Lithium ion battery self-discharge screening method, electronic equipment and storage medium

Abstract

The invention discloses a lithium ion battery self-discharge screening method. The method comprises the following specific steps: S1, carrying out capacity grading on a certain batch of formed or pre-charged battery cells; s2, standing the battery cell treated in the step S1 for a period of time T; s3, adjusting the load of the battery cell after standing in the step S2; s4, the maximum current Imax of constant-voltage charging of each battery cell processed in the step S3 is collected in sequence; and S5, if the maximum current Imax of the battery cell acquired in the step S4 meets the condition that Imax is greater than or equal to u-3sigma and less than or equal to u + 3sigma, judging that the self-discharge of the battery cell is qualified, and otherwise, judging that the self-discharge of the battery cell is unqualified. The method has the following beneficial effects: (1) OCV equipment is reduced, the influence of measurement system difference on the OCV is reduced, and the screening accuracy of self-discharge is facilitated; (2) the off-line period of the battery cell is shortened; and (3) the applicability is high, and the application range is wide.

Description

Technical Field

[0001] The invention belongs to the field of lithium ion batteries, and in particular relates to a lithium ion battery self-discharge screening method, electronic equipment and storage medium. Background Art

[0002] Lithium-ion battery is a secondary battery (rechargeable battery) that mainly relies on the movement of lithium ions between the positive and negative electrodes to work. + Insertion and deinsertion back and forth between the two electrodes: During charging, Li + The electrolyte is then embedded into the negative electrode, which is then in a lithium-rich state. The opposite is true during discharge. Currently, lithium-ion batteries have broad prospects in the fields of new energy vehicles, mobile base stations, and energy storage power stations.

[0003] In this case, lithium-ion batteries are more likely to appear in the form of battery packs connected in series or in parallel. The capacity and life of a lithium-ion battery pack are not only related to each individual battery, but also closely related to the consistency between each battery.

[0004] Lithium-ion battery self-discharge refers to the battery's self-discharge when it is not connected to an external circuit. This is due to chemical reactions occurring inside the battery. The main causes of self-discharge include electrolyte decomposition, micro-short circuits, temperature effects, etc. The self-discharge rate of lithium-ion batteries is relatively low, usually losing 0.5% to 3% of power per month, but this varies with changes in ambient temperature and storage conditions.

[0005] Self-discharge has a certain impact on the life of lithium-ion batteries. High temperatures will accelerate the self-discharge process because high temperatures can cause electrolyte decomposition and degradation of electrode materials. In addition, micro-short circuits and increased activity of the electrolyte can also aggravate self-discharge.

[0006] The consistency of lithium-ion battery self-discharge is an important part that affects capacity and life. After a period of storage, lithium-ion batteries with inconsistent self-discharge will have a large difference in SOC (the state of charge of the battery, that is, the ratio of the remaining power or available capacity of the battery to its capacity in the fully charged state), which will greatly affect the capacity and safety of the lithium-ion battery. Therefore, research on lithium-ion battery self-discharge screening will help improve the overall level of lithium-ion battery packs, enable lithium-ion battery packs to obtain a longer service life, and reduce the defective rate of products.

[0007] At present, most lithium-ion battery manufacturers use the voltage drop over a period of time to characterize the quality of lithium-ion battery self-discharge. The process is as follows: Figure 1 As shown. The capacity decay over a period of time can also be used to characterize the quality of lithium-ion battery self-discharge, or the two methods can be combined and used simultaneously for self-discharge screening.

[0008] However, the above-mentioned technical solution for characterizing the quality of lithium-ion battery self-discharge has the following shortcomings:

[0009] 1. Currently, the self-discharge screening by voltage drop method requires the battery cell to stand at high temperature or room temperature for a period of time, and detect the OCV before and after standing. This requires good temperature consistency when measuring OCV twice, otherwise the temperature will affect the measurement of lithium battery OCV. On the other hand, the longer the standing time, the easier it is to screen out abnormal self-discharge cells, so manufacturers need to choose between standing time and production capacity. Often, the self-discharge cells screened by the voltage drop method on the mass production line are missed or over-killed.

