Method for rapidly predicting influence of formation process on cycle life

Abstract

The invention discloses a method for rapidly predicting the influence of a formation process on the cycle life, and relates to the technical field of battery processing, according to the method, a pulse power test is integrated through production line formation and capacity grading equipment, discharge pulses are applied to a sample lithium battery according to different charge state intervals, the charge state resistance is rapidly obtained, and detection can be completed within tens of seconds. And by integrating the correlation between the cycle life data and the resistance value in the state of charge, the obtained correlation model can show that the state-of-charge resistance has high sensitivity to the lithium loss in the formation process in the low state of charge, so that the lithium battery to be detected can be detected by comparing the state-of-charge resistance values of the lithium battery to be detected in different formation processes. The method does not need to add equipment, does not interfere with the rhythm of a production line, is shorter in single detection time consumption, avoids the long-period problem of traditional capacity attenuation monitoring, and can improve the life prediction efficiency by hundreds of times.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery processing, and in particular relates to a method for rapidly predicting the influence of a formation process on cycle life. Background Art

[0002] The lithium battery formation process is the activation process during the first charge. It primarily uses a specific current to induce electrochemical reactions between the active materials in the positive and negative electrodes, forming a solid electrolyte interface (SEI) on the surface of the negative electrode. This SEI allows lithium ions to pass freely but isolates electrons, minimizing side reactions between the electrolyte and the negative electrode. It is crucial for the battery's cycle life, capacity utilization, and safety. Formation equipment consumes approximately 40% of the total energy consumption of a production line, making it one of the most energy-intensive steps in lithium battery production. Improving formation speed can significantly reduce lithium battery manufacturing costs. The cycle life of a lithium battery can be directly evaluated by the quality of the formation process. However, in actual production, cycle life testing is typically predicted using characterization techniques such as volume change detection, impedance spectroscopy, acoustic spectroscopy, and X-ray tomography. However, these testing methods are expensive and time-consuming, requiring months or even years to complete, making them unsuitable for large-scale production. Clearly, existing technologies have significant shortcomings in rapidly, accurately, and cost-effectively predicting the impact of the formation process on cycle life using existing production line testing equipment. An innovative solution that overcomes these limitations is urgently needed. Summary of the Invention

[0003] In view of the defects in the prior art, the present invention provides a method for quickly predicting the impact of the formation process on the cycle life to solve the above technical problems.

[0004] A method for quickly predicting the impact of formation process on cycle life includes the following:

[0005] For the lithium battery to be tested, at least one pulse power test is performed during the capacity formation stage to measure its resistance value at at least one predetermined state of charge;

[0006] Pre-establishing a correlation model, wherein the correlation model represents a corresponding relationship between a resistance value measured at at least one predetermined state of charge and a cycle life of the lithium battery;

[0007] Based on the correlation model and the resistance value of the lithium battery to be tested, the cycle life of the lithium battery to be tested is predicted.

[0008] Preferably, the process of establishing the association model is:

[0009] Performing a pulse power test on at least one sample lithium battery that has completed a formation process to measure the resistance value of the sample lithium battery under at least one predetermined state of charge;

[0010] Performing a cycle life test on the at least one sample lithium battery to obtain cycle life data thereof;

[0011] A correlation between the cycle life data and the resistance value at the state of charge is determined, and a correlation model between the resistance value at at least one predetermined state of charge and the cycle life is established.

[0012] Preferably, the pulse power test is performed on at least one sample lithium battery after the formation process is completed, and the resistance value of the sample lithium battery under at least one predetermined state of charge is measured, which specifically includes the following steps:

[0013] At room temperature,

[0014] After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds, and the resistance in the first state of charge was calculated by sampling at 0.1 seconds.

[0015] After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds. After standing for 1 hour, the sample lithium battery was discharged at 1C for 6 minutes. After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds. The resistance in the second state of charge was calculated at 0.1s.

[0016] After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds, and the cycle was repeated until the state of charge dropped to 10%. After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds, and the resistance in the third state of charge was calculated by sampling at 0.1 seconds.

[0017] After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds. After standing for 1 hour, the sample lithium battery was discharged at 1C for 1.2 minutes. After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds. The resistance in the fourth state of charge was calculated at 0.1 seconds.

[0018] After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds. After standing for 1 hour, the sample lithium battery was discharged at 1C for 1.2 minutes. After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds. The resistance in the fifth state of charge was calculated at 0.1s.

