Grouping method of battery modules and application of grouping method

Abstract

The invention provides a battery module matching method and application thereof, and relates to the technical field of batteries. The matching method of the battery module provided by the invention comprises the following steps: emptying the electric quantity of single batteries after capacity grading, then adjusting the electric quantity SOC of the single batteries to be less than or equal to 10%, standing until the voltage recovers to the highest point so as to eliminate the polarization effect, and recording the voltage OCV1 of the highest point and the internal resistance ACR1 of the highest point; placing the processed single battery in a constant-temperature environment until the voltage is stable, recording the voltage value OCV2 and the internal resistance ACR2 at the moment, and calculating the change rate K of the voltage in unit time from OCV1 to OCV2; and performing consistency screening on the battery monomers according to the capacity, the OCV1, the ACR1, the OCV2, the ACR2 and the K value of the battery monomers, and then matching the screened battery monomers. According to the matching method, the module pressure difference can be obviously improved, and the vicious cycle of'consistency degradation-thermal runaway 'of the battery pack can be effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method for matching battery modules and its application. Background Art

[0002] Existing battery matching technologies usually screen based on capacity, internal resistance or voltage consistency. However, under low SOC (<10%) conditions, the polarization effect, self-discharge rate difference and internal side reactions of the battery are aggravated, resulting in a significant increase in the voltage difference between monomers in the module, affecting the performance and life of the battery pack. The traditional matching method is not optimized for the low SOC characteristics, resulting in the out-of-control voltage difference after deep discharge or long-term static state of the module, leading to potential safety hazards.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] The first object of the present invention is to provide a method for matching battery modules to solve the above technical problems.

[0005] The second object of the present invention is to provide the application of the above method for matching battery modules in the preparation of battery modules.

[0006] In order to achieve the above objects, the following technical solutions are specifically adopted:

[0007] In the first aspect, the present invention provides a method for matching battery modules, including the following steps:

[0008] a. Discharge the power of the battery monomers after grading, then adjust the power of the battery monomers to SOC ≤ 10%, and let it stand until the voltage recovers to the highest point to eliminate the polarization effect, and record the voltage OCV1 and internal resistance ACR1 at the highest point;

[0009] b. Place the battery monomers processed in step a in a constant temperature environment until the voltage is stable, that is, the voltage change ≤ 0.1 mV / d, record the voltage value OCV2 and internal resistance ACR2 at this time, and calculate the change rate K of the voltage from OCV1 to OCV2 per unit time;

[0010] c. Perform consistency screening on the battery monomers according to the capacity, OCV1, ACR1, OCV2, ACR2 and voltage change rate of the battery monomers, and then match the screened battery monomers.

[0011] As a further technical solution, in step a, the power of the battery monomers after grading is discharged with a current ≤ 1 / 3C.

[0012] As a further technical solution, in step a, after discharging the power, the power of the battery monomers is adjusted to SOC of 2.5% - 5%.

[0013] As a further technical solution, the temperature of the constant temperature environment is 20 to 45 °C.

[0014] As a further technical solution, the shelving time is 6 to 10 days.

[0015] As a further technical solution, the conditions for consistency screening are as follows:

[0016] The within-group difference in capacity ≤ 1% of the rated capacity;

[0017] The within-group difference in OCV1 ≤ 120 mV;

[0018] The within-group difference in ACR1 ≤ 0.2 mΩ;

[0019] The within-group difference in OCV2 ≤ 30 mV;

[0020] The within-group difference in ACR2 ≤ 0.2 mΩ;

[0021] The within-group difference in K is less than 1 mV / d.

[0022] As a further technical solution, the battery includes a lithium-ion battery and a sodium-ion battery.

[0023] As a further technical solution, the types of the battery include a wound battery and a laminated battery.

