Fast-ion conductor

Last updated
A proton conductor, specifically, superionic ice, in a static electric field. Superionic ice conducting.svg
A proton conductor, specifically, superionic ice, in a static electric field.

In materials science, fast ion conductors are solid conductors with highly mobile ions. These materials are important in the area of solid state ionics, and are also known as solid electrolytes and superionic conductors. These materials are useful in batteries and various sensors. Fast ion conductors are used primarily in solid oxide fuel cells. As solid electrolytes they allow the movement of ions without the need for a liquid or soft membrane separating the electrodes. The phenomenon relies on the hopping of ions through an otherwise rigid crystal structure.

Contents

Mechanism

Fast ion conductors are intermediate in nature between crystalline solids which possess a regular structure with immobile ions, and liquid electrolytes which have no regular structure and fully mobile ions. Solid electrolytes find use in all solid-state supercapacitors, batteries, and fuel cells, and in various kinds of chemical sensors.

Classification

In solid electrolytes (glasses or crystals), the ionic conductivity σi can be any value, but it should be much larger than the electronic one. Usually, solids where σi is on the order of 0.0001 to 0.1 Ω−1 cm−1 (300 K) are called superionic conductors.

Proton conductors

Proton conductors are a special class of solid electrolytes, where hydrogen ions act as charge carriers. One notable example is superionic water.

Superionic conductors

Superionic conductors where σi is more than 0.1 Ω−1 cm−1 (300 K) and the activation energy for ion transport Ei is small (about 0.1 eV), are called advanced superionic conductors. The most famous example of advanced superionic conductor-solid electrolyte is RbAg4I5 where σi > 0.25 Ω−1 cm−1 and σe ~10−9 Ω−1 cm−1 at 300 K. [1] [2] The Hall (drift) ionic mobility in RbAg4I5 is about 2×10−4 cm2/(V•s) at room temperatures. [3] The σe – σi systematic diagram distinguishing the different types of solid-state ionic conductors is given in the figure. [4] [5]

Classification of solid-state ionic conductors by the lg (electronic conductivity, se) - lg (ionic conductivity, si) diagram. Regions 2, 4, 6 and 8 are solid electrolytes (SEs), materials with si [?] se; regions 1, 3, 5 and 7 are mixed ion-electron conductors (MIECs). 3 and 4 are superionic conductors (SICs), i.e. materials with si > 0.001 O cm . 5 and 6 are advanced superionic conductors (AdSICs), where si > 10 O cm (300 K), energy activation Ei about 0.1 eV. 7 and 8 are hypothetical AdSIC with Ei [?] kBT [?]0.03 eV (300 K). Electronic ionic conductivity diagram.JPG
Classification of solid-state ionic conductors by the lg (electronic conductivity, σe) – lg (ionic conductivity, σi) diagram. Regions 2, 4, 6 and 8 are solid electrolytes (SEs), materials with σi ≫ σe; regions 1, 3, 5 and 7 are mixed ion-electron conductors (MIECs). 3 and 4 are superionic conductors (SICs), i.e. materials with σi > 0.001 Ω cm . 5 and 6 are advanced superionic conductors (AdSICs), where σi > 10 Ω cm (300 K), energy activation Ei about 0.1 eV. 7 and 8 are hypothetical AdSIC with Ei ≈ kBT ≈0.03 eV (300 К).

No clear examples have been described as yet, of fast ion conductors in the hypothetical advanced superionic conductors class (areas 7 and 8 in the classification plot). However, in crystal structure of several superionic conductors, e.g. in the minerals of the pearceite-polybasite group, the large structural fragments with activation energy of ion transport Ei < kBT (300 К) had been discovered in 2006. [6]

Examples

Zirconia-based materials

A common solid electrolyte is yttria-stabilized zirconia, YSZ. This material is prepared by doping Y2O3 into ZrO2. Oxide ions typically migrate only slowly in solid Y2O3 and in ZrO2, but in YSZ, the conductivity of oxide increases dramatically. These materials are used to allow oxygen to move through the solid in certain kinds of fuel cells. Zirconium dioxide can also be doped with calcium oxide to give an oxide conductor that is used in oxygen sensors in automobile controls. Upon doping only a few percent, the diffusion constant of oxide increases by a factor of ~1000. [7]

