Rapid evaluation method and system for echelon reassembled battery

Abstract

According to the rapid evaluation method and system for the echelon reconstituted battery, the dynamic internal resistance change rate is accurately measured, and multi-parameter comprehensive evaluation such as the attenuation rate of the battery capacity and temperature monitoring is combined, so that the performance state of the echelon battery can be more accurately judged, misjudgment is reduced, and the evaluation accuracy is improved. And meanwhile, corresponding evaluation standards and grading systems can be established according to different types of batteries and application scenes, so that the method is suitable for evaluation of various echelon batteries, has relatively high adaptability and universality, and is beneficial to promoting reasonable application and industrial development of the echelon batteries in different fields.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a method and system for quickly evaluating second-life recombinant batteries, which are used to accurately evaluate the performance, health status and safety of second-life batteries. Background Art

[0002] With the rapid development of industries such as electric vehicles, a large number of lithium batteries still have a certain amount of residual capacity and performance after reaching the service life of their initial application, and can be used for cascade utilization. However, cascade utilization lithium batteries come from a wide range of sources, and they have experienced different charge and discharge cycles, operating temperatures, charge and discharge rates and other conditions during their early use, resulting in significant performance differences between individual batteries. The current existing battery performance evaluation methods are difficult to comprehensively, accurately and efficiently evaluate the performance of cascade utilization lithium batteries, and cannot effectively screen out batteries suitable for different cascade utilization scenarios, which limits the healthy development of the cascade utilization lithium battery industry.

[0003] Patent document CN106383316A discloses a method for evaluating the performance of lithium batteries for cascade utilization, which can be used for the cascade recycling and reuse of lithium batteries. First, the lithium battery performance test conditions are designed, that is, the test time is designed, the initial SOC state is determined, and the discharge interval time is designed; according to the designed test conditions, the health characteristic data of the lithium battery is extracted; then, the health state decision method based on the multi-health life model data fusion technology is used to estimate the SOH; finally, the cascade utilization range of the lithium battery is divided, but this method requires the use of a large model for evaluation, which is too complicated;

[0004] Patent document CN112526367A discloses a safety evaluation method and system for a second-life power battery, which tests the safety evaluation parameters of a second-life power battery after charging and discharging; determines the relationship between the safety evaluation parameters and the corresponding set thresholds; and obtains the safety evaluation results of the second-life power battery according to the determined relationship; the safety evaluation parameters are at least one of the following parameters: temperature rise during battery charging and discharging, battery capacity retention rate, and battery internal resistance growth rate. However, this method only considers the rate of change of resistance, but due to the complex working conditions of second-life batteries, only measuring the growth rate of the battery internal resistance cannot accurately reflect and grade the actual situation of the battery.

[0005] Therefore, designing a comprehensive, accurate and efficient method to evaluate the performance of second-life lithium batteries and effectively screen out batteries suitable for different second-life scenarios is the difficulty and pain point of the current industry. Summary of the invention

[0006] Generally, the battery is recycled when the capacity of the power battery pack is less than 80%. Therefore, the recycled batteries are batteries that have been used for a long time and under complex working conditions. This also causes that each single battery in the recycled battery may have great individual differences. Therefore, it is necessary to distinguish these single batteries in detail. Measuring the open circuit voltage of the battery through the OCV-SOC curve to obtain the SOC of the battery cannot truly reflect the state of the battery. Therefore, first of all, the battery is quickly classified through preliminary screening, and then combined with dynamic resistance, it can keenly capture the changes in the internal microstructure of the battery. Dynamic internal resistance measurement can indirectly reflect the changes in this microstructure by detecting changes in resistance. When the crystal structure of the electrode material is distorted, the conduction path of electrons and ions will be affected, resulting in an increase in internal resistance. Through real-time monitoring of the dynamic internal resistance, abnormal changes in the internal microstructure of the battery can be discovered in time, providing a microscopic basis for battery status assessment.

[0007] The purpose of the present invention is to provide a rapid evaluation method for second-hand lithium batteries, which can comprehensively, accurately and quickly evaluate the various performance indicators of second-hand lithium batteries, provide a reliable basis for their reasonable second-hand utilization, and improve the safety and economic benefits of second-hand lithium batteries.

