Battery cell detection method and battery cell detection device

Abstract

The invention discloses a battery cell detection method and a battery cell detection device. The detection method is used for determining whether the internal short circuit risk exists in the battery cell to be detected after liquid injection infiltration. The detection method comprises the following steps: preprocessing a to-be-detected battery cell to enable the to-be-detected battery cell to enter a test state; the pretreatment at least comprises pressurization and heating of the to-be-tested cell and maintenance for a first time period; continuously applying excitation voltage to the to-be-tested battery cell in the test state for a second time period, and acquiring response current of the to-be-tested battery cell in the second time period; and determining whether the to-be-detected cell has an internal short circuit risk based on the response current. According to the invention, whether the internal short circuit risk exists in the battery cell or not can be rapidly and accurately detected before formation, so that defective products are rejected in advance, and the production safety and efficiency are improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a method and apparatus for rapid detection of internal short-circuit cells. Background Technology

[0002] Internal short circuits within the cell are a significant cause of battery safety issues during lithium-ion battery production. These short circuits can originate from metal impurities, separator defects, burrs, etc., introduced during the manufacturing process. They can trigger thermal runaway or even fire and explosion during formation or subsequent charging and discharging, resulting in serious safety risks and economic losses.

[0003] Current technologies commonly employ internal short-circuit detection methods that rely on monitoring open-circuit voltage after formation. This method requires two static open-circuit voltage measurements after formation, and the presence of micro-short circuits in the cell is indirectly determined by comparing the voltage drop values ​​obtained from the two measurements. This method has an excessively long testing cycle, affecting production efficiency and consuming testing space. Furthermore, detection can only be performed after formation, making it impossible to identify defects before the cell enters high-risk processes, thus leaving the formation process itself vulnerable to safety incidents caused by internal short circuits. Summary of the Invention

[0004] To address at least one of the aforementioned technical problems, this application discloses a cell testing method and a cell testing apparatus. The cell testing method can quickly and accurately detect the presence of internal short-circuit risks in cell formation before the formation process, thereby eliminating defective products in advance and improving production safety and efficiency.

[0005] The first aspect of this application provides a cell testing method, which is used to determine whether a cell under test has an internal short circuit risk after being injected with electrolyte; wherein, the testing method may include: pre-treating the cell under test to bring it into a test state; the pre-treating includes at least pressurizing and heating the cell under test and maintaining it for a first time period; continuously applying an excitation voltage to the cell under test in the test state for a second time period, and acquiring the response current of the cell under test during the second time period; and determining whether the cell under test has an internal short circuit risk based on the response current.

[0006] According to some embodiments of this application, the pretreatment satisfies at least one of the following features: (1) the pressure of the pressurization is 0.5-1 MPa; (2) the heating maintains the surface temperature of the battery cell under test at 50-60°C; and (3) the first time period is 20-30 s.

[0007] According to some embodiments of this application, the excitation voltage is a constant DC voltage of 5-10μV; the second time period is not less than 20s.

[0008] According to some embodiments of this application, the second time period is 20s; the step of determining whether the cell under test has an internal short circuit risk based on the response current includes: obtaining the average current value of the response current of the cell under test in the last segment of the second time period; the last segment does not exceed 5s; and determining whether the cell under test has an internal short circuit risk based on the relationship between the average current value and the current threshold.

[0009] According to some embodiments of this application, when the magnitude relationship indicates that the average current is not less than the current threshold, it is determined that the cell under test has an internal short circuit risk; when the magnitude relationship indicates that the average current is less than the current threshold, it is determined that the cell under test has no internal short circuit risk.

[0010] A second aspect of this application provides a battery cell testing device for determining whether a battery cell under test has an internal short-circuit risk after being injected with electrolyte. The battery cell testing device may include: a state adjustment component configured to pre-process the battery cell under test to bring it into a test state; the pre-processing includes at least pressurizing and heating the battery cell under test and maintaining this for a first time period; an excitation component configured to continuously apply an excitation voltage to the battery cell under test in the test state for a second time period; a response component configured to acquire the response current of the battery cell under test during the second time period; and a processing component configured to determine whether the battery cell under test has an internal short-circuit risk based on the response current.

