Battery module for a motor vehicle battery and battery for a motor vehicle

Abstract

Battery module (1) for a battery (2) of a motor vehicle, comprising at least two spaced-apart battery cells (3) and at least one associated cell barrier (4), which is arranged at least partially between the battery cells (3), wherein the respective cell barrier (4) is formed at least partially from a first material (5) which changes its thermal conductivity discontinuously when a certain temperature value is exceeded or fallen below, characterized in that - the cell barrier (4) is formed from at least two layers (6, 7) which are arranged next to each other, wherein a first of the layers (6, 7) is at least partially formed from the first material (5), - wherein another of the layers (6, 7) is at least partially formed from a second material (8) which has a higher mechanical stability compared to the first material (5), and - wherein another of the layers (6, 7) is at least partially formed from a third material (9) which is a thermal insulator and is designed in such a way that it encloses in its entirety an assembly of several battery cells (3) separated by the other layers of the cell barrier.

Description

[0001] The invention relates to a battery module for a motor vehicle battery according to the preamble of claim 1. Furthermore, the invention relates to a battery for a motor vehicle according to the preamble of claim 5.

[0002] In electromobility, batteries, especially high-voltage storage systems also known as traction batteries, play an increasingly important role in powering motor vehicles, particularly hybrid and electric vehicles. Currently, lithium-ion batteries are predominantly used in electrically powered vehicles. These typically consist of individual battery cells grouped together to form battery modules. These battery modules are then connected together to form the complete battery. To maximize the vehicle's range, the batteries must achieve the highest possible capacity and / or voltage, which explains the need to connect individual battery cells or modules.

[0003] For example, if an internal short circuit occurs in one of the battery cells, particularly in lithium-ion batteries, a so-called thermal event can occur. This event initially takes place within the battery cell, where the cell can smolder or burn out, resulting in a self-reinforcing, heat-generating process. Due to the ever-increasing energy density of batteries and high-voltage storage systems, driven by factors such as increasing cell packing densities, especially within battery modules, the risk grows that neighboring cells of the cell experiencing the thermal event will also suffer a short circuit or thermal event due to the high heat generated by the faulty cell, thus causing them to fail.This can cause a chain reaction, a so-called domino effect, which can lead to the destruction of the entire battery.

[0004] Currently, high-voltage storage systems are cooled by active liquid recirculation cooling. For example, DE 10 2013 226 813 A1 discloses a cooling device for a high-voltage storage system comprising a cooling element through which a refrigerant can flow, wherein the cooling element is designed to absorb heat from the high-voltage storage system and transfer it to the refrigerant flowing through it.

[0005] US patent 2017 / 0149103A1 discloses a composite material with phase change material arranged within the battery module, which is intended as a large-area element for temperature-dependent heat dissipation.

[0006] US patent 2017 0179 554 A1 discloses a laminate of thermally conductive layers and intumescent layers arranged in the battery module, which expands when the temperature rises and thereby changes its thermal conductivity.

[0007] Furthermore, other battery designs worthy of mention are disclosed in US 2012 / 0 028 107 A1, US 2010 / 0 028 758 A1 and FR 2 992 907 A1.

[0008] Furthermore, WO 2016 / 166 659 A1 discloses a battery module for a traction battery, wherein the battery module consists of a plurality of battery cells and a plurality of heat transfer elements. A cooling plate serves for heat transfer from the heat transfer elements.

[0009] Finally, EP 1 818 998 B1 discloses a cell barrier for a battery module, comprising a metal body and an insulating layer arranged on the surface of the metal body. The cell barrier is placed between individual cells of the battery module to provide electrical insulation between the cells.

[0010] The object of the invention is to further develop a battery module for a motor vehicle battery or a battery in such a way that, in the event of a thermal event in which a battery cell produces heat, for example due to a short circuit, the transfer of heat to other battery cells is prevented as far as possible.

[0011] This problem is solved according to the invention by a battery module for a motor vehicle battery according to claim 1 and by a battery for a motor vehicle according to claim 5. Advantageous embodiments of the invention are the subject of the dependent claims and the description.

[0012] A battery module according to the invention for a battery, in particular a traction battery, of a motor vehicle comprises at least two spaced-apart battery cells and at least one associated cell barrier. The cell barrier is arranged at least partially between the battery cells.

[0013] To minimize or inhibit heat transfer in the event of a thermal event in a battery cell, such as a short circuit, the cell barrier is at least partially made of a material whose thermal conductivity changes discontinuously when a certain temperature threshold is exceeded or fallen below. A thermal event in a battery cell can be understood as a spontaneous, self-reinforcing, heat-producing process. This can occur, for example, as a result of an internal short circuit. The cell can then burn out or overheat, generating extremely high temperatures that can spread to neighboring battery cells, causing them to also short-circuit and thus enter the thermal event themselves.This can be described as a "runaway" of the battery cell or the battery itself. This can lead to a chain reaction within the vehicle's battery, which is particularly important if it is a high-voltage storage device. The consequence of this chain reaction can be the complete destruction of the entire battery.

