Battery module with multiple battery cells and battery

Abstract

Battery module comprising a plurality of battery cells (2), in particular lithium-ion battery cells, wherein a balancing element (4) is arranged between at least two battery cells (2), wherein the compensating element (4) is made of a material with dilatant behavior (8), characterized in that the compensating element (4) comprises a first material with dilatant behavior (8) and a second material which is elastic and / or plastic, which includes a flame retardant and / or which includes a phase change material.

Description

State of the art

[0001] The invention relates to a battery module with a plurality of battery cells. The present invention also relates to a battery with such a battery module.

[0002] It is known from the prior art that batteries, such as lithium-ion batteries in particular, consist of at least one battery module or, advantageously, a plurality of battery modules. Furthermore, a battery module preferably comprises a plurality of individual battery cells, which are interconnected to form the battery module. The individual battery cells can be connected in series or in parallel.

[0003] Charging and discharging processes, as well as aging processes within individual battery cells, generate internal forces that cause the individual battery cells to lose their shape during operation. These processes, known as swelling, deform the battery cell casing. Therefore, the battery module must be designed to absorb these internal forces resulting from aging and limit the deformation of the individual battery cell casings. Applying a force to the individual battery cells or their casings to limit deformation is generally referred to as compression.

[0004] In particular, in the case of so-called pouch cells, which are also known as coffee bag cells or pouch cells, and in which stacked electrochemically active components are sealed in a film, only limited forces are permissible for compression, so that it is known from the prior art to insert an elastic element, for example in the form of a foam, between two pouch cells in order to absorb the deformation forces.

[0005] For example, the charge-dependent deformation of pouch cells with graphite anodes and NCA cathodes, known at the time of application and not compressed, ranges between 5% and 15% of the pouch cell volume. During charging, the volume of pouch cells increases due to the chemical processes occurring, so that a charged pouch cell exhibits the greatest volume expansion. Conversely, the volume of pouch cells decreases during discharging, so that a discharged pouch cell exhibits the smallest volume expansion. Furthermore, the aging state of the pouch cells also influences the volume expansion, with the volume increasing further with increasing age. Whether future battery cells will exhibit similar swelling behavior cannot be assessed at the time of application, as future battery cells with SiC anodes, for example, swell by up to 300%.

[0006] For example, a battery module is known from publication WO 2010 / 040520 A2 which has a shock-absorbing material between two battery cells, wherein the battery cells are housed in a rigid module casing.

[0007] The state of the art in this regard is represented in particular by the publications JP 5 039 866 B2, DE 10 2013 021 134 A1 and DE 10 2014 019 001 A1. Disclosure of the invention

[0008] A battery module with a plurality of battery cells having the features of the independent claim has the advantage that compression of the plurality of battery cells is possible and a compensating element can absorb volume changes of the battery cells due to swelling processes and the compensating element can also compensate for sudden, shock-like loads, for example as a result of an accident or an impact.

[0009] According to the invention, a battery module with a plurality of battery cells is provided, wherein the battery cells are in particular lithium-ion battery cells.

[0010] A balancing element is arranged between at least two battery cells.

[0011] Furthermore, the compensating element is made of a material that exhibits dilatant behavior.

[0012] The measures listed in the dependent claims enable advantageous further developments and improvements of the device or method specified in the independent claim.

[0013] A material exhibiting dilatant behavior is defined as one in which its viscosity increases exponentially with the shear rate acting upon it. Such a material therefore displays a shear-rate-dependent viscosity and is shear-hardening or shear-thickening. Consequently, the elasticity of the dilatant material is also dependent on the shear rate acting upon it.

[0014] In particular, the dilatant behavior of the material of the compensating element can be described by the following equation. η=k(ddtγ)n

[0015] In this, η describes a viscosity of the dilatant material and dγ|dt a shear rate acting on the dilatant material as a time derivative of a velocity y .

[0016] Furthermore, no constant of proportionality and n denotes an exponential factor, where n > 1.

[0017] Thus, a dilatant material is soft, flexible and elastic when only low shear rates, which can occur particularly during the operation of a battery module due to swelling processes, act on the dilatant material.