[0011] According to some embodiments of this application, the state adjustment component includes a pressure application unit and a heating unit; the pressure application unit is configured to apply a pressure of 0.5-1 MPa to the battery cell under test, and the heating unit is configured to accelerate the battery cell under test to maintain its surface temperature at 50-60°C.

[0012] According to some embodiments of this application, the excitation component and the response component are respectively electrically connected to the cell under test to continuously apply an excitation voltage to the cell under test in the test state and to obtain the response current of the cell under test.

[0013] According to some embodiments of this application, in order to determine whether the battery cell under test has an internal short circuit risk, the processing component is configured to: obtain the average current value of the response current of the battery cell under test in the last segment of the second time period; the last segment does not exceed 5s; and determine whether the battery cell under test has an internal short circuit risk based on the relationship between the average current value and the current threshold.

[0014] According to some embodiments of this application, the processing component is configured to: determine that the cell under test has an internal short circuit risk when the magnitude relationship indicates that the average current is not less than the current threshold; and determine that the cell under test has no internal short circuit risk when the magnitude relationship indicates that the average current is less than the current threshold.

[0015] The cell testing method disclosed in this application has a short testing cycle (e.g., less than 1 minute), which is more than a thousand times more efficient than the traditional open-circuit voltage monitoring method (OCV monitoring method) that requires 1-2 weeks, greatly saving time and inventory costs. Furthermore, the cell testing method disclosed in this application can screen for internal short circuit risks after electrolyte injection and before formation, eliminating potentially hazardous cells in advance and reducing the safety risks of thermal runaway, fire, and explosion caused by internal short circuits during the formation process. In addition, this application uses μV-level voltage excitation, which has minimal impact on the cell's state. Judgment is made by directly observing the current decay to a steady state, which is more direct and reliable than indirect voltage drop monitoring.

[0016] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0017] This application will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein: Figure 1 This is an exemplary flowchart of a cell testing method according to some embodiments of this application; Figure 2 This is an exemplary composition diagram of a battery cell testing apparatus for implementing the battery cell testing method according to some embodiments of this application; Figure 3 An exemplary schematic diagram of the response current curve of a normal battery cell is shown; Figure 4 An exemplary schematic diagram of the response current curve of a battery cell with internal short-circuit risk is shown; Figure 5 These are exemplary teardown diagrams of battery cells with internal short-circuit risk, as shown in some embodiments of this application. Detailed Implementation

[0018] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0019] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this application's specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The terms "comprising" or "including," as used in this application, mean that an element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The terms "and / or" or "and / or" as used in this application include any and all combinations of one or more of the associated listed items.

[0020] The terms “comprising,” “having,” and their cognates used in this application are intended only to indicate a particular feature, number, step, operation, element, component, or combination thereof, and should not be construed as excluding, firstly, the presence of one or more other features, numbers, steps, operations, elements, components, or combinations thereof, or adding the possibility of one or more features, numbers, steps, operations, elements, components, or combinations thereof.

[0021] As mentioned in the background section, existing internal short-circuit detection methods are not only inefficient but also fail to guarantee cell safety. Therefore, this application provides a cell testing method to address the problems of long testing cycles, delayed processes, resource consumption, and the inability to identify cells with internal short-circuit risks before formation, thereby reducing safety risks in the formation process and improving production efficiency and cell safety.

[0022] The following describes some preferred embodiments of this application. It should be noted that the following description is for illustrative purposes only and is not intended to limit the scope of protection of this application. The steps involved in this application may be performed precisely in sequence, or various steps may be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more steps may be removed from these processes.