[0008] In order to solve the above problems, the present invention provides a rapid evaluation method for cascade reorganization batteries, comprising the following steps:

[0009] S1, detect the open circuit voltage OCV of the lithium battery;

[0010] S2, according to the preset OCV-SOC curve, obtain the current SOC state of the lithium battery;

[0011] S3, if the initial SOC value is less than 80%, the dynamic internal resistance of the battery is measured to obtain the dynamic resistance change rate of the battery;

[0012] S4, if the initial SOC value is greater than 80%, use a pulse current to perform a short-time pulse discharge on the battery, obtain the actual battery capacity decay rate and record the temperature during the discharge process. When the actual capacity decay rate exceeds the threshold, execute step S3;

[0013] S5, establishment and classification of evaluation criteria to determine the suitability of batteries.

[0014] Furthermore, in S4, the specific steps for obtaining the actual battery capacity decay rate are to perform a short-time pulse discharge on the battery with a certain pulse current, and simultaneously record the voltage change curve during the discharge process; combining with the pre-established capacity-voltage relationship model, accurately obtain the actual discharge capacity Q1 of the battery, compare the actual discharge capacity Q1 with the battery nominal capacity Q0, and calculate the actual capacity decay rate of the battery by (Q0-Q1) / Q0×100%.

[0015] Furthermore, the battery is subjected to N short-time pulse charge and discharge, the actual capacity decay rate and battery temperature of each time are recorded, and the actual average capacity decay rate and average temperature of the N charge and discharge times are calculated.

[0016] Furthermore, in S4, the current of pulse charge and discharge is 0.5C, and the discharge time is 5 minutes; there is a rest period between each pulse charge and discharge.

[0017] Furthermore, the specific steps of step S3 are: first apply a constant current charging pulse current to the battery, and during the pulse current loading process, synchronously collect current and voltage data, and according to Ohm's law (R=U / I), for each collection moment, use the collected voltage and current values ​​to calculate the instantaneous internal resistance of the battery, select the internal resistance values ​​at two specific moments, denoted as R1 and R2 respectively, and calculate the dynamic internal resistance change rate by the formula ΔR=(R2-R1) / R1×100%.

[0018] Furthermore, the rate of change of the dynamic resistance may be measured multiple times, and the average value is taken as the final rate of change of the dynamic internal resistance.

[0019] Furthermore, in step S4, the threshold is a decay rate of 10%.

[0020] Further, step S5 specifically includes, characterized in that step S5 specifically includes, if the actual average capacity decay rate is less than 10%, and the average temperature does not exceed the threshold, then the battery is determined to be a primary battery; if the average value of the dynamic internal resistance change rate is less than 5%, the actual average capacity decay rate is greater than 10% and less than 20%, and the average temperature does not exceed the threshold, then the battery is determined to be a secondary battery; if the average value of the dynamic internal resistance change rate is less than 5%, and the actual average capacity decay rate is greater than 20%, and the average temperature does not exceed the threshold, then the battery is determined to be a tertiary battery; if the average value of the dynamic internal resistance change rate is between 5%-10% and the average temperature does not exceed the threshold, then it is determined to be a fourth-level battery, which requires further monitoring or use under specific conditions; if the average value of the dynamic internal resistance change rate is greater than 10%, or the average battery temperature exceeds the threshold, then it is determined to be a fifth-level battery, which is not recommended.

[0021] Further, the temperature threshold is 40° C.-50° C., and the specific temperature value is selected according to the type of battery.

[0022] The present invention also provides a rapid evaluation system for cascade reorganization batteries, comprising:

[0023] High-precision current source, used to output accurate pulse current signal;

[0024] High-precision voltmeter, used to measure the voltage across the battery in real time;

[0025] The data acquisition module collects the current value output by the current source and the voltage value measured by the voltmeter synchronously at a high-speed acquisition frequency;

[0026] Temperature acquisition module, used to measure the temperature of the battery in real time;

[0027] The control unit is used to control the entire measurement process, including setting measurement parameters, receiving and processing collected data, storing data, and communicating with external devices. It is also used to calculate the instantaneous internal resistance and dynamic internal resistance change rate of the battery based on the collected data, and to evaluate and grade the battery performance in combination with other parameters.

