Lithium cobalt oxide
|Lithium cobalt oxide|
|Molar mass||97.87 g mol−1|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Lithium cobalt oxide (LiCoO2) is a chemical compound commonly used in the positive electrodes of lithium-ion batteries. The structure of LiCoO2 is known theoretically and has been confirmed with techniques like x-ray diffraction, electron microscopy, neutron powder diffraction, and EXAFS: it consists of layers of lithium that lie between slabs of octahedra formed by cobalt and oxygen atoms. The space group is  in Hermann-Mauguin notation, signifying a rhombus-like unit cell with threefold improper rotational symmetry and a mirror plane. More simply, however, both lithium and cobalt are octahedrally coordinated by oxygen. These tetrahedra are edge-sharing, and tilted relative to the layered structure. The threefold rotational axis (which is normal to the layers) is termed improper because the triangles of oxygen (being on opposite sides of each octahedron) are anti-aligned.
Batteries produced with LiCoO2 cathodes, while providing higher capacity, are more reactive and have poorer thermal stability than chemistries such as the newer lithium-nickel-cobalt-aluminum-oxide types. This makes LiCoO2 batteries susceptible to thermal runaway in cases of abuse such as high temperature operation (>130 °C) or overcharging. At elevated temperatures, LiCoO2 decomposition generates oxygen, which then reacts with the organic electrolyte of the cell. This is a safety concern due to the magnitude of this highly exothermic reaction, which can spread to adjacent cells or ignite nearby combustible material.
Exposure to soluble cobalt salts can lead to cardiomyopathy. MSDS sheets list lithium cobalt oxide as a potential human carcinogen but indicate "no data available" under the Acute Toxicity heading. However, unlike cobalt(II) salts, this oxide is insoluble in water. Lithium ion batteries contain lithium cobalt oxide and are considered nonhazardous waste. Safety precautions should be taken when handling it.
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