A method for quickly grading and grouping lithium ion battery cells

Abstract

The application discloses a method for quickly grading and grouping lithium ion battery monomers, comprising the following steps: S1, performing limited-capacity charging formation on the battery monomers or performing limited-capacity constant-current discharging after formation; S2, collecting dynamic voltage of the battery monomers in the formation process and static voltage after aging treatment after the formation; S3, extracting a plurality of battery monomers, and performing constant-current discharging to a discharging cut-off voltage to obtain initial discharging capacity; S4, performing linear fitting on the dynamic voltage, the static voltage and the initial discharging capacity to obtain a fitting equation; and S5, substituting the dynamic voltage and the static voltage obtained in S2 into the fitting equation in S4 to obtain fitted initial discharging capacity and perform grading and grouping. The dynamic voltage in the formation process of the battery and the static voltage after aging are collected, the initial discharging capacity of the battery is fitted, and the lithium ion battery monomers are graded according to the fitted initial discharging capacity, so that the speed and efficiency of grading and grouping are improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing, and in particular to a method for rapidly separating and grouping lithium-ion battery cells. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles, electric bicycles, and energy storage due to their ultra-long cycle life, high specific energy, and excellent power performance. By connecting several battery cells in series, parallel, or series-parallel configurations, lithium-ion battery systems meet the power, capacity, and voltage requirements of electric vehicles, energy storage stations, and consumer electronics. Lithium-ion batteries pose safety hazards such as fire and explosion under extreme conditions like overcharging and over-discharging. Actual lithium-ion battery systems incorporate battery management systems to monitor parameters such as battery cell voltage and temperature, preventing overcharging and over-discharging. Therefore, the consistency of lithium-ion battery cells determines the cycle life, power, and actual discharge capacity of the battery system. To ensure the overall performance of the battery system, actual production involves classifying lithium-ion battery cells based on parameters such as capacity, internal resistance, and plateau voltage. Cells of the same class can be grouped and connected in series, parallel, or series-parallel configurations to form battery systems.

[0003] The "Method for Assembling Lithium Iron Phosphate Batteries" disclosed in Chinese patent literature, publication number CN108550893A, publication date 2018-09-18, includes: detecting the remaining power of battery boxes of lithium iron phosphate batteries; selecting a first battery box from the battery boxes with a remaining power of 5% to 30% of the initial power of the battery box; disassembling the first battery box into individual batteries to form a battery pack; selecting a first battery pack from the battery packs according to a first screening criterion; selecting a second battery pack from the first battery pack according to a second screening criterion; detecting the capacity of each individual battery in the second battery pack; selecting a third battery pack from the second battery pack according to a third screening criterion; subjecting the third battery pack to high-temperature static treatment and detecting the voltage drop of the open-circuit voltage of the individual batteries per unit time; selecting a fourth battery pack from the third battery pack according to a fourth screening criterion; and reassembling the fourth battery pack into a battery box. This technology involves testing each individual battery cell before grading and grouping them. However, in actual production, after the formation of a lithium-ion battery cell, it must undergo processes such as secondary sealing, aging, OCV, and grading to complete the grading of the battery cells. Especially in mass production, the grading process will occupy equipment, space, and capital, and increase labor and energy costs. On the other hand, testing each individual battery cell will also extend the battery production cycle, which is not conducive to improving production efficiency. Summary of the Invention

[0004] This invention aims to overcome the problems of low efficiency and high cost in existing methods for classifying and grouping lithium-ion battery cells. It provides a method for rapid classification and grouping of lithium-ion battery cells by collecting dynamic voltage during the battery formation process and static voltage after aging, fitting the initial discharge capacity of the battery, and using the fitted initial discharge capacity to classify lithium-ion battery cells, thereby improving the speed and efficiency of classification and grouping.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for rapidly grouping and assembling lithium-ion battery cells includes:

[0007] S1. Form the lithium-ion battery cells by performing staged variable current capacity-limited charging or constant current capacity-limited charging; or form the lithium-ion battery cells and then discharge them at a capacity-limited constant current.

[0008] S2. Collect the dynamic voltage V of a lithium-ion battery cell during the formation process and the static voltage OCV after aging treatment after formation.