[0019] After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds. After standing for 1 hour, the sample lithium battery was discharged at 1C for 1.2 minutes. After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds. The resistance in the sixth state of charge was measured every 0.1 seconds. After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds.

[0020] Preferably, when the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery completes the formation process through the following steps:

[0021] First pre-charge: charging current 0.05C, charging time 60min;

[0022] Second pre-charge: charging current 0.1C, charging time 70min;

[0023] Constant current charging: charging current 0.5C, charging time 100min;

[0024] Constant voltage charging: charging current 0.5C, charging time 60min.

[0025] Preferably, when the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery completes the formation process through the following steps:

[0026] Pre-charge: charging current 0.1C, charging time 100min;

[0027] Constant current charging: charging current 0.5C, charging time 100min;

[0028] Constant voltage charging: charging current 0.5C, charging time 60min.

[0029] Preferably, when the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery completes the formation process through the following steps:

[0030] Pre-charge: charging current 0.03C, charging time 320min;

[0031] Constant current charging: charging current 0.5C, charging time 100min;

[0032] Constant voltage charging: charging current 0.5C, charging time 60min.

[0033] Preferably, when the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery completes the formation process through the following steps:

[0034] First pre-charge: charging current 0.05C, charging time 60min;

[0035] Second pre-charge: charging current 0.1C, charging time 30min;

[0036] Constant current charging: charging current 0.2C, charging time 270min;

[0037] Constant voltage charging: charging current 0.3C, charging time 90min.

[0038] Preferably, when the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery completes the formation process through the following steps:

[0039] Pre-charge: charging current 0.1C, charging time 60min;

[0040] Constant current charging: charging current 0.2C, charging time 270min;

[0041] Constant voltage charging: charging current 0.3C, charging time 90min.

[0042] Preferably, when the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery completes the formation process through the following steps:

[0043] Pre-charge: charging current 0.03C, charging time 210min;

[0044] Constant current charging: charging current 0.2C, charging time 270min;

[0045] Constant voltage charging: charging current 0.3C, charging time 90min.

[0046] Preferably, when performing a cycle life test on the at least one sample lithium battery, the following steps are specifically included:

[0047] At room temperature, the sample lithium battery was charged to 3650mV at a constant current and constant voltage of 1C, with a cut-off current of 0.01C, and left for 10 minutes.

[0048] Discharge the sample lithium battery at 1C to 2000mV and leave it for 20 minutes;

[0049] The above steps are repeated until the capacity retention rate of the sample lithium battery reaches 80%, and then the cycle life test is terminated.

[0050] Preferably, when performing a cycle life test on the at least one sample lithium battery, the following steps are specifically included:

[0051] At room temperature,

[0052] When the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery is charged at a constant current and constant voltage of 1C to 4200mV, with a cut-off current of 0.01C, and left for 10 minutes. The sample lithium battery is discharged at 1C to 3000mV and left for 20 minutes;

[0053] When the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery is charged at a constant current and constant voltage of 1C to 3650mV, with a cut-off current of 0.01C, and left for 10 minutes; the sample lithium battery is discharged at 1C to 2000mV and left for 20 minutes;

[0054] The constant current and constant voltage charging and discharging steps are repeated until the capacity retention rate of the sample lithium battery reaches 80%, and then the cycle life test is terminated.

[0055] The beneficial effects of the present invention are as follows: by integrating pulse power testing with the production line capacity formation equipment, a discharge pulse is applied to the sample lithium battery for different state of charge intervals, the state of charge resistance is quickly obtained, and the test can be completed within tens of seconds. And by integrating the correlation between the cycle life data and the resistance value under the state of charge, a correlation model is obtained, which shows that the state of charge resistance is highly sensitive to lithium loss during the formation process at a low state of charge. A lower state of charge resistance value means that a more effective passivation SEI film is formed during the formation process, which indicates a longer cycle life. Therefore, for the lithium battery to be tested, by comparing its state of charge resistance value under different formation processes, its quality can be quickly and accurately evaluated. Compared with traditional cycle life tests that take months or even years, and rapid characterization technologies that take a long time and are not suitable for production line use, this method does not require new equipment, does not interfere with the production line rhythm, takes less time for a single test, and avoids the long cycle problem of traditional capacity decay monitoring. It can increase the efficiency of life prediction by a hundred times, and provide second-level feedback for process optimization, which can significantly reduce R&D and quality control costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0057] Figure 1 A flow chart of a method for rapidly predicting the effect of a formation process on cycle life provided by the present invention;

[0058] Figure 2 A linear fitting diagram of the state of charge and cycle life of an NCM system lithium battery according to a method for quickly predicting the effect of formation process on cycle life provided by the present invention;

[0059] Figure 3 A linear fitting diagram of the state of charge and cycle life of an LFP system lithium battery, which is a method for quickly predicting the impact of formation process on cycle life provided by the present invention. DETAILED DESCRIPTION

[0060] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0061] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention.

