Non-aqueous ammonia electrolytes for lithium anode based primary and reserve batteries

Abstract

Novel, non-aqueous, high salt concentration ammonia based electrolytes, compatible with lithium based anodes are described therein. Said electrolytes are supporting higher voltage provided by novel cathodes and lithium based anodes, which results in high power density batteries over prior art. Various cathodes, separators and cell constructions are also disclosed.

Claims

1. A non-aqueous ammonia based electrolyte for lithium metal anode based reserve batteries, comprising non-aqueous ammonia NH.sub.3 with at least one salt selected from the group including LiBF.sub.4, LiPF.sub.6, LiTFSI, LiSCN, NH.sub.4SCN, KSCN and LiNO.sub.3 dissolved therein.

2. A non-aqueous ammonia based electrolyte as described in claim 1, which electrolyte has a high salt concentration of at least 20%.

3. A non-aqueous reserve battery having ammonia based electrolyte with an electrolyte salt concentration above 20%, a lithium metal based anode(s), a porous non-conductive separator(s) and a cathode(s), which cathode's active materials are selected from the group including persulfate salt, manganese oxide, a permanganate, meta-dinitrobenzene and mixtures thereof.

4. A non-aqueous reserve battery having ammonia based electrolyte and lithium metal based anode as described in claim 3, in which said cathode active material is a persulfate salt, which has a general structure represented by the formula: X.sub.2S.sub.2O.sub.8, wherein X is representative of a cation with an ionic charge 1+ (such as Na.sup.+, K.sup.+, NH.sub.4.sup.+) with associated anion of S.sub.2O.sub.8.sup.2−.

5. A non-aqueous battery as described in claim 3, in which said cathode active material with a binder and conductive carbon powder is coated on a conductive current collector.

6. A non-aqueous battery as described in claim 3, in which said cathode active material with a fibrous binder and carbon conductive powder included therein is in a pad form, and said pad is in contact with a conductive substrate material.

7. A non-aqueous battery as described in claim 3, in which said cathode active material with a binder and conductive carbon is in a free-standing form casted onto a conductive substrate material.

8. A non-aqueous battery as described in claim 3, in which said cathode active material with a binder and conductive carbon is pressed onto a conductive substrate material.

9. A non-aqueous reserve battery as described in claim 3, which battery has horizontally stacked flat circular electrodes.

10. A non-aqueous reserve battery as described in claim 3, which battery is in a cylindrical form having said cathode wound.

11. A non-aqueous battery as described in claim 3, in which battery said separator(s)' material is a porous glass non-woven paper.

12. A non-aqueous battery as described in claims 3, in which battery said separator(s)' material is a porous cellulose fiber paper.

13. A non-aqueous battery as described in claim 3, in which battery said separator(s)' material is a porous polymer film.

14. A non-aqueous battery as described in claim 3, in which battery said separator(s)' material is replaced by a solid state ion conducting material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The nature and characteristic features of the invention will be more readily understood from the following description taken in connection with the accompanying drawing forming part thereof, in which:

[0028] FIG. 1 is a sectional side elevational view of cylindrical ammonia based primary or reserve battery, having flat circular electrodes and the electrolyte in the ampoule placed on top of the cells.

[0029] FIG. 2 is the image that was taken 1 minute after a piece of lithium metal was dropped into a liquid ammonia that was cooled in acetone-dry ice bath (at about −78° C.) before the image was taken. The deep blue color indicates the formation of solvated electron-lithium blue.

[0030] FIG. 3 includes the images that were taken (a) 1 minute and (b) 8 minutes after a piece of lithium metal was dropped into a saturated solution of KSCN in liquid ammonia that was cooled in acetone-dry ice bath (at about −78° C.) before the images were taken.

[0031] FIG. 4 is a discharge time (first 100 seconds) versus voltage diagram for cells made with ammonia persulfate cathodes and lithium anodes, activated with ammonia electrolyte having various KSCN concentrations, and discharged at 40 mA/cm.sup.2.

[0032] FIG. 5 is a discharge time (first 100 seconds) versus voltage diagram for cells made with ammonia persulfate cathodes, with magnesium and lithium based anodes, activated by 48% KSCN/NH.sub.3 electrolyte, and discharged at 40 mA/cm.sup.2.

