Patented July 6, 1954 2,683,102 UNITED STATES PATENT OFFICE 2,683,102 ELECTROLYTE FOR ALKALINE STORAGE BATTERIES Roger S. Coolidge, New York, N. Y. No Drawing. Application March 23, 1951, Serial No. 217,291 13 Claims. (C. 136-154) 1. 2 This invention relates to a novel structure of NaOH, KOH, RbCH, CSOH, and consist in part an electrical battery and to an improved elec of increasing conductance; decreasing degree of trolyte for this battery. More in particular, the ionic hydration, ionic heat of hydration, and invention relates to a battery which functions ionic viscosity resulting in greater percentage ca successfully at sub-zero temperatures, and es 5 pacity at lower temperatures; also lowering eu pecially the invention relates to an improved al tectic freezing point; increasing activity coeffi kaline electrolyte for Such batteries for Operat cients; and other advantageous features. These ing at relatively low temperatures. increasingly advantageous qualities are also de It is well known that many of the present elec sirable for ordinary use of electrolytes in electric tric batteries which include sodium hydroxide or 10 batteries, because they provide the means for a, potassium hydroxide as one of the ingredients of more active performance and efficiency of the the electrolyte does not efficiently operate at rela battery. tively cold temperatures, and especially in sub In view of these particular advantages of the Zero temperatures. various alkali hydroxides in the order of their It is the desire of this invention to provide a magnitude, the preferred amount of rubidium battery which operates successfully at relatively or cesium hydroxide employed in this invention cold temperatures, and at any selected Sub-Zero is a complete substitution of cesium hydroxide temperature. It has been found that such effec (rather than rubidium hydroxide, which is more tive operation of a battery having an alkaline expensive and less active) for the usual potassium electrolyte can be greatly improved by substitut 20 hydroxide now employed in an alkaline electro ing, in toto or in part in the electrolyte, the so lyte. dium hydroxide or potassium hydroxide by ru However, a less than complete substitution may bidium hydroxide or cesium hydroxide, or by mix also be employed in accordance with this inven tures thereof. tion as described in the preceding paragraph, par Also, it is possible in this invention to prepare ticularly when it is preferred to sacrifice some the electrolyte with a certain amount of rubidium of the maximum advantages obtainable by this hydroxide or cesium hydroxide or combinations invention in favor of a proportionate lowering of of them in it. So as to have the battery give excel cost of the electrolyte. - lent operating results at a specific low tempera As to the preferred concentration of the ru ture. Such an electrolyte may or may not also bidium or cesium hydroxide in the aqueous so have Some Sodium hydroxide or potassium 30 lution of the electrolyte of this invention, this droxide in it. concentration may lie between 5% and 60% by : In the experimental and commercial develop weight of the electrolyte solution. However, more ment of electric storage batteries, great difficul preferably this concentration should be at least ties have been encountered in their cold weather . equal to the mol fraction of the potassium or operation, particularly at Sub-Zero temperatures. other hydroxide it replaces, and, if greater, not The capacity of such batteries to function effi more should be added than that required to pre ciently decreases very markedly with fall in went freezing at a selected Sub-normal tempera temperature, so that at -65° F., most storage ture contemplated for operation of the electro batteries are apt to be practically useleSS. lyte of the battery. In substituting the rubidium This invention in general is based on the dis hydroxide or cesium hydroxide, or the combina covery of Ruben and others that broadly the tion of them, for any of the other hydroxides like usual alkaline electrolyte used in such types of potassium, it is possible that a complete substi storage batteries, such as an electrolyte contain tution can be made. ing potassium hydroxide as its principal ingredi In employing the rubidium hydroxide or cesium ent, may have substituted for such hydroxide in : 5 hydroxide or a mixture of both in the electro whole or in part other hydroxides of metals be lyte, it is desirous to include sufficient percentage longing to the same Period I A of the Periodic of either or both of these hydroxides in the Classification of ElementS. However, in Some re total Solution of the electrolyte to obtain success spects the hydroxides of Period I A metals in ful operation of the battery and to prevent freez aqueous solutions tend to have improving electro ing at Sub-Zero temperatures. For example, in lytic qualities of particular advantage for low the event it is