Method, device and equipment for determining solid-phase diffusion coefficient of electrode material and storage medium

Abstract

This application provides a method, apparatus, device, and storage medium for determining the solid-phase diffusion coefficient of an electrode material. The method includes: acquiring pulse relaxation data of a battery; wherein the pulse relaxation data is the potential of the positive and / or negative electrodes of the battery within a preset time period after applying a pulse current to the battery in its state of charge, and the preset time period is shorter than the time required for the battery to reach its equilibrium potential; fitting the pulse relaxation data using a preset approximation function to obtain fitted data and an equilibrium potential; and determining the solid-phase diffusion coefficient of the battery's electrode material based on the fitted data and the equilibrium potential. This application's embodiment uses a preset approximation function to fit the pulse relaxation data within a short time period, thereby obtaining fitted data when the battery reaches potential equilibrium, and then obtaining the solid-phase diffusion coefficient based on the fitted data and the equilibrium potential. Therefore, it shortens the battery's resting time and improves the efficiency of obtaining the solid-phase diffusion coefficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a method and device for determining the solid-phase diffusion coefficient of electrode materials, an equipment and a storage medium. BACKGROUND

[0002] The charging and discharging process of a battery mainly includes the diffusion of metal ions contained in the electrode material in the positive and negative electrode solid phase, the diffusion in the electrolyte and the charge exchange process at the electrode interface, wherein the solid-phase diffusion is relatively slow and often becomes the limiting link in the charging and discharging process of the battery.

[0003] Taking a lithium-ion battery as an example, in the prior art, the solid-phase diffusion coefficient of the electrode material of the lithium-ion battery is measured by a potential relaxation method (PRT), but the efficiency of obtaining the solid-phase diffusion coefficient by this method is low. SUMMARY

[0004] The purpose of the embodiments of the present application is to provide a method and device for determining the solid-phase diffusion coefficient of electrode materials, an equipment and a storage medium, so as to improve the efficiency of obtaining the solid-phase diffusion coefficient of the electrode material in the battery.

[0005] In a first aspect, the embodiments of the present application provide a method for determining the solid-phase diffusion coefficient of electrode materials, comprising: obtaining pulse relaxation data of a battery; wherein the pulse relaxation data is the potential of the positive electrode and / or the negative electrode of the battery within a preset time period collected after a pulse current is applied to the battery under a target state of charge, and the preset time period is less than the time required for the battery to reach an equilibrium potential; fitting the pulse relaxation data by using a preset approximation function to obtain fitting data and an equilibrium potential; and determining the solid-phase diffusion coefficient of the electrode material of the battery according to the fitting data and the equilibrium potential.

[0006] The embodiments of the present application can obtain the fitting data when the battery reaches the potential balance by fitting the pulse relaxation data within a shorter time period by using the preset approximation function, and then the solid-phase diffusion coefficient of the electrode material can be obtained according to the fitting data and the equilibrium potential. Therefore, the time for the battery to stand still is shortened, and the efficiency of obtaining the solid-phase diffusion coefficient is improved.

[0007] In any embodiment, fitting the pulse relaxation data by using the preset approximation function comprises: fitting the pulse relaxation data by using the formula is the potential of the battery corresponding to each time point t in the relaxation process; a, b, c and d are unknown numbers; and t is each time point in the relaxation process.

[0008] ​The embodiments of this application utilize the above formula to fit pulse relaxation data, which can quickly obtain fitting data and equilibrium potential without having the battery stand still for a long time, thus improving the efficiency of obtaining the solid-phase diffusion coefficient of lithium batteries.

[0009] In any embodiment, determining the solid-phase diffusion coefficient of the battery electrode material based on the fitted data and the equilibrium potential includes: transforming the fitted data according to the equilibrium potential to obtain a processed fitted curve with respect to time; segmenting the processed fitted curve according to a preset window width and step size to obtain multiple curve segments; determining the slope and fitting accuracy corresponding to each curve segment, and determining the slope corresponding to the maximum fitting accuracy as the target slope; and determining the solid-phase diffusion coefficient based on the target slope.

[0010] This application embodiment segments the fitted data and uses the slope corresponding to the maximum fitting accuracy as the target slope. The solid-phase diffusion coefficient is determined based on the target slope. Since the fitted data eliminates the noise of the acquired battery pulse relaxation data, the accuracy of obtaining the solid-phase diffusion coefficient is improved.

[0011] In any embodiment, the fitted data is transformed based on the equilibrium potential to obtain a processed fitted curve with respect to time, including: according to the formula The potential at each time point t in the fitted data is transformed to obtain a time-processed fitted curve; where v' is the transformed value of the potential. This is the equilibrium potential; R represents the potential at each time point t during the relaxation process of the battery; R is the gas constant, with a default value of 8.31 J·mol⁻¹. -1 ·K -1 T is temperature; F is Faraday constant, with a default value of 96500 C / mol.

