Lithium peroxide

{{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 447495940 | Name = Lithium peroxide | ImageFile1=Lithium peroxide.svg | ImageSize1= 150px | ImageFile2=Li2O2.png | ImageSize2= | ImageCaption2 = <span style="color:#C0C0C0; background-color:#C0C0C0;">__</span> Li⁺&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span style="color:#FF0000;background-color:#FF0000;">__</span> O⁻ | ImageName = Lithium peroxide |IUPACName=Lithium peroxide | OtherNames = Dilithium peroxide<br />Lithium(I) peroxide |Section1={{Chembox Identifiers | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 23787 | InChI = 1/2Li.O2/c;;1-2/q2*+1;-2 | InChIKey = HPGPEWYJWRWDTP-UHFFFAOYAV | SMILES = [Li+].[Li+].[O-][O-] | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/2Li.O2/c;;1-2/q2*+1;-2 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = HPGPEWYJWRWDTP-UHFFFAOYSA-N | CASNo_Ref = {{cascite|correct|??}} | CASNo = 12031-80-0 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 9ANX556R5F | PubChem = 25489 }} |Section2={{Chembox Properties | Formula = Li₂O₂ | MolarMass = 45.885 g/mol | Appearance = fine, white powder | Odor = odorless | Density = 2.32 g/cm³<ref>[http://www.hbcpnetbase.com/pdf/default.asp?id=04_02_91 "Physical Constants of Inorganic Compounds,"] in CRC Handbook of Chemistry and Physics, 91st Edition (Internet Version 2011), W. M. Haynes, ed., CRC Press/Taylor and Francis, Boca Raton, Florida. (pp: 4-72).</ref><ref>Speight, James G. (2005). Lange's Handbook of Chemistry (16th Edition). (pp: 1.40). McGraw-Hill. Online version available at: http://www.knovel.com/web/portal/browse/display?_EXT_KNOVEL_DISPLAY_bookid=1347&VerticalID=0</ref> | Solubility = soluble{{vague|date=August 2022}} | MeltingPt = Decomposes to Li₂O at ~450°C but melts at 197°C<ref>Phys.Chem.Chem.Phys.,2013,15, 11025. {{doi|10.1039/c3cp51056e}}</ref> | BoilingPt = NA }} |Section3={{Chembox Structure | CrystalStruct = hexagonal }} |Section4={{Chembox Thermochemistry | DeltaHf = −13.83 kJ/g | DeltaHc = | Entropy = | HeatCapacity = }} |Section7={{Chembox Hazards | GHSPictograms = {{GHS03}}{{GHS05}} | GHSSignalWord = Danger | HPhrases = {{H-phrases|271|272|314}} | PPhrases = {{P-phrases|210|220|221|260|264|280|283|301+330+331|303+361+353| 304+340|305+351+338|306+360|310|321|363|370+378|371+380+375|405|501}} | NFPA-H = 3 | NFPA-R = 2 | NFPA-F = 0 | NFPA-S = OX }} | Section8 = {{Chembox Related | OtherAnions = | OtherCations = Sodium peroxide<br>Potassium peroxide<br>Rubidium peroxide<br>Caesium peroxide | OtherCompounds = }} }}

'''Lithium peroxide''' is the inorganic compound with the formula Li₂O₂. Lithium peroxide is a white solid, and unlike most other alkali metal peroxides, it is nonhygroscopic. Because of its high oxygen:mass and oxygen:volume ratios, the solid has been used to remove CO₂ from and release O₂ to the atmosphere in spacecraft.<ref name="Greenwood" />

==Preparation== It is prepared by the reaction of hydrogen peroxide and lithium hydroxide. This reaction initially produces lithium hydroperoxide:<ref name="Greenwood">{{Greenwood&Earnshaw1st|page=98}}</ref><ref name=Brauser>E. Dönges "Lithium and Sodium Peroxides" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 979.</ref> :LiOH + H₂O₂ → LiOOH + H₂O This lithium hydroperoxide may exist as lithium peroxide monoperoxohydrate trihydrate (Li₂O₂·H₂O₂·3H₂O). Dehydration of this material gives the anhydrous peroxide salt: :2 LiOOH → Li₂O₂ + H₂O₂

Li₂O₂ decomposes at about 450&nbsp;°C to give lithium oxide: :2 Li₂O₂ → 2 Li₂O + O₂

The structure of solid Li₂O₂ has been determined by X-ray crystallography and density functional theory. The solid features eclipsed "ethane-like" Li₆O₂ subunits with an O-O distance of around 1.5 Å.<ref>L. G. Cota and P. de la Mora "On the structure of lithium peroxide, Li₂O₂" Acta Crystallogr. 2005, vol. B61, pages 133-136. {{doi|10.1107/S0108768105003629}}</ref>

==Uses== ===Air purification=== It is used in air purifiers where weight is important, e.g., spacecraft or other sealed spaces and apparatuses to absorb carbon dioxide and release oxygen in the reaction:<ref name="Greenwood" />

Li₂O₂ + CO₂ → Li₂CO₃ + {{frac|1|2}} O₂

Similar to the reaction of lithium hydroxide with carbon dioxide to release 1 Li₂CO₃ and 1 H₂O, lithium peroxide has high absorption capacity and absorbs more CO₂ than does the same weight of lithium hydroxide and offers the bonus of releasing oxygen instead of water. <ref name="Ullmann">Ulrich Wietelmann, Richard J. Bauer "Lithium and Lithium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH: Weinheim. {{doi|10.1002/14356007.a15_393.pub2}}</ref>

===Styrene polymerization=== Lithium peroxide can also act as a catalyst for polymerization of styrene to polystyrene. The polymerization of styrene to polystyrene typically involves the use of radical initiators via the free radical chain mechanism but lithium peroxide can also initiate radical polymerization reactions under certain conditions, although not as widely used.

===Lithium-air battery=== The reversible lithium peroxide reaction is the basis for a prototype lithium–air battery. Using oxygen from the atmosphere allows the battery to eliminate storage of oxygen for its reaction, saving battery weight and size.<ref>{{cite journal|last=Girishkumar|first=G.|author2=B. McCloskey |author3=AC Luntz |author4=S. Swanson |author5=W. Wilcke |title=Lithium- air battery: Promise and challenges|journal=The Journal of Physical Chemistry Letters|volume=1|issue=14|date=July 2, 2010|pages=2193–2203|doi=10.1021/jz1005384}}</ref>

==See also== * Lithium oxide * Lithium monoxide anion

==References== <references/>

==External links== * [http://www.webelements.com/webelements/compounds/text/Li/Li2O2-12031800.html WebElements entry]

{{Lithium compounds}} {{Peroxides}}

Category:Peroxides Category:Lithium compounds Category:Oxidizing agents