Method and apparatus for testing corrosion resistance of electrolytic copper foil for lithium ion battery

Abstract

The application discloses a kind of electrolytic copper foil corrosion resistance test method and device for lithium ion battery, belong to material performance test technical field, including the corrosion resistance test of electrolytic copper foil, obtains the test data of electrolytic copper foil in corrosion test, generates corrosion speed score;Obtain the corrosion state data of electrolytic copper foil in corrosion stagnation stage;According to the stagnation corrosion area and stagnation corrosion depth of electrolytic copper foil in corrosion stagnation time point, generate corrosion degree score;According to corrosion speed score and corrosion degree score, the corrosion resistance of electrolytic copper foil is classified;The application obtains the corrosion area and corrosion depth of electrolytic copper foil by carrying out corrosion resistance test to electrolytic copper foil, obtains corrosion start time and corrosion stagnation time, then combines the corrosion state of electrolytic copper foil after corrosion stagnation stage, comprehensively analyzes the corrosion resistance of electrolytic copper foil, to quantify the corrosion resistance of electrolytic copper foil, so that the test result of electrolytic copper foil corrosion resistance test is more comprehensive.

Description

Technical Field

[0001] This invention belongs to the field of material performance testing technology, and in particular relates to a method and apparatus for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries. Background Technology

[0002] Electrolytic copper foil, as the negative electrode current collector in lithium-ion batteries, plays a crucial role in electronic conductivity during the battery's charging and discharging process. It connects the negative electrode material (usually graphite) to the external circuitry of the battery, ensuring smooth current flow. In the working environment of lithium-ion batteries, electrolytic copper foil comes into contact with the electrolyte, and especially during battery cycling, it may experience corrosion. Corrosion not only affects the conductivity of the copper foil but can also lead to battery performance degradation and even safety issues. Therefore, copper foil needs to possess good corrosion resistance to prevent excessive corrosion during long-term use.

[0003] In existing technologies, the corrosion resistance testing methods for electrolytic copper foil include electrochemical testing, immersion testing, and salt spray testing. However, in existing testing methods, the corrosion assessment of copper foil mainly relies on a single static indicator, such as the final corrosion area or weight loss rate. The corrosion rate change process (such as corrosion initiation time and passivation film formation time) is not quantified, and the real-time degradation mechanism of the material in the battery electrolyte environment cannot be reflected, thus reducing the comprehensiveness of the test results of electrolytic copper foil in corrosion protection testing. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method and apparatus for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries, thus solving the aforementioned problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries, comprising the following steps:

[0006] The electrolytic copper foil was subjected to corrosion tests to obtain test data, including corrosion area, corrosion depth, corrosion start time, and corrosion stagnation time.

[0007] A corrosion rate score is generated based on the test data of electrolytic copper foil in the corrosion test;

[0008] Obtain corrosion state data of electrolytic copper foil during the corrosion stagnation stage; the corrosion state data includes the stagnation corrosion area and stagnation corrosion depth.

[0009] A corrosion severity score is generated based on the stagnant corrosion area and stagnant corrosion depth of the electrolytic copper foil at the corrosion stagnation time point.

[0010] The corrosion resistance of electrolytic copper foil is classified according to corrosion rate score and corrosion degree score;

[0011] The corrosion rate score is generated in the following specific way:

[0012] The corrosion start time is generated based on the corrosion start time; where the corrosion start time refers to the duration from the start time of the corrosion test to the corrosion start time.

[0013] A corrosion start rate score is generated based on the corrosion start time. The corrosion start rate score is the ratio between the corrosion start time and the standard corrosion start time. The standard corrosion start time is the time from the start of the corrosion test to the corrosion start time when the standard electrolytic copper foil is subjected to corrosion testing. The corrosion conditions of the standard electrolytic copper foil during corrosion testing are the same as those of the current electrolytic copper foil.

[0014] The passivation film formation time is determined based on the corrosion stagnation time; whereby the passivation film formation time refers to the duration from the corrosion start time to the corrosion stagnation time.

[0015] A passivation film forming speed score is generated based on the passivation film forming time; the passivation film forming speed score refers to the ratio between the passivation film forming time and the standard passivation film forming time.

[0016] A corrosion rate score is generated based on the initial corrosion rate score and the passivation film formation rate score; the corrosion rate score refers to the sum of the initial corrosion rate score and the passivation film formation rate score.

[0017] Based on the above technical solutions, the present invention also provides the following optional technical solutions:

[0018] Further technical solution: The method for obtaining the corrosion stagnation time is as follows:

[0019] The corrosion area and corrosion depth of each electrolytic copper foil obtained are screened; the specific screening method is to remove the corrosion area and corrosion depth of electrolytic copper foil before the corrosion start time.

[0020] The corrosion area and corrosion depth of the electrolytic copper foil obtained each time are arranged in time sequence to generate corrosion area dataset and corrosion depth dataset.

