Lithium battery formation effect evaluation method, device and equipment and storage medium

Abstract

The invention discloses a lithium battery formation effect evaluation method, device and equipment and a storage medium. A plurality of different formation schemes are executed on the lithium battery, the lithium battery is formed to a preset charge state, different formation schemes have different formation parameters, and each formation scheme has different formation parameters. The method comprises the following steps: acquiring alternating-current impedance test data at each test temperature obtained by performing alternating-current impedance test on a formed lithium battery at a plurality of different test temperatures, analyzing the alternating-current impedance test data, and determining a critical temperature at which a side reaction occurs in the lithium battery, the critical temperature is the target test temperature at which the alternating current impedance deviates relative to other test temperatures, and the formation scheme with the lowest critical temperature is determined as the optimal formation scheme, so that the problem that the formation effects of different formation schemes cannot be evaluated due to transverse comparison of the alternating current impedance at a single temperature is avoided; and the evaluation stability and accuracy are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to lithium battery formation technology, and in particular to a lithium battery formation effect evaluation method, device, equipment and storage medium. BACKGROUND

[0002] Lithium battery formation refers to the first small current charge and discharge of the just completed lithium ion battery to activate the electrode material and form a stable SEI film (solid electrolyte interface film), thereby optimizing the key process of battery performance.

[0003] At present, the evaluation of formation effect is less in the manufacturing field, and the common methods are interface disassembly, capacity determination, AC impedance test, etc., but they are all single-dimensional (such as capacity, AC impedance) horizontal comparison at a single temperature. Such comparison often cannot evaluate the formation effect of different formation schemes. SUMMARY

[0004] The present application provides a lithium battery formation effect evaluation method, device, equipment and storage medium to avoid the problem that the horizontal comparison of AC impedance at a single temperature cannot evaluate the formation effect of different formation schemes, and improve the evaluation stability and accuracy.

[0005] In a first aspect, the present application provides a lithium battery formation effect evaluation method, comprising:

[0006] Performing a plurality of different formation schemes on the lithium battery, and forming the lithium battery to a preset state of charge, wherein the different formation schemes have different formation parameters;

[0007] For each formation scheme, obtaining AC impedance test data at each test temperature obtained by performing AC impedance test on the formed lithium battery at a plurality of different test temperatures;

[0008] Analyzing the AC impedance test data to determine the critical temperature at which the side reaction occurs inside the lithium battery, the critical temperature being the target test temperature at which the AC impedance deviates from other test temperatures;

[0009] Determining the formation scheme with the lowest critical temperature as the optimal formation scheme.

[0010] Optionally, analyzing the AC impedance test data to determine the critical temperature at which the side reaction occurs inside the lithium battery, the critical temperature being the target test temperature at which the AC impedance deviates from other test temperatures, comprises:

[0011] Generating an AC impedance spectrum at different test temperatures based on the AC impedance test data;

[0012] determining charge transfer impedances at different test temperatures based on the alternating current impedance spectrum;

[0013] fitting the charge transfer impedances at different test temperatures by using an Arrhenius formula, and determining a critical temperature at which a side reaction occurs inside the lithium battery based on a fitting result, the critical temperature being a target test temperature at which the alternating current impedance deviates from other test temperatures.

[0014] Optionally, the fitting the charge transfer impedances at different test temperatures by using an Arrhenius formula, and determining a critical temperature at which a side reaction occurs inside the lithium battery based on a fitting result, the critical temperature being a target test temperature at which the alternating current impedance deviates from other test temperatures, comprises:

[0015] linearly fitting the charge transfer impedances at different test temperatures with the reciprocal of the test temperatures as the horizontal axis and the natural logarithm of the charge transfer impedances as the vertical axis;

[0016] calculating a fitting degree of the fitting line;

[0017] determining whether the fitting degree is less than a preset value;

[0018] if yes, removing the charge transfer impedance corresponding to the lowest test temperature from the current charge transfer impedance data, and returning to perform the linearly fitting the charge transfer impedances at different test temperatures with the reciprocal of the test temperatures as the horizontal axis and the natural logarithm of the charge transfer impedances as the vertical axis until the fitting degree is greater than or equal to the preset value;

[0019] when the fitting degree is greater than or equal to the preset value, taking the lowest test temperature in the current data set as the critical temperature at which a side reaction occurs inside the lithium battery.

