Multi-layer protective element for battery assembly comprising at least two battery cells

Abstract

The invention relates to a multi-layer protective element (1) for a battery assembly (100) comprising at least two battery cells (10) wherein the protective element (1) can be arranged between the battery cells (10) and wherein the protective element (1) comprises at least two heat resistant layers, and wherein the first layer is formed as an elastic buffer layer (2) and comprises a non-woven polymeric material and / or a non-woven ceramic material, and the second layer is formed as a rigid thermal barrier layer (3) and comprises a ceramic material. The invention also relates to a battery assembly (100) comprising such a multilayer protective element (1), and to the use of a multilayer protective element (1) in a battery assembly (100).

Description

[0001] The present invention relates to a multi-layer protective element for a battery assembly comprising at least two battery cells. The present invention also relates to a battery assembly comprising such a multi-layer protective element and to the use of the multi-layer protective element in a battery assembly.

[0002] Today, high-voltage batteries are used in numerous applications, especially in applications related to electric vehicles. For this purpose, individual battery cells are assembled to form larger battery arrays. The individual battery cells are typically in the form of prismatic or pouch-shaped battery cells having two flat outer surfaces facing each other in parallel, and the individual battery cells are arranged closely together in a housing and connected in series and / or in parallel. Depending on the number of battery cells used, a battery assembly with an energy capacity of 5 to 200 kWh and an open-circuit voltage of 60 to 800 can be provided in this way.

[0003] During operation, the battery cells undergo various reversible and irreversible processes, and various measures have been taken in the prior art to address these processes.

[0004] Thus, the battery cells expand to a certain extent during each charging process and contract again during the subsequent discharging process. This process is also referred to as the "breathing" of the battery cells. To compensate for the associated dimensional changes, balancing elements are used today, which are arranged between the individual battery cells. Such a balancing system is known, for example, from US10,840,494B2. In addition, over time, the breathing effect accumulates, resulting in a permanent expansion of the battery cells.

[0005] In addition to the breathing that all battery cells undergo, thermal runaway can also occur in individual battery cells during operation under extreme conditions. This is an uncontrolled reaction within the battery cell, which may be accompanied by the generation of extreme heat and pressure. The heat can be rapidly transferred to adjacent battery cells and a chain reaction can start, resulting in an explosive release of energy and causing the battery assembly to catch fire. For this reason, for example, from EP 3 661 744 B1 and WO 2008 / 136875A1, barriers made of fireproof materials are provided between the individual battery cells to prevent the spread of thermal runaway to adjacent battery cells. However, such barriers made of fireproof materials are not sufficient to be able to respond to the dimensional changes of the above-mentioned battery cells. US2022 / 166086 discloses a battery block comprising a plurality of battery cells stacked along the thickness of each of the plurality of battery cells and separators inserted between the plurality of battery cells. US20220181715A1 discloses a heat-insulating multi-layer sheet comprising a compressible layer and a heat-insulating layer.

[0006] The object of the present invention is to provide an improved multi-layer protective element for a battery assembly, which can both compensate for the dimensional changes of individual battery cells during charging and discharging cycles and at the same time provide very good protection against heat propagation during thermal runaway of the battery cells. Another object of the present invention is to provide a battery assembly having such a protective element.

[0007] These objects are achieved by a protective element having the features of claim 1, by a battery assembly having a protective element according to claim 14 and by the use of a protective element according to claim 15.

[0008] Advantageous embodiments and further developments of the present invention are the subject of the dependent claims.

[0009] According to claim 1, the present invention is a multi-layer protective element for a battery assembly comprising at least two battery cells, wherein the protective element can be arranged between the battery cells. The invention is characterized in that the protective element comprises at least two heat-resistant layers, wherein the first layer is formed as an elastic buffer layer and comprises a non-woven polymer material and / or a non-woven ceramic material, and the second layer is formed as a rigid heat-insulating barrier layer and comprises a ceramic material. The elastic buffer layer preferably comprises non-woven polymer fibers as the non-woven polymer material and / or non-woven ceramic fibers as the non-woven ceramic material. In this context, the adjective "heat-resistant" should be understood to mean that when exposed to a temperature of up to 600 °C for two minutes, the corresponding layer does not melt and / or oxidize. According to this understanding, according to the present invention, both the elastic buffer layer and the rigid heat-insulating barrier layer are heat-resistant. Preferably, it means that when exposed to a temperature of 600 °C for two minutes, the corresponding layer does not melt and / or oxidize. In this context, the adjective "rigid" should be understood to mean that the barrier layer is more rigid than the elastic buffer layer, such that during dimensional changes of the battery cells, the barrier layer is not compressed, or is compressed to a lesser extent compared to the elastic buffer layer.

