A method, device, and electronic device for detecting the state of an electric cell

Abstract

The present application provides a method, a device, and an electronic device for detecting the state of an electric cell. The method includes: after performing a self-discharge operation on a target electric cell under a first operating condition, obtaining a first K value of the target electric cell under the first operating condition; after performing a cyclic charge and discharge on the target electric cell, charging the target electric cell to a target power; after performing a self-discharge operation on the target electric cell charged to the target power under a second operating condition, obtaining a second K value of the target electric cell under the second operating condition; and determining a first electric cell state of the target electric cell according to the first K value and the second K value. Embodiments of the present application are used to solve the problem of inaccurate battery state detection.

Description

Technical Field

[0001] The present application relates to a method and device for detecting the state of an electric cell, and an electronic device. Background Art

[0002] Lithium-ion batteries have been widely used in new energy vehicles due to their high energy density, long service life, and no memory effect. However, with the continuous improvement of the energy density of lithium batteries and the increasing market retention, safety issues have become the biggest bottleneck in their development.

[0003] There are mainly two reasons for the thermal runaway of lithium-ion batteries. One is the process problems caused by defects and poor consistency during the battery manufacturing process; the other is the abuse problems caused by harsh working conditions and bad usage habits. Abnormal self-discharge is an important defect that causes battery runaway caused by manufacturing process problems. It has a long detection period, unpredictable development degree, and great harm. The electric cells with abnormal self-discharge will bring huge safety hazards to the battery system after being formed into modules.

[0004] In the related art, battery manufacturers screen and grade batteries by testing the K value (voltage drop per unit time of a lithium-ion battery) of the battery through the method of pre-storage before factory testing. This method can screen out fresh electric cells with obvious abnormal self-discharge, but it cannot screen some electric cells with self-discharge defects whose current K values are within the specifications, which has great limitations. The self-discharge degree of these defective electric cells will deteriorate significantly with the increase of the state of health (SOH), and the growth rate of the K value is significantly higher than that of normal electric cells. Therefore, they will bring huge safety hazards to the battery system after being formed into modules. Summary of the Invention

[0005] The technical object to be achieved by the embodiments of the present application is to provide a method and device for detecting the state of an electric cell, and an electronic device, so as to solve the problem of inaccurate detection of the battery state.

[0006] To solve the above technical problems, the embodiments of the present application provide a method for detecting the state of an electric cell, including:

[0007] After performing a self-discharge operation on a target electric cell under a first working condition, obtaining a first K value of the target electric cell under the first working condition;

[0008] After performing a cyclic charge and discharge on the target electric cell, charging the target electric cell to a target power;

[0009] After performing a self-discharge operation on the target electric cell charged to the target power under a second working condition, obtaining a second K value of the target electric cell under the second working condition;

[0010] Determining a first state of the target electric cell according to the first K value and the second K value.

[0011] Optionally, after obtaining the second K value of the target battery cell under the second working condition, the method further includes:

[0012] After performing a self-discharge operation on the target battery cell under the third working condition, obtain the third K value of the target battery cell under the third working condition, where the temperature of the target battery cell under the third working condition is higher than the temperatures under the first working condition and the second working condition;

[0013] Determine the second battery cell state of the target battery cell according to the first K value, the second K value, and the third K value.

[0014] Optionally, after performing a self-discharge operation on the target battery cell under the first working condition, obtaining the first K value of the target battery cell under the first working condition includes:

[0015] Charge the target battery cell with constant current and constant voltage to the target power;

[0016] After storing the target battery cell for the first duration under the first temperature condition, obtain the first open-circuit voltage of the target battery cell;

[0017] After continuing to store the target battery cell for the second duration under the second temperature condition, obtain the second open-circuit voltage of the target battery cell;

[0018] Determine the first K value according to the first open-circuit voltage and the second open-circuit voltage.

[0019] Optionally, after performing cyclic charge and discharge on the target battery cell, charging the target battery cell to the target power includes:

[0020] Perform cyclic constant-current and constant-voltage charge and discharge on the target battery cell under the third temperature condition;

[0021] After performing charge and discharge on the target battery cell for a preset number of times, charge the target battery cell with constant current and constant voltage to the target power.

[0022] Optionally, after performing a self-discharge operation on the target battery cell under the second working condition, obtaining the second K value of the target battery cell under the second working condition includes:

[0023] After storing the target battery cell for the third duration under the fourth temperature condition, obtain the third open-circuit voltage of the target battery cell;

[0024] After storing the target battery cell for the fourth duration under the fifth temperature condition, obtain the fourth open-circuit voltage of the target battery cell;

[0025] Determine the second K value according to the third open-circuit voltage and the fourth open-circuit voltage.

