Method and device for screening self-discharge performance of battery

Abstract

The invention belongs to the technical field of lithium ion battery manufacturing, and particularly relates to a battery self-discharge performance screening method and device. The method comprises the following steps: sequentially carrying out the following stages of treatment on a formed battery: standing at a first temperature section, standing at a second temperature section and standing at a third temperature section, and acquiring performance data of the battery before and after the treatment at each stage; comparing the performance data of the battery before and after processing in each stage, and if the variation amplitude of the performance data of each battery before and after processing in each stage is within a corresponding preset range, determining that the battery is a qualified battery; wherein the temperature of the first temperature section is higher than that of the third temperature section, and the temperature of the third temperature section is higher than that of the second temperature section; the OCV attenuation difference of the abnormal batteries is amplified by 3-5 times through high and low temperature alternate shelving, the screening precision is improved, time is saved, and the cycle life of the batteries is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery manufacturing technology, and particularly relates to a method and apparatus for screening battery self-discharge performance. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, electric vehicles, and energy storage systems due to their high energy density and long cycle life. The self-discharge performance of a battery is one of the key indicators for measuring its quality consistency and long-term storage reliability.

[0003] Currently, the mainstream screening method for battery self-discharge performance in industrial production mainly relies on the long-term storage method at room temperature (usually 20-30℃). This method involves fully charging the battery and then leaving it at room temperature for 7 to 15 days, screening for abnormal batteries by measuring the decay rate of the open-circuit voltage (OCV) before and after storage. However, this method has significant drawbacks: first, the screening period is too long; second, the screening sensitivity is limited, as the electrochemical behavior differences between abnormal and normal batteries are not very obvious at room temperature, especially in identifying early micro-short circuits or slow interfacial side reactions, easily leading to missed or false positives.

[0004] To shorten screening time, the industry has attempted to use high-temperature acceleration methods, such as placing batteries in environments above 45°C for extended periods. While high-temperature screening can accelerate battery reactions, it can easily induce interfacial side reactions. Furthermore, most existing screening technologies rely solely on the rate of change of a single parameter, open-circuit voltage, as a criterion, failing to consider the impact of temperature cycling on battery interface stability, thus affecting the consistency of battery performance after screening. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a method and apparatus for screening battery self-discharge performance. By alternating high and low temperature treatment, the difference in OCV attenuation of abnormal batteries can be amplified, thereby efficiently achieving self-discharge performance screening.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a method for screening the self-discharge performance of a battery, comprising: The formed battery was subjected to the following stages of treatment in sequence: first temperature stage of rest, second temperature stage of rest, and third temperature stage of rest, and the performance data of the battery before and after each stage of treatment were obtained. Compare the battery performance data before and after each stage of processing. If the change in battery performance data before and after each stage of processing is within the corresponding preset range, then the battery is a qualified battery. The temperature in the first temperature range is higher than that in the third temperature range, and the temperature in the third temperature range is higher than that in the second temperature range.

[0007] The above-mentioned technical solution, through alternating high and low temperature static treatment, creates a temperature stress cycle, which can effectively stimulate and amplify the differences in self-discharge behavior of abnormal batteries, thereby significantly improving the sensitivity and accuracy of screening. At the same time, it shortens the time required for traditional room temperature resting, improving screening efficiency.

[0008] Optionally, the first temperature range resting includes placing the battery in an environment of 45-60°C for 12-48 hours.

[0009] The above technical solution accelerates the secondary intercalation of lithium ions and the interface reaction in a short time by placing the battery in a high-temperature environment of 45-60℃ for 12-48 hours. This makes the OCV decay of defective batteries more obvious, while avoiding the problem of excessive side reactions that may be caused by continuous high temperature. It balances screening speed and battery safety.

[0010] Optionally, the second temperature range resting includes placing the battery in an environment of 0-10°C for 24-72 hours.

[0011] The above technical solution stabilizes the SEI film structure by allowing it to stand at high temperature and then stand at a low temperature of 0-10℃ for 24-72 hours. The difference in the internal reaction rate of the battery is amplified under low temperature conditions, which helps to further distinguish between normal and abnormal batteries.