[0021] Corrosion area change curves and corrosion depth change curves were generated from the corrosion area dataset and corrosion depth dataset in chronological order, respectively.

[0022] Substitute the corrosion area change curve and the corrosion depth change curve into the same two-dimensional coordinate system to obtain the line segment in the corrosion area change curve and the corrosion depth change curve that is nearly parallel to the X-axis of the coordinate system. The starting point of this line segment is the corrosion stagnation time.

[0023] Further technical solution: The method for generating the corrosion degree score specifically includes:

[0024] The surface corrosion rate is generated based on the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation point; where the surface corrosion rate refers to the ratio between the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation stage and the surface area of ​​the electrolytic copper foil.

[0025] The depth corrosion rate is generated based on the stagnation corrosion depth of the electrolytic copper foil during the stagnation corrosion stage; whereby the depth corrosion rate refers to the ratio between the stagnation corrosion depth of the electrolytic copper foil during the stagnation corrosion stage and the thickness of the electrolytic copper foil.

[0026] A corrosion severity score is generated based on the surface corrosion rate and the depth corrosion rate.

[0027] A further technical solution: The corrosion degree score is generated based on the surface corrosion rate and depth corrosion rate, specifically as follows:

[0028] Through the formula:

[0029]

[0030] Generate corrosion degree score K s ;

[0031] In the formula, C a "This represents the surface corrosion rate threshold, C" d "This represents the threshold for deep corrosion rate, C" a This represents the surface corrosion rate, C. d This represents the depth corrosion rate. a1 and a2 are both weighting coefficients, and a1 + a2 = 1.

[0032] Further technical solutions: The methods for classifying the corrosion resistance of electrolytic copper foil include:

[0033] A corrosion resistance score is generated based on the corrosion rate score and the corrosion degree score; the corrosion resistance score refers to the difference between the corrosion rate score and the corrosion degree score.

[0034] The corrosion resistance of electrolytic copper foil is classified according to its corrosion resistance rating.

[0035] A corrosion resistance testing device for electrolytic copper foil used in lithium-ion batteries, the device specifically comprising:

[0036] Test components for corrosion testing of electrolytic copper foil;

[0037] The test data acquisition component is used to acquire test data of electrolytic copper foil in corrosion tests; the test data includes corrosion area, corrosion depth, corrosion start time and corrosion stagnation time;

[0038] The test data analysis unit is used to generate a corrosion rate score based on the test data of electrolytic copper foil in the corrosion test;

[0039] The state data acquisition unit is used to acquire corrosion state data of electrolytic copper foil during the corrosion stagnation stage; wherein, the corrosion state data includes stagnation corrosion area and stagnation corrosion depth;

[0040] The state analysis unit is used to generate a corrosion degree score based on the stagnant corrosion area and stagnant corrosion depth of the electrolytic copper foil at the corrosion stagnation time point;

[0041] The comprehensive analysis unit is used to classify the corrosion resistance of electrolytic copper foil based on corrosion rate and corrosion degree scores; the classification types include Class I corrosion resistance, Class II corrosion resistance, and Class III corrosion resistance.

[0042] The test data analysis unit specifically includes:

[0043] The corrosion start duration generation module is used to generate the corrosion start duration based on the corrosion start time; where the corrosion start duration refers to the time between the start time of the corrosion test and the corrosion start time.

[0044] The corrosion start time analysis module is used to generate a corrosion start rate score based on the corrosion start time. The corrosion start rate score is the ratio between the corrosion start time and the standard corrosion start time. The standard corrosion start time refers to the time from the start of the corrosion test to the corrosion start time when the standard electrolytic copper foil is subjected to corrosion testing. The corrosion conditions of the standard electrolytic copper foil during corrosion testing are the same as those of the current electrolytic copper foil.

[0045] The passivation film forming time generation module is used to generate the passivation film forming time based on the corrosion stagnation time; whereby the passivation film forming time refers to the time between the corrosion start time and the corrosion stagnation time.

[0046] The passivation film forming speed analysis module is used to generate a passivation film forming speed score based on the passivation film forming time; the passivation film forming speed score refers to the ratio between the passivation film forming time and the standard passivation film forming time.

[0047] The corrosion rate score generation module is used to generate a corrosion rate score based on the initial corrosion rate score and the passivation film formation rate score; wherein, the corrosion rate score refers to the sum of the initial corrosion rate score and the passivation film formation rate score.

[0048] Further technical solution: The state analysis unit specifically includes:

[0049] The surface corrosion rate analysis module is used to generate the surface corrosion rate based on the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation time point; where the surface corrosion rate refers to the ratio between the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation stage and the surface area of ​​the electrolytic copper foil.

