A method and device for detecting lithium precipitation from a battery

Abstract

The application discloses a battery lithium precipitation detection method and device. When an electrochemical impedance test is performed on a battery, a corresponding first test result can be obtained. According to the first test result, corresponding first positive electrode charge transfer impedance and first negative electrode charge transfer impedance can be determined. Then, at least according to the initial positive electrode charge transfer impedance, the initial negative electrode charge transfer impedance, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance, whether the battery has lithium precipitation can be determined. In this way, when detecting whether the battery has lithium precipitation, the battery does not need to be disassembled, and the detection can be realized, so that nondestructive testing is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, and particularly relates to a battery lithium precipitation detection method and device. BACKGROUND

[0002] Lithium ion batteries are prone to lithium precipitation under high state of charge, low temperature and large charge rate. Lithium precipitation can cause the capacity of the battery cell to decrease, the impedance to increase, and the safety of the lithium ion battery to decrease. Therefore, lithium precipitation detection of the lithium ion battery is particularly important. SUMMARY

[0003] Embodiments of the present application provide a battery lithium precipitation detection method and device, which are used for lossless detection of whether the battery has lithium precipitation.

[0004] In a first aspect, embodiments of the present application provide a battery lithium precipitation detection method, which comprises the following steps.

[0005] According to a first test result obtained by performing electrochemical impedance testing on the battery, determining a first positive electrode charge transfer impedance and a first negative electrode charge transfer impedance of the battery.

[0006] At least according to the initial positive electrode charge transfer impedance, the initial negative electrode charge transfer impedance, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance, determining whether the battery has lithium precipitation.

[0007] The initial positive electrode charge transfer impedance and the initial negative electrode charge transfer impedance are determined according to an initial test result obtained by performing the electrochemical impedance testing on a fresh battery corresponding to the battery.

[0008] In a second aspect, embodiments of the present application provide a battery lithium precipitation detection device, which comprises the following steps.

[0009] A memory is configured to store program instructions.

[0010] A processor is configured to call the program instructions stored in the memory, and execute the above-mentioned battery lithium precipitation detection method according to the obtained program.

[0011] The present application has the following advantages.

[0012] The battery lithium precipitation detection method and device provided by the embodiment of the present application can obtain a corresponding first test result when performing electrochemical impedance testing on the battery, and can determine corresponding first positive electrode charge transfer impedance and first negative electrode charge transfer impedance according to the first test result, and then can determine whether the battery has lithium precipitation at least according to the initial positive electrode charge transfer impedance, the initial negative electrode charge transfer impedance, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance. In this way, when detecting whether the battery has lithium precipitation, the battery does not need to be disassembled to realize detection, so that nondestructive testing is realized. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A flowchart of a battery lithium precipitation detection method provided in the embodiment of the present application is shown.

[0014] Figure 2 A schematic diagram of battery lithium precipitation provided in the embodiment of the present application is shown.

[0015] Figure 3 A flowchart of a specific embodiment provided in the embodiment of the present application is shown.

[0016] Figure 4 A spectrum diagram after DRT analysis provided in the embodiment of the present application is shown.

[0017] Figure 5 Another spectrum diagram after DRT analysis provided in the embodiment of the present application is shown.

[0018] Figure 6 A structural schematic diagram of a battery lithium precipitation detection device provided in the embodiment of the present application is shown. DETAILED DESCRIPTION

[0019] The specific embodiments of the battery lithium precipitation detection method and device provided by the embodiment of the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0020] The embodiment of the present application provides a battery lithium precipitation detection method, as shown in Figure 1 may include:

[0021] S101, determining the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance of the battery according to the first test result obtained by performing electrochemical impedance testing on the battery;

[0022] In some embodiments, the battery mentioned in S101 can be a battery that has been cycled for N times, where N can be a positive integer greater than a preset number, which is not limited herein.

[0023] In some embodiments, when performing the electrochemical impedance test, the test conditions include:

[0024] The test temperature is 25°C;

[0025] The test frequency range is 0.01 Hz to 10 6 Hz;

[0026] The perturbation voltage is 5 mV.

[0027] Of course, the test conditions are not limited to this, which is only an example here. The test conditions can be designed according to actual needs, which are not limited herein.