[0014] The material used according to the invention for at least partially forming the respective cell barrier has at least one characteristic property that can inhibit or prevent this passage or chain reaction. In particular, the characteristic property is a temperature-dependent thermal conductivity. Simply put, thermal conductivity is the property of a material or element to transport heat through it. As a rule, the thermal conductivity of most materials increases, at least slightly, with increasing temperature. To prevent heat transfer or to severely restrict it at high temperatures, the material according to the invention changes its thermal conductivity discontinuously at a specific temperature or temperature value.In the context of claim 1, "discontinuous" can be understood in particular as "abrupt," meaning that the thermal conductivity changes significantly beyond its normally observed temperature-dependent behavior upon reaching a specific temperature value, which may be a material-specific characteristic. Thus, "discontinuous" here can also be interpreted analogously to its mathematical meaning, as a discontinuous function. Below the temperature value, the thermal diffusivity may have a first value that is significantly lower than a second value of the thermal conductivity above the temperature value. This can occur, for example, when the material changes its state of matter.

[0015] If the material is selected such that its thermal conductivity is significantly lower above a certain temperature than below, heat transfer above that temperature can be particularly effectively inhibited or prevented. This means that when the thermal event described above occurs, heat transfer from one battery cell to another is hindered or prevented, thus at least delaying the chain reaction, which can also be described as a domino effect. The first material, and therefore the cell barrier, can serve as a heat flow regulator. Therefore, the material, or rather the cell barrier, can also be referred to as a heat flow switch.For example, the first material exhibits particularly high thermal conductivity below approximately 130 to 150 degrees Celsius, whereas it exhibits particularly low thermal conductivity at temperatures above 150 degrees Celsius. The material can, for example, be composed of an inhomogeneous mixture, wherein at least one of the materials in the mixture changes its state of matter, particularly at a temperature corresponding to a specific temperature value.

[0016] Furthermore, the material can advantageously exhibit a high degree of adaptability to rough surfaces as a mechanical characteristic. It can also be beneficial, particularly since the material may be in direct contact with the respective battery cell, for the material, and thus at least part of the cell barrier, to have a particularly high electrical resistance. Alternatively, the first material could be a material or material mixture whose thermal conductivity is higher above the temperature threshold than below it. This could inhibit heat flow between adjacent battery cells at low temperatures, thereby enabling, for example, faster heating of each individual battery cell to its optimal operating temperature.

[0017] According to the invention, the cell barrier is formed from at least two layers, a first layer being at least partially made of the first material. The at least two layers, which can be arranged adjacent to one another, allow for the predefining of a further property of the cell barrier in addition to its thermal conductivity. Alternatively or additionally, the at least one further layer, which differs from the first layer, can also serve, for example, as a support for the first layer. By constructing the cell barrier from at least two layers, a cell barrier can be realized which is particularly advantageous for the, in particular, targeted transfer of heat between battery cells.

[0018] According to the invention, a further layer is formed at least partially from a second material which has higher mechanical stability compared to the first material. By using the second material, which has higher mechanical stability than the first material, and in particular particularly high mechanical stability, the at least one further layer can be used, for example, as a support or support structure or frame for the cell barrier or the battery cell. For example, the material can be formed at least partially from, in particular, hard rubber, which, for example, has particularly low thermal conductivity but particularly high electrical resistance.

[0019] According to the invention, a further layer is formed at least partially from a third material, which is a thermal insulator. Its mechanical properties could be, on the one hand, a particularly rigid material, or alternatively, a flexible material. The thermal conductivity of a thermal insulator is particularly low, and its electrical conductivity is also generally low.

[0020] The third material or further layer to be used according to the invention is designed such that it not only serves as a layer between two battery cells, but also completely encases an assembly of several battery cells separated by the other layers or the at least one first layer of the cell barrier. This offers the advantage that the battery cells as a whole, or the battery module, are particularly well protected against environmental influences, and conversely, the environment is particularly well protected from a battery module that might self-destruct due to thermal events.