[0050] The depth corrosion rate analysis module is used to generate the depth corrosion rate based on the stagnation corrosion depth of the electrolytic copper foil during the corrosion stagnation stage. The depth corrosion rate refers to the ratio between the stagnation corrosion depth of the electrolytic copper foil during the corrosion stagnation stage and the thickness of the electrolytic copper foil.

[0051] The corrosion severity rating generation module is used to generate a corrosion severity rating based on the surface corrosion rate and the depth corrosion rate.

[0052] Further technical solution: The comprehensive analysis unit specifically includes:

[0053] The comprehensive analysis module is used to generate a corrosion resistance score based on the corrosion rate score and the corrosion degree score; the corrosion resistance score refers to the difference between the corrosion rate score and the corrosion degree score.

[0054] The evaluation module is used to classify the corrosion resistance of electrolytic copper foil based on its corrosion resistance rating.

[0055] This invention provides a method and apparatus for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries, which has the following advantages compared with the prior art:

[0056] This invention obtains the corrosion area and depth of electrolytic copper foil during corrosion resistance testing, determines the corrosion start time and corrosion stagnation time, and combines this with the corrosion state of the electrolytic copper foil after the corrosion stagnation stage to comprehensively analyze the corrosion resistance of the electrolytic copper foil, thereby quantifying the corrosion resistance of the electrolytic copper foil and making the test results of corrosion resistance testing of electrolytic copper foil more comprehensive. Attached Figure Description

[0057] Figure 1 This is a flowchart illustrating a method for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries, provided in an embodiment of the present invention.

[0058] Figure 2 The flowchart is provided for step 2 in an embodiment of the present invention.

[0059] Figure 3 The flowchart for step 4 provided in the embodiment of the present invention is shown.

[0060] Figure 4 The flowchart for step 5 provided in this embodiment of the invention is shown.

[0061] Figure 5 This is a flowchart of a corrosion resistance testing device for electrolytic copper foil used in lithium-ion batteries, provided as an embodiment of the present invention.

[0062] Figure 6 This is a block diagram of the test data analysis unit provided in an embodiment of the present invention.

[0063] Figure 7 This is a block diagram of the state analysis unit provided in an embodiment of the present invention.

[0064] Figure 8 This is a block diagram of the comprehensive analysis unit provided in an embodiment of the present invention. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0066] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0067] Please see Figure 1 The present invention provides a method for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries, comprising the following steps:

[0068] Step 1: Conduct a corrosion test on the electrolytic copper foil and obtain test data of the electrolytic copper foil in the corrosion test; the test data includes corrosion area, corrosion depth, corrosion start time and corrosion stagnation time;

[0069] It should be further clarified that the corrosion start time refers to the time when corrosion occurs in the electrolytic copper foil; the corrosion stagnation time refers to the time when the corrosion rate of the electrolytic copper foil is slow or stagnant; in addition, slow rate refers to the rate at which corrosion approaches stagnation.

[0070] Specifically, corrosion tests on electrolytic copper foil include, but are not limited to, electrochemical corrosion tests, immersion corrosion tests, and salt spray corrosion tests. Furthermore, in these tests, both the area and depth of corrosion on the electrolytic copper foil are observed. For example, in the immersion corrosion test of electrolytic copper foil for lithium-ion electronics, the immersion solution used is a mixture of lithium salt solution (such as LiPF6, LiBF4, etc.) and an organic solvent. A common ratio might be 1M LiPF6 dissolved in a 1:1 mixture of dimethyl carbonate (DMC) and ethylene carbonate (EC).

[0071] In this embodiment, the corrosion area of ​​the electrolytic copper foil during the corrosion test can be obtained by image vision technology. For example, during the immersion corrosion process, the surface of the copper foil is imaged at high resolution using a scanning electron microscope (SEM) at regular intervals. SEM images with different magnifications are used to obtain the corrosion status of different areas. The surface morphology before and after corrosion is then compared to calculate the corrosion area.

[0072] The corrosion depth of electrolytic copper foil during corrosion testing can be obtained by X-ray micro-computed tomography (X-ray CT). For example, during immersion corrosion, three-dimensional images of the sample are scanned and acquired at regular intervals using an X-ray CT scanner to analyze the corrosion depth on the copper foil surface. This corrosion depth refers to the average depth of all corroded areas.

[0073] The corrosion start time can be determined by measuring the corrosion area of ​​the electrolytic copper foil each time. For example, if a corrosion area appears on the surface of the electrolytic copper foil during a surface image analysis, the time when the electrolytic copper foil is removed is the corrosion start time.

[0074] Step 2: Generate a corrosion rate score based on the test data of the electrolytic copper foil in the corrosion test;

[0075] Step 3: Obtain corrosion status data of electrolytic copper foil during the corrosion stagnation stage; the corrosion status data includes the stagnation corrosion area and the stagnation corrosion depth.