[0012] In this embodiment, the fitted data is transformed using the above formula to obtain a processed fitted curve, which provides a basis for subsequent calculation of the solid diffusion coefficient.

[0013] In any embodiment, determining the slope and fitting accuracy corresponding to each curve segment includes: fitting each curve segment according to the formula y = kx + b to obtain the slope and fitting accuracy corresponding to each curve segment; where y is the ordinate value of the fitted curve after processing; k is the slope; x is time; and b is the intercept.

[0014] This application embodiment obtains a stable and accurate solid-phase diffusion coefficient by fitting each curve segment and using the slope of the curve segment with the maximum fitting accuracy as the target slope.

[0015] In any embodiment, the electrode material comprises lithium ions, and the solid-phase diffusion coefficient is determined according to the target slope, including:

[0016] According to the formula Determine the solid-phase diffusion coefficient; where k is the target slope; d is the diameter of the active material particles; D Li is the solid-phase diffusion coefficient of lithium ions in the electrode.

[0017] In this embodiment of the application, after obtaining the target slope, the accurate solid-phase diffusion coefficient can be obtained according to the above formula.

[0018] In any embodiment, obtaining the battery's pulse relaxation data includes: sequentially charging or discharging the battery with a pulse current of a preset rate and a preset pulse time until the cutoff voltage is reached, thereby obtaining the battery's pulse relaxation data within the full battery state of charge range; wherein, each battery state of charge within the full battery state of charge range is referred to as the target battery state of charge.

[0019] This application embodiment obtains pulse relaxation data of the full battery state of charge range, and processes and analyzes the obtained pulse relaxation data to efficiently obtain the solid-phase diffusion coefficient of the battery in the full battery state of charge range.

[0020] Secondly, embodiments of this application provide a device for determining the solid-phase diffusion coefficient of an electrode material, comprising: a data acquisition module for acquiring pulse relaxation data of a battery; wherein the pulse relaxation data is the potential of the positive and / or negative electrodes of the battery within a preset time period after applying a pulse current to the battery in a state of charge of the target battery, and the preset time period is less than the time required for the battery to reach the equilibrium potential; a fitting module for fitting the pulse relaxation data using a preset approximation function to obtain fitted data and an equilibrium potential; and a determination module for determining the solid-phase diffusion coefficient of the electrode material of the battery based on the fitted data and the equilibrium potential.

[0021] Thirdly, embodiments of this application provide an electronic device, including: a processor, a memory, and a bus, wherein the processor and the memory communicate with each other via the bus; the memory stores program instructions that can be executed by the processor, and the processor can execute the method of the first aspect by calling the program instructions.

[0022] Fourthly, embodiments of this application provide a non-transitory computer-readable storage medium, comprising: the non-transitory computer-readable storage medium storing computer instructions, the computer instructions causing a computer to perform the method of the first aspect.

[0023] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a process for determining the solid-phase diffusion coefficient of a lithium battery, provided in an embodiment of this application.

[0026] Figure 2 Curves showing the solid-phase diffusion coefficient and equilibrium potential of the graphite anode provided in the embodiments of this application as a function of lithium insertion depth;

[0027] Figure 3 The curves show the solid-phase diffusion coefficient and equilibrium potential of the NCM cathode as a function of lithium insertion depth.

[0028] Figure 4(a) is a schematic diagram comparing the 1s DCR test results and simulation results at 0℃ provided in the embodiments of this application;

[0029] Figure 4(b) is a schematic diagram comparing the 1s DCR test results and simulation results at 10℃ provided in the embodiments of this application;

[0030] Figure 4(c) is a schematic diagram comparing the 1s DCR test results and simulation results at 25℃ provided in the embodiments of this application;

[0031] Figure 4(d) is a schematic diagram comparing the DCR test results and simulation results at 0℃ for 30s provided in the embodiments of this application;

[0032] Figure 4(e) is a schematic diagram comparing the DCR test results and simulation results at 10℃ for 30s provided in the embodiments of this application;

[0033] Figure 4(f) is a schematic diagram comparing the DCR test results and simulation results at 25°C for 30s provided in the embodiments of this application;

[0034] Figure 5 This is a schematic diagram of the structure of the lithium battery solid-phase diffusion coefficient determination device provided in the embodiments of this application;

[0035] Figure 6This is a schematic diagram of the physical structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0036] The following describes the relevant concepts involved in the embodiments of this application:

[0037] The intercalation / deintercalation reaction of metal ions involves a slow solid-state diffusion process, often considered the controlling step. Diffusion refers to the transport of matter from a high concentration to a low concentration, causing the concentration to homogenize. The diffusion coefficient is the rate of mass transfer of particles under a unit concentration gradient. The diffusion rate often determines the reaction rate; a larger diffusion coefficient results in better high-current discharge capability of the electrode, higher power density of the material, and better high-rate performance. Solid-state diffusion refers to diffusion within a solid primarily caused by the Brownian motion of atoms or ions through defects.