[0023] The cell testing method provided in this application can be referenced. Figure 1This cell testing method 100 can be used to determine whether a cell under test has an internal short circuit risk after being injected with electrolyte. It is known that the production process of a lithium-ion battery cell can include the front-end electrode fabrication process (e.g., material preparation, slurry mixing, electrode coating, electrode rolling, electrode slitting, sheet forming, etc.), the mid-end cell assembly process (e.g., die-cutting, cell winding / stacking, casing, electrolyte injection, wetting, sealing, etc.), and the back-end activation and testing process (e.g., formation, capacity testing, testing and sorting, etc.). Existing testing methods are performed in the back-end production process, which not only results in a long testing cycle but also affects production efficiency. The cell testing method 100 provided in this application is performed in the mid-end production process, that is, after electrolyte injection and wetting. The testing time is short, the testing efficiency is high, and it does not affect production efficiency. The cell under test can be a lithium-ion cell with any cathode system, such as LFP, NCM, LNMO, LMO, LFMP, LCO, etc. Figure 1 ,like Figure 1 As shown, the cell testing method 100 may include the following steps.

[0024] Step 110: Preprocess the battery cell under test to bring it into the test state.

[0025] In some embodiments, the test state may refer to the internal electrochemical steady state of the battery cell under test, which can be achieved through a pretreatment that includes at least pressurizing and heating the battery cell under test and maintaining it for a first time period. In some examples, the pressurization can be performed by a pressure-applying element such as a mechanical press, a pneumatic press, or a hydraulic press. Taking a pneumatic press as an example, the battery cell under test can be placed on the machine platform of the pneumatic press, and a cylinder drives the end actuator (such as a flat pressure head) to move toward the battery cell under test, applying pressure upon contact. The applied pressure can be 0.5-1 MPa, for example, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, or any increment or decrement of the above values. Pressurization reduces the interfacial contact resistance between the electrode and the diaphragm, shortening the time required to reach a steady state. The heating can be performed by a heating element such as a heating plate. For example, a heating plate can be attached to the surface of the battery cell under test to heat the battery cell under test, maintaining its surface temperature at 50-60°C. For example, 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, or any increment or decrement of these values. Heating can reduce the internal polarization resistance of the battery cell, thereby accelerating its attainment of electrochemical steady state.

[0026] refer to Figure 2 The exemplary composition diagram of the cell testing apparatus according to some embodiments of this application is shown, such as... Figure 2As shown, heating elements H1 and H2 clamp the battery cell C under test, and then place them together on the pressure-applying element, such as the machine base B of a pneumatic compressor. When cylinder G is activated, the final actuator P moves downwards to apply pressure to the battery cell C. In all the above components, heating elements H1 and H2 can be thin-film heating elements, including but not limited to mica heating elements, etched foil heating elements (metal substrate type), and PTC heating elements (ceramic substrate type). These heating elements can remain unchanged and function normally under pressure. Alternatively, silicone heating elements, polyimide (PI) film heating elements, carbon fiber heating elements, and polyester (PET) film heating elements can be used, with thin aluminum or stainless steel plates attached to both sides to distribute pressure and prevent deformation of the heating elements from affecting the heating function.

[0027] In some embodiments, the first time period can be 20-30 seconds. After continuous pressurization and heating for 20-30 seconds, the internal structure of the battery cell under test will tend to stabilize, and the test state can be carried out.

[0028] Step 120: Continuously apply an excitation voltage to the cell under test in the test state and obtain the response current of the cell under test.

[0029] It should be noted that after the cell is immersed in electrolyte and before formation, the positive and negative electrode active materials have not yet formed a complete solid electrolyte interface (SEI) film, and no lithium insertion / deintercalation reaction has occurred. At this time, the cell can be approximately equivalent to a double-layer capacitor, and its charging process follows the characteristics of an RC circuit.

[0030] When a step DC voltage is applied to an ideal, unshort-circuited capacitor, its response current will decay exponentially. .in, For the response current coefficient, It is a time constant. The polarization resistance of the system. It is an electric double-layer capacitor. Over time... Increase, current It will rapidly decay to near zero. An example can be referenced. Figure 3 The response current curve of a normal battery cell is shown below, as follows: Figure 3 As shown, the response current of a normal battery cell approaches zero over time.

