The Negatives in Storage Batteries

Posted By Richard Jefferson on 01 December 2014

Posted in The Vintage Machinery Almanac

This article was originally published in Electrochemical and Metallurgical Industry Publication of April 1907. Information within this article is therefore correct as of 1907. The publication of this material aims to provide historical insight on the subject and its place in industry.

The number of battery inventions and patents is legion. But very few have marked important industrial progress. It is, therefore, a pleasure to call attention to one patent of Mr. Joseph Bijur, abstracted in the "Analysis of Current Electrochemical Patents," since it may be conservatively said that the process described in it looks very promising. It serves the highly useful purpose of preventing the loss of capacity of the negatives (lead plates) in the lead storage battery. For many years the life of a lead cell has been limited by the condition of its negatives. The loss of capacity of the negatives in time during service is a fact. As a remedy, negative plates after having lost part of their capacity have been used as positives (peroxide plates) and have recovered. But this needs careful and skilled attendance. What then is the cause of the trouble with the negatives?

The chemical reaction which yields the electric current takes place at the contact surfaces of the active-mass particles with the acid in its pores. The active mass with its containing electrolyte is the stomach, heart and soul of the battery. The electrolyte outside of the pores represents only a reservoir of food, from where a fresh supply is dispatched when needed to the place where it is needed, that is, into the pores within the active mass. It is, therefore, an essential necessity that the active mass be thoroughly porous and remain so during service. On the other hand, for simple mechanical reasons, the active mass must be hard, tough and coherent, able to withstand expansion and contraction; it must be firmly attached to the support of the plate so that no particles may drop off or insulating sulphate layers form between support and active mass. These two fundamental conditions—porosity and tough coherency of the active mass—appear to be contradictory, and their simultaneous fulfillment represents an important problem of lead storage battery manufacture. In the case of the negatives, the loss of capacity may be due to the formation of the insulating sulphate layer mentioned above, or to the dropping off of active material from the grid. But even if care is taken in the construction of the plate to prevent this to occur, there has, nevertheless, always occurred a loss of capacity in the lead storage battery, due to a contraction of the pores of the mass, the plate shrinks, it loses its porous consistency and solidifies partly into solid lead. This means, of course, an enormous reduction of the active surface, which directly explains the loss of capacity. The problem is, therefore, briefly, to maintain the porous consistency of the plate during service.

Mr. Bijur attains the same end in a peculiarly direct manner. He reinforces the porous structure of the active mass by means of inert matter, just as concrete buildings are reinforced with steel. His plate has a solid metallic support as foundation, and upon it is built a porous structure of particles of active mass, reinforced by carbon particles which are chemically inert, and serve the sole purpose of holding the active-mass particles in their original condition of porous consistency. The idea is beautifully simple. But the means to attain this end would appear at first sight extremely difficult. The real remarkable feature of Mr. Bijur's process is the extreme simplicity and directness by which he introduces the reinforcing carbon particles afterwards, after the plate has been formed, by introducing sugar and carbonizing it. It is clear that if too much carbon is introduced in this way the carbon will clog the pores and will make matters worse. To be efficient the carbon particles introduced must be just enough to give sufficient strength to the structure, but they should not reduce in any essential degree the active surface of the lead particles. Since this lead storage battery has been in practical use for a year it appears that Mr. Bijur has found the exact conditions of accomplishing his end. The method certainly deserves most careful attention.

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