[0024] In a second aspect, the present invention provides an application of the matching method of the above battery module in the preparation of a battery module.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The matching method of the battery module provided by the present invention performs a shelving test on battery cells under low SOC conditions, monitors the voltage recovery characteristics (voltage change rate K) during shelving, and simultaneously combines voltage, internal resistance, and capacity parameters to screen out cells with excellent consistency under low SOC, realizing dynamic optimization of the module pressure difference. Through experimental research, the battery module obtained by the matching method of the present invention has a 10% to 60% reduction in pressure difference under low SOC conditions compared with the conventional method, effectively improving the discharge depth and cycle life of the battery. By predicting the long-term static pressure difference through voltage recovery characteristics, it can effectively avoid the vicious cycle of "consistency deterioration - thermal runaway" of the battery pack. Description of the Drawings

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 Comparison of the end - voltage differences of 1P8S modules assembled with different SOC storage and matching methods at 25°C with 1C discharge in Example 1.

[0029] Figure 2 Comparison of the end - voltage differences of 1P8S modules assembled with different SOC storage and matching methods at 25°C with 1C discharge in Example 2. Specific Embodiments

[0030] The following will describe the implementation schemes of the present invention in detail in combination with the embodiments and examples. However, those skilled in the art will understand that the following embodiments and examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Those not specifying specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not indicating the manufacturer can be obtained as conventional products through commercial purchase.

[0031] In the first aspect, the present invention provides a method for matching battery modules, including the following steps:

[0032] a. Discharge the electricity of the battery cells after grading, then adjust the electricity of the battery cells to SOC ≤ 10%, and let it stand until the voltage recovers to the highest point to eliminate the polarization effect, and record the voltage OCV1 at the highest point and its internal resistance ACR1;

[0033] b. Place the battery cells processed in step a in a constant - temperature environment until the voltage is stable, that is, the voltage change ≤ 0.1 mV / d, record the voltage value OCV2 at this time and its internal resistance ACR2, and calculate the change rate K of the voltage from OCV1 to OCV2 per unit time;

[0034] c. Screen the battery cells for consistency according to the capacity, OCV1, ACR1, OCV2, ACR2 of the battery cells and the voltage change rate, and then match the screened battery cells.

[0035] The battery matching method provided by the present invention performs a rest test on battery cells under low SOC conditions, monitors the voltage recovery characteristics during the rest period, and combines voltage, internal resistance, and capacity parameters to select cells with excellent consistency under low SOC, achieving dynamic optimization of the module voltage difference. Through experimental research, the battery module obtained by the matching method of the present invention has a voltage difference reduction of 10% - 60% under low SOC conditions compared with the conventional method, effectively improving the discharge depth and cycle life of the battery. Predicting the long-term static voltage difference through the voltage recovery characteristics can effectively avoid the vicious cycle of "consistency deterioration - thermal runaway" of the battery pack.

[0036] In some alternative embodiments, in step a, the current of ≤1 / 3C is used to discharge the charged battery cells until the charge is exhausted.

[0037] Discharging with a small current to fully discharge the battery charge.

[0038] In some alternative embodiments, in step a, after the charge is exhausted, the charge of the battery cells is adjusted to an SOC of 2.5% - 5%, which helps to improve the performance and life of the battery module obtained by matching.

[0039] In some alternative embodiments, in step a, the rest time is 1 - 3 days to allow the voltage value of the battery cells to recover to the highest point.

[0040] In some alternative embodiments, the temperature of the constant temperature environment in step b can be, for example, but not limited to, 20°C, 30°C, or 45°C.

[0041] In some alternative embodiments, the rest time in step b is 6 - 10 days to allow the voltage value of the battery cells to stabilize.

[0042] In some alternative embodiments, the calculation formula for the voltage change rate K is as follows:

[0043] K = ΔV / Δt;

[0044] Where ΔV is the rest voltage difference (OCV1 - OCV2), and Δt is the time difference between measuring OCV1 and OCV2.

[0045] In some alternative embodiments, the conditions for the consistency screening are as follows:

[0046] The within-group difference in capacity ≤1% of the rated capacity;

[0047] The within-group difference in OCV1 ≤120 mV;

[0048] The within-group difference in ACR1 ≤0.2 mΩ;

[0049] The within-group difference of the OCV2 ≤ 30 mV;

[0050] The within-group difference of the ACR2 ≤ 0.2 mΩ;

[0051] The within-group difference of the K < 1 mV / d.