[0031] If a micro-short circuit exists inside the battery cell, it is equivalent to connecting a leakage resistor R in parallel in the RC circuit. short After a voltage is applied, the system not only charges the capacitor but also generates a continuous current through the leakage resistance. Therefore, the response current cannot decay to near zero but instead remains near a steady-state current value related to the degree of short circuit after decaying. An example can be found in [reference needed]. Figure 4 The response current curves of a battery cell with an internal short-circuit risk are shown, as follows:Figure 4 As shown, over time, the response current of the cell with internal short-circuit risk reaches a certain value (e.g., Figure 4 The voltage fluctuates around 6nA. Therefore, step 120 determines whether the cell under test has an internal short-circuit risk by applying an excitation voltage to obtain the corresponding response current.

[0032] Furthermore, the heating and pressurization in step 110 can effectively reduce the overall polarization resistance. This significantly shortens the time constant. This allows short-circuit-free cells to reach a "steady state" with near-zero current within tens of seconds, improving detection efficiency.

[0033] In some embodiments, the excitation voltage is a constant DC voltage of 5-10 μV, which can be provided by a high-precision digital-to-analog converter (DAC). Exemplarily, this high-precision DAC can be a 24-bit DAC such as the AD5791 or other suitable DAC. A controller, such as an MCU, can send a digital signal to generate a constant DC voltage of 5-10 μV. This high-precision DAC can be followed by a zero-drift operational amplifier (such as the ADA4528-1) to convert its output into a low-impedance signal, which is then applied to both ends (e.g., positive and negative terminals) of the cell under test via a Kelvin connection (e.g., a four-terminal connector to account for the voltage drop caused by the lead resistance).

[0034] In this application, a micro voltage at the μV level is used as the excitation, which can effectively stimulate the response while avoiding side reactions or damage to the cell that may be caused by excessive voltage.

[0035] In some embodiments, the application time of the excitation signal (also referred to as the second time period in this application) may be not less than 20s. For example, the second time period may be 20s, 25s, 30s, etc. Optionally or preferably, the second time period may be 20s. During the second time period, the response current may be captured by the response detection unit. Exemplarily, the response detection unit may employ a topology of a transimpedance amplifier (TIA) combined with a zero-drift differential amplifier and an analog-to-digital converter (ADC). The response current of the cell under test under the excitation voltage is input to the TIA, and the TIA outputs a detection voltage. The zero-drift differential amplifier amplifies the detection voltage to suppress common-mode noise, and the high-frequency noise is filtered out by an RC low-pass filter before outputting a filtered voltage. This filtered voltage is converted into a digital signal by the ADC and finally converted into a digital signal by a formula (e.g., ...). ,in, For ADC digital quantities, The ADC reference voltage (e.g., 2.5V, LTZ1000 reference). For TIA feedback resistor, The response current is calculated using the differential amplifier gain. The exemplary response detection unit described above can achieve a current response of 1pA to 1μA, which is compatible with the aforementioned excitation voltage range.

[0036] In this application, the current detection accuracy is sufficient to distinguish between normal capacitor decay current and continuous leakage current caused by micro-short circuit, so as to ensure the correct implementation of the detection method.

[0037] Step 130: Determine whether the cell under test has an internal short circuit risk based on the response current.

[0038] In some embodiments, the average current value of the response current of the cell under test in the last segment of the second time period can be determined and used to compare with a current threshold to determine whether the cell under test has an internal short circuit risk.

[0039] In some embodiments, the final segment interval can refer to a time interval located at the end of the second time period, not exceeding 5 seconds. Taking the second time period as 20 seconds as an example, the final segment interval can be the time interval of 15 seconds to 20 seconds. Of course, other interval widths of final segment intervals can be applied to this application, such as 4 seconds (16 seconds to 20 seconds), 3 seconds (e.g., 17 seconds to 20 seconds), 2 seconds (e.g., 18 seconds to 20 seconds), or 1 second (e.g., 19 seconds to 20 seconds), etc.

