How Are Electrodes Made? By Cutting a Bar of Steel

Although the basis of the nickel-cadmium cell is chemistry, its production is relatively simple engineering. Simple, but very precise, like folding electrode plates.

Most people's idea of the inside of a galvanic cell is based on schematic drawings and experiments as we remember them from chemistry classes. So, two rods immersed in electrolyte. The electrode of a real nickel-cadmium cell would therefore be hardly identifiable by the vast majority of the public, as it rather resembles a very fine metal sieve. 

The electrode of the Ni-Cd cell is based on two several centimeters wide strips of deep-drawn ferritic low-carbon steel, the center of which is perforated to ensure contact between the active material in the electrode and the electrolyte itself. One of these strips is formed into the shape of a tray into which the active material is subsequently charged in the gear of the filling line. The second strip closes it from above so that a typically 8-12 meter long rod or lamella filled with active material comes out of the press.

The procedure is the same for both the anode and the cathode, which of course contain different active material. The positive active mass is the size of instant coffee granules, while the negative mass most resembles grains of table salt. The rods are therefore treated before further processing to prevent spontaneous leakage of the mass from the electrodes.

The electrode of a modern Ni-Cd cell consists of several, say fifteen, of these lamellae, which the operator of the next machine stacks side by side, one face up, another face down, and so on. The locks on its edges snap into each other and join the slats into one wide strip. This then goes to a shearer, which cuts it to the required length, i.e. the width of the resulting electrode plate - its length is then determined by the number of lamellae. The machine weighs each plate for inspection before it drops out of the machine into a tray and can go on to assemble the entire cell.

Although the production of electrode plates can be fully automated, there are undeniable advantages in maintaining the human labor involved in the process. In fact, the operator can monitor the process very efficiently, given that careful inter-operational control of production significantly reduces the scrap rate. Thus, it rarely happens that the weighing of a finished plate reveals an inaccurately manufactured piece that has to be scrapped.

This article is part of a series of articles on Ni-Cd production, more of which can be found as links in the top right corner of this page.