Lithium deposition evaluation method and device for lithium-ion batteries

Abstract

The present application relates to the field of lithium-ion batteries and provides a method and device for evaluating lithium deposition in lithium-ion batteries. The method comprises: obtaining a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated based on the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated; subtracting the surface pressure corresponding to each SOC value of the pressure-SOC curve to be compared from the surface pressure corresponding to the same SOC value of the standard pressure-SOC curve, and obtaining a first pressure difference value corresponding to each SOC value to obtain a first pressure difference value-SOC curve; if the first pressure difference value-SOC curve is below the threshold curve in the standard coordinate system, it is determined that the lithium-ion battery to be evaluated has not deposited lithium. The lithium-ion battery lithium deposition evaluation method provided in the embodiment of the present application can obtain a higher accuracy in lithium deposition evaluation, thereby improving the accuracy of lithium deposition evaluation.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a method and device for evaluating lithium deposition in lithium-ion batteries. Background Art

[0002] Lithium-ion batteries are widely used in various electronic products due to their high energy density, operating voltage, and cycle life, and are considered an ideal power source for electric vehicles. During the charging process, lithium ions are released from the positive electrode and embedded in the negative electrode. When the positive electrode delithiation rate is too rapid (such as during fast charging), or when the negative electrode lithium insertion rate is reduced (such as at high state of charge (SOC) or low temperatures), lithium ions tend to precipitate on the negative electrode surface and form metallic lithium (lithium plating). Lithium plating exacerbates electrolyte side reactions, thereby reducing battery efficiency, lowering the temperature of thermal runaway, and increasing the risk of internal micro-short circuits, posing a significant threat to battery performance and safety. Therefore, lithium plating assessment has great application value.

[0003] Existing lithium plating assessment technologies primarily involve battery disassembly and real-time monitoring. Real-time monitoring, however, is favored by researchers because it can mitigate the risk of lithium plating by adjusting charging and discharging strategies without damaging the battery. However, existing real-time monitoring methods suffer from poor assessment accuracy, significantly impacting the accuracy of lithium plating assessments. Summary of the Invention

[0004] The embodiments of the present application provide a method and device for evaluating lithium deposition in lithium-ion batteries, which are used to solve the technical problem that existing real-time monitoring methods have poor evaluation accuracy, seriously affecting the accuracy of lithium deposition evaluation.

[0005] In a first aspect, an embodiment of the present application provides a method for evaluating lithium deposition in a lithium-ion battery, comprising:

[0006] Obtaining a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated according to the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process;

[0007] A first pressure difference is obtained by subtracting the surface pressure corresponding to each SOC value of the pressure-SOC curve to be compared from the surface pressure corresponding to the same SOC value of the standard pressure-SOC curve, and the first pressure difference is matched with each SOC value to obtain a first pressure difference-SOC curve; the standard pressure-SOC curve is a pressure-SOC curve of a fresh battery under the same operating conditions as the lithium-ion battery to be evaluated; the fresh battery is a lithium-ion battery that has not been subjected to any operating conditions after pre-charge and formation;

[0008] If the first pressure difference-SOC curve is below the threshold curve in a standard coordinate system, it is determined that the lithium-ion battery to be evaluated has not deposited lithium; the standard coordinate system is a coordinate system with the SOC value as the horizontal axis and the pressure value as the vertical axis.

[0009] In one embodiment, obtaining a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated based on the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process includes:

[0010] The surface pressure and the SOC value are matched one by one according to time to obtain a surface pressure-SOC curve of the lithium ion to be evaluated;

[0011] If the absolute value of the difference between the open-circuit voltage of the lithium-ion battery to be evaluated at the end of charging and the open-circuit voltage of the fresh battery at the end of charging is greater than a difference threshold, correcting the surface pressure-SOC curve, and using the corrected surface pressure-SOC curve as the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated;

[0012] If the absolute value of the difference between the open-circuit voltage of the lithium-ion battery to be evaluated at the end of charging and the open-circuit voltage of the fresh battery at the end of charging is less than or equal to the difference threshold, the surface pressure-SOC curve is used as the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated.

[0013] In one embodiment, the correcting the surface pressure-SOC curve and using the corrected surface pressure-SOC curve as the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated includes:

[0014] The surface pressure-SOC curve is shifted based on the SOC value corresponding to the open circuit voltage of the lithium-ion battery to be evaluated at the end of charging, to obtain the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated.

