Battery Cell Having a Plurality of Electrode Units in a Common Battery Cell Housing

Abstract

A battery cell has a plurality of electrode units in a common battery cell housing. Each of the electrode units includes a protective film having an inner layer and an outer layer, where the inner layer is arranged on the electrode unit and the outer layer is arranged on the inner layer. The outer layer has a higher melting point than the inner layer.

Claims

1-10. (canceled)

11. A battery cell comprising: a plurality of electrode units in a common battery cell housing, each of the electrode units comprising: a protective film thereon, the protective film including an inner layer and an outer layer, the inner layer being arranged on the electrode unit and the outer layer being arranged on the inner layer, wherein the outer layer has a higher melting point than the inner layer.

12. The battery cell according to claim 11, wherein the inner layer has a lower hardness than the outer layer.

13. The battery cell according to claim 11, wherein the inner layer includes polyethylene or polypropylene.

14. The battery cell according to claim 11, wherein the outer layer includes polyethylene terephthalate or polyimide.

15. The battery cell according to claim 11, wherein the protective film is from 20 μm to 200 μm in thickness.

16. The battery cell according to claim 11, wherein the protective film includes a plurality of openings for penetration of a liquid electrolyte into the electrode unit.

17. The battery cell according to claim 16, wherein the plurality of openings are disposed in an area facing toward a bottom of the battery cell housing.

18. The battery cell according to claim 16, wherein a number of the openings is from 10 to 20.

19. The battery cell according to claim 11, wherein the battery cell is a lithium-ion battery cell.

20. A lithium-ion battery comprising a plurality of the battery cells according to claim 19.

21. A motor vehicle comprising the lithium-ion battery according to claim 20.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] A preferred exemplary embodiment of the technology will be described hereinafter on the basis of the appended drawings. Further details, preferred embodiments, and refinements result therefrom.

[0019] FIG. 1 shows an exploded view of a battery cell according to one exemplary embodiment,

[0020] FIG. 2 shows a cross-sectional view of the electrode units,

[0021] FIG. 3 shows a top view of the protective film on the lower side of an electrode unit, and

[0022] FIG. 4 shows a cross-sectional view of an electrode unit.

[0023] Identical or identically acting components are each provided with the identical reference signs in the figures. The components shown and the size relationships of the components to one another are not considered to be to scale.

DETAILED DESCRIPTION OF THE DRAWINGS

[0024] The battery cell 20 shown schematically in an exploded view in FIG. 1 is a prismatic battery cell 20. The battery cell 20 includes a battery cell housing, which is formed by a housing main body 9 and a cover 4. The battery cell housing forms a mechanically solid casing for the electrode units 10a, 10b arranged therein. Two electrode units 10a, 10b are arranged in the battery cell housing in the battery cell in the example shown. The electrode layers can be provided, for example, as a stack or coil (jellyroll) in the electrode units 10a, 10b. In the exemplary embodiment, the battery cell housing has a rectangular footprint and is essentially cuboid. The housing main body 9 and the cover 4 of the battery cell housing can be formed from a metal, for example aluminum. It is possible that the battery cell housing includes an electrically insulating coating at least in some areas.

[0025] The battery cell 20 includes a first terminal 1 and a second terminal 2, wherein the terminals 1, 2 are arranged on the cover 4 of the battery cell housing. The terminals 1, 2 are provided for electrically contacting the poles of the battery cell 20 and can each be electrically insulated from the cover 4 by an insulating plate 3. The terminals 1, 2 are each connected in the example shown by a rivet 6, which is led through the cover 4, to current collectors 8 of the electrode unit 10. Seals 5 are provided for sealing the feedthroughs through the cover 4. The electrode units 10a, 10b can be fixed in the battery cell housing by a holder 7, which is arranged between the electrode units 10 and the cover 4, and lateral holders 11.

[0026] An emergency venting opening 13 is arranged on the cover 4 of the battery cell housing. The emergency venting opening 13 is closed in the normal operation of the battery cell 20, for example by a bursting membrane. If the internal pressure in the battery cell 20 rises above a critical limit (typically between 6 bar and 15 bar), the bursting membrane opens so that the pressure can escape. The bursting membrane (not shown) can be fastened in the emergency venting opening 13 by laser welding, for example. The bursting membrane can have, for example, a thickness of 80 μm to 400 μm, preferably of 100 μm to 300 μm.

[0027] The electrode units 10a, 10b arranged in the battery cell each include a protective film 12. The protective film 12 advantageously essentially completely covers the electrode units 10a, 10b. “Essentially completely” can mean in particular that the film covers the electrode units except for possible openings for electrical feedthroughs and/or openings for the penetration of a liquid electrolyte.

