Glass battery

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The Glass battery is a type of solid state battery. It uses a glass electrolyte and lithium or sodium metal electrodes.

Video Glass battery

Publication

The battery was invented by John B. Goodenough, inventor of the lithium cobalt oxide and lithium iron phosphate electrode materials used in the lithium-ion (Li-ion) battery, and Maria H. Braga, a senior research fellow at Cockrell School of Engineering at The University of Texas. The paper describing the battery was published in Energy and Environmental Science in December 2016.

Maps Glass battery

Construction and electrochemistry

The battery, as reported in the original publication, is constructed using an alkali metal (lithium or sodium foil) as the negative electrode (anode), and a mixture of carbon and a redox active component, as the positive electrode (cathode). The cathode mixture is coated onto copper foil. The redox active component is either sulfur, ferrocene, or manganese dioxide. The electrolyte is a highly conductive glass formed from lithium hydroxide and lithium chloride and doped with barium, allowing fast charging of the battery without the formation of metal dendrites.

The publication states that the battery operates during discharge by stripping the alkali metal from the anode and re-depositing it at the cathode, with the battery voltage determined by the redox active component and the capacity of the battery determined by the amount of the alkali metal anode. This operating mechanism is radically different from the insertion (intercalation) mechanism of most conventional Li-ion battery materials.

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Comparison with lithium-ion batteries

Braga and Goodenough have stated that they expect the battery to have an energy density many times higher than that of current lithium-ion batteries, as well as an operating temperature range down to -20 °C (-4 °F); much lower than current solid-state batteries. The electrolyte is also stated to have a wide electrochemical window. The battery's design is safer than lithium-ion batteries, as the use of a flammable liquid electrolyte is avoided. The battery can also be made using low-cost sodium instead of lithium.

The battery has a much shorter charging time than Li-ion batteries - in minutes rather than hours. The authors also state that they have tested the stability of the alkali metal/electrolyte interface over 1,200 charge cycles with low cell resistance; the specification for Li-ion batteries is usually less than a thousand.

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Skepticism

The publication was initially met with considerable skepticism by other researchers in battery technology, with several noting that it is unclear how a battery voltage is obtained given that pure metallic lithium or sodium exists on both electrodes, which should not produce a difference in electrochemical potential, and therefore give no cell voltage. Any energy stored or released by the battery would therefore violate the first law of thermodynamics. Goodenough's high reputation was enough to deter the strongest criticism however, with Daniel Steingart of Princeton University commenting, "If anyone but Goodenough published this, I would be, well, it's hard to find a polite word." A formal comment was published by Steingart and Venkat Viswanathan from Carnegie Melon University in E&ES.

Goodenough responded to the skepticism, stating: "The answer is that if the lithium plated on the cathode current collector is thin enough for its reaction with the current collector to have its Fermi energy lowered to that of the current collector, the Fermi energy of the lithium anode is higher than that of the thin lithium plated on the cathode current collector." Goodenough went on to say in a later interview with Slashdot that the lithium plated on the cathode is on the "order of a micron thick".

Goodenough's response has drawn further skepticism from Daniel Steingart and also Matthew Lacey of Uppsala University, who point out that this effect is only known for extremely thin layers (monolayers) of materials. Lacey also notes that the original publication does not mention a limit to the thickness of the lithium plated on the cathode, but instead states the opposite: that the capacity of the cell is "determined by the amount of alkali metal used as the anode".

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See also

• Solid-state lithium-ion battery

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References

Source of the article : Wikipedia