[0012] Optionally, the third temperature range resting includes: placing the battery in an environment of 20-30°C for 8-12 hours.

[0013] The above technical solution allows the battery to return to a state close to the actual operating temperature by being left to stand in a normal temperature environment of 20-30℃ for 8-12 hours. This helps to evaluate its self-discharge performance under normal conditions, ensuring that the screening results are closer to the actual application scenarios. At the same time, as a balancing stage of temperature cycling, it reduces the continuous impact of temperature stress on the battery.

[0014] Optionally, the battery performance data includes one or more of the following: open-circuit voltage, DC internal resistance, and self-heating temperature.

[0015] The above technical solution, by comprehensively monitoring one or more parameters among open-circuit voltage, DC internal resistance and self-heating temperature, can evaluate the battery status from multiple dimensions of electrochemical, impedance and thermal behavior, thereby improving the comprehensiveness and reliability of screening.

[0016] Optionally, the preset range of the change in open-circuit voltage before and after any stage of processing is 0-10mV; and / or, the preset range of the rate of change of DC internal resistance before and after any stage of processing is 0-5%; and the preset range of the change in self-heating temperature before and after any stage of processing is 0-2℃.

[0017] The above technical solution provides quantifiable judgment criteria for screening by setting reasonable threshold values ​​for parameters such as OCV change, DC internal resistance change rate, and self-heating temperature change. This facilitates automated and standardized screening to obtain batteries with qualified self-discharge performance and improves consistency.

[0018] Optionally, it also includes determining that a battery is unqualified and is eliminated when any performance data of the battery at any stage exceeds the corresponding preset range.

[0019] The above technical solution can promptly remove abnormal batteries, preventing them from entering subsequent processes and saving processing costs and time.

[0020] In a second aspect, the present invention provides a battery self-discharge performance screening device for performing the battery self-discharge performance screening method described in the first aspect, the device comprising: The temperature control unit is used to provide and control the static environment of the first temperature range, the second temperature range and the third temperature range; The test unit, located in the temperature control unit, is used to acquire performance data of the battery sample before and after each stage of resting. The processing unit is communicatively connected to the testing unit and is used to receive performance data before and after each stage of processing, and compare the changes in battery performance data before and after each stage of processing with the corresponding preset range to determine whether the battery sample is qualified.

[0021] The above technical solution integrates a temperature control unit, a testing unit, and a processing unit, enabling fully automated, high-precision multi-stage temperature cycling and parameter detection. This significantly improves the efficiency and consistency of screening operations, reduces human error, and is suitable for rapid and reliable screening in large-scale battery production.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects: This invention amplifies the difference in OCV decay of abnormal batteries by 3-5 times through alternating high and low temperature exposure, thereby improving the screening accuracy and reducing the time required for the self-discharge performance screening process to 1 / 3 of the traditional method.

[0023] This invention promotes Li-ionization by statically placing the battery at a high temperature of 45-60℃. + The SEI film is then stabilized by secondary embedding and low-temperature static setting at 0-10℃, which increases the cycle life of the battery by more than 15%. Finally, the battery is left to stand at room temperature to obtain a battery that meets the charging and discharging requirements, and then it enters the capacity grading process. Detailed Implementation

[0024] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use.

