Liquid metal battery

A liquid metal battery is an electrochemical energy storage, the anode , cathode and electrolyte during operation in the liquid aggregate state is. For operation, comparatively high temperatures are necessary so that the individual materials are in liquid form, which requires appropriate thermal insulation from the environment. These batteries are thermal batteries . Liquid metal batteries are being discussed as stationary electrical energy storage devices for strongly fluctuating renewable energies .

Structure and functionality

Basic sketch of a liquid metal battery with Na anode and Bi cathode

Liquid metal batteries are characterized by a completely liquid inventory. A heavy metal acts as a cathode, a light metal acts as an anode. Both metals are separated from each other by a thin molten salt, the electrolyte. If the active materials are selected appropriately according to their density, the three phases “float” on top of each other. One of the best-known cells is the Na | NaCl-NaF-NaI | Bi cell. It uses sodium as the anode, bismuth as the cathode, and a mixture of several sodium salts as the electrolyte.

During the discharge, the sodium gives off an electron

{\ displaystyle \ mathrm {Na} \ longrightarrow \ mathrm {Na} ^ {+} + \ mathrm {e} ^ {-}}

and diffuses as an ion through the electrolyte layer, where it alloys with bismuth:

{\ displaystyle \ mathrm {Na} ^ {+} + \ mathrm {e} ^ {-} \ longrightarrow \ mathrm {Na} (\ mathrm {Bi})}

.

Sodium is in the same oxidation state in the anode as in the cathode. Therefore it is not a design like the historical Daniell elements or the Gravity-Daniell elements , which also work with density differences , but a concentration cell. The theoretical cell voltage, with the Nernst equation to

{\ displaystyle U = - {\ frac {RT} {zF}} \ ln a _ {\ mathrm {Na} (\ mathrm {Bi})}}

to be determined.

Advantages and disadvantages

The main advantages of the liquid metal battery are:

low price of active materials
easy construction
extremely high current density (up to 130 kA / m²)
high theoretical service life (no electrode degradation)
easy scalability

The main disadvantages are:

Position dependency and thus no or very limited applicability in mobile applications
low cell voltage (less than 1 V)
high working temperature and the associated limitations.
unknown flow behavior in completely liquid batteries

proof

↑ ^a ^b C. Crouthamel, H. Recht (Ed.): Regenerative EMF Cells . Vol. 64. American Chemical Society, 1967.
^ ^A ^b EJ Cairns, CE Crouthamel, AK Fischer, MS Foster, JC Hesson, CE Johnson, H. Shimotake, AD Tevebaugh: Galvanic Cells with Fused-Salt Electrolytes . Argonne National Laboratory, 1967 (ANL-7316).
↑ ^a ^b ^c Hojong Kim et al: Liquid Metal Batteries: Past, Present, and Future . In: Chemical Reviews . tape 113 , no. 3 , March 13, 2013, p. 2075-2099 , doi : 10.1021 / cr300205k .
↑ ^a ^b DJ Bradwell: Liquid Metal Batteries: Ambipolar Electrolysis and Alkaline Earth Electroalloying Cells . Massachusetts Institute of Technology, Dissertation, 2011.
↑ Norbert Weber, Vladimir Galindo, Frank Stefani, Tom Weier: Current-driven flow instabilities in large-scale liquid metal batteries, and how to tame them . In: Journal of Power Sources . tape 265 , November 1, 2014, p. 166-173 , doi : 10.1016 / j.jpowsour.2014.03.055 .
↑ Kangli Wang et al: Lithium-antimony-lead liquid metal battery for grid-level energy storage . In: Nature . tape 514 , no. 7522 , October 16, 2014, p. 348-350 , doi : 10.1038 / nature13700 .
^ DAJ Swinkels: Molten Salt Batteries and Fuel Cells . In: J. Braunstein, G. Mamantov, GP Smith (eds.): Advances in Molten Salt Chemistry Vol. 1, Plenum Press, New York 1971, chap. 4, pp. 165-223.

[Crouthamel1967-1] C. Crouthamel, H. Recht (Ed.): Regenerative EMF Cells . Vol. 64. American Chemical Society, 1967.

[Cairns1967-2] A ^b EJ Cairns, CE Crouthamel, AK Fischer, MS Foster, JC Hesson, CE Johnson, H. Shimotake, AD Tevebaugh: Galvanic Cells with Fused-Salt Electrolytes . Argonne National Laboratory, 1967 (ANL-7316).

[Kim2013a-3] Hojong Kim et al: Liquid Metal Batteries: Past, Present, and Future . In: Chemical Reviews . tape 113 , no. 3 , March 13, 2013, p. 2075-2099 , doi : 10.1021 / cr300205k .

[Bradwell2011-4] DJ Bradwell: Liquid Metal Batteries: Ambipolar Electrolysis and Alkaline Earth Electroalloying Cells . Massachusetts Institute of Technology, Dissertation, 2011.

[Weber2014b-5] Norbert Weber, Vladimir Galindo, Frank Stefani, Tom Weier: Current-driven flow instabilities in large-scale liquid metal batteries, and how to tame them . In: Journal of Power Sources . tape 265 , November 1, 2014, p. 166-173 , doi : 10.1016 / j.jpowsour.2014.03.055 .

[Wang2014-6] Kangli Wang et al: Lithium-antimony-lead liquid metal battery for grid-level energy storage . In: Nature . tape 514 , no. 7522 , October 16, 2014, p. 348-350 , doi : 10.1038 / nature13700 .

[Swinkels1971-7] DAJ Swinkels: Molten Salt Batteries and Fuel Cells . In: J. Braunstein, G. Mamantov, GP Smith (eds.): Advances in Molten Salt Chemistry Vol. 1, Plenum Press, New York 1971, chap. 4, pp. 165-223.