[0009] S3. After fully charging a number of lithium-ion battery cells using a constant current and constant voltage method, let them stand for a certain period of time, and then discharge them at a constant current until the discharge cutoff voltage is reached to obtain the initial discharge capacity.

[0010] S4. Linearly fit the sampling data of dynamic voltage V and static voltage OCV with the initial discharge capacity to obtain the equation C=ax+by+d, where C represents the fitted initial discharge capacity data, x represents the dynamic voltage data, y represents the static voltage data, and a, b and d are constants.

[0011] S5. Substitute the dynamic voltage V and static voltage OCV obtained in S2 into the equation in S4 to obtain the fitted initial discharge capacity of the batch of lithium-ion battery cells, and then classify and group them according to the fitted initial discharge capacity.

[0012] In this invention, based on an ideal battery model, the relationship between the battery output voltage U and the power supply internal resistance R, battery electromotive force E, and output current I can be described by the equation U = ER * I. In actual production, the discharge capacity of a single battery cell is often measured using a constant current-limited voltage discharge method. The battery internal resistance R affects the battery output voltage, and thus the battery capacity. According to electrode dynamics, a large battery internal resistance is directly reflected in the following: under the same conditions, the larger the battery internal resistance, the larger the dynamic voltage during charging and the smaller the dynamic voltage during discharging. Therefore, it can be considered that there is a strong correlation between the dynamic voltage during charging or discharging and the battery discharge capacity. That is, when a certain capacity is charged or discharged, the battery discharge capacity is strongly correlated with the static voltage. Therefore, it can be simply considered that C = f(x,y), where C is the discharge capacity of a single battery cell, x is the dynamic voltage, and y is the static voltage. After differentiation, an approximate linear fitting equation C = ax + by + d is obtained. The fitted initial discharge capacity is obtained using the actually measured dynamic voltage and static voltage to classify and group lithium-ion batteries.

[0013] Preferably, S2 includes two acquisition methods for dynamic voltage V and static voltage OCV:

[0014] The first method involves collecting the dynamic voltage V1 when a certain capacity is charged into a single lithium-ion battery cell during the charging and formation process, and the static voltage OCV1 after aging at room temperature.

[0015] The second method involves collecting the dynamic voltage V2 when a lithium-ion battery cell is discharged to a certain capacity during the constant current discharge process after charging and formation, and the static voltage OCV2 after high-temperature aging.

[0016] In this invention, the material system of the lithium-ion battery cell can be selected from one of the following systems: lithium iron phosphate-graphite, ternary-graphite, lithium manganese oxide-graphite, ternary composite-graphite, lithium manganese oxide composite-graphite, lithium-rich manganese-graphite, lithium manganese iron phosphate-graphite, ternary-lithium titanate, lithium manganese oxide-lithium titanate, ternary composite-lithium titanate, lithium-rich manganese-lithium titanate, lithium manganese iron phosphate-lithium titanate, and lithium manganese oxide composite-lithium titanate.

[0017] Preferably, in step S1, when the lithium-ion battery cell undergoes staged variable current limited capacity charging or constant current limited capacity charging, the charging capacity range is 0.3*Cr-1.0*Cr, and the charging current range is 0.05*Cr(A)-1.0*Cr(A); where Cr and Cr(A) are the rated capacity and rated current of the lithium-ion battery cell, respectively. In step S1, after the lithium-ion battery cell is formed, during limited capacity constant current discharge, the discharge capacity range is 0.05*Cr-0.95*Cr, and the discharge current range is 0.1*Cr(A)-2.0*Cr(A).

[0018] The formation method of the lithium-ion battery in this invention is selected to adapt to the dynamic voltage acquisition method. When the input voltage of the battery cell during the formation process is selected as the dynamic voltage, the formation is carried out by staged variable current limited capacity charging or constant current limited capacity charging. When the output voltage of the battery cell after formation is selected as the dynamic voltage, the formation is carried out by limited capacity constant current discharge.