[0040] It is understood that the aforementioned acquisition of the response current is based on the sampling rate. Assuming this sampling rate is 10 kS / s (i.e., 10,000 points / second), the total number of sampling points obtained in the final 5-second interval is 50,000 (including the sampling time points and their corresponding response currents). After removing outliers, these response currents are summed and divided by the number of samples to obtain the average current (e.g., denoted as ). Other calculation methods can also be used, such as time-weighted averaging. Linear weighting is applied according to the timestamps of the sampling points, with the weights increasing over time. The average current is then calculated. The quotient between the sum of the product of the response current at each sampling point and the corresponding weight, and the sum of all weights.

[0041] In some embodiments, the average current This will be used for a magnitude comparison with the current threshold (e.g., 1 nA). If the magnitude relationship indicates the average current... When the current is not less than the said current threshold (e.g., If the cell under test is found to have an internal short circuit risk, it can be determined that the cell under test is defective, will be removed from the production line, and can be used for disassembly and analysis to determine the cause of the internal short circuit, thereby improving the process. If the magnitude relationship indicates that the average current is less than the current threshold (e.g., If the test cell is deemed to have no internal short-circuit risk, it can be determined that the test cell has no risk of internal short circuit. In this case, the test cell can proceed to the subsequent formation and capacity testing processes.

[0042] The cell testing method disclosed in this application has a testing cycle of less than 1 minute, which is more than a thousand times more efficient than the 1-2 weeks required by the traditional open-circuit voltage monitoring method (OCV monitoring method), greatly saving time and inventory costs. Furthermore, the cell testing method disclosed in this application can screen for internal short circuit risks after electrolyte injection and before formation, eliminating potentially hazardous cells in advance and reducing the safety risks of thermal runaway, fire, and explosion caused by internal short circuits during the formation process. In addition, this application uses μV-level voltage excitation, which has minimal impact on the cell's state. Judgment is made by directly observing the current decay to a steady state, which is more direct and reliable than indirect voltage drop monitoring.

[0043] This application also provides a cell testing apparatus for implementing the cell testing method. In some embodiments, the cell testing apparatus may include a state adjustment component, an excitation component, a response component, and a processing component.

[0044] Simultaneously combined Figure 2 The battery cell testing device is described by way of example.

[0045] The state adjustment component can be used to pre-process the battery cell C under test to bring it into the test state. Exemplarily, the state adjustment component may include a pressure application unit or pressurizing element (e.g., cylinder G and end-stage actuator P) and a heating unit or heating element (e.g., heating plate H1 and heating plate H2) to perform a pre-processing operation on the battery cell under test, including at least pressurizing and heating the battery cell under test and maintaining it for a first time period (e.g., 20-30 s). The pressurizing element can be used to apply pressure to the battery cell C under test (e.g., applying a pressure of 0.5-1 MPa), and the heating element can be used to heat the battery cell C under test to maintain its surface temperature within a stable range (e.g., maintaining the surface temperature of the battery cell C under test at 50-60°C). In some embodiments, the heating element may be integrated into the pressurizing element. For example, the end-stage actuator P and the machine tool B may have embedded heating units, such as resistance wires, to simultaneously pressurize and heat the battery cell under test.

[0046] The excitation component can be used to continuously apply an excitation voltage to the battery cell C under test in the test state for a second time period (e.g., 20s). The excitation component can be electrically connected to the battery cell C under test. For example, the topology of the excitation component can be a high-precision DAC combined with a zero-drift operational amplifier, connected to the battery cell C under test via a Kelvin converter. The response component can be used to acquire the response current of the battery cell C under test during the second time period. The response component can also be electrically connected to the battery cell C under test. For example, the topology of the response component can be a transimpedance amplifier (TIA) combined with a zero-drift differential amplifier and an analog-to-digital converter (ADC), with the TIA connected to the battery cell C under test to receive the response current.

[0047] In some embodiments, the excitation component and the response component may be integrated into one unit, for example... Figure 2 The detection component D is shown in the figure. For example, the detection component D can be implemented by an application-specific integrated circuit (ASIC) to achieve high-precision excitation and nanoampere-level current detection through customized integration.

