Method for determining a damage rate of a battery cell for an electrical energy storage device of a motor vehicle, method for determining an adjustable pressure, computer program product, computer-readable storage medium, electronic computing device and pressure regulating device

Abstract

Methods for determining an injury rate (D C ) a battery cell (16) for an electrical energy storage device of a motor vehicle that is at least partially electrically powered by means of an electronic computing device (12), comprising the steps: - Determining the capacity degradation of the battery cell (16) as a function of a force generated due to cell swelling of the battery cell (16); - Determining the state of health (SOH) of the battery cell (16); and - Determining the damage rate (D C ) depending on capacity degradation and state of health (SOH), where the damage rate (D C ) is determined on the basis of a covariance procedure or the damage rate (D C ) based on a derivation using the formula: DC = | d SOHC d ETP | is determined, where D C the damage rate, SOH cthe state of aging and ETP corresponds to an energy flow.

Description

[0001] The invention relates to a method for determining the damage rate of a battery cell for an electrical energy storage device of an at least partially electrically powered motor vehicle using an electronic computing device. Furthermore, the invention relates to a method for determining an adjustable pressure for at least one battery cell for an electrical energy storage device of an at least partially electrically powered motor vehicle using a pressure regulating device. The invention also relates to a computer program product with program code means and a computer-readable storage medium.Furthermore, the invention relates to an electronic computing device for determining a damage rate of a battery cell for an electrical energy storage device of an at least partially electrically powered motor vehicle, and a pressure regulating device for determining an adjustable pressure for at least one battery cell for an electrical energy storage device of an at least partially electrically powered motor vehicle.

[0002] Prior art already describes methods for clamping cell blocks, particularly battery cell blocks, in which a corresponding pressure is built up during assembly. The battery cells are pressed into a defined installation space with a certain structural stiffness. As they age, the cells tend to increase in thickness, resulting in a force within the block that increases with age. This is known as cell thickness growth, which thus leads to pressure development within the block.

[0003] To slow down pressure development due to aging, compressible mats, so-called tensioning mats, are used. However, these tensioning mats consume installation space, have an insulating effect on the battery cells, and influence their thermal connection. Currently, the design of the tensioning mats focuses solely on slowing down force development, neglecting the potential reduction in lifespan at certain force levels.

[0004] DE 10 2019 004 928 A1 relates to a battery for a motor vehicle that is at least partially electrically powered, comprising a plurality of battery cells, wherein each of the battery cells has a first volume in a discharged state and a second volume different from the first volume in a charged state, and comprising at least one first flexible clamping device for exerting a predetermined force on the plurality of battery cells in the discharged state and in the charged state, wherein the at least first flexible clamping device is designed such that, in order to exert the predetermined force on the plurality of battery cells, the at least first flexible clamping device is supported at least on a motor vehicle component of the motor vehicle.

[0005] DE 10 2019 007 363 A1 relates to an electrical energy storage device with at least one electrode stack, comprising a plurality of layers of electrodes arranged one above the other in a stacking direction and separators arranged between the electrodes. A first pressure plate and a second pressure plate serve to exert pressure on the at least one electrode stack arranged between the pressure plates. At least one actuator is provided for moving at least one of the pressure plates. A control device is provided for controlling the at least one actuator. The pressure plates are coupled to each other by the at least one actuator. By controlling the at least one actuator via the control device, the distance between the pressure plates can be changed.

[0006] DE 10 2018 123 682 A1 relates to a modular battery comprising several battery cells and a detection unit for recording the battery's operating state. An actuator is provided for this purpose to adjust the pressure in the battery depending on the detected operating state.

[0007] The object of the present invention is to provide a method for determining a damage rate of a battery cell, a method for determining an adjustable pressure for at least one pressure regulating device, a computer program product, a computer-readable storage medium, an electronic computing device and a pressure regulating device, by which improved operation of a battery cell in an electrical energy storage device can be achieved.

[0008] This problem is solved by the independent claims. Advantageous embodiments are specified in the dependent claims. One aspect of the invention relates to a method for determining the damage rate of a battery cell for an electrical energy storage device of an at least partially electrically powered motor vehicle using an electronic computing device. This involves determining the capacity degradation of the battery cell as a function of a force generated by cell swelling, determining the aging state of the battery cell, and determining the damage rate as a function of the capacity degradation and the aging state.

[0009] In particular, this allows for the description, measurement, and quantification of the cell- and module-specific, age-related pressure dependence of a battery cell, such as a lithium-ion cell. Data is then recorded, and the module design is optimized to increase its lifespan. This can lead to a longer product lifespan and increased holding capacity over a wider lifespan, thereby maximizing the overall range.

