Method for judging infiltration effect of battery cell
By calculating the film-forming peak area of electrolyte additives and combining it with dQ/dV curve analysis, the problem of difficulty in judging the electrolyte wetting effect in lithium batteries was solved, thus improving battery performance and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 阿特斯储能科技有限公司
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-10
AI Technical Summary
In the existing technology, the wetting effect of the electrolyte cannot be effectively judged during the lithium battery manufacturing process, which leads to unstable battery performance and may cause capacity decay and safety hazards.
By calculating the film-forming peak area of the electrolyte additive and combining it with the dQ/dV curve analysis, the wetting effect of the battery cell is judged, and the film-forming peak area threshold A1 is set to judge whether the wetting of the battery cell is qualified.
This enables accurate assessment of cell wetting effects, allowing for the screening of poorly wetting cells and improving battery performance stability and safety.
Smart Images
Figure CN121830835A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery technology and relates to a method for judging the wetting effect of battery cells. Background Technology
[0002] In lithium batteries, the degree to which the electrolyte wets the positive and negative electrodes is one of the key factors affecting the battery's cycle life and safety. If the electrolyte cannot fully penetrate the electrode materials, it may lead to local ion transport obstruction, resulting in problems such as capacity decay, increased internal resistance, or even thermal runaway.
[0003] In the lithium battery manufacturing process, after electrolyte injection, the electrolyte needs to be allowed to fully wet the electrodes and separators by standing before formation to form a stable SEI film. Therefore, full wetting is very important for formation. However, during the manufacturing process, there will be fluctuations in the content of electrolyte additives. Furthermore, differences in wetting time, the thickness of the positive and negative electrodes, and compaction will all affect the formation effect, thereby affecting the battery performance.
[0004] Based on the above research, a method is needed to determine the wetting effect of battery cells in order to screen out poorly wetting cells. Summary of the Invention
[0005] The purpose of this invention is to provide a method for judging the wetting effect of a battery cell, wherein the method judges the wetting effect before formation by calculating the film-forming peak area of the electrolyte additive.
[0006] To achieve this objective, the present invention adopts the following technical solution:
[0007] This invention provides a method for determining the wetting effect of a battery cell, the method comprising the following steps:
[0008] (1) Provide a plurality of first cells, wherein the electrolyte of the plurality of first cells contains different amounts of additives;
[0009] (2) Test the energy of the first cells and determine the minimum content of the additive in the electrolyte based on the test results. The minimum content is recorded as M1.
[0010] (3) Provide a plurality of second cells, wherein the content of additives in the electrolyte of the plurality of second cells is M1, and the immersion time gradient of the electrolyte of the plurality of second cells varies.
[0011] (4) Form the plurality of second cells, and then collect the dQ / dV curve of the formed second cells, calculate the film-forming peak area of the additive in the second cells, and when the film-forming peak area no longer increases, the corresponding electrolyte wetting time is recorded as T1.
[0012] (5) Inject the electrolyte containing additive M1 into several third cells, immerse them for T1 time and then perform formation. Then collect the dQ / dV curve of the third cell after formation, calculate the film-forming peak area of the additive in the third cell, and record the average value of the film-forming peak area of all third cells as A1.
[0013] If the film-forming peak area corresponding to the battery cell under test is ≥ A1, then the wetting is qualified; if the film-forming peak area corresponding to the battery cell under test is < A1, then the wetting is unqualified.
[0014] In some embodiments, the additive in step (1) includes any one or a combination of at least two of DTD, VC, EC or AMSD.
[0015] In some embodiments, step (2) testing the plurality of first cells includes testing the cycle performance of the plurality of first cells.
[0016] In some embodiments, the method for determining the minimum content of additive in the electrolyte in step (2) is: the minimum content of additive when the 8000-cycle life obtained by the test of the plurality of first cells is above 70%.
[0017] In some embodiments, the electrolyte immersion time gradient of the plurality of second cells in step (3) is increased, wherein the interval between adjacent gradients is 10h-15h.
[0018] In some embodiments, the fact that the film-forming peak area no longer increases in step (4) means that as the immersion time gradient increases, the difference between the film-forming peak area at immersion time T2 and the film-forming peak area at immersion time T1 is ≤0.003, where T2 is the immersion time after T1.