[0021] In an advantageous embodiment of the invention, the first material is porous and contains a fluid in the resulting cavities, which changes its state of matter at a temperature corresponding to the specified temperature value. In other words, the first material has a porous internal structure, meaning it has a non-zero porosity. Due to this non-zero porosity, the material has cavities within it, which can be, for example, open-pored or closed-pored. Thus, the internal structure can be at least partially sponge-like and / or at least partially foam-like; a superposition or mixture of the two internal structures is also possible. The cavities can be completely and / or at least partially filled with the fluid.The fluid present in the cavities can advantageously be selected such that it undergoes a change of state, for example, from gaseous to liquid and vice versa, at a temperature corresponding to the temperature value at which a discontinuous or abrupt increase or decrease in thermal conductivity is desired. When selecting the fluid, other conditions occurring within the pores or cavities of the material, such as pressure, should be considered. By designing the material as a porous structure filled with the fluid, a cell barrier can be implemented in a particularly simple manner. This barrier changes its thermal conductivity depending on whether the temperature exceeds or falls below a certain value, thus minimizing heat transfer from a battery cell undergoing a thermal event to adjacent battery cells.

[0022] In an advantageous embodiment of the invention, the first material exhibits a phase transition at a temperature corresponding to the specified temperature value. A phase transition, or phase transformation, is understood to be the change or transformation of at least one phase of the material into another phase. This phase change is particularly temperature-dependent, but can also depend on other state variables such as ambient pressure or pressure within the material, and / or similar factors. More precisely, a phase change occurs in the material upon reaching the specified temperature value, as phase interfaces can form, for example, at which properties, particularly thermal conductivity, can change abruptly. By using a material that exhibits a phase transition when passing through the specified temperature value, the change in thermal conductivity can be discontinuous.A wide variety of materials, in particular multi-component systems, i.e. substances which do not consist of only one chemical element, are therefore suitable for use in the cell barrier, which makes a particularly flexible design of the barrier and thus of the battery module according to the invention possible.

[0023] In an advantageous embodiment of the invention, the first layer is formed at least partially from the first material, which discontinuously increases its thermal conductivity when a first temperature value is exceeded. The second layer is formed from a further first material, which discontinuously decreases its thermal conductivity when a second temperature value, which is higher than the first temperature value, is exceeded. By arranging a different first material in at least one of the layers of the cell barrier and by allowing one of the first materials to increase its thermal conductivity with increasing temperature while the other first material decreases its thermal conductivity with increasing temperature, a temperature range can be defined.This temperature window can now be designed, through the use of the first materials, in such a way that the cell barrier is particularly thermally conductive within this temperature range. This allows, for example, heat from the respective battery cell to be transferred to another cooling system or similar, or heat to be exchanged particularly easily between individual battery cells within the temperature window. At temperatures above the upper limit of the temperature window, the thermal conductivity of the cell barrier decreases, thus preventing the propagation of thermal activity from one cell to other battery cells. At or below the lower limit of the temperature window, the thermal conductivity of the cell barrier also decreases, making it particularly advantageous, for example, to achieve the operating temperature of the respective battery cell.

[0024] Furthermore, the invention comprises a battery for a motor vehicle, which includes at least one battery module according to the invention. Advantages and advantageous embodiments of the battery module are to be regarded as advantages and advantageous embodiments of the battery and vice versa.

[0025] Further features of the invention will become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations or on their own.

[0026] The invention will now be explained in more detail with reference to a preferred embodiment and the drawings. The drawings show: The single figure shows a schematic side view of a battery module according to the invention for a motor vehicle battery, with at least two spaced-apart battery cells and with at least one associated cell barrier.

[0027] The figure shows a battery module 1 for a battery 2 of a motor vehicle, with at least two spaced-apart battery cells 3 and with at least one associated cell barrier 4. The at least one cell barrier 4 is arranged at least partially between the battery cells 3.

[0028] In the event of a thermal event, where one of the battery cells 3 produces heat, for example due to a short circuit, particularly in a self-reinforcing manner, and thereby overheats, potentially leading to a so-called burnout of the battery cell 3, it is advantageous for the battery 2 that the transfer of the heat produced during the thermal event to the other battery cells 3 is prevented as much as possible. For this purpose, the respective cell barrier 4 is at least partially formed from a first material 5, which changes its thermal conductivity discontinuously when a certain temperature value is exceeded or fallen below. The material 5 thus acts as a heat flow control device in the cell barrier 4 between at least two battery cells 3 and can be described as a so-called heat flow switch.For example, material 5 is designed in such a way that the thermal conductivity, which can be temperature-dependent over the entire temperature range, is particularly high up to approximately 150 degrees Celsius, or higher than in a temperature range above 150 degrees Celsius, where the thermal conductivity is lower or significantly lower, especially compared to the temperature range below 150 degrees Celsius.