[0019] Preferably, the dynamic voltage V1 is the input voltage of a single battery cell when a certain capacity is charged during the charging formation process, with a charging capacity range of 0.3*Cr-1.0*Cr and a charging current range of 0.05*Cr(A)-1.0*Cr(A); the dynamic voltage V2 is the output voltage of a single battery cell when a certain capacity is discharged during the constant current discharge process after charging formation, with a discharge capacity range of 0.05*Cr-0.95*Cr and a discharge current range of 0.1*Cr(A)-2.0*Cr(A). The dynamic voltage in this invention is most suitable for acquisition during limited-capacity constant current charging or discharging processes, thus avoiding the voltage range required for the formation of the SEI solid electrolyte interface film.

[0020] Preferably, the static voltage OCV1 is the open-circuit voltage of a lithium-ion battery cell after room-temperature aging, with an aging time of 36-144 hours and a temperature of 25±3℃; the static voltage OCV2 is the open-circuit voltage of a lithium-ion battery cell after high-temperature aging, with an aging time of 24-96 hours and a temperature of 45±3℃. The aging time and temperature settings in this invention are to eliminate the influence of relaxation effects on the static voltage. Simultaneously, the relative humidity of the environment needs to be maintained at least 70% during both room-temperature and high-temperature aging processes.

[0021] Preferably, in the method of obtaining the initial discharge capacity of the S3 lithium-ion battery cell, the constant current and constant voltage charging current range is 0.2*Cr(A)-1.0*Cr(A), and the constant current discharge current range is 0.5*Cr(A)-2.0*Cr(A).

[0022] In this invention, in order to calculate the values ​​of the three constants a, b, and d in the fitting equation C = ax + by + d, 100 to 500 lithium-ion battery cells from the same production batch can be selected as samples, fully charged in a constant current and constant voltage manner, and then left to stand for 10 to 30 minutes. After that, they are discharged at a constant current until the discharge cutoff voltage is obtained to obtain the initial discharge capacity of the lithium-ion battery cells. The fitting equation of the batch of lithium-ion battery cells is obtained by fitting the data of these extracted lithium-ion battery cells.

[0023] Preferably, in step S5, after acquiring dynamic voltage sampling data and static voltage sampling data for a lithium-ion battery cell, the fitted initial discharge capacity of the lithium-ion battery cell is obtained by substituting them into the equation C=ax+by+d. Based on the fitted initial discharge capacity, the lithium-ion battery cells are classified into grades with a fixed gradient, and the gradient range is selected as any value in 0.005*Cr-0.02*Cr.

[0024] In this invention, the initial discharge capacity of lithium-ion battery cells in actual mass production fluctuates randomly within a very small range. That is, when a certain capacity is charged or discharged, the dynamic voltage and static voltage of the lithium-ion battery change within a very small range. Therefore, by substituting the dynamic voltage and static voltage data of the lithium-ion battery cells that were not sampled in the same batch into the fitting equation, the fitted initial discharge capacity of the remaining lithium-ion battery cells can be obtained. Based on the fitted initial discharge capacity, the lithium-ion battery cells are classified by capacity, and lithium-ion battery cells of the same category are grouped together.

[0025] The present invention has the following advantages: by collecting the dynamic voltage during the battery formation process and the static voltage after aging, the initial discharge capacity of the battery is fitted, and the lithium-ion battery cells are classified according to the fitted initial discharge capacity, thereby improving the speed and efficiency of capacity classification and grouping; when detecting dynamic voltage or static voltage, only a certain capacity of charging or discharging is needed to obtain the result, which takes less time than detecting the capacity of the entire battery cell, and the detection method is simpler. Attached Figure Description

[0026] Figure 1 This is a flowchart of the capacity allocation method of the present invention;

[0027] Figure 2 This is a residual distribution diagram of the fitted linear equation in Embodiment 1 of the present invention;

[0028] Figure 3 This is a residual distribution diagram of the fitted linear equation in Embodiment 2 of the present invention. Detailed Implementation

[0029] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0030] like Figure 1 As shown, a method for rapidly grouping and assembling lithium-ion battery cells includes:

[0031] S1. Form the lithium-ion battery cells using a staged variable current capacity-limited charging or constant current capacity-limited charging method; or form the lithium-ion battery cells and then discharge them at a capacity-limited constant current. In S1, when forming the lithium-ion battery cells using a staged variable current capacity-limited charging or constant current capacity-limited charging method, the charging capacity range is 0.3*Cr-1.0*Cr, and the charging current range is 0.05*Cr(A)-1.0*Cr(A); where Cr and Cr(A) are the rated capacity and rated current of the lithium-ion battery cell, respectively. When the lithium-ion battery cells are formed and then discharged at a capacity-limited constant current, the discharge capacity range is 0.05*Cr-0.95*Cr, and the discharge current range is 0.1*Cr(A)-2.0*Cr(A).