[0015] In one embodiment, after obtaining the first pressure difference-SOC curve, the method includes:

[0016] If, in the standard coordinate system, the first pressure difference-SOC curve is above the threshold curve, or the first pressure difference-SOC curve coincides with the threshold curve, a second pressure difference-SOC curve is obtained according to the surface pressure change difference of the lithium-ion battery to be evaluated during the charging process;

[0017] The threshold curve is updated, and the lithium plating condition of the lithium-ion battery to be evaluated is determined according to the positional relationship between the second pressure difference-SOC curve and the updated threshold curve, wherein each updated threshold curve is located below the previous threshold curve.

[0018] In one embodiment, obtaining a second pressure difference-SOC curve according to the surface pressure change difference of the lithium-ion battery to be evaluated during the charging process includes:

[0019] Select the surface pressure and SOC value corresponding to the Nth charging process, the NAth charging process, the Ath charging process, and the first charging process of the lithium-ion battery to be evaluated, where A is an integer greater than or equal to 1 and less than or equal to 500, and N is an integer greater than A;

[0020] Subtracting the surface pressure corresponding to each SOC value during the Nth charging cycle from the surface pressure corresponding to the same SOC value during the NAth charging cycle to obtain a first sub-pressure difference;

[0021] Subtract the surface pressure corresponding to each SOC value during the Ath week of charging from the surface pressure corresponding to the same SOC value during the first week of charging to obtain a second sub-pressure difference;

[0022] A second pressure difference obtained by subtracting the second sub-pressure difference corresponding to each SOC value from the first sub-pressure difference corresponding to the same SOC value is matched one-to-one with each SOC value to obtain a second pressure difference-SOC curve.

[0023] In one embodiment, determining the lithium plating condition of the lithium-ion battery to be evaluated based on the positional relationship between the second pressure difference-SOC curve and the updated threshold curve includes:

[0024] If, in the standard coordinate system, the second pressure difference-SOC curve is below the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has not undergone lithium deposition;

[0025] If, in the standard coordinate system, the second pressure difference-SOC curve is above the updated threshold curve, or the second pressure difference-SOC curve coincides with the updated threshold curve, then after reducing the value of A and recalculating the second pressure difference-SOC curve, the threshold curve is updated, and the step of determining the lithium deposition condition of the lithium-ion battery to be evaluated based on the positional relationship between the second pressure difference-SOC curve and the updated threshold curve is performed, until A is less than or equal to the interval threshold. If the second pressure difference-SOC curve is below the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has not deposited lithium; if the second pressure difference-SOC curve is above the updated threshold curve, or the second pressure difference-SOC curve coincides with the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has deposited lithium.

[0026] In one embodiment, after determining that the lithium-ion battery to be evaluated has lithium deposited, the method includes:

[0027] Charging the lithium-ion battery to be evaluated using a first current and a second current, respectively, obtaining a pressure difference corresponding to the same SOC value of the lithium-ion battery to be evaluated under the first current and the second current, and obtaining a third pressure difference-SOC curve; the first current is a current under low current, and the second current is a current less than the operating current;

[0028] The third pressure difference-SOC curve is compared with a standard third pressure difference-SOC curve to optimize the non-lithium precipitation charging current and SOC charging range of the lithium-ion battery to be evaluated. The standard third pressure difference-SOC curve is the third pressure difference-SOC curve of the fresh battery at two different currents.

[0029] In a second aspect, an embodiment of the present application provides a lithium-ion battery lithium deposition evaluation device, comprising:

[0030] a pressure-SOC curve generation module for comparison, configured to obtain a pressure-SOC curve for comparison during the charging process of the lithium-ion battery to be evaluated based on the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process;

[0031] a pressure difference-SOC curve generating module, configured to: obtain a first pressure difference by subtracting the surface pressure corresponding to each SOC value of the pressure-SOC curve to be compared from the surface pressure corresponding to the same SOC value of the standard pressure-SOC curve, and assigning a one-to-one correspondence between the first pressure difference and each SOC value to generate a first pressure difference-SOC curve; the standard pressure-SOC curve is a pressure-SOC curve of a fresh battery under the same operating conditions as the lithium-ion battery to be evaluated; the fresh battery is a lithium-ion battery that has not been subjected to any operating conditions after pre-charging and formation;

[0032] The first lithium deposition evaluation module is configured to determine that the lithium-ion battery to be evaluated has not deposited lithium if the first pressure difference-SOC curve is below a threshold curve in a standard coordinate system, wherein the standard coordinate system has the SOC value as the horizontal axis and the pressure value as the vertical axis.

[0033] In a third aspect, an embodiment of the present application provides an electronic device comprising a processor and a memory storing a computer program, wherein when the processor executes the program, the steps of the lithium ion battery lithium deposition evaluation method described in the first aspect are implemented.

[0034] In a fourth aspect, an embodiment of the present application provides a computer program product, comprising a computer program, which, when executed by a processor, implements the steps of the lithium-ion battery lithium deposition evaluation method described in the first aspect.