[0020] Optionally, a calculation formula of the fitting degree is:

[0021]

[0022] wherein, R 2 is the fitting degree, y i is an actual value of the charge transfer impedance, is a predicted value of the charge transfer impedance after linear fitting, is an average value of the actual value of the charge transfer impedance.

[0023] Optionally, the test temperatures range from 0℃ to 45℃.

[0024] Optionally, when the charge transfer impedances at different test temperatures are fitted by using an Arrhenius formula, the method further comprises:

[0025] when the fitting degree is greater than or equal to a preset value, calculating an absolute value of a slope value of the current fitting straight line;

[0026] calculating a product of the absolute value of the slope value and a gas molar constant as an activation energy of the lithium battery using the formation scheme.

[0027] Optionally, the lithium battery formation effect evaluation method further comprises:

[0028] comparing the activation energies of the lithium batteries of different formation schemes;

[0029] determining the formation scheme with the lowest activation energy as the optimal formation scheme.

[0030] In a second aspect, the present application provides a lithium battery formation effect evaluation device, comprising:

[0031] a formation scheme execution module configured to execute a plurality of different formation schemes on a lithium battery to form the lithium battery to a preset state of charge, wherein the different formation schemes have different formation parameters;

[0032] a test data acquisition module configured to, for each formation scheme, acquire alternating current impedance test data of the lithium battery after formation at each test temperature obtained by performing alternating current impedance tests on the lithium battery at a plurality of different test temperatures;

[0033] a data analysis module configured to analyze the alternating current impedance test data and determine a critical temperature at which a side reaction occurs inside the lithium battery, the critical temperature being a target test temperature at which the alternating current impedance deviates from other test temperatures;

[0034] a formation effect evaluation module configured to determine the formation scheme with the lowest critical temperature as the optimal formation scheme.

[0035] In a third aspect, the present application provides an electronic device, comprising:

[0036] one or more processors;

[0037] a storage device configured to store one or more programs;

[0038] when the one or more programs are executed by the one or more processors, the one or more processors implement the lithium battery formation effect evaluation method provided in the first aspect of the present application.

[0039] In a fourth aspect, the present application provides a computer readable storage medium having a computer program stored thereon, the program being executed by a processor to implement the lithium battery formation effect evaluation method provided in the first aspect of the present application.

[0040] The lithium battery formation effect evaluation method provided by the application executes different formation schemes on the lithium battery, forms the lithium battery to a preset state of charge, and the different formation schemes have different formation parameters. For each formation scheme, the AC impedance test data of the lithium battery after formation at each test temperature is obtained by performing AC impedance tests on the lithium battery at different test temperatures. The AC impedance test data is analyzed to determine the critical temperature of the side reaction occurring inside the lithium battery. The critical temperature is the target test temperature at which the AC impedance deviates from other test temperatures. The formation scheme with the lowest critical temperature is determined as the optimal formation scheme. The problem of being unable to evaluate the formation effect of different formation schemes due to the horizontal comparison of AC impedance at a single temperature is avoided, and the evaluation stability and accuracy are improved.

[0041] It should be understood that the content described in this part is not intended to identify key or important features of the embodiments of the application, nor is it used to limit the scope of the application. Other features of the application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0043] Figure 1 A flowchart of a lithium battery formation effect evaluation method provided by the application;

[0044] Figure 2 A formation effect evaluation schematic diagram of the prior art;

[0045] Figure 3 、 4 A formation effect evaluation schematic diagram of the A formation scheme of the application;

[0046] Figure 5 、 6 A formation effect evaluation schematic diagram of the B formation scheme of the application;

[0047] Figure 7 A formation effect evaluation schematic diagram of the C formation scheme of the application;

[0048] Figure 8 A structure schematic diagram of a lithium battery formation effect evaluation device provided by the application;

[0049] Figure 9 A structure schematic diagram of an electronic device provided by the application.

[0050] The specific embodiments of the present application have been shown by the above drawings, and will be described in more detail hereinafter. These drawings and the written description are not intended to restrict the scope of the present application in any way, but to explain the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0051] In order to make the technical personnel in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0052] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0053] Figure 1 A flowchart of a lithium battery formation effect evaluation method provided by the present application, the present embodiment evaluates the lithium battery formation effect based on alternating current impedance test data at multiple different test temperatures, which can be executed by a lithium battery formation effect evaluation device provided by the present application, which can be realized by software and / or hardware, and is usually configured in an electronic device, such as Figure 1 The lithium battery formation effect evaluation method includes the following steps:

[0054] S101, multiple different formation schemes are executed on the lithium battery, and the lithium battery is formed to a preset state of charge.

