R. S. Gumucio Etal Storage Battery
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R. S. GUMUCIO ETAL STORAGE BATTERY V BY April 22, 1969 R. S. GUMUCIO ETAL 3,440,100 STORAGE BATTERY "arzzze 3,440,100 United States Patent Office Patented Apr. 22, 1969 1. 2 3,440,100 very reactive lead dioxide positive electrode, it will be STORAGE BATTERY possible to arrive at several embodiments of potentially Ricardo Salcedo Gumucio and Angel Pascual Ardanuy, reversible, i.e., chargeable and dischargeable, storage bat Madrid, Spain, assignors to Instituto Nacional De Indus teries. Zinc is preferred for this purpose, primarily due to tria, Madrid, Spain the fact that the free energy from the reduction of lead Filed Dec. 13, 1965, Ser. No. 513,200 dioxide by zinc in an acid medium equals about 108.56 Claims priority, application Spain, June 2, 1965, Kcal, corresponding to an electromotive force of about 313,675 nt. CI. H01m 39/00, 41/00 235 volts determined from thermal data, or 2.448 volts U.S. CI. 136—26 12 Claims if the lead dioxide-zinc semi-elements which are shown 10 in the electrochemical couple oxidation-reduction tables are combined, for instance in accordance with the disclos ure in “Oxidation Potentials” by Latimer, second edition, ABSTRACT OF THE DISCLOSURE pp. 340 and 345. Furthermore, a zinc-lead battery will be A storage battery which comprises a housing, at least of considerably lesser weight than a lead battery, since one positive electrode including lead dioxide as active 5 the ratio of electrochemical equivalence between zinc and mass, located in the housing, at least one negative elec lead is 1:3.17. trode including as negative active mass a composite amal However, these advantages of the last described electro gam of silver and of at least one metal selected from the chemical system, which represents a galvanic couple cap group consisting of zinc, cadmium and copper, located in able of Supplying an electromotive force of about 25 the housing spaced from the positive electrode, and an 20 Volts, could not be utilized successfully in view of the ?? acidic electrolyte consisting essentially of sulfuric acid parently unsurmountable difficulties involved in obtaining of effective concentration located in the housing and con complete reversibility of the system, elimination of the tacting the positive and negative electrodes. Self discharge of the negative plate, and maintenance of the charge of the charged battery. «??????, ?????» 25 These difficulties may be subdivided into different The present invention relates to a storage battery and, groups, namely inherent difficulties with respect to the more particularly, to an acidic storage battery of the type permanence of the active matter of the negative electrode; utilizing lead dioxide as the active mass of the positive difficulties concerning the nature and material of the Sup electrode. port portion of the electrode such as a wire mesh, grid It has been attempted to form acidic storage batteries 30 ºr plate to which the negative active mass adheres; dif with a zinc-sulfuric acid-lead dioxide galvanic system or ficulties connected with the regeneration of the negative a cadmium-Sulfuric acid-lead dioxide galvanic system. active mass in a compound and firm form during the However, these systems did not meet with technical charging process; and, furthermore, difficulties with re success, particularly due to self discharge of the negative spect to the corrosion resistance of the supporting portion electrode and difficulties connected with recharging such of the negative electrode, especially at the terminal zones batteries, thereof which are exposed to moisture, acid and air. It The earliest attempts to provide such batteries appear has been proposed to maintain zinc, cadmium or, more to have been carried out towards the end of the last cen generally, any other metal which can be attacked by sul tury and at the beginning of the present century by 40 furic acid under formation of a sulfate which is soluble Regnier. Consequently, zinc-sulfuric acid-lead dioxide in the Sulfuric acid, in amalgamated state, because the storage batteries or cells are known as the "Regnier cell.' presence of mercury will considerably increase the over The interest in such systems for storage batteries contin tension of hydrogen on these elements. It was believed lues due to the limitations of the conventional lead acid that an appropriate increase in the degree of amalgamation battery. It is well known that these limitations of the lead of the negative active mass would be sufficient to prevent acid battery include a disadvantageous relationship be Spontaneous chemical dissolution of the negative active tween the weight of such battery and the amount of energy mass and, consequently, to maintain the charge in the that can be