Other conductive ceramics function as ion conductors. One example is NASICON, (Na3Zr2Si2PO12), a sodium super-ionic conductor

beta-Alumina

Another example of a popular fast ion conductor is beta-alumina solid electrolyte. [8] Unlike the usual forms of alumina, this modification has a layered structure with open galleries separated by pillars. Sodium ions (Na+) migrate through this material readily since the oxide framework provides an ionophilic, non-reducible medium. This material is considered as the sodium ion conductor for the sodium–sulfur battery.

Fluoride ion conductors

Lanthanum trifluoride (LaF3) is conductive for F− ions, used in some ion selective electrodes. Beta-lead fluoride exhibits a continuous growth of conductivity on heating. This property was first discovered by Michael Faraday.

Iodides

A textbook example of a fast ion conductor is silver iodide (AgI). Upon heating the solid to 146 °C, this material adopts the alpha-polymorph. In this form, the iodide ions form a rigid cubic framework, and the Ag+ centers are molten. The electrical conductivity of the solid increases by 4000x. Similar behavior is observed for copper(I) iodide (CuI), rubidium silver iodide (RbAg4I5), [9] and Ag2HgI4.

Other Inorganic materials

Organic materials

History

The important case of fast ionic conduction is one in a surface space-charge layer of ionic crystals. Such conduction was first predicted by Kurt Lehovec. [14] As a space-charge layer has nanometer thickness, the effect is directly related to nanoionics (nanoionics-I). Lehovec's effect is used as a basis for developing nanomaterials for portable lithium batteries and fuel cells.

See also

Related Research Articles

An electrolyte is a medium containing ions that are electrically conductive through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dissolving, the substance separates into cations and anions, which disperse uniformly throughout the solvent. Solid-state electrolytes also exist. In medicine and sometimes in chemistry, the term electrolyte refers to the substance that is dissolved.

<span class="mw-page-title-main">Lithium polymer battery</span> Lithium-ion battery using a polymer electrolyte

A lithium polymer battery, or more correctly, lithium-ion polymer battery, is a rechargeable battery of lithium-ion technology using a polymer electrolyte instead of a liquid electrolyte. Highly conductive semisolid (gel) polymers form this electrolyte. These batteries provide higher specific energy than other lithium battery types. They are used in applications where weight is critical, such as mobile devices, radio-controlled aircraft, and some electric vehicles.

<span class="mw-page-title-main">Proton conductor</span> Type of electrolyte

A proton conductor is an electrolyte, typically a solid electrolyte, in which H+ are the primary charge carriers.

Nanoionics is the study and application of phenomena, properties, effects, methods and mechanisms of processes connected with fast ion transport (FIT) in all-solid-state nanoscale systems. The topics of interest include fundamental properties of oxide ceramics at nanometer length scales, and fast ion conductor /electronic conductor heterostructures. Potential applications are in electrochemical devices for conversion and storage of energy, charge and information. The term and conception of nanoionics were first introduced by A.L. Despotuli and V.I. Nikolaichik in January 1992.

<span class="mw-page-title-main">Kurt Lehovec</span>

Kurt Lehovec was one of the pioneers of the integrated circuit. While also pioneering the photo-voltaic effect, light-emitting diodes and lithium batteries, he innovated the concept of p-n junction isolation used in every circuit element with a guard ring: a reverse-biased p-n junction surrounding the planar periphery of that element. This patent was assigned to Sprague Electric.