[0035] The lithium deposition evaluation method and device for lithium-ion batteries provided in the embodiments of the present application determine whether the lithium-ion battery to be evaluated is undergoing lithium deposition by comparing the positional relationship between the first pressure difference-SOC curve and the threshold curve. Since the first pressure difference is the change in the surface pressure of the lithium-ion battery to be evaluated and the surface pressure of a fresh battery corresponding to the same SOC value under the same operating current, the change in the pressure difference is more meaningful for reference, enabling the lithium deposition evaluation method of the present embodiment to obtain higher lithium deposition evaluation accuracy, thereby improving the accuracy of the lithium deposition evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the present application or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0037] Figure 1 This is one of the flow charts of the lithium ion battery lithium deposition evaluation method provided in the embodiment of the present application;

[0038] Figure 2 This is the second flow chart of the lithium ion battery lithium deposition evaluation method provided in the embodiment of the present application;

[0039] Figure 3 This is the third flow chart of the lithium ion battery lithium deposition evaluation method provided in the embodiment of the present application;

[0040] Figure 4 This is the fourth flow chart of the lithium ion battery lithium deposition evaluation method provided in the embodiment of the present application;

[0041] Figure 5Schematic diagram of the structure of the lithium ion battery lithium deposition evaluation device provided in an embodiment of the present application;

[0042] Figure 6 It is a structural diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions in this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0044] Figure 1 This is a flow chart of a lithium ion battery lithium deposition evaluation method provided in an embodiment of the present application. Figure 1 , the present application embodiment provides a lithium ion battery lithium deposition evaluation method, which may include:

[0045] 101. Obtain a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated based on the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process;

[0046] A constant displacement rigid fixture with a pressure acquisition device can be used to clamp the lithium-ion battery to be evaluated, perform cyclic charge and discharge tests on the battery, and collect and record relevant data.

[0047] The SOC value is the ratio of the measured capacity of the lithium-ion battery to be evaluated to the standard capacity (i.e., capacity / standard capacity). The standard capacity is the capacity of a fresh battery calibrated under a small current (such as 0.04C). A fresh battery is a lithium-ion battery that has not experienced any working conditions after pre-charge and formation.

[0048] 102. Subtract the surface pressure corresponding to each SOC value of the pressure-SOC curve to be compared from the surface pressure corresponding to the same SOC value of the standard pressure-SOC curve to obtain a first pressure difference, and associate it with each SOC value one by one to obtain a first pressure difference-SOC curve;

[0049] The standard pressure-SOC curve is a pressure-SOC curve of a fresh battery under the same operating conditions as the lithium-ion battery to be evaluated, and is obtained by normalizing the pressure-capacity curve of the fresh battery under the operating current by the standard capacity.

[0050] 103. If, in the standard coordinate system, the first pressure difference-SOC curve is below the threshold curve, it is determined that the lithium-ion battery to be evaluated has not deposited lithium.

[0051] The standard coordinate system is a coordinate system with the SOC value as the horizontal axis and the pressure value as the vertical axis.

[0052] The first pressure difference-SOC curve is located below the threshold curve, that is, at the same SOC value, the first pressure difference is always smaller than the threshold.

[0053] The threshold curve can be determined by the following method:

[0054] Obtain the pressure-SOC curve of a fresh battery at different charging rates, and calibrate the pressure-SOC curve with the open circuit voltage after charging to obtain its calibrated pressure-SOC curve. Calculate the difference between the calibrated pressure-SOC curve at different rates and the pressure-SOC curve of the fresh battery at the operating current at the same SOC value, and correspond them one-to-one with the SOC value to obtain different threshold curves.

[0055] The threshold curve depends on the battery system. For high-energy batteries, the threshold curve is determined by the difference between the calibrated pressure-SOC curve corresponding to the 3C current and the pressure-SOC curve of a fresh battery under the operating current at the same SOC value. For high-power batteries, the threshold curve is determined by the difference between the calibrated pressure-SOC curve corresponding to the 5C current and the pressure-SOC curve of a fresh battery under the operating current at the same SOC value, or by the difference between the calibrated pressure-SOC curve corresponding to the current at which a sudden change in pressure information occurs and the pressure-SOC curve of a fresh battery under the operating current at different charging rates (such as 0.04C, 0.1C, 0.5C, 1C, 1.5C, 2C, 3C, 4C, 5C).

[0056] The lithium deposition evaluation method for lithium-ion batteries provided in this embodiment determines whether the lithium-ion battery to be evaluated has deposited lithium by comparing the positional relationship between the first pressure difference-SOC curve and the threshold curve. Since the first pressure difference is the change in the surface pressure of the lithium-ion battery to be evaluated and the surface pressure of a fresh battery corresponding to the same SOC value under the same operating current, the change in the pressure difference is more meaningful for reference, so that the lithium deposition evaluation method of this embodiment can obtain higher lithium deposition evaluation accuracy, thereby improving the accuracy of lithium deposition evaluation.

