Dihydrophenazine derivatives for overcharge protection of rechargeable lithium batteries

Two dihydrophenazine derivatives bearing either 2-hydroxypropyl or ethyl substituents on both N atoms, have been tested in liquid and polymer electrolyte lithium cells. Only the first one bearing 2-hydroxypropyl substituents induced a levelling of the overcharge potential. The fixed potential corresponded to either of its redox systems according to the current density and the internal resistance of the unit cells. At present the possible determining role of the hydroxyl groups is a drawback owing to its reactivity on lithium metal.