21 - Alkaline manganese batteries

Abstract

This chapter discusses two types of alkaline manganese batteries: primary and secondary. Cylindrical alkaline manganese batteries have an inverted construction compared with the familiar Leclanché carbon-zinc battery construction. In the cylindrical alkaline manganese battery the positive terminal is formed by a stud, in contact with the cathode at the top of the battery, fixed to a steel can which surrounds the positive electrode. The hermetically sealed can and steel jacket take no part in the electrochemical reactions of the cell. Where acetylene black is generally used as an additive to the manganese dioxide in a Leclanché battery, the higher conductivity of the potassium hydroxide electrolyte used in the alkaline manganese battery allows the use of highly conductive graphite as a cathode additive. The highly compressed cylindrical manganese dioxide cathode is lined with an absorbent separator and the gelled anode of amalgamated high-surface-area zinc powder inserted. Contact to the negative terminal at the base of the battery is by an internal metal contact. This design gives a high current density per unit volume of active materials, low resistance and impedance, high service capacity, and a relatively constant capacity over a range of current drawing and discharge schedules. Further, the individual cells that comprise the rechargeable alkaline dioxide battery use electrodes of zinc and manganese dioxide containing 10% graphite with an electrolyte of potassium hydroxide. These are put together in a special inside-out cell construction and each cell is then hermetically sealed. The voltage per cell is 1.5V.