Fluoride battery
Specific energyup to ~800 mAh/g
Energy densityup to ~4800 Wh/L
Cycle durabilityUnknown (no commercial available devices)
Nominal cell voltage1.5 - 5.0 V (Depends on electrode materials)

Fluoride-ion batteries (fluoride batteries and fluoride shuttle batteries) are rechargeable battery technology based on the shuttle of fluoride ions as ionic charge carriers.

This kind of chemistry is attracted interest in the mid-2010s because of its environmental friendliness, due to the avoidance of scarce an geographically strained mineral resources in electrodes composition (e.g. cobalt and nickel) and high theoretical energy densities. In addition, since there is no metal plating and stripping, dendrites formation is negligible also if high-capacity metallic anodes are used, with increased safety, cyclability and energy storage capacity. Theoretically, a FB using a low costs electrodes and a liquid electrolyte can have energy densities as high as ~800 mAh/g and ~4800 Wh/L.[1]

The fluoride-ion based technology is in early-stage of development and, as of 2023, there are no commercially available devices. The main issues limiting actual performances are the high reactivity of naked fluoride in liquid electrolytes, low fluoride-ion ionic conductivity of solid-state electrolytes at room temperature and volume expansion of conversion-type electrodes that put mechanical strain on cell components during charging-discharging cycling leading to a premature capacity fading. Despite the aforementioned limitations, the fluoride-ion based technology represents a candidate for the next generation of electrochemical storage technology.[1]

History

Fluoride-ion shuttling was proposed in 1974. while working on fluoride ionic conductivity of CaF2 at temperatures ranging from 400 to 500 °C.[2]

Research continued between 70s and early 80s when other studies about fluoride conductivity of inorganic fluorides at high temperature were carried out, one of the practical application was made [3] in 1976 doping β-PbF2 with potassium fluoride. When employed in a galvanic cell as a solid-state electrolyte this material allow reaching open-circuit voltage close to theoretical ones, but failed to sustain a current when a load was applied.

Little advancements were made in the field of fluoride-ion shuttling later in the 1980s, with only few studies reported working cells using solid-state fluoride conductive materials based on lanthanum, lead or cerium fluoride with unsatisfactory discharge capacity, if compared to commercially available batteries, high working temperature (up to 160 °C) and limited cell life.[4]

True trends for FBs started to drawing attention from mid-2010s, driven by energy transition and needs of new energy storage devices. Improvement were made in both solid[5][6][7][8] and liquid electrolytes.[9][10]

Working principle

The fluoride batteries chemistry rely on reversible electrochemical fluorination of a electropositive metal (M') at the anode side, at the expenses of a more noble metal fluoride (MFx) at the cathode side.[1]

Discharge process

At Cathode (+)

At Anode (-)

Charge process

At Cathode (-)

At Anode (+)

Electrodes

Conversion-type electrodes

In conversion-type electrodes the redox reaction that occur change the crystal structure of material itself, this process often lead to a big variation of particles volume that can loss contanct with current collector or aggregate and loss active surface area, causing capacity fading. An advantage of converion-type electrodes is the possibility to exploit more than one electron transfer per redox center, increasing the specific capacity.[11]

This class include some simple metal and transition metal fluorides, that can exchange two or more electrons per mole, like BiF3,[9][12] Bi0.8Ba0.2F2.8,[13] PbF2,[14] FeF3,[15] CuF2,[16] KBiF3[6] at the cathode side or Ca and Mg at the anode side.[1]

Intercalation-type

In intercalation-type electrodes, fluoride ions can be inserted in a vacancy in the crystal lattice of the electrode material, without changing its structure. In this case, the volume variation is greatly reduced making these materials more stable. In contrast, the electron transfer per redox center is usually limited to one, reducing the available specific capacity.[11]

Electrolytes

Liquid electrolytes

Liquid electrolytes for FBs would offer a solution to the problem arising from the volumetric expansion of electrodes and at the same time to the reduction of operating temperature, due to intrinsic higher ion mobility, which results in high ion conductivity.

Inorganic fluorides-based electrolytes

Inorganic-based liquid electrolytes are made by dissolving alkali metal fluorides in an organic aprotic solvent but the low solubility of inorganic fluorides in common battery electrolytes solvents leads to poor ionic conductivity.[9]

To enhance salts solubility, and consequently, ionic conductivity, boron-based anion acceptors were used to increase salt solubility in organics, as an example, an electrolyte based on cesium fluoride dissolved in tetraglyme with different anion acceptors, including triphenylboroxines and triphenylboranes[17][18] were discovered.