[0010] In particular, the invention describes the quantification and interaction of force and cell aging, and a corresponding passive and active control of pressure and force regulation via aging. The first aspect includes, in particular, measurement and evaluation. For this purpose, lithium-ion cells are clamped in a mechanical setup, for example, and cycled with an electrical profile. It is important to note that the measurement setup must be capable of measuring the forces and cell growth.

[0011] The measurements can be used to derive corresponding characteristic curves through evaluation, which can then be used to adjust the pressure control in a cell-specific manner.

[0012] The constant pressure conditions allow for the significant measurement of pressure dependencies during aging. To quantify the force dependency, a specific evaluation is required, which is described below and has also been validated by real battery life tests.

[0013] The injury rate is determined using a covariance method. In particular, the injury rate can be calculated using the formula: DC=|Cov(SOHC,ETP)Var(ETP)| be determined, where D c the damage rate, SOH c The aging state and ETP correspond to an energy flow. In particular, the force dependence of the capacity degradation can thus be determined via the damage rate. In the present embodiment, the damage rate is determined specifically using the covariance.

[0014] Alternatively, the damage rate is calculated based on a derivation using the formula: DC=|dSOHCdETP| determined, where D c the damage rate, SOH c The aging state and ETP correspond to an energy flow rate. In particular, the damage rate can alternatively be determined by directly deriving the trend.

[0015] Another aspect of the invention relates to a method for determining an adjustable pressure for at least one battery cell for an electrical energy storage device of an at least partially electrically powered motor vehicle by means of a pressure regulating device, wherein a damage rate is determined on the basis of a method according to the preceding aspect, and a continuously exerted pressure on the battery cell is determined depending on the determined damage rate.

[0016] Preferably, a continuous pressure or force between 9 kilonewtons and 11 kilonewtons, in particular 10 kilonewtons, can be set.

[0017] In particular, it has been shown that the damage rate exhibits a parabolic curve with respect to the applied pressure. Specifically, this implies that an optimal operating point for the counterforce lies in the range of 10 kilonewtons, and conversely, the service life can be maximized if the battery cell is either inherently designed to operate only within this range or is regulated within this range by an external control system, particularly via the pressure regulating device.

[0018] The methods presented are in particular computer-implemented methods. Therefore, a further aspect of the invention relates to a computer program product with program code means which, when the program code means are executed by the electronic computing device, cause a method according to the first aspect of the invention or the second aspect of the invention.

[0019] Furthermore, the invention also relates to a computer-readable storage medium containing a computer program product according to the preceding aspect. The computer program product can also be referred to as a computer program.

[0020] A further aspect of the invention describes an electronic computing device for determining the damage rate of a battery cell for an electrical energy storage device of an at least partially electrically powered motor vehicle, wherein the electronic computing device is configured to carry out a method according to the preceding aspect. In particular, the method is carried out by means of the electronic computing device.

[0021] The electronic computing device includes, for example, processors, circuits, especially integrated circuits, and other electronic components in order to carry out the corresponding process steps.

[0022] Furthermore, the invention also relates to a pressure regulating device for determining an adjustable pressure for at least one battery cell for an electrical energy storage device of an at least partially electrically powered motor vehicle, wherein the pressure regulating device is configured to carry out a method according to the second aspect of the invention. The method is carried out in particular by means of the pressure regulating device.

[0023] Advantageous embodiments of the different aspects of the invention are to be regarded as advantageous embodiments of the other aspects of the invention.

[0024] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0025] This shows: Fig. 1 a schematic view of an embodiment of a pressure regulating device with an additional embodiment of an electronic computing device; Fig. 2 a schematic SOH-ETP diagram; and Fig. 3 a schematic force-damage rate diagram.

[0026] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0027] Fig. Figure 1 shows a schematic block diagram according to an embodiment of a pressure regulating device 10. In the present embodiment, the pressure regulating device 10 has at least one electronic computing unit 12, which is configured to control a pressure control unit 14. Furthermore, the electronic computing unit 12 can also be used to determine a damage rate D. c ( Fig. 3) be trained. Alternatively, to determine the damage rate D c Another electronic computing device may also be provided.

[0028] In particular, a damage rate D ca battery cell 16 is provided. The battery cell 16 is, in particular, a lithium-ion battery cell. In the present embodiment, the battery cell 10 is located, in particular, in a housing 18, so that a corresponding force K can be exerted on the battery cell 16.

[0029] In particular, it is thus intended that the quantification and interaction of the force K on cell aging and the passive and active control of pressure regulation can be adapted accordingly via aging.

[0030] This includes, in particular, the specific measurement and evaluation. Here, the lithium-ion battery cells 16 are clamped in an experimental setup and cycled with an electrical profile. This experimental setup can also be replicated, for example, using the pressure regulation device 10. It is important to note that the measurement setup must be capable of measuring the forces K and the cell growth accordingly. Using the measurements, characteristic curves can be derived through evaluation, which the pressure regulation system can then use to set the optimal pressure or force K for each cell. The constant pressure conditions allow the pressure dependencies during aging to be measured significantly. To quantify the force dependency, a specific evaluation is required, which is also validated by real battery lifetime tests.