[0038] PRT: The study of the relationship between electrode potential and time under conditions where there is no exchange of matter and energy between the battery and the outside world. It is generally measured when the battery is charged (or discharged) at a constant current until a certain capacity is reached.

[0039] Pulse relaxation data: When a pulse current is applied to a battery for charging or discharging, and the pulse current is cut off when a certain potential is reached, the battery's electrode potential will undergo a relaxation process. The potential of the battery collected during this relaxation process is called pulse relaxation data.

[0040] Taking lithium batteries as an example, PRT calculates the solid-phase diffusion coefficient by processing the voltage-time curve during relaxation. The calculation formula is shown in formula (1):

[0041]

[0042] in, To balance the electrode potential, Let R be the initial potential, and R be the gas constant (8.31 J·mol⁻¹). -1 ·K -1 T is temperature, F is Faraday constant (default value is 6500°C / mol), d is the diameter of the active material particles, and D is the diameter of the active material particles. Li Let be the diffusion coefficient of Li in the electrode, and t be the time when the potential reaches equilibrium.

[0043] The inventors discovered that, since the potential relaxation process is often a very slow process, it usually takes a long time to reach potential equilibrium under a single pulse current. Therefore, the efficiency of obtaining the solid-phase diffusion coefficient of the positive and / or negative electrodes of the battery using the potential relaxation method is low.

[0044] To address this technical problem, this application provides a method for determining the solid-phase diffusion coefficient of an electrode material. This method acquires pulse relaxation data of a battery within a preset time period and fits the acquired pulse relaxation data using a preset approximation function to obtain fitted data after the battery reaches potential equilibrium. The solid-phase diffusion coefficient of the battery's electrode material is then calculated. Since the preset time period corresponding to the pulse relaxation data used in this method is shorter than the settling time required by existing potential relaxation methods, the solid-phase diffusion coefficient can be obtained quickly, improving the efficiency of obtaining the solid-phase diffusion coefficient.

[0045] It should be noted that the method for determining the solid-phase diffusion coefficient of the electrode material provided in this application embodiment can be applied to batteries where the electrode material contains lithium ions, batteries where the electrode material contains sodium ions, and batteries containing other metal ions. This application embodiment does not specifically limit this application. For ease of description, the following embodiments will use lithium batteries as an example for detailed description.

[0046] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0047] Figure 1 This is a schematic diagram illustrating the process for determining the solid-phase diffusion coefficient of a lithium battery, as provided in an embodiment of this application. Figure 1 As shown, the entity executing this method can be a terminal, and the method includes:

[0048] Step 101: Obtain pulse relaxation data of lithium battery; wherein, pulse relaxation data is the potential of the positive and / or negative electrode of lithium battery within a preset time period after applying pulse current to lithium battery in the state of charge of target battery, and the preset time period is less than the time required for lithium battery to reach equilibrium potential.

[0049] The materials constituting a lithium battery can be varied. For example, the positive electrode can be 811NCM, and the negative electrode can be graphite. Of course, the positive and negative electrodes of a lithium battery can also be other materials, and this application does not specifically limit this. The pulse relaxation data can be the potential of the lithium battery during the relaxation process collected by the terminal, or it can be collected by other devices and sent to the terminal.

[0050] It should be noted that the embodiments of this application are applicable to the determination of the solid-phase diffusion coefficient of the positive electrode of a lithium battery, as well as the determination of the solid-phase diffusion coefficient of the negative electrode of a lithium battery, and also applicable to the determination of the solid-phase diffusion coefficients of both the positive and negative electrodes of a lithium battery simultaneously. When it is necessary to obtain the solid-phase diffusion coefficients of both the positive and negative electrodes of a lithium battery simultaneously, the lithium battery must meet the requirements for pulse relaxation data acquisition of both the positive and negative electrodes. For example, it can be a coin cell lithium battery (with the positive and negative electrodes respectively for lithium), or a stacked three-electrode battery with a lithium reference electrode, etc.

[0051] The pulse current rate applied to the lithium battery can be determined based on the current state of charge (SOC) of the lithium battery. For example, when the lithium battery is at a high SOC (e.g., above 70%), the pulse current rate can be set to be larger, such as between 1C and 2C; when the lithium battery is at a low SOC (e.g., below 20%), the pulse current rate can be set to be smaller, such as less than 1C.

