What Is Lithium Hydroxide?

Lithium hydroxide is a compound formed of the white, soft metal lithium bound to a hydroxide group with the formula LiOH. It is commercially available in anhydrous form free of chemical bonds to water, though it is a hygroscopic chemical by nature that is also sold in monohydrate form as LiOH H₂O. The compound is used in a variety of industries with popular commercial demands for it in the manufacture of lithium batteries and as lithium hydroxide monohydrate to make lubricating greases. Lithium-based greases are stable over a wide range of temperatures and resistant to degradation, making them useful in high performance machines like aircraft and marine engines.

While lithium itself is a widely-used metal in many industries from optics to fusion research and the manufacture of rubbers and plastics, lithium hydroxide has more specialized uses. Its common use as a coloring agent and battery ingredient are based upon its basic properties. In nickel-metal-hydride batteries, lithium hydroxide is an important compound that serves to enhance the durability and conductivity of the battery. It does this by precipitating, or absorbing carbon dioxide gas that is produced as the storage-battery electrolyte is used, binding it into a new solid compound of lithium and carbon in the process known as lithium carbonate, Li₂CO₃. The bright silver-white nature of lithium metal also makes lithium hydroxide a useful chemical that can be dissolved in various dyes and pigments, which increases the brilliance of the colors for such liquids.

As a precursor chemical for the manufacture of lithium grease, the compound is used to make several lithium stearate chemicals, with 12-hydroxy-stearate being the most popular one used in industry. The use of such grease has become widespread in machinery as of 2011 where high temperatures are generated, as it withstands a heat level of up to 392° Fahrenheit (200° Celsius) without breaking down. The lithium family of greases are also known to be strongly resistant to water damage and degradation, which can break down other sealant greases in liquid cooled machinery, such as in automotive and construction equipment engines.

One of the more unique uses for lithium hydroxide is in the purification of gases. It has been incorporated into equipment used on the International Space Station (ISS) for the purification of air, though the units cannot be regenerated and are being replaced by more versatile metal-oxide scrubbers. When astronauts exhale carbon dioxide gas, lithium hydroxide reacts with this to form lithium carbonate and water, as it does in storage batteries. The compound is still in use on the ISS as of 2011 for astronaut equipment known as the Primary Life Support System (PLSS). The PLSS is part of the backpack equipment an astronaut wears as a component of their Extravehicular Mobility Unit (EMM), or spacesuit, to make excursions outside the confines of the ISS or orbiting space vehicle.