[0057] Figure 2 This is a second flow chart of the lithium ion battery lithium deposition evaluation method provided in the embodiment of the present application. Figure 2 In one embodiment, obtaining a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated based on the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process may include:

[0058] 201. Corresponding the surface pressure and the SOC value according to time to obtain a surface pressure-SOC curve of the lithium ion to be evaluated;

[0059] 202. If the absolute value of the difference between the open circuit voltage of the lithium-ion battery to be evaluated at the end of charging and the open circuit voltage of the fresh battery at the end of charging is greater than the difference threshold, correcting the surface pressure-SOC curve, and using the corrected surface pressure-SOC curve as the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated;

[0060] The correction method can be as follows:

[0061] The SOC value corresponding to the open circuit voltage of the lithium-ion battery to be evaluated at the end of charging on the standard voltage-SOC curve is used as a benchmark, and the surface pressure-SOC curve is shifted to obtain the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated.

[0062] The difference threshold may be 0.1V.

[0063] 203. If the absolute value of the difference between the open circuit voltage of the lithium-ion battery to be evaluated at the end of charging and the open circuit voltage of the fresh battery at the end of charging is less than or equal to the difference threshold, the surface pressure-SOC curve is used as the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated.

[0064] This embodiment determines whether the surface pressure-SOC curve of the lithium-ion battery to be evaluated needs to be corrected based on a comparison of the open circuit voltages of the lithium-ion battery to be evaluated and a fresh battery at the end of charging. If the open circuit voltage of the lithium-ion battery to be evaluated at the end of charging deviates significantly from the open circuit voltage of the fresh battery at the end of charging, the surface pressure-SOC curve of the lithium-ion battery to be evaluated is corrected. If the deviation between the two is not significant, no correction is performed, thereby obtaining a more accurate pressure-SOC curve to be compared.

[0065] Figure 3 This is a flow chart of the third method for evaluating lithium deposition in lithium-ion batteries provided in the embodiment of the present application. Figure 3 In one embodiment, if the first pressure difference-SOC curve is above the threshold curve in the standard coordinate system, or the first pressure difference-SOC curve coincides with the threshold curve, the lithium deposition assessment method may include:

[0066] 301. Select the surface pressure and SOC value corresponding to the Nth charging process, the NAth charging process, the Ath charging process, and the first charging process of the lithium-ion battery to be evaluated;

[0067] Wherein, A is an integer greater than or equal to 1 and less than 500, N is an integer greater than A, and further, A can be an integer greater than or equal to 1 and less than or equal to 50.

[0068] 302. Subtract the surface pressure corresponding to each SOC value during the Nth charging cycle from the surface pressure corresponding to the same SOC value during the NAth charging cycle to obtain a first sub-pressure difference;

[0069] 303. Subtract the surface pressure corresponding to each SOC value during the Ath charging cycle from the surface pressure corresponding to the same SOC value during the first charging cycle to obtain a second sub-pressure difference.

[0070] It should be noted that, in actual applications, there is no strict timing relationship between step 302 and step 303; that is, they can be executed simultaneously, or any one step can be executed first, depending on actual needs and is not limited here.

[0071] 304. Subtract the second sub-pressure difference corresponding to each SOC value from the first sub-pressure difference corresponding to the same SOC value to obtain a second pressure difference, and associate it with each SOC value one-to-one to obtain a second pressure difference-SOC curve.

[0072] Among them, the surface pressure corresponding to each SOC value in the Nth week of charging of the lithium-ion battery to be evaluated is subtracted from the surface pressure corresponding to the same SOC value in the NAth week of charging. The change in pressure difference information over a relatively short period of time is used to represent the pressure signal caused by lithium precipitation in the Nth week of battery charging. This can eliminate the impact of factors such as changes in pressure value information caused by changes in electrode structure and side reactions in the middle and late stages of operation on the detection accuracy. At the same time, the pressure difference between the same operating cycle interval in the early and middle and late stages of the lithium-ion battery to be evaluated, such as the pressure difference between the Ath week charging process and the first week charging process, is used as a comparison pressure-SOC curve to accurately obtain the changes in pressure information values ​​caused by lithium precipitation in the middle and late stages of battery operation.

[0073] 305 : Update the threshold curve, and determine the lithium deposition condition of the lithium-ion battery to be evaluated based on the positional relationship between the second pressure difference-SOC curve and the updated threshold curve.