[0026] Optionally, after performing a self-discharge operation on the target battery cell under the third operating condition, obtaining a third K value of the target battery cell under the third operating condition includes:

[0027] After storing the target battery cell for a fifth duration under the sixth temperature condition, obtaining a fifth open-circuit voltage of the target battery cell, where the temperature of the target battery cell under the sixth temperature condition is greater than the temperature of the target battery cell under the fifth temperature condition;

[0028] Determining the third K value according to the fourth open-circuit voltage and the fifth open-circuit voltage.

[0029] Optionally, determining a first battery cell state of the target battery cell according to the first K value and the second K value includes at least one of the following:

[0030] When the first K value and / or the second K value is outside a preset K value range, determining that the target battery cell is in an abnormal battery cell state, where the preset K value range is associated with the target battery cell;

[0031] When the absolute value of the difference between the first K value and the second K value is greater than a first preset value, determining that the target battery cell is in an abnormal battery cell state.

[0032] Optionally, determining a second battery cell state of the target battery cell according to the first K value, the second K value, and the third K value includes at least one of the following:

[0033] When the first K value, the second K value, and / or the third K value is outside a preset K value range, determining that the target battery cell is in an abnormal battery cell state;

[0034] When the absolute value of the difference between the first K value and the second K value is greater than a first preset value, determining that the target battery cell is in an abnormal battery cell state;

[0035] When the absolute value of the difference between the second K value and the third K value is greater than a second preset value, determining that the target battery cell is in an abnormal battery cell state.

[0036] An embodiment of the present application further provides a state detection device for a battery cell, including:

[0037] A first acquisition module, configured to obtain a first K value of the target battery cell under the first operating condition after performing a self-discharge operation on the target battery cell under the first operating condition;

[0038] A first control module, configured to charge the target battery cell to a target power after performing a cyclic charge and discharge on the target battery cell;

[0039] A second acquisition module, configured to obtain a second K value of the target battery cell under the second operating condition after performing a self-discharge operation on the target battery cell charged to the target power under the second operating condition;

[0040] A first determination module, configured to determine a first cell state of a target cell according to a first K value and a second K value.

[0041] Optionally, the apparatus further includes:

[0042] A third acquisition module, configured to, after performing a self-discharge operation on the target cell under a third operating condition, acquire a third K value of the target cell under the third operating condition, where the temperature at which the target cell is located under the third operating condition is higher than the temperature at which the target cell is located under the first operating condition and the second operating condition;

[0043] A second determination module, configured to determine a second cell state of the target cell according to the first K value, the second K value, and the third K value.

[0044] Optionally, the first acquisition module is specifically configured to: charge the target cell with constant current and constant voltage to a target power; after storing the target cell for a first duration under a first temperature condition, acquire a first open-circuit voltage of the target cell; after continuing to store the target cell for a second duration under a second temperature condition, acquire a second open-circuit voltage of the target cell; and determine the first K value according to the first open-circuit voltage and the second open-circuit voltage.

[0045] Optionally, the first control module is specifically configured to: perform cyclic constant-current and constant-voltage charge and discharge on the target cell under a third temperature condition; after performing a preset number of charge and discharge operations on the target cell, charge the target cell with constant current and constant voltage to the target power.

[0046] Optionally, the second acquisition module is specifically configured to: after storing the target cell for a third duration under a fourth temperature condition, acquire a third open-circuit voltage of the target cell; after storing the target cell for a fourth duration under a fifth temperature condition, acquire a fourth open-circuit voltage of the target cell; and determine the second K value according to the third open-circuit voltage and the fourth open-circuit voltage.

[0047] Optionally, the third acquisition module is specifically configured to: after storing the target cell for a fifth duration under a sixth temperature condition, acquire a fifth open-circuit voltage of the target cell, where the temperature at which the target cell is located under the sixth temperature condition is greater than the temperature at which the target cell is located under the fifth temperature condition; and determine the third K value according to the fourth open-circuit voltage and the fifth open-circuit voltage.

[0048] Optionally, the first determination module is specifically configured to: in a case where the first K value and / or the second K value is outside a preset K value range, determine that the target cell is in a cell abnormal state, where the preset K value range is associated with the target cell; and / or, in a case where the absolute value of the difference between the first K value and the second K value is greater than a first preset value, determine that the target cell is in a cell abnormal state.

[0049] Optionally, the second determination module is specifically configured to: determine that the target battery cell is in an abnormal state when the first K value, the second K value, and / or the third K value are outside the preset K value range; determine that the target battery cell is in an abnormal state when the absolute value of the difference between the first K value and the second K value is greater than the first preset value; and / or, determine that the target battery cell is in an abnormal state when the absolute value of the difference between the second K value and the third K value is greater than the second preset value.

