Method and device for testing stepped steady-state thermal safety of lithium ion battery after fast charging cycle

Abstract

The invention discloses a stepped steady-state thermal safety test method and device for a lithium ion battery after fast charging circulation, and relates to the technical field of battery test.The method comprises the steps that lithium ion battery samples after fast charging circulation are obtained, and the lithium ion battery samples are grouped; carrying out a stepped steady-state thermal test on a first group of the lithium ion battery samples to obtain temperature change data and voltage change data of the lithium ion battery samples in the stepped steady-state thermal test; performing a short-circuit test on a second group of the lithium ion battery samples to obtain heating data and spark phenomenon data of the lithium ion battery samples in the short-circuit test; according to the temperature change data and the voltage change data of the stepped steady-state thermal test, judging the thermal safety performance of the lithium ion battery sample in the stepped steady-state thermal test; according to the heating data and the spark phenomenon data of the short circuit test, judging the thermal safety performance of the lithium ion battery sample in the short circuit test; and generating a thermal safety evaluation report of the lithium ion battery sample by integrating thermal safety performance judgment results of the stepped steady-state thermal test and the short-circuit test.

Description

Technical Field

[0001] The present application relates to the technical field of battery testing, and particularly to a method and device for testing the stepped steady-state thermal safety of a lithium-ion battery after fast charge cycling. Background Art

[0002] With the rapid development of the global new energy vehicle industry, power batteries, as the core components of new energy vehicles, directly affect the vehicle's cruising range, charging time, service life, and safety. In recent years, fast charging technology has become an important development direction in the field of power batteries, and major companies have successively launched high-rate fast charging products, claiming that they can complete high-proportion charging in a short time. However, while fast charging technology improves charging efficiency, it also poses higher requirements for the thermal safety performance of the battery. Since the battery needs to withstand a larger current during fast charging and users frequently perform fast charge cycling in daily use, the thermal stability of the battery faces severe challenges. According to statistics, a considerable part of new energy vehicle fire accidents occur during the charging process or the idle stage after charging, exposing the severity of the battery thermal safety problem after fast charge cycling.

[0003] Currently, the industry's testing of power batteries mainly focuses on aspects such as charging time, charging efficiency, and cycle life, and there are already various testing methods for evaluating the fast charging performance of batteries. For example, by measuring the charging time, voltage change, and temperature rise of the battery at different rates, the fast charging ability of the battery is evaluated. In addition, some testing methods also involve the thermal stability test of the battery in a high-temperature environment to simulate the performance of the battery under extreme temperature conditions. However, most of these testing methods focus on the charging efficiency and cycle life of the battery and lack a systematic evaluation of the thermal safety performance of the battery after fast charge cycling. Summary of the Invention

[0004] The purpose of the present application is to provide a method and device for testing the stepped steady-state thermal safety of a lithium-ion battery after fast charge cycling.

[0005] To achieve the above purpose, the present application provides the following solutions:

[0006] In a first aspect, the present application provides a method for testing the stepped steady-state thermal safety of a lithium-ion battery after fast charge cycling, including:

[0007] Obtaining a lithium-ion battery sample after fast charge cycling and grouping the lithium-ion battery sample;

[0008] Performing a stepped steady-state thermal test on a first group of the lithium-ion battery samples to obtain temperature change data and voltage change data of the lithium-ion battery samples during the stepped steady-state thermal test;

[0009] Perform a short - circuit test on the second group in the lithium - ion battery sample, and obtain the heat - generation data and spark - phenomenon data of the lithium - ion battery sample during the short - circuit test;

[0010] Based on the temperature - change data and voltage - change data of the step - steady - state thermal test, determine the thermal safety performance of the lithium - ion battery sample during the step - steady - state thermal test;

[0011] Based on the heat - generation data and spark - phenomenon data of the short - circuit test, determine the thermal safety performance of the lithium - ion battery sample during the short - circuit test;

[0012] Based on the comprehensive judgment results of the thermal safety performance of the step - steady - state thermal test and the short - circuit test, generate a thermal safety evaluation report for the lithium - ion battery sample.

[0013] Optionally, the step of obtaining the lithium - ion battery sample after fast - charge cycling and grouping the lithium - ion battery sample includes:

[0014] Prepare 8 lithium - ion battery samples after fast - charge cycling, and divide the lithium - ion battery samples into four groups: A, B, C, and D, with 2 lithium - ion battery samples in each group;

[0015] Define the fast - charge cycling as a charging rate ≥ 3C, and the lithium - ion battery sample completes 300 fast - charge cycles or completes the fast - charge cycles according to the number of times specified by the preset standard.

[0016] Optionally, the step of performing a step - steady - state thermal test on the first group in the lithium - ion battery sample and obtaining the temperature - change data and voltage - change data of the lithium - ion battery sample during the step - steady - state thermal test includes:

[0017] Place the lithium - ion battery sample in a high - temperature explosion - proof chamber, and arrange sensors in the high - temperature explosion - proof chamber to measure the open - circuit voltage at the terminals of the lithium - ion battery sample;

[0018] Starting from room temperature, gradually increase the temperature in the high - temperature explosion - proof chamber by 10°C each time, and let it stand for 1 hour after each temperature increase to allow the lithium - ion battery sample to reach a steady - state temperature;

[0019] Repeat the process of increasing the temperature and standing until the temperature of the lithium - ion battery sample reaches the preset final temperature;

[0020] Record the temperature - change data and voltage - change data of the lithium - ion battery sample during the step - steady - state thermal test.

[0021] Optionally, the calculation method for the preset final temperature Tw is:

[0022] Calculate the final temperature Tw according to the fast charge cycle number n of the lithium-ion battery sample, the total designed life cycle number Ltotal of the battery at the time of factory shipment, and the initial state thermal runaway temperature Tc of the battery;

[0023] Among them, the calculation formula of Tw is: Tw = Tc × (1 - n / Ltotal * 0.8).