[0062] The embodiments of the invention are described in detail below with reference to the accompanying drawings.

[0063] like Figure 1 As shown in the figure, a method for quickly predicting the impact of the formation process on the cycle life includes the following:

[0064] For the lithium battery to be tested, at least one pulse power test is performed during the capacity formation stage to measure its resistance value at at least one predetermined state of charge;

[0065] Pre-establishing a correlation model, wherein the correlation model represents a corresponding relationship between a resistance value measured at at least one predetermined state of charge and a cycle life of the lithium battery;

[0066] Based on the correlation model and the resistance value of the lithium battery to be tested, the cycle life of the lithium battery to be tested is predicted.

[0067] This solution can screen out resistance indicators with a strong linear correlation with life by obtaining the corresponding relationship between the resistance under different states of charge and the actual cycle life test results, and establish a correlation model. After the correlation model is established, for the lithium batteries to be tested in subsequent production, it is only necessary to use existing equipment to measure their corresponding state of charge resistance during the composition and capacity stage, and then substitute this relationship to quickly predict their potential cycle life.

[0068] More specifically, the process of establishing the association model is:

[0069] Performing a pulse power test on at least one sample lithium battery that has completed the formation process to measure the resistance value of the sample lithium battery under at least one predetermined state of charge;

[0070] Performing a cycle life test on at least one sample lithium battery to obtain cycle life data thereof;

[0071] A correlation between the cycle life data and the resistance value at the state of charge is determined, and a correlation model between the resistance value at at least one predetermined state of charge and the cycle life is established.

[0072] Among them, the pulse power test adopted in this scheme is a hybrid pulse power characteristic test, and the state-of-charge resistance is obtained using Ohm's law. Specifically, the linear regression equation of Minitab software is used to establish a correlation model, in which the response is "cycle life data" and the predicted variable is "resistance value under charge state". Minitab software is used to automatically generate a fitting equation for the actual cycle data of the production line and the resistance value under low charge state.

[0073] More specifically, after the formation process is completed, a pulse power test is performed on at least one sample lithium battery to measure the resistance value of the sample lithium battery at at least one predetermined state of charge, specifically including the following steps:

[0074] At room temperature,

[0075] After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds, and the resistance in the first state of charge was calculated by sampling at 0.1 seconds.

[0076] After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds. After standing for 1 hour, the sample lithium battery was discharged at 1C for 6 minutes. After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds. The resistance in the second state of charge was calculated at 0.1s.

[0077] After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds, and the cycle was repeated until the state of charge dropped to 10%. After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds, and the resistance in the third state of charge was calculated by sampling at 0.1 seconds.

[0078] After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds. After standing for 1 hour, the sample lithium battery was discharged at 1C for 1.2 minutes. After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds. The resistance in the fourth state of charge was calculated at 0.1 seconds.

[0079] After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds. After standing for 1 hour, the sample lithium battery was discharged at 1C for 1.2 minutes. After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds. The resistance in the fifth state of charge was calculated at 0.1s.

[0080] After standing for 40 seconds, the sample lithium battery was charged at 2.25C for 10 seconds. After standing for 1 hour, the sample lithium battery was discharged at 1C for 1.2 minutes. After standing for 1 hour, the sample lithium battery was discharged at 3C for 10 seconds. The resistance in the sixth state of charge was calculated at 0.1s.

[0081] At this time, the first state of charge resistance is the resistance of the sample lithium battery at 100% state of charge; the second state of charge resistance is the resistance of the sample lithium battery at 90% state of charge; the third state of charge resistance is the resistance of the sample lithium battery at 10% state of charge; the fourth state of charge resistance is the resistance of the sample lithium battery at 8% state of charge; the fifth state of charge resistance is the resistance of the sample lithium battery at 6% state of charge; the fifth state of charge resistance is the resistance of the sample lithium battery at 4% state of charge; the sampling point is taken at 0.1s here, which specifically means that during the charging process of the sample lithium battery, data is collected every 0.1s.