[0010] 2. Since the capacity is greatly affected by temperature, using the capacity decay over a period of time to characterize the quality of lithium-ion battery self-discharge cannot accurately screen out abnormal self-discharge cells. Summary of the invention

[0011] Purpose of the invention: The present invention makes improvements to the problems existing in the above-mentioned prior art, that is, the present invention discloses a self-discharge screening method for lithium-ion batteries, an electronic device and a storage medium. The present invention adopts the maximum current value of constant voltage charging to characterize the self-discharge of the battery cell (hereinafter referred to as the maximum current method), cancels the two OCV measurements of the voltage drop method, reduces the OCV process and measurement equipment, and shortens the battery cell offline cycle. At the same time, the maximum current method screens self-discharge, and compared with the voltage drop method for screening self-discharge, the test process is greatly simplified, the error of the measurement system is reduced, and the self-discharge of the battery cell can be measured more accurately. Compared with the capacity decay method, the maximum current method is less affected by the ambient temperature, which solves the problem that the capacity decay method is greatly affected by temperature.

[0012] The method for self-discharge screening of lithium-ion batteries includes charging the battery cells to the voltage V1 and then letting them stand. The voltage will decay during the standing process. After standing, the battery cells will perform a charge adjustment process. The charge adjustment process starts with constant voltage charging to make the battery cell voltage reach V3. Depending on the degree of voltage decay during the standing process of the battery cells, the current I that causes the constant voltage charging to reach V3 will be max Different, to carry out self-discharge screening, can accurately detect abnormal self-discharge cells.

[0013] Technical solution: A lithium-ion battery self-discharge screening method, the specific steps are as follows:

[0014] S1. Capacity division of a batch of formed or pre-charged cells, where:

[0015] The final voltage of the cell after capacity division is V1;

[0016] S2, leaving the battery cell treated in step S1 to stand for a period of time T to eliminate polarization of the battery cell;

[0017] S3, adjusting the charge of the battery cell after being left to stand in step S2:

[0018] S31, collecting the open circuit voltage V2 of the battery cell processed in step S2 at the beginning of the charge adjustment process;

[0019] S32, the first charge and discharge step of the load adjustment process must be a constant voltage charging step. At the same time, the constant voltage charging step must keep the voltage unchanged after the cell voltage is charged to V3, and the cell current begins to gradually decrease to the set value I 设定 Then end this step;

[0020] S4, sequentially collecting the maximum current I of the constant voltage charging of each battery cell processed in step S3 max ;

[0021] S5. If the maximum current I of the battery cell collected in step S4 max Meets u-3σ≤I max ≤u+3σ, the self-discharge of the battery cell is judged to be qualified, otherwise the self-discharge of the battery cell is unqualified, wherein:

[0022] u is the maximum current I of the batch of cells for constant voltage charging max The mean of

[0023] σ is the maximum current I of the batch of cells for constant voltage charging max The standard deviation of .

[0024] Furthermore, in step S1, the process step must be terminated at the voltage V1 of the battery cell.

[0025] Furthermore, if the battery cell is a lithium iron phosphate battery cell, the voltage V1 in step S1 ranges from 3.0 to 3.65 volts;

[0026] If the battery cell is a ternary battery cell, the voltage V1 in step S1 ranges from 3.0 to 4.2 volts.

[0027] Furthermore, the range of the standing time T in step S2 is T≥720 minutes.

[0028] Further, if the battery cell is a lithium iron phosphate battery cell, the voltage V3 in step S3 ranges from 3.0 to 3.65 volts;

[0029] If the battery cell is a ternary battery cell, the voltage V3 in step S3 is in the range of 3.0 to 4.2 volts.

[0030] Furthermore, the setting value I of the battery cell in step S3 is 设定 It is 0.05C ampere.

[0031] Furthermore, V2<V3≤V1.

[0032] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, any of the above-mentioned lithium-ion battery self-discharge screening methods is implemented.

[0033] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements any of the above-mentioned lithium-ion battery self-discharge screening methods.

[0034] Beneficial effects: The lithium-ion battery self-discharge screening method, electronic device and storage medium disclosed in the present invention have the following beneficial effects:

[0035] (1) The two OCV measurements are cancelled, the OCV equipment is reduced, and the impact of measurement system differences on OCV is reduced, which is beneficial to the accuracy of self-discharge screening;

[0036] (2) Changing from two static placements to one static placement reduces the number of static storage spaces and shortens the battery cell offline cycle;

[0037] (3) The present invention does not require the addition of any equipment or modification of the production line, and has strong applicability and a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Flowchart of the voltage drop method process to characterize the quality of lithium-ion battery self-discharge.