[0076] Step 4: Generate a corrosion degree score based on the stagnant corrosion area and stagnant corrosion depth of the electrolytic copper foil at the corrosion stagnation time point;

[0077] Step 5: Classify the corrosion resistance of electrolytic copper foil according to the corrosion rate score and corrosion degree score; the classification types include first-level corrosion resistance, second-level corrosion resistance and third-level corrosion resistance.

[0078] In a preferred embodiment of the present invention, the corrosion stagnation time is obtained specifically as follows:

[0079] The corrosion area and corrosion depth of the electrolytic copper foil obtained each time are screened. The specific screening method is to remove the corrosion area and corrosion depth of the electrolytic copper foil before the corrosion start time, that is, there is no data on the corrosion area and corrosion depth of the electrolytic copper foil.

[0080] The corrosion area and corrosion depth of the electrolytic copper foil obtained each time are arranged in time sequence to generate corrosion area dataset and corrosion depth dataset.

[0081] Corrosion area and corrosion depth datasets are used to generate corrosion area and corrosion depth variation curves in chronological order, respectively. For example, a two-dimensional coordinate system is established with time as the X-axis and the values ​​in the corrosion area dataset as the Y-axis. The data in the corrosion area dataset are substituted into the two-dimensional coordinate system to generate the corrosion area variation curve. Similarly, the corrosion depth variation curve is obtained in the same way as the corrosion area variation curve.

[0082] Substitute the corrosion area change curve and the corrosion depth change curve into the same two-dimensional coordinate system to obtain the line segment in the corrosion area change curve and the corrosion depth change curve that is nearly parallel to the X-axis of the coordinate system (the starting point of the line segment is the same X-axis coordinate value). The starting point of the line segment is the corrosion stagnation time.

[0083] It should be further explained that the Y-axis of the same two-dimensional coordinate system is dimensionless so that the corrosion area change curve and the corrosion depth change curve can exist in the same two-dimensional coordinate system; for example, the Y-axis coordinate value of the corrosion depth change curve is de-normalized and the value is reduced by a factor of m, so that the distance between the corrosion area change curve and the corrosion depth change curve is reduced, which facilitates subsequent identification.

[0084] Please see Figure 2 In a preferred embodiment of the present invention, the corrosion rate score is generated as follows:

[0085] S2.1: Generate the corrosion start duration based on the corrosion start time; where the corrosion start duration refers to the time between the start time of the corrosion test and the corrosion start time.

[0086] S2.2: Generate a corrosion initiation rate score based on the corrosion initiation time; where the corrosion initiation rate score refers to the ratio between the corrosion initiation time and the standard corrosion initiation time.

[0087] It should be noted that the standard corrosion start time refers to the time between the start of the corrosion test and the corrosion start time when the standard electrolytic copper foil is subjected to corrosion testing; in addition, the corrosion conditions (corrosive medium) of the standard electrolytic copper foil during corrosion testing are the same as those of the current electrolytic copper foil.

[0088] In this embodiment, compared with the corrosion initiation time of standard electrolytic copper foil, the longer the corrosion initiation time of electrolytic copper foil, the stronger the corrosion resistance of the copper foil surface may be. This is because corrosion requires a certain amount of time to occur, which may be due to the formation of a relatively stable protective film (such as an oxide film or passivation film) on the surface, which can effectively delay the start of the corrosion reaction. If the corrosion initiation time is shorter, it means that the copper foil surface lacks an effective protective film, or its structure is easily eroded by corrosive media, thus initiating the corrosion process more quickly. In this case, the corrosion resistance of the copper foil is poor.

[0089] S2.3: Based on the corrosion stagnation time, the passivation film formation time is determined; whereby the passivation film formation time refers to the duration from the corrosion start time to the corrosion stagnation time.

[0090] S2.4: Generate a passivation film forming speed score based on the passivation film forming time; whereby the passivation film forming speed score refers to the ratio between the passivation film forming time and the standard passivation film forming time;

[0091] In this embodiment, when the copper surface reacts with oxygen or other corrosive media during the corrosion process, a thin and dense layer of copper oxide (CuO) or other oxides is formed. This oxide film (i.e., passivation film) can effectively isolate the corrosive media (such as acid, oxygen, etc.) from direct contact with the copper metal, thereby slowing down or even stopping further corrosion. The formation of the passivation film makes the copper foil surface less active, greatly reducing the corrosion reaction rate, and even stopping it in some cases.