[0082] In Example 1, more specifically, when the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery completes the formation process through the following steps:

[0083] First pre-charge: charging current 0.05C, charging time 60min;

[0084] Second pre-charge: charging current 0.1C, charging time 70min;

[0085] Constant current charging: charging current 0.5C, charging time 100min;

[0086] Constant voltage charging: charging current 0.5C, charging time 60min.

[0087] By adopting different formation processes, a stable SEI film can be generated in the shortest possible time for different positive electrode materials, thereby improving the cycle life.

[0088] In Example 2, more specifically, when the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery completes the formation process through the following steps:

[0089] Pre-charge: charging current 0.1C, charging time 100min;

[0090] Constant current charging: charging current 0.5C, charging time 100min;

[0091] Constant voltage charging: charging current 0.5C, charging time 60min.

[0092] In Example 3, more specifically, when the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery completes the formation process through the following steps:

[0093] Pre-charge: charging current 0.03C, charging time 320min;

[0094] Constant current charging: charging current 0.5C, charging time 100min;

[0095] Constant voltage charging: charging current 0.5C, charging time 60min.

[0096] In Example 4, more specifically, when the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery completes the formation process through the following steps:

[0097] First pre-charge: charging current 0.05C, charging time 60min;

[0098] Second pre-charge: charging current 0.1C, charging time 30min;

[0099] Constant current charging: charging current 0.2C, charging time 270min;

[0100] Constant voltage charging: charging current 0.3C, charging time 90min.

[0101] In Example 5, more specifically, when the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery completes the formation process through the following steps:

[0102] Pre-charge: charging current 0.1C, charging time 60min;

[0103] Constant current charging: charging current 0.2C, charging time 270min;

[0104] Constant voltage charging: charging current 0.3C, charging time 90min.

[0105] In Example 6, more specifically, when the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery completes the formation process through the following steps:

[0106] Pre-charge: charging current 0.03C, charging time 210min;

[0107] Constant current charging: charging current 0.2C, charging time 270min;

[0108] Constant voltage charging: charging current 0.3C, charging time 90min.

[0109] Using different implementations

[0110] The pulse power test results of each embodiment are as follows:

[0111] 100% state of charge (unit: mΩ)

[0112] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 1 23.13 23.03 23.19 9.83 9.77 9.80 2 24.27 22.79 23.43 10.14 9.80 9.92 3 24.53 23.88 23.66 9.96 9.74 9.80 4 24.23 22.81 23.02 9.78 9.56 9.81 5 23.63 23.90 23.61 9.93 9.77 10.02 6 23.11 23.50 24.03 10.06 9.88 10.04 7 25.34 23.38 23.20 9.79 9.62 9.85 8 24.38 23.44 23.47 9.92 9.59 9.73 9 23.51 23.38 24.09 9.97 9.73 9.76 10 24.00 23.06 24.03 9.89 9.60 10.05

[0113] 90% state of charge (unit: mΩ)

[0114] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 1 61.17 63.74 60.70 9.91 9.86 9.99 2 61.87 63.91 61.13 9.28 10.11 9.74 3 61.50 64.50 62.93 9.94 9.82 10.16 4 62.17 61.64 60.75 9.83 9.80 10.13 5 59.56 63.15 61.37 10.02 10.40 9.88 6 59.58 63.47 61.87 9.52 10.52 10.25 7 62.08 61.52 62.55 9.60 9.86 10.03 8 60.70 63.92 62.88 9.50 10.06 9.90 9 61.59 61.62 60.51 9.36 10.46 9.99 10 24.14 23.98 25.04 5.77 5.57 5.78

[0115] 10% state of charge (unit: mΩ)

[0116] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 1 61.17 63.74 60.70 9.91 9.86 9.99 2 61.87 63.91 61.13 9.28 10.11 9.74 3 61.50 64.50 62.93 9.94 9.82 10.16 4 62.17 61.64 60.75 9.83 9.80 10.13 5 59.56 63.15 61.37 10.02 10.40 9.88 6 59.58 63.47 61.87 9.52 10.52 10.25 7 62.08 61.52 62.55 9.60 9.86 10.03 8 60.70 63.92 62.88 9.50 10.06 9.90 9 61.59 61.62 60.51 9.36 10.46 9.99 10 60.22 64.36 60.61 10.02 10.20 10.25