[0039] Figure 2 The present invention discloses a flow chart of a lithium-ion battery self-discharge screening method.

[0040] Figure 3 This is the current and voltage curve of the charge regulation constant voltage charging process.

[0041] Figure 4 For I max Schematic diagram of data recording.

[0042] Figure 5 is the voltage difference ΔV and I max Schematic diagram of the relationship curve. DETAILED DESCRIPTION

[0043] The specific embodiments of the present invention are described in detail below.

[0044] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10 to 50 is listed for a specific parameter, it is understood that the range of 10 to 40 and 20 to 50 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise specified, the range of values ​​"a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the range of values ​​"0 to 5" means that all real numbers between "0 to 5" have been fully listed in this article, and "0 to 5" is only an abbreviation of these numerical combinations.

[0045] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0046] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0047] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0048] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0049] Unless otherwise specified, the reaction is carried out at room temperature and pressure.

[0050] Unless otherwise specified, all parts or percentages are by weight.

[0051] In the present invention, all substances used are known substances and can be purchased or synthesized by known methods.

[0052] In the present invention, the devices or equipment used are all conventional devices or equipment known in the art and are commercially available.

[0053] Example 1

[0054] Taking lithium iron phosphate battery as an example, a self-discharge screening method for lithium-ion batteries has the following specific steps:

[0055] S1. Capacity division of a batch of formed cells, including:

[0056] The final voltage of the cell after capacity division is V1;

[0057] S2, leaving the battery cell treated in step S1 to stand for a period of time T to eliminate polarization of the battery cell;

[0058] S3, adjusting the charge of the battery cell after being left to stand in step S2:

[0059] S31, collecting the open circuit voltage V2 of the battery cell processed in step S2 at the beginning of the charge adjustment process;

[0060] S32: The charging and discharging step must be a constant voltage charging step. At the same time, the constant voltage charging step must keep the voltage unchanged after the cell voltage is charged to V3, and the cell current begins to gradually decrease to the set value I 设定 Then end this step;

[0061] S4, sequentially collecting the maximum current I of the constant voltage charging of each battery cell processed in step S3 max ; S5, if the maximum current I of the battery collected in step S4 max Meets u-3σ≤I max ≤u+3σ, the self-discharge of the battery cell is judged to be qualified, otherwise the self-discharge of the battery cell is unqualified, wherein:

[0062] u is the maximum current I of the batch of cells for constant voltage charging max The mean of

[0063] σ is the maximum current I of the batch of cells for constant voltage charging max The standard deviation of .

[0064] Furthermore, in step S1, the process step must be terminated at the voltage V1 of the battery cell.

[0065] Furthermore, the voltage V1 in step S1 is in the range of 3.0V.

[0066] Furthermore, the range of the standing time T in step S2 is T=720 minutes.

[0067] Further, the voltage V3 in step S3 is in the range of 3.0 volts.

[0068] Furthermore, the setting value I of the battery cell in step S3 is 设定 It is 0.05C ampere.

[0069] Furthermore, V2<V3≤V1.

[0070] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, any of the above-mentioned lithium-ion battery self-discharge screening methods is implemented.

[0071] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements any of the above-mentioned lithium-ion battery self-discharge screening methods.

[0072] Example 2

[0073] Taking lithium iron phosphate battery as an example, a self-discharge screening method for lithium-ion batteries has the following specific steps:

[0074] S1. Capacity division of a batch of pre-charged cells, where:

[0075] The final voltage of the cell after capacity division is V1;

[0076] S2, leaving the battery cell treated in step S1 to stand for a period of time T to eliminate polarization of the battery cell;

[0077] S3, adjusting the charge of the battery cell after being left to stand in step S2:

[0078] S31, collecting the open circuit voltage V2 of the battery cell processed in step S2 at the beginning of the charge adjustment process;