[0032] S2 collects the dynamic voltage V of a lithium-ion battery cell during the formation process and the static voltage OCV after aging treatment following formation; S2 includes two methods for collecting the dynamic voltage V and the static voltage OCV:

[0033] The first method involves collecting the dynamic voltage V1 when a certain capacity is charged into a single lithium-ion battery cell during the charging and formation process, and the static voltage OCV1 after aging at room temperature.

[0034] The second method involves collecting the dynamic voltage V2 when a lithium-ion battery cell is discharged to a certain capacity during the constant current discharge process after charging and formation, and the static voltage OCV2 after high-temperature aging.

[0035] Dynamic voltage V1 is the input voltage of a single battery cell when it is charged to a certain capacity during the charging and formation process. The charging capacity range is 0.3*Cr-1.0*Cr, and the charging current range is 0.05*Cr(A)-1.0*Cr(A). Dynamic voltage V2 is the output voltage of a single battery cell when it is discharged to a certain capacity during the constant current discharge process after charging and formation. The discharge capacity range is 0.05*Cr-0.95*Cr, and the discharge current range is 0.1*Cr(A)-2.0*Cr(A).

[0036] The static voltage OCV1 is the open-circuit voltage of a lithium-ion battery cell after aging at room temperature, with an aging time of 36h-144h and a temperature of 25±3℃; the static voltage OCV2 is the open-circuit voltage of a lithium-ion battery cell after aging at high temperature, with an aging time of 24h-96h and a temperature of 45±3℃.

[0037] S3. After fully charging a number of lithium-ion battery cells using a constant current and constant voltage method, let them stand for a certain period of time, and then discharge them at a constant current until the discharge cutoff voltage is reached to obtain the initial discharge capacity. In the method of obtaining the initial discharge capacity of lithium-ion battery cells, the constant current and constant voltage charging current range is 0.2*Cr(A)-1.0*Cr(A), and the constant current discharging current range is 0.5*Cr(A)-2.0*Cr(A).

[0038] S4. Linearly fit the collected data of dynamic voltage V and static voltage OCV with the initial discharge capacity to obtain the equation C = ax + by + d, where C represents the fitted initial discharge capacity data, x represents the dynamic voltage data, y represents the static voltage data, and a, b, and d are constants. For the several lithium-ion battery cells sampled in S3, number them, and then, based on the least squares method, the constants in the fitting equation C = ax + by + d can be obtained using the following formula:

[0039]

[0040]

[0041]

[0042] Where n is the total number of samples taken, i represents the sample battery cell number, and x i y i C i These are the three data points for the i-th sample battery: dynamic voltage, static voltage, and initial discharge capacity.

[0043] S5. Substitute the dynamic voltage V and static voltage OCV sampling data obtained in S2 into the equation in S4 to obtain the fitted initial discharge capacity of the batch of lithium-ion battery cells. Then, classify and group them according to the fitted initial discharge capacity. In S5, after obtaining the dynamic voltage sampling data and static voltage sampling data of the lithium-ion battery cells, substitute them into the equation C=ax+by+d to obtain the fitted initial discharge capacity of the lithium-ion battery cells. According to the fitted initial discharge capacity, classify the lithium-ion battery cells with a fixed gradient. The gradient range is selected as any value in 0.005*Cr-0.02*Cr.

[0044] If the production process and battery material system remain unchanged, steps S3 and S4 can be omitted in subsequent mass production. That is, the dynamic voltage V1 or V2 and static voltage OCV1 or OCV2 of the battery cell can be directly substituted into the obtained binary linear equation to fit the initial discharge capacity.