[0052] The size of the preset time period can be determined based on the sampling duration of the device collecting pulse relaxation data. This is because a certain number of pulse relaxation data points are needed to ensure the accuracy of fitting the pulse relaxation data. For example, if at least 300 pulse relaxation data points are required, and the device's sampling duration is one data point per second, then the preset time period must be at least 300 seconds. Generally, a preset time period of 5 minutes can be set. Therefore, it can be seen that the embodiment of this application only requires the lithium battery to be left to stand for about 5 minutes, which is significantly shorter than the at least 2 hours required in the prior art.

[0053] Step 102: Fit the pulse relaxation data using a preset approximation function to obtain the fitted data and equilibrium potential.

[0054] After obtaining the pulse relaxation data, the pulse relaxation data is fitted using a preset approximation function to obtain the fitted data. The fitted data is data about time and potential. Therefore, the potential of the lithium battery when it reaches the equilibrium state can be obtained through the fitted data, i.e., the equilibrium potential.

[0055] Step 103: Determine the solid-phase diffusion coefficient of the lithium battery based on the fitted data and equilibrium potential.

[0056] In this process, after obtaining the fitted data and equilibrium potential, the fitted data is processed based on the equilibrium potential to determine the solid-phase diffusion coefficient of the lithium battery.

[0057] This application embodiment uses a preset approximation function to fit pulse relaxation data over a short time period, thereby obtaining fitted data when the battery reaches potential equilibrium. The solid-phase diffusion coefficient can then be obtained based on the fitted data and the equilibrium potential. Therefore, the resting time of the lithium battery is shortened, and the efficiency of obtaining the solid-phase diffusion coefficient is improved.

[0058] Based on the above embodiments, the pulse relaxation data is fitted using a preset approximation function, including:

[0059] The pulse relaxation data are fitted using formula (2), which is shown below:

[0060]

[0061] in, Let be the potential at each time point t during the relaxation process of the lithium battery; a, b, c, and d are unknowns; t is each time point during the relaxation process.

[0062] In the specific implementation process, the pulse relaxation data are substituted into formula (2). In order to improve the fitting accuracy of the pulse relaxation data, four unknowns are set in formula (2) in this embodiment, namely a, b, c, and d. The specific values ​​of a, b, c, and d are calculated, so that the potential from 0 to ∞ at time t can be obtained, that is, the fitting data. Theoretically, when t is infinite, The coefficient 'a' will infinitely approach the given value. To obtain the solid-state diffusion coefficient across the entire SOC range more quickly, 'a' can be limited. Taking pulsed discharge as an example, for the positive electrode, the value of 'a' in the later SOC stage should be less than the value of 'a' in the earlier SOC stage. For the negative electrode, the value of 'a' in the later SOC stage should be greater than the value of 'a' in the earlier SOC stage.

[0063] The embodiments of this application utilize the above formula to fit pulse relaxation data, which can quickly obtain fitting data and equilibrium potential without having the lithium battery stand still for a long time, thus improving the efficiency of obtaining the solid-phase diffusion coefficient of the lithium battery.

[0064] Based on the above embodiments, the solid-phase diffusion coefficient of the lithium battery is determined according to the fitted data and equilibrium potential, including:

[0065] The fitted data is transformed based on the equilibrium potential to obtain a time-processed fitted curve.

[0066] The processed fitted curve is segmented according to the preset window width and step size to obtain multiple curve segments;

[0067] Determine the slope and fitting accuracy for each curve segment, and set the slope corresponding to the maximum fitting accuracy as the target slope.

[0068] The solid-phase diffusion coefficient is determined based on the target slope.

[0069] In the specific implementation process, the fitted data consists of time-potential point data. The potential in the fitted data is transformed according to the equilibrium potential to obtain the transformed potential value for each time point. The transformed data points are plotted and connected to obtain the processed fitted curve. It can be understood that in the processed fitted curve, the horizontal axis represents time, and the vertical axis represents the transformed potential value.

[0070] After obtaining the processed fitted curve, the curve is segmented using a preset window width and step size to obtain multiple curve segments. For example, the window width can be 1 / 6 of the total number of data points in the fitted data, and the step size can be 1 / 8 of the total number of data points. It is understood that the window width and step size can be adjusted according to the actual situation, and this application embodiment does not specifically limit them.

[0071] Each curve segment is fitted separately; specifically, a linear fit can be performed on each curve segment to obtain the slope and fitting accuracy for each segment. It is understandable that existing fitting tools can be used for this purpose.

[0072] The slope corresponding to the maximum fitting accuracy is taken as the target slope. After obtaining the target slope, the solid-phase diffusion coefficient can be calculated.