[0050] An embodiment of the present application also provides an electronic device, including a processor and a memory. The memory stores machine-executable instructions that can be executed by the processor, and the processor executes the machine-executable instructions to implement the method for detecting the state of the battery cell as described above.

[0051] Compared with the prior art, a method, device, and electronic device for detecting the state of a battery cell provided by an embodiment of the present application have at least the following beneficial effects:

[0052] In the method of the embodiment of the present application, under the first working condition, after self-discharging the target battery cell, the first K value of the target battery cell under the first working condition is obtained. After the target battery cell is subjected to cyclic charge and discharge and charged to the target power, the target battery cell is self-discharged again under the second working condition, and the second K value of the target battery cell under the second working condition is obtained. The state of the target battery cell is determined according to the first K value and the second K value. In the embodiment of the application, by testing the K value under multiple conditions and comparing the change values of the K value under different working conditions, the self-discharge type of the battery and the degree of influence on safety can be judged, so that the state of the battery cell can be determined more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a schematic flow chart of the method for detecting the state of the battery cell according to the embodiment of the present application;

[0054] Figure 2 is a graph showing the relationship between the storage time and the open-circuit voltage of the battery cell according to the embodiment of the present application;

[0055] Figure 3 is a schematic structural diagram of the device for detecting the state of the battery cell according to the embodiment of the present application. DETAILED DESCRIPTION

[0056] To make the technical problems, technical solutions, and advantages to be solved by this application clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments. In the following description, providing specific details such as specific configurations and components is only to help comprehensively understand the embodiments of this application. Therefore, those skilled in the art should clearly understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. Additionally, descriptions of known functions and structures are omitted for clarity and conciseness.

[0057] It should be understood that the "one embodiment" or "an embodiment" mentioned throughout the specification means that the specific features, structures, or characteristics related to the embodiment are included in at least one embodiment of this application. Therefore, the "in one embodiment" or "in an embodiment" that appears throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures, or characteristics can be combined in one or more embodiments in any suitable manner.

[0058] In various embodiments of this application, it should be understood that the magnitudes of the serial numbers of the following processes do not mean the order of execution is prior or subsequent. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0059] It should be understood that the term "and / or" in this article is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the front and rear associated objects.

[0060] In the embodiments provided by this application, it should be understood that "B corresponding to A" means that B is associated with A, and B can be determined according to A. However, it should also be understood that determining B according to A does not mean determining B only according to A, and B can also be determined according to A and / or other information.

[0061] See Figure 1 , the embodiments of this application provide a method for detecting the state of an electric cell, including:

[0062] S101, after performing self-discharge operation on the target electric cell under the first operating condition, obtain the first K value of the target electric cell under the first operating condition;

[0063] S102, after performing cyclic charge and discharge on the target electric cell, charge the target electric cell to the target power;

[0064] S103, after performing self-discharge operation on the target electric cell charged to the target power under the second operating condition, obtain the second K value of the target electric cell under the second operating condition;

[0065] S104. Determine the first battery cell state of the target battery cell according to the first K value and the second K value.

[0066] In the embodiments of the present application, the first operating condition and the second operating condition may be to simulate the operating conditions of the battery cell, and the first operating condition and the second operating condition may be the same. In one embodiment, the first operating condition may be to store the battery cell at 35-55°C for 12-72 hours, and the second operating condition may be to leave the battery cell at 35-55°C for 3-5 days.

[0067] In the method of the embodiments of the present application, under the first operating condition, after performing a self-discharge operation on the target battery cell, the first K value of the target battery cell under the first operating condition is obtained. After the target battery cell is subjected to cyclic charge and discharge and charged to the target power, after performing a self-discharge operation on the target battery cell again under the second operating condition, the second K value of the target battery cell under the second operating condition is obtained, and the battery cell state of the target battery cell is determined according to the first K value and the second K value. In the embodiments of the application, by testing the K value under multiple conditions and comparing the change values of the K value under different operating conditions, the self-discharge type of the battery and the degree of influence on safety can be judged, so that the state of the battery cell can be determined more accurately.

[0068] Optionally, after obtaining the second K value of the target battery cell under the second operating condition, the method further includes:

[0069] After performing a self-discharge operation on the target battery cell under the third operating condition, the third K value of the target battery cell under the third operating condition is obtained, where the temperature of the target battery cell under the third operating condition is higher than the temperature under the first operating condition and the second operating condition;

[0070] Determine the second battery cell state of the target battery cell according to the first K value, the second K value and the third K value.

[0071] In the embodiments of the present application, the third operating condition may be to simulate the operating conditions of the battery cell. In the embodiments of the present application, the temperature of the target battery cell under the third operating condition is higher than the temperature under the first operating condition and the second operating condition. By simulating the target battery cell in different high-temperature environments and obtaining the third K value, the state of the battery cell under different environmental changes can be determined by combining the first K value, the second K value and the third K value, making the detection of the battery cell state more accurate.