[0074] Among them, the threshold curve after each update is located below the previous threshold curve, which means that after each update, the threshold corresponding to the same SOC value is decreasing. This effect can be achieved by reducing the charging current of the fresh battery. On the basis of the initial charging current of 5C or 3C, the charging current is reduced to 2C, 1.5 or 1C, etc.

[0075] During the operation of lithium-ion batteries, due to side reactions such as the formation of SEI films inside the batteries, the electrode structure of the battery will undergo irreversible changes in the electrode thickness direction. Therefore, as the battery operates, the maximum thickness of the battery and the maximum stress on the battery surface both increase irreversibly with operation, which makes it challenging to accurately evaluate the lithium deposition condition and health status of the lithium-ion battery after operating under working conditions. In order to eliminate the changes in pressure information caused by changes in the battery electrode structure after operating under working conditions and accurately evaluate the lithium deposition of lithium-ion batteries in the late stage of operation, the lithium deposition evaluation method for lithium-ion batteries provided in this embodiment adds a second pressure difference determination on the basis of the first pressure difference determination. In the second pressure difference determination process, the difference information between the pressure information of the lithium-ion battery to be evaluated and the pressure information of the adjacent cycle is used as the determination threshold, which can eliminate the changes in pressure information caused by aging of the electrode structure in the late stage of operating under working conditions and more accurately reflect the changes in the pressure signal caused by lithium deposition, so that the lithium deposition evaluation method of this embodiment can obtain higher lithium deposition evaluation accuracy, and by continuously reducing the threshold, the lithium deposition evaluation precision can be further improved.

[0076] In one embodiment, determining the lithium deposition condition of the lithium-ion battery to be evaluated based on the positional relationship between the second pressure difference-SOC curve and the updated threshold curve may include:

[0077] If, in the standard coordinate system, the second pressure difference-SOC curve is below the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has not undergone lithium deposition;

[0078] If, in the standard coordinate system, the second pressure difference-SOC curve is above the updated threshold curve, and the second pressure difference-SOC curve coincides with the updated threshold curve, then reducing the value of A and recalculating the second pressure difference-SOC curve, then updating the threshold curve, and determining the lithium deposition condition of the lithium-ion battery to be evaluated based on the positional relationship between the second pressure difference-SOC curve and the updated threshold curve;

[0079] When A is less than or equal to the interval threshold, if the second pressure difference-SOC curve is below the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has not undergone lithium deposition;

[0080] When A is less than or equal to the interval threshold, if the second pressure difference-SOC curve is above the updated threshold curve, or the second pressure difference-SOC curve coincides with the updated threshold curve, it is determined that lithium plating occurs in the lithium-ion battery to be evaluated.

[0081] As the value of A becomes smaller and smaller, the lithium plating pressure signal of the lithium-ion battery to be evaluated will become less and less obvious. Therefore, it is necessary to continuously set a more refined threshold curve to determine whether the lithium-ion battery to be evaluated has lithium plating. To achieve this effect, the charging current of the fresh battery can be gradually reduced from 5C to 0.05C.

[0082] When the value of A is small to a certain extent, until it is less than or equal to the interval threshold, if the second pressure difference-SOC curve is still above the updated threshold curve or coincides with the updated threshold curve, it is determined to be lithium deposition; if the second pressure difference-SOC curve is below the updated threshold curve, it is determined to be no lithium deposition.

[0083] The interval threshold may be set to 5 weeks or less.

[0084] This embodiment reduces the change in pressure information caused by aging of the electrode structure by continuously reducing the value of A and setting a finer threshold curve, thereby determining whether the lithium-ion battery to be evaluated has deposited lithium, so that the lithium deposition conditions are continuously approaching the critical level, thereby improving the accuracy of the determination.

[0085] Figure 4 This is a fourth flow chart of the lithium ion battery lithium deposition evaluation method provided in the embodiment of the present application. Figure 4 In one embodiment, after determining that the lithium-ion battery to be evaluated has lithium deposition, a method for optimizing the non-lithium deposition charging current and SOC charging range of the lithium-ion battery to be evaluated may include:

[0086] 401. Charge a lithium-ion battery to be evaluated using a first current and a second current, respectively, obtain a pressure difference corresponding to the same SOC value of the lithium-ion battery to be evaluated under the first current and the second current, and obtain a third pressure difference-SOC curve;

[0087] The first current is a low current current, and the second current is a current smaller than the operating current.

[0088] 402. Compare the third pressure difference-SOC curve with a standard third pressure difference-SOC curve to optimize the non-lithium deposition charging current and SOC charging range of the lithium-ion battery to be evaluated.

[0089] The third pressure difference-SOC curve is a third pressure difference-SOC curve of a fresh battery at two different currents.