[0018] Furthermore, a dilatant material can also absorb high shear rates, which can occur particularly during shock-like loads acting on the battery module from the outside, by means of, for example, the molecules of the dilatant material interlocking with each other.

[0019] Such a material offers the particular advantage that movements of the battery cells due to their own weight, caused by sudden, shock-like loads, can be compensated for by the balancing element. This prevents, for example, the loss or destruction of electrical contacts between battery cells.

[0020] Furthermore, it is advantageous if the battery module has a clamping device that clamps the majority of battery cells together.

[0021] It is advantageous if the material is designed in such a way that the dilatant behavior of the compensating element material has a first shear rate range in which the viscosity is essentially constant above a shear rate, and that the dilatant behavior of the compensating element material has a second shear rate range in which the viscosity increases exponentially above a shear rate.

[0022] This offers the advantage that, firstly, in the first range of low shear rates, which refers to ordinary loads on the battery cells occurring during operation, reliable compression of the battery cells is possible, and secondly, in the range of higher shear rates, which refers to sudden shock loads, for example, the battery cells can be reliably held in their position.

[0023] According to an advantageous aspect of the invention, the battery cells are each designed as pouch cells in which the electrochemical components of the battery cell are contained in a foil.

[0024] A compensating element made of a material with dilatant properties offers the advantage that it allows for compression of the pouch cells without exceeding the compression force limited to pouch cells, thus preventing damage. Furthermore, the compensating element made of a material with dilatant properties can also compensate for the deformation of individual pouch cells without falling below a minimum compression force.

[0025] According to another advantageous aspect of the invention, the battery cells each comprise a solid electrolyte. The material, exhibiting dilatant behavior, can ensure reliable compression without falling below a minimum compression force or exceeding a maximum force.

[0026] Advantageously, the clamping device comprises, for example, a first clamping plate and a second clamping plate, with the majority of battery cells arranged between the first and second clamping plates. Furthermore, the clamping device includes a clamping element, which is in particular a clamping band, connecting the first and second clamping plates. This enables the first and second clamping plates to press the majority of battery cells together, and the clamping force can be precisely adjusted using the clamping element.

[0027] It is advantageous to continue to have a cooling element positioned between two battery cells. The dilatant behavior of the compensating element's material offers the benefit that the connection between the two battery cells and the cooling element is maintained even under shock loads.

[0028] According to the invention, the compensating element comprises a first material with dilatant behavior and further comprises a second material.

[0029] The second material can be elastic and / or plastically deformable, so that, in addition to the dilatant behavior of the first material, age-related volume deformations of the battery cells during operation can be better compensated for. The second material can also include flame protection. Furthermore, the second material can, for example, also include a phase-change material to act as a cooling element.

[0030] It should also be noted that the majority of battery cells of the battery module and the compensating element arranged between two battery cells with dilatant behavior can also be arranged in a housing of a battery module or in a housing of a battery, wherein preferably the walls of the respective housing form the clamping device and clamp the majority of battery cells together.

[0031] Furthermore, the invention also relates to a battery with a battery module, which has just been described.

[0032] Dilatant materials are known from the prior art. For example, dispersions, such as suspensions, emulsions or foams, with a high concentration of particles or gelled components that have too low a proportion of solvent or plasticizer, can form a material with dilatant behavior according to the invention.

[0033] In particular, highly concentrated colloidal or non-colloidal suspensions can form a material with dilatant behavior according to the invention.

[0034] In particular, quartz can form a material with dilatant behavior in acrylates according to the invention.

[0035] In particular, a PCV plastisol or ceramic compounds can also form a material with dilatant behavior according to the invention.

[0036] Furthermore, it is possible to use the mixture known as "Silly Putty", consisting of 65% dimethylsiloxane, 17% silicon dioxide, 9% thixatrol, 4% polydimethylsiloxane, 1% decamethylcyclopentasiloxane, 1% glycerin and 1% titanium dioxide, as a dilatant material. Brief description of the drawings

[0037] Exemplary embodiments of the invention are shown in the drawings and explained in more detail in the following description.

[0038] They show: Fig. 1 in a schematic side view an embodiment of a battery module according to the invention and Fig. 2 an exemplary, dilatant behavior of a material of a compensating element.