[0033] It should, of course, be understood that the description and drawings herein are merely illustrative, and that various modifications and changes can be made in the compositions and the structures disclosed without departing from the spirit of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] When referring to the preferred embodiments, certain terminology will be utilized for the sake of clarity. Use of such terminology is intended to encompass not only the described embodiments, but also technical equivalents, which operate and function substantially same way to bring about the same results.

[0035] Referring now to the FIG. 1, which is one embodiment of the invention, showing ammonium based low temperature primary or reserve battery 1 of the invention, as an example, which battery comprises: a circular lithium foil anode 2; in contact with a cylindrical metal enclosure/current collector 3; a cathode 4, such as persulfate based salt like (NH.sub.4).sub.2S.sub.2O.sub.8, or K.sub.2S.sub.2O.sub.8, or Na.sub.2S.sub.2O.sub.8, or coated on a tabbed stainless steel collector 5 and in contact with the cathode 4; a separator 6, such as 90% porous non-woven glass paper, between said anode 2 and cathode 4; and an electrolyte 7, such as ammonia NH.sub.3 with a salt like KSCN dissolved therein, and the electrolyte is stored in a separate pressure ampoule 8, preferably of a glass material, placed next to the battery components 2 and 6. The cathode 4 with collector 5 is insulated by non-conductive ring 9.

[0036] The battery 1 is sealed dry in moisture-proof metal enclosure 3, with metal plug 10, insulating layer 11, and positive metal pin 12, welded to the collector 5 and sealed by glass seal 13. The battery 1 is activated by mechanically punching the wall of the ampoule 8. The activation is done only when the battery 1 is needed to power a device.

[0037] The battery may be multi-celled with the cells connected in parallel. (not shown).

[0038] All structures are heat and pressure and corrosion resistant.

[0039] Other cells' constrictions may be also used with the electrolyte of the invention, as described in our prior patent application Ser. No. 17/300,205, and in prior art U.S. Pat. Nos. 3,45,295; 3,032,284 and 3,943,001, which are hereby incorporated by reference.

[0040] The cathodes 4 described in FIGS. 1 may be coated on the collector 5 by well known various methods via a slurry comprising the active material, plastic binder, and conductive carbon powder in a solvent, which solvent evaporates after coating. Additionally, the described material persulfate salt of the cathode 4 may be replaced by molybdenum oxide, a permanganate, meta-dinitrobenzene, or their mixtures.

[0041] The battery electrolyte of the invention is ammonia-based non-aqueous electrolyte, and comprises NH.sub.3 solvent with at least one salt selected from the group including: LiPF.sub.6, LiBF.sub.4, LiTFSI, LiSCN, NH.sub.4SCN, KSCN and LiNO.sub.3, dissolved therein with salt concentration ranging from 10% to 80%, which is another embodiment of the invention.

[0042] The cathode's persulfate salt of the invention has a general structure represented by the formula: X.sub.2S.sub.2O.sub.8, wherein X is representative of a cation with an ionic charge 1+ (such as Na+, K+, NH.sub.4+) with associated anion of S.sub.2O.sub.8.sup.2−.

[0043] The cathode active materials may have a fibrous binder with conductive carbon powder and may be also in a pad form, and said pad is in contact with a conductive substrate, which is another embodiment of the invention.

[0044] In another embodiment of the invention, the cathode active materials with a binder and conductive carbon powder may be in a free-standing form, casted onto a conductive substrate.

[0045] In another embodiment of the invention, the cathode active materials with a binder and conductive carbon powder may be as a free-standing sheet pressed onto a conductive substrate.

[0046] The separators in the described batteries of the invention may be also made from a porous polymer, or a porous cellulose paper, or a solid state ion conductive film.

[0047] FIG. 2 shows the formation of lithium blue when lithium is in contact with ammonia.

[0048] FIG. 3 demonstrates that lithium is stable in concentrated KSCN/NH.sub.3 solution. No lithium blue was observed even after 8 minutes.

[0049] FIG. 4 indicates the load voltage is greatly improved when a higher salt concentration electrolyte is used.

[0050] FIG. 5 shows the lithium anode based cell has higher voltage than the magnesium anode based cell. The load voltage gain is more than 0.5 V when replacing magnesium anode with lithium anode.

[0051] It will thus be seen that the high salt concentration ammonia electrolyte can improve its compatibility with lithium and provides high voltage and high power density. Thus lithium based ammonia batteries have been provided herein, with which the objects of the invention are achieved.