[0024] Optionally, the step of performing a short-circuit test on the second group in the lithium-ion battery sample and obtaining the heat generation data and spark phenomenon data of the lithium-ion battery sample in the short-circuit test includes:

[0025] Short-circuit the positive and negative electrodes of the lithium-ion battery sample, and observe the heat generation phenomenon and spark phenomenon of the lithium-ion battery sample during the short-circuit process;

[0026] Record the heat generation data and spark phenomenon data of the lithium-ion battery sample in the short-circuit test.

[0027] Optionally, the step of judging the thermal safety performance of the lithium-ion battery sample in the stepwise steady-state thermal test according to the temperature change data and voltage change data of the stepwise steady-state thermal test includes:

[0028] Judge whether the open-circuit voltage drop at the end of the lithium-ion battery sample during the stepwise steady-state thermal test does not exceed 25% of the initial voltage;

[0029] Judge whether the lithium-ion battery sample does not catch fire, explode, or leak within 1 hour after reaching the final temperature Tw;

[0030] If the lithium-ion battery sample meets the above conditions, it is determined that the thermal safety performance of the lithium-ion battery sample in the stepwise steady-state thermal test is qualified.

[0031] Optionally, the step of judging the thermal safety performance of the lithium-ion battery sample in the short-circuit test according to the heat generation data and spark phenomenon data of the short-circuit test includes:

[0032] Judge whether the lithium-ion battery sample does not catch fire, explode, or leak after the short-circuit test ends;

[0033] Judge whether there is no sparking phenomenon at the tab of the lithium-ion battery sample during the short-circuit test;

[0034] If the lithium-ion battery sample meets the above conditions, it is determined that the thermal safety performance of the lithium-ion battery sample in the short-circuit test is qualified.

[0035] In a second aspect, the present application provides a stepwise steady-state thermal safety test device for a lithium-ion battery after fast charge cycling, including:

[0036] An acquisition module, configured to acquire lithium-ion battery samples after fast charge cycles and group the lithium-ion battery samples;

[0037] A test module, configured to perform a stepped steady-state thermal test on a first group of the lithium-ion battery samples to obtain temperature change data and voltage change data of the lithium-ion battery samples during the stepped steady-state thermal test;

[0038] Perform a short-circuit test on a second group of the lithium-ion battery samples to obtain heat generation data and spark phenomenon data of the lithium-ion battery samples during the short-circuit test;

[0039] An evaluation module, configured to judge the thermal safety performance of the lithium-ion battery samples during the stepped steady-state thermal test according to the temperature change data and voltage change data of the stepped steady-state thermal test;

[0040] Judge the thermal safety performance of the lithium-ion battery samples during the short-circuit test according to the heat generation data and spark phenomenon data of the short-circuit test;

[0041] Generate a thermal safety evaluation report for the lithium-ion battery samples by integrating the judgment results of the thermal safety performance of the stepped steady-state thermal test and the short-circuit test.

[0042] Optionally, the acquisition module is further configured to:

[0043] Prepare 8 lithium-ion battery samples after fast charge cycles, and divide the lithium-ion battery samples into four groups A, B, C, and D, with 2 lithium-ion battery samples in each group;

[0044] Define the fast charge cycle as a charge rate ≥ 3C, and the lithium-ion battery samples complete 300 fast charge cycles or complete the fast charge cycles according to the number of times specified by a preset standard.

[0045] Optionally, the test module is further configured to:

[0046] Place the lithium-ion battery samples in a high-temperature explosion-proof chamber, and arrange sensors in the high-temperature explosion-proof chamber to measure the open-circuit voltage at the terminals of the lithium-ion battery samples;

[0047] Starting from room temperature, gradually increase the temperature in the high-temperature explosion-proof chamber by 10°C each time, and let it stand for 1 hour after each temperature increase to enable the lithium-ion battery samples to reach a steady-state temperature;

[0048] Repeat the process of increasing the temperature and standing until the temperature of the lithium-ion battery samples reaches a preset final temperature;

[0049] Record the temperature change data and voltage change data of the lithium-ion battery samples during the stepped steady-state thermal test.

[0050] Optionally, the calculation method of the preset final temperature Tw is as follows:

[0051] Calculate the final temperature Tw according to the fast charge cycle number n of the lithium-ion battery sample, the total battery factory-designed life cycle number Ltotal, and the initial state thermal runaway temperature Tc of the battery;

[0052] Among them, the calculation formula of Tw is: Tw = Tc × (1 - n / Ltotal * 0.8).

[0053] Optionally, the test module is further configured to:

[0054] Short-circuit the positive and negative electrodes of the lithium-ion battery sample, and observe the heat generation phenomenon and spark phenomenon of the lithium-ion battery sample during the short-circuit process;

[0055] Record the heat generation data and spark phenomenon data of the lithium-ion battery sample during the short-circuit test.

[0056] Optionally, the evaluation module is further configured to:

[0057] Judge whether the voltage drop at the open terminal during the stepped steady-state thermal test of the lithium-ion battery sample does not exceed 25% of the initial voltage;

[0058] Judge whether the lithium-ion battery sample does not catch fire, explode, or leak within 1 hour after reaching the final temperature Tw;

[0059] If the lithium-ion battery sample meets the above conditions, it is determined that the thermal safety performance of the lithium-ion battery sample in the stepped steady-state thermal test is qualified.

[0060] Optionally, the evaluation module is further configured to:

[0061] Judge whether the lithium-ion battery sample does not catch fire, explode, or leak after the short-circuit test ends;

[0062] Judge whether there is no sparking phenomenon at the tab during the short-circuit test of the lithium-ion battery sample;

[0063] If the lithium-ion battery sample meets the above conditions, it is determined that the thermal safety performance of the lithium-ion battery sample in the short-circuit test is qualified.

[0064] In a third aspect, the present application provides a computer device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, where the processor executes the computer program to implement the steps of the lithium-ion battery fast charge cycle followed by stepped steady-state thermal safety test method described in any one of the above.

