Functionalized short chain fluorinated polyether based electrolytes for safe lithium batteries and the cells having the same

Abstract

Non-flammable electrolyte compositions for lithium metal primary batteries and the cells containing these electrolytes are described. The electrolyte compositions comprise one or more partially or fully fluorinated functionalized short chain polyethers with one or more lithium salts, and may include one or more cosolvents, and may have one or more fire retardants added. Said short chain functionalized fluorinated polyethers have much better ionic conductivity than the alkyl terminated fluorinated polyethers or long chain perfluoropolyethers, which provide superior flame resistance without sacrificing overall battery performance. Heat resistant, non-flammable primary lithium cells are also disclosed.

Claims

1. A fire resistant, non-flammable and stable electrolyte composition for lithium primary batteries, which electrolyte composition contains at least one functionalized fluorinated short chain polyether which has a general structure represented by formula: R(C.sub.xF.sub.2xyH.sub.yO).sub.mR, wherein x, y and m represent integers with x=1 to 3, y=0 to 2x1, m=1 to 9, and R, R represent functional groups, selected from the group consisting of esters, carbonates, carboxylic acids, alcohols, nitriles, amines, amides, lactones, lactams, sulfates, sulfonates, sulfones, sultones, phosphates, phosphites, phosphonates, and phosphazenes, and said polyether is present from trace amount to 90% (percent) by weight.

2. A fire resistant, non-flammable and stable electrolyte composition for lithium primary batteries as described in claim 1, further comprising at least one lithium salt, at least one short chain polyether and a cosolvent.

3. A fire resistant, non-flammable and stable electrolyte composition as described in claim 1, wherein said functionalized fluorinated polyether defined as terminal groups in the polymers containing functional groups selected from the group consisting of esters, carbonates, carboxylic acids, alcohols, nitriles, amines, amides, lactones, lactams, sulfates, sulfonates, sulfones, sultones, phosphates, phosphites, phosphonates, and phosphazenes.

4. A fire resistant, non-flammable and stable electrolyte composition as described in claim 2, in which said cosolvent is selected from the group consisting of esters, carbonates, carboxylic acids, alcohols, nitriles, amines, amides, lactones, lactams, sulfates, sulfonates, sulfones, sultones, phosphates, phosphites, phosphonates, and phosphazenes.

5. A fire resistant, non-flammable and stable electrolyte composition as described in claim 1, in which said lithium salt is selected from the group consisting of LiPF.sub.6, LiBF.sub.4, LiClO.sub.4, LiN(SO.sub.2F).sub.2, LiN(SO.sub.2CF.sub.3).sub.2, LiB(C.sub.2O.sub.4).sub.2, LiBF.sub.2CO.sub.4, LiSO.sub.3CF.sub.3, LiNO.sub.3, and their mixtures.

6. A fire resistant, non-flammable and stable electrolyte composition as described in claim 2, in which said cosolvent is present from trace amount to 80% (percent) by weight.

7. A fire resistant, non-flammable and stable electrolyte composition as described in claim 1, which additionally contains fire retardant materials selected from the group consisting of hydrofluoroethers, phosphites, phosphates, phosphazenes, and their mixtures.

8. An electrolyte composition as described in claim 7, in which said fire retardant materials are present from trace amounts to 40% (percent) by weight.

9. A fire resistant, non-flammable and stable lithium primary battery, having anode(s) cathode(s), and separator(s), which battery contains therein a fire resistant, non-flammable and stable electrolyte composition, as described in claim 1.

10. A fire resistant, non-flammable and stable lithium primary battery, as described in claim 9, in which said cathode(s) material is selected from the group consisting of V.sub.2O.sub.5, CF.sub.x, FeS.sub.2, MnO.sub.2, C/S and C/Air.

11. A fire resistant, non-flammable and stable lithium primary battery, as described in claim 9, in which said separator(s) material is high temperature resistant aramid fibers non-woven.

