A method and system for detecting the failure time of a battery binder

Abstract

The present application relates to a battery binder failure time detection method and system, the detection method comprising the following steps: (1) soaking the pole piece in the electrolyte and placing it in a target temperature environment, detecting the peel strength of the pole piece corresponding to different soaking times, and obtaining a reference peel strength decay curve according to the peel strength of the pole piece corresponding to different soaking times; wherein the ordinate of the reference peel strength decay curve is the peel strength retention rate, and the abscissa is the soaking time; (2) detecting the peel strength of the pole piece of the fresh battery without cycling and the battery after cycling for a target number of times, and calculating to obtain a target peel strength retention rate; (3) calculating the failure time of the binder according to the target number of cycles, the target peel strength retention rate and the reference peel strength decay curve. The present application detects the failure of the binder in the battery through the pole piece, which can guide the design and selection of the battery binder; and has strong compatibility, and can be compatible with batch differences of the same battery through peel strength retention rate detection.

Description

Technical Field

[0001] This invention belongs to the field of analytical testing technology, specifically relating to a method and system for detecting the failure time of battery binders. Background Technology

[0002] The main function of binders in batteries is to bond active materials, conductive carbon, and current collectors, maintaining the stability of the electrode structure. Binder failure will lead to battery performance degradation and a significant drop in capacity. Therefore, predicting binder failure time is of great value for predicting battery cycle life and battery design.

[0003] Existing technologies mainly predict the overall lifespan of batteries. For example, patent document CN109581240B discloses a lithium-ion battery failure analysis method based on the AC impedance method. It analyzes the change in SEI film resistance by AC impedance spectroscopy (EIS) test to predict the short circuit state within the dendrites of the battery, and then evaluates the battery's lifespan and safety. However, it cannot analyze and predict the failure of the binder, making it difficult to guide the design and selection of subsequent battery binders. Summary of the Invention

[0004] Based on the aforementioned shortcomings and deficiencies in the existing technology, the purpose of this invention is to provide a method and system for detecting the failure time of battery binders.

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

[0006] A method for detecting the failure time of battery binder, wherein the binder is one of the constituent materials of the electrode sheet, and the detection method includes the following steps:

[0007] (1) The electrode is immersed in the electrolyte and placed in the target temperature environment. The peel strength of the electrode corresponding to different immersion times is detected, and the baseline peel strength decay curve is obtained based on the peel strength of the electrode corresponding to different immersion times. The vertical axis of the baseline peel strength decay curve is the peel strength retention rate, and the horizontal axis is the immersion time.

[0008] (2) Detect the peel strength of the electrodes of the uncycled fresh battery and the battery after the target number of cycles, and calculate the target peel strength retention rate;

[0009] (3) Calculate the failure time of the adhesive based on the target number of cycles, the target peel strength retention rate and the baseline peel strength decay curve.

[0010] As a preferred embodiment, the peel strength retention rate of the immersed electrode is the ratio of the peel strength of the immersed electrode to the original peel strength of the immersed and wetted electrode.

[0011] As a preferred embodiment, the target peel strength retention rate is the ratio of the peel strength of the electrode of the battery after a target number of cycles to the peel strength of the electrode of a fresh battery that has not been cycled.

[0012] As a preferred embodiment, the failure time of the adhesive is expressed as the number of adhesive failure cycles.

[0013] As a preferred embodiment, in step (1), the temperature of the target temperature environment is 0-90℃.

[0014] As a preferred embodiment, the temperature of the target temperature environment is 40-50℃.

[0015] As a preferred option, the electrode is a negative electrode.

[0016] As a preferred embodiment, the negative electrode active material of the negative electrode sheet is one or more of graphite, hard carbon, silicon carbide, and silicon oxide.

[0017] As a preferred option, the detection method includes:

[0018] Different electrodes and electrolytes were selected to test the failure time of the binder in different battery systems.

[0019] The present invention also provides a system for detecting the failure time of battery adhesives, using the detection method described in any of the preceding embodiments, the detection system comprising:

[0020] The detection module is used to detect the peel strength of the electrode corresponding to different immersion times, and also to detect the peel strength of the electrode of the uncycled fresh battery and the battery after the target number of cycles.

[0021] The fitting module is used to obtain the baseline peel strength decay curve based on the peel strength of the electrode corresponding to different soaking times;

[0022] The calculation module is used to calculate the target peel strength retention rate based on the peel strength of the electrodes of the uncycled fresh battery and the battery after the target number of cycles. It is also used to calculate the failure time of the adhesive based on the target number of cycles, the target peel strength retention rate, and the baseline peel strength decay curve.