[0045] In this invention, based on an ideal battery model, the relationship between the battery output voltage U and the power supply internal resistance R, battery electromotive force E, and output current I can be described by the equation U = ER * I. In actual production, the discharge capacity of a single battery cell is often measured using a constant current-limited voltage discharge method. The battery internal resistance R affects the battery output voltage, and thus the battery capacity. According to electrode dynamics, a large battery internal resistance is directly reflected in the following: under the same conditions, the larger the battery internal resistance, the larger the dynamic voltage during charging and the smaller the dynamic voltage during discharging. Therefore, it can be considered that there is a strong correlation between the dynamic voltage during charging or discharging and the battery discharge capacity. That is, when a certain capacity is charged or discharged, the battery discharge capacity is strongly correlated with the static voltage. Therefore, it can be simply considered that C = f(x,y), where C is the discharge capacity of a single battery cell, x is the dynamic voltage, and y is the static voltage. After differentiation, an approximate linear fitting equation C = ax + by + d is obtained. The fitted initial discharge capacity is obtained using the actually measured dynamic voltage and static voltage to classify and group lithium-ion batteries.

[0046] In this invention, the material system of the lithium-ion battery cell can be selected from one of the following systems: lithium iron phosphate-graphite, ternary-graphite, lithium manganese oxide-graphite, ternary composite-graphite, lithium manganese oxide composite-graphite, lithium-rich manganese-graphite, lithium manganese iron phosphate-graphite, ternary-lithium titanate, lithium manganese oxide-lithium titanate, ternary composite-lithium titanate, lithium-rich manganese-lithium titanate, lithium manganese iron phosphate-lithium titanate, and lithium manganese oxide composite-lithium titanate.

[0047] The formation method of the lithium-ion battery in this invention is selected to adapt to the dynamic voltage acquisition method. When the input voltage of the battery cell during the formation process is selected as the dynamic voltage, the formation is carried out by staged variable current limited capacity charging or constant current limited capacity charging. When the output voltage of the battery cell after formation is selected as the dynamic voltage, the formation is carried out by limited capacity constant current discharge.

[0048] The dynamic voltage in this invention is most suitable for acquisition during limited-capacity constant-current charging or discharging processes, in order to avoid the voltage range for the formation of the SEI solid electrolyte interface film. The aging time and temperature settings in this invention are to eliminate the influence of relaxation effects on the static voltage, while maintaining a relative humidity of less than or equal to 70% during both room-temperature and high-temperature aging processes.

[0049] In this invention, in order to calculate the values ​​of the three constants a, b, and d in the fitting equation C = ax + by + d, 100 to 500 lithium-ion battery cells from the same production batch can be selected as samples, fully charged in a constant current and constant voltage manner, and then left to stand for 10-30 minutes. After that, they are discharged at a constant current until the discharge cutoff voltage is obtained to obtain the initial discharge capacity of the lithium-ion battery cells. The fitting equation of the batch of lithium-ion battery cells is obtained by fitting the data of these extracted lithium-ion battery cells.

[0050] In this invention, the initial discharge capacity of lithium-ion battery cells in actual mass production fluctuates randomly within a very small range. That is, when a certain capacity is charged or discharged, the dynamic voltage and static voltage of the lithium-ion battery change within a very small range. Therefore, by substituting the dynamic voltage and static voltage data of the lithium-ion battery cells that were not sampled in the same batch into the fitting equation, the fitted initial discharge capacity of the remaining lithium-ion battery cells can be obtained. Based on the fitted initial discharge capacity, the lithium-ion battery cells are classified by capacity, and lithium-ion battery cells of the same category are grouped together.

[0051] In the embodiments of the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. Unless otherwise specified, the methods in the embodiments are conventional methods in the art.

[0052] Example 1:

[0053] 1. Formation of 12000mAh soft-pack lithium-ion battery cells using lithium manganese oxide-graphite: After liquid injection and aging, batches of lithium-ion battery cells are subjected to pressure formation. The formation process parameters are as follows:

[0054]

[0055] 2. By using a pressurized formation device to collect data, the dynamic voltage x after the completion of constant current charging in step 2 is acquired. i ;

[0056] 3. The formed lithium-ion battery cells are aged at room temperature for 36-144 hours. In this embodiment, 36 hours of aging is preferred. The steady-state voltage is then measured and recorded as the static voltage y. i ;

[0057] 4. Take 100 lithium-ion battery cells aged at room temperature as samples for normal capacity testing. The capacity testing parameters are as follows. The actual initial discharge capacity of the battery after the fourth step of constant current discharge is taken and denoted as C. i ;

[0058]

[0059] 5. Transfer the collected data (x) i ,y i C i Substituting the constants into the constants of the fitted equation C = ax + by + d, we obtain the bivariate linear equation C = -1.7822x - 7.3837y + 49082.85. From this bivariate linear equation, we calculate the fitted initial discharge capacity of the sample battery cell and then calculate the residual: actual initial discharge capacity - fitted initial discharge capacity. The residual distribution is as follows: Figure 2 As shown, the relative fitting error is ≤0.7%.