[0092] Furthermore, compared to the passivation film formation time of standard electrolytic copper foil, a longer passivation film formation time for electrolytic copper foil indicates a slower reaction rate between the copper foil surface and oxygen or other corrosive media during corrosion. This results in a longer passivation film formation time, or a longer corrosion stagnation time. If the corrosion process quickly enters a stagnation phase, it may indicate that the corrosion reaction is strongly influenced by the environment or media, or that the protective oxide layer on the copper foil surface is unstable and cannot effectively maintain its protective function. Therefore, the copper foil has poor corrosion resistance. For example, if the corrosion stagnation time of a certain electrolytic copper foil is 40 hours, it indicates that the surface of the copper foil can resist corrosion for a relatively long time and maintain corrosion resistance for a relatively long time after corrosion occurs. This may indicate that an effective protective film or passivation layer has formed on its surface. Conversely, if the corrosion stagnation time of another electrolytic copper foil is 10 hours, it indicates poor corrosion resistance, possibly due to the absence of an effective passivation film on the surface, or that the corrosion products have failed to form a sufficient protective layer to prevent further corrosion.

[0093] S2.5: Generate a corrosion rate score based on the initial corrosion rate score and the passivation film formation rate score; whereby the corrosion rate score is the sum of the initial corrosion rate score and the passivation film formation rate score.

[0094] For example, through the formula:

[0095] K t =C start ×α+C stagnate ×β;

[0096] Generate corrosion rate score K t ;

[0097] In the formula, C start This indicates the initial corrosion rate score, C. stagnate This represents the passivation film formation speed score, where α and β are both weighting coefficients, and α+β=1;

[0098] It should be noted that α and β are preset values, which are set by relevant personnel in the field, and the methods for obtaining these values ​​include, but are not limited to, expert consultation and experimental calibration.

[0099] In this embodiment, ideal corrosion resistance is typically characterized by a long time required for corrosion to begin and a long time for corrosion to stop. This indicates that the copper foil can not only resist the initiation of the corrosion reaction for a long time, but also maintain corrosion resistance for a long time after corrosion begins, and ultimately effectively slow down the continuation of corrosion through passivation or the formation of a protective layer.

[0100] Please see Figure 3 In a preferred embodiment of the present invention, the method for generating the corrosion degree score specifically includes:

[0101] S4.1: The surface corrosion rate is generated based on the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation point; where the surface corrosion rate refers to the ratio between the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation stage and the surface area of ​​the electrolytic copper foil.

[0102] It should be noted that the stagnant corrosion area of ​​the electrolytic copper foil during the stagnant corrosion stage refers to the total corrosion area on the surface of the electrolytic copper foil during the stagnant corrosion stage.

[0103] S4.2: Generate the depth corrosion rate based on the stagnation corrosion depth of the electrolytic copper foil during the stagnation corrosion stage; whereby the depth corrosion rate refers to the ratio between the stagnation corrosion depth of the electrolytic copper foil during the stagnation corrosion stage and the thickness of the electrolytic copper foil.

[0104] It should be noted that the stagnation corrosion depth of electrolytic copper foil in the stagnation corrosion stage refers to the average corrosion depth of the electrolytic copper foil in the stagnation corrosion stage.

[0105] S4.3: Generate a corrosion degree score based on surface corrosion rate and depth corrosion rate;

[0106] Specifically, through the formula:

[0107]

[0108] Generate corrosion degree score K s ;

[0109] In the formula, C a "This represents the surface corrosion rate threshold, C" d "This represents the threshold for deep corrosion rate, C" a This represents the surface corrosion rate, C. d This represents the depth corrosion rate, where a1 and a2 are both weighting coefficients, and a1 + a2 = 1;

[0110] It should be noted that the values ​​of a1 and a2 are set by those skilled in the art.

[0111] In this embodiment, the small surface corrosion area of ​​the electrolytic copper foil during the corrosion stagnation stage generally indicates that the electrolytic copper foil has strong corrosion resistance. A protective film (such as a copper oxide film) can be formed on the surface of the electrolytic copper foil, thereby slowing down the corrosion process and protecting the internal metal from further corrosion. This phenomenon shows that the electrolytic copper foil has good resistance to corrosive media, that is, the smaller the surface corrosion rate of the electrolytic copper foil, the stronger its resistance to corrosive media.

[0112] If the corrosion depth is shallow, it usually means that the electrolytic copper foil has good corrosion resistance. The corrosion rate slows down, and the corrosion does not go deeper during the stagnation stage, which shows the effectiveness of the material surface protection mechanism. This phenomenon indicates that the electrolytic copper foil may have formed a dense and stable protective film, which reduces further corrosion. That is, the smaller the depth corrosion rate of the electrolytic copper foil, the stronger its resistance to corrosive media.

[0113] When corrosion stops, electrolytic copper foil with better corrosion resistance can form a stable passivation layer earlier and inhibit the corrosion process, thus exhibiting a smaller corrosion area and shallower corrosion depth; conversely, electrolytic copper foil with poor corrosion resistance may continue to corrode until the material structure undergoes significant changes.