[0079] S32, the first charge and discharge step of the load adjustment process must be a constant voltage charging step. At the same time, the constant voltage charging step must keep the voltage unchanged after the cell voltage is charged to V3, and the cell current begins to gradually decrease to the set value I 设定 Then end this step;

[0080] S4, sequentially collecting the maximum current I of the constant voltage charging of each battery cell processed in step S3 max ; S5, if the maximum current I of the battery collected in step S4 max Meets u-3σ≤I max ≤u+3σ, the self-discharge of the battery cell is judged to be qualified, otherwise the self-discharge of the battery cell is unqualified, wherein:

[0081] u is the maximum current I of the batch of cells for constant voltage charging max The mean of

[0082] σ is the maximum current I of the batch of cells for constant voltage charging max The standard deviation of .

[0083] Furthermore, in step S1, the process step must be terminated at the voltage V1 of the battery cell.

[0084] Furthermore, the voltage V1 in step S1 is in the range of 3.65V.

[0085] Furthermore, the range of the standing time T in step S2 is T=780 minutes.

[0086] Further, the voltage V3 in step S3 is in the range of 3.65 volts.

[0087] Furthermore, the setting value I of the battery cell in step S3 is 设定 It is 0.05C ampere.

[0088] Furthermore, V2<V3≤V1.

[0089] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, any of the above-mentioned lithium-ion battery self-discharge screening methods is implemented.

[0090] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements any of the above-mentioned lithium-ion battery self-discharge screening methods.

[0091] Example 3

[0092] Taking lithium iron phosphate battery as an example, a self-discharge screening method for lithium-ion batteries has the following specific steps:

[0093] S1. Capacity division of a batch of formed cells, including:

[0094] The final voltage of the cell after capacity division is V1;

[0095] S2, leaving the battery cell treated in step S1 to stand for a period of time T to eliminate polarization of the battery cell;

[0096] S3, adjusting the charge of the battery cell after being left to stand in step S2:

[0097] S31, collecting the open circuit voltage V2 of the battery cell processed in step S2 at the beginning of the charge adjustment process;

[0098] S32, the first charge and discharge step of the load adjustment process must be a constant voltage charging step. At the same time, the constant voltage charging step must keep the voltage unchanged after the cell voltage is charged to V3, and the cell current begins to gradually decrease to the set value I 设定 Then end this step;

[0099] S4, sequentially collecting the maximum current I of the constant voltage charging of each battery cell processed in step S3 max ; S5, if the maximum current I of the battery collected in step S4 max Meets u-3σ≤I max ≤u+3σ, the self-discharge of the battery cell is judged to be qualified, otherwise the self-discharge of the battery cell is unqualified, wherein:

[0100] u is the maximum current I of the batch of cells for constant voltage charging max The mean of

[0101] σ is the maximum current I of the batch of cells for constant voltage charging max The standard deviation of .

[0102] Furthermore, in step S1, the process step must be terminated at the voltage V1 of the battery cell.

[0103] Furthermore, the voltage V1 in step S1 is in the range of 3.3V.

[0104] Furthermore, the range of the standing time T in step S2 is T=750 minutes.

[0105] Further, the voltage V3 in step S3 is in the range of 3.3 volts.

[0106] Furthermore, the setting value I of the battery cell in step S3 is 设定 It is 0.05C ampere.

[0107] Furthermore, V2<V3≤V1.

[0108] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, any of the above-mentioned lithium-ion battery self-discharge screening methods is implemented.

[0109] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements any of the above-mentioned lithium-ion battery self-discharge screening methods.

[0110] Example 4

[0111] Taking ternary cells as an example, a self-discharge screening method for lithium-ion batteries has the following specific steps:

[0112] S1. Capacity division of a batch of pre-charged cells, where:

[0113] The final voltage of the cell after capacity division is V1;

[0114] S2, leaving the battery cell treated in step S1 to stand for a period of time T to eliminate polarization of the battery cell;

[0115] S3, adjusting the charge of the battery cell after being left to stand in step S2:

[0116] S31, collecting the open circuit voltage V2 of the battery cell processed in step S2 at the beginning of the charge adjustment process;

[0117] S32, the first charge and discharge step of the load adjustment process must be a constant voltage charging step. At the same time, the constant voltage charging step must keep the voltage unchanged after the cell voltage is charged to V3, and the cell current begins to gradually decrease to the set value I 设定 Then end this step;

[0118] S4, sequentially collecting the maximum current I of the constant voltage charging of each battery cell processed in step S3 max ; S5, if the maximum current I of the battery collected in step S4 max Meets u-3σ≤I max ≤u+3σ, the self-discharge of the battery cell is judged to be qualified, otherwise the self-discharge of the battery cell is unqualified, wherein:

[0119] u is the maximum current I of the batch of cells for constant voltage charging max The mean of

[0120] σ is the maximum current I of the batch of cells for constant voltage charging max The standard deviation of .