[0072] Optionally, after performing a self-discharge operation on the target battery cell under the first operating condition, obtaining the first K value of the target battery cell under the first operating condition includes:

[0073] Charge the target battery cell with constant current and constant voltage to the target power;

[0074] After storing the target battery cell for a first duration under a first temperature condition, obtain the first open-circuit voltage of the target battery cell;

[0075] After continuing to store the target battery cell for a second duration under a second temperature condition, obtain the second open-circuit voltage of the target battery cell;

[0076] Determine a first K value according to the first open-circuit voltage and the second open-circuit voltage.

[0077] In the embodiments of the present application, the target battery level can be 100% battery level. In the embodiments of the present application, the battery cell can be charged at a constant current and constant voltage of 0.33C - 2C to 100%. The first temperature condition can be a temperature condition of 35 - 55°C. The first duration can be 12 - 72 hours. The second temperature condition can be a temperature condition of 35 - 55°C. The second duration can be 3 - 5 days. In one embodiment, the temperature under the first temperature condition can be 45°C, and the temperature under the second temperature condition can also be 45°C.

[0078] Optionally, after performing cyclic charge and discharge on the target battery cell, charging the target battery cell to the target battery level includes:

[0079] Performing cyclic constant current and constant voltage charge and discharge on the target battery cell under a third temperature condition;

[0080] After performing a preset number of charge and discharge operations on the target battery cell, charging the target battery cell at a constant current and constant voltage to the target battery level.

[0081] In the embodiments of the present application, the third temperature condition can be a temperature condition of 35 - 55°C. The target battery cell can be cycled for constant current and constant voltage charging at 0.5C - 2C and constant current discharging at 0.5C - 2C.

[0082] Optionally, after performing a self-discharge operation on the target battery cell under a second working condition, obtaining a second K value of the target battery cell under the second working condition includes:

[0083] After storing the target battery cell for a third duration under a fourth temperature condition, obtain the third open-circuit voltage of the target battery cell;

[0084] After storing the target battery cell for a fourth duration under a fifth temperature condition, obtain the fourth open-circuit voltage of the target battery cell;

[0085] Determine a second K value according to the third open-circuit voltage and the fourth open-circuit voltage.

[0086] In the embodiments of the present application, the fourth temperature condition can be a temperature condition of 35 - 55°C. The third duration can be 12 - 72 hours. The fifth temperature condition can be a temperature condition of 35 - 55°C. The fourth duration can be 3 - 5 days.

[0087] Optionally, after performing self-discharge operation on the target battery cell under the third working condition, obtaining the third K value of the target battery cell under the third working condition includes:

[0088] After storing the target battery cell for a fifth duration under the sixth temperature condition, obtaining the fifth open-circuit voltage of the target battery cell, where the temperature of the target battery cell under the sixth temperature condition is greater than the temperature of the target battery cell under the fifth temperature condition;

[0089] Determining the third K value according to the fourth open-circuit voltage and the fifth open-circuit voltage.

[0090] In the embodiments of the present application, the sixth temperature condition may be a temperature condition of 40-60 °C. The fifth duration may be 2-4 days.

[0091] Optionally, determining the first battery cell state of the target battery cell according to the first K value and the second K value includes at least one of the following:

[0092] In the case where the first K value or the second K value is outside the preset K value range, it is determined that the target battery cell is in an abnormal battery cell state, where the preset K value range is associated with the target battery cell;

[0093] In the case where the absolute value of the difference between the first K value and the second K value is greater than the first preset value, it is determined that the target battery cell is in an abnormal battery cell state.

[0094] In one implementation manner, in the case where the absolute value of the difference between the first K value and the second K value is greater than the first preset value, determining that the target battery cell is in an abnormal battery cell state may include:

[0095] In the case where the first K value is greater than the second K value and the difference between the first K value and the second K value is greater than the first threshold, it is determined that the target battery cell is in a state of foreign object micro short circuit;

[0096] In the case where the first K value is less than the second K value and the difference between the second K value and the first K value is greater than the second threshold, it is determined that the target battery cell is in a state of foreign object micro short circuit and the battery cell diaphragm is damaged.

[0097] In the related art, each type of battery cell has its factory self-discharge K value specification, and this specification value generally should not be greater than 0.12% / day. In the case where both the first K value and the second K value are qualified, it can be determined that the target battery cell is in the first qualified state. It can also be determined that the target battery cell is in the first qualified state in the case where both the first K value and the second K value are qualified and the absolute value of the difference between the two is less than or equal to the first preset value. Whether the K value is qualified can be determined according to the factory self-discharge K value specification of the battery cell. In the case where both the first K value and the second K value are abnormal, it can be determined that the target battery cell is in a state of foreign object micro short circuit and the battery cell diaphragm is damaged.