[0028] S102, at least according to the initial positive electrode charge transfer impedance, the initial negative electrode charge transfer impedance, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance, determine whether the battery has lithium precipitation; wherein the initial positive electrode charge transfer impedance and the initial negative electrode charge transfer impedance are: when performing electrochemical impedance test on the fresh battery corresponding to the battery, the initial test result is determined according to the initial test result.

[0029] When performing electrochemical impedance test on the battery, the corresponding first test result can be obtained, and the corresponding first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance can be determined according to the first test result, and then the battery can be determined whether lithium precipitation occurs at least according to the initial positive electrode charge transfer impedance, the initial negative electrode charge transfer impedance, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance; in this way, when detecting whether the battery has lithium precipitation, the battery can be detected without disassembly, so as to realize nondestructive testing.

[0030] Moreover, only electrochemical impedance test needs to be performed on the battery, so as to realize nondestructive testing, which is simple and easy to operate, has little influence on the performance of the battery, and does not need destructive disassembly confirmation, so that the battery which has not occurred lithium precipitation can continue to be used, and the detection cost can be reduced and the detection efficiency can be improved.

[0031] In addition, the detection method is not limited by the type of battery, that is, the detection method can be applied to various types and models of batteries, such as but not limited to: soft package battery, metal shell battery or cylindrical battery, etc., which has a wide range of applications.

[0032] In some embodiments, according to the first test result, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance of the battery are determined, which specifically includes:

[0033] The first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance are obtained by using a relaxation time distribution (DRT) analysis algorithm to analyze the first test result.

[0034] In this way, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance can be accurately obtained by analyzing the test result of the electrochemical impedance test based on the DRT technology, so that the accuracy of the determination result can be improved.

[0035] Specifically, the process of determining the initial positive electrode charge transfer impedance and the initial negative electrode charge transfer impedance of the fresh battery according to the initial test result can refer to the specific embodiments of determining the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance according to the first test result, which will not be described in detail here.

[0036] In the embodiments of the present application, when determining whether lithium precipitation occurs in the battery, the following two methods can be included:

[0037] Method 1:

[0038] In some embodiments, whether lithium precipitation occurs in the battery is determined according to at least the initial positive electrode charge transfer impedance, the initial negative electrode charge transfer impedance, the first positive electrode charge transfer impedance, and the first negative electrode charge transfer impedance, specifically including:

[0039] calculating a first positive electrode ratio of the first positive electrode charge transfer impedance to the initial positive electrode charge transfer impedance, and a first negative electrode ratio of the first negative electrode charge transfer impedance to the initial negative electrode charge transfer impedance;

[0040] determining whether lithium precipitation occurs in the battery according to the first positive electrode ratio and the first negative electrode ratio.

[0041] The fresh battery can be understood as a battery with a cycle number less than a preset number, and the preset number can be but is not limited to 10.

[0042] In this way, whether lithium precipitation occurs in the battery can be determined according to the first positive electrode ratio and the first negative electrode ratio, which simplifies the detection process and improves the detection efficiency.

[0043] In some embodiments, whether lithium precipitation occurs in the battery is determined according to the first positive electrode ratio and the first negative electrode ratio, specifically including:

[0044] when the first positive electrode ratio is less than a first preset value, determining whether the first negative electrode ratio is greater than or equal to the first preset value;

[0045] if yes, it is determined that lithium precipitation occurs in the battery;

[0046] if no, it is determined that lithium precipitation does not occur in the battery.

[0047] The first preset value can be different or the same for different types of batteries, and needs to be determined according to the specific battery type, which is not limited herein.

[0048] That is, the first positive electrode ratio can be determined first, and if the first positive electrode ratio is less than the first preset value, it can be considered that the first positive electrode charge transfer impedance does not increase significantly compared with the initial positive electrode charge transfer impedance, and then it is further determined whether the first negative electrode ratio is greater than or equal to the first preset value to determine whether the first negative electrode charge transfer impedance increases significantly compared with the initial negative electrode charge transfer impedance. If yes, it means that the increase is significant, and then it can be determined that the battery has lithium precipitation. If no, it means that the increase is not significant, and then it can be determined that the battery does not have lithium precipitation.

[0049] It is noted that in the embodiment of the present application, the first positive electrode ratio is determined first, and the first negative electrode ratio is determined when the first positive electrode ratio meets the condition. If the first positive electrode ratio does not meet the condition, the first negative electrode ratio will not be determined, that is, the battery will not be determined whether it has lithium precipitation according to the above process.