[0065] Fourthly, the present application provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method for testing the stepped steady-state thermal safety of a lithium-ion battery after fast charging cycles described in any one of the above are implemented.

[0066] Fifthly, the present application provides a computer program product, including a computer program. When the computer program is executed by a processor, the steps of the method for testing the stepped steady-state thermal safety of a lithium-ion battery after fast charging cycles described in any one of the above are implemented.

[0067] According to the specific embodiments provided by the present application, the following technical effects are disclosed:

[0068] The present application provides a method and a device for testing the stepped steady-state thermal safety of a lithium-ion battery after fast charging cycles. Through stepped steady-state thermal testing and short-circuit testing, the thermal safety performance of the battery after fast charging cycles can be comprehensively evaluated. The stepped steady-state thermal testing simulates the thermal stability of the battery in a high-temperature environment, and the short-circuit testing simulates the safety performance in extreme cases, ensuring that the battery still has good thermal safety after fast charging. This method adopts multi-group sample testing and repeated verification, improves the reliability and accuracy of the test results, and ensures the repeatability and comparability of the test through a standardized process. Description of the Drawings

[0069] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0070] Figure 1 It is a schematic flow chart of a method for testing the stepped steady-state thermal safety of a lithium-ion battery after fast charging cycles provided by an embodiment of the present application;

[0071] Figure 2 It is a schematic principle diagram of a method for testing the stepped steady-state thermal safety of a lithium-ion battery after fast charging cycles provided by an embodiment of the present application;

[0072] Figure 3 It is a schematic functional module diagram of a device for testing the stepped steady-state thermal safety of a lithium-ion battery after fast charging cycles provided by an embodiment of the present application;

[0073] Figure 4 It is a schematic structural diagram of a computer device provided by an embodiment of the present application. Detailed Embodiments

[0074] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present application.

[0075] As Figure 1 shown, some embodiments of the present application provide a method for testing the stepped steady-state thermal safety of a lithium-ion battery after fast charge cycling. In the embodiments of the present application, the following steps 101 to 104 are included. Among them:

[0076] Step 101, obtain lithium-ion battery samples after fast charge cycling, and group the lithium-ion battery samples.

[0077] In the embodiments of the present application, a batch of lithium-ion battery samples after fast charge cycling needs to be prepared first. The definition of fast charge cycling is that the charge rate ≥ 3C, and the samples need to be processed by fast charge cycling such as 3C fast charge and 1C fast discharge full charge and full discharge cycle a certain number of times (such as 300 times or according to the enterprise regulations).

[0078] Subsequently, these lithium-ion battery samples are grouped. It can be assumed that these samples are divided into several groups, such as groups A, B, C, and D in the example, and each group contains a certain number of battery cells (such as 2 battery cells in each group). In this explanation, we focus on the first group (for stepped steady-state thermal test) and the second group (for short-circuit test).

[0079] Step 102, perform a stepped steady-state thermal test on the first group of the lithium-ion battery samples, and obtain the temperature change data and voltage change data of the lithium-ion battery samples in the stepped steady-state thermal test.

[0080] In the embodiments of the present application, the test method is to place the samples after fast charge cycling in the full charge state (100% SOC) in a high-temperature explosion-proof chamber, and synchronously install and arrange sensors to measure the open-circuit voltage at the battery terminals.

[0081] Starting from room temperature, gradually increase the temperature in the chamber (such as increasing by 10°C each time), and let the battery temperature fully adapt to the target temperature at each target temperature for a period of time (such as 1 hour) to ensure that the battery reaches a steady-state temperature. During this process, record the temperature change data and voltage change data of the battery. These data will be used for subsequent thermal safety performance judgment.

[0082] Specifically, place the sample after fast charge cycling at 100% SOC (fully charged state) in a high-temperature explosion-proof chamber, and synchronously install and arrange sensors to measure the open-circuit voltage at the battery terminals. Starting from room temperature, set the temperature in the chamber to increase by 10°C, and then let it stand for 1 hour to allow the battery temperature to fully adapt to the target temperature to ensure that the battery reaches a steady-state temperature. After 1 hour, continue to adjust the temperature in the chamber to increase by 10°C, and then let it stand for 1 hour. Repeat the above process of increasing the temperature and standing until the final temperature of the battery reaches Tw. The schematic diagram of the stepped steady-state thermal test conditions is shown in Figure 2 。

[0083] Step 103: Conduct a short-circuit test on the second group of the lithium-ion battery samples to obtain the heat generation data and spark phenomenon data of the lithium-ion battery samples during the short-circuit test.

[0084] In the embodiment of the present application, the test method is to short-circuit the positive and negative electrodes of the sample after fast charge cycling at 100% SOC (fully charged state), and observe the heat generation and spark phenomenon at the battery tabs. During the test, record the heat generation data and spark phenomenon data of the battery. These data will also be used for subsequent judgment of thermal safety performance.

[0085] Step 104: Based on the temperature change data and voltage change data of the stepped steady-state thermal test, judge the thermal safety performance of the lithium-ion battery samples during the stepped steady-state thermal test.

[0086] In the embodiment of the present application, the temperature change data and voltage change data obtained in step 102 will be used to judge the thermal safety performance of the lithium-ion battery samples during the stepped steady-state thermal test. The specific judgment criteria may include: the voltage drop of the open-circuit voltage at the battery terminals during the stepped steady-state thermal test does not exceed a certain proportion (such as 25%) of the initial voltage, and the battery does not catch fire, explode, or leak liquid after reaching the final test temperature (such as Tw) and standing for a period of time.

[0087] Step 105: Based on the heat generation data and spark phenomenon data of the short-circuit test, judge the thermal safety performance of the lithium-ion battery samples during the short-circuit test.

[0088] In the embodiment of the present application, the heat generation data and spark phenomenon data obtained in step 103 will be used to judge the thermal safety performance of the lithium-ion battery samples during the short-circuit test. The specific judgment criteria may include: the battery does not catch fire, explode, or leak liquid after the short-circuit test, and there is no sparking phenomenon at the battery tabs.