[0098] Optionally, according to the first K value, the second K value, and the third K value, determine the second cell state of the target cell, including at least one of the following:

[0099] When the first K value, the second K value, and / or the third K value are outside the preset K value range, determine that the target cell is in an abnormal cell state;

[0100] When the absolute value of the difference between the first K value and the second K value is greater than the first preset value, determine that the target cell is in an abnormal cell state;

[0101] When the absolute value of the difference between the second K value and the third K value is greater than the second preset value, determine that the target cell is in an abnormal cell state.

[0102] When the absolute value of the difference between the second K value and the third K value is greater than the second preset value, determine that the target cell is in an abnormal cell state.

[0103] In the embodiments of the present application, on the basis of determining the cell state of the target cell according to the first K value and the second K value, the judgment of the third K value can be added. Specifically, it includes judging whether the third K value is within the preset K value range, and judging the relationship between the absolute value of the difference between the second K value and the third K value and the second preset value;

[0104] Among them, when the third K value is outside the preset K value range and / or the absolute value of the difference between the second K value and the third K value is greater than the second preset value, it is determined that the target cell is in an abnormal cell state. Specifically, when the absolute value of the difference between the second K value and the third K value is greater than the second preset value, it can be specifically determined whether the target cell is in a state where the chemical self-discharge is higher than the third threshold.

[0105] In the embodiments of the present application, when the first K value, the second K value, and the third K value are all qualified, it can be determined that the target cell is in the second qualified state. It can also be determined that the target cell is in the second qualified state when the first K value, the second K value, and the third K value are all qualified, and the absolute value of the difference between the first K value and the second K value is less than or equal to the first preset value, and the absolute value of the difference between the second K value and the third K value is less than or equal to the second preset value. When the second K value and the third K value are abnormal, it can be determined that the target cell is a cell in an abnormal chemical self-discharge state.

[0106] By detecting and comparing the K value under different working conditions, the judgment of the cell state can be made more accurate.

[0107] In the embodiments of the present application, when the first K value, the second K value, and the third K value are all abnormal, it can be determined that the target cell is in a severely abnormal state.

[0108] The following is an example of the method according to the embodiments of the present application. In Figure 2 the following, an example is given to illustrate the method of the embodiments of the present application. In Figure 2 the schematic diagram shown, the horizontal axis is time, with the unit of days, and the vertical axis is the open circuit voltage, with the unit of milliamperes. This figure records the open circuit voltage values of the battery cell at different time points.

[0109] The self-discharge safety screening test is carried out on fresh batteries according to the following process to test the change of the K value of the battery cell under different working conditions, so as to determine the state of the battery cell. The detailed process steps are as follows:

[0110] S1, High-temperature storage and shelving: Charge the fresh battery cell at a constant current and constant voltage of 0.33C - 2C (preferably 1C) to 100% SOC, store it for 12 - 72 hours (preferably 36 hours) at 35 - 55°C (preferably 45°C) (the end time point is T1), and test the open circuit voltage (Open Circuit Voltage, abbreviated as OCV) V1 of the battery after storage.

[0111] S2, High-temperature storage and shelving: After shelving for 3 - 5 days (preferably 4 days) at 35 - 55°C (preferably 45°C) (the end time point is T2), record the OCV value V2. Through the SOC-OCV curve of this battery cell, obtain the corresponding SOC1 and SOC2, calculate the daily self-discharge K value, and obtain K1. The K value is calculated using the following formula:

[0112] K = (SOC t1 - SOC t2 ) / (T t2 - T t1 ), where SOC t1 represents the state of charge (State of charge, abbreviated as SOC) of the battery cell at time t1, SOC t2 represents the state of charge of the battery cell at time t2, T t2 represents the moment t2, and T t1 represents the moment t1. It can be understood that the formula can be used to calculate K1, K2, and K3.

[0113] S3, High-temperature cycling: Perform constant current and constant voltage charging at 0.5C - 2C (preferably 1C) and constant current discharging at 0.5C - 2C (preferably 1C) on the test battery cell for 2 - 20 cycles (preferably 10 cycles) at 35 - 55°C (preferably 45°C). After the last cycle ends, charge the battery cell at a constant current and constant voltage of 0.5C - 2C (preferably 1C) to 100% SOC, and record the time point T3;

[0114] S4, High-temperature storage and standby: Continue to store at 35 - 55°C (preferably 45°C) for 12 - 72 hours (preferably 48 hours) (time point is T4). After the storage ends, test the open-circuit voltage (OCV) V3 of the battery and obtain SOC3;

[0115] S5, High-temperature storage and standby: Under the condition of 35 - 55°C (preferably 45°C), standby for 3 - 5 days (preferably 4 days) (time point is T5). At the end, test the open-circuit voltage (OCV) V4 and obtain SOC4; Calculate the K value to obtain K2.

