Nickel-cadmium secondary batteries

Then, A. B. Lange and others found how a cadmium electrode consumes the oxygen from a positive electrode during overcharging in 1938. Then, G. Neumann and others established the present sealing principle and basic structure of a sealed-type nickel-cadmium secondary battery in 1948. Then, the sealed-type nickel-cadmium secondary battery has come to rapidly spread mainly in the consumer electronic equipment market. 

In Japan, the Furukawa Battery Co., Ltd. industrialized a sintered-type vented nickel-cadmium battery for airplane starting in 1955. The Furukawa Battery Co., Ltd. started mass production of the vented-type nickel-cadmium secondary battery and a sealed nickel-cadmium secondary battery for industrial use in 1962 and developed the same to the fields, such as aircrafts. 

On the other hand, Sanyo Electric Co., Ltd. started mass production of a consumer sealed type nickel-cadmium secondary battery. Then, other companies produced a consumer sealed-type nickel-cadmium secondary battery commercially one after another. Then, the batteries have been used as the main power supply of portable electronic devices such as cordless power tools and toys, video cameras, and notebook PCs in 1980s, and the production amount has enlarged drastically. 

The nickel-cadmium secondary battery contains NiOOH/nickel hydroxide as a positive active material, cadmium/cadmium hydroxide as a negative active material, and an aqueous solution containing potassium hydroxide as the main component as an electrolyte. Generally the charge-and-discharge reaction is shown in the following formulas 1, 2 and 3. 

The electrodes of the nickel-cadmium secondary battery are classified into pocket type, sintered type, and pasted type according to those manufacturing methods. Moreover, the batteries... 

The pasted-type electrode is developed in order to design a small and lightweight nickel-cadmium secondary battery. Main production methods of the pasted-type electrode include a method of applying to a nickel-coated steel sheet with perforations and a method of filling up a sponge-like nickel substrate. 

Thus, it is necessary to have a vent valve for releasing the gas. Moreover, since alkaline mist splashes from the electrolyte in the battery with gas venting, the vent valve has a splash proof structure which prevents diffusion of mist. The nickel-cadmium secondary battery with such a structure is referred to as the vented-type cell. 

The vented-type battery needs to perform water addition in which water consumed by electrolysis is periodically added. However, in recent years, the vented-type nickel-cadmium secondary battery which has reduced the water addition frequency is produced commercially for trains and the like. The battery controls the electrolysis of the water under float charging by using the pasted-type cadmium electrode which has a high hydrogen overpotential characteristic for the negative electrode. 

A nickel-cadmium secondary battery with the type of the gas recombination by catalyst in which oxygen and hydrogen gas generated in the end of charging are made to react and return to water by providing a catalyst to the vent valve is used partly. 

I. Y. Sato, K. Ito, T. Arakawa and K. Kobaya Kawa Possible Causes of the Memory Effect Observed in Nickel-Cadmium Secondary Batteries. J. Electrochemical Society, 143 L225 (October 1996). 

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