[0089] Step 106: Based on the comprehensive judgment results of the thermal safety performance of the stepped steady-state thermal test and the short-circuit test, generate a thermal safety evaluation report for the lithium-ion battery samples.

[0090] In the embodiments of the present application, the thermal safety evaluation report of the lithium-ion battery sample is generated by integrating the thermal safety performance judgment results in steps 104 and 105. The content of the report may include, but is not limited to: the specific performance of the lithium-ion battery sample in the stepwise steady-state thermal test and the short-circuit test, whether it meets the thermal safety performance requirements, and possible potential safety hazards or improvement suggestions, etc.

[0091] Through the stepwise steady-state thermal test and the short-circuit test in the embodiments of the present application, the thermal safety performance of the battery after fast charge cycling can be comprehensively evaluated. The stepwise steady-state thermal test simulates the thermal stability of the battery in a high-temperature environment, and the short-circuit test simulates the safety performance in extreme cases, ensuring that the battery still has good thermal safety after fast charging. This method uses multiple groups of sample tests and repeated verification, improving the reliability and accuracy of the test results, and ensuring the repeatability and comparability of the test through a standardized process.

[0092] Optionally, step 101 includes:

[0093] Step 1011, prepare 8 lithium-ion battery samples after fast charge cycling, and divide the lithium-ion battery samples into four groups A, B, C, and D, with 2 lithium-ion battery samples in each group.

[0094] In the embodiments of the present application, first, 8 lithium-ion batteries need to be selected as experimental samples. These batteries should be of the same type, the same batch, or have similar performance characteristics to ensure the accuracy and comparability of the experimental results. These batteries need to have experienced fast charge cycling beforehand, that is, they have undergone the charging and discharging cycle process according to specific fast charge conditions. Divide these 8 lithium-ion battery samples into four groups, labeled A, B, C, and D respectively. Each group contains 2 lithium-ion battery samples. Such a setting can provide a sufficient sample size for subsequent experiments to conduct statistical analysis and reduce the influence of accidental errors.

[0095] Step 1012, define the fast charge cycling as the charging rate ≥ 3C, and the lithium-ion battery sample completes 300 fast charge cycles or completes the fast charge cycles according to the number of times specified by the preset standard.

[0096] In the embodiments of the present application, fast charge cycling refers to the process of charging and discharging the lithium-ion battery at a relatively high charging rate. It is clearly stipulated that the charging rate of fast charge cycling should be ≥ 3C. The charging rate (C-rate) is a parameter indicating the charge and discharge speed of the battery. 1C means that the battery can be fully charged or discharged within 1 hour. Therefore, 3C means that the battery can be fully charged or discharged within 1 / 3 hour (i.e., about 20 minutes).

[0097] The lithium-ion battery samples need to complete 300 fast charge cycles, or complete the fast charge cycles according to the number of times specified by the preset standard. 300 times is a relatively large number of cycles, which is used to simulate the performance changes of the battery during long-term use. If there are specific requirements or standards for the experiment, the fast charge cycles can also be carried out according to the number of times specified by these requirements or standards. After completing the specified number of fast charge cycles, these batteries will be used for subsequent experiments or tests to evaluate their performance, lifespan, safety and other indicators.

[0098] Optionally, step 102 includes:

[0099] Step 1021, place the lithium-ion battery sample in a high-temperature explosion-proof chamber, and arrange sensors in the high-temperature explosion-proof chamber to measure the open-circuit voltage at the terminals of the lithium-ion battery sample.

[0100] In the embodiment of the present application, the previously prepared lithium-ion battery sample is placed in a high-temperature explosion-proof chamber. The high-temperature explosion-proof chamber is an experimental device that can control the temperature and has a safety explosion-proof function, and is used to conduct safety tests on the battery under high-temperature conditions. Sensors are arranged in the high-temperature explosion-proof chamber, and these sensors are used to measure the open-circuit voltage (OCV, Open Circuit Voltage) at the terminals of the lithium-ion battery sample. The open-circuit voltage is the voltage of the battery in the open-circuit state (i.e., no current flows through), and it is an important parameter for evaluating the state of the battery. By measuring the open-circuit voltage of the lithium-ion battery sample in real time or regularly through the sensors, the voltage value of the battery in the initial state is recorded, providing a benchmark for the impact of subsequent temperature changes on the battery performance.

[0101] Step 1022, starting from room temperature, gradually increase the temperature in the high-temperature explosion-proof chamber by 10°C each time, and let it stand for 1 hour after each temperature increase to make the lithium-ion battery sample reach the steady-state temperature.

[0102] In the embodiment of the present application, the temperature in the high-temperature explosion-proof chamber is set to room temperature as the starting temperature of the experiment. The temperature in the high-temperature explosion-proof chamber is gradually increased in steps of 10°C each time. This stepped temperature increase method helps to observe the performance changes of the battery at different temperatures. After each temperature increase, keep the temperature in the high-temperature explosion-proof chamber constant and let it stand for 1 hour. During this period, the lithium-ion battery sample will gradually reach the steady-state temperature corresponding to this temperature, that is, the temperature distribution inside the battery becomes uniform, and the performance parameters of the battery (such as voltage, internal resistance, etc.) tend to be stable.

[0103] Step 1023, repeat the process of increasing the temperature and standing until the temperature of the lithium-ion battery sample reaches the preset final temperature.

[0104] In an embodiment of the present application, according to the method in step 1022, the process of raising the temperature and standing still is repeated. Continue to raise the temperature until the temperature of the lithium-ion battery sample reaches the final temperature preset in the experiment. This final temperature is determined according to the experimental purpose and the performance characteristics of the battery, and may be the upper limit of the safe operating temperature of the battery or higher.

[0105] Step 1024, record the temperature change data and voltage change data of the lithium-ion battery sample during the stepped steady-state thermal test.