[0116] S6, High-temperature storage and standby: Under the condition of 40 - 60°C (preferably 50°C), standby for 2 - 4 days (preferably 3 days) (time point is T6). At the end, test the open-circuit voltage (OCV) V5 and SOC5; Calculate the K value to obtain K3.

[0117] Classify the cell state of the battery cell according to the above three self-discharge values of K1, K2, and K3.

[0118] Each type of battery cell has its own self-discharge K value specification at the time of factory, and this specification value should generally not be greater than 0.12% / day. According to whether the three K values tested according to the present invention meet the self-discharge K specification, the battery cells can be divided into the following four cell states, and only the first type is a safe and qualified battery cell.

[0119] 1) Normal battery cells with qualified K1, K2, and K3;

[0120] 2) Physical self-discharge battery cells with abnormal K1 and K2;

[0121] 3) Chemical self-discharge battery cells with abnormal K2 and K3;

[0122] 4) Seriously unqualified battery cells with abnormal K1, K2, and K3.

[0123] In the embodiment of the present application, K1 and K2 are used to judge whether there is an obvious physical self-discharge type in the battery. If the values of K1 and K2 are inconsistent, the battery has a risk of internal short circuit due to metal foreign objects: If K2 is significantly smaller than K1, it indicates that there is a micro short circuit of foreign objects in the battery and melting occurs during the large-current cycle. Although the self-discharge K value is qualified, there is still a micro short circuit of foreign objects inside, with a potential risk of out-of-control; If K2 is significantly larger than K1, it indicates that there is a micro short circuit of foreign objects in the battery and melting occurs during the large-current cycle, and it causes greater damage to the separator, increasing the degree of self-discharge, and the battery also has a risk of out-of-control;

[0124] K2 and K3 are used to determine whether there is an obvious type of chemical self-discharge in the battery. Since the storage temperature in step S6 is higher, it will cause an increase in the chemical activity of each component in the battery, resulting in an increase in chemical self-discharge. By comparing K2 and K3, the battery cells with high chemical self-discharge can be further screened out. The values of K2 and K3 must also meet the battery shipping standards.

[0125] Taking the 28Ah square battery cell of the ternary lithium battery NCM532 system as an example:

[0126] First, charge a fresh battery cell at a constant current of 28A with constant current and constant voltage (CC-CV, cutoff at 1.4A) to 100% SOC, store it at 45°C for 24 hours. After the storage ends, test the open-circuit voltage of the battery to be 4.1555V, and the corresponding SOC is 99.967%;

[0127] Then perform high-temperature storage and shelving: Under the condition of 45°C, after shelving for 3 days, the OCV is 4.1530V, and the corresponding SOC is 99.781%. Calculate the self-discharge K value per hour according to the formula as K1 = 0.062% / d;

[0128] Next, perform 3 constant current charge and discharge cycles on the test battery cell at a current of 42A under the condition of 40°C. After the last cycle ends, charge the battery cell at a constant current of 28A with constant current and constant voltage (CC-CV, cutoff at 1.4A) to 100% SOC, and again under the condition of 45°C, shelve it for 12 hours. After 12 hours, record the OCV as 4.1558V, corresponding to an SOC of 99.968%. Continue to store it at 45°C for 3 days. After the end, test the open-circuit voltage of the battery to be 4.1538V, and the corresponding SOC is 99.788%. Calculate the K value using the formula as K2 = 0.060% / d.

[0129] Continue to shelve it at 45°C for 3 days. When it ends, test the open-circuit voltage to be 4.1514V, corresponding to an SOC of 99.593%; calculate the K value to obtain K3 = 0.065% / d.

[0130] The current K value standard for this type of battery cell is 0.10% / d. All three K values in the test meet the specification requirements, so it is a safe battery cell.

[0131] See Figure 3 , the embodiment of the present application also provides a state detection device for a battery cell, including:

[0132] The first acquisition module 301 is used to acquire the first K value of the target battery cell under the first working condition after performing a self-discharge operation on the target battery cell under the first working condition;

[0133] The first control module 302 is configured to charge the target battery cell to a target power level after performing cyclic charge and discharge on the target battery cell.

[0134] The second acquisition module 303 is configured to, after performing a self-discharge operation on the target battery cell charged to the target power level under second working conditions, acquire a second K value of the target battery cell under the second working conditions.

[0135] The first determination module 304 is configured to determine a first battery cell state of the target battery cell according to the first K value and the second K value.

[0136] Optionally, the apparatus further includes:

[0137] The third acquisition module is configured to, after performing a self-discharge operation on the target battery cell under third working conditions, acquire a third K value of the target battery cell under the third working conditions, where the temperature at which the target battery cell is located under the third working conditions is higher than the temperatures at which the target battery cell is located under the first working conditions and the second working conditions.