[0010] In other words, due to its layered structure and the special materials used, the protective element according to the present invention combines elasticity, heat insulation and flame retardancy properties in one component and is thus designed as a multi-functional protective element. When the battery cells expand, the elastic buffer layer comprising a non-woven polymer material and / or a non-woven ceramic material, preferably non-woven polymer fibers and / or non-woven ceramic fibers, can be compressed, and when the battery cells contract, it can be restored. The restoring force that appears in the elastic material due to such compression causes the layer to move back to its original state when the battery cells contract. In this way, the dimensional changes of the battery cells, especially the dimensional changes at the center of their flat outer surface, can be dynamically compensated.

[0011] The thermal insulation barrier layer comprises a ceramic material with low thermal conductivity and good flame retardant properties. In this way, heat transfer from one battery cell to an adjacent battery cell can be substantially prevented or delayed.

[0012] The compressible properties of the protective element can also have been utilized during the assembly of a battery assembly comprising a plurality of individual battery cells. For example, when assembling the battery assembly, the battery cells are stacked and installed in a housing; arranging the compressible protective element according to the present invention between at least some of the battery cells allows the battery cell stack to be slightly compressed and thus optimally installed in the housing.

[0013] In the simplest embodiment, the protective element comprises a buffer layer and a barrier layer. However, in principle, the protective element can also comprise a plurality of buffer layers and / or a plurality of barrier layers and / or other layers with different designs.

[0014] According to one embodiment of the present invention, the polymeric material of the buffer layer is selected from non-woven fibers made of partially and fully oxidized polyacrylonitrile, silicates, silica, metal oxides, metal nitrides, metal carbides, metal carbonates, mica, rock powder, glass fiber, and combinations of materials comprising one or more of these materials. These materials have good elastic properties in the non-woven state, that is, these materials can be compressed under the action of force and return to their initial state when the force is released.

[0015] According to another embodiment of the present invention, the ceramic material of the buffer layer is selected from the following materials: non-woven fibers made of silicates, silica, metal oxides, metal nitrides, metal carbides, metal carbonates, mica, rock powder, glass fiber, and combinations of materials comprising one or more of these materials. It can be designed as a pad or composite material of ceramic material.

[0016] Preferably, based on the standard specification ASTM D1056, at a temperature of about 100 °C, when the buffer layer is compressed by 25%, the compression force of the buffer layer is about 5 to 300 kPa, more preferably 5 to 200 kPa, and the compression set is preferably less than 10%, more preferably less than 5%. According to the present invention, in particular, the buffer layer is heat-resistant, which should be understood in this context to mean that the buffer layer does not melt and / or oxidize when exposed to a temperature of up to 600 °C for two minutes. Preferably, the buffer layer does not melt and / or oxidize when continuously exposed to a temperature of 600 °C for two minutes. In a preferred embodiment, the buffer layer has thermal insulation properties, and the thermal conductivity in the direction perpendicular to the surface area facing the battery cell is preferably less than 0.5 W / mK, particularly preferably less than 0.3 W / mK.

[0017] According to another embodiment of the present invention, the ceramic material of the barrier layer is selected from the following materials: silicate, silicon dioxide, metal oxide, metal nitride, metal carbide, metal carbonate, mica, rock powder, glass fiber, and a combination of materials containing one or more of these materials. It can be designed as a pad or composite material of ceramic material. Preferably, the ceramic material of the barrier layer is not a non-woven material, especially not non-woven fibers.

[0018] The barrier layer preferably has a flame retardancy of V1 level measured by UL 94 Test for Flammability of Plastics, and particularly preferably has a flame retardancy of V0 level measured by UL 94 Test for Flammability of Plastics. The barrier layer preferably has heat insulation performance and the thermal conductivity in the direction perpendicular to the surface area facing the battery cell is preferably less than 0.5 W / mK, particularly preferably less than 0.3 W / mK.

[0019] According to a proposal of the present invention, the thickness of the buffer layer is 0.1 to 10 mm. Preferably, the thickness of the buffer layer can be 3 to 5 mm.

[0020] According to another proposal of the present invention, the thickness of the barrier layer is 0.1 to 10 mm. Preferably, the thickness of the barrier layer can be 0.1 to 3 mm.

[0021] The total thickness of the protective element is preferably 0.2 to 20 mm, more preferably 0.4 to 8 mm. The area of the protective element is preferably 30% to 100% of the flat outer surface area of the battery cell, more preferably 60% to 95%.

