Method for short-circuit testing an electrochemical storage cell

Abstract

The invention relates to a method for short-circuit testing an electrochemical storage cell, comprising the steps of: providing an electrochemical storage cell (1) having an electrolyte (4), freezing the electrochemical storage cell (1) so that the electrolyte (4) becomes non-conducting, applying a measurement voltage, and detecting a short circuit of the electrochemical storage cell (1) as a function of the measurement voltage.

Description

[0001] SHORT-CIRCUIT TESTING PROCEDURE

[0002] AN ELECTROCHEMICAL STORAGE CELL

[0003] The present description relates to a method for short-circuit testing an electrochemical storage cell and a measuring arrangement for short-circuit testing an electrochemical storage cell.

[0004] State of the art

[0005] There are various methods for detecting short circuits in a battery cell. For example, the cell's internal resistance is measured to determine whether a short circuit has occurred. By monitoring the change in internal resistance over time, short circuits or capacity losses can be identified. In addition, a current-voltage characteristic curve can be recorded. A short circuit can be detected by a sudden deviation from the expected characteristic curve. Another option is thermography. This involves recording the heat distribution on the cell's surface. A short circuit often leads to an increase in temperature at the affected area. Finally, electrochemical impedance spectroscopy can be used to measure the cell's impedance at different frequencies. A short circuit leads to a change in the impedance spectrum. These methods are either time-consuming or complex.Resistance measurements are also difficult to interpret because different components of the cell contribute to the measurement result.

[0006] A method that enables the rapid and easy detection of short circuits on an industrial scale is currently lacking. For example, breakdown tests are performed on battery cells before the electrolyte is added. This method is not applicable to finished or aged, fully functional cells. Furthermore, short circuits are difficult to detect during visual inspection. For example, it is not cost-effective to examine the entire separator optically, e.g., with a microscope.

[0007] It is an object of the present description to provide an improved and simple method for short-circuit testing of an electrochemical storage cell and a corresponding measuring arrangement. These objects are achieved by a cover assembly, an energy storage cell, a battery module, and a method for filling an energy storage cell having the features of the independent and subordinate patent claims. Advantageous embodiments and further developments of the invention are set forth in the dependent claims.

[0008] Summary

[0009] It is understood below that each feature described with respect to any embodiment may be used alone or in combination with other features described herein, and may be used in combination with one or more features of any other embodiment, or in any combination of any other embodiment, unless explicitly described as an alternative. Furthermore, equivalents and modifications not described below may be used without departing from the scope of the claimed subject matter.

[0010] The following describes a method for short-circuit testing of an electrochemical storage cell. According to one embodiment, an electrochemical storage cell comprising an electrolyte is first provided. In a further step, the electrochemical storage cell is frozen so that the electrolyte becomes non-conductive. In this frozen state, a measuring voltage is then applied to the electrochemical storage cell. Subsequently, a short circuit in the electrochemical storage cell, if present, is detected as a function of the measuring voltage.

[0011] The proposed concept is based in particular on the considerations outlined below. By freezing the electrochemical storage cell, the electrolyte becomes non-conductive. Freezing can be carried out, for example, in liquid nitrogen. In this frozen state, physical parameters of the cell, such as the (internal) resistance of the cell, can be recorded as a function of the measuring voltage. Alternatively, the cell can be diagnosed in another way. The physical parameters and / or diagnosis of the cell then provide an indication as to whether or not a short circuit is present. According to one embodiment, the measuring voltage is applied for a measuring duration corresponding to a high measuring potential. The electrochemical storage cell is opened after the measuring duration has elapsed. Finally, the short circuit in the electrochemical storage cell is detected by diagnosis, in particular by optical diagnosis.

[0012] It can be assumed that in the frozen state, contact between the cathode and anode essentially exists only via the separator. If, for example, a high potential is applied through the measuring voltage, this potential is present across any short circuit that may be present. This can create a high local temperature, which, during the measurement period, melts a hole in the cell material, for example, in the separator. This hole can be much more easily detected during subsequent analysis. Optical aids can be used to assist the analysis.

[0013] According to one embodiment, the electrochemical storage cell has a separator. The measuring voltage is suitable for locally melting the separator in the event of a short circuit in the electrochemical storage cell.