Organic fluorides-based electrolytes

Organic-based liquid electrolytes were developed by dissolving tetraalkylammonium salts in proper organic aprotic solvents. The main issue is the high nucleophilic behavior of unsolved fluoride-ion that react easily with β-hydrogen of alkyl groups via the Hofmann elimination mechanism.[19]

To obtain a stable organic-based electrolyte, ammonium salts without β-hydrogen was employed and tested N,N,N-trimethyl-N-neopentylammonium fluoride dissolved at high concentration in a partially fluorinated ether.[20]

Solid electrolytes

Despite the intrinsic challenges of materials, in fact, most fluoride-conducting materials achieve insufficient ionic conductivity even at high temperatures (up to 160 °C) that limit the possibility of commercial use. Moreover, the stiffness of these materials doesn't cope with the high volumetric expansion of conversion cathodes.[21]

Tysonite-type rare-earth fluorides

Rare-earth fluorides with tysonite-type structure (RE1-xMxF3-x where RE is a rare-earth among La, Ce, Sm, and M is a second group metal like Ba, Ca, or Sr) has studied, because of their wide electrochemical stability windows, up to 4 V vs Li+/Li.

As an example, in 2017, it was synthesized, with a ball milling technique, barium-doped lanthanum fluoride (LBF), reaching an ionic conductivity of around 10−5 S cm−1 at room temperature[22] but still lower than conventional liquid electrolytes used in commercially available Li-ion batteries. Similar results in terms of ionic conductivity were achieved with cerium fluoride doped with strontium fluoride or calcium-doped samarium fluoride.[23][24]

Alkaline-earth fluorides

Among alkaline-earth fluorides, barium-tin fluoride (BaSnF4) has investigated because of its relatively high ionic conductivity at room temperature, in the order of 10−4 S cm−1. Despite the increased ionic conductivity, the low electrochemical stability window of Sn2+ prevents the use of reducing metals as anodes, decreasing the maximum cell potential, and consequently, the energy density.[7]

In 2019 researchers obtained rechargable FB with a BaSnF4 solid electrolyte covered with an interlayer of LBF extending the electrochemical stability windows of BaSnF4.[25]