Beta-alumina solid electrolyte (BASE) is a fast ion conductor material used as a membrane in several types of molten salt electrochemical cell. Currently there is no known substitute available. β-Alumina exhibits an unusual layered crystal structure which enables very fast ion transport. β-Alumina is not an isomorphic form of aluminium oxide (Al2O3), but a sodium polyaluminate. It is a hard polycrystalline ceramic, which, when prepared as an electrolyte, is complexed with a mobile ion, such as Na+, K+, Li+, Ag+, H+, Pb2+, Sr2+ or Ba2+ depending on the application. β-Alumina is a good conductor of its mobile ion yet allows no non-ionic (i.e., electronic) conductivity. The crystal structure of the β-alumina provides an essential rigid framework with channels along which the ionic species of the solid can migrate. Ion transport involves hopping from site to site along these channels. Since the 1970's this technology has been thoroughly developed, resulting in interesting applications. Its special characteristics on ion and electrical conductivity make this material extremely interesting in the field of energy storage.

<span class="mw-page-title-main">Ionic conductivity (solid state)</span>

Ionic conductivity is a measure of a substance's tendency towards ionic conduction. Ionic conduction is the movement of ions. The phenomenon is observed in solids and solutions. Ionic conduction is one mechanism of current.

An advanced superionic conductor (AdSIC) in materials science, is fast ion conductor that has a crystal structure close to optimal for fast ion transport (FIT).

Rubidium silver iodide is a ternary inorganic compound with the formula RbAg4I5. Its conductivity involves the movement of silver ions within the crystal lattice. It was discovered while searching for chemicals which had the ionic conductivity properties of alpha-phase silver iodide at temperatures below 146 °C for AgI.

<span class="mw-page-title-main">Yttria-stabilized zirconia</span> Ceramic with room temperature stable cubic crystal structure

Yttria-stabilized zirconia (YSZ) is a ceramic in which the cubic crystal structure of zirconium dioxide is made stable at room temperature by an addition of yttrium oxide. These oxides are commonly called "zirconia" (ZrO2) and "yttria" (Y2O3), hence the name.

<span class="mw-page-title-main">Solid state ionics</span>

Solid-state ionics is the study of ionic-electronic mixed conductor and fully ionic conductors and their uses. Some materials that fall into this category include inorganic crystalline and polycrystalline solids, ceramics, glasses, polymers, and composites. Solid-state ionic devices, such as solid oxide fuel cells, can be much more reliable and long-lasting, especially under harsh conditions, than comparable devices with fluid electrolytes.

<span class="mw-page-title-main">Solid-state battery</span> Battery with solid electrodes and a solid electrolyte

A solid-state battery is an electrical battery that uses a solid electrolyte for ionic conductions between the electrodes, instead of the liquid or gel polymer electrolytes found in conventional batteries. Solid-state batteries theoretically offer much higher energy density than the typical lithium-ion or lithium polymer batteries.

LISICON is an acronym for LIthiumSuper Ionic CONductor, which refers to a family of solids with the chemical formula Li2+2xZn1−xGeO4.

<span class="mw-page-title-main">NASICON</span> Class of solid materials

NASICON is an acronym for sodium (Na) super ionic conductor, which usually refers to a family of solids with the chemical formula Na1+xZr2SixP3−xO12, 0 < x < 3. In a broader sense, it is also used for similar compounds where Na, Zr and/or Si are replaced by isovalent elements. NASICON compounds have high ionic conductivities, on the order of 10−3 S/cm, which rival those of liquid electrolytes. They are caused by hopping of Na ions among interstitial sites of the NASICON crystal lattice.

<span class="mw-page-title-main">Mixed conductor</span>

Mixed conductors, also known as mixed ion-electron conductors(MIEC), are a single-phase material that has significant conduction ionically and electronically. Due to the mixed conduction, a formally neutral species can transport in a solid and therefore mass storage and redistribution are enabled. Mixed conductors are well known in conjugation with high-temperature superconductivity and are able to capacitate rapid solid-state reactions.