[0022] According to the present invention, the barrier layer is rigid, which means that the barrier layer is harder than the buffer layer. Therefore, during the size change of the battery cell, the barrier layer will not be compressed or the degree of compression is less than that of the buffer layer. In a preferred embodiment, under the same deformation, the compression force of the barrier layer can be at least 150% of the compression force of the buffer layer. For example, if the buffer layer exhibits a compression force of 0.1 MPa under a 0.1 mm deformation, the barrier layer should have a value of at least 0.15 MPa under the same deformation. If this value of the barrier layer is too small, the barrier layer may be permanently deformed, which may cause it to lose its initial purpose of preventing heat transfer.

[0023] In addition, the barrier layer is preferably designed not to melt even when exposed to a high temperature of at least 600 °C for two minutes, and particularly preferably not to melt when exposed to a high temperature of at least 1000 °C for two minutes. In this way, when a thermal runaway occurs in the battery cell, the barrier layer can act as a barrier layer for other battery cells.

[0024] The value of the dielectric strength of the barrier layer and / or the buffer layer can be greater than 2.5 kV / mm. Preferably, the value can be higher than 3.5 kV / mm.

[0025] The buffer layer and the barrier layer can be assembled into the protective element of the present invention by various processes such as lamination, dispensing, spraying, curtain coating, slot coating, and roll-to-roll.

[0026] According to the present invention, an adhesive material layer can be arranged between the buffer layer and the barrier layer. The adhesive material can include, for example, a pressure-sensitive adhesive or a hot-melt adhesive.

[0027] In principle, the outer surface of the protective element can be formed by the buffer layer and / or the barrier layer. According to an alternative embodiment of the present invention, at least one outer surface of the protective element includes a film based on polyethylene terephthalate, polyethylene, polypropylene, polyolefin, nylon, polyamideimide, polyamide, or polyimide. It can be provided that the film is bonded to the buffer layer and / or the barrier layer by an adhesive material.

[0028] In other embodiments of the present invention, the barrier layer can contain hollow particles, for example, in the form of hollow silica and / or aerogel, to improve the heat insulation performance.

[0029] In other embodiments of the present invention, in order to enhance the heat insulation performance, a refractory heat-insulating material can be embedded in the buffer layer and / or the barrier layer. The refractory heat-insulating material can be selected from one of micron silica, silica aerogel, glass bubbles, and some micron- and / or nano-sized particles having spaces for trapping air.

[0030] According to claim 10, the present invention also relates to a battery assembly having at least two battery cells, and a multilayer protective element according to any one of claims 1 to 9 is arranged between the two battery cells. In the case of a battery assembly having a plurality of battery cells, in principle, the protective element according to the present invention can be arranged between every two adjacent battery cells. Alternatively, such protective elements can be arranged only between some of the battery cells.

[0031] Furthermore, according to claim 11, there is provided the use of the multilayer protective element according to any one of claims 1 to 9 for insertion between two battery cells of a battery assembly.

[0032] The present invention will be explained in more detail below by way of example embodiments and with reference to the accompanying drawings, wherein:

[0033] Figure 1 : shows a schematic cross-sectional view of an embodiment of the protective element according to the present invention;

[0034] Figure 2: Schematically shows an alternative embodiment of a protective element according to the present invention;

[0035] Figure 3 : Shows a battery assembly having a protective element according to the present invention.

[0036] Figure 1 Shows a multi-layer protective element according to the present invention, which is generally labeled 1. The protective element 1 includes a central elastic buffer layer 2 made of a non-woven felt of partially oxidized polyacrylonitrile fibers. Rigid heat-insulating barrier layers 3 containing a ceramic material (mica in this example) are provided on each side of the buffer layer 2. The buffer layer 2 is bonded to each of these two barrier layers 3 by a thin layer 4 of an adhesive material. In this example, the adhesive material is a pressure-sensitive adhesive.

[0037] The outer surface of the protective element 1 is formed by a film 5 based on polyethylene terephthalate, and the film 5 is used to protect the underlying barrier layer 2. Additionally, the film 5 and the underlying barrier layer 2 are bonded together by an adhesive material layer not shown in the figure.

[0038] The thickness of the buffer layer 2 is 4 mm, the thickness of the barrier layer 3 is 1 mm, and the thickness of the entire protective element 1 including the adhesive layer 4 is approximately 8 mm.

[0039] Therefore, the protective element 1 combines the buffer layer 2 (which is elastic and thus reversibly compressible) and two rigid barrier layers 3 (which have flame-retardant and heat-insulating properties due to their materials) in one assembly. This makes the protective element 1 extremely suitable for insertion between the battery cells 10 in the battery assembly 100, as Figure 3 shown.

