What is the best way to store lithium?
I tried extra virgin cold-pressed heart-healthy olive oil. The lithium appears to react initially, producing a few bubbles. However, the lithium was covered with its foamy electrolyte and so it was not clear whether it was the lithium or the electrolyte reacting. The reaction appears to stop after a while. Olive oil primarily consists of oleic and palmitic acid esters, which do not seem to react with the lithium metal. So olive oil is a good, though not ideal, way to store lithium metal because of its lightness. Lithium is liable to get stuck on the side of the container after any disturbance because of its density. After the oil drains from the surface, it is susceptible to oxidation and therefore is destroyed.
Plastic wrap is the first method that I used to store lithium metal. However, the lithium's reaction with almost all atmospheric gases guaranteed that some gas would find its way into the plastic wrap. The lithium did have somewhat of a restriction on reacting; I detected a distinct smell of ammonia when the resulting white powder was placed in water, signifying that nitride was produced due to the lack of oxygen.
I then tried petroleum jelly. Lithium keeps very well in this medium. Since it does not float in petroleum jelly, there is no worry about lithium being isolated on the side of a container. A large piece of lithium can be covered with petroleum jelly and pressed against the side of a container to make an excellent lithium display for an element collection. A disadvantage is that the petroleum jelly coats the surface of the lithium, making it less likely to react and contaminating any reaction.
LIthium can remain in air for about a day before it starts significantly oxidizing (turning white). This is for normal air with about 40% humidity. With extra-humid air, however, the time period is much shorter. If you are opening a lithium coin cell for only one quick experiment, it is best to skip preservation and just use the lithium as-is. For a collection or display, use petroleum jelly. For further experiments, use petroleum jelly but be sure to completely wipe off the lithium before use.