[0050] In this way, whether the battery has lithium precipitation can be determined based on the first positive electrode ratio and the first negative electrode ratio, so that the lithium precipitation of the battery can be quickly and accurately detected, the detection efficiency is improved, and the detection accuracy is also improved.

[0051] The judgment mechanism of whether the battery has lithium precipitation is explained and described below.

[0052] Firstly, the B-V equation is:

[0053] Rct=K / (j.A);

[0054] wherein Rct represents the charge transfer impedance, K is a constant, j is the current density, A is the electrode area, and (j.A) represents the functional relationship between j and A.

[0055] Secondly, according to the above B-V equation, it can be known that:

[0056] For the positive electrode:

[0057] When the battery has lithium precipitation, the lithium precipitation reaction generally occurs on the surface of the negative electrode, so the electrode area of the positive electrode does not change significantly, and the current density near the positive electrode also does not change significantly, and thus the positive electrode charge transfer impedance does not change significantly. However, considering the influence of error, the first positive electrode ratio can be set to be less than the first preset value to eliminate the influence of error.

[0058] For the negative electrode:

[0059] In the initial stage of lithium plating of the battery, the electrode area of the negative electrode changes greatly, while the current density near the negative electrode does not change significantly at this time, so the decrease of the electrode area becomes the dominant factor, resulting in a significant increase in the charge transfer impedance of the negative electrode;

[0060] When the current I = (j.A), the current can be a fixed value, and as lithium plating occurs, the electrode area of the negative electrode gradually decreases, resulting in a gradual increase in the local current density, eventually making the charge transfer impedance of the negative electrode tend to be stable and no longer change significantly.

[0061] Therefore, when the first positive electrode ratio is less than the first preset value, it can be considered that the first positive electrode charge transfer impedance does not change significantly compared with the initial positive electrode charge transfer impedance; when the first negative electrode ratio is greater than or equal to the first preset value, it can be considered that the first negative electrode charge transfer impedance increases significantly compared with the initial negative electrode charge transfer impedance, at this time it can be considered that the battery has lithium plating.

[0062] Method 2:

[0063] In some embodiments, the determination of whether the battery has lithium plating is based on at least the initial positive electrode charge transfer impedance, the initial negative electrode charge transfer impedance, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance, specifically comprising:

[0064] calculating a first positive electrode ratio of the first positive electrode charge transfer impedance to the initial positive electrode charge transfer impedance;

[0065] when the first positive electrode ratio is less than the first preset value, heating the battery according to the preset heating condition and cooling to room temperature, and obtaining a second test result by electrochemical impedance testing on the heated battery;

[0066] determining whether the battery has lithium plating according to the first positive electrode charge transfer impedance, the first negative electrode charge transfer impedance, the second positive electrode charge transfer impedance and the second negative electrode charge transfer impedance.

[0067] In this way, the first positive electrode ratio can be determined first, and when the first positive electrode ratio is less than the first preset value, it indicates that the first positive electrode charge transfer impedance does not increase significantly compared with the initial positive electrode charge transfer impedance, at this time the battery is heated, and based on the first positive electrode charge transfer impedance, the first negative electrode charge transfer impedance, the second positive electrode charge transfer impedance and the second negative electrode charge transfer impedance, a further judgment is made to finally determine whether the battery has lithium plating, thereby improving the accuracy of the final detection result and reducing errors.

[0068] Specifically, the process of determining the second positive charge transfer impedance and the second negative charge transfer impedance according to the second test result can refer to the above-mentioned specific embodiments of determining the first positive charge transfer impedance and the first negative charge transfer impedance according to the first test result, and will not be described in detail here.

[0069] In some embodiments, the determination of whether lithium precipitation occurs in the battery according to the first positive charge transfer impedance, the first negative charge transfer impedance, the second positive charge transfer impedance, and the second negative charge transfer impedance specifically comprises:

[0070] calculating a second positive electrode ratio of the second positive charge transfer impedance to the first positive charge transfer impedance, and a second negative electrode ratio of the second negative charge transfer impedance to the first negative charge transfer impedance;

[0071] determining whether the second positive electrode ratio is greater than a second preset value and whether the second negative electrode ratio is greater than a third preset value;

[0072] if yes, it is determined that lithium precipitation occurs in the battery;

[0073] if no, it is determined that lithium precipitation does not occur in the battery.