[0055] The lithium battery can be a battery cell or a battery pack, which is not limited in the present application. Different formation schemes have different formation parameters. For example, different formation schemes have different charging currents. In the embodiments of the present application, multiple different formation schemes are executed on multiple lithium batteries of the same batch (having the same performance parameters), and the lithium battery is formed to a preset state of charge, so as to ensure the consistency of the state of charge and exclude the influence of the state of charge on the test.

[0056] The formation process is usually carried out at a high temperature (30-60°C), and in some embodiments of the present application, the lithium battery is left to stand at the formation temperature for 24-48 hours after the formation is completed to ensure that the reaction in the formation process is complete. Then the lithium battery is left to stand at room temperature for 5-8 hours for AC impedance test.

[0057] S102, for each formation scheme, obtaining the AC impedance test data at each test temperature obtained by performing AC impedance test on the lithium battery after formation at a plurality of different test temperatures.

[0058] In embodiments of the present application, for each formation scheme, the AC impedance test data at each test temperature obtained by performing AC impedance test on the lithium battery after formation at a plurality of different test temperatures is obtained. The AC impedance test is a test method for controlling the AC voltage of the electrode (or the AC current of the electrode) to change regularly in a small amplitude (generally less than 10 mV) sinusoidal wave (or pulse), and then measuring the AC impedance of the electrode, and further calculating the electrochemical parameters of the electrode. In embodiments of the present application, the frequency range of the AC voltage is 10 KHz-0.01 Hz, and the amplitude is 5 mV.

[0059] In some embodiments of the present application, the test temperature range of the AC impedance test is 0-45°C. Exemplarily, in this temperature range, a plurality of test temperatures are taken at a preset temperature interval. Exemplarily, 5°C is taken as a gradient, and 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C and 45°C are taken as test temperatures, respectively. Of course, in other embodiments of the present application, in order to improve the fitting accuracy, the interval temperature can be smaller, for example, 1°C or 2°C, which will not be described herein again.

[0060] S103, analyzing the AC impedance test data to determine the critical temperature of the side reaction occurring inside the lithium battery, and the critical temperature is the target test temperature at which the AC impedance deviates from other test temperatures.

[0061] In embodiments of the present application, the AC impedance test data is analyzed to determine the target test temperature at which the AC impedance deviates from other test temperatures, for example, the AC impedance at other test temperatures can well approach the fitting curve, but the AC impedance at one of the test temperatures deviates from the fitting curve obviously, and the test temperature at which the AC impedance deviates obviously is taken as the target temperature, and the target temperature is the critical temperature of the side reaction occurring inside the lithium battery. The side reaction can be lithium precipitation, electrolyte decomposition to produce gas, SEI film decomposition, etc., which is not limited herein.

[0062] In some embodiments of the present application, the step S103 comprises the following sub-steps:

[0063] S1031, generating an AC impedance spectrum at different test temperatures based on the AC impedance test data.

[0064] In the embodiments of the present application, the AC impedance test data generates an AC impedance spectrum at different test temperatures. In the embodiments of the present application, the AC impedance spectrum is a Nyquist spectrum, the horizontal axis of the Nyquist spectrum represents the real part of the lithium battery impedance, and the vertical axis represents the imaginary part of the lithium battery impedance. The left side of the Nyquist spectrum represents the high frequency region, and the right side represents the low frequency region. Each point of the Nyquist spectrum corresponds to an impedance at a specific frequency.

[0065] S1032, determining the charge transfer impedance at different test temperatures based on the AC impedance spectrum.

[0066] The Nyquist spectrum shows a semicircle in the high frequency region, and the diameter of the circle is the charge transfer impedance R ct .

[0067] S1033, fitting the charge transfer impedance at different test temperatures using the Arrhenius formula, and determining the critical temperature of the side reaction inside the lithium battery based on the fitting result, the critical temperature being the target test temperature at which the AC impedance deviates from other test temperatures.

[0068] In the embodiments of the present application, the charge transfer impedance at different test temperatures is fitted using the Arrhenius formula, and the critical temperature of the side reaction inside the lithium battery is determined based on the fitting result, the critical temperature being the target test temperature at which the AC impedance deviates from other test temperatures.

[0069] The Arrhenius formula quantitatively represents the relationship between the reaction rate constant and the temperature, and its indefinite integral expression is:

[0070]

[0071] wherein, R ct is the charge transfer impedance, A is the pre-exponential factor, E a is the activation energy of the lithium battery, R is the molar gas constant, and T is the Kelvin temperature.