[0023] Compared with the prior art, the beneficial effects of this invention are:

[0024] (1) This invention detects the failure of the binder in the battery by using electrode plates, which can guide the design and selection of subsequent battery binders;

[0025] (2) The present invention has strong compatibility. By testing the peel strength retention rate, it can be compatible with batch differences of the same battery.

[0026] (3) The present invention has a wide range of applications and can select different electrodes and electrolytes to detect the failure time of binders in different systems;

[0027] (4) The detection process of the present invention is simple to operate and has low cost. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the baseline peel strength decay curve of Embodiment 1 of the present invention;

[0029] Figure 2 This is a schematic diagram of the battery binder failure time detection system according to Embodiment 1 of the present invention. Detailed Implementation

[0030] To more clearly illustrate the embodiments of the present invention, specific implementation methods will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0031] Example 1:

[0032] The method for detecting the failure time of the battery adhesive in this embodiment includes:

[0033] Using lithium iron phosphate as the positive electrode active material to fabricate the positive electrode sheet;

[0034] Graphite is used as the negative electrode active material to make the negative electrode sheet;

[0035] The manufacturing processes for the aforementioned positive and negative electrode sheets can be referenced from existing technologies and will not be elaborated here. Both the positive and negative electrode sheets contain a binder.

[0036] The positive and negative electrode sheets are separated and wound together with a diaphragm, and then the tabs are welded to make a bare cell. The bare cell is then wrapped in a housing and packaged into a pre-assembled cell. After that, an electrolyte is injected into the pre-assembled cell and then sealed. The solvent used in the electrolyte is ethylene carbonate, propylene carbonate, and methyl ethyl carbonate, and the lithium salt is lithium hexafluorophosphate.

[0037] In this embodiment, the negative electrode sheet is immersed in the electrolyte and placed in a 45°C oven;

[0038] Samples were taken at 0, 1, 2, 3, 5, 7, 10 and 15 days respectively, cleaned with DMC (dimethyl carbonate) and dried, and the peel strength F of the dried electrode was tested. The results are shown in Table 1.

[0039] Table 1 Performance parameters of electrode sheets under different soaking times

[0040] Soaking time T (days) Peel strength F (N / m) Peel strength retention rate Y (%) 0 11.2 100.00 1 9.6 85.71 2 8.2 73.21 3 6.5 58.04 5 4.7 41.96 7 2.9 25.89 10 1.5 13.39 15 0 0.00

[0041] Among them, the peel strength of the electrode on day 0 is recorded as F0, which is used as the original peel strength of the electrode.

[0042] Peel strength retention rate Y = (F / F0) * 100%.

[0043] In this embodiment, the 0-day electrode is a soaked and moistened electrode. Generally, the soaking time is ≤1 minute, until it is moistened. In addition, the specific soaking time can be determined according to the actual sample, and may exceed 1 minute.

[0044] A baseline peel strength decay curve was obtained by plotting soaking time on the x-axis and peel strength retention rate on the y-axis, as shown below. Figure 1 As shown; where the intersection of the reference peel strength decay curve and the horizontal axis is (T0, 0), that is, the soaking time T0 corresponding to the reference peel strength decay curve in this embodiment when the peel strength retention rate is zero is 15 days, that is, the electrode peel strength retention rate is 0 after soaking for 15 days.

[0045] Then, negative electrode sheets from uncycled fresh batteries and batteries that had undergone 1000 cycles at 45°C were taken, cleaned and dried using DMC, and their peel strength was tested. The peel strength retention rate Y was calculated. * As shown in Table 2.

[0046] Table 2 Performance parameters of the negative electrode sheets of uncycled fresh batteries and batteries cyclically charged at 45°C for 1000 cycles.

[0047] Number of iterations N <![CDATA[Peeling strength F * (N / m)]]> <![CDATA[Peeling strength retention rate Y * (%)]]> 0 10.8 100 1000 8.6 79.63

[0048] Next, based on the peel strength retention rate Y * Find the corresponding point (T1, Y) in the baseline peel strength decay curve. * ),like Figure 1 As shown, specifically (1.5, 79.63).

[0049] The failure time of the adhesive is expressed by the number of adhesive failure cycles. Therefore, the number of adhesive failure cycles K = (T0 / T1) * N = (15 / 1.5) * 1000 = 10000, which means that the adhesive fails after approximately 10000 cycles at 45℃.

[0050] like Figure 2 As shown in the figure, this embodiment also provides a detection system for battery adhesive failure time, including a detection module, a fitting module and a calculation module.

[0051] Specifically, the detection module in this embodiment is used to detect the peel strength of the electrode corresponding to different immersion times, and also to detect the peel strength of the electrode of the uncycled fresh battery and the battery after the target number of cycles.

[0052] The fitting module in this embodiment is used to obtain the baseline peel strength decay curve based on the peel strength of the electrode corresponding to different soaking times.

