- Lithium borohydride (LiBH₄) is a white crystalline inorganic compound composed of lithium (Li⁺) and the borohydride anion (BH₄⁻). It is best known for its role as a powerful reducing agent in organic and inorganic chemistry, and for its potential use in hydrogen storage applications.
- Lithium borohydride is part of the broader class of metal borohydrides, which contain a boron atom bonded to four hydrogen atoms, forming a tetrahedral anion. Its unique combination of reactivity, hydrogen content, and ionic character makes it a compound of considerable interest in both laboratory and emerging energy technologies.
- In organic synthesis, LiBH₄ is widely used as a reducing agent, particularly for the conversion of esters, carboxylic acids, lactones, and amides into alcohols. It is more reactive than sodium borohydride (NaBH₄), especially in non-aqueous solvents like tetrahydrofuran (THF) and diethyl ether. This higher reactivity allows it to reduce more resistant carbonyl compounds under milder conditions. LiBH₄ is also compatible with selective reduction reactions and is sometimes used in stepwise or tandem syntheses where specific functional group reduction is needed.
- One of the most promising areas of research involving lithium borohydride is its application in hydrogen storage. LiBH₄ contains 18.5% hydrogen by weight, making it one of the highest hydrogen content materials available. When heated or reacted with water, it releases hydrogen gas, making it a potential candidate for use in fuel cells and portable hydrogen storage systems. However, its practical use in hydrogen storage is still limited by issues such as high dehydrogenation temperatures, slow kinetics, and the irreversibility of hydrogen release without complex regeneration processes.
- LiBH₄ also finds application in materials science and solid-state chemistry, particularly as a solid electrolyte in lithium-ion batteries and all-solid-state battery systems. In these contexts, lithium borohydride can provide both lithium-ion conductivity and stability under certain conditions, though its practical use is limited by its reactivity with moisture and air. Its role in battery research highlights its multifunctional nature, offering both chemical reactivity and ionic transport properties.
- In terms of handling and safety, lithium borohydride is a moisture-sensitive and flammable material. It reacts vigorously with water and alcohols, releasing hydrogen gas, which can ignite in air. As a result, it must be stored in airtight containers, typically under an inert atmosphere like nitrogen or argon, and handled with care in a dry environment. These safety considerations, while manageable, limit its widespread adoption in some practical settings without appropriate containment and safety systems.