stored therein, and also the spontaneous sul storage battery. Although the presence of mercury is re fating of the negative plate which occurs in batteries of quired for this purpose, it must be taken into considera this type if they are not properly operated. In view of 50 tion that the necessarily high degree of amalgamation will these disadvantages of the lead acid battery, it would be give to the amalgamated negative active mass a certain de desirable to use and electrode which is non-sulfatable by gree of flowability or fluidity. This fluidity increases with chemical attack and, if possible, including, or composed an increase in the proportion of mercury in the amalgam of, an element whose electrochemical equivalent would and thus with the advance of the discharge of the battery. be more favorable than that of lead. For reasons of this 55 Thereby, the mechanical structural conditions of the elec kind, alkaline storage batteries, such as nickel-iron, trode are impaired. Normally, the electrode is placed in nickel-cadmium, silver-cadmium and silver-zinc batteries a vertical position, and in this position, liquid amalgam were developed. may flow off the negative electrode and fall onto the However, the old acidic systems of storage batteries bottom of the battery housing. are potentially cheaper and capable of delivering more 60 Furthermore, the electrochemical conditions in the bat electricity than alkaline systems. There are only a few tery are modified during charging since there is an uneven electrochemical systems capable of accumulating energy. distribution of mercury and therefore of active amalgam On the other hand, replacement of the negative electrode at the electrode surface, with a higher concentration of of the lead battery with a soluble sulfate electrode is of mercury at the lower portion of the electrode and a lesser practical interest for two reasons, namely, the elimination 65 concentration of mercury at the upper portion thereof. of chemical sulfating, and the ability to discharge large Thus, non-homogeneous amalgams are formed on the quantities of electric energy from a battery of relatively electrode which will produce local reactions and self small weight. Zinc was primarily investigated, although, discharge. For these reasons, it has been proposed to in addition, cadmium and copper were studied. These arrange negative electrodes so as to extend horizontally three elements form sulfates which are soluble in the acid 70 within the battery housing, thereby causing the quite obvi electrolyte, i.e., in aqueous sulfuric acid, and by com ous mechanical and electrical difficulties connected with bining these metals in the negative electrode with the Such positioning of the negative electrode. Furthermore, 3,440,100 3. 4. due to the reactivity between zinc and cadmium on the one the weight of the battery and the capacity for storing hand and sulfuric acid on the other hand, even with a electric energy in the same. horizontally extending negative electrode of this type, it It is yet another object of the present invention to is not possible to prevent or adequately reduce the speed provide an acidic storage battery with substantially com of the solution of the elements, i.e., zinc or cadmium in plete reversibility of charge and discharge conditions. the acid, and, consequently, self discharge phenomena 5 It is also contemplated according to the present inven where only partially prevented. From a practical point of tion to utilize electrodes which are capable of performing view, replacing zinc by cadmium or copper did not give at the acidity level of conventional lead batteries, i.e., decisive advantages. The use of cadmium, for instance, with aqueous sulfuric acid of between about 25 and 36% reduces the electromotive force down to 2.088 volts with concentration as the electrolyte, in order to assure opti practically the same disadvantages as zinc and higher costs 10 mum performance of the positive lead dioxide electrodes and weight per cell. This more than outweighs the lesser and double sulfation of positive and negative plates. How degree of the self-discharge phenomena which were ob ever, unlike the negative plate of a lead battery, the sul served when using cadmium amalgam instead of zinc fate of the negative plate of the battery of the present in amalgam. The use of copper amalgam has further dis vention will be soluble. advantages, particularly because of the low electromotive If a weak acid is used with the electrolyte, in order to force of only 1.348 volts in the case of copper. prevent the solution of zinc or cadmium, which weak Self-discharge phenomena may also be reduced by using acid is not capable to convert faradically or totally the an acid solution of the sulfate corresponding to the metal equivalent quantity of lead dioxide