[0019] In some embodiments, the transformation described in steps (4) and (5) each independently includes the following steps:
[0020] The cells to be formed undergo their first charge under external pressure, followed by a first resting period after the first charge is completed.
[0021] After the first settling period, a second charge is performed, and after the second charge is performed, a second settling period is performed.
[0022] After the second settling period, a third charging process is initiated, and the formation process ends after the third charging process.
[0023] In some embodiments, the applied pressure is 250 kgf-350 kgf.
[0024] In some embodiments, the charging rate of the third charge is greater than the charging rate of the second charge.
[0025] In some embodiments, the charging rate of the second charge is greater than the charging rate of the first charge.
[0026] In some embodiments, the first charge has a charging rate of 0.04C-0.06C and a charging time of 55min-65min.
[0027] In some embodiments, the second charge has a charging rate of 0.08C-0.12C and a charging time of 55min-65min.
[0028] In some embodiments, the third charge has a charging rate of 0.18C-0.22C and a charging time of 55min-65min.
[0029] In some embodiments, the first settling time is 8-15 minutes.
[0030] In some embodiments, the second settling time is 2-5 minutes.
[0031] Compared with the prior art, the present invention has the following beneficial effects:
[0032] This invention first provides several first battery cells with different additive contents in the electrolyte. Then, the electrochemical performance of these first battery cells is tested, and the minimum additive content M1 in the electrolyte is determined based on the test results. Next, an electrolyte with an additive content of M1 is injected into multiple battery cells to form a set of several second battery cells. Although the electrolyte injected into different battery cells is the same, the wetting time gradient is increased. Formation is performed on these second battery cells with increased electrolyte wetting time gradients, and dQ / dV curves are collected. The film-forming peak area of the additive is calculated based on the dQ / dV curves. A set of peak areas for film formation is obtained. When the peak area of film formation no longer increases, the corresponding electrolyte wetting time is recorded as T1. Finally, electrolyte containing additive M1 is injected into several third cells. After wetting for T1 time, formation is performed. The dQ / dV curve is collected and the peak area of film formation of the additive is calculated. The average value A1 of the calculated peak area is used as the threshold. When the peak area of film formation of the cell under test is ≥ A1, it is judged as qualified for wetting. Otherwise, it is judged as unqualified for wetting. The wetting effect of the cell can be judged and the unqualified cells are picked out. Attached Figure Description
[0033] Figure 1 This is the dQ / dV curve of cell B1 described in Embodiment 1 of the present invention. Detailed Implementation
[0034] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.
[0035] This invention provides a method for determining the wetting effect of a battery cell, the method comprising the following steps:
[0036] (1) Provide a plurality of first cells, wherein the electrolyte of the plurality of first cells contains different amounts of additives;
[0037] (2) Test the first cells and determine the minimum content of additive in the electrolyte based on the test results. The minimum content is recorded as M1.
[0038] (3) Provide a plurality of second cells, wherein the content of additives in the electrolyte of the plurality of second cells is M1, and the immersion time gradient of the electrolyte of the plurality of second cells varies.
[0039] (4) Form the plurality of second cells, and then collect the dQ / dV curve of the formed second cells, calculate the film-forming peak area of the additive in the second cells, and when the film-forming peak area no longer increases, the corresponding electrolyte wetting time is recorded as T1.
[0040] (5) Inject the electrolyte containing additive M1 into several third cells, immerse them for T1 time and then perform formation. Then collect the dQ / dV curve of the third cell after formation, calculate the film-forming peak area of the additive in the third cell, and record the average value of the film-forming peak area of all third cells as A1.
[0041] If the film-forming peak area corresponding to the battery cell under test is ≥ A1, then the wetting is qualified; if the film-forming peak area corresponding to the battery cell under test is < A1, then the wetting is unqualified.
[0042] Since various electrolyte additives participate in the film-forming reaction during the formation process, the peak area of the additives changes with their content in the electrolyte. Therefore, this invention selects the peak area of one of the additives participating in the film formation during the formation process to determine the film-forming effect, thereby judging the wetting effect before formation. If the wetting effect is good, the peak area of the film formation meets the set value (A1 value). If the wetting effect is poor, the amount of additives participating in the reaction is small, the peak area of the film formation is small, and the set value (A1 value) is not met.