[0074] The second preset value and the third preset value can be set according to actual needs, and the second preset value and the third preset value corresponding to different types of batteries can be different, which is not limited here.

[0075] After heating the battery, the heating temperature used can accelerate the change of the surface structure of the positive electrode material, and thus cause adverse effects on the embedding and de-embedding of Li + into and out of the positive electrode, so that the charge transfer impedance of the heated positive electrode increases compared with that before heating.

[0076] Moreover, when lithium precipitation occurs, lithium metal is precipitated on the surface of the negative electrode, and the lithium metal can accelerate the reaction with the electrolyte at a higher temperature to generate lithium salt. The generated lithium salt adheres to the surface of the active material of the negative electrode, affecting the embedding and de-embedding of Li + into and out of the negative electrode, so that the charge transfer impedance of the heated negative electrode increases compared with that before heating.

[0077] In this way, if it is determined that the charge transfer impedance of the heated negative electrode and the charge transfer impedance of the heated positive electrode increase, it indicates that lithium precipitation has occurred in the battery before heating, so that the conclusion that the battery has occurred lithium precipitation can be accurately drawn.

[0078] It should be noted that this way 2 can be understood as:

[0079] first, the first positive electrode ratio and the first negative electrode ratio are used to preliminarily determine whether lithium precipitation occurs in the battery (the result is recorded as result 1);

[0080] Afterwards, based on the second positive electrode ratio and the second negative electrode ratio, it is determined again whether lithium precipitation occurs in the battery (the result is recorded as result 2) ;

[0081] If the result 1 is the same as the result 2, it means that the preliminary determination result is accurate. If the result 1 is different from the result 2, it means that the preliminary determination result has an error. At this time, the result 2 can be used as the final determination result of whether lithium precipitation occurs in the battery.

[0082] That is, the result 2 can be used to verify the result 1, verify whether the result 1 is accurate and reliable, thereby improving the accuracy of the final determination result, reducing the influence of errors, and reducing misjudgment.

[0083] In some embodiments, the preset heating condition includes: maintaining at 60-100°C for a preset time.

[0084] The preset time can be, but is not limited to, 3h, and can also be set to 0.5h-24h. The specific value can be set according to actual needs, detection efficiency, and other factors, which are not limited herein.

[0085] For example, taking a soft package battery and the second preset value of 106% and the third preset value of 150% as an example, through experiments, it can be obtained that the second positive electrode ratio of the soft package battery at 35°C and 1.2C after heating treatment is 173%, and the second negative electrode ratio is 1582%. Obviously, 173% is greater than 106%, and 1582% is greater than 150%, so it can be determined that the battery has lithium precipitation. Moreover, by disassembling the battery, it is found that the battery has indeed lithium precipitation, as shown in FIG. 1, wherein the dashed circle in the figure indicates the position of lithium precipitation. Figure 2

[0086] In some embodiments, the method further comprises:

[0087] According to the first negative electrode charge transfer impedance and the second negative electrode charge transfer impedance, the degree of lithium precipitation of the battery is determined.

[0088] In this way, when it is determined that lithium precipitation occurs in the battery, the degree of lithium precipitation can be further determined, thereby providing a reference for the maintenance and later design and improvement of the battery.

[0089] In some embodiments, according to the first negative electrode charge transfer impedance and the second negative electrode charge transfer impedance, the degree of lithium precipitation of the battery is determined, specifically comprising:

[0090] A second negative electrode ratio of the second negative electrode charge transfer impedance to the first negative electrode charge transfer impedance is calculated;

[0091] According to the corresponding relationship between the ratio and the degree of lithium precipitation, the degree of lithium precipitation corresponding to the second negative electrode ratio is found; ​

[0092] The found lithium precipitation degree is determined as the lithium precipitation degree of the battery.

[0093] The corresponding relationship can be, but is not limited to, as shown in Table 1.