[0014] According to one embodiment, a short circuit in the electrochemical storage cell is detected by a resistance measurement. The smallest measurable resistance after freezing is the resistance above which the short circuit occurs. This also allows for a qualitative assessment of the short circuit.

[0015] For example, the cell under investigation is first frozen, and a first resistance measurement is taken in this state. Then, a reference cell without a short circuit can be frozen, and a second resistance measurement can be taken in this state. By comparing the two measurements, it can be determined whether a short circuit is present in the cell. The magnitude of the resistance also provides an indication of the short circuit that exists without opening the cell.

[0016] According to one embodiment, the assessment includes locating a visible burn mark. This may require opening the electrochemical storage cell and examining its components, such as the cathode, anode, and / or separator, for visible burn marks. Furthermore, a measuring arrangement for short-circuit testing of an electrochemical storage cell is proposed. According to one embodiment, the measuring arrangement comprises a thermal container with a region for accommodating an electrochemical storage cell containing an electrolyte and configured to accommodate a coolant, wherein the coolant is suitable for freezing the electrochemical storage cell so that the electrolyte becomes non-conductive. A measuring device is provided for applying a measuring voltage to the electrochemical storage cell.

[0017] According to one embodiment, the measuring device is configured to provide the measuring voltage for a measuring duration corresponding to a high measuring potential.

[0018] According to one embodiment, the electrochemical storage cell has a separator. The measuring voltage is suitable for locally melting the separator in the event of a short circuit in the electrochemical storage cell.

[0019] According to one embodiment, the measuring arrangement further comprises means for detecting the short circuit of the electrochemical storage cell by means of diagnosis, in particular by means of optical diagnosis.

[0020] According to one embodiment, the means for detecting the short circuit comprise an optic and / or an optical detector.

[0021] In the following, exemplary embodiments are described with reference to the accompanying drawings. Further details, preferred embodiments, and further developments emerge from them. Identical or similarly functioning components are provided with the same reference numerals in the figures. The components depicted, as well as their relative sizes, are not to be considered to scale. To the extent that components and parts in the various figures have the same function, their description is not necessarily repeated for each of the following figures.

[0022] In detail: Figure 1 shows an embodiment of a measuring arrangement for short-circuit testing of an electrochemical storage cell, and

[0023] Fig. 2 shows a further embodiment of a measuring arrangement for short-circuit testing of an electrochemical storage cell.

[0024] Detailed description

[0025] Figure 1 shows an embodiment of a measuring arrangement for short-circuit testing of an electrochemical storage cell 1. The measuring arrangement is operated according to a method for short-circuit testing of an electrochemical storage cell.

[0026] The measuring arrangement comprises a thermal container 3 and a measuring device 5. To perform the measurement, an electrochemical storage cell 1 is arranged in a region of the thermal container 3. The electrochemical storage cell 1 has an electrolyte 4, for example, an electrolyte that is liquid under standard conditions.

[0027] The thermal container 3 is first filled with a refrigerant, such as liquid nitrogen or a refrigerant mixture. The refrigerant freezes the electrochemical storage cell 1, and the electrolyte 4 becomes non-conductive. This converts the electrochemical storage cell 1 into a measuring state.

[0028] The measuring device 5 now applies a measuring voltage to the electrochemical storage cell 1. For this purpose, corresponding lines are connected to the + and - poles of cell 1. In the frozen state or measuring state, physical parameters of cell 1 can then be recorded as a function of the applied measuring voltage, such as the (internal) resistance of cell 1. For example, the measuring device 5 is set up to perform a resistance measurement. If there is a short circuit in the cell 1 to be tested, the smallest resistance measurable after freezing is the one above which the short circuit lies. This enables a qualitative assessment of the short circuit. The size of the resistance also provides an indication of the short circuit that is present without opening cell 1. Preferably, the resistance measurement is compared with a reference, for example, a cell that is guaranteed not to have a short circuit.Figure 2 shows another embodiment of a measuring arrangement for short-circuit testing of an electrochemical storage cell. The measuring arrangement is operated according to a method for short-circuit testing of an electrochemical storage cell. The electrochemical storage cell 1 comprises a cell core with an anode 11, cathode 12, and a separator 13. Furthermore, the cell 1 comprises corresponding current collectors 14, 15, which are in contact with a positive and negative pole of a cell housing. The electrochemical storage cell has an electrolyte, for example, an electrolyte that is liquid under standard conditions.