[0026] The following describes some embodiments of the present invention in detail. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0027] Example 1 Taking a 120Ah lithium iron phosphate prismatic battery as an example, the self-discharge screening of batteries from the same batch after formation is carried out by the following steps: 1. Perform the first temperature stage of resting: Place the battery in an environment of 45°C for 12 hours to stimulate potential interfacial side reactions; The open-circuit voltage measured before the first temperature section is allowed to settle is recorded as OCV. 11 The open-circuit voltage after the first temperature range has settled is denoted as OCV. 12 The DC internal resistance before settling in the first temperature range is denoted as R. 11 The DC internal resistance after the first temperature range has been allowed to settle is denoted as R. 12 The self-heating temperature before settling in the first temperature range is denoted as T. 11 The self-heating temperature after standing in the first temperature range is denoted as T. 12 Calculate the change in open-circuit voltage during this stage, ΔOCV = OCV 11 -OCV 12 DC internal resistance change rate ΔR% = (R 12- R 11 ) / R 11 ×100%, Self-heating temperature change ΔT=|T 12- T 11 |; Batteries that simultaneously meet the following criteria are allowed to enter the second temperature range for resting: 0≤ΔOCV≤10mV, 0≤ΔR%≤5%, and 0≤ΔT≤2℃. Batteries that do not meet any of these criteria are deemed unqualified due to high self-discharge and are eliminated. 2. Perform a second temperature range resting: Place the battery in an environment of 10℃ for 24 hours to stabilize the SEI film and amplify the voltage decay of the micro short-circuit battery. The open-circuit voltage measured before the second temperature section is allowed to settle is recorded as OCV. 21 The open-circuit voltage after the second temperature range has settled is denoted as OCV. 22 The DC internal resistance before settling in the second temperature range is denoted as R. 21 The DC internal resistance after resting in the second temperature range is denoted as R. 22The self-heating temperature before settling in the second temperature range is denoted as T. 21 The self-heating temperature after standing in the second temperature range is denoted as T. 22 Calculate the change in open-circuit voltage during this stage, ΔOCV = OCV 21 -OCV 22 DC internal resistance change rate ΔR% = (R 22- R 21 ) / R 21 ×100%, Self-heating temperature change ΔT=|T 22- T 21 |; Batteries that simultaneously meet the following criteria are allowed to enter the third temperature range for resting: 0≤ΔOCV≤10mV, 0≤ΔR%≤5%, and 0≤ΔT≤2℃. Batteries that do not meet any of these criteria are deemed unqualified due to high self-discharge and are eliminated. 3. Perform the third temperature stage of resting: let the battery stand at 25±2℃ for 8 hours; qualified batteries will then proceed to the capacity testing process. The open-circuit voltage measured before settling in the third temperature range is recorded as OCV. 31 The open-circuit voltage after resting in the third temperature range is denoted as OCV. 32 The DC internal resistance before settling in the third temperature range is denoted as R. 31 The DC internal resistance after resting in the third temperature range is denoted as R. 32 The self-heating temperature before settling in the third temperature range is denoted as T. 31 The self-heating temperature after standing in the third temperature range is denoted as T. 32 Calculate the change in open-circuit voltage during this stage, ΔOCV = OCV 31 -OCV 32 DC internal resistance change rate ΔR% = (R 32- R 31 ) / R 31 ×100%, Self-heating temperature change ΔT=|T 32- T 31 |; Batteries that simultaneously meet the following criteria are qualified and sent to the next process: 0≤ΔOCV≤10mV, 0≤ΔR%≤5%, and 0≤ΔT≤2℃. Batteries that do not meet any of these criteria are judged as unqualified batteries with high self-discharge and are eliminated.

[0028] This embodiment also provides a battery self-discharge performance screening device for performing the above-described battery self-discharge performance screening method. The device includes: The temperature control unit is used to provide and control the static environment of the first temperature range, the second temperature range and the third temperature range; The test unit, located in the temperature control unit, is used to acquire performance data of the battery sample before and after each stage of resting. The processing unit is communicatively connected to the testing unit and is used to receive performance data before and after each stage of processing, and compare the changes in battery performance data before and after each stage of processing with the corresponding preset range to determine whether the battery sample is qualified.

[0029] Example 2:

[0030] The difference between this embodiment and Embodiment 1 is that: during the first temperature period, the plant is placed in an environment of 45°C for 48 hours; during the second temperature period, the plant is placed in an environment of 10°C for 72 hours.

[0031] Example 3:

[0032] The difference between this embodiment and Embodiment 1 is that: during the first temperature period, the plant is placed in an environment of 50°C for 48 hours; during the second temperature period, the plant is placed in an environment of 5°C for 72 hours.