<span class="mw-page-title-main">Solid-state electrolyte</span> Type of solid ionic conductor electrolyte

A solid-state electrolyte (SSE) is a solid ionic conductor and electron-insulating material and it is the characteristic component of the solid-state battery. It is useful for applications in electrical energy storage (EES) in substitution of the liquid electrolytes found in particular in lithium-ion battery. The main advantages are the absolute safety, no issues of leakages of toxic organic solvents, low flammability, non-volatility, mechanical and thermal stability, easy processability, low self-discharge, higher achievable power density and cyclability. This makes possible, for example, the use of a lithium metal anode in a practical device, without the intrinsic limitations of a liquid electrolyte thanks to the property of lithium dendrite suppression in the presence of a solid-state electrolyte membrane. The use of a high capacity anode and low reduction potential, like lithium with a specific capacity of 3860 mAh g−1 and a reduction potential of -3.04 V vs SHE, in substitution of the traditional low capacity graphite, which exhibits a theoretical capacity of 372 mAh g−1 in its fully lithiated state of LiC6, is the first step in the realization of a lighter, thinner and cheaper rechargeable battery. Moreover, this allows the reach of gravimetric and volumetric energy densities, high enough to achieve 500 miles per single charge in an electric vehicle. Despite the promising advantages, there are still many limitations that are hindering the transition of SSEs from academia research to large-scale production, depending mainly on the poor ionic conductivity compared to that of liquid counterparts. However, many car OEMs (Toyota, BMW, Honda, Hyundai) expect to integrate these systems into viable devices and to commercialize solid-state battery-based electric vehicles by 2025.

Lithium lanthanum zirconium oxide (LLZO, Li7La3Zr2O12) or lithium lanthanum zirconate is a lithium-stuffed garnet material that is under investigation for its use in solid-state electrolytes in lithium-based battery technologies. LLZO has a high ionic conductivity and thermal and chemical stability against reactions with prospective electrode materials, mainly lithium metal, giving it an advantage for use as an electrolyte in solid-state batteries. LLZO exhibits favorable characteristics, including the accessibility of starting materials, cost-effectiveness, and straightforward preparation and densification processes. These attributes position this zirconium-containing lithium garnet as a promising solid electrolyte for all-solid-state lithium-ion rechargeable batteries.

A polymer electrolyte is a polymer matrix capable of ion conduction. Much like other types of electrolyte—liquid and solid-state—polymer electrolytes aid in movement of charge between the anode and cathode of a cell. The use of polymers as an electrolyte was first demonstrated using dye-sensitized solar cells. The field has expanded since and is now primarily focused on the development of polymer electrolytes with applications in batteries, fuel cells, and membranes.

<span class="mw-page-title-main">Lithium aluminium germanium phosphate</span> Chemical compound

Lithium aluminium germanium phosphate, typically known with the acronyms LAGP or LAGPO, is an inorganic ceramic solid material whose general formula is Li
1+xAl
xGe
2-x(PO
4)
3. LAGP belongs to the NASICON family of solid conductors and has been applied as a solid electrolyte in all-solid-state lithium-ion batteries. Typical values of ionic conductivity in LAGP at room temperature are in the range of 10–5 - 10–4 S/cm, even if the actual value of conductivity is strongly affected by stoichiometry, microstructure, and synthesis conditions. Compared to lithium aluminium titanium phosphate (LATP), which is another phosphate-based lithium solid conductor, the absence of titanium in LAGP improves its stability towards lithium metal. In addition, phosphate-based solid electrolytes have superior stability against moisture and oxygen compared to sulfide-based electrolytes like Li
10GeP
2S
12 (LGPS) and can be handled safely in air, thus simplifying the manufacture process. Since the best performances are encountered when the stoichiometric value of x is 0.5, the acronym LAGP usually indicates the particular composition of Li
1.5Al
0.5Ge
1.5(PO
4)
3, which is also the typically used material in battery applications.

<span class="mw-page-title-main">Venkataraman Thangadurai</span> Canadian Scientist

Venkataraman Thangadurai is a scientist recognized for his work in solid state ionics and chemistry. He is a professor at the University of Calgary, specializing in Chemistry.