[0106] In an embodiment of the present application, during the entire stepped steady-state thermal test, use sensors or data recording devices to record the temperature change data in the high-temperature explosion-proof chamber in real time or at regular intervals. These data are used to analyze the thermal behavior of the battery at different temperatures. At the same time, record the open-circuit terminal voltage change data of the lithium-ion battery sample at each temperature steady state. These data are used to evaluate the influence of temperature on the electrochemical performance of the battery, such as the attenuation of battery capacity, the change of internal resistance, etc.

[0107] Optionally, the calculation method of the preset final temperature Tw is: according to the fast charge cycle number n of the lithium-ion battery sample, the total number of cycles Ltotal of the battery's factory-designed life cycle, and the initial state thermal runaway temperature Tc of the battery, calculate the final temperature Tw.

[0108] Among them, the calculation formula of Tw is: Tw = Tc × (1 - n / Ltotal * 0.8).

[0109] In an embodiment of the present application, the fast charge cycle number n refers to the number of fast charge cycles that the lithium-ion battery sample has experienced. A fast charge cycle usually refers to the charging and discharging process carried out at a relatively high charging rate, and this cycle will have an impact on the performance and life of the battery.

[0110] The total number of cycles Ltotal of the battery's factory-designed life cycle is the total number of cycles that the battery manufacturer expects the battery to withstand during design, that is, the design life of the battery. This value is usually determined based on factors such as the chemical composition, structural design, and manufacturing process of the battery.

[0111] The initial state thermal runaway temperature Tc of the battery refers to the temperature at which the battery undergoes thermal runaway in the initial state (i.e., without any cycles or aging). Thermal runaway is a phenomenon in which the battery releases a large amount of heat due to the acceleration of internal chemical reactions under overheating conditions, resulting in a sharp increase in temperature. Tc is an important parameter for evaluating the safety of the battery.

[0112] Determine the specific values of the fast charge cycle number n of the lithium-ion battery sample, the total designed life cycle number L of the battery at the time of factory shipment, and the initial state thermal runaway temperature Tc of the battery. Then, substitute these values into the formula Tw = Tc × (n / Ltotal) for calculation. The finally obtained Tw value is the final temperature at which thermal runaway may occur for the battery under the current aging degree. By calculating Tw, the change in the thermal safety of the battery after experiencing a certain number of fast charge cycles can be evaluated. If the Tw value is close to or exceeds the upper limit of the battery's operating temperature or the safe temperature range, it means that the thermal safety of the battery may be threatened, and corresponding measures need to be taken to prevent the occurrence of thermal runaway.

[0113] Optionally, step 103 includes:

[0114] Step 1031: Short-circuit the positive and negative electrodes of the lithium-ion battery sample, and observe the heat generation phenomenon and spark phenomenon of the lithium-ion battery sample during the short-circuit process.

[0115] In the embodiment of the present application, the positive and negative electrodes of the lithium-ion battery sample need to be directly connected together to form a short-circuit state. This is usually achieved by directly contacting the positive and negative electrodes of the battery using a wire or a metal sheet. A short circuit is an extreme electrical connection state, which will cause a large amount of current to flow through the battery internally instantaneously. Since the internal resistance of the battery is very small, the current will be very large.

[0116] During the short-circuit process, due to a large amount of current flowing through the battery internally, the battery will generate a large amount of heat. This is because when the current passes through the battery internally, it will encounter resistance, thereby generating Joule heat. Observing the heat generation situation of the battery during the short-circuit process, including the heat generation speed, the degree of heat generation, and whether the heat generation is uniform, etc., are all important indicators for evaluating the safety of the battery.

[0117] At the moment of short circuit, due to the sudden increase in current, sparks may be generated at the contact points of the positive and negative electrodes of the battery. The size, color, and duration of the sparks can all provide information about the internal state of the battery and the short-circuit process. Observing the spark phenomenon is crucial for evaluating the safety of the battery under short-circuit conditions because the sparks may cause dangerous situations such as fires or explosions.

[0118] Step 1032: Record the heat generation data and spark phenomenon data of the lithium-ion battery sample during the short-circuit test.

[0119] In the embodiment of the present application, during the short-circuit test process, it is necessary to use a temperature measurement device (such as a thermocouple, an infrared thermometer, etc.) to record the surface temperature or internal temperature of the lithium-ion battery sample in real time or at regular intervals. The recorded data should include the temperature change curve over time, the highest temperature point, the heat generation rate, etc., and these data are used for subsequent analysis of the thermal behavior of the battery under short-circuit conditions.

[0120] Regarding the spark phenomenon, it is necessary to record detailed information such as the time when the spark appears, the duration, the size, the color, and whether there is any accompanying sound. These data can be captured and recorded through observation or by using devices such as high-speed cameras for subsequent detailed analysis of the spark phenomenon.

[0121] Optionally, step 104 includes:

[0122] Step 1041: Determine whether the voltage drop of the open-circuit voltage at the terminals of the lithium-ion battery sample during the stepped steady-state thermal test does not exceed 25% of the initial voltage.

[0123] In the embodiments of the present application, the open-circuit voltage (OCV) of the battery is the voltage of the battery in the open-circuit state. During the stepped steady-state thermal test, as the temperature increases, the chemical reaction rate of the battery may change, resulting in a change in the open-circuit voltage. The voltage drop of the open-circuit voltage refers to the decrease in the open-circuit voltage of the battery relative to the initial voltage during the test.

[0124] During the stepped steady-state thermal test, it is necessary to measure the open-circuit voltage of the lithium-ion battery sample in real-time or regularly and record its changes. Compare the lowest open-circuit voltage during the test with the initial voltage to calculate the percentage of voltage drop. Determine whether this percentage of voltage drop does not exceed 25%. If the voltage drop exceeds 25%, it may indicate that the performance stability of the battery at high temperatures is poor, and its safety needs to be further evaluated.

[0125] Step 1042: Determine whether the lithium-ion battery sample does not catch fire, explode, or leak within 1 hour after reaching the final temperature Tw.