desirable to have the battery work temperature use. These qualities tend to improve in good practical manner, for instance, at -50 in going from one hydroxide to another in the C., all or part of the normal potassium hydroxide order of their molecular weights, namely, LiOH, in the Solution may be substituted by a desired 2,683,102 3 g percentage concentration of the rubidium hy ing a negative electrode, a positive electrode, and droxide or cesium hydroxide Or a mixture thereof. an alkalin electrolyte having cesium hydroxide The concentration of rubidium. Or Cesium hydrox as the major alkali hydroxide Constituent of Said ide to be added to the electrolyte or Substituted electrolyte. therein, may be varied depending upon the de 9. A rechargeable electric storage battery of sired efficiency of operation at the above ten the nickel-cadmiurn or nickel-iron type, COImpris perature, or at a Selected temperature, ing a negative electrode, a positive electrode, and It Will be. Seen from the foregoing presentation an alkalin electrolyte having rubidium hydroxide that there is an electrolyte material which en as the major alkali hydroxide constituent of Said ploys the hydroxides of rubidium and cesium in O electrolyte. the electrolyte of any type of battery, be that: 10. A rechargeable electric storage battery of battery of the Edison type or of the nickel-cad the nickel-cadinium or nickel-iron type, compris mium type, or any other type of alikaline battery. ing a negative electrode, a positive electrode, and It Will also be seen that an inproved electric an alkalin electrolyte having a total of Cesium battery is provided that successfully functions at 5. hydroxide and rubidium hydroxide Constituting OW temperatures. In addition, it will be noted the major alkali hydroxide constituent in Said that the electrolyte may be: a combination of electrolyte. rubidium hydroxide, or cesium hydroxide, With 11. A rechargeable electric Storage battery of a Solvent, Such aS, for example, Water; or nay the nickel-cadmium or nickel-iron type, Compris be a mixture of rubidium hydroxide and cesium 20 ing a negative electrode, a positive electrode, and hydroxide with the Water; or, the electrolyte may an electrolyte having an alkali metal hydroxide be composed of a desirable amount of Water With content thereof up to approximately 60% by Several alkali metal hydroxides, and in which Weight of Said electrolyte, said alkali metal hy there may be SOEine rubidium hydroxide or cesium droxide content having rubidium hydroxide. Sub hydroxide or a mixture of the rubidium and Stituted for said alkali metal hydroxide in a nan Cesium hydroxides. When the selected tempera ther equal to the no fraction of the Substituted tures, are not too low, it is quite possible the elec hydroxide. trolyte will contain rubidium and cesium hydrox 12. A rechargeable electric storage battery of ides and some potassium, and possibly some so the nickel-cadmium or nickel-iron type, compris dium hydroxides. 30 ing a negative electrode, a positive electrode, and It will be understood that various rinodifica an electrolyte having an alkali metal hydroxide tions and changes may be made in the preferred content thereof up to approximately 60% by form of the invention herein, and Such modifica Weight of Said electrolyte, Said alkali metal hy tions and changes are to be understood as part droxide content having cesium hydroxide Sub of this invention, as outlined in the following Stituted for said alkali metal hydroxide in a claims. manner equal to the mol fraction of the Substi The invention Cairned is: tuted hydroxide. 1. A Storage battery electrolyte having rubidi 13. A rechargeable electric Storage battery of unn hydroxide as the major alkali hydroxide COin the nickel-cadmium or nickel-iron type, compris Stituent therein. 40 ing a negative electrode, a positive electrode, and 2. A Storage battery electrolyte having cesiuin. an electrolyte having an alkali metal hydroxide hydroxide as the major alkali hydroxide constit content thereof up to approximately 60% by uent therein. weight of said electrolyte, said alkali metal hy 3. A storage battery electrolyte having rubidi droxide content having a total of cesium hydrox unhydroxide and cesium hydroxide wherein the ide...and rubidium hydroxide Substituting for an total of Said hydroxides Constitutes the major alkali metal hydroxide in Said electrolyte, in a alkali hydroxide constituent in Said electrolyte. manner equal to the mol fraction of the Sub 4. An electric storage battery electrolyte hav Stituted hydroxides. ing approximately 5 to 60% by Weight of rubidi um hydroxide therein. References Cited in the file of this patent 5. An electric storage battery electrolyte hav UNITED STATES PATENTS. ing, approximately 5 to 60% by weight of cesium hydroxide therein. Number Nanne Date 6. An electric storage battery electrolyte have 1,137,226 Manchester -------- Apr. 27, 1915 ing a mixture of.