[0053] The calculation module in this embodiment is used to calculate the target peel strength retention rate based on the peel strength of the electrodes of the uncycled fresh battery and the battery after the target number of cycles. It is also used to calculate the failure time of the adhesive based on the target number of cycles, the target peel strength retention rate, and the baseline peel strength decay curve.

[0054] The specific processing procedures for each of the above functional modules can be found in the detailed description in the detection method, and will not be repeated here.

[0055] Example 2:

[0056] The method for detecting the battery adhesive failure time in this embodiment differs from that in Embodiment 1 in that:

[0057] Different electrodes and electrolytes can be selected to test the failure time of binders in different battery systems, so as to comprehensively evaluate the performance of binders and facilitate the selection and improvement of subsequent binders.

[0058] Other steps can be found in Example 1.

[0059] Example 3:

[0060] The method for detecting the battery adhesive failure time in this embodiment differs from that in Embodiment 1 in that:

[0061] The target temperature environment can also be 0℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 75℃, 80℃, 90℃, etc., which can be determined according to the actual testing requirements;

[0062] In addition, the target number of cycles can be determined according to actual needs, such as 500 times, 1500 times, 3000 times, etc.

[0063] The negative electrode active material of the negative electrode sheet can also be hard carbon, silicon carbide or silicon oxide, or several of graphite, hard carbon, silicon carbide and silicon oxide; the specific choice depends on the actual application requirements.

[0064] Other steps can be found in Example 1.

[0065] The above description is merely a detailed explanation of preferred embodiments and principles of the present invention. For those skilled in the art, there may be changes in specific implementation methods based on the ideas provided by the present invention, and these changes should also be considered within the scope of protection of the present invention.

Claims

1. A method for detecting the failure time of a battery binder, wherein the binder is one of the constituent materials of the electrode sheet, characterized in that, The detection method includes the following steps: (1) The electrode is immersed in the electrolyte and placed in the target temperature environment. The peel strength of the electrode corresponding to different immersion times is detected, and the baseline peel strength decay curve is obtained based on the peel strength of the electrode corresponding to different immersion times. The vertical axis of the baseline peel strength decay curve is the peel strength retention rate, and the horizontal axis is the immersion time. (2) Detect the peel strength of the electrodes of the uncycled fresh battery and the battery after the target number of cycles, and calculate the target peel strength retention rate; (3) Calculate the failure time of the adhesive based on the target number of cycles, the target peel strength retention rate, and the baseline peel strength decay curve; In step (3), the failure time of the adhesive is represented by the number of adhesive failure cycles K: K = (T0 / T1) * N; Where T0 is the immersion time corresponding to the baseline peel strength decay curve when the peel strength retention rate is zero, T1 is the immersion time corresponding to the baseline peel strength decay curve when the peel strength retention rate is the target peel strength retention rate, and N is the target number of cycles for the battery.

2. The detection method according to claim 1, characterized in that, In step (1), the peel strength retention rate Y of the electrode after soaking for day i is... i for: Y i =(F i / F0)*100%; Among them, F i F0 represents the peel strength of the electrode after soaking for day i, F0 represents the original peel strength of the electrode before soaking, and i is a positive integer.

3. The detection method according to claim 1, characterized in that, In step (2), the target peel strength retention rate Y * for: Y * =(F N * / F0 * )*100%; Among them, F0 * F represents the peel strength of the electrode of a fresh, uncycled battery. N * The peel strength of the battery electrode after the target number of cycles N.

4. The detection method according to any one of claims 1-3, characterized in that, In step (1), the temperature of the target temperature environment is 30-90℃.

5. The detection method according to claim 4, characterized in that, The target temperature environment is 45°C.

6. The detection method according to any one of claims 1-3, characterized in that, The electrode is a negative electrode.

7. The detection method according to claim 6, characterized in that, The negative electrode active material of the negative electrode sheet is graphite.

8. The detection method according to any one of claims 1-3, characterized in that, include: Different electrodes and electrolytes were selected to test the failure time of the binder in different battery systems.

9. A system for detecting the failure time of battery adhesives, using the detection method as described in any one of claims 1-8, characterized in that, The detection system includes: The detection module is used to detect the peel strength of the electrode corresponding to different immersion times, and also to detect the peel strength of the electrode of the uncycled fresh battery and the battery after the target number of cycles. The fitting module is used to obtain the baseline peel strength decay curve based on the peel strength of the electrode corresponding to different soaking times; The calculation module is used to calculate the target peel strength retention rate based on the peel strength of the electrodes of the uncycled fresh battery and the battery after the target number of cycles. It is also used to calculate the failure time of the adhesive based on the target number of cycles, the target peel strength retention rate, and the baseline peel strength decay curve.

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