[0028] The beneficial effects of the present invention are:

[0029] By accurately measuring the dynamic internal resistance change rate and combining it with comprehensive evaluation of multiple parameters such as battery capacity attenuation rate and temperature monitoring, the performance status of the second-life battery can be judged more accurately, misjudgment can be reduced, and the accuracy of the evaluation can be improved. At the same time, corresponding evaluation standards and grading systems can be established according to different types of batteries and application scenarios. It is suitable for the evaluation of various second-life batteries, has strong adaptability and versatility, and helps promote the rational application and industrial development of second-life batteries in different fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic flow chart of the rapid evaluation method of the cascade utilization lithium battery of the present invention; DETAILED DESCRIPTION

[0031] To make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects will be described in further detail below in conjunction with specific implementation methods and accompanying drawings, but the implementation methods of the present invention are not limited thereto.

[0032] In the present invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple.

[0033] Generally, the battery is recycled when the capacity of the power battery pack is less than 80%. Therefore, the recycled batteries are batteries that have been used for a long time and under complex working conditions. This also causes that each single battery in the recycled battery may have great individual differences. Therefore, it is necessary to distinguish these single batteries in detail. Measuring the open circuit voltage of the battery through the OCV-SOC curve to obtain the SOC of the battery cannot truly reflect the state of the battery. Therefore, first of all, the battery is quickly classified through preliminary screening, and then combined with dynamic resistance, it can keenly capture the changes in the internal microstructure of the battery. Dynamic internal resistance measurement can indirectly reflect the changes in this microstructure by detecting changes in resistance. When the crystal structure of the electrode material is distorted, the conduction path of electrons and ions will be affected, resulting in an increase in internal resistance. Through real-time monitoring of the dynamic internal resistance, abnormal changes in the internal microstructure of the battery can be discovered in time, providing a microscopic basis for battery status assessment.

[0034] See also Figure 1 The present invention provides a rapid evaluation method for second-life lithium batteries, which specifically comprises the following steps:

[0035] S1, detect the open circuit voltage OCV of the lithium battery;

[0036] Use a high-precision voltmeter to measure the open circuit voltage (OCV) of the battery. Set the appropriate open circuit voltage range according to the battery type and application scenario. For example, when lithium-ion second-life batteries are used in energy storage systems, the open circuit voltage range is generally 3.0V-4.2V.

[0037] S2, according to the preset OCV-SOC curve, obtain the current SOC state of the lithium battery;

[0038] S3, if the initial SOC value is less than 80%, the dynamic internal resistance of the battery is measured to obtain the dynamic resistance change rate of the battery;

[0039] Measurement preparation: Connect the second-life battery to be evaluated to the dynamic internal resistance measurement system, ensuring that the connection is reliable and the contact resistance is extremely small. Before measuring, let the battery stand for a period of time (e.g. 30 minutes) to allow it to reach a stable state.

[0040] Pulse current loading and data acquisition: The pulse current loading scheme is set by the control unit. For example, a constant current charging pulse with a duration of 10 milliseconds is first applied. The current size is set according to the rated capacity of the battery (such as 0.2C, for a battery with a rated capacity of 50Ah, the current is 10A), and the pulse interval is 100 milliseconds. During the pulse current loading process, the data acquisition module synchronously collects current and voltage data.

[0041] Dynamic internal resistance calculation: According to Ohm's law (R = U / I), for each acquisition moment, the instantaneous internal resistance of the battery is calculated using the collected voltage and current values. In a pulse current loading cycle, the internal resistance values ​​at multiple different moments can be obtained to form a curve of internal resistance changing with time.

[0042] Calculation of dynamic internal resistance change rate: Select the internal resistance values ​​at two specific moments (such as 2 milliseconds and 8 milliseconds after the start of the pulse current), record them as R1 and R2 respectively, and calculate the dynamic internal resistance change rate by the formula (ΔR = (R2-R1) / R1×100%). In order to improve the accuracy, multiple measurements (such as 5 times) can be performed, and the average value is taken as the final dynamic internal resistance change rate.