[0117] 8% state of charge (unit: mΩ)

[0118] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 1 75.66 80.75 76.11 12.38 12.91 12.69 2 73.59 79.88 76.46 12.24 12.74 12.46 3 74.00 80.42 77.74 12.15 12.93 12.75 4 74.70 78.98 76.10 12.18 12.99 12.73 5 74.18 80.64 77.37 12.15 12.89 12.48 6 75.86 78.65 78.39 12.18 12.68 12.66 7 75.80 80.47 77.87 12.29 12.63 12.61 8 75.97 79.99 78.36 12.27 12.72 12.68 9 74.66 80.53 77.09 12.30 12.98 12.61 10 74.57 79.21 77.19 12.20 12.90 12.67

[0119] 6% state of charge (unit: mΩ)

[0120] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 1 99.54 107.23 104.99 16.46 17.20 16.86 2 98.88 106.47 104.77 16.26 17.14 16.77 3 100.19 105.94 102.96 16.46 17.28 16.98 4 100.63 107.90 102.70 16.41 17.24 16.94 5 100.38 107.45 103.59 16.20 17.36 16.79 6 99.57 105.81 102.91 16.41 17.26 16.91 7 100.35 107.64 103.51 16.32 17.32 16.75 8 99.20 105.75 104.44 16.30 17.26 17.06 9 99.73 105.92 104.96 16.25 17.20 16.84 10 99.47 105.70 102.95 16.20 17.37 16.71

[0121] 4% state of charge (unit: mΩ)

[0122] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 1 150.63 159.41 155.16 24.32 25.64 25.08 2 150.81 160.04 155.21 24.23 25.76 25.29 3 148.96 158.55 155.71 24.58 25.51 25.00 4 149.53 160.84 154.51 24.49 25.59 25.00 5 150.02 159.43 154.79 24.25 25.76 25.04 6 150.14 158.93 154.86 24.45 25.59 25.20 7 150.56 159.97 155.96 24.39 25.56 25.20 8 150.57 159.87 154.37 24.59 25.55 25.14 9 149.77 160.49 155.56 24.48 25.78 25.33 10 150.50 159.79 155.44 24.58 25.82 25.00

[0123] More specifically, when performing a cycle life test on a charged sample lithium battery, the following steps are specifically included:

[0124] At room temperature,

[0125] When the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery is charged at a constant current and constant voltage of 1C to 4200mV, the cut-off current is 0.01C, and the battery is left for 10 minutes. The sample lithium battery is discharged at 1C to 3000mV and left for 20 minutes.

[0126] When the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery is charged at a constant current and constant voltage of 1C to 3650mV, with a cut-off current of 0.01C, and left for 10 minutes; the sample lithium battery is discharged at 1C to 2000mV and left for 20 minutes;

[0127] The constant current and constant voltage charging and discharging steps are repeated until the capacity retention rate of the sample lithium battery reaches 80%, and then the cycle life test is terminated.

[0128] After collecting the sixth state of charge resistance, let it stand for 40 seconds, charge the sample lithium battery at 2.25C for 10 seconds, let it stand for 1 hour, and then charge it according to the shipping requirements to make the sample lithium battery reach the predetermined state of charge. Select the battery according to actual needs for cycle life testing.

[0129] like Figure 2 As shown in the table, the relationship between 4% state of charge and cycle life of NCM system:

[0130] R (mΩ) Cycle life Examples 2-4 160.84 621 Examples 2-9 160.49 625 Example 2-2 160.04 654 Examples 2-7 159.97 683 Examples 2-8 159.87 692 Example 2-10 159.79 717 Examples 2-5 159.43 717 Example 2-1 159.41 721 Examples 2-6 158.93 724 Example 2-3 158.55 742 Examples 3-7 155.96 756 Example 3-3 155.71 765 Examples 3-9 155.56 770 Examples 3-10 155.44 776 Example 3-2 155.21 787 Example 3-1 155.16 818 Examples 3-6 154.86 824 Examples 3-5 154.79 824 Examples 3-4 154.51 826 Examples 3-8 154.37 832 Example 1-2 150.81 842 Example 1-1 150.63 853 Examples 1-8 150.57 866 Examples 1-7 150.56 868 Examples 1-10 150.50 892 Examples 1-6 150.14 904 Examples 1-5 150.02 961 Examples 1-9 149.77 965 Examples 1-4 149.53 997 Examples 1-3 148.96 998

