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Lithium Peroxide
Lithium peroxide is the inorganic compound with the empirical formula Li2O2. It is a nonhygroscopic solid. Because of its high oxygen:mass and oxygen:volume ratios, the solid has been used to remove carbon dioxide and release oxygen from the atmosphere in many space technologies.

Preparation
It is prepared by the reaction of hydrogen peroxide and lithium hydroxide. This reaction initially produces lithium hydroperoxide:

LiOH + H2O2 → LiOOH + H2O

This lithium hydroperoxide has also been described 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 °C to give lithium oxide AND produces high-purity oxygen:

2 Li2O2 → 2 Li2O + O2

The structure of Li2O2 solid has been determined by X-ray crystallography and density functional theory. The solid features an eclipsed "ethane-like" Li6O2 subunits with an O-O distance of around 1.5 Å.

Uses
Lithium peroxide is used in air purifiers where weight is important, to absorb carbon dioxide and release oxygen in the reaction:

Li2O2 + CO2 → Li2CO3 + 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. This absorption method, along with the decomposition of Li2O2 to produce high-purity oxygen, is commonly used with applications as a source of oxygen in components of spacecraft or other sealed spaces and apparatuses.

A second use of lithium peroxide, the reversible lithium-oxygen reaction with oxygen from the air is the basis for a prototype lithium–air battery. Rechargeable lithium–oxygen batteries based on the reversible formation and decomposition of Li2O2 has wide applications in vehicle applications, for example. Lithium peroxide has a considerably high theoretical energy density, and using oxygen from the atmosphere allows the battery to eliminate storage of oxygen for its reaction, saving battery weight and size.

Lithium peroxide also acts 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.