[0138] The second determination module is configured to determine a second battery cell state of the target battery cell according to the first K value, the second K value, and the third K value.

[0139] Optionally, the first acquisition module is specifically configured to: charge the target battery cell with constant current and constant voltage to the target power level; after storing the target battery cell for a first duration under a first temperature condition, acquire a first open-circuit voltage of the target battery cell; after continuing to store the target battery cell for a second duration under a second temperature condition, acquire a second open-circuit voltage of the target battery cell; and determine the first K value according to the first open-circuit voltage and the second open-circuit voltage.

[0140] Optionally, the first control module is specifically configured to: perform cyclic constant-current and constant-voltage charge and discharge on the target battery cell under a third temperature condition; after performing a preset number of charge and discharge operations on the target battery cell, charge the target battery cell with constant current and constant voltage to the target power level.

[0141] Optionally, the second acquisition module is specifically configured to: after storing the target battery cell for a third duration under a fourth temperature condition, acquire a third open-circuit voltage of the target battery cell; after storing the target battery cell for a fourth duration under a fifth temperature condition, acquire a fourth open-circuit voltage of the target battery cell; and determine the second K value according to the third open-circuit voltage and the fourth open-circuit voltage.

[0142] Optionally, the third acquisition module is specifically configured to: after storing the target battery cell for a fifth duration under a sixth temperature condition, acquire a fifth open-circuit voltage of the target battery cell, where the temperature at which the target battery cell is located under the sixth temperature condition is greater than the temperature at which the target battery cell is located under the fifth temperature condition; and determine the third K value according to the fourth open-circuit voltage and the fifth open-circuit voltage.

[0143] Optionally, the first determination module is specifically configured to: when the first K value and / or the second K value is outside a preset K value range associated with the target battery cell, determine that the target battery cell is in an abnormal state; and / or, when the absolute value of the difference between the first K value and the second K value is greater than a first preset value, determine that the target battery cell is in an abnormal state.

[0144] Optionally, the second determination module is specifically configured to: when the first K value, the second K value, and / or the third K value is outside a preset K value range, determine that the target battery cell is in an abnormal state; when the absolute value of the difference between the first K value and the second K value is greater than a first preset value, determine that the target battery cell is in an abnormal state; and / or, when the absolute value of the difference between the second K value and the third K value is greater than a second preset value, determine that the target battery cell is in an abnormal state.

[0145] The apparatus embodiment of the present application is an apparatus corresponding to the method embodiment above. All the implementation means in the above method embodiment are applicable to the apparatus embodiment, and the same technical effects can be achieved.

[0146] The embodiment of the present application further provides an electronic device, including a processor and a memory. The memory stores machine-executable instructions that can be executed by the processor, and the processor executes the machine-executable instructions to implement the method for detecting the state of the battery cell as described above.

[0147] In addition, the present application may repeat reference numerals and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0148] It should also be noted that in this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover a non-exclusive inclusion.

[0149] The above is the preferred embodiment of the present application. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present application.

Claims

1. A method for detecting the state of an electric cell, characterized in that, Including: After performing a self-discharge operation on the target battery cell under the first operating condition, obtaining a first K value of the target battery cell under the first operating condition; After performing cyclic charge and discharge on the target battery cell, charging the target battery cell to a target power level; After performing a self-discharge operation on the target battery cell charged to the target power level under the second operating condition, obtaining a second K value of the target battery cell under the second operating condition; Determining a first battery cell state of the target battery cell according to the first K value and the second K value; Wherein, after performing a self-discharge operation on the target battery cell under the first operating condition, obtaining the first K value of the target battery cell under the first operating condition includes: Charging the target battery cell with constant current and constant voltage to the target power level; After storing the target battery cell for a first duration under a first temperature condition, obtaining a first open-circuit voltage of the target battery cell; After continuing to store the target battery cell for a second duration under a second temperature condition, obtaining a second open-circuit voltage of the target battery cell; Determining the first K value according to the first open-circuit voltage and the second open-circuit voltage; After performing a self-discharge operation on the target battery cell under the second operating condition, obtaining the second K value of the target battery cell under the second operating condition includes: After storing the target battery cell for a third duration under a fourth temperature condition, obtaining a third open-circuit voltage of the target battery cell; After storing the target battery cell for a fourth duration under a fifth temperature condition, obtaining a fourth open-circuit voltage of the target battery cell; Determining the second K value according to the third open-circuit voltage and the fourth open-circuit voltage; Determining the first battery cell state of the target battery cell according to the first K value and the second K value includes at least one of the following: In the case where the first K value and / or the second K value is outside a preset K value range, determining that the target battery cell is in a state of battery cell abnormality, wherein the preset K value range is associated with the target battery cell; In the case where the absolute value of the difference between the first K value and the second K value is greater than a first preset value, determining that the target battery cell is in a state of battery cell abnormality; After obtaining the second K value of the target battery cell under the second operating condition, the method further includes: After performing a self-discharge operation on the target battery cell under the third operating condition, obtaining a third K value of the target battery cell under the third operating condition, wherein the temperature of the target battery cell under the third operating condition is higher than the temperature under the first operating condition and the second operating condition; Determining a second battery cell state of the target battery cell according to the first K value, the second K value and the third K value; After performing a self-discharge operation on the target battery cell under the third operating condition, obtaining the third K value of the target battery cell under the third operating condition includes: After storing the target battery cell for a fifth duration under a sixth temperature condition, obtaining a fifth open-circuit voltage of the target battery cell, wherein the temperature of the target battery cell under the sixth temperature condition is greater than the temperature of the target battery cell under the fifth temperature condition; Determine the third K value according to the fourth open-circuit voltage and the fifth open-circuit voltage; Determine the second cell state of the target cell according to the first K value, the second K value and the third K value, including at least one of the following: When the first K value, the second K value and / or the third K value are outside the preset K value range, determine that the target cell is in an abnormal state; When the absolute value of the difference between the first K value and the second K value is greater than a first preset value, determine that the target cell is in an abnormal state; When the absolute value of the difference between the second K value and the third K value is greater than a second preset value, determine that the target cell is in an abnormal state.

