Rechargeable Lithium Ion (Li-Ion) cells have a negative electrode (anode) made from lithium compounds. Lithium is a highly reactive material and is much lighter than the hydrogen-absorbing metal alloy of the NiMH negative electrode. This leads to higher gravimetric energy densities for the Li-Ion cell. Cells can stay in storage for 12 months without requiring maintenance. The expected cycle life of a Li-Ion in an application is about 1000+ cycles.