Lithium oxide
Lithium oxide, with the chemical formula Li₂O, is an inorganic compound that appears as a white, hygroscopic, and odorless solid powder.[1] It is highly reactive with water and moisture, rapidly forming corrosive lithium hydroxide (LiOH), and also reacts with carbon dioxide to produce lithium carbonate.[1] This compound has a molecular weight of 29.88 g/mol, a theoretical density of 2.01 g/cm³, and a high lithium density of 0.93 g/cm³, contributing to its utility in specialized applications.[2] Its crystal structure adopts the antifluorite type with space group Fm-3m.[1] Key physical properties include a melting point of 1432 °C, good thermal conductivity of 6 W/m·K at 400 °C, and a specific heat capacity of 2.5 J/g·K at the same temperature, though it is sensitive to moisture and exhibits swelling under neutron irradiation.[2] These characteristics make lithium oxide suitable for high-temperature environments, but its reactivity necessitates careful handling to avoid corrosion or decomposition.[1] As a corrosive substance, it can cause severe burns to skin and eyes upon contact and respiratory irritation if inhaled, classifying it as toxic in certain exposure scenarios.[1] Lithium oxide serves as a vital flux in ceramics and glass manufacturing, where it lowers melting temperatures, improves melt rates, and enhances properties like refractive index and chemical durability in specialty glasses.[3][4] In energy storage, it acts as a cathode material in lithium-air batteries, offering high energy density and low self-discharge rates, which supports applications in electric vehicles and renewable energy systems.[2] Additionally, due to its high lithium content and thermal properties, it was considered in early nuclear fusion reactor designs for tritium breeding blankets, though irradiation-induced swelling limits broader adoption.[2] It also functions as a carbon dioxide absorbent in certain industrial processes.[1]Properties
Physical properties
Lithium oxide, with the chemical formula Li₂O and a molecular weight of 29.88 g/mol, is a white, odorless, crystalline solid that appears as a fine powder.[5][1] It exhibits a density of 2.013 g/cm³ at 25 °C, reflecting its compact ionic structure.[6][5] The compound demonstrates high thermal stability, with a melting point of 1,438 °C (2,620 °F) and sublimes above 1000 °C.[7][8][9] Its thermal conductivity is approximately 14.5 W/m·K at 300 K, decreasing with increasing temperature due to phonon scattering effects.[10] The linear thermal expansion coefficient is about 25.9 × 10⁻⁶ K⁻¹ at 300 K, rising to around 41.4 × 10⁻⁶ K⁻¹ near 1,200 K, which influences its behavior in high-temperature applications.[10] Due to its hygroscopic nature, it absorbs moisture from the air, leading to surface deliquescence and the formation of a hydroxide layer that alters its appearance and handling properties over time.[1][5]| Property | Value | Conditions/Source |
|---|---|---|
| Molecular weight | 29.88 g/mol | ChemicalBook |
| Density | 2.013 g/cm³ | 25 °C Sigma-Aldrich SDS |
| Melting point | 1,438 °C (2,620 °F) | Stanford Advanced Materials |
| Boiling point | Sublimes above 1000 °C | Nature Energy (2025) |
| Thermal conductivity | ~14.5 W/m·K | 300 K ARIES Fusion Library |
| Linear thermal expansion | 25.9 × 10⁻⁶ K⁻¹ | 300 K ARIES Fusion Library |