopy]]. This method reveals the [[storage modulus]] as well as the [[loss modulus]], which define the stress-strain response of the gel. All ion gels are in the quasi-solid to solid state regime indicating that the [[storage modulus]] is higher than the [[loss modulus]] (i.e. elastic behavior prevails over the energy dissipating liquid-like behavior).<ref>{{Cite web|title=Viscoelasticity and dynamic mechanical testing|url=http://tainstruments.com/pdf/literature/AAN004_Viscoelasticity_and_DMA.pdf|last=Franck|first=A.|date=|website=TA Instruments|url-status=live|archive-url=|archive-date=|access-date=}}</ref> The magnitude of the storage modulus and its ratio to the loss modulus dictate the strength and the [[toughness]] of composite material.<ref name=":2" /> [[Storage modulus]] values for ion gels can vary from approximately 1.0 kPa for typical polymeric-based matrices<ref>{{Cite journal|last=Patel|first=Monalisa|last2=Gnanavel|first2=M.|last3=Bhattacharyya|first3=Aninda J.|date=2011|title=Utilizing an ionic liquid for synthesizing a soft matter polymer “gel” electrolyte for high rate capability lithium-ion batteries|url=http://xlink.rsc.org/?DOI=c1jm12269j|journal=Journal of Materials Chemistry|language=en|volume=21|issue=43|pages=17419|doi=10.1039/c1jm12269j|issn=0959-9428}}</ref> up to approximately 1.0 MPa for refractory-based matrices.<ref name=":3" />

The structure of the composite matrix can play a large role in the outcome of the final bulk mechanical properties. This is especially true for inorganic based matrix materials. Several lab-scale examples have demonstrated a general trend that smaller matrix particle sizes can result in orders of magnitude increase in storage modulus.<ref name=":3" /><ref name=":4" /> This has been attributed to higher surface area to volume ratio of the matrix particles and the higher concentration of nanoscale interactions between the particle and the immobilized [[ionic liquid]].<ref name=":3" /> The higher the interaction forces between the components int he ion gel composite results in a higher force required for [[plastic deformation]] and and an overall stiffer material.


== References ==
== References ==
{{refbegin}}
* {{cite journal | title = MATERIALS SCIENCE: A Unique Platform for Materials Design | author = Lodge, Timothy P | journal = Science | volume = 321 | year = 2008 | pages = 50–51 | doi = 10.1126/science.1159652 | pmid = 18599764 | issue = 5885}}
{{refend}}
{{reflist}}
{{reflist}}


Revision as of 06:24, 20 May 2020

An Ion gel (or Iongel) is a composite material consisting of an ionic liquid immobilized by an inorganic or a polymer matrix.[1][2] The material has the quality of maintaining high ionic conductivity while in the solid state. To create an ion gel, the solid matrix is mixed with the ionic liquid or synthesized in-situ with the ionic liquid. A common practice of utilizing block copolymer which are polymerized along with an ionic liquid so that self-assembled nanostructure is generated where the ions are selectively soluble. Ion gels can also be made using non-copolymer polymers such as cellulose, oxides such as silicon dioxide or refractory materials such as boron nitride.

Applications

Jump to navigationJump to search Ion gels have been utilized in many electrical device systems such as in capacitors as dielectrics[3], as insulators for field effect transistors[4], and as electrolytes for lithium-ion batteries.[1] The solid state and yet flexible form of ion gels are attractive for modern mobile devices such as formable screens, health monitoring systems, and solid state batteries.[5] Especially for solid state battery applications, the high viscosity of ion gels provides sufficient strength to serve as both an electrolyte and separator between the anode and cathode.[1] In addition, ion gels are sought after in battery applications as the viscoelastic flow of the gel under stress creates a high quality electrode/electrolyte contact compared to other solid state electrolytes.[6]

Thermal Stability

Jump to navigationJump to search Ion gels have been known to be able to sustain upwards of 300 °C before onset of degradation.[7] The high temperature capability is typically limited by the underlying ionic liquid, which can have a wide range of thermal stability, but are typically stable to at least 250 °C.[8] This high temperature stability has been exploited to operate lithium ion battery cells at lab scale up to 175 °C, which is well beyond the capabilities of current commercial electrolytes.[9]

Mechanical Properties

Jump to navigationJump to search Given the variety of ion gels, the mechanical properties of this broad class of materials spans a wide range. Often mechanical properties are tailored towards the desired application. Applications that require high flexibility target a highly elastic matrix material such as a cross-linked polymer.[5][7] These types of elastomeric materials offer high degree of elastic strain with full recovery, which is desirable in wearable devices that will undergo many stress cycles during their lifetime. Additionally, these types of materials can achieve up to 135% strain at failure indicating a degree of ductility.[10] Applications that require higher strength ion gel will often use a refractory matrix to generate composite strengthening. This is particularly desirable in lithium-ion battery applications, which seek to deter the growth of lithium dendrites in the cell that can result in an internal short-circuit. A relationship has been established in lithium-ion batteries between high modulus, strong, solid electrolytes and a reduction in lithium dendrite growth.[11] Thereby, a strong ion gel composite can improve the longevity of lithium-ion batteries through reduced internal short circuit failures.