[0114] Furthermore, when electrolytic copper foil is used in lithium-ion batteries, its main function is to act as a current collector, responsible for effectively conducting electricity. If the surface corrosion area is too large, the conductivity of the copper foil will decrease, affecting the overall performance of the battery, especially during charging and discharging. Corrosion can lead to interruption of the current path and a decrease in battery efficiency. Therefore, in lithium-ion batteries, the smaller the corrosion area when corrosion stops, the better, because a smaller corrosion area helps maintain the conductivity, stability, and safety of the copper foil, thereby ensuring the long-term stable operation and high efficiency of the battery.

[0115] Meanwhile, if the corrosion depth of the copper foil is large, it will cause structural damage to the copper foil and reduce its conductivity, thereby affecting the charge and discharge performance of the battery. A shallower corrosion depth can maximize the conductivity of the copper foil and ensure the efficient operation of the battery. The greater the corrosion depth of the copper foil, the greater the risk of surface damage and corrosion product accumulation. These corrosion products may affect the battery's capacity retention and cycle performance, especially the stability of the electrode materials. Therefore, a smaller corrosion depth helps the battery maintain a higher capacity and a longer cycle life during repeated charge and discharge.

[0116] Please see Figure 4 In a preferred embodiment of the present invention, the method for classifying the corrosion resistance of electrolytic copper foil includes:

[0117] S5.1: Generate a corrosion resistance score based on the corrosion rate score and the corrosion degree score; whereby the corrosion resistance score refers to the difference between the corrosion rate score and the corrosion degree score.

[0118] S5.2: Classify the corrosion resistance of electrolytic copper foil according to the corrosion resistance rating;

[0119] Specifically, the corrosion resistance score is compared with a preset score range; the preset score range includes a first threshold and a second threshold, and the first threshold is less than the second threshold.

[0120] If the corrosion resistance score is less than or equal to the first threshold, it means that the smaller the corrosion resistance score, the more abnormal the corrosion test result of the electrolytic copper foil, that is, the weaker the corrosion resistance of the electrolytic copper foil. Therefore, the corrosion resistance of the electrolytic copper foil is judged to be level three.

[0121] If the corrosion resistance score is greater than the first threshold and less than the second threshold, it means that the higher the corrosion resistance score, the more normal the corrosion test result of the electrolytic copper foil is, that is, the more normal the corrosion resistance of the electrolytic copper foil is, and the corrosion resistance of the electrolytic copper foil is judged to be level two corrosion resistance.

[0122] If the corrosion resistance score is greater than the second threshold, it means that the higher the corrosion resistance score, the better the corrosion test result of the electrolytic copper foil, that is, the stronger the corrosion resistance of the electrolytic copper foil. In this case, the corrosion resistance of the electrolytic copper foil is judged to be Level 1 corrosion resistance.

[0123] This invention also provides a corrosion resistance testing device for electrolytic copper foil used in lithium-ion batteries. This device is used to perform the aforementioned corrosion resistance testing method for electrolytic copper foil used in lithium-ion batteries, specifically including:

[0124] Test components for corrosion testing of electrolytic copper foil;

[0125] It should be further explained that the test assembly is a corrosion resistance test assembly in the prior art, which can provide the necessary support for corrosion testing of electrolytic copper foil; for example, when using immersion corrosion testing, the test assembly includes an immersion container, an immersion solution storage tank, a temperature control device, and a stirring device, etc.

[0126] Please see Figure 5 The device also includes:

[0127] The test data acquisition component 10 is used to acquire test data of electrolytic copper foil in corrosion testing; the test data includes corrosion area, corrosion depth, corrosion start time and corrosion stagnation time;

[0128] The test data analysis unit 20 is used to generate a corrosion rate score based on the test data of the electrolytic copper foil in the corrosion test;

[0129] The state data acquisition unit 30 is used to acquire corrosion state data of electrolytic copper foil during the corrosion stagnation stage; wherein, the corrosion state data includes stagnation corrosion area and stagnation corrosion depth;

[0130] The state analysis unit 40 is used to generate a corrosion degree score based on the stagnant corrosion area and stagnant corrosion depth of the electrolytic copper foil at the corrosion stagnation time point;

[0131] The comprehensive analysis unit 50 is used to classify the corrosion resistance of electrolytic copper foil based on corrosion rate score and corrosion degree score; the classification types include first-level corrosion resistance, second-level corrosion resistance and third-level corrosion resistance.

[0132] Please see Figure 6 The test data analysis unit specifically includes:

[0133] The corrosion start duration generation module 21 is used to generate the corrosion start duration based on the corrosion start time; wherein, the corrosion start duration refers to the duration from the start time of the corrosion test to the corrosion start time.

[0134] The corrosion start time analysis module 22 is used to generate a corrosion start rate score based on the corrosion start time; the corrosion start rate score refers to the ratio between the corrosion start time and the standard corrosion start time.

[0135] The passivation film forming time generation module 23 is used to generate the passivation film forming time based on the corrosion stagnation time; wherein, the passivation film forming time refers to the time between the corrosion start time and the corrosion stagnation time.

