Lithium tetrafluoroborate is an

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula Li BF₄. It is a white crystalline powder. It has been extensively tested for use in commercial secondary batteries, an application that exploits its high solubility in nonpolar solvents.Xu, Kang. "Nonaqueous Liquid Electrolytes for Lithium-Based Rechargeable Batteries."Chemical Reviews 2004, volume 104, pp. 4303-418.

Applications

Although BF₄⁻ has high ionic mobility, solutions of its Li⁺ salt are less conductive than other less associated salts. As an

electrolyte An electrolyte is a substance that conducts electricity through the movement of ions, but not through the movement of electrons. This includes most soluble Salt (chemistry), salts, acids, and Base (chemistry), bases, dissolved in a polar solven ...

lithium-ion batteries A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible intercalation of Li+ ions into electronically conducting solids to store energy. Li-ion batteries are characterized by higher specific energy, energy ...

, LiBF₄ offers some advantages relative to the more common LiPF₆. It exhibits greater thermal stability and moisture tolerance. For example, LiBF₄ can tolerate a moisture content up to 620 ppm at room temperature whereas LiPF₆ readily hydrolyzes into toxic POF₃ and HF gases, often destroying the battery's

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can consist of a varie ...

materials. Disadvantages of the electrolyte include a relatively low conductivity and difficulties forming a stable solid electrolyte interface with

graphite Graphite () is a Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...

electrodes.

Thermal stability

Because LiBF₄ and other alkali-metal salts thermally decompose to evolve

boron trifluoride Boron trifluoride is the inorganic compound with the formula . This pungent, colourless, and toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds. Structure and bonding The g ...

, the salt is commonly used as a convenient source of the chemical at the laboratory scale: : LiBF₄ → LiF + BF₃

Production

LiBF₄ is a byproduct in the industrial synthesis of

diborane Diborane(6), commonly known as diborane, is the chemical compound with the formula . It is a highly toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Given its simple formula, borane is a fundamental boron compound. It has att ...

: :8 BF₃ + 6 LiH → B₂H₆ + 6 LiBF₄ LiBF₄ can also be synthesized from LiF and BF₃ in an appropriate solvent that is resistant to fluorination by BF₃ (e.g. HF, BrF₃, or liquified SO₂): : LiF + BF₃ → LiBF₄

References

Tetrafluoroborates Lithium salts Electrolytes {{electrochem-stub