Lithium-Ion Cell

Abstract

A lithium-ion cell includes two working electrodes which are located opposite one another and have different polarities and between which a separator which electrically insulates the working electrodes with respect to one another and is permeable to lithium ions is arranged in an electrolyte space. A lithium-containing reservoir electrode is in contact with the electrolyte space in such a way that electronic isolation is provided and lithium ions are exchanged, wherein by way of a measuring and control circuit which connects the reservoir electrode to at least one of the working electrodes a voltage can be measured between the reservoir electrode and the working electrode and a voltage can be applied between the reservoir electrode and the working electrode. The reservoir electrode is of porous design and is arranged between two insulation layers of the separator which provide electronic isolation and are permeable to lithium ions.

Claims

1. A lithium-ion cell comprising: two working electrodes situated opposite one another and having different polarities; a separator arranged in an electrolyte space between the two working electrodes, the separator electronically insulating the two working electrodes from one another and being permeable to lithium ions; a lithium-containing reservoir electrode in contact with the electrolyte space such that electronic insulation is provided and lithium ions are exchanged; a measuring and control circuit connecting the reservoir electrode to at least one of the two working electrodes, wherein a voltage is measurable between the reservoir electrode and the at least one working electrode and further wherein a voltage is appliable between the reservoir electrode and the at least one working electrode, wherein the separator comprises two insulation layers that provide electronic insulation and are permeable to lithium ions, and the reservoir electrode has a porous design and is arranged between the two insulation layers of the separator.

2. The lithium-ion cell according to claim 1, wherein the reservoir electrode comprises an electrically conductive polymer material to which a lithium-containing application material is applied.

3. The lithium-ion cell according to claim 2, wherein the electrically conductive polymer material comprises a polyaniline, a polypyrrole, or a polythiophene.

4. The lithium-ion cell according to claim 3, wherein the lithium-containing application material comprises lithium iron phosphate (LiFePO.sub.4).

5. The lithium-ion cell according to claim 2, wherein the lithium-containing application material comprises lithium iron phosphate (LiFePO.sub.4).

6. The lithium-ion cell according to claim 2, wherein the lithium-containing application material comprises metallic lithium.

7. The lithium-ion cell according to claim 3, wherein the lithium-containing application material comprises metallic lithium.

8. The lithium-ion cell according to claim 1, wherein the two insulation layers of the separator comprise polyethylene or polypropylene.

9. The lithium-ion cell according to claim 2, wherein the two insulation layers of the separator comprise polyethylene or polypropylene.

10. The lithium-ion cell according to claim 2, wherein the polymer material of the reservoir electrode is in a form of a porous membrane.

11. The lithium-ion cell according to claim 10, wherein polymer materials of the two insulation layers are in a form of porous membranes.

12. The lithium-ion cell according to claim 2, wherein polymer materials of the two insulation layers are in a form of porous membranes.

13. The lithium-ion cell according to claim 2, wherein the polymer material of the reservoir electrode is in a form of a stretched film.

14. The lithium-ion cell according to claim 13, wherein polymer material of the two insulation layers are in a form of stretched films.

15. The lithium-ion cell according to claim 2, wherein polymer material of the two insulation layers are in a form of stretched films.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0018] FIG. 1 is a schematic illustration of a lithium-ion cell according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWING

[0019] FIG. 1 is a schematic illustration of a lithium-ion cell 10 according to an embodiment of the invention. The cell 10 has a first, negative working electrode 12 and a second, positive working electrode 14. An electrolyte space 16 which is filled with an electrolyte which, in particular, also impregnates the working electrodes 12, 14, is located between the working electrodes 12, 14. A separator 18 is arranged in the electrolyte space 16, the primary task of said separator being that of electronically insulating the working electrodes 12, 14 from one another and, at the same time, allowing lithium ions to flow through the electrolyte space 16. The working electrodes 12, 14 are formed from materials which allow reversible binding or intercalation of lithium ions which can move freely in the electrolyte. An extremely wide variety of materials of which the different properties have an effect on the operating properties of the cell 10 are known to a person skilled in the art in this respect.

[0020] As outlined in the introductory part, an intermediate layer 20 can be deposited between the first electrode 12 and the electrolyte space 16 during operation of the cell 10, in particular during the first charging and discharging cycles of said cell, wherein lithium ions accumulate in the layer 20 and are withdrawn from the electrochemical process.

[0021] The separator 18 is designed in a particular way in order to replace lithium ions which are lost in such a way or in some other way. For example, in the illustrated exemplary embodiment, the separator 18 comprises two outer insulation layers 181 which are preferably composed of a polymer which provides electrical insulation and is permeable to lithium ions, in particular polyethylene or polypropylene. In this case, the insulation layers 181 are preferably in the form of stretched films. The insulation layers 181 electronically isolate the working electrodes 12, 14.

[0022] A reservoir electrode 182 is arranged between the insulation layers 181. The reservoir electrode 182 is in the form of an electrically conductive polymer layer 183 in which a lithium-containing application material 184 is embedded in the illustrated embodiment. By way of example, the lithium-containing application material 184 is composed of lithium iron phosphate, for example in the form of embedded nanoparticles.

[0023] The reservoir electrode 182 is connected to the working electrodes 12, 14 by way of a measuring and control circuit 22. The measuring and control circuit 22 is designed such that it can be used to measure a voltage between the reservoir electrode 182 and one of the working electrodes 12, 14, indicated by the voltmeter symbol “V”. In addition, it is possible to apply a voltage U between the reservoir electrode 18 and one of the working electrodes 12, 14 by way of the measuring and control circuit 22. As a result, an electron current which runs across the measuring and control circuit 22 from the reservoir electrode 18 to one of the working electrodes 12, 14 can be triggered, this resulting in a corresponding lithium ion current from the reservoir electrode 18 into the electrolyte space 16. Lithium which is stored in the intermediate layer 20 can be replaced in this way. The level and duration of the voltage required for this purpose can be determined on the basis of a preceding voltage measurement between the reservoir electrode 18 and the working electrodes 12, 14, wherein the reservoir electrode 18 serves as a reference electrode in this case.

[0024] It goes without saying that the embodiments which are discussed in the specific description and shown in the figures are only illustrative exemplary embodiments of the present invention. In light of the present disclosure, a person skilled in the art is provided with a broad spectrum of possible variations. In particular, a person skilled in the art can of course vary the specific design of the reservoir electrode. For example, embodiments in which an electrically conductive carrier material is coated with the lithium-containing application material only on one side are also feasible.

LIST OF REFERENCE SYMBOLS

[0025] 10 Lithium-ion cell [0026] 12 First working electrode [0027] 14 Second working electrode [0028] 16 Electrolyte space [0029] 18 Separator [0030] 181 Insulation layer [0031] 182 Reservoir electrode [0032] 183 Electrically conductive polymer layer [0033] 184 Lithium-containing application material [0034] 20 Intermediate layer [0035] 22 Measuring and control circuit

[0036] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.