[0126] In the embodiments of the present application, the final temperature Tw is the highest temperature reached by the battery during the stepped steady-state thermal test, which is usually calculated based on factors such as the designed life of the battery and the number of fast charge cycles. After the battery reaches the final temperature Tw, it is necessary to continuously observe the behavior of the battery, especially whether dangerous situations such as catching fire, exploding, or leaking occur. The observation time is at least 1 hour to ensure the stability of the battery at high temperatures. If the battery does not catch fire, explode, or leak within 1 hour, it is considered that the safety of the battery at this temperature is qualified.

[0127] Step 1043: If the lithium-ion battery sample meets the above conditions, it is determined that the thermal safety performance of the lithium-ion battery sample in the stepped steady-state thermal test is qualified.

[0128] In the embodiment of the present application, based on the results of step 1041 and step 1042, the thermal safety performance of the lithium-ion battery sample is comprehensively evaluated. If during the stepped steady-state thermal test of the battery, the voltage drop at the open circuit terminal does not exceed 25% of the initial voltage, and the battery does not catch fire, explode, or leak within 1 hour after reaching the final temperature Tw, it is considered that the thermal safety performance of the battery is qualified.

[0129] If the battery meets all the above conditions, it can be determined that the thermal safety performance of the lithium-ion battery sample in the stepped steady-state thermal test is qualified. This means that the battery has good performance stability and safety at high temperatures, and its feasibility in practical applications can be further considered.

[0130] Optionally, step 105 includes:

[0131] Step 1051, determine whether the lithium-ion battery sample does not catch fire, explode, or leak after the short-circuit test ends.

[0132] In the embodiment of the present application, the short-circuit test is an important test in the safety assessment of lithium-ion batteries, and it evaluates the safety of the battery by simulating the behavior of the battery under extreme conditions. After the short-circuit test ends, the battery may be in a high-temperature, high-pressure, or unstable state. Therefore, special attention needs to be paid to whether dangerous situations such as fire, explosion, or leakage occur. After the short-circuit test ends, it is necessary to immediately observe the state of the lithium-ion battery sample, especially its appearance, temperature, and whether there are abnormal odors or sounds. Focus on checking whether the battery catches fire, explodes, or leaks. Fire may be manifested as open flames or smoke; explosion may be manifested as the battery case cracking or fragments flying; leakage may be manifested as electrolyte flowing out of the battery. If the battery does not catch fire, explode, or leak after the short-circuit test ends, it is considered that the safety of the battery under this test condition is qualified.

[0133] Step 1052, determine whether there is no sparking phenomenon at the tab during the short-circuit test of the lithium-ion battery sample.

[0134] In the embodiment of the present application, the tab is the positive and negative electrode lead-out end of the lithium-ion battery, usually connected to the wire or connector outside the battery. The sparking phenomenon refers to the electric spark or arc that may be generated at the tab during the short-circuit test due to the sudden increase in current. During the short-circuit test, it is necessary to closely monitor the tab of the lithium-ion battery sample, especially whether there is a sparking phenomenon. A high-speed camera or the naked eye can be used to observe whether there is a flash of light or an arc at the tab. If there is no sparking phenomenon at the tab during the short-circuit test, it is considered that the safety of the battery in this regard is qualified. The sparking phenomenon may trigger dangerous situations such as fire or explosion, so it is one of the important indicators for evaluating the battery safety.

[0135] Step 1053, if the lithium-ion battery sample meets the above conditions, it is determined that the thermal safety performance of the lithium-ion battery sample is qualified in the short-circuit test.

[0136] In the embodiments of the present application, based on the results of Step 1051 and Step 1052, the thermal safety performance of the lithium-ion battery sample in the short-circuit test is comprehensively evaluated. If the battery does not catch fire, explode or leak liquid after the short-circuit test, and there is no sparking phenomenon at the tab during the test, it is considered that the thermal safety performance of the battery is qualified. If the battery meets all the above conditions, it can be determined that the thermal safety performance of the lithium-ion battery sample in the short-circuit test is qualified. This means that the battery has good safety under short-circuit conditions, and its feasibility in actual applications can be further considered.

[0137] Based on the same inventive concept, the embodiments of the present application also provide a lithium-ion battery fast-charging cycle post-step steady-state thermal safety test device for implementing the above-mentioned lithium-ion battery fast-charging cycle post-step steady-state thermal safety test method. The solution provided by this device to solve the problem is similar to the solution described in the above method. Therefore, the specific limitations in one or more embodiments of the following lithium-ion battery fast-charging cycle post-step steady-state thermal safety test device can refer to the limitations on the lithium-ion battery fast-charging cycle post-step steady-state thermal safety test method in the above text, and will not be repeated here.

[0138] In an exemplary embodiment, as Figure 3 shown, a lithium-ion battery fast-charging cycle post-step steady-state thermal safety test device 20 is provided, including:

[0139] An acquisition module 201, configured to acquire a lithium-ion battery sample after a fast-charging cycle and group the lithium-ion battery sample;

[0140] A test module 202, configured to perform a step steady-state thermal test on the first group of the lithium-ion battery samples to obtain temperature change data and voltage change data of the lithium-ion battery samples in the step steady-state thermal test;

[0141] Perform a short-circuit test on the second group of the lithium-ion battery samples to obtain heat generation data and spark phenomenon data of the lithium-ion battery samples in the short-circuit test;

[0142] An evaluation module 203, configured to determine the thermal safety performance of the lithium-ion battery samples in the step steady-state thermal test according to the temperature change data and voltage change data of the step steady-state thermal test;

[0143] Determine the thermal safety performance of the lithium-ion battery samples in the short-circuit test according to the heat generation data and spark phenomenon data of the short-circuit test;

[0144] Generate a thermal safety evaluation report for the lithium-ion battery sample by synthesizing the judgment results of the thermal safety performance of the step steady-state thermal test and the short-circuit test.