[0052] In some alternative embodiments, the battery includes, but is not limited to, lithium-ion batteries and sodium-ion batteries.

[0053] The battery module matching method provided by the present invention is applicable to the matching of lithium-ion batteries, sodium-ion batteries, etc.

[0054] In some alternative embodiments, the types of the battery include wound batteries and laminated batteries.

[0055] The battery module matching method provided by the present invention is applicable to the matching of wound batteries and laminated batteries.

[0056] In a second aspect, the present invention provides an application of the above battery module matching method in the preparation of battery modules.

[0057] The battery module obtained by using the battery module matching method of the present invention has better battery performance and longer lifespan, and can be used in the preparation of battery modules.

[0058] The present invention will be further described below through specific examples. However, it should be understood that these examples are only for more detailed description and should not be construed as limiting the present invention in any form.

[0059] Example 1

[0060] Battery cell type: LiFePO4 soft-pack battery, capacity 40 Ah, charge and discharge voltage range 2.5 - 3.65 V.

[0061] The above LiFePO4 soft-pack batteries are divided into 5 groups, with 100 pcs in each group. Each group of batteries is matched to obtain a battery module. Among them, the module type: 1P8S, without an equalization strategy, charge and discharge voltage range 18.4 - 29.2 V (single cell 2.3 - 3.65 V).

[0062] The matching method is as follows:

[0063] 1. Align at the end of discharge: The battery cells are charged and discharged for grading at 0.5C at 25 ± 2 °C, and then discharged to the lower limit voltage of 2.3 V at a current of ≤ 1 / 3C to completely discharge the battery cells.

[0064] 2. SOC Adjustment: At 25 ± 2°C, adjust the SOC to 27%, 10%, 5%, 2.5%, and 0% respectively; let it stand until the voltage recovers to the highest point to eliminate the polarization effect (about 1 - 3 days of standing), and measure the OCV1 and internal resistance ACR1 at the highest point.

[0065] 3. Shelf Test and Data Acquisition: At 25 ± 2°C, let the single battery stand until the voltage is stable (about 6 - 10 days), measure the voltage value OCV2 and its internal resistance ACR2 when it reaches stability, and calculate the change rate K of the battery voltage from OCV1 to OCV2 per unit time (K = ΔV / Δt);

[0066] 4. Screening and Matching: Conduct consistency screening on the single batteries according to the capacity, OCV1, ACR1, OCV2, ACR2, and voltage change rate of the single batteries, and then match the screened single batteries;

[0067] 5. Assembly Module Test: Assemble the matched single cells into a 1P8S module without an equalization strategy; discharge at 1C to 18.4V at 25 ± 2°C, record the voltages of the module and each single cell in real time, and calculate the voltage difference of the single cells. The results are shown in Table 1 and Figure 1 as follows.

[0068] Table 1

[0069]

[0070] Note: The process standards described in the table are the qualified ranges of the performance data of the subsequent process, and the within-group standard is the matching control range of the performance data of the subsequent process within the grouping group; taking 27% SOC as an example, the formation capacity in the process standard refers to selecting batteries with a capacity in the range of 40900 - 41600 mAh, and the formation capacity in the within-group standard refers to dividing the batteries that meet the process standards into multiple groups, and the range of the formation capacity within the group (i.e., the difference between the maximum capacity and the minimum capacity of the single cells within the group) should be within 400 mV; the same applies to Table 2.

[0071] The results show that the better example is the 2.5% SOC shelf matching, and the voltage difference at the end of the 1C discharge of its 1P8S module is reduced by about 55.8% compared with the conventional 27% SOC.

[0072] Example 2

[0073] Type of single battery: Sodium - ion soft - pack battery, capacity 20 Ah, charge - discharge voltage range 2.6 - 4.2V.