The elastic resistance to flow of ion gels is often measure via Dynamic Mechanical Spectroscopy. This method reveals the storage modulus as well as the loss modulus, which define the stress-strain response of the gel. All ion gels are in the quasi-solid to solid state regime indicating that the storage modulus is higher than the loss modulus (i.e. elastic behavior prevails over the energy dissipating liquid-like behavior).[12] The magnitude of the storage modulus and its ratio to the loss modulus dictate the strength and the toughness of composite material.[7] Storage modulus values for ion gels can vary from approximately 1.0 kPa for typical polymeric-based matrices[13] up to approximately 1.0 MPa for refractory-based matrices.[9]

The structure of the composite matrix can play a large role in the outcome of the final bulk mechanical properties. This is especially true for inorganic based matrix materials. Several lab-scale examples have demonstrated a general trend that smaller matrix particle sizes can result in orders of magnitude increase in storage modulus.[9][11] This has been attributed to higher surface area to volume ratio of the matrix particles and the higher concentration of nanoscale interactions between the particle and the immobilized ionic liquid.[9] The higher the interaction forces between the components int he ion gel composite results in a higher force required for plastic deformation and and an overall stiffer material.

References

  1. ^ a b c Chen, Nan; Zhang, Haiqin; Li, Li; Chen, Renjie; Guo, Shaojun (2018-04). "Ionogel Electrolytes for High-Performance Lithium Batteries: A Review". Advanced Energy Materials. 8 (12): 1702675. doi:10.1002/aenm.201702675. {{cite journal}}: Check date values in: |date= (help)
  2. ^ Osada, Irene; de Vries, Henrik; Scrosati, Bruno; Passerini, Stefano (2016). "Ionic-Liquid-Based Polymer Electrolytes for Battery Applications". Angewandte Chemie International Edition. 55 (2): 500–513. doi:10.1002/anie.201504971. ISSN 1521-3773.
  3. ^ Yong, Hansol; Park, Habin; Jung, Cheolsoo (2020-01-31). "Quasi-solid-state gel polymer electrolyte for a wide temperature range application of acetonitrile-based supercapacitors". Journal of Power Sources. 447: 227390. doi:10.1016/j.jpowsour.2019.227390. ISSN 0378-7753.
  4. ^ Lodge, T. P. (2008-07-04). "MATERIALS SCIENCE: A Unique Platform for Materials Design". Science. 321 (5885): 50–51. doi:10.1126/science.1159652. ISSN 0036-8075.
  5. ^ a b Palchoudhury, Soubantika; Ramasamy, Karthik; Gupta, Ram K.; Gupta, Arunava (2019). "Flexible Supercapacitors: A Materials Perspective". Frontiers in Materials. 5. doi:10.3389/fmats.2018.00083. ISSN 2296-8016.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  6. ^ Wang, Ziqi; Tan, Rui; Wang, Hongbin; Yang, Luyi; Hu, Jiangtao; Chen, Haibiao; Pan, Feng (2018-01). "A Metal-Organic-Framework-Based Electrolyte with Nanowetted Interfaces for High-Energy-Density Solid-State Lithium Battery". Advanced Materials. 30 (2): 1704436. doi:10.1002/adma.201704436. {{cite journal}}: Check date values in: |date= (help)
  7. ^ a b c Zhao, Kang; Song, Hongzan; Duan, Xiaoli; Wang, Zihao; Liu, Jiahang; Ba, Xinwu (2019/3). "Novel Chemical Cross-Linked Ionogel Based on Acrylate Terminated Hyperbranched Polymer with Superior Ionic Conductivity for High Performance Lithium-Ion Batteries". Polymers. 11 (3): 444. doi:10.3390/polym11030444. PMC 6473542. PMID 30960428. {{cite journal}}: Check date values in: |date= (help)CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)
  8. ^ Lewandowski, Andrzej; Świderska-Mocek, Agnieszka (2009-12). "Ionic liquids as electrolytes for Li-ion batteries—An overview of electrochemical studies". Journal of Power Sources. 194 (2): 601–609. doi:10.1016/j.jpowsour.2009.06.089. {{cite journal}}: Check date values in: |date= (help)
  9. ^ a b c d Hyun, Woo Jin; de Moraes, Ana C. M.; Lim, Jin-Myoung; Downing, Julia R.; Park, Kyu-Young; Tan, Mark Tian Zhi; Hersam, Mark C. (2019-08-27). "High-Modulus Hexagonal Boron Nitride Nanoplatelet Gel Electrolytes for Solid-State Rechargeable Lithium-Ion Batteries". ACS Nano. 13 (8): 9664–9672. doi:10.1021/acsnano.9b04989. ISSN 1936-0851.
  10. ^ Guo, Panlong; Su, Anyu; Wei, Yingjin; Liu, Xiaokong; Li, Yang; Guo, Feifan; Li, Jian; Hu, Zhenyuan; Sun, Junqi (2019-05-29). "Healable, Highly Conductive, Flexible, and Nonflammable Supramolecular Ionogel Electrolytes for Lithium-Ion Batteries". ACS Applied Materials & Interfaces. 11 (21): 19413–19420. doi:10.1021/acsami.9b02182. ISSN 1944-8244.
  11. ^ a b Lu, Yingying; Korf, Kevin; Kambe, Yu; Tu, Zhengyuan; Archer, Lynden A. (2014-01-07). "Ionic-Liquid-Nanoparticle Hybrid Electrolytes: Applications in Lithium Metal Batteries". Angewandte Chemie International Edition. 53 (2): 488–492. doi:10.1002/anie.201307137.
  12. ^ Franck, A. "Viscoelasticity and dynamic mechanical testing" (PDF). TA Instruments.{{cite web}}: CS1 maint: url-status (link)
  13. ^ Patel, Monalisa; Gnanavel, M.; Bhattacharyya, Aninda J. (2011). "Utilizing an ionic liquid for synthesizing a soft matter polymer "gel" electrolyte for high rate capability lithium-ion batteries". Journal of Materials Chemistry. 21 (43): 17419. doi:10.1039/c1jm12269j. ISSN 0959-9428.
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