[0145] Optionally, the obtaining module 201 is further configured to:

[0146] Prepare 8 lithium-ion battery samples after fast charge cycling, and divide the lithium-ion battery samples into four groups: A, B, C, and D, with 2 lithium-ion battery samples in each group;

[0147] Define the fast charge cycling as the charge rate ≥ 3C, and the lithium-ion battery sample completes 300 fast charge cycles or the fast charge cycles are completed according to the number of times specified by the preset standard.

[0148] Optionally, the testing module 202 is further configured to:

[0149] Place the lithium-ion battery sample in a high-temperature explosion-proof chamber, and arrange sensors in the high-temperature explosion-proof chamber to measure the open-circuit voltage at the terminals of the lithium-ion battery sample;

[0150] Starting from room temperature, gradually increase the temperature in the high-temperature explosion-proof chamber by 10 °C each time, and let it stand for 1 hour after each temperature increase to enable the lithium-ion battery sample to reach a steady-state temperature;

[0151] Repeat the process of increasing the temperature and standing until the temperature of the lithium-ion battery sample reaches the preset final temperature;

[0152] Record the temperature change data and voltage change data of the lithium-ion battery sample during the step steady-state thermal test.

[0153] Optionally, the calculation method for the preset final temperature Tw is:

[0154] Calculate the final temperature Tw according to the fast charge cycle number n of the lithium-ion battery sample, the total number of battery factory-designed life cycles Ltotal, and the initial state thermal runaway temperature Tc of the battery;

[0155] Among them, the calculation formula for Tw is: Tw = Tc × (1 - n / Ltotal * 0.8).

[0156] Optionally, the testing module 202 is further configured to:

[0157] Short-circuit the positive and negative electrodes of the lithium-ion battery sample, and observe the heat generation phenomenon and spark phenomenon of the lithium-ion battery sample during the short-circuit process;

[0158] Record the heat generation data and spark phenomenon data of the lithium-ion battery sample during the short-circuit test.

[0159] Optionally, the evaluation module 203 is further configured to:

[0160] Determine whether the voltage drop of the open-circuit voltage at the terminals of the lithium-ion battery sample during the stepped steady-state thermal test does not exceed 25% of the initial voltage;

[0161] Determine whether the lithium-ion battery sample catches fire, explodes, or leaks within 1 hour after reaching the final temperature Tw;

[0162] If the lithium-ion battery sample meets the above conditions, it is determined that the thermal safety performance of the lithium-ion battery sample in the stepped steady-state thermal test is qualified.

[0163] Optionally, the evaluation module 203 is further configured to:

[0164] Determine whether the lithium-ion battery sample catches fire, explodes, or leaks after the short-circuit test ends;

[0165] Determine whether there is no sparking phenomenon at the tabs of the lithium-ion battery sample during the short-circuit test;

[0166] If the lithium-ion battery sample meets the above conditions, it is determined that the thermal safety performance of the lithium-ion battery sample in the short-circuit test is qualified.

[0167] Through the stepped steady-state thermal test and the short-circuit test in the embodiments of the present application, the thermal safety performance of the battery after fast charge cycling can be comprehensively evaluated. The stepped steady-state thermal test simulates the thermal stability of the battery in a high-temperature environment, and the short-circuit test simulates the safety performance in extreme cases, ensuring that the battery still has good thermal safety after fast charging. This method uses multiple sets of sample tests and repeated verification to improve the reliability and accuracy of the test results, and ensures the repeatability and comparability of the test through a standardized process.

[0168] In an exemplary embodiment, a computer device is provided. The computer device can be a server or a terminal, and its internal structure diagram can be as Figure 4As shown in the figure. The computer device includes a processor, a memory, an input / output interface (Input / Output, abbreviated as I / O), and a communication interface. Among them, the processor, the memory, and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store the stepped steady-state thermal safety test data after fast charging cycles of lithium-ion batteries. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals through a network connection. When the computer program is executed by the processor, it implements a method for stepped steady-state thermal safety test after fast charging cycles of lithium-ion batteries.

[0169] Those skilled in the art can understand that Figure 4 the structure shown in the figure is only a block diagram of some structures related to the solution of this application, and does not constitute a limitation on the computer device to which the solution of this application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0170] In an exemplary embodiment, a computer device is further provided, including a memory and a processor. A computer program is stored in the memory, and when the processor executes the computer program, the steps in the above method embodiments are implemented.

[0171] In an exemplary embodiment, a computer-readable storage medium is provided, storing a computer program, and when the computer program is executed by the processor, the steps in the above method embodiments are implemented.

[0172] In an exemplary embodiment, a computer program product is provided, including a computer program, and when the computer program is executed by the processor, the steps in the above method embodiments are implemented.

[0173] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use, and processing of relevant data need to comply with relevant regulations.

[0174] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memories can include read-only memory (ROM), magnetic tapes, floppy disks, flash memories, optical memories, high-density embedded non-volatile memories, resistive random-access memories (ReRAM), magnetoresistive random-access memories (MRAM), ferroelectric random-access memories (FRAM), phase change memories (PCM), graphene memories, etc. Volatile memories can include random-access memory (RAM) or external cache memories, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random-access memory (SRAM) or dynamic random-access memory (DRAM), etc.

[0175] The databases involved in the embodiments provided in the present application can include at least one of relational databases and non-relational databases. Non-relational databases can include distributed databases based on blockchain, etc., without limitation. The processors involved in the embodiments provided in the present application can be general-purpose processors, central processors, graphics processors, digital signal processors, programmable logics, data processing logics based on quantum computing, etc., without limitation.

