What Is Lithium Fluoride?
Lithium fluoride, a white or nearly white odorless powder, is an inorganic compound formed from lithium and fluorine. It exhibits low solubility in water, standing out for its unparalleled ultraviolet light transmittance, making it an exceptional optical material. Notably, it boasts a high melting point of 1,063°C and considerable hardness, ensuring stability under high-temperature conditions.
This compound serves as a precursor for lithium hexafluorophosphate in lithium batteries, a coolant in nuclear reactors, a UV optical material, and more.
Uses of Lithium Fluoride
Lithium fluoride finds applications in lithium batteries, nuclear reactor coolants, optical materials, and conductive materials.
1. Raw Materials for Lithium Batteries
As a key precursor to lithium hexafluorophosphate, an electrolyte for lithium batteries, lithium fluoride is synthesized through a reaction with hydrogen fluoride and phosphorus pentachloride.
2. Reactor Coolant
Due to its chemical stability, lithium fluoride, especially when highly concentrated and mixed with beryllium fluoride (FLiBe), is an efficient nuclear reactor coolant. This mixture, notable for its low melting point and high thermal conductivity, excels in heat dispersion within reactors.
3. Optical Materials
With the highest ultraviolet light transmittance among crystals, lithium fluoride is utilized in special optical components for the UV spectrum. It also plays a role in X-ray spectrometry diffraction crystals and radiation exposure recording instruments.
4. Conductive Material
Boasting a high dielectric constant, lithium fluoride enhances electron injection in cathodes for OLEDs and synthesized LEDs, typically applied as a thin layer of about 1 nm.
Properties of Lithium Fluoride
Lithium fluoride (LiF), with a molecular weight of 25.94, forms clear, colorless crystals. It’s virtually insoluble in water yet dissolves in ethanol and dimethylformamide. Its robust melting and boiling points are 1,063°C and 1,686°C, respectively. Characterized as an ionic crystal, it has a cubic structure with a lattice constant of 3.01 Å, contributing to its hardness and industrial importance due to excellent thermal and electrical conductivity.
Structure of Lithium Fluoride
The cubic structure of lithium fluoride’s ionic crystal alternates between lithium and fluoride ions, with a dense lattice constant of approximately 3.01 Å, attributing to its significant hardness.
Other Information on Lithium Fluoride
Production Method of Lithium Fluoride
Lithium fluoride is typically produced by reacting water-soluble lithium salts (e.g., lithium sulfate, carbonate, nitrate, or chloride) with hydrofluoric acid. The reaction, exemplified with lithium sulfate as Li2SO4 + HF → LiF↓ + LiHSO4, precipitates lithium fluoride, which is then filtered, washed, and dried to yield the powdered form.