[0043] Specifically, this invention first selects a certain additive and adds it to the electrolyte in different amounts to obtain a set of electrolytes with different additive contents. These electrolytes are then injected into multiple battery cells to form a set of several first battery cells with different additive contents. The electrochemical performance of these first battery cells is then tested. Based on the test results, the minimum additive content M1 in the electrolyte is determined. The reason for determining the minimum content M1 is that at the minimum content M1, the battery's electrochemical performance meets the requirements (e.g., cycle performance). Otherwise, if the content is lower than the minimum content M1, the battery's electrochemical performance will not meet the requirements (e.g., cycle performance). Next... An electrolyte solution with an additive content of M1 is injected into multiple battery cells to form a group of second battery cells. Although the electrolyte is the same for different battery cells, the wetting time gradient increases. The second battery cells with the increased electrolyte wetting time gradient are formed, and dQ / dV curves are collected. The film-forming peak area of the additive is calculated based on the dQ / dV curves to obtain a set of film-forming peak areas. When the film-forming peak area no longer increases, the corresponding electrolyte wetting time is recorded as T1. The reason for determining T1 is that when fully wetting occurs, the amount of electrolyte additive reaction no longer increases, and the reaction peak area tends to stabilize and no longer increases.
[0044] Finally, the electrolyte containing additive M1 was injected into several third cells. After immersion for T1 time, formation was performed. The dQ / dV curve was collected and the film-forming peak area of the additive was calculated. The average value A1 of the calculated film-forming peak area was used as the threshold. When the film-forming peak area of the cell under test is ≥ A1, the immersion is qualified; otherwise, the immersion is unqualified.
[0045] It should be noted that the present invention does not specifically limit the type of additive, as long as it can participate in the film-forming reaction during the formation process and thus has a film-forming characteristic peak in the dQ / dV curve.
[0046] The dQ / dV curve mentioned in this invention refers to the differential capacity curve.
[0047] In one specific embodiment, the additive in step (1) includes any one or a combination of at least two of DTD (vinyl sulfate), VC (vinyl carbonate), EC (vinyl carbonate) or AMSD (2,4-diphenyl-4-methyl-1-pentene);
[0048] In one specific embodiment, step (2) of testing the plurality of first cells includes testing the cycle performance of the plurality of first cells.
[0049] In one specific embodiment, the method for determining the minimum content of additive in the electrolyte in step (2) is: the minimum content of additive when the 8000-cycle life obtained by the test of the plurality of first cells is above 70%.
[0050] In one specific embodiment, the electrolyte immersion time gradient of the plurality of second cells in step (3) is increased, wherein the interval between adjacent gradients is 10h-15h, for example, it can be 10h, 11h, 12h, 13h, 14h or 15h, but is not limited to the listed values, and other unlisted values within the range are also applicable.
[0051] The adjacent gradient interval of the immersion time in this invention is 10h-15h. For example, when the gradient interval is 12h, the immersion time of several second cells can be 12h, 24h, 36h and 48h respectively, and so on.
[0052] In one specific implementation, the fact that the film-forming peak area no longer increases in step (4) means that as the gradient of immersion time increases, the difference between the film-forming peak area at immersion time T2 and the film-forming peak area at immersion time T1 is ≤0.003, for example, it can be 0.003, 0.002, 0.001 or 0, where T2 is the immersion time after T1.
[0053] In this invention, T0 is the previous gradient of T1. For example, when the immersion times of several second cells are 12h, 24h, 36h and 48h respectively, if T1 is 36h, then T0 is 24h.
[0054] In one specific embodiment, the transformation described in steps (4) and (5) each independently includes the following steps:
[0055] The cells to be formed undergo their first charge under external pressure, followed by a first resting period after the first charge is completed.
[0056] After the first settling period, a second charge is performed, and after the second charge is performed, a second settling period is performed.
[0057] After the second settling period, a third charging process is initiated, and the formation process ends after the third charging process.