[0121] Furthermore, in step S1, the process step must be terminated at the voltage V1 of the battery cell.

[0122] Furthermore, the voltage V1 in step S1 is in the range of 3.0V.

[0123] Furthermore, the range of the standing time T in step S2 is T=720 minutes.

[0124] Further, the voltage V3 in step S3 is in the range of 3.0 volts.

[0125] Furthermore, the setting value I of the battery cell in step S3 is 设定 It is 0.05C ampere.

[0126] Furthermore, V2<V3≤V1.

[0127] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, any of the above-mentioned lithium-ion battery self-discharge screening methods is implemented.

[0128] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements any of the above-mentioned lithium-ion battery self-discharge screening methods.

[0129] Example 5

[0130] Taking ternary cells as an example, a self-discharge screening method for lithium-ion batteries has the following specific steps:

[0131] S1. Capacity division of a batch of formed cells, including:

[0132] The final voltage of the cell after capacity division is V1;

[0133] S2, leaving the battery cell treated in step S1 to stand for a period of time T to eliminate polarization of the battery cell;

[0134] S3, adjusting the charge of the battery cell after being left to stand in step S2:

[0135] S31, collecting the open circuit voltage V2 of the battery cell processed in step S2 at the beginning of the charge adjustment process;

[0136] S32, the first charge and discharge step of the load adjustment process must be a constant voltage charging step. At the same time, the constant voltage charging step must keep the voltage unchanged after the cell voltage is charged to V3, and the cell current begins to gradually decrease to the set value I 设定 Then end this step;

[0137] S4, sequentially collecting the maximum current I of the constant voltage charging of each battery cell processed in step S3 max ; S5, if the maximum current I of the battery collected in step S4 max Meets u-3σ≤I max ≤u+3σ, the self-discharge of the battery cell is judged to be qualified, otherwise the self-discharge of the battery cell is unqualified, wherein:

[0138] u is the maximum current I of the batch of cells for constant voltage charging max The mean of

[0139] σ is the maximum current I of the batch of cells for constant voltage charging max The standard deviation of .

[0140] Furthermore, in step S1, the process step must be terminated at the voltage V1 of the battery cell.

[0141] Furthermore, the voltage V1 in step S1 is in the range of 4.2V.

[0142] Furthermore, the range of the standing time T in step S2 is T=900 minutes.

[0143] Further, the voltage V3 in step S3 is in the range of 4.2 volts.

[0144] Furthermore, the setting value I of the battery cell in step S3 is 设定 It is 0.05C ampere.

[0145] Furthermore, V2<V3≤V1.

[0146] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, any of the above-mentioned lithium-ion battery self-discharge screening methods is implemented.

[0147] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements any of the above-mentioned lithium-ion battery self-discharge screening methods.

[0148] Example 6

[0149] Taking ternary cells as an example, a self-discharge screening method for lithium-ion batteries has the following specific steps:

[0150] S1. Capacity division of a batch of pre-charged cells, where:

[0151] The final voltage of the cell after capacity division is V1;

[0152] S2, leaving the battery cell treated in step S1 to stand for a period of time T to eliminate polarization of the battery cell;

[0153] S3, adjusting the charge of the battery cell after being left to stand in step S2:

[0154] S31, collecting the open circuit voltage V2 of the battery cell processed in step S2 at the beginning of the charge adjustment process;

[0155] S32, the first charge and discharge step of the load adjustment process must be a constant voltage charging step. At the same time, the constant voltage charging step must keep the voltage unchanged after the cell voltage is charged to V3, and the cell current begins to gradually decrease to the set value I 设定 Then end this step;

[0156] S4, sequentially collecting the maximum current I of the constant voltage charging of each battery cell processed in step S3 max ; S5, if the maximum current I of the battery collected in step S4 max Meets u-3σ≤I max≤u+3σ, the self-discharge of the battery cell is judged to be qualified, otherwise the self-discharge of the battery cell is unqualified, wherein:

[0157] u is the maximum current I of the batch of cells for constant voltage charging max The mean of

[0158] σ is the maximum current I of the batch of cells for constant voltage charging max The standard deviation of .

