US Patent 7615312 Substituted phenothiazine redox shuttles for rechargeable lithium-ion cell

A rechargeable lithium-ion cell contains a positive electrode, negative electrode, charge-carrying electrolyte containing charge carrying medium and lithium salt, and an N-substituted or C-substituted phenothiazine compound dissolved in or dissolvable in the electrolyte. The substituted phenothiazine compound has an oxidation potential above the positive electrode recharged potential and serves as a cyclable redox chemical shuttle providing cell overcharge protection.