[0090] This embodiment reduces the charging current of the lithium-ion battery to be evaluated, calculates the third pressure difference-SOC curve of the lithium-ion battery to be evaluated at different currents, and compares it with the standard third pressure difference-SOC curve. This can optimize the non-lithium deposition charging current and SOC charging range of the lithium-ion battery to be evaluated, thereby obtaining a better charging strategy.

[0091] The lithium ion battery lithium deposition evaluation device provided in an embodiment of the present application is described below. The lithium ion battery lithium deposition evaluation device described below and the lithium ion battery lithium deposition evaluation method described above can be referenced to each other.

[0092] Figure 5 This is a schematic diagram of the structure of the lithium ion battery lithium deposition evaluation device provided in the embodiment of the present application. Figure 5 , an embodiment of the present application provides a lithium-ion battery lithium deposition evaluation device, which may include:

[0093] The pressure-SOC curve generating module 501 is configured to obtain a pressure-SOC curve of the lithium-ion battery to be evaluated during the charging process according to the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process.

[0094] The pressure difference-SOC curve generating module 502 is configured to: obtain a first pressure difference by subtracting the surface pressure corresponding to each SOC value of the pressure-SOC curve to be compared from the surface pressure corresponding to the same SOC value of the standard pressure-SOC curve, and associate it with each SOC value to generate a first pressure difference-SOC curve; the standard pressure-SOC curve is a pressure-SOC curve of a fresh battery under the same operating conditions as the lithium-ion battery to be evaluated; the fresh battery is a lithium-ion battery that has not been subjected to any operating conditions after pre-charging and formation;

[0095] The first lithium deposition evaluation module 503 is configured to determine that the lithium-ion battery to be evaluated has not deposited lithium if the first pressure difference-SOC curve is below a threshold curve in a standard coordinate system, wherein the standard coordinate system has the SOC value as the horizontal axis and the pressure value as the vertical axis.

[0096] The lithium ion battery lithium deposition evaluation device provided in this embodiment determines whether the lithium ion battery to be evaluated has deposited lithium by comparing the positional relationship between the first pressure difference-SOC curve and the threshold curve. Since the first pressure difference is the change in the surface pressure of the lithium ion battery to be evaluated and the surface pressure of a fresh battery corresponding to the same SOC value under the same operating current, the change in the pressure difference is more meaningful for reference, so that the lithium deposition evaluation method of this embodiment can obtain higher lithium deposition evaluation accuracy, thereby improving the accuracy of lithium deposition evaluation.

[0097] In one embodiment, the pressure-SOC curve generation module 501 is specifically configured to:

[0098] The surface pressure and the SOC value are matched one by one according to time to obtain a surface pressure-SOC curve of the lithium ion to be evaluated;

[0099] If the absolute value of the difference between the open-circuit voltage of the lithium-ion battery to be evaluated at the end of charging and the open-circuit voltage of the fresh battery at the end of charging is greater than a difference threshold, correcting the surface pressure-SOC curve, and using the corrected surface pressure-SOC curve as the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated;

[0100] If the absolute value of the difference between the open-circuit voltage of the lithium-ion battery to be evaluated at the end of charging and the open-circuit voltage of the fresh battery at the end of charging is less than or equal to the difference threshold, the surface pressure-SOC curve is used as the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated.

[0101] In one embodiment, the pressure-SOC curve generation module 501 is specifically configured to:

[0102] The surface pressure-SOC curve is shifted based on the SOC value corresponding to the open circuit voltage of the lithium-ion battery to be evaluated at the end of charging, to obtain the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated.

[0103] In one embodiment, a second lithium deposition evaluation module (not shown) is further included, which is configured to:

[0104] If, in the standard coordinate system, the first pressure difference-SOC curve is above the threshold curve, or the first pressure difference-SOC curve coincides with the threshold curve, a second pressure difference-SOC curve is obtained according to the surface pressure change difference of the lithium-ion battery to be evaluated during the charging process;

[0105] The threshold curve is updated, and the lithium plating condition of the lithium-ion battery to be evaluated is determined according to the positional relationship between the second pressure difference-SOC curve and the updated threshold curve, wherein each updated threshold curve is located below the previous threshold curve.

[0106] In one embodiment, the second lithium deposition assessment module is specifically configured to:

[0107] Select the surface pressure and SOC value corresponding to the Nth charging process, the NAth charging process, the Ath charging process, and the first charging process of the lithium-ion battery to be evaluated, where A is an integer greater than or equal to 1 and less than or equal to 500, and N is an integer greater than A;

[0108] Subtracting the surface pressure corresponding to each SOC value during the Nth charging cycle from the surface pressure corresponding to the same SOC value during the NAth charging cycle to obtain a first sub-pressure difference;

[0109] Subtract the surface pressure corresponding to each SOC value during the Ath week of charging from the surface pressure corresponding to the same SOC value during the first week of charging to obtain a second sub-pressure difference;

[0110] A second pressure difference obtained by subtracting the second sub-pressure difference corresponding to each SOC value from the first sub-pressure difference corresponding to the same SOC value is matched one-to-one with each SOC value to obtain a second pressure difference-SOC curve.