[0094] Table 1

[0095] Ratio Degree of lithium precipitation [B1-B2) No lithium precipitation [B2-B3) Beginning of lithium precipitation [B3-B4) Moderate lithium precipitation [B4-B5) Severe lithium precipitation

[0096] Suppose that a battery (denoted as battery 1) that has been cycled 50 times is heated and cooled, and denoted as battery 2, then:

[0097] If the ratio of the first negative electrode charge transfer impedance corresponding to battery 1 to the second negative electrode charge transfer impedance corresponding to battery 2 is greater than B3 and less than B4, it can be determined that the lithium precipitation degree of the battery is moderate lithium precipitation, indicating that the battery has been lithium precipitated for a period of time, and a large amount of elemental lithium has been precipitated. If battery 1 continues to be used, the risk of danger is high, so at this time it is recommended not to continue to use battery 1.

[0098] If the ratio of the first negative electrode charge transfer impedance corresponding to battery 1 to the second negative electrode charge transfer impedance corresponding to battery 2 is greater than B2 and less than B3, it can be determined that the lithium precipitation degree of the battery is beginning to precipitate lithium, indicating that the battery has just begun to precipitate lithium. If battery 1 continues to be used, the risk of danger is low, so at this time it is recommended to continue to use battery 1.

[0099] If the ratio of the first negative electrode charge transfer impedance corresponding to battery 1 to the second negative electrode charge transfer impedance corresponding to battery 2 is greater than B4 and less than B5, it can be determined that the lithium precipitation degree of the battery is severe lithium precipitation, indicating that the battery has already occurred severe lithium precipitation. If battery 1 continues to be used, danger may occur at any time, so at this time it is recommended not to continue to use battery 1.

[0100] Specifically, the values of B1, B2, B3, B4 and B5 can be set according to the type of the battery, which is not limited herein.

[0101] In this way, based on the second negative electrode charge transfer impedance and the first negative electrode charge transfer impedance, and the corresponding relationship, the lithium precipitation degree of the battery can be determined, thereby providing guidance for subsequent use of the battery, improving the safety of the battery use, and maximizing the performance of the battery.

[0102] The battery lithium precipitation detection method will be described below in conjunction with specific embodiments.

[0103] In conjunction with Figure 3As shown, the above mode 2 is taken as an example for illustration. Among them, the initial positive electrode charge transfer impedance is represented by Rct-p0, the initial negative electrode charge transfer impedance is represented by Rct-n0, the first positive electrode charge transfer impedance is represented by Rct-p1, the first negative electrode charge transfer impedance is represented by Rct-n1, the second positive electrode charge transfer impedance is represented by Rct-p2, and the second negative electrode charge transfer impedance is represented by Rct-n2; and when the fresh battery is cycled for N times, the battery cycled for N times is recorded as battery 1, and whether lithium precipitation occurs in battery 1 is judged, wherein N is any positive integer.

[0104] S301, electrochemical impedance test is performed on battery 1, and after obtaining the test result, DRT analysis is performed to obtain Rct-p1 and Rct-n1;

[0105] S302, determine the Rct-p0 and Rct-n0 of the fresh battery corresponding to the battery 1;

[0106] Among them, the Rct-p0 and Rct-n0 of the fresh battery can be determined in advance before performing S301, and the determination method comprises:

[0107] The electrochemical impedance test is performed on the fresh battery, and after obtaining the test result, DRT analysis is performed to obtain Rct-p0 and Rct-n0.

[0108] S303, judge whether Rct-p1 / Rct-p0 is less than the first preset value; if yes, execute S304; if no, end the process;

[0109] S304, judge whether Rct-n1 / Rct-n0 is greater than or equal to the first preset value; if yes, execute S305; if no, execute S306;

[0110] S305, initially judge that battery 1 has lithium precipitation; execute S307;

[0111] S306, initially judge that battery 1 has not lithium precipitation;

[0112] S307, heat battery 1 according to the preset heating condition and then cool it to obtain battery 2, perform electrochemical impedance test on battery 2, and after obtaining the test result, perform DRT analysis to obtain Rct-p2 and Rct-n2;

[0113] S308, judge whether Rct-p2 / Rct-p1 is greater than the second preset value and Rct-n2 / Rct-n1 is greater than the third preset value; if yes, execute S309; if no, execute S310;

[0114] S309, finally determine that battery 1 has lithium precipitation;

[0115] S310, It was finally determined that lithium plating did not occur in battery 1.

[0116] The following example illustrates this.

[0117] Take metal-cased batteries as an example.

