Propagation barrier with reinforcing filling material and method of producing same

Abstract

The present invention relates to a barrier for preventing the propagation of a thermal event within a multi-cell battery module (so-called propagation barrier), comprising a heat-absorbing protective layer based on a hydrogel and a reinforcing filling material. Furthermore, the invention relates to a battery module which comprises the barrier, and to the use of the barrier to compensate for volume fluctuations within a battery module. In addition, a method for producing the propagation barrier is also specified.

Claims

1-15. (canceled)

16. A barrier for preventing propagation of a thermal event within a multi-cell battery module, comprising a heat-absorbing protective layer containing 70.0-97.5% by weight hydrogel and 2.5-30.0% by weight reinforcing filling material, wherein the hydrogel comprises a matrix material and water and the reinforcing filling material is dispersed in the hydrogel.

17. The barrier according to claim 16, wherein the protective layer is enclosed in a foil impermeable to water vapor.

18. The barrier according to claim 17, wherein the foil impermeable to water vapor comprises a polymer foil, a metal foil, or a laminate thereof.

19. The barrier according to claim 17, wherein the foil impermeable to water vapor is selected from the group consisting of polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), polyphenylene sulfide (PPS), ethylenetetrafluoroethylene copolymer (ETFE), polyurethanes (PU), polyamides (PA), polyesters, and combinations thereof.

20. The barrier according to claim 16, wherein the matrix material comprises at least 85% natural polymer, wherein said natural polymer is selected from the group consisting of alginate, agar-agar, starch, starch derivatives, -carrageenan, .Math.-carrageenan, pectin, gellan, scleroglucan, and combinations thereof.

21. The barrier according to claim 16, wherein the matrix material comprises at least 85% by weight calcium alginate.

22. The barrier according to claim 16, wherein the matrix material further comprises up to 15% by weight thickener.

23. The barrier according to claim 22, wherein the thickener is selected from the group consisting of hydroxyethyl cellulose; hydroxypropyl cellulose; hydroxypropylmethylcellulose and/or carbox-ycellulose, guar gum, xanthan gum, or mixtures thereof.

24. The barrier according to claim 16, wherein the reinforcing filling material is selected from the group consisting of hydroxyapatite, calcium carbonate, calcium sulfate; aluminum oxide, magnesium oxide, hydrates of the aforementioned substances, and mixtures thereof.

25. The barrier according to claim 16, wherein the hydrogel comprises 5-30% by weight matrix material and 70-95% by weight water.

26. The barrier according to claim 16, wherein the protective layer has a thickness of 0.25-10.0 mm.

27. The barrier according to claim 16, wherein the protective layer has a thickness of 1.5-3.0 mm.

28. The barrier according to claim 16, wherein the heat-absorbing protective layer has passage openings, wherein the volume proportion of the passage openings in the protective layer is between 20% and 60%.

29. The barrier according to claim 16, wherein the heat-absorbing protective layer has passage openings, wherein each passage opening has a cross-sectional area of 0.5 mm.sup.2-8.0 mm.sup.2.

30. The barrier according to claim 16, wherein the heat-absorbing protective layer has passage openings, wherein each passage opening has a cross-sectional area of 2.0 mm.sup.2-5.0 mm.sup.2.

31. A method for preventing the propagation of a thermal event within a multi-cell battery module comprising: a) providing a multi-cell battery module comprising a barrier of claim 1, wherein the barrier is arranged between a first battery cell and an adjacent second battery cell; b) generating heat in the first battery cell; c) absorbing the generated heat into the barrier thereby thermally shielding the adjacent second battery from the generated heat.

32. The method of claim 31, wherein the heat-absorbing protective layer has passage openings, wherein the volume proportion of the passage openings in the protective layer is between 1% and 90%, and the method comprises displacing a portion of the hydrogel and the reinforcing filling material into the passage openings when force is applied, thereby compensating for volume fluctuations.

33. A battery module, comprising a plurality of battery cells and at least one barrier according to claim 16, wherein the barrier is arranged between two adjacent battery cells.

34. The battery module according to claim 33, wherein the battery cells are lithium-ion cells.

35. A method of manufacturing a barrier according to claim 16, in which a heat-absorbing protective layer is produced, wherein the heat absorbing protective layer is produced by i) mixing sodium alginate powder, a reinforcing filling material and water to form a viscous mass, ii) pouring the mass onto a flat surface or into a mold with a planar bottom, and iii) wetting the cast mass with a solution containing calcium ions or immersing it in a solution containing calcium ions.

Description

DESCRIPTION OF PREFERRED EMBODIMENTS

[0052] Preferred embodiments of the invention are explained in more detail with reference to the figures and the following example, without wishing to limit the invention thereto. In particular, the following example describes only one production route for the barriers according to the invention. It can be assumed that the barriers can also be manufactured industrially by extrusion.

[0053] FIG. 1 shows the arrangement of a barrier 3 according to the invention in a battery (-test) module comprising two battery cells 1 and 2. 5a and 5b are thermal insulations, which prevent, after the proactive triggering of the thermal event, that a part the thermal energy released is absorbed by the clamping plates 6a and 6b, which have a certain heat capacity. This avoids measurement errors. The clamping plates ensure the mechanical cohesion of the module. The measuring points at which the temperature is measured are on the front and back of each cell.

[0054] FIG. 2 shows the temperature profile of cells 1 and 2 after nail penetration of cell 1. From the temperature profile it can be deduced that barrier 3 according to the invention successfully shields cell 2 thermally. This prevents cell 2 from reaching the critical temperature.

EXAMPLE

1) Production of the Barrier According to the Invention

[0055] 80% by weight water, 15% by weight sodium alginate and 5% by weight filling material (calcium carbonate) are mixed for about 3 minutes. The resulting mixture is applied in a flat and open mold with a thickness of about 2.3 mm. The mixture of thickness 2.3 mm is immersed with the mold in an aqueous CaCl.sub.2 solution (5% by weight) for 30 seconds. This creates a heat-absorbing protective layer comprising a flexible, homogeneous hydrogel with a thickness of 2.6 mm. Compared to the dimensions of the mold in which the mixture was applied, the heat absorbing protective layer has shrinkage of about 5% in both length and width. The protective layer contains about 80% by weight water.

[0056] Finally, the protective layer is welded into a foil impermeable to water vapor (foil thickness 0.15 mm).

2) Nail Penetration Test

[0057] The barrier produced was placed in a gap between two fully charged 40 Ah NMC 111 prismatic cells. The arrangement corresponds to the illustration in FIG. 1. The thermal runaway of the cell 1 was then provoked by penetrating it with a nail. The temperature development at the front and back of both cells was measured and recorded for a period of 7000 seconds (see FIG. 2). The barrier prevented thermal runaway from cell 1 to cell 2.