[0028] A cross-sectional schematic view of the electrode units 10a, 10b is shown in FIG. 2. In the example shown, two electrode units 10a, 10b are arranged adjacent to one another. However, it is possible that the battery cell includes more than two electrode units, wherein the multiple electrode units can be interconnected in series or in parallel. The protective film 12 on the electrode units 10a, 10b is advantageously embodied in two layers. The protective film includes an inner layer 12a and an outer layer 12b. The outer layer 12b has the highest possible melting point, preferably of greater than 150° C. or even greater than 200° C. The outer layer 12b is provided in particular to ensure the thermal resistance of the protective film 12 in the event of a thermal runaway of an electrode unit 10a, 10b. The outer layer 12b preferably includes a polyethylene terephthalate, for example mylar, or a polyimide, for example Kapton®. The inner layer 12a can have a lower melting point than the outer layer 12b. If the melting point of the inner layer 12a is exceeded in the case of a thermal runaway of an electrode unit and the inner layer 12a is thus damaged, the outer layer 12b advantageously still remains intact for a longer time. The inner layer 12a is advantageously formed from a softer polymer than the outer layer 12b. The inner layer 12a can in particular improve the pressure distribution on the electrode units 10a, 10b. The inner layer 12a preferably includes polypropylene or polyethylene. The two-layer protective film 12 advantageously has a low thermal conductivity. The protective film reduces the heat transport between the adjacent electrode units 10a, 10b. In the event of a thermal runaway of an electrode unit, for example the electrode unit 10a, a thermal runaway of the adjacent electrode unit 10b is thus prevented or at least delayed. The heat resulting in the battery cell is thus released more slowly, so that the heat can be dissipated better, for example via the cover of the battery cell housing or a cooling. If a plurality of battery cells are arranged in a battery, damage to the entire battery is thus counteracted.

[0029] FIG. 3 shows a top view of an exemplary embodiment of the protective film 12 on a surface facing toward the bottom of the housing main body 9. The protective film 12 is advantageously perforated in this area. For example, the protective film 12 includes approximately 10 to 20 openings 14 in this area. The electrolyte can advantageously penetrate into the electrode units 10a, 10b through the openings 14 in the protective film 12 when the battery cell is filled with a liquid electrolyte.

[0030] FIG. 4 shows an example of the layer stack in an electrode unit 10a. The electrode unit 10a comprises copper foils 15, which are coated using an anode active material 16, and aluminum foils 19, which are coated using a cathode active material 18.

[0031] The anode active material 16 is, for example, a material from the group consisting of carbon-containing materials, silicon, silicon suboxide, silicon alloys, aluminum alloys, indium, indium alloys, tin, tin alloys, cobalt alloys, and mixtures thereof. The anode active material is preferably selected from the group consisting of synthetic graphite, natural graphite, graphene, meso-carbon, doped carbon, hard carbon, soft carbon, fullerene, silicon-carbon composite, silicon, surface-coated silicon, silicon suboxide, silicon alloys, lithium, aluminum alloys, indium, tin alloys, cobalt alloys, and mixtures thereof.

[0032] The cathode active material 18 can include a layered oxide such as a lithium-nickel-manganese-cobalt oxide (NMC), a lithium-nickel-cobalt-aluminum oxide (NCA), a lithium-cobalt oxide (LCO), or a lithium-nickel-cobalt oxide (LNCO). The layered oxide can in particular be an overlithiated layered oxide (OLO). Other suitable cathode active materials are compounds having spinel structure, such as lithium-manganese oxide (LMO) or lithium-manganese-nickel oxide (LMNO), or compounds having olivine structure, such as lithium-iron phosphate (LFP) or lithium-manganese-iron phosphate (LMFP).

[0033] The anode active material 16 is separated from the cathode active material 18 in each case by a separator 17. The separator 17 is in particular a film and includes a material which is permeable to lithium ions but impermeable to electrons. Polymers can be used as separators, in particular, a polymer selected from the group consisting of polyesters, in particular polyethylene terephthalate, polyolefins, in particular polyethylene and/or polypropylene, polyacrylonitriles, polyvinylidene fluoride, polyvinylidene hexafluoropropylene, polyether imide, polyimide, aramid, polyether, polyether ketone, synthetic spider silk, or mixtures thereof. The separator can optionally additionally be coated using ceramic material and a binder, for example based on Al.sub.2O.sub.3

[0034] A layer sequence S, which includes a copper foil 15 coated on both sides using the anode active material 16, an aluminum foil 19 coated on both sides using the cathode active material 18, and separators 17, can repeat multiple times in the electrode unit 10a (indicated in the drawing as N*S). A copper foil 15 coated using the anode active material 16 forms the terminus of the electrode unit 10a on both sides.

[0035] Although the invention was illustrated and described in detail on the basis of exemplary embodiments, the invention is not thus restricted by the exemplary embodiments. Rather, other variations of the invention can be derived therefrom by a person skilled in the art without leaving the scope of protection of the invention defined by the claims.

LIST OF REFERENCE SIGNS

[0036] 1 first terminal [0037] 2 second terminal [0038] 3 insulating plate [0039] 4 cover [0040] 5 seal [0041] 6 rivet [0042] 7 holder [0043] 8 current collector [0044] 9 housing main body [0045] 10 electrode unit [0046] 11 lateral holder [0047] 12 protective film [0048] 12a inner layer [0049] 12b outer layer [0050] 13 emergency venting opening [0051] 14 opening [0052] 15 copper foil [0053] 16 anode active material [0054] 17 separator [0055] 18 cathode active material [0056] 19 aluminum foil [0057] 20 battery cell