[0073] In this embodiment, the fitted data is segmented and the slope corresponding to the maximum fitting accuracy is taken as the target slope. The solid-phase diffusion coefficient is determined based on the target slope. Since the data points of the fitted data are more dense and smoother than the original test data, the noise of the acquired lithium battery pulse relaxation data is eliminated, thus improving the accuracy of obtaining the solid-phase diffusion coefficient.

[0074] Based on the above embodiments, the fitted data is transformed according to the equilibrium potential to obtain a processed fitted curve with respect to time, including:

[0075] The potential at each time t in the fitted data is transformed according to formula (3) to obtain the value of the potential after processing; formula (3) is shown below:

[0076]

[0077] Where v' is the value after the potential is transformed. This is the equilibrium potential; R represents the potential at each time point t during the relaxation process of the lithium battery; R is the gas constant, with a default value of 8.31 J·mol⁻¹. -1 ·K -1T represents temperature; F represents Faraday constant, with a default value of 6500°C / mol.

[0078] The obtained potential values ​​at each time point are plotted and connected to obtain a time-processed fitting curve.

[0079] In this embodiment, the fitted data is transformed using the above formula to obtain a processed fitted curve, which provides a basis for subsequent calculation of the solid diffusion coefficient.

[0080] Based on the above embodiments, the slope and fitting accuracy corresponding to each curve segment are determined, including: fitting each curve segment according to formula (4) to obtain the slope and fitting accuracy corresponding to each curve segment:

[0081] y = kx + b (4)

[0082] Where y is the ordinate of the fitted curve after processing; k is the slope; x is time; and b is the intercept.

[0083] In the specific implementation process, the time value corresponding to each point in each curve segment is substituted into x in formula (4), and the result is obtained. Substitute the corresponding values ​​into y in formula (4) to calculate k and b. It is understandable that the tool for fitting each curve segment can also be an existing fitting tool, and the fitting accuracy can be calculated using the existing fitting tool.

[0084] This application embodiment obtains a stable and accurate solid-phase diffusion coefficient by fitting each curve segment and using the slope of the curve segment with the maximum fitting accuracy as the target slope.

[0085] Based on the above embodiments, the solid-phase diffusion coefficient is determined according to the target slope, including:

[0086] The solid-phase diffusion coefficient is determined according to formula (5):

[0087]

[0088] Where k is the target slope; d is the diameter of the active substance particles; D Li Let be the solid-phase diffusion coefficient of lithium ions in the electrode. It can be understood that if the pulse relaxation data is for the positive electrode of a lithium battery, d is the diameter of the positive electrode material particles, and D... Li d is the solid-phase diffusion coefficient of the lithium-ion cathode; if the pulse relaxation data is for the lithium-ion anode, d is the diameter of the anode material particles, and D... Li is the solid-phase diffusion coefficient of the lithium-ion anode.

[0089] In this embodiment of the application, after obtaining the target slope, the accurate solid-phase diffusion coefficient can be obtained according to the above formula.

[0090] Based on the above embodiments, obtaining pulse relaxation data of lithium batteries includes: sequentially charging or discharging lithium batteries with pulse current of preset rate and preset pulse time until the cutoff voltage is reached, thereby obtaining pulse relaxation data of lithium batteries in the full battery state of charge range; wherein, each battery state of charge in the full battery state of charge range is called the target battery state of charge.

[0091] In the specific implementation process, in order to obtain the solid-state diffusion coefficient of the positive and / or negative electrodes of the lithium battery across the entire SOC range, the lithium battery can be sequentially charged or discharged according to a preset rate and preset pulse duration. For example, the lithium battery can be discharged from 100% SOC with a small-rate pulse (0-2C), or charged from 0% SOC with a small-rate pulse (0-2C). Taking discharge as an example, the initial SOC of the lithium battery is 100%, assuming the preset pulse current applied to the lithium battery is 2C and the preset pulse duration is 10 seconds, after sequentially pulse discharging the lithium battery at 100% SOC, it is allowed to rest for 5 minutes, and the pulse relaxation data during the rest period is obtained. After one discharge, the SOC of the lithium battery will decrease, for example, to 98%. After the previous resting period, a pulse current is applied to the lithium battery again to discharge it. After the discharge, it is rested for another 5 minutes, and so on, discharging sequentially in the above manner until the cutoff voltage of the lithium battery is reached. This allows us to obtain pulse relaxation data of the lithium battery across the entire SOC range. After obtaining the pulse relaxation data across the entire SOC range, the solid-phase diffusion coefficient is determined for each discharge using the method described in the above embodiment, thereby obtaining the solid-phase diffusion coefficient of the lithium battery across the entire SOC range.