[0031] Fig. Figure 2 shows a schematic ETP-SOH diagram. ETP refers in particular to the so-called Energy Throughput, which is given in watt-hours and corresponds to the energy flow. The aging state, in particular the State of Health (SOH), is also plotted. In this embodiment, the SOH is plotted as a percentage, where an ETP value of 0 represents 100 percent State of Health. Furthermore, different characteristic curves are shown, specifically those of battery cells 16 under different forces, corresponding to a cell test 22. Finally, an actual battery test 20 is shown, which validates the theoretical determinations.

[0032] In particular, the Fig. 2. the force dependence of capacity degradation, which is determined by the damage rate D c is determined. The damage rate D cThis is calculated using the following two mathematical rules. Firstly, via the covariance: DC=|Cov(SOHC,ETP)Var(ETP)| or alternatively via the direct derivation of the course: DC=|dSOHCdETP|

[0033] The battery test 20 according to Fig. 2 was carried out under real tension conditions and corresponding strains and forces K were measured over the aging process using special measuring technology.

[0034] Fig. Figure 3 shows a schematic force-damage rate diagram, where the force K is given in kilonewtons and the damage rate D c in percent of megawatt hours. It is particularly noticeable here that the derived damage rates D c from the cell level to a real battery measurement. Furthermore, a parabolic progression of the damage rates D can be observed in both the battery measurement and the corresponding cell measurement.c The force K is determined via the applied pressure. This results in an optimal operating point for the counterforce being in the range of 10 kilonewtons, and conversely, the service life can be maximized if the battery or electrical energy storage device is either inherently designed to operate only within this range or is regulated within this range by an external control system, for example with a pressure regulating device 10.

[0035] The invention thus yields improvements and recommendations. Firstly, it demonstrates active pressure regulation for increased service life. Furthermore, it shows that the forces K within the module and across the cell array should be kept as constant as possible, since otherwise inhomogeneous force distributions lead to inhomogeneous pressure developments. In addition, it is evident that modules or cell arrays should be as compact as possible and constructed in such a way that the pressure or force K remains within the optimal range throughout aging and cell growth. Reference symbol list 10 Pressure regulating device 12 electronic computing equipment 14 Pressure control unit 16 battery cells 18 cases 20 Battery test 22-cell test K force ETP energy flow SOH aging state D c Damage rate

Claims

[1] Methods for determining an injury rate (D C ) a battery cell (16) for an electrical energy storage device of a motor vehicle that is at least partially electrically powered by means of an electronic computing device (12), comprising the steps: - Determining the capacity degradation of the battery cell (16) as a function of a force generated due to cell swelling of the battery cell (16); - Determining the state of health (SOH) of the battery cell (16); and - Determining the damage rate (D C ) depending on capacity degradation and state of health (SOH), where the damage rate (D C ) is determined on the basis of a covariance procedure or the damage rate (D C ) based on a derivation using the formula: DC=|dSOHCdETP| is determined, where D C the damage rate, SOH cthe state of aging and ETP corresponds to an energy flow. [2] Method according to claim 1, characterized by , that the damage rate (D C ) using the formula: DC=|Cov(SOHC,ETP)Var(ETP)| is determined, where D C the damage rate, SOH c the state of aging and ETP corresponds to an energy flow. [3] Method for determining an adjustable force (K) for at least one battery cell (16) for an electrical energy storage device of an at least partially electrically powered motor vehicle by means of a pressure regulating device (10), wherein a damage rate (D C ) is determined on the basis of a method according to one of claims 1 to 2, and depending on the determined damage rate (D C ) a continuously exerted force (K) on the battery cell (16) is determined. [4] Method according to claim 3, characterized by, that a continuous force (K) between 9kN and 11kN, in particular 10kN, is set. [5] Computer program product comprising program code means which cause an electronic computing device (12) to perform a method according to one of claims 1 to 2 and / or 3 and 4 when the program code means are processed by the electronic computing device (12). [6] Computer-readable storage medium containing a computer program product according to claim 5. [7] Electronic computing device (12) for determining a damage rate (D C ) a battery cell (16) for an electrical energy storage device of an at least partially electrically powered motor vehicle, wherein the electronic computing device (12) is configured to carry out a method according to one of claims 1 to 2. [8] Pressure regulating device (10) for determining an adjustable force (K) for at least one battery cell (16) for an electrical energy storage device of an at least partially electrically powered motor vehicle, wherein the pressure regulating device (10) is configured to carry out a method according to one of claims 3 or 4.

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