PROPAGATION BARRIER FOR BATTERIES

Abstract

The present invention relates to a barrier for preventing the propagation of a thermal event within a multi-cell battery module, comprising a framework structure and a heat-absorbing material, which comprises water and a component based on biogenic raw materials. Furthermore, the invention relates to a multi-cell battery module and a battery comprising at least one such barrier. Finally, the present invention also relates to a method for preventing the propagation of a thermal event within a multi-cell battery module.

Claims

1. A barrier for preventing propagation of a thermal event within a multi-cell battery module comprising a thermally and electrically insulating frame structure which has a plurality of cavities which are at least partially filled with a heat-absorbing material, wherein the heat-absorbing material comprises water and a component based on biogenic raw materials.

2. The barrier of claim 1, wherein the heat absorbing material comprises 70-99.8% by weight water, and 0.2-30% by weight of a component based on biogenic raw materials.

3. The barrier of claim 1, wherein the heat-absorbing material comprises a hydrogel which is a network of at least one biogenic gelling agent and water, wherein the gelling agent is preferably a polysaccharide and/or gelatin the polysaccharide is preferably selected from the group consisting of agar-agar, starch, in particular corn starch, starch derivatives, hydroxypropylmethylcellulose, methylcellulose, κ-carrageenan, .Math.-carrageenan, pectin, gellan, scleroglucan, alginates and combinations thereof.

4. The barrier of claim 1, wherein the heat-absorbing material further comprises 0.05-10% by weight of at least one additive, wherein the at least one additive is preferably selected from the group consisting of rheology modifiers, biocides, salts, flame retardants, dyes and combinations thereof, the rheology modifiers are preferably selected from the group consisting of xanthan, cellulose, carboxymethyl cellulose, gum arabic, guar gum, maltodextrin and combinations thereof, and the salts are preferably hydrate salts, particularly preferably hydrate salts selected from the group consisting of Na.sub.2CO.sub.3.Math.10H.sub.2O, Na.sub.2SO.sub.4.Math.10H.sub.2O, Na.sub.3PO.sub.4.Math.12H.sub.2O and MgSO.sub.4.Math.7H.sub.2O.

5. The barrier of claim 1, wherein the heat-absorbing material comprises water-swollen cork particles from tree bark.

6. The barrier of claim 1, wherein the cavities of the frame structure, based on the volume of the cavities, are preferably filled with the heat-absorbing material to at least 65% by volume, preferably to at least 70% by volume, particularly preferably to at least 90% by volume, in particular to at least 98% by volume.

7. The barrier of claim 1, wherein the frame structure contains 60-100% by weight of a polymeric matrix material and 0-40% by weight of fillers, preferably 70-99% by weight of a polymeric matrix material and 1-30% by weight fillers, wherein the polymeric matrix material is preferably selected from the group consisting of polyetheretherketone (PEEK), polyaramid, silicone and combinations thereof, and wherein the fillers are preferably selected from the group consisting of clay, expanded clay, mica, glass, expanded glass, stone, cork particles and combinations thereof.

8. The barrier of claim 1, wherein the frame structure has a coating.

9. The barrier of claim 1, wherein the cavities of the frame structure are sealed to prevent drying out of the heat-absorbing material prior to the occurrence of a thermal event, preferably with a polymer foil, a metal foil or a laminate of the aforementioned foils, wherein the polymer foil is preferably selected from the group consisting of polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), polyphenylene sulfide (PPS), ethylene-tetrafluoroethylene copolymer (ETFE) and combinations thereof and wherein the metal foil is preferably an aluminum foil.

10. The barrier of claim 1, wherein the frame structure is formed as a layer having honeycomb, round or square cross-section cavities, or as a foam, or a combination thereof.

11. The barrier of claim 1, wherein the barrier is formed as a layer with a layer thickness of 0.5 to 20 mm, preferably 0.5 to 5 mm, particularly preferably 0.5 to 2 mm.

12. A multi-cell battery module or battery comprising at least one barrier of claim 1 or a cork layer soaked in water.

13. The battery module of claim 12, wherein the barrier or the cork layer soaked in water is arranged in a space between two cells and/or in a space between an outer cell and a wall of the battery module.

14. A method for preventing the propagation of a thermal event within a multi-cell battery module, in which a barrier of claim 1 or a cork layer soaked in water is arranged between the battery cells.