[0176] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0177] Specific examples are used in this article to elaborate on the principles and implementation manners of the present application. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A step-by-step steady-state thermal safety test method for a lithium-ion battery after fast charging cycles, characterized in that: The step-by-step steady-state thermal safety test method for a lithium-ion battery after fast charging cycles comprises: Obtaining lithium-ion battery samples after fast charging cycles, and grouping the lithium-ion battery samples; Performing a step steady-state thermal test on a first group of the lithium-ion battery samples to obtain temperature change data and voltage change data of the lithium-ion battery samples in the step steady-state thermal test; Performing a short circuit test on a second group of the lithium ion battery samples to obtain heating data and spark phenomenon data of the lithium ion battery samples in the short circuit test; According to the temperature change data and the voltage change data of the step steady-state thermal test, judging the thermal safety performance of the lithium-ion battery sample in the step steady-state thermal test; According to the heating data and spark phenomenon data of the short-circuit test, judging the thermal safety performance of the lithium-ion battery sample in the short-circuit test; The thermal safety performance judgment results of the step steady-state thermal test and the short-circuit test are combined to generate a thermal safety evaluation report of the lithium-ion battery sample.

2. The step-by-step steady-state thermal safety test method for a lithium-ion battery after fast charging cycles according to claim 1, characterized in that: The step of obtaining lithium-ion battery samples after fast charging cycles and grouping the lithium-ion battery samples comprises: 8 lithium-ion battery samples after fast charging cycles were prepared, and the lithium-ion battery samples were divided into four groups, A, B, C, and D, with 2 lithium-ion battery samples in each group; The fast charging cycle is defined as a charging rate ≥ 3C, and the lithium-ion battery sample completes 300 fast charging cycles or completes fast charging cycles according to the number of times specified in the preset standard.

3. The step-by-step steady-state thermal safety test method for a lithium-ion battery after fast charging cycles according to claim 1, characterized in that: The step of performing a step steady-state thermal test on the first group of the lithium-ion battery samples to obtain temperature change data and voltage change data of the lithium-ion battery samples in the step steady-state thermal test comprises: Placing the lithium-ion battery sample in a high-temperature explosion-proof chamber, arranging a sensor in the high-temperature explosion-proof chamber, and measuring the terminal open-circuit voltage of the lithium-ion battery sample; Starting from room temperature, gradually increase the temperature in the high-temperature explosion-proof chamber by 10° C. each time, and let it stand for 1 hour after each temperature increase to allow the lithium-ion battery sample to reach a steady-state temperature; Repeating the temperature increase and standing process until the temperature of the lithium-ion battery sample reaches a preset final temperature; The temperature change data and voltage change data of the lithium-ion battery sample during the step steady-state thermal test are recorded.

4. The step-by-step steady-state thermal safety test method for a lithium-ion battery after fast charging cycles according to claim 3, characterized in that: The calculation method of the preset final temperature Tw is: Calculate the final temperature Tw according to the fast charging cycle number n of the lithium-ion battery sample, the factory design life cycle number Ltotal of the battery, and the thermal runaway temperature Tc of the battery in the initial state; The calculation formula of Tw is: Tw=Tc×(1-n / Ltotal*0.8).

5. The step-by-step steady-state thermal safety test method for a lithium-ion battery after fast charging cycles according to claim 1, characterized in that: The step of performing a short circuit test on the second group of the lithium ion battery samples to obtain heating data and spark phenomenon data of the lithium ion battery samples in the short circuit test comprises: Short-circuiting the positive and negative electrodes of the lithium-ion battery sample, and observing the heating and sparking phenomena of the lithium-ion battery sample during the short-circuit process; The heating data and spark phenomenon data of the lithium-ion battery sample in the short circuit test are recorded.

6. The step-by-step steady-state thermal safety test method for a lithium-ion battery after fast charging cycles according to claim 1, characterized in that: The step of judging the thermal safety performance of the lithium-ion battery sample in the step steady-state thermal test according to the temperature change data and the voltage change data of the step steady-state thermal test comprises: Determine whether the open circuit voltage drop of the lithium ion battery sample during the step steady-state thermal test does not exceed 25% of the initial voltage; Determine whether the lithium-ion battery sample does not catch fire, explode, or leak within 1 hour after reaching the final temperature Tw; If the lithium-ion battery sample meets the above conditions, it is determined that the thermal safety performance of the lithium-ion battery sample in the step steady-state thermal test is qualified.

7. The step-by-step steady-state thermal safety test method for a lithium-ion battery after fast charging cycles according to claim 1, characterized in that: The step of judging the thermal safety performance of the lithium-ion battery sample in the short-circuit test according to the heating data and the spark phenomenon data of the short-circuit test comprises: Determine whether the lithium-ion battery sample does not catch fire, explode, or leak after the short-circuit test; Determine whether there is no spark at the tab during the short circuit test of the lithium ion battery sample; If the lithium-ion battery sample meets the above conditions, it is determined that the thermal safety performance of the lithium-ion battery sample in the short-circuit test is qualified.

8. A step-by-step steady-state thermal safety test device for lithium-ion batteries after fast charging cycles, characterized in that: The lithium-ion battery fast charging cycle step steady-state thermal safety test device comprises: An acquisition module, used for acquiring lithium-ion battery samples after fast charging cycles, and grouping the lithium-ion battery samples; A testing module, used for performing a step steady-state thermal test on a first group of the lithium-ion battery samples, and obtaining temperature change data and voltage change data of the lithium-ion battery samples in the step steady-state thermal test; Performing a short circuit test on a second group of the lithium ion battery samples to obtain heating data and spark phenomenon data of the lithium ion battery samples in the short circuit test; An evaluation module, used to determine the thermal safety performance of the lithium-ion battery sample in the step steady-state thermal test according to the temperature change data and the voltage change data of the step steady-state thermal test; According to the heating data and spark phenomenon data of the short-circuit test, judging the thermal safety performance of the lithium-ion battery sample in the short-circuit test; The thermal safety performance judgment results of the step steady-state thermal test and the short-circuit test are combined to generate a thermal safety evaluation report of the lithium-ion battery sample.

9. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the step steady-state thermal safety test method for a lithium-ion battery after fast charging cycles according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the step-by-step steady-state thermal safety testing method for a lithium-ion battery after a fast charge cycle as described in any one of claims 1 to 7 are implemented.

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