Electrochemical window

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The electrochemical window (EW) of a substance is the electrode electric potential range between which the substance is neither oxidized nor reduced. The EW is one of the most important characteristics to be identified for solvents and electrolytes used in electrochemical applications. The EW is a term that is commonly used to indicate the potential range and the potential difference. It is calculated by subtracting the reduction potential (cathodic limit) from the oxidation potential (anodic limit). [1]

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When the substance of interest is water, it is often referred to as the water window.

This range is important for the efficiency of an electrode. Out of this range, the electrodes will react with the electrolyte, instead of driving the electrochemical reaction. [2]

In principle, ammonia has an extremely small electrochemical window, but thermodynamically-favored reactions less than 1 V outside the window are very slow. Consequently, the electrochemical window for many practical reactions is much larger, comparable to water. [3] Ionic liquids famously have a very large electrochemical window, about 4–5 V. [4]

The importance of electrochemical window (EW) in organic batteries

The electrochemical window (EW) is an important concept in organic electrosynthesis and design of batteries, especially organic batteries. [5] This is because at higher voltage (greater than 4.0 V) organic electrolytes decompose and interferes with the oxidation and reduction of the organic cathode/anode materials. For this reason, the best organic electrolytes should be characterized by a wider range of electrochemical window, i.e., greater than the working range of the battery cell voltage. [6] For example, the electrochemical window of Lithium bis- (trifluoromethanesulfonyl)imide, commercially known as LiTFSI is about 3.0 V because it can operate in the range of 1.9 -4.9 V. [7] On the other hand, for electrolytes that are characterized by narrow electrochemical window, they are prone to irreversible decomposition, [8] which in turn triggers the battery capacity decaying during subsequent battery cycling.

The electrochemical window of organic electrolyte depends on many factors that include temperature, molecular frontier orbitals such LUMO (Lowest Unoccupied Molecular Orbital) and HOMO (Highest occupied Molecular Orbital) because the mechanisms of reduction (electron gaining) and oxidation (electron loss) are governed by band gap between HOMO and LUMO. [9] Solvation energy also plays an important role in defining the electrochemical window of the electrolyte. [10]

In order to safeguard the thermodynamic stability working conditions of the electrode materials in a given electrolyte, the electrochemical potentials of the electrode materials (anode and cathode) must be comprised within the electrochemical stability of the electrolyte. [11] This condition is very succinct because electrolyte might be oxidized when the cathode material possess an electrochemical potential, which is less than the electrolyte oxidation potential. When the electrochemical potential of the anode material is quite higher than the reduction potential of the electrolyte, the electrolyte will be degraded through reduction process. [12] [13]

Limitation of Electrochemical window

One of the shortcoming of electrochemical window (EW) in predicting the stability of the electrolyte towards anode or cathode materials ignores the voltage and the ionic conductivity, which are also important. [14]

Related Research Articles

<span class="mw-page-title-main">Electrochemistry</span> Branch of chemistry

Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change. These reactions involve electrons moving via an electronically conducting phase between electrodes separated by an ionically conducting and electronically insulating electrolyte.

<span class="mw-page-title-main">Electrochemical cell</span> Electro-chemical device

An electrochemical cell is a device that generates electrical energy from chemical reactions. Electrical energy can also be applied to these cells to cause chemical reactions to occur. Electrochemical cells that generate an electric current are called voltaic or galvanic cells and those that generate chemical reactions, via electrolysis for example, are called electrolytic cells.

<span class="mw-page-title-main">Lithium-ion battery</span> Rechargeable battery type

A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible intercalation of Li+ ions into electronically conducting solids to store energy. In comparison with other commercial rechargeable batteries, Li-ion batteries are characterized by higher specific energy, higher energy density, higher energy efficiency, a longer cycle life, and a longer calendar life. Also noteworthy is a dramatic improvement in lithium-ion battery properties after their market introduction in 1991: over the following 30 years, their volumetric energy density increased threefold while their cost dropped tenfold.

A polymer-based battery uses organic materials instead of bulk metals to form a battery. Currently accepted metal-based batteries pose many challenges due to limited resources, negative environmental impact, and the approaching limit of progress. Redox active polymers are attractive options for electrodes in batteries due to their synthetic availability, high-capacity, flexibility, light weight, low cost, and low toxicity. Recent studies have explored how to increase efficiency and reduce challenges to push polymeric active materials further towards practicality in batteries. Many types of polymers are being explored, including conductive, non-conductive, and radical polymers. Batteries with a combination of electrodes are easier to test and compare to current metal-based batteries, however batteries with both a polymer cathode and anode are also a current research focus. Polymer-based batteries, including metal/polymer electrode combinations, should be distinguished from metal-polymer batteries, such as a lithium polymer battery, which most often involve a polymeric electrolyte, as opposed to polymeric active materials.