[0029] In this example, the measuring arrangement also includes a thermal container 3 and a measuring device 5. To perform the measurement, the electrochemical storage cell 1 is arranged in a region of the thermal container 3. The thermal container 3 is first filled with a coolant, such as liquid nitrogen or a cooling mixture. The coolant causes the electrochemical storage cell 1 to freeze, and the electrolyte 4 becomes non-conductive. In this way, the electrochemical storage cell 1 is transferred to a measuring state.

[0030] During measurement, contact between cathode 12 and anode 11 is essentially only made via separator 13. If a high potential is now applied, it is applied via the short circuit. This creates a high local temperature, which melts a hole (burn mark 16) in the separator. This hole can be detected much more easily during subsequent examination.

[0031] The illustration shows an opened cell 1 with a visible burn mark 16. After the high potential has been applied, the cell 1 is opened for inspection. For this purpose, the internal materials such as the anode 11, cathode 12 and separator 13 can be examined separately to look for any unusual features. A slight short circuit is often very small and difficult to detect. The method involves applying a high potential to the frozen cell 1, which only flows away via the small short circuit and leads to local heat. This damages the separator 13 at this point, for example, which makes it easier to locate the damaged area 16 during visual inspection. This simplifies the detection of short circuits in battery cells. Suitable optics or optical detectors can be used for detection.Although the improved concept has been illustrated and described in detail using exemplary embodiments, it is not limited by the exemplary embodiments. Rather, other variations of the improved concept may be derived therefrom by those skilled in the art without departing from the scope of protection defined by the claims.

[0032] List of reference symbols

[0033] I electrochemical storage cell

[0034] 3 Thermo container 4 Electrolyte

[0035] 5 measuring device

[0036] II Anode

[0037] 12 Cathode

[0038] 13 Separator 14 Current collector

[0039] 15 pantographs

[0040] 16 Burn marks, damaged area

Claims

1. A method for short-circuit testing an electrochemical storage cell, comprising the steps of: - Providing an electrochemical storage cell (1) with an electrolyte (4), - Freezing the electrochemical storage cell (1) so that the electrolyte (4) becomes non-conductive, - Applying a measuring voltage, and - Detection of a short circuit of the electrochemical storage cell (1) as a function of the measuring voltage.

2. The method according to claim 1, wherein - the measuring voltage is applied for a measuring duration corresponding to a high measuring potential, - the electrochemical storage cell (1) is opened after the measurement period has elapsed, and - the short circuit of the electrochemical storage cell (1) is detected by examination, in particular by optical examination.

3. The method according to one of the preceding claims, wherein the detection of a short circuit in the electrochemical storage cell (1) is carried out by a resistance measurement.

4. The method according to one of the preceding claims, wherein the electrochemical storage cell (1) has a separator (13), and the measuring voltage is suitable for locally melting the separator (13) in the event of a short circuit in the electrochemical storage cell (1).

5. The method according to one of the preceding claims, wherein the diagnosis comprises the detection of a visible burn mark (16).

6. A measuring arrangement for short-circuit testing of an electrochemical storage cell, comprising: - a thermal container (3) having a region for receiving an electrochemical storage cell (1) with an electrolyte (4) and arranged to receive a refrigerant, wherein the refrigerant is suitable for freezing the electrochemical storage cell (1) so that the electrolyte (4) becomes non-conductive, and - a measuring device (5) for applying a measuring voltage to the electrochemical storage cell (1).

7. The measuring arrangement according to claim 6, wherein the measuring device (5) is arranged to provide the measuring voltage for a measuring duration corresponding to a high measuring potential.

8. The measuring arrangement according to one of the preceding claims, wherein the electrochemical storage cell (1) has a separator (13), and the measuring voltage is suitable for locally melting the separator (13) in the event of a short circuit in the electrochemical storage cell (1).

9. The measuring arrangement according to one of the preceding claims, further comprising means for detecting the short circuit of the electrochemical storage cell (1) by diagnosis, in particular by optical diagnosis.

10. The measuring arrangement according to one of the preceding claims, wherein the means for detecting the short circuit comprise an optics and / or an optical detector.

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