Battery systems have undergone significant improvements over the past 25 years. Older systems have been updated with new materials and constructions. New lithium and nickel systems have been introduced, especially in the rechargeable segment, and have undergone tremendous growth and reached maturity. The technology and applications of the various battery systems are reviewed here, and the status of commercial aqueous and nonaqueous systems updated. NEC first introduced electrochemical capacitors in August 1978 under the trade name Supercapacitor™. Electrochemical capacitor technology has evolved from first generation products with low energy density for memory protection applications through several generations of designs to create megajoule-size capacitors for transportation and power quality applications.

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Recent progress in the development of rechargeable alkaline zinc-manganese dioxide cells is described. The advantages and limitations of the system are evaluated. Laboratory tests run on commercial primary alkaline cells as well as model simulations of a bipolar MnO~ electrode show that the rechargeable alkaline battery may be able to compete with lead-acid, nickel-cadmium, and secondary lithium cells for low-to moderate-rate applications. However, because of its poor performance at high rates and low temperatures, the alkaline MnO~ battery is not suitable for present automotive starting applications.

The effect of phosphoric acid on the positive electrode reaction in a leadacid battery is studied by cyclic voltammetry. It is proposed that phosphate reversibly adsorbs on the PbO2 during charge, and modifies the crystal growth of PbO2 on the lead grid. The form of PbO2 produced in the presence of phosphate is not easily reduced to lead sulfate and, therefore, the positive grid does not become insulated from the active material. The limit of this effect is reached at a low concentration of phosphoric acid.

The effect of H~PO4 on the constant potential corrosion of the positive grid in the lead-acid battery has been studied. The metallurgical and chemical properties of the corrosion products have been examined and correlated with their electrochemical behavior during self-discharge and voltammetric cycling. Low concentrations of H3PO4 in the electrolyte modify the crystal growtl~ of PbO2 on the lead grid, producing a structure which is not readily discharged to PbSO4. * Electrochemical Society Active Member.