[0039] The Fig. Figure 1 schematically shows a side view of an embodiment of a battery module 1 according to the invention.

[0040] The battery module 1 comprises a plurality of battery cells 2, which are arranged side by side. Specifically, the battery cells 2 are each designed as lithium-ion battery cells. Furthermore, the battery cells 2 can each be designed as pouch cells. Additionally, the battery cells 2 can each comprise a solid electrolyte.

[0041] Furthermore, the battery module 1 has a clamping device 3 which clamps the majority of battery cells 2 together.

[0042] According to the Fig. In the embodiment shown in Figure 1, the clamping device 3 comprises a first clamping plate 31 and a second clamping plate 32, wherein the majority of battery cells 2 are arranged between the first clamping plate 31 and the second clamping plate 32.

[0043] Furthermore, the clamping device 3 comprises, according to the one described in the Fig. In the embodiment shown in Figure 1, a clamping element 33, which is in particular designed as a clamping band 34, wherein the clamping element 33 connects the first clamping plate 31 and the second clamping plate 32 together.

[0044] This makes it possible for the first clamping plate 31 and the second clamping plate 32 to press the majority of battery cells 2 together due to the connection by means of the clamping element 33.

[0045] In this arrangement, a balancing element 4 can be arranged between two adjacent battery cells 2, which is made of a material with dilatant behavior, the properties of a dilatant material having already been explained at the outset.

[0046] Furthermore, from the Fig. 1 to recognize that a cooling element 5 can also be arranged between two adjacent battery cells 2.

[0047] The Fig. Figure 2 schematically shows a dilatant behavior 8 of the material of the compensating element 4, in particular according to the embodiment of Fig. 1.

[0048] This is in the Fig. 2 A viscosity 6 for the material of the compensating element 4 is plotted against a shear rate 7 acting on the material of the compensating element 4. A logarithmic representation has been chosen for both axes.

[0049] This is from the Fig. 2. It can be seen that the dilatant behavior 8 exhibits a first region 71 of the shear rate 7 in which the viscosity 6 is essentially constant over the shear rate 7. In the first region 71 of the shear rate 7, the material with the dilatant behavior 8 is comparable to a Newtonian fluid.

[0050] Furthermore, from the Fig. 2 to recognize that the dilatant behavior 8 has a second region 72 of the shear rate 7 in which the viscosity 6 increases exponentially with respect to the shear rate 7.

[0051] It should be noted at this point that the described embodiment is only intended to serve a better understanding and does not limit the invention.

Claims

[1] Battery module comprising a plurality of battery cells (2), in particular lithium-ion battery cells, wherein a balancing element (4) is arranged between at least two battery cells (2), wherein the compensating element (4) is made of a material with dilatant behavior (8), characterized by , that the compensating element (4) comprises a first material with dilatant behavior (8) and a second material which is elastic and / or plastic, which includes a flame retardant and / or which includes a phase change material. [2] Battery module according to the preceding claim 1, characterized by , that the battery module (1) comprises a clamping device (3) which clamps the majority of battery cells (2) together. [3] Battery module according to any one of the preceding claims, characterized by, that the dilatant behavior (8) of the compensating element (4) has a first region (71) of a shear rate (7) in which a viscosity (6) is essentially constant over a shear rate (7) and that the dilatant behavior (8) of the compensating element (4) has a second region (72) of a shear rate (7) in which a viscosity (6) increases exponentially over a shear rate (7). [4] Battery module according to any one of the preceding claims, characterized by , that the battery cells (2) are each designed as pouch cells. [5] Battery module according to any one of the preceding claims, characterized by , that the battery cells (2) each comprise a solid electrolyte. [6] Battery module according to any one of the preceding claims, characterized by , that the clamping device (3) comprises a first clamping plate (31) and a second clamping plate (32) and the majority of battery cells (2) are arranged between the first clamping plate (31) and the second clamping plate (32) and that a clamping element (33), in particular a clamping band (34), connects the first clamping plate (31) and the second clamping plate (32) together. [7] Battery module according to any one of the preceding claims, characterized by , that a cooling element (5) is arranged between two battery cells (2). [8] Battery comprising a battery module according to any one of the preceding claims 1 to 7.

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