[0118] After performing electrochemical impedance spectroscopy (EIS) tests on batteries in four different states, the test results were analyzed using DRT (Dielectric Resistance Thermometry) technology to obtain... Figure 4 The spectrum shown, Figure 4 The diagram shows four types of impedance, where P1 represents solid-phase diffusion impedance, P2 represents liquid-phase diffusion impedance, P3 represents positive electrode charge transfer impedance (denoted by Rct-p), and P4 represents negative electrode charge transfer impedance (denoted by Rct-n). The horizontal axis represents the logarithm of the frequency, and the vertical axis represents the impedance value.

[0119] Through the Figure 4 The data in the table was organized to obtain the corresponding Table 2. Figure 4 In Table 2, "97% SOH battery" refers to a battery with a state of health of 97% after a period of cycling, and "75% SOH battery" refers to a battery with a state of health of 75% after a period of cycling. The cycling time of the 75% SOH battery is longer than that of the 97% SOH battery. "Sto-97% SOH battery" refers to a battery with a state of health of 97% after being stored fresh without cycling. Since this type of battery has not been cycled, lithium plating will not occur, so it can be used as a control group.

[0120] Table 2

[0121] Impedance value of Rct-p / mΩ Fresh battery 0.0165 97% SOH battery 0.0174 75% SOH battery 0.0169 Sto-97% SOH battery 0.0150

[0122] From Table 2, we can determine that:

[0123] The Rct-p ratio of a 97% SOH battery to that of a fresh battery is 105%, the Rct-p ratio of a 75% SOH battery to that of a fresh battery is 102%, and the Rct-p ratio of a Sto-97% SOH battery to that of a fresh battery is 91%.

[0124] Based on the mechanism described above, even if lithium plating occurs in the battery, it happens at the negative electrode. Therefore, theoretically, Rct-p is a constant value. However, due to factors such as measurement errors, Rct-p is not a constant value and may fluctuate. This can be seen from the Rct-p corresponding to the 97% SOH battery and the Rct-p corresponding to the 75% SOH battery.

[0125] Since it can be determined that lithium plating did not occur in the Sto-97% SOH battery, the 91% can be considered as an effect of error.

[0126] Based on this, and considering the impact of error, the first preset value can be set to 106%.

[0127] Through the Figure 4 The data in the table is organized to obtain the corresponding Table 3.

[0128] Table 3

[0129] Impedance value of Rct-n / mΩ Fresh battery 0.0696 97% SOH battery 0.0812 75% SOH battery 0.0814 Sto-97% SOH battery 0.0651

[0130] From Table 3, we can determine that:

[0131] The Rct-n ratio of a 97% SOH battery to that of a fresh battery is 116.7%, the Rct-n ratio of a 75% SOH battery to that of a fresh battery is 116.9%, and the Rct-n ratio of a Sto-97% SOH battery to that of a fresh battery is 93.5%.

[0132] Since it can be determined that the Sto-97% SOH battery did not undergo lithium plating, 93.5% can be considered as the effect of error; while 116.7% and 116.9% are both greater than 106%, indicating that the negative electrode charge transfer impedance has changed significantly. Based on the mechanism given above, this is due to lithium plating in the battery.

[0133] Therefore, based on the above analysis, it can be preliminarily determined that lithium plating occurred in both the 97% SOH battery and the 75% SOH battery.

[0134] To further verify the preliminary judgment, the batteries in the three states other than the fresh battery were heated and cooled respectively. Electrochemical impedance spectroscopy was then performed again on the cooled batteries in all three states, yielding the results. Figure 5 The spectrum shown has the horizontal axis representing the logarithm of frequency and the vertical axis representing the impedance value.

[0135] Through the Figure 5 The data in the table was organized to obtain the corresponding Table 4. Figure 5 In Table 4, "97% SOH-heat battery" refers to a battery with a health status of 97% after heat treatment, "75% SOH-heat battery" refers to a battery with a health status of 75% after heat treatment, and "Sto-97% SOH-heat battery" refers to a Sto-97% SOH battery after heat treatment.

[0136] Table 4

[0137] Impedance value of Rct-p / mΩ 97% SOH battery 0.0174 97% SOH-heat battery 0.0185 75% SOH battery 0.0169 75% SOH-heat battery 0.0253 Sto-97% SOH battery 0.0150 Sto-97% SOH-heat battery 0.0161

[0138] From Table 4, we can determine that:

[0139] The Rct-p of the 97% SOH-heat battery is significantly increased compared to that of the 97% SOH battery, and the ratio of Rct-p of the 97% SOH-heat battery to that of the 97% SOH battery is 106%.