[0072] Further, the above formula is rewritten as:

[0073]

[0074] From the above formula, it can be seen that the natural logarithm lnR ct of the charge transfer impedance and the reciprocal of the test temperature are linearly related, and the absolute value of the slope of the linear function is

[0075] In the embodiment of the present application, the process of determining the critical temperature by fitting is as follows:

[0076] 1. Linearly fitting the charge transfer impedance at different test temperatures with the reciprocal of the test temperature as the horizontal axis and the natural logarithm of the charge transfer impedance as the vertical axis.

[0077] Since the natural logarithm lnR ct of the charge transfer impedance and the reciprocal of the test temperature are linearly related, in the embodiment of the present application, the charge transfer impedance at different test temperatures is linearly fitted with the reciprocal of the test temperature as the horizontal axis and the natural logarithm lnR ct of the charge transfer impedance as the vertical axis.

[0078] 2. Calculating the fitting degree of the fitted straight line.

[0079] After each fitting, the fitting degree of the fitted straight line is calculated. The fitting degree test is a test on the fitted straight line, comparing the fitting degree of the predicted results and the actual data distribution. The greater the fitting degree, the closer the fitted straight line is to the actual data distribution.

[0080] In the embodiment of the present application, the calculation formula of the fitting degree is as follows:

[0081]

[0082] Wherein, R 2 is the fitting degree, y i is the actual value of the charge transfer impedance, is the predicted value of the charge transfer impedance after linear fitting, is the average value of the actual value of the charge transfer impedance.

[0083] 3. Determining whether the fitting degree is less than a preset value.

[0084] In the embodiment of the present application, it is determined whether the fitting degree is less than a preset value. If yes, it means that the deviation between the currently fitted straight line and the actual data distribution is large. Exemplarily, the preset value can be set to 95%.

[0085] 4. If yes, the charge transfer impedance corresponding to the lowest test temperature is removed from the current charge transfer impedance data, and the step of linearly fitting the charge transfer impedance at different test temperatures with the reciprocal of the test temperature as the horizontal axis and the natural logarithm of the charge transfer impedance as the vertical axis is executed again. In this way, the above fitting process is repeated until the fitting degree is greater than or equal to the preset value.

[0086] 5. When the fitting degree is greater than or equal to the preset value, the lowest test temperature in the current data set is taken as the critical temperature of the side reaction inside the lithium battery.

[0087] For example, first, the charge transfer impedance at all test temperatures (5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃) is fitted with the reciprocal of the test temperature as the horizontal axis and the natural logarithm of the charge transfer impedance as the vertical axis to obtain a fitting straight line, and the fitting degree of the fitting straight line is calculated. If the fitting degree is less than the preset value, the charge transfer impedance data corresponding to the test temperature of 0℃ is removed, and the data is fitted again based on the remaining data to calculate the fitting degree. If the fitting degree is greater than or equal to the preset value, the lowest test temperature (i.e. 5℃) in the remaining data at this time is taken as the critical temperature of the side reaction inside the lithium battery. If the fitting degree is still less than the preset value, the above process is repeated until the fitting degree is greater than or equal to the preset value. When the fitting degree is greater than or equal to the preset value, the lowest test temperature in the current data set is taken as the critical temperature of the side reaction inside the lithium battery. It should be noted that in order to improve the accuracy of the critical temperature, the interval of the test temperature can be smaller.

[0088] S104. Determine the formation scheme with the lowest critical temperature as the optimal formation scheme.

[0089] The lower the critical temperature of the side reaction, the better and more stable the performance of the lithium battery using the formation scheme. Therefore, in the embodiments of the present application, the formation scheme with the lowest critical temperature is determined as the optimal formation scheme.

[0090] As described above, the natural logarithm lnR ct of the charge transfer impedance is linearly related to the reciprocal of the test temperature , and the absolute value of the slope of the linear function is Therefore, in some embodiments of the present application, when the fitting degree is greater than or equal to the preset value, the absolute value of the slope of the current fitting straight line is calculated, and then the product of the absolute value of the slope and the gas molar constant R is taken as the activation energy E a of the lithium battery using the formation scheme. a Then, the activation energies of the lithium batteries of different formation schemes are compared. The smaller the activation energy E a of the lithium battery, the smaller the energy barrier of the electrochemical reaction inside the lithium battery, the easier the electrochemical reaction inside the lithium battery, and the better the performance of the lithium battery. Therefore, the formation scheme with the lowest activation energy is determined as the optimal formation scheme.