[0048] The processing component can be used to determine whether the cell under test has an internal short-circuit risk based on the response current. The processing component can be communicatively connected to the response component to obtain the response current data it captures. For example, the processing component can be any computing device with computing power, such as an industrial computer (e.g., a Linux-based computer), a main control chip (e.g., ARM, DSC, DSP, etc.), a programmable logic controller (PLC), a programmable logic device (PLD), a microcontroller (MCU), etc., and can communicate with the response component through any suitable communication method such as fieldbus (e.g., PROFIBUS, MODBUS, DeviceNet, CANopen, etc.), Ethernet (e.g., EtherNet / IP, PROFINET, EtherCAT, Modbus TCP, etc.), wireless communication (e.g., Wi-Fi™, Bluetooth™, ZigBee™, LoRa™, etc.), serial communication (e.g., RS-232, RS-485, etc.), parallel communication, fiber optic communication, OPC (OLE for Process Control), Internet of Things (IIoT) protocols (e.g., MQTT, AMQP, CoAP, etc.), Time-Sensitive Networking (TSN), 5G network, etc. Figure 2 The processing component U is shown in the figure. In some embodiments, the processing component U and the detection component D can also be integrated into one unit. For example, the processing component U is implemented by a microcontroller (MCU) or can be integrated into an ASIC.

[0049] In some embodiments, the processing component can obtain the average current of the response current of the cell under test C during the last segment of the second time period (e.g., a 5-second time interval, such as 15-20 seconds), and determine whether the cell under test C has an internal short-circuit risk based on the relationship between the average current and a current threshold. The average current can be an arithmetic average or a time-weighted average. When the relationship indicates that the average current is not less than the current threshold, the processing component can determine that the cell under test has an internal short-circuit risk. When the relationship indicates that the average current is less than the current threshold, the processing component can determine that the cell under test has no internal short-circuit risk.

[0050] The above process is illustrated below with specific implementation details. It should be noted that the following content is for illustrative purposes only and is not intended to limit the scope of this application.

[0051] This example demonstrates a rapid screening method for internal short-circuit risks in lithium iron phosphate battery cells: (1) Place the LFP cell, which has been injected with electrolyte and soaked for 48 hours, into the testing device (e.g., Figure 2 The detection device shown.

[0052] (2) Start the heating element to stabilize the surface temperature of the battery cell at 55°C; at the same time, start the cylinder to apply a constant pressure of 0.6 MPa to the battery cell and maintain this state for 20 seconds.

[0053] (3) Apply a constant DC voltage of 10μV to both ends of the cell for 20 seconds using a high-precision digital-to-analog converter, record the current data from the 0th second to the 20th second, and calculate the average value of the current data within the 5-second time window from the 15th second to the 20th second. .

[0054] (4) If the cell is a normal cell, its current response curve can be similar to that of a normal cell. Figure 3 As shown, it becomes less than 1 μA after 10 seconds. After calculation... If the current threshold is less than 1nA, the cell can be considered qualified and will proceed to the formation process.

[0055] (5) If the cell has the risk of internal short circuit, its current response can be similar to Figure 4 Since the response current of the battery cell is always greater than 1μA, then The current threshold must be greater than 1nA. At this point, the cell can be deemed unqualified and is considered a cell with an internal short circuit risk.

[0056] refer to Figure 5 The exemplary teardown diagram shown, targeting a battery cell with an internal short-circuit risk, reveals the presence of particulate foreign matter (such as...) inside. Figure 5(As shown by the black circle in the image). This foreign object is the cause of the internal short circuit in the battery cell. To address this, the control of raw materials, production equipment, and the production environment in the preceding processes can be improved.

[0057] It should be noted that the above-mentioned Figure 1 The descriptions of the various steps in this specification are for illustrative purposes only and do not limit the scope of this specification. Those skilled in the art can, under the guidance of this specification, [perform certain tasks / activities]. Figure 1 Various modifications and changes have been made to the steps described herein. However, these modifications and changes remain within the scope of this specification.

[0058] This application has described the basic concepts. Obviously, for those skilled in the art, the above detailed disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this application.