[0058] In one specific embodiment, the applied pressure is 250 kgf-350 kgf, for example, it can be 250 kgf, 275 kgf, 300 kgf, 325 kgf or 350 kgf, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0059] In one specific embodiment, the charging rate of the third charge is greater than the charging rate of the second charge.
[0060] In one specific embodiment, the charging rate of the second charge is greater than the charging rate of the first charge.
[0061] In one specific embodiment, the charging rate of the first charge is 0.04C-0.06C, for example, 0.04C, 0.05C or 0.06C, and the charging time is 55min-65min, for example, 55min, 57min, 59min, 61min, 63min or 65min, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0062] In one specific embodiment, the charging rate of the second charge is 0.08C-0.12C, for example, it can be 0.08C, 0.09C, 0.1C, 0.11C or 0.12C, and the charging time is 55min-65min, for example, it can be 55min, 57min, 59min, 61min, 63min or 65min, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0063] In one specific embodiment, the charging rate of the third charge is 0.18C-0.22C, for example, 0.18C, 0.19C, 0.20C, 0.21C or 0.22C, and the charging time is 55min-65min, for example, 55min, 57min, 59min, 61min, 63min or 65min, but not limited to the listed values. Other unlisted values within the range are also applicable.
[0064] In one specific embodiment, the first settling time is 8-15 minutes, for example, it can be 8 minutes, 10 minutes, 12 minutes, 14 minutes or 15 minutes, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0065] In one specific embodiment, the second settling time is 2-5 minutes, for example, it can be 2 minutes, 3 minutes, 4 minutes or 5 minutes, but is not limited to the listed values. Other unlisted values within the range are also applicable.
[0066] The technical solution of the present invention will be further illustrated below through specific embodiments.
[0067] The battery cell used in Example 1 is a 314Ah lithium iron phosphate battery cell, and the electrolyte additive used is VC (ethylene carbonate).
[0068] The cycling performance in Example 1 was achieved by cycling 8000 times at 25°C under 0.5P charge-discharge conditions, and the capacity retention rate was recorded.
[0069] In Example 1, the area of the film-forming peak was obtained by collecting the area of the characteristic peak corresponding to the dQ / dV curve through the formation equipment program.
[0070] The formation method described in Example 1 includes the following steps:
[0071] (1) Fix the battery cell in the restraint tray and apply a pressure of 300 kgf.
[0072] (2) Charge with a 0.05C current for 60 minutes, then let stand for 10 minutes;
[0073] (3) Charge with 0.1C current for 60 minutes, then let stand for 3 minutes;
[0074] (4) After charging with a 0.2C current for 60 minutes, the formation is completed.
[0075] Example 1
[0076] This embodiment provides a method for determining the wetting effect of a battery cell, the method comprising the following steps:
[0077] Battery cells A1, A2, A3, and A4 are provided. The VC content and electrolyte wetting time of the electrolytes of battery cells A1, A2, A3, and A4 are shown in Table 1.
[0078] Cells A1, A2, A3, and A4 were formed separately, and dQ / dV curves were acquired. The VC film-forming peak area was calculated. Then, the capacity retention of cells A1, A2, A3, and A4 after 8000 cycles was tested. The VC film-forming peak area and test results are shown in Table 1.
[0079] Table 1
[0080]
[0081] According to Table 1, the minimum amount of VC added to maintain a capacity retention rate of over 70% after 8000 cycles is 2.5 wt%, which means that the minimum content of VC in the electrolyte, M1, is 2.5 wt%.
[0082] An electrolyte with a VC content of 2.5 wt% was injected into cells B1, B2, B3, and B4, respectively. Cells B1, B2, B3, and B4 were immersed for 12 h, 24 h, 36 h, and 48 h, respectively. Formation was then performed on cells B1, B2, B3, and B4, and dQ / dV curves were collected. The peak area of the VC film formation was calculated. The dQ / dV curve of cell B1 is shown below. Figure 1 The above, Figure 1 The mid-peak is the characteristic peak of VC film formation; then the capacity retention of cells B1, B2, B3 and B4 after 8000 cycles was tested respectively.