[0091] It should be noted that in some embodiments of the present invention, the critical temperature and activation energy can also be combined for comprehensive evaluation. For example, each critical temperature can be mapped to a corresponding score; the lower the critical temperature, the higher the score. Similarly, each activation energy can be mapped to a corresponding score; the lower the activation energy, the higher the score. Critical temperatures and activation energies are assigned corresponding weights, and then the scores for the critical temperature and activation energy of the formation scheme are weighted and summed to obtain a total score. The higher the total score, the better the formation scheme.

[0092] The lithium battery formation effect evaluation method provided by this invention performs multiple different formation schemes on the lithium battery to form it to a preset state of charge. Different formation schemes have different formation parameters. For each formation scheme, AC impedance test data is obtained at each test temperature by performing AC impedance tests on the formed lithium battery at multiple different test temperatures. The AC impedance test data is analyzed to determine the critical temperature at which side reactions occur inside the lithium battery. The critical temperature is the target test temperature at which the AC impedance deviates from other test temperatures. The formation scheme with the lowest critical temperature is determined as the optimal formation scheme. This avoids the problem of being unable to evaluate the formation effect of different formation schemes due to the lateral comparison of AC impedance at a single temperature, thus improving the stability and accuracy of the evaluation.

[0093] For example, to verify the evaluation method of the present invention, three formation schemes (A, B, and C) are set up. For each formation scheme, AC impedance tests are performed at test temperatures (5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, and 45℃), with an AC voltage frequency range of 10kHz-0.01Hz and an amplitude of 5mV. The evaluation method of the present invention is used to evaluate the formation effect. In addition, a comparative example is also set up, which generally sets up three formation schemes (A, B, and C). For each formation scheme, AC impedance tests are performed at room temperature (25℃), with an AC voltage frequency range of 10kHz-0.01Hz and an amplitude of 5mV. The existing evaluation method is used to evaluate the formation effect, that is, to determine the range of charge transfer impedance in the AC impedance test of each formation scheme, and then select the formation scheme with the minimum charge transfer impedance as the optimal formation scheme.

[0094] Figure 2 This is a schematic diagram illustrating the formation effect evaluation of existing technologies. The vertical axis represents charge transfer impedance. Figure 3 , 4 This is a schematic diagram illustrating the evaluation of the formation effect of formation scheme A of the present invention. Figure 5 , 6 This is a schematic diagram illustrating the evaluation of the formation effect of formation scheme B of the present invention. Figure 7 This is a schematic diagram illustrating the formation effect evaluation of the formation scheme C of the present invention.Figures 3-7 In one embodiment, a series of data points represent the flow impedance (charge transfer impedance) of the battery at different test voltage frequencies at a certain test temperature. As shown in FIG. 1, the existing formation effect evaluation method obtains the range of charge transfer impedance of each formation scheme. However, since the ranges of charge transfer impedance of different formation schemes overlap, for example, the ranges of charge transfer impedance of the A formation scheme and the B formation scheme overlap, it is not possible to directly determine the pros and cons of the A formation scheme and the B formation scheme. Figure 2 As shown in FIG. 2, the evaluation method of the present application has a good fitting degree (fitting degree R 2 = 0.9902) for the AC impedance data of the A formation scheme in the test temperature range of 15℃-45℃, and the activation energy E a = 47.54kJ / mol. However, the fitting degree R 2 = 0.9053 for the AC impedance data in the test temperature range of 10℃-45℃ is less than the preset value, indicating that the critical temperature of the A formation scheme is between 10℃-15℃, and the present application takes 10℃ as the critical temperature. Figure 3 As shown in FIG. 3, the evaluation method of the present application has a good fitting degree (fitting degree R 2 = 0.9942) for the AC impedance data of the B formation scheme in the test temperature range of 10℃-45℃, and the activation energy E a = 40.04kJ / mol. However, the fitting degree R 2 = 0.7654 for the AC impedance data in the test temperature range of 5℃-45℃ is less than the preset value, indicating that the critical temperature of the B formation scheme is between 5℃-10℃, and the present application takes 5℃ as the critical temperature. 4 As shown in FIG. 4, the evaluation method of the present application has a good fitting degree (fitting degree R 2 = 0.9918) for the AC impedance data of the C formation scheme in the test temperature range of 5℃-45℃, and the activation energy E a = 33.18kJ / mol, indicating that the critical temperature is below 5℃. Therefore, considering the critical temperature and the activation energy, the critical temperature and the activation energy of the C formation scheme are the lowest among the three formation schemes, and thus it can be confirmed that the C formation scheme is the optimal formation scheme among the three. Figure 5 6 Figure 7