[0040] Figure 3 Shows a battery assembly generally labeled 100, in which stacks 6 of prismatic battery cells 10 are arranged adjacent to each other. Each stack 6 includes a plurality (e.g., eight) of battery cells 10, however, Figure 3 only 3 of them are shown in Figure 3 schematically. As

[0041] Figure 2Another embodiment of a multi-layer protective element, generally labeled 1, is shown. The protective element 1 has a central barrier layer 3 comprising a ceramic material (in this case fiberglass). To better insulate heat, the barrier layer 3 also includes aerogel particles. Buffer layers 2 made of non-woven felts of partially oxidized polyacrylonitrile fibers are disposed on each side of the central barrier layer 3. The barrier layer 3 and the buffer layers 2 are bonded together by an adhesive layer 4.

[0042] These two buffer layers 2 respectively form the outer surfaces of the protective element 1. Different from Figure 1 the example of the embodiment of, no additional film is provided on the outer surface here.

[0043] The total thickness of the protective element 1 is about 8 mm, wherein the thickness of each of the buffer layers 2 is about 2.5 mm and the thickness of the barrier layer 3 is about 3 mm.

[0044] List of reference symbols

[0045] 1 Protective element

[0046] 2 Buffer layer

[0047] 3 Barrier layer

[0048] 4 Layer

[0049] 5 Film

[0050] 6 Stack

[0051] 10 Battery cell

[0052] 100 Battery assembly

Claims

1. A multi-layer protective element (1) for a battery assembly (100) comprising at least two battery cells (10), wherein the protective element (1) can be arranged between the battery cells (10), characterized in that, The protective element (1) comprises at least two heat-resistant layers, wherein the first layer is formed as an elastic buffer layer (2) and comprises a non-woven polymer material and / or a non-woven ceramic material, and the second layer is formed as a rigid heat-insulating barrier layer (3) and comprises a ceramic material.

2. The multi-layer protective element (1) according to claim 1, characterized in that, The polymer material is selected from non-woven fibers made of partially and fully oxidized polyacrylonitrile, silicates, silica, metal oxides, metal nitrides, metal carbides, metal carbonates, mica, rock powder, glass fibers, and combinations of materials comprising one or more of these materials.

3. The multi-layer protective element (1) according to claim 1 or 2, characterized in that, The ceramic material of the buffer layer and / or the barrier layer is selected from the following materials: silicates, silica, metal oxides, metal nitrides, metal carbides, metal carbonates, mica, rock powder, glass fibers, and combinations of materials comprising one or more of these materials.

4. The multi-layer protective element (1) according to any one of claims 1 to 3, characterized in that, The thickness of the buffer layer (2) is 0.1 to 10 mm.

5. The multi-layer protective element (1) according to any one of claims 1 to 4, characterized in that, The thickness of the barrier layer (3) is 0.1 to 10 mm.

6. The multi-layer protective element (1) according to any one of claims 1 to 5, characterized in that, The total thickness of the protective element (1) is preferably 0.2 to 20 mm.

7. The multi-layer protective element (1) according to any one of claims 1 to 6, characterized in that A bonding material layer (4) is arranged between the buffer layer (2) and the barrier layer (3).

8. The multi-layer protective element (1) according to any one of claims 1 to 7, characterized in that, At least one outer surface of the protective element (1) comprises a film (5) based on polyethylene terephthalate, polyethylene, polypropylene, polyolefin, nylon, polyamideimide, polyamide or polyimide.

9. The multi-layer protective element (1) according to claim 8, characterized in that, The film (5) is bonded to the buffer layer (2) and / or the barrier layer (3) by a bonding material.

10. The multi-layer protective element (1) according to any one of claims 1 to 9, characterized in that, The barrier layer (3) comprises hollow silica and / or aerogel.

11. The multi-layer protective element (1) according to any one of claims 1 to 10, characterized in that, Based on the standard specification ASTM D1056, at a temperature of about 100 °C, when the buffer layer (2) is compressed by 25%, the compression force of the buffer layer is about 5 to 300 kPa, and the compression deformation is preferably less than 10%.

12. The multi-layer protective element (1) according to any one of claims 1 to 11, characterized in that, The thermal conductivity of the buffer layer (2) and / or the barrier layer (3) in a direction perpendicular to the surface area facing the battery cell (10) is less than 0.5 W / mK.

13. The multi-layer protective element (1) according to any one of claims 1 to 12, characterized in that, A refractory heat-insulating material can be embedded in the buffer layer (2) and / or the barrier layer (3).

14. A battery assembly (100) comprising at least two battery cells (10), between which a multi-layer protective element (1) according to any one of claims 1 to 13 is arranged.

15. Use of the multi-layer protective element (1) according to any one of claims 1 to 13 for insertion between two of the battery cells (10) of the battery assembly (100).

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