[0060] 6. Measure the dynamic and steady-state voltages of the remaining unsampled battery cells from the same batch. Substitute these values ​​into the binary linear equation C = -1.7822x - 7.3837y + 49082.85 to obtain the fitted initial discharge capacity for each battery cell. Then, classify the cells according to capacity gradient sorting criteria. After normal mass production, since the cell system and rated capacity of the battery cells remain unchanged, the process of sampling battery cells and calculating the binary linear equation can be omitted. Perform a uniform fixed formation process on the batch of battery cells to obtain the dynamic voltage. After aging, measure the static voltage of the battery cells and substitute it into the already calculated binary linear equation to obtain the fitted initial discharge capacity of the battery cells. Then, classify the cells according to capacity sorting criteria. Battery cells of the same grade can be grouped to form battery systems.

[0061] Example 2:

[0062] 1. Formation of 20000mAh soft-pack lithium-ion battery cells using lithium manganese oxide-graphite: After liquid injection and aging, batches of lithium-ion battery cells are subjected to pressure formation. The formation process parameters are as follows:

[0063]

[0064] 2. Data was collected using a pressurized formation device, specifically the dynamic voltage x at the end of the 8th step discharge. i ;

[0065] 3. The formed lithium-ion battery cells are aged at 45°C for 24-96 hours. In this embodiment, it is preferred to age them at 45°C for 24 hours and then measure their steady-state voltage, which is recorded as the static voltage y. i ;

[0066] 4. Take 100 lithium-ion battery cells that have undergone high-temperature aging as samples for normal capacity testing. The capacity testing parameters are as follows. The actual initial discharge capacity of the battery after the fourth step of constant current discharge is taken and denoted as C. i ;

[0067]

[0068] 5. Transfer the collected data (x) i ,y i C i Substituting the constants into the constants in the fitting equation C = ax + by + d, we obtain the bivariate linear equation C = 0.8113x - 1.7689y + 25089.97. From this bivariate linear equation, we calculate the fitted initial discharge capacity of the sample battery cell and then calculate the residual: actual initial discharge capacity - fitted initial discharge capacity. The residual distribution is as follows: Figure 3 As shown, the relative fitting error is ≤1%.

[0069] 6. Measure the dynamic and steady-state voltages of the remaining unsampled battery cells from the same batch. Substitute these values ​​into the binary linear equation C = 0.8113x - 1.7689y + 25089.97 to obtain the fitted initial discharge capacity for each battery cell. Then, classify the cells according to capacity gradient sorting criteria. After normal mass production, since the cell system and rated capacity of the battery cells remain unchanged, the process of sampling battery cells and calculating the binary linear equation can be omitted. Perform a uniform fixed formation process on the batch of battery cells to obtain the dynamic voltage. After aging, measure the static voltage of the battery cells and substitute it into the already calculated binary linear equation to obtain the fitted initial discharge capacity of the battery cells. Then, classify the cells according to capacity sorting criteria, and battery cells of the same grade can be grouped to form battery systems.

[0070] As can be seen from the above embodiments, the capacity-based grouping method of the present invention can quickly, efficiently, and accurately group battery cells.