[0111] In one embodiment, the second lithium deposition assessment module is specifically configured to:

[0112] If, in the standard coordinate system, the second pressure difference-SOC curve is below the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has not undergone lithium deposition;

[0113] If, in the standard coordinate system, the second pressure difference-SOC curve is above the updated threshold curve, or the second pressure difference-SOC curve coincides with the updated threshold curve, then after reducing the value of A and recalculating the second pressure difference-SOC curve, the threshold curve is updated, and the step of determining the lithium deposition condition of the lithium-ion battery to be evaluated based on the positional relationship between the second pressure difference-SOC curve and the updated threshold curve is performed, until A is less than or equal to the interval threshold. If the second pressure difference-SOC curve is below the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has not deposited lithium; if the second pressure difference-SOC curve is above the updated threshold curve, or the second pressure difference-SOC curve coincides with the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has deposited lithium.

[0114] In one embodiment, a lithium-ion battery optimization module (not shown) is further included, which is used to:

[0115] Charging the lithium-ion battery to be evaluated using a first current and a second current, respectively, obtaining a pressure difference corresponding to the same SOC value of the lithium-ion battery to be evaluated under the first current and the second current, and obtaining a third pressure difference-SOC curve; the first current is a current under low current, and the second current is a current less than the operating current;

[0116] The third pressure difference-SOC curve is compared with a standard third pressure difference-SOC curve to optimize the non-lithium precipitation charging current and SOC charging range of the lithium-ion battery to be evaluated. The standard third pressure difference-SOC curve is the third pressure difference-SOC curve of the fresh battery at two different currents.

[0117] Figure 6 An example of a physical structure diagram of an electronic device is shown in FIG. Figure 6As shown, the electronic device may include: a processor 610, a communication interface 620, a memory 630 and a communication bus 640, wherein the processor 610, the communication interface 620, and the memory 630 communicate with each other via the communication bus 640. The processor 610 may call a computer program in the memory 630 to execute the steps of the lithium ion battery lithium deposition evaluation method, for example, including:

[0118] Obtaining a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated according to the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process;

[0119] A first pressure difference is obtained by subtracting the surface pressure corresponding to each SOC value of the pressure-SOC curve to be compared from the surface pressure corresponding to the same SOC value of the standard pressure-SOC curve, and the first pressure difference is matched with each SOC value to obtain a first pressure difference-SOC curve; the standard pressure-SOC curve is a pressure-SOC curve of a fresh battery under the same operating conditions as the lithium-ion battery to be evaluated; the fresh battery is a lithium-ion battery that has not been subjected to any operating conditions after pre-charge and formation;

[0120] If the first pressure difference-SOC curve is below the threshold curve in a standard coordinate system, it is determined that the lithium-ion battery to be evaluated has not deposited lithium; the standard coordinate system is a coordinate system with the SOC value as the horizontal axis and the pressure value as the vertical axis.

[0121] In addition, the logic instructions in the above-mentioned memory 630 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0122] On the other hand, an embodiment of the present application further provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can perform the steps of the lithium-ion battery lithium deposition evaluation method provided in the above embodiments, for example, including:

[0123] Obtaining a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated according to the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process;

[0124] A first pressure difference is obtained by subtracting the surface pressure corresponding to each SOC value of the pressure-SOC curve to be compared from the surface pressure corresponding to the same SOC value of the standard pressure-SOC curve, and the first pressure difference is matched with each SOC value to obtain a first pressure difference-SOC curve; the standard pressure-SOC curve is a pressure-SOC curve of a fresh battery under the same operating conditions as the lithium-ion battery to be evaluated; the fresh battery is a lithium-ion battery that has not been subjected to any operating conditions after pre-charge and formation;

[0125] If the first pressure difference-SOC curve is below the threshold curve in a standard coordinate system, it is determined that the lithium-ion battery to be evaluated has not deposited lithium; the standard coordinate system is a coordinate system with the SOC value as the horizontal axis and the pressure value as the vertical axis.

