Lithium Ion Cells

Anode : Carbon compound, graphite

Cathode : Lithium oxide

Rechargeable batteries that use lithium metal have safety issues. This has lead to a series of cell chemistry developments using lithium compounds instead of lithium metal. These are generically Lithium ion Batteries.

Cathodes consist of a layered crystal (graphite) into which the lithium is intercalated. Experimental cells have also used lithiated metal oxide such as LiCoO2, NiNi0.3Co0.7O2, LiNiO2, LiV2O5, LiV6O13, LiMn4O9,LiMn2O4, LiNiO02CoO2.

Electrolytes are usually LiPF6, although this has a problem with aluminum corrosion, and so alternatives are being sought. One such is LiBF4. The electrolyte in current production batteries is liquid, and uses an organic solvent. Membranes are necessary to separate the electrons from the ions. Current batteries use microporous polyethylene membranes.

Intercalationis a long-studied process which has finally found a practical use. Small ions (lithium, sodium, and other alkali metals) can fit in the interstitial spaces in a graphite crystal. Not only that, but these metallic atoms can go farther and force the graphitic planes apart to fit two, three, or more layers of metallic atoms between the carbon sheets. A great way this is to store lithium in a battery—the graphite is conductive, dilutes the lithium for safety, is reasonably cheap, and does not allow dendrites or other unwanted crystal structures to form.