[0059] Furthermore, this application uses specific terms to describe its embodiments. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this application do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

[0060] Similarly, it should be noted that, in order to simplify the description of this application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of this application sometimes combines multiple features into one embodiment or its description. However, this disclosure method does not imply that the subject matter of this application requires more features than those mentioned in the claims. In fact, the embodiments have fewer features than all the features of the single embodiments disclosed above.

[0061] Finally, it should be understood that the embodiments described in this application are merely illustrative of the principles of the embodiments of this application. Other modifications may also fall within the scope of this application. Therefore, alternative configurations of the embodiments of this application are considered as examples and not limitations, and are regarded as consistent with the teachings of this application. Accordingly, the embodiments of this application are not limited to the embodiments explicitly described and illustrated in this application.

Claims

1. A method for testing battery cells, wherein the method is used to determine whether a battery cell under test has an internal short circuit risk after being injected with electrolyte; characterized in that, The detection method includes: The cell under test is pre-processed to bring it into a test state; the pre-processing includes at least pressurizing and heating the cell under test and maintaining it for a first time period. A second time period is used to continuously apply an excitation voltage to the cell under test in the test state, and the response current of the cell under test during the second time period is obtained. The presence of an internal short circuit risk in the cell under test is determined based on the response current.

2. The cell testing method according to claim 1, characterized in that, The preprocessing satisfies at least one of the following characteristics: (1) The pressure applied is 0.5-1 MPa; (2) The heating maintains the surface temperature of the battery cell under test at 50-60°C; (3) The first time period is 20-30s.

3. The cell testing method according to claim 1, characterized in that, The excitation voltage is a constant DC voltage of 5-10μV; the second time period is not less than 20s.

4. The cell testing method according to claim 1, characterized in that, The second time period is 20 seconds; The step of determining whether the cell under test has an internal short-circuit risk based on the response current includes: The average current value of the response current of the cell under test in the last segment of the second time period is obtained; the last segment does not exceed 5 seconds. Based on the relationship between the average current and the current threshold, it is determined whether the cell under test has a risk of internal short circuit.

5. The cell testing method according to claim 4, characterized in that, When the magnitude relationship indicates that the average current is not less than the current threshold, it is determined that the cell under test has an internal short circuit risk; When the magnitude relationship indicates that the average current is less than the current threshold, it is determined that the cell under test has no risk of internal short circuit.

6. A battery cell testing device, wherein the battery cell testing device is used to determine whether a battery cell under test has an internal short circuit risk after being injected with electrolyte; characterized in that, The battery cell testing device includes: A state adjustment component is configured to preprocess the cell under test to bring it into a test state; the preprocessing includes at least pressurizing and heating the cell under test and maintaining it for a first time period. The excitation component is configured to continuously apply an excitation voltage to the cell under test in the test state for a second time period. A response component is configured to acquire the response current of the cell under test during the second time period; and The processing component is configured to determine whether the cell under test has an internal short-circuit risk based on the response current.

7. The cell testing device according to claim 6, characterized in that, The state adjustment assembly includes a pressure application unit and a heating unit; the pressure application unit is configured to apply a pressure of 0.5-1 MPa to the cell under test, and the heating unit is configured to accelerate the cell under test to maintain its surface temperature at 50-60°C.

8. The cell testing device according to claim 6, characterized in that, The excitation component and the response component are electrically connected to the cell under test, respectively, to continuously apply an excitation voltage to the cell under test in the test state and to obtain the response current of the cell under test.

9. The cell testing device according to claim 6, characterized in that, To determine whether the cell under test has a risk of internal short circuit, the processing component is configured to: The average current value of the response current of the cell under test in the last segment of the second time period is obtained; the last segment does not exceed 5 seconds. Based on the relationship between the average current and the current threshold, it is determined whether the cell under test has a risk of internal short circuit.

10. The cell testing device according to claim 9, characterized in that, The processing component is configured as follows: When the magnitude relationship indicates that the average current is not less than the current threshold, it is determined that the cell under test has an internal short circuit risk; When the magnitude relationship indicates that the average current is less than the current threshold, it is determined that the cell under test has no risk of internal short circuit.

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