[0029] The thermal conductivity of material 5, and thus at least part of the cell barrier 4, is therefore particularly variable. Ideally, material 5 is selected such that the cell barrier 4 as a whole, especially due to its proximity to the battery cells 3, exhibits a particularly high electrical resistance or is an electrical insulator. Advantageously, the first material 5 is porous, meaning that it contains cavities. These cavities are advantageously at least partially filled with a fluid, or contain a fluid that changes its state of matter at a temperature corresponding to the specified temperature value. Material 5 can thus be considered an inhomogeneous material, in which at least one component or material constituent of material 5 can change its state of matter, particularly at a specific temperature value. Material 5 therefore partially changes its state of matter.Alternatively or additionally, the first material 5 can advantageously exhibit a phase transition at a temperature corresponding to the temperature value. This phase transition can, for example, include a change of state and / or at least one other material-specific order parameter. The order parameter is advantageously selected such that the material 5, which is to be considered as a physical system, undergoes a phase transition, particularly at a temperature corresponding to the temperature value, which is subject to or exhibits a particularly abrupt or discontinuous change, especially in thermal conductivity.

[0030] Advantageously, the cell barrier 4 is formed from at least two layers 6 and 7, wherein a first layer 6 is at least partially formed from the first material 5. Advantageously, a further layer 7 is at least partially formed from a second material 8, which can exhibit, or already exhibits, higher mechanical stability compared to the first material 5. The second material 8 can, for example, be a hard and / or rubber-like material and / or material that contributes to the mechanical stabilization of the battery module and / or is formed from a material mix, wherein the layer formed from material 8 can at least partially assume the functions of a frame. For example, the second material 8 can have a specific three-dimensional structure. Advantageously, its thermal and electrical conductivity are low.Furthermore, the cell barrier 4 can advantageously be formed at least partially from a third material 9, which is a thermal insulator. This material advantageously has particularly high thermal stability; for example, it can be heat-resistant up to over 1000 degrees Celsius and is, in particular, non-flammable. It can, for example, be designed as a foam and thermally insulate several battery cells 3 of the battery module 1 from the environment of the battery 2 or the battery module 1. Alternatively, the cell barrier 4 can be designed such that it is arranged completely between the battery modules 1 or the respective battery modules 1, as shown in the figure.

[0031] In an advantageous embodiment of the battery module 1, the first layer 6 is at least partially formed from the first material 5, which discontinuously increases its thermal conductivity when a first temperature value is exceeded, and the second layer 7 is formed from a further first material 5', which discontinuously decreases its thermal conductivity when a second temperature value, higher than the first temperature value, is exceeded. This makes it possible to form a temperature window with a first low temperature value and a second higher temperature value, so that particularly good heat exchange between the cells is achievable within the temperature window. Conversely, below the first temperature value and above the second temperature value, the cell barrier 4 is particularly efficient at inhibiting or preventing heat exchange between respective adjacent battery cells 3.Thus, in addition to the advantage of an upper temperature value, at which the probability of a battery cell 3 burning out or the spread of the thermal event through a so-called domino effect is reduced, insulation in a lower temperature range is also possible. This temperature range can, for example, be selected so that the cell barrier 4 can be used as a good thermal insulator or heat barrier, so that the respective battery cell 3 can be heated up to its respective optimal operating temperature particularly quickly.

Claims

[1] Battery module (1) for a battery (2) of a motor vehicle, comprising at least two spaced-apart battery cells (3) and at least one associated cell barrier (4), which is arranged at least partially between the battery cells (3), wherein the respective cell barrier (4) is formed at least partially from a first material (5) which changes its thermal conductivity discontinuously when a certain temperature value is exceeded or fallen below, characterized by , that - the cell barrier (4) is formed from at least two layers (6, 7) which are arranged next to each other, wherein a first of the layers (6, 7) is at least partially formed from the first material (5), - wherein another of the layers (6, 7) is at least partially formed from a second material (8) which has a higher mechanical stability compared to the first material (5), and - wherein another of the layers (6, 7) is at least partially formed from a third material (9) which is a thermal insulator and is designed in such a way that it encloses in its entirety an assembly of several battery cells (3) separated by the other layers of the cell barrier. [2] Battery module (1) according to claim 1, characterized by , that the first material (5) is porous and contains a fluid in the resulting cavities which changes its state of matter at a temperature corresponding to the temperature value. [3] Battery module (1) according to claim 1 or 2, characterized by , that the first material (5) exhibits a phase transition at a temperature corresponding to the temperature value. [4] Battery module (1) according to any one of the preceding claims, characterized by, that the first layer (6) is at least partially formed from the first material (5) which discontinuously increases its thermal conductivity when a first temperature value is exceeded, and the second layer (7) is formed from a further first material (5') which discontinuously decreases its thermal conductivity when a second temperature value, which is higher than the first temperature value, is exceeded. [5] Battery (2) for a motor vehicle, characterized by that the battery (2) comprises at least one battery module (1) according to one of the preceding claims.

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