Lithium peroxide

Lithium peroxide is the inorganic compound with the formula Li₂O₂. It is a white, nonhygroscopic solid. Because of its low density, the solid has been used to remove CO₂ from the atmosphere in spacecraft.

Preparation

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

This lithium hydroperoxide has also been described as lithium peroxide monoperoxohydrate trihydrate (Li₂O₂·H₂O₂·3H₂O). Dehydration of this material gives the anhydrous peroxide salt:

Li₂O₂ decomposes at about 450 °C to give lithium oxide:

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

Uses

It is used in air purifiers where weight is important, e.g., spacecraft to absorb carbon dioxide and release oxygen in the reaction:

It absorbs more CO₂ than does the same weight of lithium hydroxide and offers the bonus of releasing oxygen. Furthermore, unlike most other alkali metal peroxides, it is not hygroscopic.