[0131] like Figure 3 As shown in the table, the relationship between 4% state of charge and cycle life of the LFP system:

[0132] R (mΩ) Cycle life Examples 5-10 25.82 1518 Examples 5-9 25.78 1538 Example 5-2 25.76 1559 Example 5-5 25.76 1570 Example 5-1 25.64 1607 Examples 5-6 25.59 1629 Example 5-4 25.59 1659 Examples 5-7 25.56 1665 Examples 5-8 25.55 1671 Example 5-3 25.51 1689 Examples 6-9 25.33 1705 Example 6-2 25.29 1725 Examples 6-7 25.20 1732 Example 6-6 25.20 1816 Examples 6-8 25.14 1901 Example 6-1 25.08 1933 Example 6-5 25.04 1952 Examples 6-10 25.00 1987 Example 6-3 25.00 2094 Example 6-4 25.00 2268 Examples 4-8 24.59 2322 Examples 4-10 24.58 2388 Example 4-3 24.58 2396 Example 4-4 24.49 2416 Examples 4-9 24.48 2419 Examples 4-6 24.45 2434 Examples 4-7 24.39 2439 Example 4-1 24.32 2443 Examples 4-5 24.25 2457 Example 4-2 24.23 2497

[0133] The room temperature here is 25±2℃.

[0134] It can be seen from the linear fitting graph that the room temperature cycle life test of each embodiment is carried out, and it is found that the cycle life of each embodiment is linearly correlated with the resistance at 4% state of charge. As the state of charge decreases, the state of charge resistance generally shows an upward trend, and the distinction between the state of charge resistance of different formation processes becomes more and more obvious. When the state of charge is reduced to within 10%, there is a significant difference in the state of charge resistance of different formation processes, and the lower the state of charge, the more obvious the difference, and the smaller the state of charge resistance, the better the cycle life;

[0135] When verifying the formation process of the lithium battery to be tested on the mass production line, the resistance at 4% state of charge can be tested during the formation and capacity adjustment. The cycle life of the new formation process can be predicted by combining the resistance data at 4% state of charge of the original process and the corresponding cycle life test data.

[0136] This method is applicable to both NCM and LFP systems, and is also suitable for predicting cycle life between mass production batches.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A method for rapidly predicting the effect of formation process on cycle life, characterized by: For the lithium battery to be tested, at least one pulse power test is performed during the capacity formation stage to measure its resistance value at at least one predetermined state of charge; Pre-establishing a correlation model, wherein the correlation model represents a corresponding relationship between a resistance value measured at at least one predetermined state of charge and a cycle life of the lithium battery; Based on the correlation model and the resistance value of the lithium battery to be tested, the cycle life of the lithium battery to be tested is predicted.

2. The method for rapidly predicting the effect of formation process on cycle life according to claim 1, characterized in that: The process of establishing the correlation model is as follows: performing a pulse power test on at least one sample lithium battery that has completed the formation process to measure the resistance value of the sample lithium battery under at least one predetermined state of charge; performing a cycle life test on the at least one sample lithium battery to obtain its cycle life data; determining the correlation between the cycle life data and the resistance value under the state of charge, and establishing a correlation model between the resistance value under at least one predetermined state of charge and the cycle life.