See also

References

  1. 1 2 3 4 Gschwind, F.; Rodriguez-Garcia, G.; Sandbeck, D.J.S.; Gross, A.; Weil, M.; Fichtner, M.; Hörmann, N. (February 2016). "Fluoride ion batteries: Theoretical performance, safety, toxicity, and a combinatorial screening of new electrodes". Journal of Fluorine Chemistry. 182: 76–90. doi:10.1016/j.jfluchem.2015.12.002.
  2. ↑ Baukal, W. (1974-11-01). "Über reaktionsmöglichkeiten in elektroden von festkörperbatterien". Electrochimica Acta (in German). 19 (11): 687–694. doi:10.1016/0013-4686(74)80011-3. ISSN 0013-4686.
  3. ↑ Kennedy, John H.; Miles, Ronald C. (1976-01-01). "Ionic Conductivity of Doped Beta‐Lead Fluoride". Journal of the Electrochemical Society. 123 (1): 47–51. Bibcode:1976JElS..123...47K. doi:10.1149/1.2132763. ISSN 0013-4651.
  4. ↑ Schoonman, J.; Wapenaar, K. E. D.; Oversluizen, G.; Dirksen, G. J. (1979-05-01). "Fluoride‐Conducting Solid Electrolytes in Galvanic Cells". Journal of the Electrochemical Society. 126 (5): 709–713. Bibcode:1979JElS..126..709S. doi:10.1149/1.2129125. ISSN 0013-4651.
  5. ↑ Rongeat, Carine; Anji Reddy, M.; Witter, Raiker; Fichtner, Maximilian (2014-02-12). "Solid Electrolytes for Fluoride Ion Batteries: Ionic Conductivity in Polycrystalline Tysonite-Type Fluorides". ACS Applied Materials & Interfaces. 6 (3): 2103–2110. doi:10.1021/am4052188. ISSN 1944-8244. PMID 24444763.
  6. 1 2 Anji Reddy, M.; Fichtner, M. (2011). "Batteries based on fluoride shuttle". Journal of Materials Chemistry. 21 (43): 17059. doi:10.1039/c1jm13535j. ISSN 0959-9428.
  7. 1 2 Mohammad, Irshad; Witter, Raiker; Fichtner, Maximilian; Anji Reddy, M. (2018-09-24). "Room-Temperature, Rechargeable Solid-State Fluoride-Ion Batteries". ACS Applied Energy Materials. 1 (9): 4766–4775. doi:10.1021/acsaem.8b00864. ISSN 2574-0962. S2CID 104555159.
  8. ↑ Liu, Lei; Yang, Li; Shao, Dingsheng; Luo, Kaili; Zou, Changfei; Luo, Zhigao; Wang, Xianyou (2020-08-15). "Nd3+ doped BaSnF4 solid electrolyte for advanced room-temperature solid-state fluoride ion batteries". Ceramics International. 46 (12): 20521–20528. doi:10.1016/j.ceramint.2020.05.161. ISSN 0272-8842. S2CID 219450100.
  9. 1 2 3 Konishi, Hiroaki; Minato, Taketoshi; Abe, Takeshi; Ogumi, Zempachi (2017). "Electrochemical Performance of a Bismuth Fluoride Electrode in a Reserve-Type Fluoride Shuttle Battery". Journal of the Electrochemical Society. 164 (14): A3702–A3708. doi:10.1149/2.0931714jes. ISSN 0013-4651.
  10. ↑ Minato, Taketoshi; Umeda, Kenichi; Kobayashi, Kei; Araki, Yuki; Konishi, Hiroaki; Ogumi, Zempachi; Abe, Takeshi; Onishi, Hiroshi; Yamada, Hirofumi (2021-09-01). "Atomic-level nature of solid/liquid interface for energy conversion revealed by frequency modulation atomic force microscopy". Japanese Journal of Applied Physics. 60 (SE): SE0806. doi:10.35848/1347-4065/abffa2. ISSN 0021-4922. S2CID 235817341.
  11. 1 2 Nowroozi, Mohammad Ali; Mohammad, Irshad; Molaiyan, Palanivel; Wissel, Kerstin; Munnangi, Anji Reddy; Clemens, Oliver (2021). "Fluoride ion batteries – past, present, and future". Journal of Materials Chemistry A. 9 (10): 5980–6012. doi:10.1039/D0TA11656D. ISSN 2050-7488. S2CID 233961245.
  12. ↑ Konishi, Hiroaki; Minato, Taketoshi; Abe, Takeshi; Ogumi, Zempachi (2019-04-25). "Influence of Electrolyte Composition on the Electrochemical Reaction Mechanism of Bismuth Fluoride Electrode in Fluoride Shuttle Battery". The Journal of Physical Chemistry C. 123 (16): 10246–10252. doi:10.1021/acs.jpcc.9b00455. hdl:2433/243871. ISSN 1932-7447. S2CID 146057087.
  13. ↑ Shimoda, Keiji; Minato, Taketoshi; Konishi, Hiroaki; Kano, Gentaro; Nakatani, Tomotaka; Fujinami, So; Celik Kucuk, Asuman; Kawaguchi, Shogo; Ogumi, Zempachi; Abe, Takeshi (August 2021). "Defluorination/fluorination mechanism of Bi0.8Ba0.2F2.8 as a fluoride shuttle battery positive electrode". Journal of Electroanalytical Chemistry. 895: 115508. doi:10.1016/j.jelechem.2021.115508. hdl:2433/269542. S2CID 237722139.
  14. ↑ Konishi, Hiroaki; Minato, Taketoshi; Abe, Takeshi; Ogumi, Zempachi (March 2019). "Electrochemical performance of a lead fluoride electrode mixed with carbon in an electrolyte containing triphenylboroxine as an anion acceptor for fluoride shuttle batteries". Materials Chemistry and Physics. 226: 1–5. doi:10.1016/j.matchemphys.2019.01.006. hdl:2433/243334. S2CID 104452152.