[0074] Divide the above - mentioned sodium - ion soft - pack batteries into 4 groups, with 100 pcs in each group, and match each group of batteries to obtain battery modules. Among them, module type: 1P8S, without an equalization strategy, charge - discharge voltage range 19.2 - 33.6V (single cell 2.4 - 4.2V).

[0075] The grouping method is as follows:

[0076] 1. Discharge end alignment: The battery cells are charged and discharged for grading at 0.5C at 25±2°C, and then discharged at a current of ≤1 / 3C to the lower limit voltage of 2.4V to completely discharge the battery cells.

[0077] 2. SOC adjustment: At 25±2°C, adjust the SOC to 30%, 10%, 5%, and 2.5% respectively; let it stand until the voltage recovers to the highest point to eliminate the polarization effect (about 1 - 3 days of standing), and measure the OCV1 and internal resistance ACR1 at the highest point.

[0078] 3. Shelf test and data collection: At 25±2°C, place the battery cells until the voltage is stable (about 6 - 10 days), measure the voltage value OCV2 and its internal resistance ACR2 when it reaches stability, and calculate the change rate K of the battery voltage from OCV1 to OCV2 per unit time (K = ΔV / Δt);

[0079] 4. Screening and grouping: Screen the battery cells for consistency according to the capacity, OCV1, ACR1, OCV2, ACR2, and voltage change rate of the battery cells, and then group the screened battery cells;

[0080] 5. Assembly module test: Assemble the grouped cells into a 1P8S module without an equalization strategy; discharge at 1C to 19.2V at 25±2°C, record the voltages of the module and each cell in real time, and calculate the cell voltage difference. The results are shown in Table 2 and Figure 2 as follows.

[0081] Table 2

[0082]

[0083]

[0084] The results show that the better example is the grouping with 5% SOC shelving, and the voltage difference at the end of 1C discharge of its 1P8S module is reduced by about 65.78% compared with the conventional 30% SOC.

[0085] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for matching battery modules, characterized in that, Including the following steps: a. Discharge the charged battery cell until it is completely discharged, then adjust the state of charge (SOC) of the battery cell to SOC ≤ 10%, and let it stand until the voltage recovers to the highest point to eliminate the polarization effect. Record the highest voltage OCV1 and its internal resistance ACR1. b. Place the battery cell processed in step a in a constant temperature environment until the voltage stabilizes, i.e., the voltage change ≤ 0.1 mV / d. Record the voltage value OCV2 and its internal resistance ACR2 at this time, and calculate the change rate K of the voltage from OCV1 to OCV2 per unit time. c. Perform consistency screening on the battery cells according to the capacity, OCV1, ACR1, OCV2, ACR2, and voltage change rate of the battery cells, and then group the screened battery cells.

2. The matching method of the battery module according to claim 1, wherein In step a, use a current of ≤ 1 / 3C to discharge the charged battery cell until it is completely discharged.

3. The matching method of the battery module according to claim 1, characterized in that, In step a, after discharging, adjust the state of charge (SOC) of the battery cell to 2.5% - 5%.

4. The matching method of the battery module according to claim 1, wherein, The temperature of the constant temperature environment is 20 - 45 °C.

5. The matching method of the battery module according to claim 1, wherein, The standing time is 6 - 10 days.

6. The battery module matching method according to claim 1, characterized in that The conditions for the consistency screening are as follows: The within-group difference in capacity ≤ 1% of the rated capacity; The within-group difference in OCV1 ≤ 120 mV; The within-group difference in ACR1 ≤ 0.2 mΩ; The within-group difference in OCV2 ≤ 30 mV; The within-group difference in ACR2 ≤ 0.2 mΩ; The within-group difference in K < 1 mV / d.

7. The matching method of the battery module according to claim 1, wherein, The battery includes lithium-ion batteries and sodium-ion batteries.

8. The matching method of the battery module according to claim 1, wherein, The types of the battery include wound batteries and laminated batteries.

9. Application of the method for grouping battery modules according to any one of claims 1 - 8 in the preparation of battery modules.

Images