[0140] The Rct-p of the 75% SOH-heat battery was significantly increased compared to that of the 75% SOH battery, and the ratio of Rct-p of the 75% SOH-heat battery to that of the 75% SOH battery was 150%.

[0141] The Rct-p of the Sto-97% SOH battery changed little before and after heating;

[0142] This is because lithium plating had already occurred in both the 97% SOH and 75% SOH batteries before heating. The heating process converts elemental lithium into lithium salt, which in turn alters the structure of the positive electrode surface, affecting the Li... + The insertion and extraction of lithium result in a significant increase in Rct-p after heating compared to before heating, which also verifies that lithium plating occurred in both 97% SOH and 75% SOH batteries.

[0143] Since the Sto-97%SOH battery does not undergo lithium plating before heating, even after heating, there will be no reaction in which elemental lithium is converted into lithium salt, so Rct-p does not change significantly.

[0144] Therefore, based on the results in Table 4 above, the second preset value can be set to 106%.

[0145] Similarly, through the Figure 5 The data in the table was organized to obtain the corresponding Table 5.

[0146] Table 5

[0147] Impedance value of Rct-n / mΩ 97% SOH battery 0.0812 97% SOH-heat battery 0.0855 75% SOH battery 0.0814 75% SOH-heat battery 0.1104 Sto-97% SOH battery 0.0651 Sto-97% SOH-heat battery 0.0603

[0148] From Table 5, we can determine that:

[0149] The Rct-n of the 97% SOH-heat battery is significantly increased compared to that of the 97% SOH battery, and the ratio of Rct-n of the 97% SOH-heat battery to that of the 97% SOH battery is 105%.

[0150] The Rct-n corresponding to the 75% SOH-heat battery also has a significant increase compared with the Rct-n corresponding to the 75% SOH battery, and the ratio of the Rct-n corresponding to the 75% SOH-heat battery to the Rct-n corresponding to the 75% SOH battery is 136%;

[0151] The Rct-n of the Sto-97% SOH battery changes little before and after heating;

[0152] This is because the 97% SOH battery and the 75% SOH battery have undergone lithium precipitation before heating, and the heating process causes the elemental lithium to react with the electrolyte to generate lithium salt, which affects the embedding and de-embedding of Li + , so that the Rct-n after heating is significantly increased than the Rct-n before heating, which also verifies that the 97% SOH battery and the 75% SOH battery have undergone lithium precipitation;

[0153] Since the Sto-97% SOH battery does not undergo lithium precipitation before heating, even after heating treatment, the reaction of converting elemental lithium into lithium salt does not occur, so the Rct-n does not change significantly.

[0154] Therefore, based on the results in Table 5 above, the third preset value can be set to 105%.

[0155] That is, if the Rct-p and the Rct-n both change significantly after the battery is heated, it indicates that the battery has undergone lithium precipitation before heating; if the Rct-p and the Rct-n both do not change significantly after the battery is heated, it indicates that the battery does not undergo lithium precipitation before heating;

[0156] The Rct-p and the Rct-n after heating can verify the result of the initial judgment, and finally the final judgment of whether the battery has undergone lithium precipitation can be given based on the conclusion obtained after heating, so as to improve the accuracy of the judgment result, avoid misjudgment, and provide accurate guidance for subsequent battery analysis and maintenance.

[0157] Based on the same inventive concept, the embodiments of the present application provide a battery lithium precipitation detection device, and the implementation principle of the detection device is similar to that of the foregoing detection method. The specific embodiments of the detection device can be referred to the specific implementation of the foregoing detection method, and the repeated parts will not be described herein.

[0158] Specifically, the battery lithium precipitation detection device provided by the embodiments of the present application, as shown in Figure 6 Impedance value of Rct-n / mΩ 97% SOH battery 97% SOH-heat battery 75% SOH battery 75% SOH-heat battery Sto-97% SOH battery Sto-97% SOH-heat battery Figure 6 Impedance value of Rct-n / mΩ 97% SOH battery 97% SOH-heat battery 75% SOH battery 75% SOH-heat battery Sto-97% SOH battery Sto-97% SOH-heat battery Figure 6 , can include:

[0159] The memory 601 is configured to store program instructions.