[0095] Figure 8 As shown in FIG. 5, the lithium battery formation effect evaluation device provided by the present application comprises: Figure 8 As shown in FIG. 6, the lithium battery formation effect evaluation device comprises:

[0096] ​​​The formation scheme execution module 201 is configured to execute a plurality of different formation schemes on the lithium battery to form the lithium battery to a preset state of charge, wherein the different formation schemes have different formation parameters;

[0097] The test data acquisition module 202 is configured to acquire, for each formation scheme, alternating current impedance test data at each test temperature obtained by performing alternating current impedance tests on the lithium battery after formation at a plurality of different test temperatures;

[0098] The data analysis module 203 is configured to analyze the alternating current impedance test data to determine a critical temperature at which a side reaction occurs inside the lithium battery, the critical temperature being a target test temperature at which the alternating current impedance deviates from other test temperatures;

[0099] The formation effect evaluation module 204 is configured to determine the formation scheme with the lowest critical temperature as the optimal formation scheme.

[0100] In some embodiments of the present application, the data analysis module 203 comprises:

[0101] The impedance spectrum generation unit is configured to generate alternating current impedance spectra at different test temperatures based on the alternating current impedance test data;

[0102] The charge transfer impedance determination unit is configured to determine charge transfer impedances at different test temperatures based on the alternating current impedance spectra;

[0103] The critical temperature determination unit is configured to fit the charge transfer impedances at different test temperatures using an Arrhenius formula, and determine the critical temperature at which a side reaction occurs inside the lithium battery based on the fitting result, the critical temperature being a target test temperature at which the alternating current impedance deviates from other test temperatures.

[0104] In some embodiments of the present application, the critical temperature determination unit comprises:

[0105] The linear fitting subunit is configured to linearly fit the charge transfer impedances at different test temperatures with the reciprocal of the test temperatures as the horizontal axis and the natural logarithm of the charge transfer impedances as the vertical axis;

[0106] The fitting degree calculation subunit is configured to calculate the fitting degree of the fitting straight line;

[0107] The judgment subunit is configured to judge whether the fitting degree is less than a preset value;

[0108] The returning execution subunit is configured to, when the fitting degree is less than the preset value, eliminate the charge transfer impedance corresponding to the lowest test temperature from the current charge transfer impedance data, and return to execute the step of linearly fitting the charge transfer impedances at different test temperatures with the reciprocal of the test temperature as the horizontal axis and the natural logarithm of the charge transfer impedance as the vertical axis, until the fitting degree is greater than or equal to the preset value.

[0109] The critical temperature determination subunit is configured to, when the fitting degree is greater than or equal to the preset value, determine the lowest test temperature in the current data set as the critical temperature at which the side reaction occurs inside the lithium battery.

[0110] In some embodiments of the present application, the calculation formula of the fitting degree is:

[0111]

[0112] wherein R 2 is the fitting degree, y i is the actual value of the charge transfer impedance, is the predicted value of the charge transfer impedance after linear fitting, is the average value of the actual value of the charge transfer impedance.

[0113] In some embodiments of the present application, the test temperature ranges from 0℃ to 45℃.

[0114] In some embodiments of the present application, the lithium battery formation effect evaluation device further comprises:

[0115] The activation energy calculation module is configured to, when fitting the charge transfer impedances at different test temperatures by using the Arrhenius formula, calculate the absolute value of the slope value of the current fitting straight line when the fitting degree is greater than or equal to the preset value.

[0116] The product of the absolute value of the slope value and the gas molar constant is calculated as the activation energy of the lithium battery using the formation scheme.

[0117] In some embodiments of the present application, the lithium battery formation effect evaluation device further comprises:

[0118] The activation energy comparison module is configured to compare the activation energies of the lithium batteries using different formation schemes.

[0119] The formation effect evaluation module 204 is further configured to determine the formation scheme with the lowest activation energy as the optimal formation scheme.

[0120] The lithium battery formation effect evaluation device described above can execute the lithium battery formation effect evaluation method provided in the foregoing embodiments of the present application, and has the corresponding functional modules and beneficial effects of executing the lithium battery formation effect evaluation method.