[0033] Example 4:

[0034] The difference between this embodiment and Embodiment 1 is that: during the first temperature period, the plant is placed in an environment of 60°C for 48 hours; during the second temperature period, the plant is placed in an environment of 5°C for 72 hours.

[0035] Example 5:

[0036] The difference between this embodiment and Embodiment 1 is that: during the first temperature period, the plant is placed in an environment of 60°C for 48 hours; during the second temperature period, the plant is placed in an environment of 0°C for 72 hours.

[0037] Comparative Example 1: The difference between this comparative example and Example 1 is that the formed battery was placed in an environment of 25°C for 168 hours, and the changes in open-circuit voltage, DC internal resistance, and self-heating temperature before and after the resting period were directly measured.

[0038] Comparative Example 2: The difference between this comparative example and Example 1 is that the battery after capacity grading was placed in an environment of 25°C for 168 hours, and the change in open circuit voltage, the rate of change in DC internal resistance, and the change in self-heating temperature before and after standing were directly measured. The battery after capacity grading is obtained by processing the battery after formation in the same way as in Example 1 through the following steps:

[0039] This invention, through alternating high and low temperature exposure, amplifies the difference in OCV decay between the prototype and the comparative abnormal battery by 3-5 times. Simultaneously, post-formation self-discharge screening facilitates interface performance optimization, promotes Li+ secondary intercalation at high temperatures, and stabilizes the SEI film at low temperatures, resulting in a cycle life improvement of over 15%. Furthermore, the total processing time is reduced to one-third of traditional methods, significantly reducing time costs and improving production efficiency.

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Those skilled in the art can make various modifications and improvements based on the principles of the present invention, and these modifications and improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for screening the self-discharge performance of a battery, characterized in that, include: The formed battery was subjected to the following stages of treatment in sequence: first temperature stage of rest, second temperature stage of rest, and third temperature stage of rest, and the performance data of the battery before and after each stage of treatment were obtained. Compare the battery performance data before and after each stage of processing. If the change in battery performance data before and after each stage of processing is within the corresponding preset range, then the battery is a qualified battery. The temperature in the first temperature range is higher than that in the third temperature range, and the temperature in the third temperature range is higher than that in the second temperature range.

2. The method for screening battery self-discharge performance according to claim 1, characterized in that, The first temperature range resting period includes placing the battery in an environment of 45-60°C for 12-48 hours.

3. The method for screening battery self-discharge performance according to claim 1, characterized in that, The second temperature range resting period includes placing the battery in an environment of 0-10℃ for 24-72 hours.

4. The method for screening battery self-discharge performance according to claim 1, characterized in that, The third temperature range resting period includes placing the battery in an environment of 20-30℃ for 8-12 hours.

5. The method for screening battery self-discharge performance according to claim 1, characterized in that, The battery performance data includes one or more of the following: open-circuit voltage, DC internal resistance, and self-heating temperature.

6. The method for screening battery self-discharge performance according to claim 5, characterized in that, The preset range for the change in open-circuit voltage before and after any stage of processing is 0-10mV; and / or, the preset range for the rate of change of DC internal resistance before and after any stage of processing is 0-5%; the preset range for the change in self-heating temperature before and after any stage of processing is 0-2℃.

7. The method for screening battery self-discharge performance according to claim 1, characterized in that, It also includes the provision that if any performance data of a battery at any stage exceeds the corresponding preset range, the battery is deemed unqualified and is eliminated.

8. A battery self-discharge performance screening device, characterized in that, The apparatus for performing the battery self-discharge performance screening method according to any one of claims 1 to 7 includes: The temperature control unit is used to provide and control the static environment of the first temperature range, the second temperature range and the third temperature range; The test unit, located in the temperature control unit, is used to acquire performance data of the battery sample before and after each stage of resting. The processing unit is communicatively connected to the testing unit and is used to receive performance data before and after each stage of processing, and compare the changes in battery performance data before and after each stage of processing with the corresponding preset range to determine whether the battery sample is qualified.