[0071] The above embodiments are further elaborations and descriptions of the present invention to facilitate understanding, and are not intended to limit the present invention in any way. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for rapidly grouping and assembling lithium-ion battery cells, characterized in that, include: S1. Forming lithium-ion battery cells by staged variable current limited capacity charging or constant current limited capacity charging. Alternatively, lithium-ion battery cells can be converted into a single unit and then discharged at a constant current with a limited capacity. S2. Collect the dynamic voltage V of a lithium-ion battery cell during the formation process and the static voltage OCV after aging treatment; including: collecting the dynamic voltage V1 when a lithium-ion battery cell is charged to a certain capacity during the charging and formation process and the static voltage OCV1 after aging at room temperature; or The dynamic voltage V2 of a lithium-ion battery cell after charging and formation was collected when it was discharged to a certain capacity during the constant current discharge process and the static voltage OCV2 after high-temperature aging. S3. After fully charging a number of lithium-ion battery cells using a constant current and constant voltage method, let them stand for a certain period of time, and then discharge them at a constant current until the discharge cutoff voltage is reached to obtain the initial discharge capacity. S4. Linearly fit the sampling data of dynamic voltage V and static voltage OCV with the initial discharge capacity to obtain the equation C=ax+by+d, where C represents the fitted initial discharge capacity data, x represents the dynamic voltage data, y represents the static voltage data, and a, b and d are constants. S5. Substitute the dynamic voltage V and static voltage OCV obtained in S2 into the equation in S4 to obtain the fitted initial discharge capacity of the batch of lithium-ion battery cells, and then classify and group them according to the fitted initial discharge capacity.

2. The method for rapid capacity allocation and grouping of lithium-ion battery cells according to claim 1, characterized in that, In S1, when a lithium-ion battery cell is formed using a staged variable current-limited capacity charging or constant current-limited capacity charging method, the charging capacity range is 0.3*Cr-1.0*Cr, and the charging current range is 0.05*Cr(A)-1.0*Cr(A); where Cr and Cr(A) are the rated capacity and rated current of the lithium-ion battery cell, respectively.

3. The method for rapid capacity allocation and grouping of lithium-ion battery cells according to claim 1, characterized in that, In S1, when the lithium-ion battery cell is formed and discharged under limited capacity constant current, the discharge capacity range is 0.05*Cr-0.95*Cr, and the discharge current range is 0.1*Cr(A)-2.0*Cr(A), where Cr and Cr(A) are the rated capacity and rated current of the lithium-ion battery cell, respectively.

4. The method for rapid capacity allocation and grouping of lithium-ion battery cells according to claim 1, characterized in that, Dynamic voltage V1 is the input voltage of a single battery cell when it is charged to a certain capacity during the charging and formation process. The charging capacity range is 0.3*Cr-1.0*Cr, and the charging current range is 0.05*Cr(A)-1.0*Cr(A). Dynamic voltage V2 is the output voltage of a single battery cell when it is discharged to a certain capacity during the constant current discharge process after charging and formation. The discharge capacity range is 0.05*Cr-0.95*Cr, and the discharge current range is 0.1*Cr(A)-2.0*Cr(A), where Cr and Cr(A) are the rated capacity and rated current of the lithium-ion battery cell, respectively.

5. A method for rapid capacity allocation and grouping of lithium-ion battery cells according to claim 1 or 4, characterized in that, The static voltage OCV1 is the open-circuit voltage of a lithium-ion battery cell after aging at room temperature, with an aging time of 36h-144h and a temperature of 25±3℃; the static voltage OCV2 is the open-circuit voltage of a lithium-ion battery cell after aging at high temperature, with an aging time of 24h-96h and a temperature of 45±3℃.

6. A method for rapid capacity allocation and grouping of lithium-ion battery cells according to claim 1, characterized in that, In the method for obtaining the initial discharge capacity of the S3 lithium-ion battery cell, the constant current and constant voltage charging current range is 0.2*Cr(A)-1.0*Cr(A), and the constant current discharge current range is 0.5*Cr(A)-2.0*Cr(A), where Cr and Cr(A) are the rated capacity and rated current of the lithium-ion battery cell, respectively.

7. A method for rapid capacity allocation and grouping of lithium-ion battery cells according to claim 1, 4, or 6, characterized in that, In step S5, after acquiring dynamic voltage sampling data and static voltage sampling data for a lithium-ion battery cell, the fitted initial discharge capacity of the lithium-ion battery cell is obtained by substituting them into the equation C=ax+by+d. Based on the fitted initial discharge capacity, the lithium-ion battery cells are classified into grades with a fixed gradient. The gradient range is selected as any value in the range of 0.005*Cr-0.02*Cr, where Cr and Cr(A) are the rated capacity and rated current of the lithium-ion battery cell, respectively.

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