[0121] Figure 9 A block diagram of an electronic device is provided for the present disclosure. The electronic device is intended to represent various forms of digital computers, such as laptops, desktops, tablets, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The electronic device can also represent various forms of mobile devices, such as personal digital assistants, cellular telephones, smart phones, wearable devices (e.g., headsets, glasses, watches, etc.), and other similar computing devices. The components shown here, their connections and relationships, and their functions, are meant to be examples only, and are not meant to limit implementations of the present disclosure described and / or claimed in this document.

[0122] As shown in Figure 9 The electronic device includes at least one processor 11, and a memory, such as a read-only memory (ROM) 12, a random access memory (RAM) 13, etc., connected to the at least one processor 11 in communication, where the memory stores computer programs executable by the at least one processor. The processor 11 can perform various appropriate actions and processes according to the computer programs stored in the read-only memory (ROM) 12 or loaded into the random access memory (RAM) 13 from the storage unit 18. In the RAM 13, various programs and data required for the operation of the electronic device can also be stored. The processor 11, the ROM 12, and the RAM 13 are connected to each other through a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0123] A plurality of components in the electronic device are connected to the I / O interface 15, including an input unit 16, such as a keyboard, a mouse, etc., an output unit 17, such as various types of displays, speakers, etc., a storage unit 18, such as a magnetic disk, an optical disk, etc., and a communication unit 19, such as a network card, a modem, a wireless communication transceiver, etc. The communication unit 19 allows the electronic device to exchange information / data with other devices through a computer network, such as the Internet, and / or various telecommunications networks.

[0124] The processor 11 can be various general and / or special-purpose processing components with processing and computing capabilities. Some examples of the processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any appropriate processor, controller, microcontroller, etc. The processor 11 performs various methods and processes described above, such as the lithium battery formation effect evaluation method.

[0125] In some embodiments, the lithium battery formation effect evaluation method can be implemented as a computer program tangibly embodied in a computer readable storage medium, e.g., storage unit 18. In some embodiments, parts or all of the computer program can be loaded and / or installed onto the electronic device via, e.g., ROM 12 and / or communication unit 19. When the computer program is loaded into RAM 13 and executed by processor 11 as described above, one or more steps of the above-described lithium battery formation effect evaluation method can be performed. Alternatively, in other embodiments, processor 11 can be configured to perform the lithium battery formation effect evaluation method by other any suitable means, e.g., by way of firmware.

[0126] Various implementations of the systems and techniques described above can be realized in digital electronic circuitry, integrated circuitry, specially designed application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), computer hardware, firmware, software, and / or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and / or interpretable on a programmable system including at least one programmable processor, which can be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device.

[0127] Computer programs implementing methods of the present application can be written in any combination of one or more programming languages. These computer programs can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the computer program, when executed, implements the functions / acts specified in the flowcharts and / or block diagrams. The computer program can be executed entirely on a machine, partially on a machine, partially on a machine and partially on a remote machine or entirely on a remote machine or server.

[0128] In the context of the present application, a computer-readable storage medium can be a tangible medium that can contain or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. A computer-readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium can be a machine-readable signal medium. More specific examples of a machine-readable storage medium will include one or more lines of a program of instructions in a transitory signal, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0129] To provide for interaction with a user, the systems and techniques described here can be implemented on an electronic device having a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user and a keyboard and a pointing device (e.g., a mouse or a trackball) by which the user can provide input to the electronic device. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form, including acoustic, speech, or tactile input.

[0130] The systems and techniques described here can be implemented in a computing system that includes a back end component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front end component (e.g., a user computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such back end, middleware, or front end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include a local area network (LAN), a wide area network (WAN), a blockchain network, and the Internet.

[0131] The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. Servers can be cloud servers, also known as cloud computing servers or cloud hosts, which are a host product in the cloud computing service system to solve the defects of great management difficulty and weak business scalability in traditional physical hosts and VPS services.

[0132] The embodiment of the present application also provides a computer program product comprising a computer program which, when executed by a processor, implements the lithium battery formation effect evaluation method provided by any embodiment of the present application.

[0133] The computer program product can be written in one or more programming languages or combinations of languages including object-oriented languages, such as Java, Smalltalk, C++, and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0134] It should be understood that various forms of flow shown above can be used to reorder, add or delete steps. For example, the steps described in the present application can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions of the present application can be achieved, which are not limited herein.