[0136] The passivation film forming speed analysis module 24 is used to generate a passivation film forming speed score based on the passivation film forming time; wherein, the passivation film forming speed score refers to the ratio between the passivation film forming time and the standard passivation film forming time;

[0137] The corrosion rate score generation module 25 is used to generate a corrosion rate score based on the initial corrosion rate score and the passivation film formation rate score; wherein, the corrosion rate score refers to the sum between the initial corrosion rate score and the passivation film formation rate score.

[0138] Please see Figure 7 The state analysis unit specifically includes:

[0139] The surface corrosion rate analysis module 41 is used to generate the surface corrosion rate based on the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation time point; wherein, the surface corrosion rate refers to the ratio between the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation stage and the surface area of ​​the electrolytic copper foil.

[0140] The depth corrosion rate analysis module 42 is used to generate the depth corrosion rate based on the stagnation corrosion depth of the electrolytic copper foil during the corrosion stagnation stage; wherein, the depth corrosion rate refers to the ratio between the stagnation corrosion depth of the electrolytic copper foil during the corrosion stagnation stage and the thickness of the electrolytic copper foil.

[0141] The corrosion degree rating generation module 43 is used to generate a corrosion degree rating based on the surface corrosion rate and the depth corrosion rate.

[0142] Please see Figure 8 The comprehensive analysis unit specifically includes:

[0143] The comprehensive analysis module 51 is used to generate a corrosion resistance score based on the corrosion rate score and the corrosion degree score; whereby the corrosion resistance score refers to the difference between the corrosion rate score and the corrosion degree score.

[0144] Evaluation module 52 is used to classify the corrosion resistance of electrolytic copper foil based on corrosion resistance rating.

[0145] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries, characterized in that, Includes the following steps: The electrolytic copper foil was subjected to corrosion tests to obtain test data, including corrosion area, corrosion depth, corrosion start time, and corrosion stagnation time. A corrosion rate score is generated based on the test data of electrolytic copper foil in the corrosion test; Obtain corrosion state data of electrolytic copper foil during the corrosion stagnation stage; the corrosion state data includes the stagnation corrosion area and stagnation corrosion depth. A corrosion severity score is generated based on the stagnant corrosion area and stagnant corrosion depth of the electrolytic copper foil at the corrosion stagnation time point. The corrosion resistance of electrolytic copper foil is classified according to corrosion rate score and corrosion degree score; The corrosion rate score is generated in the following specific way: The corrosion start time is generated based on the corrosion start time; where the corrosion start time refers to the duration from the start time of the corrosion test to the corrosion start time. A corrosion start rate score is generated based on the corrosion start time. The corrosion start rate score is the ratio between the corrosion start time and the standard corrosion start time. The standard corrosion start time is the time from the start of the corrosion test to the corrosion start time when the standard electrolytic copper foil is subjected to corrosion testing. The corrosion conditions of the standard electrolytic copper foil during corrosion testing are the same as those of the current electrolytic copper foil. The passivation film formation time is determined based on the corrosion stagnation time; whereby the passivation film formation time refers to the duration from the corrosion start time to the corrosion stagnation time. A passivation film forming speed score is generated based on the passivation film forming time; the passivation film forming speed score refers to the ratio between the passivation film forming time and the standard passivation film forming time. A corrosion rate score is generated based on the initial corrosion rate score and the passivation film formation rate score; the corrosion rate score refers to the sum of the initial corrosion rate score and the passivation film formation rate score.

2. The method for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries according to claim 1, characterized in that, The specific method for obtaining the corrosion stagnation time is as follows: The corrosion area and corrosion depth of each electrolytic copper foil obtained are screened; the specific screening method is to remove the corrosion area and corrosion depth of electrolytic copper foil before the corrosion start time. The corrosion area and corrosion depth of the electrolytic copper foil obtained each time are arranged in time sequence to generate corrosion area dataset and corrosion depth dataset. Corrosion area change curves and corrosion depth change curves were generated from the corrosion area dataset and corrosion depth dataset in chronological order, respectively. Substitute the corrosion area change curve and the corrosion depth change curve into the same two-dimensional coordinate system to obtain the line segment in the corrosion area change curve and the corrosion depth change curve that is nearly parallel to the X-axis of the coordinate system. The starting point of this line segment is the corrosion stagnation time.

3. The method for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries according to claim 1, characterized in that, The specific methods for generating the corrosion degree score include: The surface corrosion rate is generated based on the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation point; where the surface corrosion rate refers to the ratio between the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation stage and the surface area of ​​the electrolytic copper foil. The depth corrosion rate is generated based on the stagnation corrosion depth of the electrolytic copper foil during the stagnation corrosion stage; whereby the depth corrosion rate refers to the ratio between the stagnation corrosion depth of the electrolytic copper foil during the stagnation corrosion stage and the thickness of the electrolytic copper foil. A corrosion severity score is generated based on the surface corrosion rate and the depth corrosion rate.