12. A fire resistant, non-flammable and stable lithium primary battery, as described in claim 9, in which said cathode has binder of polyamide material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) FIG. 1 contains images of cell conditions under Wedge (Puncture) Test and Bullet Test, showing the cells containing conventional electrolyte (with ether and lactone solvents) which failed the two tests, and the cells with FFPE containing electrolyte which passed the two tests without any smoke or flame throughout the test time.

(3) FIG. 2 is a voltage vs. capacity plot of the cell with conventional flammable electrolyte and the cell with FFPE containing nonflammable electrolyte of the invention, both having CF.sub.x cathodes.

(4) FIG. 3 is a voltage vs, capacity plot of the cell with conventional flammable electrolyte and the cell with FFPE containing nonflammable electrolyte of the invention, both having V.sub.2O.sub.5 cathodes.

(5) FIG. 4 is a vertical sectional view of a battery constructed in accordance with the invention, and

(6) FIG. 5 is a top sectional view of a battery constructed in accordance with the invention.

(7) 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

(8) 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 the same way to bring about the same result.

(9) An electrochemical device, such as lithium primary battery typically includes a lithium metal anode(s), and a current collector tab in contact with the anode(s), a cathode(s) capable of accepting lithium ions upon discharge, and a current collector in contact with the cathode(s), separator(s), and an electrolyte in contact with the anode(s), cathode(s), and separator(s) with the whole assembly contained in a moisture proof enclosure with exiting sealed terminals electro-conductively connected to the collectors and the electrodes. It is highly desirable that this battery is heat resistant and non-flammable in all environmental conditions and especially in hot environments or under abuse by overloads or shorts, where conventional batteries are particularly unsafe. The non-flammability is mainly achieved by inclusion of a non-flammable electrolyte therein, but the electrolyte must be also highly ionically conductive within a wide temperature span, so that the battery can perform satisfactorily in these extreme conditions, primarily in military applications.

(10) Preferred electrolytes of the invention, which achieved the characteristics described above contain at least one functionalized, partially or fully fluorinated short chain polyether (FFPE), which may be in combination with a cosolvent from trace amount to 80% (percent) by weight, and the cosolvent is selected from the group consisting of esters, carbonates, nitriles, imides, lactones, sulfones, sulfonates, sulfolanes, sultones, ionic liquids, and their mixtures. These compositions also have at least one lithium salt added, which salt is selected from the group consisting of LiPF.sub.6, LiBF.sub.4, LiClO.sub.4, LiN(SO.sub.2F).sub.2, LiN(SO.sub.2CF.sub.3).sub.2, LiB(C.sub.2O.sub.4).sub.2, LiSO.sub.3CF.sub.3, LiNO.sub.3, and their mixtures. The more preferred cosolvents are gamma-butyrolactone and a dinitrile, such as succinonitrile. The more preferred salts are LiBF.sub.4, LiN(SO.sub.2CF.sub.3).sub.2 and LiN(SO.sub.2F).sub.2.

(11) The short chain polyether has preferably a general structure represented by the following formula: R(C.sub.xF.sub.2xyH.sub.yO).sub.mR wherein x, y and m represent integers with x=1 to 3, y=0 to 2x1, and m=1 to 9 and R, R represent functional groups selected from the list of esters, carbonates, carboxylic acids, alcohols, nitriles, amines, amides, lactones, lactams, sulfates, sulfonates, sulfones, sultones, phosphates, phosphites, phosphonates, and phosphazenes. The more preferred functional groups are methyl carbonate, N,N-dimethyl amide, and propylene carbonate. The chemical structure of the electrolyte solvent may contain one or more polymer units (i.e. co-polymers) defined in the formula backbone and/or branch sections, wherein the functionalization of the fluorinated polyethers are defined as such by the presence of functional groups in the chemical structure of the electrolyte solvent such as esters, carbonates, carboxylic acids, alcohols, nitriles, amines, amides, lactones, lactams, sulfates, sulfonates, sulfones, sultones, phosphates, phosphites, phosphonates, and phosphazenes.

(12) To provide an additional fire quenching mechanism, fire retardants, such as hydrofluoroethers, phosphites, phosphates and phosphazenes from trace amounts to 40% (percent) by weight may be added.