[0135] The above detailed description does not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for evaluating formation effect of a lithium battery, characterized by, The method comprises the following steps: performing a plurality of different formation schemes on a lithium battery to form the lithium battery to a preset state of charge, wherein different formation schemes have different formation parameters; for each formation scheme, obtaining AC impedance test data of the lithium battery after formation at each test temperature obtained by performing AC impedance test on the lithium battery at a plurality of different test temperatures; analyzing the AC impedance test data to determine a critical temperature at which a side reaction occurs inside the lithium battery, the critical temperature being a target test temperature at which the AC impedance deviates from other test temperatures; determining the formation scheme with the lowest critical temperature as the optimal formation scheme.

2. The lithium battery formation effect evaluation method according to claim 1, characterized by, The method of analyzing the AC impedance test data to determine a critical temperature at which a side reaction occurs inside the lithium battery, the critical temperature being a target test temperature at which the AC impedance deviates from other test temperatures, comprises: generating an AC impedance spectrum at different test temperatures based on the AC impedance test data; determining charge transfer impedance at different test temperatures based on the AC impedance spectrum; fitting the charge transfer impedance at different test temperatures using the Arrhenius formula, and determining the critical temperature at which a side reaction occurs inside the lithium battery based on the fitting result, the critical temperature being a target test temperature at which the AC impedance deviates from other test temperatures.

3. The lithium battery formation effect evaluation method according to claim 2, characterized by, The method of fitting the charge transfer impedance at different test temperatures using the Arrhenius formula, and determining the critical temperature at which a side reaction occurs inside the lithium battery based on the fitting result, the critical temperature being a target test temperature at which the AC impedance deviates from other test temperatures, comprises: linearly fitting the charge transfer impedance at different test temperatures with the reciprocal of the test temperature as the horizontal axis and the natural logarithm of the charge transfer impedance as the vertical axis; calculating the fitting degree of the fitting straight line; determining whether the fitting degree is less than a preset value; if yes, removing the charge transfer impedance corresponding to the lowest test temperature from the current charge transfer impedance data, and returning to the step of linearly fitting the charge transfer impedance at different test temperatures with the reciprocal of the test temperature as the horizontal axis and the natural logarithm of the charge transfer impedance as the vertical axis until the fitting degree is greater than or equal to the preset value; when the fitting degree is greater than or equal to the preset value, taking the lowest test temperature in the current data set as the critical temperature at which a side reaction occurs inside the lithium battery.

4. The lithium battery formation effect evaluation method according to claim 3, characterized by, The calculation formula of the fitting degree is: wherein R 2 is the degree of fit, y i is the actual value of the charge transfer impedance, is the predicted value of the charge transfer impedance after linear fitting, is the average of the actual values of the charge transfer impedance.

5. The lithium battery formation effect evaluation method according to claim 1, characterized by, The test temperature ranges from 0°C to 45°C.

6. The lithium battery formation effect evaluation method according to claim 3, characterized by, When fitting the charge transfer impedance at different test temperatures using the Arrhenius formula, the method further comprises: when the fitting degree is greater than or equal to the preset value, calculating the absolute value of the slope value of the current fitting straight line; calculating the product of the absolute value of the slope value and the gas molar constant as the activation energy of the lithium battery using the formation scheme.

7. The lithium battery formation effect evaluation method according to claim 6, characterized by, The method further comprises: comparing the activation energies of the lithium batteries using different formation schemes; determining the formation scheme with the lowest activation energy as the optimal formation scheme.

8. A lithium battery formation effect evaluation device characterized by comprising: The method comprises the following steps: The formation scheme execution module is configured to execute a plurality of different formation schemes on the lithium battery to form the lithium battery to a preset state of charge, wherein the different formation schemes have different formation parameters; The test data acquisition module is configured to, for each formation scheme, acquire AC impedance test data of the lithium battery at each test temperature obtained by performing AC impedance test on the lithium battery at a plurality of different test temperatures after formation; The data analysis module is configured to analyze the AC impedance test data to determine a critical temperature at which a side reaction occurs inside the lithium battery, the critical temperature being a target test temperature at which the AC impedance deviates from other test temperatures; The formation effect evaluation module is configured to determine the formation scheme with the lowest critical temperature as an optimal formation scheme.

9. An electronic device, comprising: One or more processors; A storage device configured to store one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors are caused to implement the lithium battery formation effect evaluation method according to any one of claims 1-7. The program is executed by the processor to implement the lithium battery formation effect evaluation method according to any one of claims 1-7.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, ​

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