[0092] It should be noted that, to prevent the lithium battery from reaching its cutoff voltage prematurely, when the lithium battery's SOC falls below a certain threshold, such as below 20%, the pulse current rate can be reduced. The SOC of the lithium battery obtained after each discharge is the target SOC.

[0093] In addition, in practical applications, once the pulse relaxation data obtained from each discharge is acquired, the solid-phase diffusion coefficient can be calculated from the pulse relaxation data, without having to acquire the pulse relaxation data for the entire SOC range before calculating the solid-phase diffusion coefficient.

[0094] It is understandable that when charging a lithium battery, the initial SOC of the lithium battery is 0, and then pulse currents are applied to the lithium battery sequentially for charging.

[0095] In another embodiment, the State of Charge (SOC) can be fixed. Specifically, pulse relaxation data can be collected when the SOC value of the lithium battery reaches 2%, 4%, 6%, 8%, 10%, ..., 100%. The lithium battery can be charged or discharged according to a preset pulse rate, where the pulse duration is not fixed. For example, with charging, the initial SOC of the lithium battery is 0. The battery is charged using a 2C pulse rate. When the SOC reaches 2%, charging is stopped, and the battery is left to rest for 5 minutes. Pulse relaxation data is collected during this rest period. This process is repeated until the SOC reaches 100%. It is understood that 2%, 4%, 6%, 8%, 10%, ..., 100% are all target SOC values.

[0096] This application embodiment obtains pulse relaxation data of the full battery state of charge range, processes and analyzes the obtained pulse relaxation data, and thus can efficiently obtain the solid-phase diffusion coefficient of the lithium battery in the full battery state of charge range.

[0097] In another embodiment, an experiment was conducted using a lithium battery with 811NCM as the positive electrode and graphite as the negative electrode as an example. Figure 2 The curves showing the solid-phase diffusion coefficient and equilibrium potential of the graphite anode provided in the embodiments of this application as a function of lithium insertion depth are shown. Figure 3 The curves show the solid-phase diffusion coefficient and equilibrium potential of the NCM cathode as a function of lithium insertion depth. Figure 2 and Figure 3 The horizontal axis represents the lithium insertion depth, the vertical axis on the left represents the potential, and the vertical axis on the right represents the solid-phase diffusion coefficient. The solid line represents the curve of potential as a function of lithium insertion depth, and the dashed line represents the curve of solid-phase diffusion coefficient as a function of lithium insertion depth.

[0098] Figure 4(a) is a schematic diagram comparing the test results and simulation results of 1s DCR at 0℃ provided in the embodiment of this application; Figure 4(b) is a schematic diagram comparing the test results and simulation results of 1s DCR at 10℃ provided in the embodiment of this application; Figure 4(c) is a schematic diagram comparing the test results and simulation results of 1s DCR at 25℃ provided in the embodiment of this application; Figure 4(d) is a schematic diagram comparing the test results and simulation results of 30s DCR at 0℃ provided in the embodiment of this application; Figure 4(e) is a schematic diagram comparing the test results and simulation results of 30s DCR at 10℃ provided in the embodiment of this application; and Figure 4(f) is a schematic diagram comparing the test results and simulation results of 30s DCR at 25℃ provided in the embodiment of this application. Figures 4(a)-4(f) In the graph, the horizontal axis represents the State of Charge (SOC) of the lithium battery, and the vertical axis represents the resistance of the lithium battery. Square dots represent test results showing the resistance changing with SOC, while dashed lines represent simulation results showing the resistance changing with SOC. Figures 4(a)-4(f)It can be seen that, after ensuring the accuracy of 1sDCR (i.e., the accuracy of the process dominated by chemical reaction impedance), 30sDCR is also accurate. This experiment shows that the trend of solid-phase diffusion coefficient with SOC obtained by the solid-phase diffusion coefficient determination method provided in the embodiments of this application is accurate.

[0099] Figure 5 This is a schematic diagram of the device for determining the solid-phase diffusion coefficient of electrode materials provided in an embodiment of this application. This device can be a module, program segment, or code on an electronic device. It should be understood that this device is similar to the one described above. Figure 1 The method implementation corresponds to this and can be executed. Figure 1 The various steps involved in the method embodiment, and the specific functions of the device, can be found in the description above. To avoid repetition, detailed descriptions are appropriately omitted here. The device includes: a data acquisition module 501, a fitting module 502, and a determination module 503, wherein:

[0100] The data acquisition module 501 is used to acquire the pulse relaxation data of the battery; wherein, the pulse relaxation data is the potential of the positive and / or negative electrodes of the battery within a preset time period after applying a pulse current to the battery in the state of charge of the target battery, and the preset time period is less than the time required for the battery to reach the equilibrium potential; the fitting module 502 is used to fit the pulse relaxation data using a preset approximation function to obtain the fitted data and the equilibrium potential; the determination module 503 is used to determine the solid-phase diffusion coefficient of the electrode material of the battery based on the fitted data and the equilibrium potential.

