Lithium cobalt dioxide accumulator

The lithium cobalt dioxide accumulator , also LiCoO ₂ accumulator, is a lithium ion accumulator with lithium cobalt (III) oxide (LiCoO ₂ ) as the positive electrode material. From about 1990 to 2010, most commercial mobile devices used a lithium-cobalt dioxide battery, which was also the first commercially available type of lithium-ion battery. Due to this dominance in the market, the generic term lithium-ion battery was in many cases synonymous with the variant lithium-cobalt dioxide battery. This is no longer the case today, as lithium-ion batteries with different chemical compositions are sold.

Like all lithium ion accumulators, LiCoO ₂ accumulators can also be designed as lithium polymer accumulators .

Lithium cobalt dioxide accumulators tend to run away thermally when overloaded .

history

The lithium cobalt dioxide accumulator was the first commercially available accumulator with lithium ions that did not use lithium metal on the negative pole side. The usefulness of LiCoO ₂ as an electrode material was discovered in 1980 by a research group led by John B. Goodenough at the University of Oxford . The positive electrode consists of the eponymous substance lithium cobalt (III) oxide . The first commercially available Li-ion battery was taken as lithium Cobaltdioxid accumulator by Sony in 1991 to the market and in the Hi8 - Video camera CCD TR 1 used had two series-connected cells, a battery pack voltage of 7, 2 V and a capacity of around 1200 mAh.

construction

The negative electrode of a commercially available lithium cobalt dioxide accumulator consists of graphite , the positive electrode consists of lithium cobalt dioxide (LiCoO ₂ ) and the electrolyte is a lithium salt in an organic solution. Copper and aluminum are used as arrester materials.

The electrolyte consists of a mixture of aprotic solvents such as ethylene carbonate , propylene carbonate , dimethyl carbonate , diethyl carbonate or 1,2-dimethoxyethane as well as lithium hexafluorophosphate (LiPF ₆ ) dissolved therein . The electrolyte must be anhydrous (H ₂ O content <20 ppm), otherwise the water will react with the conductive salt LiPF ₆ to form HF (hydrofluoric acid).

The lithium itself only makes up a fraction of the battery material used. It is just 1 to 1.5%, the rest are the materials of the cathode, the anode or the conductive copper layers.

Reaction equation

Half-reaction of the positive electrode (lithium cobalt dioxide layer):

${\displaystyle \mathrm {CoO_{2}} +\mathrm {Li^{+}} +\mathrm {e^{-}} \leftrightarrows \mathrm {LiCoO_{2}} }$

Half-reaction of the negative electrode (graphite layer):

${\displaystyle \mathrm {LiC_{6}} \leftrightarrows \mathrm {6C} +\mathrm {Li^{+}} +\mathrm {e^{-}} }$

Overall reaction (left: charging, right: discharging):

${\displaystyle \mathrm {LiC_{6}} +\mathrm {CoO_{2}} \leftrightarrows \mathrm {6C} +\mathrm {LiCoO_{2}} }$

In the event of severe overcharging (cell voltage above 4.6 V), the electrolyte is decomposed. When charging too quickly, metallic lithium is produced on the graphite electrode, which reacts with the electrolyte and thus consumes it. In addition, the metallic lithium can lead to short circuits and thus overheating and fire

application

Until around 2010, most lithium-ion batteries contained lithium cobalt dioxide as a positive electrode material, including batteries from Apple ( iPhone 6 Plus), Microsoft, Samsung and Sony, as well as electric cars from Daimler and Volkswagen.

Lithium-ion batteries will still contain cobalt oxide in 2020, especially when it comes to high energy densities or high discharge currents. However, it is usually no longer the original lithium cobalt (III) oxide LiCoO ₂ , but rather mixed oxides related to LiCoO ₂ such as the lithium nickel manganese cobalt oxides NMC in the NMC accumulator or lithium nickel Cobalt-Aluminum-Oxide NCA.

Handling and dangers

Burned out lithium cobalt dioxide accumulator from a Boeing 787 Dreamliner

In the event of mechanical damage, overcharging, short circuit or excessive charging of deeply discharged batteries, short circuits and / or highly exothermic reactions that cannot be stopped can occur. Due to the strong heat development, the components of the cell can dissolve (e.g. the separator), an internal short circuit occurs (if this is not the cause) and from temperatures of approx. 180 ° C on the lithium cobalt (III) oxide used to the release of oxygen in the cell, which ultimately leads to an uncontrolled thermal runaway that can no longer be influenced from the outside, leading to a fire.

Burning lithium-ion batteries give off toxic and irritating fumes.

Burning lithium cobalt dioxide accumulators and other lithium ion accumulators should be extinguished with plenty of water. Once the process of thermal runaway has started, the fire can no longer be suffocated by the oxygen generation in the cell, which is independent of the ambient air, but cooling using water can protect other cells and prevent the fire from spreading. Another measure for small accumulators or individual cells is the controlled burning of the accumulator.

Lithium-cobalt dioxide batteries are installed in the Boeing 787 Dreamliner passenger aircraft , which led to two fires in January 2013. Ultimately, the cause has not been clarified.

Individual evidence

1. ^ Daniel Doughty, Ahmad Pesaran: Vehicle Battery Safety Roadmap Guidance . National Renewable Energy Laboratory. Retrieved January 19, 2013.
2. ↑ K. Mizushima, PC Jones, Philip J. Wiseman, John B. Goodenough: Li _x CoO ₂ (0 <x ≤ 1): A new cathode material for batteries of high energy density . In: Materials Research Bulletin . tape 15 , no. 6 . Elsevier, June 1980, ISSN  0025-5408 , pp. 783-789 , doi : 10.1016 / 0025-5408 (80) 90012-4 ( elsevier.com ).
3. ↑ A look inside an iphone 6 plus battery . 
4. ↑ HJ Bergveld, WS Kruijt, PHL Notten: Battery Management System: Design by modeling . Springer , 2002, ISBN 978-94-017-0843-2 , pp. 107-108, 113.
5. ↑ S Dhameja: Electric Vehicle Battery Systems . Newnes Press , 2001, ISBN 978-0-7506-9916-7 , p. 12.
6. ↑ A look inside an iphone 6 plus battery . 
7. ↑ Vehicle Battery Safety Roadmap Guidance. (PDF) National Renewable Energy Laboratory, US Department of Energy, p. 108 , accessed October 10, 2017 .  
8. ↑ ^{a b} https://www.umweltbundesamt.de/umwelttipps-fuer-den-alltag/elektrogeraete/lithium-batterien-lithium-ionen-akkus#gewusst- wie communication from the Federal Environment Agency on handling lithium batteries, accessed on March 4, 2020
9. ↑ https://vision-mobility.de/news/lithium-ionen-akkus-am-besten-mit-wasser-loeschen-1991.html Thilo Jörgl: It is best to extinguish lithium-ion batteries with water, experts advise against fires other extinguishing agents. Announcement from Huss Verlag on September 24, 2018, accessed on March 4, 2020
10. ^ Daniel Michaels: Batteries Like Those on Dreamliner Raised Concerns . In: The Wall Street Journal , January 18, 2013. Retrieved January 19, 2013.