They are already environmentally safe. Rechargeable Lithium-ion
batteries use lithium salts (lithium oxide or lithium hydroxide) in an organic solvent as the electrolyte, and a layered oxide (lithium cobalt oxide for regular cells, lithium manganese oxide for IMRs) as the positive cathode. The negative cathode is just carbon (graphite). All of these are environmentally neutral. It's only the non-rechargeable lithium batteries that use free metallic lithium and pose an environmental hazard.