Lithium tetrafluoroborate is an inorganic compound with the formula . 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.
Applications Although has high ionic mobility, solutions of its salt are less conductive than other less associated salts. As an electrolyte in lithium-ion batteries, offers some advantages relative to the more common . It exhibits greater thermal stability and moisture tolerance. For example, can tolerate a moisture content up to 620 ppm at room temperature whereas readily hydrolyzes into toxic phosphoryl fluoride () and hydrogen fluoride () gases, often destroying the battery's electrode materials. Disadvantages of the electrolyte include a relatively low conductivity and difficulties forming a stable solid electrolyte interface with graphite electrodes.
Thermal stability Because and other alkali-metal salts thermally decompose to evolve boron trifluoride (), the salt is commonly used as a convenient source of the chemical at the laboratory scale:
Production is a byproduct in the industrial synthesis of diborane:
It can also be synthesized from LiF and in an appropriate solvent that is resistant to fluorination by (e.g. , Bromine trifluoride (), or liquified Sulfur dioxide ():
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