[0083] The amount of VC added to the electrolyte, the electrolyte wetting time, the capacity retention rate after 8000 cycles, and the VC film-forming peak area for cells B1, B2, B3, and B4 are shown in Table 2.
[0084] Table 2
[0085]
[0086] Table 2 shows that when the immersion time is 36h, the corresponding VC film-forming peak area is basically equal to that of the next gradient (48h) (difference of 0.003). Therefore, when the film-forming peak area no longer increases, and the capacity retention rate is above 70% after 8000 cycles, the electrolyte immersion time T1 is 36h. Therefore, an electrolyte with a VC content of 2.5wt% and an immersion time of 36h are selected as the process conditions. Under these conditions, the film-forming peak area of the cell under test is 0.107. Therefore, when the VC film-forming peak area of the cell under test is ≥0.107, the immersion is qualified; when the VC film-forming peak area of the cell under test is <0.107, the immersion is unqualified, and its cycle life will not meet the requirement of a capacity retention rate above 70% after 8000 cycles.
[0087] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.
Claims
1. A method for judging the wetting effect of a battery cell, characterized in that, The method includes the following steps: (1) Provide a plurality of first cells, wherein the electrolyte of the plurality of first cells contains different amounts of additives; (2) Test the first cells and determine the minimum content of additive in the electrolyte based on the test results. The minimum content is recorded as M1. (3) Provide a plurality of second cells, wherein the content of additives in the electrolyte of the plurality of second cells is M1, and the immersion time gradient of the electrolyte of the plurality of second cells varies. (4) Form the plurality of second cells, and then collect the dQ / dV curve of the formed second cells, calculate the film-forming peak area of the additive in the second cells, and when the film-forming peak area no longer increases, the corresponding electrolyte wetting time is recorded as T1. (5) Inject the electrolyte containing additive M1 into several third cells, immerse them for T1 time and then perform formation. Then collect the dQ / dV curve of the third cell after formation, calculate the film-forming peak area of the additive in the third cell, and record the average value of the film-forming peak area of all third cells as A1. If the film-forming peak area corresponding to the battery cell under test is ≥ A1, then the wetting is qualified; if the film-forming peak area corresponding to the battery cell under test is < A1, then the wetting is unqualified.
2. The method according to claim 1, characterized in that, The additives mentioned in step (1) include any one or a combination of at least two of DTD, VC, EC or AMSD; And / or, step (2) of testing the plurality of first cells includes testing the cycle performance of the plurality of first cells.
3. The method according to claim 2, characterized in that, The method for determining the minimum content of additives in the electrolyte in step (2) is: the minimum content of additives when the 8000-cycle life obtained by the test of the first cells is above 70%.
4. The method according to claim 1 or 2, characterized in that, In step (3), the electrolyte immersion time gradient of the several second cells increases, wherein the interval between adjacent gradients is 10h-15h.
5. The method according to claim 1 or 2, characterized in that, The statement in step (4) that the film-forming peak area no longer increases means that as the immersion time gradient increases, the difference between the film-forming peak area at immersion time T2 and the film-forming peak area at immersion time T1 is ≤0.003, where T2 is the immersion time after T1.
6. The method according to claim 1 or 2, characterized in that, The transformations described in steps (4) and (5) each independently include the following steps: The cells to be formed undergo their first charge under external pressure, followed by a first resting period after the first charge is completed. After the first settling period, a second charge is performed, and after the second charge is performed, a second settling period is performed. After the second settling period, a third charging process is initiated, and the formation process ends after the third charging process.
7. The method according to claim 6, characterized in that, The applied pressure is 250 kgf-350 kgf.
8. The method according to claim 6, characterized in that, The charging rate of the third charge is greater than the charging rate of the second charge; And / or, the charging rate of the second charge is greater than the charging rate of the first charge.
9. The method according to claim 6, characterized in that, The first charge has a charging rate of 0.04C-0.06C and a charging time of 55min-65min; And / or, the second charge has a charging rate of 0.08C-0.12C and a charging time of 55min-65min; And / or, the third charge has a charging rate of 0.18C-0.22C and a charging time of 55min-65min.
10. The method according to claim 6, characterized in that, The first settling time is 8-15 minutes; And / or, the second settling time is 2-5 minutes.