[0043] S4, if the initial SOC value is greater than 80%, use pulse current to perform short-time pulse charge and discharge on the battery, obtain the actual battery capacity decay rate and record the temperature during the discharge process, and when the actual capacity decay rate exceeds the threshold, execute step S3;

[0044] The battery is pulse-discharged for a short time (such as 5 minutes) with a certain pulse current (such as 0.5C), and the voltage change curve during the discharge process is recorded. Combined with the pre-established capacity-voltage relationship model, the actual discharge capacity Q1 of the battery is accurately obtained, and the actual discharge capacity Q1 is compared with the nominal capacity Q0 of the battery, and the actual capacity decay rate of the battery is calculated by (Q0-Q1) / Q0×100%. During the battery measurement process, a high-precision temperature sensor is used to monitor the surface temperature of the battery in real time. Set a temperature threshold (such as 42°C). If the temperature exceeds the threshold during the measurement process, combined with the change trend of the dynamic internal resistance change rate, analyze whether the battery has heat dissipation problems or internal short circuit risks. Further, in order to improve the accuracy of the results, N short-term pulse charge and discharge can be performed, and the capacity decay rate and battery temperature of each time are recorded, and the actual average capacity decay rate and average temperature of N charge and discharge are calculated. If the actual decay rate of the battery calculated exceeds 10%, the battery is further subjected to dynamic resistance measurement to further evaluate the performance of the battery.

[0045] S5, establishment and classification of evaluation criteria to determine the suitability of batteries.

[0046] Based on a large amount of experimental data and practical application experience, a dynamic internal resistance change rate evaluation standard and grading system are established for different types of second-life batteries (such as lithium-ion batteries, lead-acid batteries, etc.) and application scenarios (such as energy storage systems, low-speed electric vehicles, etc.).

[0047] Specifically, if the actual average capacity decay rate is less than 10% and the average temperature does not exceed the threshold, the battery is judged to be a primary battery; if the average value of the dynamic internal resistance change rate is less than 5%, the actual average capacity decay rate is greater than 10% and less than 20%, and the average temperature does not exceed the threshold, the battery is judged to be a secondary battery; if the average value of the dynamic internal resistance change rate is less than 5%, and the actual average capacity decay rate is greater than 20%, and the average temperature does not exceed the threshold, the battery is judged to be a third-level battery; if the average value of the dynamic internal resistance change rate is between 5%-10% and the average temperature does not exceed the threshold, it is judged to be a fourth-level battery, which requires further monitoring or use under specific conditions; if the average value of the dynamic internal resistance change rate is greater than 10%, or the average battery temperature exceeds the threshold, it is judged to be a fifth-level battery, which is not recommended.

[0048] Further, the temperature threshold may be 40° C.-50° C., and the specific temperature value is selected according to the type of battery.

[0049] In order to further implement the above-mentioned rapid evaluation method for second-life lithium batteries, the present invention also provides a rapid evaluation system for second-life recombinant batteries, comprising:

[0050] High-precision current source, used to output accurate pulse current signal;

[0051] High-precision voltmeter, used to measure the voltage across the battery in real time;

[0052] The data acquisition module collects the current value output by the current source and the voltage value measured by the voltmeter synchronously at a high-speed acquisition frequency;

[0053] Temperature acquisition module, used to measure the temperature of the battery in real time;

[0054] The control unit is used to control the entire measurement process, including setting measurement parameters, receiving and processing collected data, storing data, and communicating with external devices. It is also used to calculate the instantaneous internal resistance and dynamic internal resistance change rate of the battery based on the collected data, and to evaluate and grade the battery performance in combination with other parameters.