<span class="mw-page-title-main">Lithium-ion capacitor</span> Hybrid type of capacitor

A lithium-ion capacitor is a hybrid type of capacitor classified as a type of supercapacitor. It is called a hybrid because the anode is the same as those used in lithium-ion batteries and the cathode is the same as those used in supercapacitors. Activated carbon is typically used as the cathode. The anode of the LIC consists of carbon material which is often pre-doped with lithium ions. This pre-doping process lowers the potential of the anode and allows a relatively high output voltage compared to other supercapacitors.

<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.

The lithium–air battery (Li–air) is a metal–air electrochemical cell or battery chemistry that uses oxidation of lithium at the anode and reduction of oxygen at the cathode to induce a current flow.

A metal–air electrochemical cell is an electrochemical cell that uses an anode made from pure metal and an external cathode of ambient air, typically with an aqueous or aprotic electrolyte.

A potassium-ion battery or K-ion battery is a type of battery and analogue to lithium-ion batteries, using potassium ions for charge transfer instead of lithium ions.

Aluminium-ion batteries are a class of rechargeable battery in which aluminium ions serve as charge carriers. Aluminium can exchange three electrons per ion. This means that insertion of one Al3+ is equivalent to three Li+ ions. Thus, since the ionic radii of Al3+ (0.54 Å) and Li+ (0.76 Å) are similar, significantly higher numbers of electrons and Al3+ ions can be accepted by cathodes with little damage. Al has 50 times (23.5 megawatt-hours m-3) the energy density of Li and is even higher than coal.

Research in lithium-ion batteries has produced many proposed refinements of lithium-ion batteries. Areas of research interest have focused on improving energy density, safety, rate capability, cycle durability, flexibility, and reducing cost.

<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.

Magnesium batteries are batteries that utilize magnesium cations as charge carriers and possibly in the anode in electrochemical cells. Both non-rechargeable primary cell and rechargeable secondary cell chemistries have been investigated. Magnesium primary cell batteries have been commercialised and have found use as reserve and general use batteries.

A zinc-ion battery or Zn-ion battery (abbreviated as ZIB) uses zinc ions (Zn2+) as the charge carriers. Specifically, ZIBs utilize Zn metal as the anode, Zn-intercalating materials as the cathode, and a Zn-containing electrolyte. Generally, the term zinc-ion battery is reserved for rechargeable (secondary) batteries, which are sometimes also referred to as rechargeable zinc metal batteries (RZMB). Thus, ZIBs are different than non-rechargeable (primary) batteries which use zinc, such as alkaline or zinc–carbon batteries.

Calcium (ion) batteries are energy storage and delivery technologies (i.e., electro–chemical energy storage) that employ calcium ions (cations), Ca2+, as the active charge carrier. Calcium (ion) batteries remain an active area of research, with studies and work persisting in the discovery and development of electrodes and electrolytes that enable stable, long-term battery operation. Calcium batteries are rapidly emerging as a recognized alternative to Li-ion technology due to their similar performance, significantly greater abundance, and lower cost.

<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.

<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">History of the lithium-ion battery</span> Overview of the events of the development of lithium-ion battery

This is a history of the lithium-ion battery.

Fluoride batteries are a rechargeable battery technology based on the shuttle of fluoride, the anion of fluorine, as ionic charge carriers.

Superconcentrated electrolytes, also known as water-in-salt or solvent-in-salt liquids, usually refer to chemical systems, which are liquid near room temperature and consist of a solvent-to-dissoved salt in a molar ratio near or smaller than ca. 4-8, i.e. where all solvent molecules are coordinated to cations, and no free solvent molecules remain. Since ca. 2010 such liquid electrolytes found several applications, primarily for batteries. In the case of lithium metal batteries and lithium-ion batteries most commonly used anions for superconcentrated electrolytes are those, that are large, asymmetric and rotationally-vibrationally flexible, such as bis(trifluoromethanesulfonyl)amide and bis(fluorosulfonyl)amide. Noteworthy, lithium chloride and sodium perchlorate also form water-in-salt solutions.