4. The method for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries according to claim 3, characterized in that, The corrosion degree score is generated based on the surface corrosion rate and the depth corrosion rate, specifically as follows: Through the formula: Generate corrosion degree score K s ; In the formula, C a " This represents the surface corrosion rate threshold, C. d " This represents the depth corrosion rate threshold, C. a This represents the surface corrosion rate, C. d This represents the depth corrosion rate. a1 and a2 are both weighting coefficients, and a1 + a2 = 1.

5. The method for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries according to claim 1, characterized in that, The methods for classifying the corrosion resistance of electrolytic copper foil include: A corrosion resistance score is generated based on the corrosion rate score and the corrosion degree score; the corrosion resistance score refers to the difference between the corrosion rate score and the corrosion degree score. The corrosion resistance of electrolytic copper foil is classified according to its corrosion resistance rating.

6. A device for testing the corrosion resistance of electrolytic copper foil for lithium-ion batteries, characterized in that, The device is used to perform a corrosion resistance test method for electrolytic copper foil for lithium-ion batteries as described in any one of claims 1-5, specifically including: Test components for corrosion testing of electrolytic copper foil; The test data acquisition component is used to acquire test data of electrolytic copper foil in corrosion tests; the test data includes corrosion area, corrosion depth, corrosion start time and corrosion stagnation time; The test data analysis unit is used to generate a corrosion rate score based on the test data of electrolytic copper foil in corrosion tests; The state data acquisition unit is used to acquire corrosion state data of electrolytic copper foil during the corrosion stagnation stage; wherein, the corrosion state data includes stagnant corrosion area and stagnant corrosion depth; The state analysis unit is used to generate a corrosion degree score based on the stagnant corrosion area and stagnant corrosion depth of the electrolytic copper foil at the corrosion stagnation time point; The comprehensive analysis unit is used to classify the corrosion resistance of electrolytic copper foil based on corrosion rate and corrosion degree scores; the classification types include Class I corrosion resistance, Class II corrosion resistance, and Class III corrosion resistance. The test data analysis unit specifically includes: The corrosion start duration generation module is used to generate the corrosion start duration based on the corrosion start time; where the corrosion start duration refers to the time between the start time of the corrosion test and the corrosion start time. The corrosion start time analysis module is used to generate a corrosion start rate score based on the corrosion start time. The corrosion start rate score is the ratio between the corrosion start time and the standard corrosion start time. The standard corrosion start time refers to the time from the start of the corrosion test to the corrosion start time when the standard electrolytic copper foil is subjected to corrosion testing. The corrosion conditions of the standard electrolytic copper foil during corrosion testing are the same as those of the current electrolytic copper foil. The passivation film forming time generation module is used to generate the passivation film forming time based on the corrosion stagnation time; whereby the passivation film forming time refers to the time between the corrosion start time and the corrosion stagnation time. The passivation film forming speed analysis module is used to generate a passivation film forming speed score based on the passivation film forming time; the passivation film forming speed score refers to the ratio between the passivation film forming time and the standard passivation film forming time. The corrosion rate score generation module is used to generate a corrosion rate score based on the initial corrosion rate score and the passivation film formation rate score; wherein, the corrosion rate score refers to the sum of the initial corrosion rate score and the passivation film formation rate score.

7. The corrosion resistance testing device for electrolytic copper foil for lithium-ion batteries according to claim 6, characterized in that, The state analysis unit specifically includes: The surface corrosion rate analysis module is used to generate the surface corrosion rate based on the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation time point; where the surface corrosion rate refers to the ratio between the stagnant corrosion area of ​​the electrolytic copper foil at the corrosion stagnation stage and the surface area of ​​the electrolytic copper foil. The depth corrosion rate analysis module is used to generate the depth corrosion rate based on the stagnation corrosion depth of the electrolytic copper foil during the corrosion stagnation stage. The depth corrosion rate refers to the ratio between the stagnation corrosion depth of the electrolytic copper foil during the corrosion stagnation stage and the thickness of the electrolytic copper foil. The corrosion severity rating generation module is used to generate a corrosion severity rating based on the surface corrosion rate and the depth corrosion rate.

8. The corrosion resistance testing device for electrolytic copper foil for lithium-ion batteries according to claim 6, characterized in that, The comprehensive analysis unit specifically includes: The comprehensive analysis module is used to generate a corrosion resistance score based on the corrosion rate score and the corrosion degree score; the corrosion resistance score refers to the difference between the corrosion rate score and the corrosion degree score. The evaluation module is used to classify the corrosion resistance of electrolytic copper foil based on its corrosion resistance rating.

Images