[0101] Based on the above embodiments, the fitting module 502 is specifically used for:

[0102] Using formula Fit the pulse relaxation data;

[0103] in, Let be the potential at each time point t during the relaxation process of the battery; a, b, c, and d are unknowns; t is each time point during the relaxation process.

[0104] Based on the above embodiments, the determination module 503 is specifically used for:

[0105] The fitted data is transformed based on the equilibrium potential to obtain a time-processed fitted curve.

[0106] The processed fitted curve is segmented according to the preset window width and step size to obtain multiple curve segments;

[0107] Determine the slope and fitting accuracy for each curve segment, and set the slope corresponding to the maximum fitting accuracy as the target slope.

[0108] The solid-phase diffusion coefficient is determined based on the target slope.

[0109] Based on the above embodiments, the determination module 503 is specifically used for:

[0110] According to the formula The potential at each time point t in the fitted data is transformed to obtain the time-processed fitted curve.

[0111] Where v' is the value after the potential is transformed. This is the equilibrium potential; R represents the potential at each time point t during the battery's relaxation process; R is the gas constant, with a default value of 8.31 J·mol⁻¹. -1 ·K -1 T is temperature; F is Faraday constant, with a default value of 96500 C / mol.

[0112] Based on the above embodiments, the determination module 503 is specifically used for:

[0113] Each curve segment is fitted according to the formula y=kx+b to obtain the slope and fitting accuracy of each curve segment.

[0114] Where y is the ordinate of the fitted curve after processing; k is the slope; x is time; and b is the intercept.

[0115] Based on the above embodiments, the electrode material contains lithium ions, and the determining module 503 is specifically used for:

[0116] According to the formula Determine the solid-phase diffusion coefficient;

[0117] Where k is the target slope; d is the diameter of the active substance particles; D Li is the solid-phase diffusion coefficient of lithium ions in the electrode.

[0118] Based on the above embodiments, the data acquisition module 501 is specifically used for:

[0119] The battery is sequentially charged or discharged using a pulse current with a preset rate and preset pulse time until the cutoff voltage is reached, thereby obtaining pulse relaxation data of the battery within the full battery state of charge range; wherein, each battery state of charge in the full battery state of charge range is called the target battery state of charge.

[0120] Figure 6 This is a schematic diagram of the physical structure of the electronic device provided in the embodiments of this application, such as... Figure 6 As shown, the electronic device includes: a processor 601, a memory 602, and a bus 603; wherein,

[0121] The processor 601 and the memory 602 communicate with each other via the bus 603;

[0122] The processor 601 is used to call program instructions in the memory 602 to execute the methods provided in the above-described method embodiments, such as: acquiring pulse relaxation data of the battery; wherein the pulse relaxation data is the potential of the positive and / or negative electrodes of the battery within a preset time period after applying a pulse current to the battery in the state of charge of the target battery, and the preset time period is less than the time required for the battery to reach the equilibrium potential; fitting the pulse relaxation data using a preset approximation function to obtain fitted data and equilibrium potential; and determining the solid-phase diffusion coefficient of the electrode material of the battery based on the fitted data and equilibrium potential.

[0123] Processor 601 can be an integrated circuit chip with signal processing capabilities. The processor 601 can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor can be a microprocessor or any conventional processor.

[0124] The memory 602 may include, but is not limited to, random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.

[0125] This embodiment discloses a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, and when the program instructions are executed by the computer, the computer can perform the methods provided in the above-described method embodiments, such as: acquiring pulse relaxation data of a battery; wherein the pulse relaxation data is the potential of the positive and / or negative electrodes of the battery within a preset time period after applying a pulse current to the battery in a state of charge of the target battery, and the preset time period is less than the time required for the battery to reach the equilibrium potential; fitting the pulse relaxation data using a preset approximation function to obtain fitted data and an equilibrium potential; and determining the solid-phase diffusion coefficient of the electrode material of the battery based on the fitted data and the equilibrium potential.

[0126] This embodiment provides a non-transitory computer-readable storage medium that stores computer instructions. The computer instructions cause the computer to execute the methods provided in the above-described method embodiments, such as: acquiring pulse relaxation data of a battery; wherein the pulse relaxation data is the potential of the positive and / or negative electrodes of the battery within a preset time period after applying a pulse current to the battery in a state of charge, and the preset time period is less than the time required for the battery to reach the equilibrium potential; fitting the pulse relaxation data using a preset approximation function to obtain fitted data and the equilibrium potential; and determining the solid-phase diffusion coefficient of the electrode material of the battery based on the fitted data and the equilibrium potential.