2. The method according to claim 1, characterized in that, After performing cyclic charge and discharge on the target cell, charge the target cell to a target power, including: Under a third temperature condition, perform cyclic constant current and constant voltage charge and discharge on the target cell; After performing charge and discharge on the target cell a preset number of times, charge the target cell with constant current and constant voltage to the target power.

3. A state detection device for an electric cell, characterized in that, Include: A first acquisition module, configured to, after performing a self-discharge operation on a target cell under a first operating condition, acquire a first K value of the target cell under the first operating condition; A first control module, configured to charge the target cell to a target power after performing cyclic charge and discharge on the target cell; A second acquisition module, configured to, after performing a self-discharge operation on the target cell charged to the target power under a second operating condition, acquire a second K value of the target cell under the second operating condition; A first determination module, configured to determine a first cell state of the target cell according to the first K value and the second K value; A third acquisition module, configured to, after performing a self-discharge operation on a target cell under a third operating condition, acquire a third K value of the target cell under the third operating condition, where the temperature of the target cell under the third operating condition is higher than the temperature under the first operating condition and the second operating condition; A second determination module, configured to determine a second cell state of the target cell according to the first K value, the second K value and the third K value; The first acquisition module is specifically configured to: charge the target cell with constant current and constant voltage to the target power; after storing the target cell for a first duration under a first temperature condition, acquire a first open-circuit voltage of the target cell; after continuing to store the target cell for a second duration under a second temperature condition, acquire a second open-circuit voltage of the target cell; determine the first K value according to the first open-circuit voltage and the second open-circuit voltage; The second acquisition module is specifically configured to: after storing the target cell for a third duration under a fourth temperature condition, acquire a third open-circuit voltage of the target cell; after storing the target cell for a fourth duration under a fifth temperature condition, acquire a fourth open-circuit voltage of the target cell; determine the second K value according to the third open-circuit voltage and the fourth open-circuit voltage; The first determination module is specifically configured to: when the first K value and / or the second K value is outside the preset K value range, determine that the target battery cell is in an abnormal state, where the preset K value range is associated with the target battery cell; and / or, when the absolute value of the difference between the first K value and the second K value is greater than a first preset value, determine that the target battery cell is in an abnormal state; The third acquisition module is specifically configured to: after storing the target battery cell for a fifth duration under a sixth temperature condition, acquire a fifth open-circuit voltage of the target battery cell, where the temperature of the target battery cell under the sixth temperature condition is greater than the temperature of the target battery cell under the fifth temperature condition; determine a third K value according to the fourth open-circuit voltage and the fifth open-circuit voltage; The second determination module is specifically configured to: when the first K value, the second K value and / or the third K value is outside the preset K value range, determine that the target battery cell is in an abnormal state; when the absolute value of the difference between the first K value and the second K value is greater than a first preset value, determine that the target battery cell is in an abnormal state; and / or, when the absolute value of the difference between the second K value and the third K value is greater than a second preset value, determine that the target battery cell is in an abnormal state.

4. An electronic device, characterized in that, It includes a processor and a memory, the memory stores machine-executable instructions that can be executed by the processor, and the processor executes the machine-executable instructions to implement the method for detecting the state of the battery cell according to claim 1 or 2.

Images