(13) In order to compare the non-flammable electrolyte of the invention with prior art typical flammable electrolyte with gamma-butyrolactone (GBL) and dimethyl ether (DME), the following examples of electrolyte compositions has been made.

(14) TABLE-US-00001 EXAMPLE #1: EXAMPLE #2 (Flammable electrolyte) (Electrolyte of the invention) 1.2M LiBF.sub.4 in GBL/DME (1:1) 1.0M LiBF.sub.4 in FFPE/GBL (70:30)

(15) Wedge (Puncture) tests and bullet tests were performed at room temperature on primary CF.sub.x cells with electrolytes EXAMPLE #1 and #2, to evaluate the flammability. The cells filled with EXAMPLE #1 electrolyte exploded immediately in both tests. The cells filled with example #2 electrolyte did not catch on fire at all. Images of test results are shown in FIG. 1, which is one embodiment of the invention.

(16) To evaluate the electrochemical performance, identical primary CF.sub.x cells were activated by the two electrolytes (Example #1 and #2). The performance of the cells is shown in FIG. 2, which is another embodiment of the invention. The result shows that the FFPE containing non-flammable electrolyte does not have negative impact on cell performance in comparison to flammable electrolyte.

(17) Additionally, Identical primary V.sub.2O.sub.5 cells were also activated by the two electrolytes (Example #1 and #2). The performance of the cells is shown in the FIG. 3, which is another embodiment of the invention. The result again shows that the FFPE containing non-flammable electrolyte does not have negative impact on cell performance in comparison to flammable electrolyte.

(18) Referring now to the drawings FIG. 4 and FIG. 5, the non-flammable electrolyte containing cell or battery 10 is therein illustrated, which is shown as a prismatic bi-cell, which is another embodiment of the invention. The cell 10 has a cathode 11 in the middle and comprises preferably aluminum grid or foil collector 11A coated with cathode particles, plus Super-P, Ketjen Black, or graphene attached and held together by a heat resistant binder, preferably polyamide. Two porous insulating separators 12 are placed on both sides of the cathode 11, and soaked by electrolyte 13 described above, as well as the cathode is soaked by the electrolyte, all under argon or other inert atmosphere. The separators are preferably of heat resistant aramid fibers non-woven material. Two anodes 14 of lithium foils or plates are placed on and in contact with the separators 12; and the electrolyte 14, and have preferably nickel grid tabs terminal 15 electro-conductively attached to the lithium foils. This cell or battery 10 is enclosed in a moisture proof enclosure 16 with the terminals 15 existing in a sealed and insulated manner. The terminals 15 are preferably full width of the lithium electrode, as shown. The cathode aluminum current collector 11A also exists from the enclosure 16 in a sealed and insulated manner, or optionally may have electro conductively attached another full width terminal tab 17 of nickel grid or foil, existing in sealed and insulated manner. The cell 10 maybe heat sealed in flexible metal foil and plastic enclosure 16 under vacuum, which provides atmospheric pressure for the outside and thus for good contacts of all components, or the enclosure is made from a tight and hard metal structure to hold the cells together (not shown).The bi-cell depicted, could also be reversed with anode in the middle and two cathodes on the outside; or it can be a well-known single cell structure (not shown). Also, several single or bi-cells may be placed in the enclosure 16 and connected electrically in parallel (not shown). The cathode material 11 is preferably V.sub.2O.sub.5, but other materials suitable for insertion of lithium upon discharge can be used, such as CF.sub.x, FeS, MnO.sub.2, and sulfur mixed with carbon (C/S). Other cell constructions can be used for containing this non-flammable electrolyte, such as rolled cylindrical and flat wound cells, and lithium air type cells (not shown), while using the same heat resistant materials. It has also been discovered, that the described electrolytes are resistant to oxidation, which makes them particularly suitable for lithium-air cells, and that they can also be used in lithium-ion type cells.

(19) It will thus be seen, that electrolyte compositions and cells constructions have been provided with which the objects of the invention are achieved.