3. The method for rapidly predicting the effect of formation process on cycle life according to claim 2, characterized in that: The method comprises the following steps: standing at room temperature for 1 hour, discharging the sample lithium battery at 3C for 10 seconds, sampling points at 0.1 seconds and calculating the first state of charge resistance; standing at room temperature for 40 seconds, charging the sample lithium battery at 2.25C for 10 seconds, standing at room temperature for 1 hour, discharging the sample lithium battery at 1C for 6 minutes, standing at room temperature for 1 hour, discharging the sample lithium battery at 3C for 10 seconds, sampling points at 0.1 seconds and calculating the second state of charge resistance; standing at room temperature for 40 seconds, charging the sample lithium battery at 2.25C for 10 seconds, and calculating the second state of charge resistance; standing at room temperature for 1 hour, discharging the sample lithium battery at 3C for 10 seconds, sampling points at 0.1 seconds and calculating the second state of charge resistance; standing at room temperature for 40 seconds, discharging the sample lithium battery at 2.25C for 10 seconds, and calculating the second state of charge resistance; standing at room temperature for 1 hour, discharging the sample lithium battery at 3C for 10 seconds, sampling points at 0.1 seconds and calculating the third state of charge resistance; standing at room temperature for 40 seconds, The sample lithium battery was charged at 2.25C for 10s, and after standing for 1h, the sample lithium battery was discharged at 1C for 1.2min. After standing for 1h, the sample lithium battery was discharged at 3C for 10s, and points were sampled at 0.1s to calculate the fourth state of charge resistance; after standing for 40s, the sample lithium battery was charged at 2.25C for 10s, and after standing for 1h, the sample lithium battery was discharged at 1C for 1.2min. After standing for 1h, the sample lithium battery was discharged at 3C for 10s, and points were sampled at 0.1s to calculate the fifth state of charge resistance; after standing for 40s, the sample lithium battery was charged at 2.25C for 10s, and after standing for 1h, the sample lithium battery was discharged at 1C for 1.2min. After standing for 1h, the sample lithium battery was discharged at 3C for 10s, and points were sampled at 0.1s to calculate the sixth state of charge resistance. After standing for 40s, the sample lithium battery was charged at 2.25C for 10s.

4. The method for rapidly predicting the effect of formation process on cycle life according to claim 3, characterized in that: When the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery completes the formation process through the following steps: first pre-charging: charging current 0.05C, charging time 60min; second pre-charging: charging current 0.1C, charging time 70min; constant current charging: charging current 0.5C, charging time 100min; constant voltage charging: charging current 0.5C, charging time 60min.

5. The method for rapidly predicting the effect of formation process on cycle life according to claim 3, characterized in that: When the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery is subjected to the following steps to complete the formation process: pre-charging: charging current 0.1C, charging time 100 minutes; constant current charging: charging current 0.5C, charging time 100 minutes; constant voltage charging: charging current 0.5C, charging time 60 minutes.

6. The method for rapidly predicting the effect of formation process on cycle life according to claim 3, characterized in that: When the positive electrode of the sample lithium battery is an NCM system, the sample lithium battery completes the formation process through the following steps: pre-charging: charging current 0.03C, charging time 320min; constant current charging: charging current 0.5C, charging time 100min; constant voltage charging: charging current 0.5C, charging time 60min.

7. The method for rapidly predicting the effect of formation process on cycle life according to claim 3, characterized in that: When the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery completes the formation process through the following steps: first pre-charging: charging current 0.05C, charging time 60min; second pre-charging: charging current 0.1C, charging time 30min; constant current charging: charging current 0.2C, charging time 270min; constant voltage charging: charging current 0.3C, charging time 90min.

8. The method for rapidly predicting the effect of formation process on cycle life according to claim 3, characterized in that: When the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery completes the formation process through the following steps: pre-charging: charging current 0.1C, charging time 60min; constant current charging: charging current 0.2C, charging time 270min; constant voltage charging: charging current 0.3C, charging time 90min.

9. The method for rapidly predicting the effect of formation process on cycle life according to claim 3, characterized in that: When the positive electrode of the sample lithium battery is an LFP system, the sample lithium battery completes the formation process through the following steps: pre-charging: charging current 0.03C, charging time 210min; constant current charging: charging current 0.2C, charging time 270min; constant voltage charging: charging current 0.3C, charging time 90min.

10. The method for rapidly predicting the effect of formation process on cycle life according to any one of claims 4 to 9, characterized in that: When performing a cycle life test on the at least one sample lithium battery, specifically The method comprises the following steps: at room temperature, when the positive electrode of the sample lithium battery is an NCM system, charging the sample lithium battery to 4200mV at a constant current and constant voltage of 1C, with a cut-off current of 0.01C, and leaving it for 10 minutes; discharging the sample lithium battery to 3000mV at 1C, and leaving it for 20 minutes; when the positive electrode of the sample lithium battery is an LFP system, charging the sample lithium battery to 3650mV at a constant current and constant voltage of 1C, with a cut-off current of 0.01C, and leaving it for 10 minutes; discharging the sample lithium battery to 2000mV at 1C, and leaving it for 20 minutes; and cyclically performing the constant current and constant voltage charging and discharging steps until the capacity retention rate of the sample lithium battery reaches 80%, and then ending the cycle life test.

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