[0159] Furthermore, in step S1, the process step must be terminated at the voltage V1 of the battery cell.

[0160] Furthermore, the voltage V1 in step S1 is in the range of 3.8V.

[0161] Furthermore, the range of the standing time T in step S2 is T=800 minutes.

[0162] Further, the voltage V3 in step S3 is in the range of 3.8V.

[0163] Furthermore, the setting value I of the battery cell in step S3 is 设定 It is 0.05C ampere.

[0164] Furthermore, V2<V3≤V1.

[0165] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, any of the above-mentioned lithium-ion battery self-discharge screening methods is implemented.

[0166] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements any of the above-mentioned lithium-ion battery self-discharge screening methods.

[0167] Example 7

[0168] A lithium-ion battery self-discharge screening method, the specific steps are as follows:

[0169] Step S1, dividing the capacity of a batch of formed or pre-charged cells. This embodiment takes a lithium iron phosphate cell as an example. The capacity division process is shown in Table 1, where:

[0170] The voltage of the cell after capacity division is V1, and the cut-off condition of this process step must be cut off at the cell voltage V1;

[0171] Table 1 Capacity division flow chart

[0172]

[0173]

[0174] The capacity-dividing process fully charges and discharges the battery cell. After determining the actual capacity of the battery cell, the battery cell is charged in step 6 with constant current and constant voltage until the voltage reaches V1 and the current drops to 0.05C, where C represents the capacity and V1 is less than the full-charge voltage specified for the battery cell.

[0175] Step 6 uses constant current and constant voltage charging, which reduces the polarization of the battery cells and reduces the voltage difference between single battery cells.

[0176] S2. Let the cells stand still after capacity division to eliminate polarization of the cells. Generally, the standing time T of the cells should not be less than 720 minutes (depending on the type and capacity of the cells).

[0177] S3. Adjust the charge of the battery cell. This embodiment takes a lithium iron phosphate battery cell as an example. The charge adjustment process is shown in Table 2.

[0178] Table 2 Load adjustment process

[0179]

[0180] When the charge adjustment process step 1 is in sleep mode, the equipment collects the open circuit voltage V2 of the battery cell. Because the battery cell has been at rest for a period of time T, V2 is less than the capacity division cut-off voltage V1. Therefore, there is a voltage difference ΔV=V1-V2 between the open circuit voltage V2 of the battery cell and the capacity division cut-off voltage V1.

[0181] Step 2 of the charging process must be set to constant voltage charging. At this time, the current rises rapidly from 0mA at the beginning to I max , so that the cell voltage quickly rises from V2 to V3 (V3 setting: V2<V3≤V1). When the cell voltage reaches V3, the cell maintains the voltage V3 unchanged, and the cell current starts to rise from I max After it drops to 0.05C, the process is terminated. The current and voltage curve of the constant voltage charging process is as follows: Figure 3 shown.

[0182] S4, sequentially collecting the maximum current I of the constant voltage charging of each battery cell processed in step S3 max ;

[0183] This embodiment studies the constant voltage charging of cells with different V2 values ​​to the same voltage V3. max The data are recorded in Table 3 and Figure 4 As shown,

[0184] Table 3 Constant voltage charging Imax data record

[0185]

[0186]

[0187] From the recorded data, Imax The relationship curve with the voltage difference ΔV is as follows Figure 5 As shown. For abnormal self-discharge cells, the voltage decays greatly during the static process. After static, V2 is smaller than that of normal cells, and the voltage difference ΔV will be larger, which will indirectly lead to constant voltage charging to V3. max The present invention utilizes this principle to screen the self-discharge of the battery cells.