References

  1. ↑ Akin, Mert; Wang, Yuchen; Qiao, Xiaoyao; Yan, Zhiwei; Zhou, Xiangyang (September 2020). "Effect of relative humidity on the reaction kinetics in rubidium silver iodide based all-solid-state battery". Electrochimica Acta. 355: 136779. doi:10.1016/j.electacta.2020.136779. S2CID   225553692.
  2. ↑ Wang, Yuchen; Akin, Mert; Qiao, Xiaoyao; Yan, Zhiwei; Zhou, Xiangyang (September 2021). "Greatly enhanced energy density of all‐solid‐state rechargeable battery operating in high humidity environments". International Journal of Energy Research. 45 (11): 16794–16805. doi: 10.1002/er.6928 .
  3. ↑ Stuhrmann C.H.J.; Kreiterling H.; Funke K. (2002). "Ionic Hall effect measured in rubidium silver iodide". Solid State Ionics. 154–155: 109–112. doi:10.1016/S0167-2738(02)00470-8.
  4. ↑ Александр Деспотули; Александра Андреева (2007). Высокоёмкие конденсаторы для 0,5 вольтовой наноэлектроники будущего. Современная Электроника (in Russian) (7): 24–29.Alexander Despotuli; Alexandra Andreeva (2007). "High-capacity capacitors for 0.5 voltage nanoelectronics of the future". Modern Electronics (7): 24–29.
  5. ↑ Despotuli, A.L.; Andreeva, A.V. (January 2009). "A Short Review on Deep-Sub-Voltage Nanoelectronics and Related Technologies". International Journal of Nanoscience. 8 (4&5): 389–402. Bibcode:2009IJN.....8..389D. doi:10.1142/S0219581X09006328.
  6. ↑ Bindi, L.; Evain M. (2006). "Fast ion conduction character and ionic phase-transitions in disordered crystals: the complex case of the minerals of the pearceite– polybasite group". Phys Chem Miner. 33 (10): 677–690. Bibcode:2006PCM....33..677B. doi:10.1007/s00269-006-0117-7. S2CID   95315848.
  7. ↑ Shriver, D. F.; Atkins, P. W.; Overton, T. L.; Rourke, J. P.; Weller, M. T.; Armstrong, F. A. “Inorganic Chemistry” W. H. Freeman, New York, 2006. ISBN   0-7167-4878-9.
  8. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  9. ↑ Akin, Mert; Wang, Yuchen; Qiao, Xiaoyao; Yan, Zhiwei; Zhou, Xiangyang (20 September 2020). "Effect of relative humidity on the reaction kinetics in rubidium silver iodide based all-solid-state battery". Electrochimica Acta. 355: 136779. doi:10.1016/j.electacta.2020.136779. S2CID   225553692.
  10. ↑ Matsumoto, Hiroshige; Miyake, Takako; Iwahara, Hiroyasu (2001-05-01). "Chloride ion conduction in PbCl2-PbO system". Materials Research Bulletin. 36 (7): 1177–1184. doi:10.1016/S0025-5408(01)00593-1. ISSN   0025-5408.
  11. ↑ "The Roll-to-Roll Battery Revolution". Ev World. Archived from the original on 2011-07-10. Retrieved 2010-08-20.
  12. ↑ Perzyna, K.; Borkowska, R.; Syzdek, J. A.; Zalewska, A.; Wieczorek, W. A. A. (2011). "The effect of additive of Lewis acid type on lithium–gel electrolyte characteristics". Electrochimica Acta. 57: 58–65. doi:10.1016/j.electacta.2011.06.014.
  13. ↑ Syzdek, J. A.; Armand, M.; Marcinek, M.; Zalewska, A.; Żukowska, G. Y.; Wieczorek, W. A. A. (2010). "Detailed studies on the fillers modification and their influence on composite, poly(oxyethylene)-based polymeric electrolytes". Electrochimica Acta. 55 (4): 1314. doi:10.1016/j.electacta.2009.04.025.
  14. ↑ Lehovec, Kurt (1953). "Space-charge layer and distribution of lattice defects at the surface of ionic crystals". Journal of Chemical Physics . 21 (7): 1123–1128. Bibcode:1953JChPh..21.1123L. doi: 10.1063/1.1699148 .
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.