  15. ↑ Inoishi, Atsushi; Setoguchi, Naoko; Hori, Hironobu; Kobayashi, Eiichi; Sakamoto, Ryo; Sakaebe, Hikari; Okada, Shigeto (December 2021). "FeF 3 as Reversible Cathode for All‐Solid‐State Fluoride Batteries". Advanced Energy and Sustainability Research. 3 (12): 2200131. doi:10.1002/aesr.202200131. ISSN 2699-9412. S2CID 252770085.
  16. ↑ Mohammad, Irshad; Witter, Raiker (2019-06-01). "Testing Mg as an anode against BiF3 and SnF2 cathodes for room temperature rechargeable fluoride ion batteries". Materials Letters. 244: 159–162. doi:10.1016/j.matlet.2019.02.052. ISSN 0167-577X. S2CID 104470455.
  17. ↑ Konishi, Hiroaki; Minato, Taketoshi; Abe, Takeshi; Ogumi, Zempachi (2018-11-05). "Triphenylboroxine and Triphenylborane as Anion Acceptors for Electrolyte in Fluoride Shuttle Batteries". Chemistry Letters. 47 (11): 1346–1349. doi:10.1246/cl.180573. hdl:2433/243767. ISSN 0366-7022. S2CID 105752095.
  18. ↑ Konishi, Hiroaki; Takekawa, Reiji; Minato, Taketoshi; Ogumi, Zempachi; Abe, Takeshi (2020-09-16). "Effect of anion acceptor added to the electrolyte on the electrochemical performance of bismuth(III) fluoride in a fluoride shuttle battery". Chemical Physics Letters. 755: 137785. Bibcode:2020CPL...75537785K. doi:10.1016/j.cplett.2020.137785. ISSN 0009-2614. S2CID 224884471.
  19. ↑ Cox, D. Phillip; Terpinski, Jacek; Lawrynowicz, Witold (August 1984). ""Anhydrous" tetrabutylammonium fluoride: a mild but highly efficient source of nucleophilic fluoride ion". The Journal of Organic Chemistry. 49 (17): 3216–3219. doi:10.1021/jo00191a035. ISSN 0022-3263.
  20. ↑ Davis, Victoria K.; Bates, Christopher M.; Omichi, Kaoru; Savoie, Brett M.; Momčilović, Nebojša; Xu, Qingmin; Wolf, William J.; Webb, Michael A.; Billings, Keith J.; Chou, Nam Hawn; Alayoglu, Selim; McKenney, Ryan K.; Darolles, Isabelle M.; Nair, Nanditha G.; Hightower, Adrian (2018-12-07). "Room-temperature cycling of metal fluoride electrodes: Liquid electrolytes for high-energy fluoride ion cells". Science. 362 (6419): 1144–1148. Bibcode:2018Sci...362.1144D. doi:10.1126/science.aat7070. ISSN 0036-8075. PMID 30523107. S2CID 54456959.
  21. ↑ Zhang, Z.; Wang, X.; Li, X.; Zhao, J.; Liu, G.; Yu, W.; Dong, X.; Wang, J. (2023-03-01). "Review on composite solid electrolytes for solid-state lithium-ion batteries". Materials Today Sustainability. 21: 100316. doi:10.1016/j.mtsust.2023.100316. ISSN 2589-2347. S2CID 255721150.
  22. ↑ Chable, J.; Martin, A. G.; Bourdin, A.; Body, M.; Legein, C.; Jouanneaux, A.; Crosnier-Lopez, M. -P.; Galven, C.; Dieudonné, B.; Leblanc, M.; Demourgues, A.; Maisonneuve, V. (2017-01-25). "Fluoride solid electrolytes: From microcrystalline to nanostructured tysonite-type La0.95Ba0.05F2.95". Journal of Alloys and Compounds. 692: 980–988. doi:10.1016/j.jallcom.2016.09.135. ISSN 0925-8388.
  23. ↑ Dieudonné, Belto; Chable, Johann; Body, Monique; Legein, Christophe; Durand, Etienne; Mauvy, Fabrice; Fourcade, Sébastien; Leblanc, Marc; Maisonneuve, Vincent; Demourgues, Alain (2017). "The key role of the composition and structural features in fluoride ion conductivity in tysonite Ce 1−x Sr x F 3−x solid solutions". Dalton Transactions. 46 (11): 3761–3769. doi:10.1039/C6DT04714A. ISSN 1477-9226. PMID 28262874.
  24. ↑ Dieudonné, Belto; Chable, Johann; Mauvy, Fabrice; Fourcade, Sebastien; Durand, Etienne; Lebraud, Eric; Leblanc, Marc; Legein, Christophe; Body, Monique; Maisonneuve, Vincent; Demourgues, Alain (2015-10-30). "Exploring the Sm1–xCaxF3–x Tysonite Solid Solution as a Solid-State Electrolyte: Relationships between Structural Features and F– Ionic Conductivity". The Journal of Physical Chemistry C. 119 (45): 25170–25179. doi:10.1021/acs.jpcc.5b05016. ISSN 1932-7447.
  25. ↑ Mohammad, Irshad; Witter, Raiker; Fichtner, Maximilian; Reddy, M. Anji (2019-02-25). "Introducing Interlayer Electrolytes: Toward Room-Temperature High-Potential Solid-State Rechargeable Fluoride Ion Batteries". ACS Applied Energy Materials. 2 (2): 1553–1562. doi:10.1021/acsaem.8b02166. ISSN 2574-0962. S2CID 104454848.
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