[0188] Step S5: According to u-3σ≤I max ≤u+3σ to screen whether the self-discharge of a batch of batteries is legal; if the maximum current I of the battery obtained in step S4 is max Meets u-3σ≤I max ≤u+3σ, the self-discharge of the battery cell is judged to be qualified, otherwise the self-discharge of the battery cell is judged to be unqualified, wherein:

[0189] u is the maximum current I of the batch of cells for constant voltage charging max The mean of

[0190] σ is the maximum current I of the batch of cells for constant voltage charging max The standard deviation of .

[0191] The lithium ion battery self-discharge screening method, electronic device and storage medium disclosed in the present invention have the following advantages:

[0192] (1) Different from the voltage drop method for measuring the self-discharge of the battery cell, the two OCV tests are cancelled, which reduces the impact of the measurement system differences on the OCV, and is conducive to the accuracy of self-discharge screening;

[0193] (2) Solved the problem that the capacity attenuation method has poor capacity test accuracy due to the influence of ambient temperature on capacity, which leads to inaccurate self-discharge screening;

[0194] (3) The present invention adopts the characteristics of a separate constant voltage charging process step, and the cell is charged to a voltage V1 by capacity division, and the voltage will decay after being left at rest. After being left at rest, the cell performs a charge adjustment process; the charge is adjusted to an open circuit voltage V2, and the charge adjustment starts with constant voltage charging, so that the cell voltage reaches V3 again, and V3 is set as follows V2<V3≤V1; according to the different degrees of voltage decay when the cell is left at rest, the current I of the constant voltage charging to reach V3 is adjusted. max Different, to conduct self-discharge screening.

[0195] The above describes the embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A method for screening self-discharge of lithium-ion batteries, characterized in that: The specific steps are as follows: S1. Capacity division of a batch of formed or pre-charged cells, where: The final voltage of the cell after capacity division is V1; S2, leaving the battery cell treated in step S1 to stand for a period of time T to eliminate polarization of the battery cell; S3, adjusting the charge of the battery cell after being left to stand in step S2: S31, collecting the open circuit voltage V2 of the battery cell processed in step S2 at the beginning of the charge adjustment process; S32, the first charge and discharge step of the load adjustment process must be a constant voltage charging step. At the same time, the constant voltage charging step must keep the voltage unchanged after the cell voltage is charged to V3, and the cell current begins to gradually decrease to the set value I 设定 Then end this step; S4, sequentially collecting the maximum current I of the constant voltage charging of each battery cell processed in step S3 max ; S5. If the maximum current I of the battery cell collected in step S4 max Meets u-3σ≤I max ≤u+3σ, the self-discharge of the battery cell is judged to be qualified, otherwise the self-discharge of the battery cell is unqualified, wherein: u is the maximum current I of the batch of cells for constant voltage charging max The mean of σ is the maximum current I of the batch of cells for constant voltage charging max The standard deviation of .

2. A lithium ion battery self-discharge screening method as claimed in claim 1, characterized in that: In step S1, the process step must be terminated at the voltage V1 of the battery cell.

3. A lithium ion battery self-discharge screening method as claimed in claim 2, characterized in that: If the battery cell is a lithium iron phosphate battery cell, the voltage V1 in step S1 ranges from 3.0 to 3.65 volts; If the battery cell is a ternary battery cell, the voltage V1 in step S1 ranges from 3.0 to 4.2 volts.

4. A lithium ion battery self-discharge screening method as claimed in claim 1, characterized in that: The range of the standing time T in step S2 is T≥720 minutes.

5. A lithium ion battery self-discharge screening method as claimed in claim 1, characterized in that: If the battery cell is a lithium iron phosphate battery cell, the voltage V3 in step S3 is in the range of 3.0 to 3.65 volts; If the battery cell is a ternary battery cell, the voltage V3 in step S3 is in the range of 3.0 to 4.2 volts.

6. A lithium ion battery self-discharge screening method as claimed in claim 1, characterized in that: The set value I of the battery cell in step S3 设定 It is 0.05C ampere.

7. A lithium ion battery self-discharge screening method as claimed in claim 1, characterized in that: V2<V3≤V1.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the lithium-ion battery self-discharge screening method according to any one of claims 1 to 7 is implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the lithium-ion battery self-discharge screening method described in any one of claims 1 to 7 is implemented.

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