[0055] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0056] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0057] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0058] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A rapid evaluation method for cascade recombinant batteries, characterized in that: The following steps are involved: S1, detect the open circuit voltage OCV of the lithium battery; S2, according to the preset OCV-SOC curve, obtain the current SOC state of the lithium battery; S3, if the initial SOC value is less than 80%, the dynamic internal resistance of the battery is measured to obtain the dynamic resistance change rate of the battery; S4, if the initial SOC value is greater than 80%, use a pulse current to perform a short-time pulse discharge on the battery, obtain the actual battery capacity decay rate and record the temperature during the discharge process. When the actual capacity decay rate exceeds the threshold, execute step S3; S5, establishment and classification of evaluation criteria to determine the suitability of batteries.

2. The rapid evaluation method for cascade recombinant batteries according to claim 1, characterized in that: In S4, the specific steps for obtaining the actual battery capacity decay rate are: performing a short-time pulse discharge on the battery with a certain pulse current, and recording the voltage change curve during the discharge process; combining with the pre-established capacity-voltage relationship model, accurately obtaining the actual discharge capacity Q1 of the battery, comparing the actual discharge capacity Q1 with the nominal capacity Q0 of the battery, and calculating the actual capacity decay rate of the battery by (Q0-Q1) / Q0×100%.

3. The rapid evaluation method for cascade reorganization batteries according to claim 2, characterized in that: Perform N short-time pulse charge and discharge on the battery, record the capacity decay rate and battery temperature each time, and calculate the actual average capacity decay rate and average temperature of N charge and discharge.

4. The rapid evaluation method for cascade reorganization batteries according to claim 1, characterized in that: In S4, the current of pulse charge and discharge is 0.5C, and the discharge time is 5 minutes; there is a rest period between each pulse charge and discharge.

5. The rapid evaluation method for cascade recombinant batteries according to claim 1, characterized in that: The specific steps in S3 are: first apply a constant current charging pulse current to the battery, and during the pulse current loading process, synchronously collect current and voltage data, and according to Ohm's law (R=U / I), for each collection moment, use the collected voltage and current values ​​to calculate the instantaneous internal resistance of the battery, select the internal resistance values ​​at two specific moments, denoted as R1 and R2 respectively, and calculate the dynamic internal resistance change rate by the formula ΔR=(R2-R1) / R1×100%.

6. The rapid evaluation method for cascade reorganization batteries according to claim 5, characterized in that: Multiple measurements can be performed and the average value can be taken as the final dynamic internal resistance change rate.

7. The rapid evaluation method for cascade recombinant batteries according to claim 1, characterized in that: In step S4, the threshold is a decay rate of 10%.

8. The rapid evaluation method for cascade recombinant batteries according to claim 1, characterized in that: Step S5 specifically includes, it is characterized in that step S5 specifically includes, if the actual average capacity decay rate is less than 10%, and the average temperature does not exceed the threshold, then the battery is determined to be a primary battery; if the average value of the dynamic internal resistance change rate is less than 5%, the actual average capacity decay rate is greater than 10% and less than 20%, and the average temperature does not exceed the threshold, then the battery is determined to be a secondary battery; if the average value of the dynamic internal resistance change rate is less than 5%, and the actual average capacity decay rate is greater than 20%, and the average temperature does not exceed the threshold, then the battery is determined to be a tertiary battery; if the average value of the dynamic internal resistance change rate is between 5%-10% and the average temperature does not exceed the threshold, further monitoring or use under specific conditions is required; if the average value of the dynamic internal resistance change rate is greater than 10%, or the average temperature of the battery exceeds the threshold, it is determined to be a fifth-level battery and is not recommended for use.

9. The rapid evaluation method for cascade recombinant batteries according to claim 8, characterized in that: The temperature threshold is 40°C-50°C.

10. A rapid evaluation system for recombinant batteries, characterized in that: include: High-precision current source, used to output accurate pulse current signal; High-precision voltmeter, used to measure the voltage across the battery in real time; The data acquisition module collects the current value output by the current source and the voltage value measured by the voltmeter synchronously at a high-speed acquisition frequency; Temperature acquisition module, used to measure the temperature of the battery in real time; The control unit is used to control the entire measurement process, including setting measurement parameters, receiving and processing collected data, storing data, and communicating with external devices. It is also used to calculate the instantaneous internal resistance and dynamic internal resistance change rate of the battery based on the collected data, and to evaluate and grade the battery performance in combination with other parameters.

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