Description

DESCRIPTION OF PREFERRED EMBODIMENTS

[0038] Preferred embodiments of the invention are explained in more detail with reference to the following examples, experiments and figures, without wishing to limit the invention thereto.

[0039] FIG. 1 shows a schematic of a framework structure 1, which is designed as a layer with honeycomb cross-section cavities 2.

[0040] FIG. 2 shows a photograph of a barrier according to the invention without a sealing foil. The framework structure of the barrier is also designed here as a layer with honeycomb cross-section cavities.

[0041] FIG. 3 shows a photograph of two barriers according to the invention, in which the cavities of the framework structure are sealed with a pouch foil. The left barrier is unused, while the right barrier has already served to shield a thermal battery cell.

[0042] FIG. 4 shows the arrangement of a barrier 3 according to the invention in a battery (test) module comprising two battery cells 4a and 4b. 5a and 5b is a thermal insulation which, after the proactive triggering of the thermal event, prevents part of the released thermal energy from being absorbed by the clamping plates 6a and 6b, which have a certain thermal capacity. This avoids measurement errors. The clamping plates ensure the mechanical cohesion of the module. T1 and T2 show the measuring points where the temperature was measured. T1 is the temperature measurement point of the cell where the thermal event is triggered, and T2 is the temperature measurement point on the neighboring cell.

[0043] FIG. 5 shows the results of a thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) for samples of two different heat-absorbing reference materials, material 1 (see upper diagram) and material 2 (see lower diagram). Heating was at a rate of 10 K/min. Material 1 is a comparative material in which a salt hydrate (calcium sulfate dihydrate, CaSO.sub.4.Math.2H.sub.2O) was introduced into a silicone matrix. Material 2 is a hydrogel obtained using conventional polyacrylic acid superabsorbent. The differential heat flow “DSC” is stated in mW/mg and is shown so that endothermic events in the sample pan are recorded as an upward excursion. Percent mass loss is plotted on the right y-axis. The specific vaporization enthalpy of material 1 based on this measurement was 351 J/g. The specific vaporization enthalpy of material 2 was 1185 J/g.

[0044] FIG. 6 shows the results of another combined TGA/DSC measurement with a heating rate of 10 K/min. A sample of a heat-absorbing material according to the invention consisting of 10% by weight gelling powder and 90% by weight water was measured, the gelling powder used consisting of about 30% by weight agar-agar and about 70% by weight maltodextrin. The differential heat flow “DSC” is stated in mW/mg and is shown so that endothermic events in the sample pan are recorded as an upward excursion. Percent mass loss is plotted on the right y-axis. The specific vaporization enthalpy of the material in the DSC measurement is determined to be 1880 J/g and is therefore higher than the specific vaporization enthalpies of materials 1 and 2 in FIG. 5.

[0045] FIG. 7 shows the results of another combined TGA/DSC measurement, at which a heating rate of 10 K/min was used. The sample here consists of cork soaked in water, namely 37.5% by weight cork and 62.5% by weight water. The differential heat flow “DSC” is stated in mW/mg and is shown so that endothermic events in the sample pan are recorded as an upward excursion. Percent mass loss is plotted on the right y-axis. The specific enthalpy of vaporization is determined to be 1224 J/g. This enthalpy is also higher than the specific vaporization enthalpies of materials 1 and 2 in FIG. 5.

[0046] FIG. 8 shows the temperature profiles of a battery (test) module with a structure analogous to FIG. 4.

[0047] The temperature profile in the upper diagram corresponds to the temperature profile that was measured for a module without a barrier. The thermal runaway of a battery cell (cell 1, also referred to as the TR cell) is triggered by the nail penetration. The temperature rises sharply after the nail penetration and the voltage drop of cell 1 (U cell 1). The temperature of the neighboring cell (temperature of neighboring cell, cell 2) also rises sharply with a short delay due to the thermal short circuit of both cells (test without barrier). After 38 seconds, the voltage drop in cell 2 can be seen (U cell 2) and the temperature of the neighboring cell, which is thermally runaway, continues to rise. Thermal propagation has taken place.

[0048] The temperature profile in the lower diagram is the temperature profile that was measured in a battery (test) module with a barrier according to the invention arranged between the battery cells. As can be clearly seen, the barrier according to the invention can thermally shield the second battery cell to the extent that the critical temperature is not reached.