[0160] The processor 602 is configured to invoke the program instructions stored in the memory 601 to execute the above-mentioned battery lithium precipitation detection method according to the embodiments of the present application.

[0161] In some embodiments, the fresh battery can be pre-tested by electrochemical impedance to obtain an initial positive electrode charge transfer impedance and an initial negative electrode charge transfer impedance, and then the initial positive electrode charge transfer impedance and the initial negative electrode charge transfer impedance are stored in the memory. When it is necessary to determine whether the battery has lithium precipitation after the battery is used for a period of time, the initial positive electrode charge transfer impedance and the initial negative electrode charge transfer impedance can be read from the memory to determine whether the battery has lithium precipitation.

[0162] In addition, the storage format, storage location, etc. of the initial positive electrode charge transfer impedance and the initial negative electrode charge transfer impedance in the memory can be set according to actual needs, which are not limited herein.

[0163] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application belong to the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A method for detecting lithium plating in batteries, characterized in that, The application comprises: determining the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance of the battery according to the first test result obtained by electrochemical impedance testing on the battery; the test conditions of the electrochemical impedance testing include that the test temperature is 25 DEG C; determining whether the battery generates lithium precipitation according to at least the initial positive electrode charge transfer impedance, the initial negative electrode charge transfer impedance, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance; wherein the initial positive electrode charge transfer impedance and the initial negative electrode charge transfer impedance are determined according to the initial test result when the initial test result is obtained by performing the electrochemical impedance testing on a fresh battery corresponding to the battery; determining whether the battery generates lithium precipitation according to at least the initial positive electrode charge transfer impedance, the initial negative electrode charge transfer impedance, the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance, specifically comprising: calculating the first positive electrode ratio of the first positive electrode charge transfer impedance to the initial positive electrode charge transfer impedance; when the first positive electrode ratio is less than a first preset value, cooling the battery to room temperature after heating the battery according to the preset heating condition, and obtaining the second test result by performing the electrochemical impedance testing on the heated battery, determining the corresponding second positive electrode charge transfer impedance and the second negative electrode charge transfer impedance according to the second test result; determining whether the battery generates lithium precipitation according to the first positive electrode charge transfer impedance, the first negative electrode charge transfer impedance, the second positive electrode charge transfer impedance and the second negative electrode charge transfer impedance; determining whether the battery generates lithium precipitation according to the first positive electrode charge transfer impedance, the first negative electrode charge transfer impedance, the second positive electrode charge transfer impedance and the second negative electrode charge transfer impedance, specifically comprising: calculating the second positive electrode ratio of the second positive electrode charge transfer impedance to the first positive electrode charge transfer impedance, and the second negative electrode ratio of the second negative electrode charge transfer impedance to the first negative electrode charge transfer impedance; determining whether the second positive electrode ratio is greater than a second preset value and whether the second negative electrode ratio is greater than a third preset value; if yes, determining that the battery generates lithium precipitation; if no, determining that the battery does not generate lithium precipitation.

2. The battery lithium plating detection method of claim 1, wherein, The preset heating condition includes maintaining at 60 DEG C to 100 DEG C for a preset time.

3. The battery lithium plating detection method of claim 1, wherein, The application further comprises: determining the degree of lithium precipitation of the battery according to the first negative electrode charge transfer impedance and the second negative electrode charge transfer impedance.

4. The battery lithium plating detection method of claim 3, wherein, determining the degree of lithium precipitation of the battery according to the first negative electrode charge transfer impedance and the second negative electrode charge transfer impedance, specifically comprising: calculating the ratio of the second negative electrode charge transfer impedance to the first negative electrode charge transfer impedance; looking up the degree of lithium precipitation corresponding to the second negative electrode ratio according to the corresponding relationship between the ratio and the degree of lithium precipitation; determining the looked-up degree of lithium precipitation as the degree of lithium precipitation of the battery.

5. The lithium plating detection method of any one of claims 1-4, wherein, determining the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance of the battery according to the first test result, specifically comprising: The first test result is analyzed by using a relaxation time distribution DRT analysis algorithm to obtain the first positive electrode charge transfer impedance and the first negative electrode charge transfer impedance. 6.A device for detecting lithium plating of a battery, characterized by The method comprises the steps of: a memory for storing program instructions; a processor for calling the program instructions stored in the memory, and executing the battery lithium precipitation detection method according to any one of claims 1-5 according to the obtained program.

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