This paper reviews developments in batteries over the past 50 years with particular reference to advances in materials science and engineering technology. The emphasis is on commercially available batteries such as zinc/manganese dioxide primary cells, and lead/acid and nickel/alkaline secondary cells, although specialist batteries and those in an advanced stage of development are also described briefly. Rechargeable lithium-ion batt. This paper reviews developments in batteries over the past 50 years with particular reference to advances in materials science and engineering technology. The emphasis is on commercially available batteries such as zinc/manganese dioxide primary cells, and lead/acid and nickel/alkaline secondary cells, although specialist batteries and those in an advanced stage of development are also described briefly. Rechargeable lithium-ion batteries will be covered in another paper in this symposium.••Fifty years is a long time in the history of materials science, and also in the design, development and application of primary and secondary batteries. In the 1940s, the principal domestic uses for batteries were in torches (flashlamps), in a few toys, in vehicles (for starting, lighting and ignition) and in radios. Before the days of transistors and solid state electronics, when thermionic valves (tubes) were used in radios, it was necessary to have a source of low voltage electricity to heat the filament and a DC high voltage to accelerate electrons between the valve cathode and anode. Many radios in those days were remote from the electricity supply and then two batteries were required, a 2 V lead/acid accumulator to supply the filament current and a 'high tension' battery consisting of 100 or 120 Leclanché cells wired in series to supply the high DC voltage. The radio weighed several kilograms, had to be maintained in an upright position to avoid spillage of acid and was anything but 'portable'. No doubt there were other applications for batteries in industry and commerce, for example emergency lighting and back-up for the primitive telephone system of the day.Over the past 50 years the applications for small batteries in the home (consumer batteries) have expanded phenomenally. Today small primary or rechargeable batteries are employed in a huge number of appliances. Some e. 2.1. Zinc/manganese dioxide (1.5 V) primary cellsFifty years ago most primary batteries were of the Leclanché type in which the zinc negative electrode was in the form of a metal can which acted as the container for the other cell components. There was a central carbon rod which served as the positive electrode and this was surrounded by a mixture of crude MnO2 (often the mineral pyrolusite) and carbon powder, intimately mixed together. The function of the carbon powder was to increase the conductivity of the positive active mass and so to reduce the internal resistance of the cell. The electrolyte, an aqueous solution of ammonium chloride and zinc chloride, was absorbed into the pores of a paste type separator (e.g. starch) and the MnO2/C mixture, and for this reason these cells became known as 'dry cells'. The cells had a seal and vent at their upper end and a non-conducting board cap which served to insulate the positive carbon rod from the negative zinc can. Finally, the zinc can was surrounded by a cardboard jacket, on which the manufacturer's name and information was printed.Over the years some improvements have been made in the design of Leclanché cells and their materials of construction. The metallurgy of the zinc can has been improved through alloying additions to facilitate deep drawing. Better designs of seals have been developed. The use of mercury to increase the over-potential for h. For 15–20 years there has been enormous international activity in the development of lithium batteries, both primary and secondary. The interest stems from the low atomic mass of lithium (6.94), its high specific capacity (3.86 Ah/g) and its high electrochemical reduction potential (−3.045 V), all of which contribute to a high specific energy for lithium cells.Primary cells normally employ lithium metal foil as anodes, whereas secondary lithium cells are not usually based on lithium metal since experience has shown that repeated recharging of lithium metal anodes can be dangerous. Rather, most rechargeable lithium cells are of the 'lithium ion' type in which Li+ ions are intercalated into a carbon anode in the charged state and into an oxide cathode in the discharged state.Numerous cathode compounds have been used in lithium primary cells, e.g. CuO, CuS, CFx, MnO2, MoO3, V2O5 etc. Commercially, the most widely adopted positive-electrode materials are CFx, and MnO2. The electrolyte employed in lithium cells is a solution of a lithium salt in an organic solvent. The number of possible combinations of salt and solvent is large, and most lithium cell manufacturers have their own preferred solution.Lithium/manganese. The lead/acid battery was invented in 1859 by Planté and developed further by Faure in 1881. In the original Planté cell the active materials of the electrodes were obtained by passing a current between soft lead plates. This led to the conversion of the surface of the positive plate to PbO2 and that of the negative plate to spongy metallic lead. Modified Planté cells are still used in many standby batteries. The innovation introduced by Faure was the pasted plate wherein a sheet of lead is coated with a paste of lead oxide and sulphuric acid. By passing a current through the cell ('forming the plates') the positive is converted to PbO2 and the negative to spongy lead. Because of the greater mass of active material, the Faure cell has greater capacity than the Planté cell. Although invented more than 100 years ago, the lead/acid battery still has the overwhelming share of the secondary battery market.During this century the battery has been subject to continuous improvement in materials of construction, design and manufacture, and this process is still ongoing. Many of these improvements have been of an engineering rather than scientific nature. Some examples are:••the.