[0127] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and there may be other division methods in actual implementation. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the coupling or direct coupling or communication connection shown or discussed may be through some communication interface; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0128] Furthermore, the units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0129] Furthermore, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0130] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0131] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for determining a solid phase diffusion coefficient of an electrode material, characterized by, The method comprises: acquiring pulse relaxation data of a battery; wherein the pulse relaxation data is the potential of the positive electrode and / or the negative electrode of the battery within a preset time period after a pulse current is applied to the battery under a target state of charge, and the preset time period is less than the time required for the battery to reach an equilibrium potential; fitting the pulse relaxation data using a preset approximation function to obtain fitting data and an equilibrium potential; determining a solid-phase diffusion coefficient of an electrode material of the battery according to the fitting data and the equilibrium potential; The method of determining the solid-phase diffusion coefficient of the electrode material of the battery according to the fitting data and the equilibrium potential comprises: transforming the fitting data according to the equilibrium potential to obtain a processed fitting curve with respect to time; segmenting the processed fitting curve according to a preset window width and a step length to obtain a plurality of curve segments; determining the slope and fitting accuracy of each curve segment, and determining the slope corresponding to the maximum fitting accuracy as a target slope; determining the solid-phase diffusion coefficient according to the target slope.

2. The method of claim 1, wherein, The method of fitting the pulse relaxation data using a preset approximation function comprises: Using the formula fitting the pulse relaxation data; wherein, is the potential corresponding to each time point t for the relaxation process of the battery; , , , is an unknown; is each time point in the relaxation process.

3. The method of claim 1, wherein, The method of transforming the fitting data according to the equilibrium potential to obtain a processed fitting curve with respect to time comprises: According to the formula transforming the potential corresponding to each time instant in the fitted data, obtaining a processed fitted curve as a function of time; wherein, is a value after transformation of the potential, is the equilibrium potential; is the potential of the battery at each time point t during the relaxation process; is the gas constant, by default 8.314 J / mol / K; ; is the temperature; is the Faraday constant, by default 96500 C / mol.

4. The method of claim 1, wherein, The method of determining the slope and fitting accuracy of each curve segment comprises: According to the formula Fitting each curve segment to obtain the slope and fitting accuracy corresponding to each curve segment; wherein, is the ordinate value of the fitted curve after the treatment; is the slope; is time; is the intercept.

5. The method of claim 1, wherein, The electrode material contains lithium ions, and the method of determining the solid-phase diffusion coefficient according to the target slope comprises: According to the formula determining the solid phase diffusion coefficient; wherein, is the target slope; is the diameter of the active material particles; is the solid phase diffusion coefficient of lithium ions in the electrode.

6. The method of claim 1, wherein, The method of acquiring the pulse relaxation data of the battery comprises: charging or discharging the battery in sequence using a pulse current with a preset rate and a preset pulse time until a cutoff voltage is reached to obtain the pulse relaxation data of the battery within a full state of charge interval; wherein each state of charge in the full state of charge interval is referred to as the target state of charge.

7. An electrode material solid phase diffusion coefficient determination apparatus characterized by comprising: The method comprises: a data acquisition module configured to acquire pulse relaxation data of a battery; wherein the pulse relaxation data is the potential of the positive electrode and / or the negative electrode of the battery within a preset time period after a pulse current is applied to the battery under a target state of charge, and the preset time period is less than the time required for the battery to reach an equilibrium potential; a fitting module configured to fit the pulse relaxation data using a preset approximation function to obtain fitting data and an equilibrium potential; a determination module configured to determine a solid-phase diffusion coefficient of an electrode material of the battery according to the fitting data and the equilibrium potential; The determination module is specifically configured to: transform the fitting data according to the equilibrium potential to obtain a processed fitting curve with respect to time; segment the processed fitting curve according to a preset window width and a step length to obtain a plurality of curve segments; determine the slope and fitting accuracy of each curve segment, and determine the slope corresponding to the maximum fitting accuracy as a target slope; determine the solid-phase diffusion coefficient according to the target slope.

8. An electronic device, comprising: The method comprises: a processor, a memory and a bus, wherein the processor and the memory communicate with each other through the bus; The memory stores program instructions executable by the processor, the processor invoking the program instructions being capable of executing the method of any one of claims 1-6.

9. A non-transitory computer-readable storage medium, comprising: The non-transitory computer readable storage medium stores computer instructions, the computer instructions, when executed by a computer, causing the computer to perform the method of any one of claims 1-6.

Images