References

  1. ↑ Maan Hayyan; Farouq S. Mjalli; Mohd Ali Hashim; Inas M. AlNashef (2013). "Investigating the Electrochemical Windows of Ionic Liquids". Journal of Industrial and Engineering Chemistry. 19: 106–112. doi:10.1016/j.jiec.2012.07.011.
  2. ↑ Huggins, Robert (2010). Advanced batteries : materials science aspects. Springer. p. 375. ISBN   978-0-387-76423-8. OCLC   760155429.
  3. ↑ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 488. ISBN   978-0-08-022057-4.
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  5. ↑ Leech, Matthew C.; Lam, Kevin (April 2022). "A practical guide to electrosynthesis". Nature Reviews Chemistry. 6 (4): 275–286. doi:10.1038/s41570-022-00372-y. ISSN   2397-3358. PMID   37117870. S2CID   247585645.
  6. ↑ Li, Mengjie; Hicks, Robert Paul; Chen, Zifeng; Luo, Chao; Guo, Juchen; Wang, Chunsheng; Xu, Yunhua (2023-02-22). "Electrolytes in Organic Batteries". Chemical Reviews. 123 (4): 1712–1773. doi:10.1021/acs.chemrev.2c00374. ISSN   0009-2665. PMID   36735935. S2CID   256577160.
  7. ↑ Suo, Liumin; Borodin, Oleg; Gao, Tao; Olguin, Marco; Ho, Janet; Fan, Xiulin; Luo, Chao; Wang, Chunsheng; Xu, Kang (2015-11-20). ""Water-in-salt" electrolyte enables high-voltage aqueous lithium-ion chemistries". Science. 350 (6263): 938–943. doi:10.1126/science.aab1595. ISSN   0036-8075.
  8. ↑ Li, Chenghan; Zhou, Shi; Dai, Lijie; Zhou, Xuanyi; Zhang, Biao; Chen, Liwen; Zeng, Tao; Liu, Yating; Tang, Yongfu; Jiang, Jie; Huang, Jianyu (2021-11-09). "Porous polyamine/PEO composite solid electrolyte for high performance solid-state lithium metal batteries". Journal of Materials Chemistry A. 9 (43): 24661–24669. doi:10.1039/D1TA04599G. ISSN   2050-7496. S2CID   240888672.
  9. ↑ Marchiori, Cleber F. N.; Carvalho, Rodrigo P.; Ebadi, Mahsa; Brandell, Daniel; Araujo, C. Moyses (2020-09-08). "Understanding the Electrochemical Stability Window of Polymer Electrolytes in Solid-State Batteries from Atomic-Scale Modeling: The Role of Li-Ion Salts". Chemistry of Materials. 32 (17): 7237–7246. doi:10.1021/acs.chemmater.0c01489. ISSN   0897-4756. S2CID   225384562.
  10. ↑ Wang, Da; He, Tingting; Wang, Aiping; Guo, Kai; Avdeev, Maxim; Ouyang, Chuying; Chen, Liquan; Shi, Siqi (March 2023). "A Thermodynamic Cycle-Based Electrochemical Windows Database of 308 Electrolyte Solvents for Rechargeable Batteries". Advanced Functional Materials. 33 (11). doi:10.1002/adfm.202212342. ISSN   1616-301X. S2CID   255457966.
  11. ↑ Marchiori, Cleber F. N.; Carvalho, Rodrigo P.; Ebadi, Mahsa; Brandell, Daniel; Araujo, C. Moyses (2020-09-08). "Understanding the Electrochemical Stability Window of Polymer Electrolytes in Solid-State Batteries from Atomic-Scale Modeling: The Role of Li-Ion Salts". Chemistry of Materials. 32 (17): 7237–7246. doi:10.1021/acs.chemmater.0c01489. ISSN   0897-4756. S2CID   225384562.
  12. ↑ Sekhar Manna, Surya; Bhauriyal, Preeti; Pathak, Biswarup (2020). "Identifying suitable ionic liquid electrolytes for Al dual-ion batteries: role of electrochemical window, conductivity and voltage". Materials Advances. 1 (5): 1354–1363. doi: 10.1039/D0MA00292E . S2CID   221802258.
  13. ↑ Kalisa, Nyirimbibi Daniela; Muhizi, Theonestea; Niyotwizera, Jean Jacques Yvesa; Barutwanayo, Jean Baptistea; Nkuranga, Jean Boscoa (2020-05-08). "Kinetics and Thermodynamics Investigations on Corrosion Inhibiting Properties of Coffee Husks Extract on Mild Steel in Acidic Medium". Rwanda Journal of Engineering, Science, Technology and Environment. 3 (1). doi: 10.4314/rjeste.v3i1.10 . ISSN   2617-233X.
  14. ↑ Sekhar Manna, Surya; Bhauriyal, Preeti; Pathak, Biswarup (2020). "Identifying suitable ionic liquid electrolytes for Al dual-ion batteries: role of electrochemical window, conductivity and voltage". Materials Advances. 1 (5): 1354–1363. doi: 10.1039/D0MA00292E . S2CID   221802258.
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