[0126] On the other hand, an embodiment of the present application further provides a processor-readable storage medium, wherein the processor-readable storage medium stores a computer program, wherein the computer program is configured to cause a processor to execute the steps of the methods provided in the above embodiments, for example, including:

[0127] Obtaining a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated according to the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process;

[0128] A first pressure difference is obtained by subtracting the surface pressure corresponding to each SOC value of the pressure-SOC curve to be compared from the surface pressure corresponding to the same SOC value of the standard pressure-SOC curve, and the first pressure difference is matched with each SOC value to obtain a first pressure difference-SOC curve; the standard pressure-SOC curve is a pressure-SOC curve of a fresh battery under the same operating conditions as the lithium-ion battery to be evaluated; the fresh battery is a lithium-ion battery that has not been subjected to any operating conditions after pre-charge and formation;

[0129] If the first pressure difference-SOC curve is below the threshold curve in a standard coordinate system, it is determined that the lithium-ion battery to be evaluated has not deposited lithium; the standard coordinate system is a coordinate system with the SOC value as the horizontal axis and the pressure value as the vertical axis.

[0130] The processor-readable storage medium can be any available medium or data storage device that can be accessed by the processor, including but not limited to magnetic storage (such as floppy disks, hard disks, magnetic tapes, magneto-optical disks (MO)), optical storage (such as CDs, DVDs, BDs, HVDs, etc.), and semiconductor storage (such as ROMs, EPROMs, EEPROMs, non-volatile memories (NANDFLASH), solid-state drives (SSDs)), etc.

[0131] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0132] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, or of course, by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the existing technology can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or certain parts of the embodiments.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A lithium ion battery lithium deposition evaluation method, characterized in that: include: Obtaining a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated according to the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process; A first pressure difference is obtained by subtracting the surface pressure corresponding to each SOC value of the pressure-SOC curve to be compared from the surface pressure corresponding to the same SOC value of the standard pressure-SOC curve, and the first pressure difference is matched with each SOC value to obtain a first pressure difference-SOC curve; the standard pressure-SOC curve is a pressure-SOC curve of a fresh battery under the same operating conditions as the lithium-ion battery to be evaluated; the fresh battery is a lithium-ion battery that has not been subjected to any operating conditions after pre-charge and formation; If the first pressure difference-SOC curve is below the threshold curve in a standard coordinate system, it is determined that the lithium-ion battery to be evaluated has not deposited lithium; the standard coordinate system is a coordinate system with the SOC value as the horizontal axis and the pressure value as the vertical axis; If, in the standard coordinate system, the first pressure difference-SOC curve is above the threshold curve, or the first pressure difference-SOC curve coincides with the threshold curve, a second pressure difference-SOC curve is obtained according to the surface pressure change difference of the lithium-ion battery to be evaluated during the charging process, including: Select the surface pressure and SOC value corresponding to the Nth charging process, the NAth charging process, the Ath charging process, and the first charging process of the lithium-ion battery to be evaluated, where A is an integer greater than or equal to 1 and less than or equal to 500, and N is an integer greater than A; Subtracting the surface pressure corresponding to each SOC value during the Nth charging cycle from the surface pressure corresponding to the same SOC value during the NAth charging cycle to obtain a first sub-pressure difference; Subtract the surface pressure corresponding to each SOC value during the Ath week of charging from the surface pressure corresponding to the same SOC value during the first week of charging to obtain a second sub-pressure difference; A second pressure difference value obtained by subtracting the second sub-pressure difference value corresponding to each SOC value from the first sub-pressure difference value corresponding to the same SOC value is corresponded to each SOC value one by one to obtain a second pressure difference value-SOC curve; The threshold curve is updated, and the lithium plating condition of the lithium-ion battery to be evaluated is determined according to the positional relationship between the second pressure difference-SOC curve and the updated threshold curve, wherein each updated threshold curve is located below the previous threshold curve.

2. The lithium ion battery lithium deposition evaluation method according to claim 1, wherein The step of obtaining a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated based on the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process includes: The surface pressure and the SOC value are matched one by one according to time to obtain a surface pressure-SOC curve of the lithium ion to be evaluated; If the absolute value of the difference between the open-circuit voltage of the lithium-ion battery to be evaluated at the end of charging and the open-circuit voltage of the fresh battery at the end of charging is greater than a difference threshold, correcting the surface pressure-SOC curve, and using the corrected surface pressure-SOC curve as the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated; If the absolute value of the difference between the open-circuit voltage of the lithium-ion battery to be evaluated at the end of charging and the open-circuit voltage of the fresh battery at the end of charging is less than or equal to the difference threshold, the surface pressure-SOC curve is used as the pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated.

3. The lithium ion battery lithium deposition evaluation method according to claim 2, wherein The step of correcting the surface pressure-SOC curve and using the corrected surface pressure-SOC curve as a pressure-SOC curve to be compared during the charging process of the lithium-ion battery to be evaluated includes: The surface pressure-SOC curve is shifted based on the SOC value corresponding to the open circuit voltage of the lithium ion battery to be evaluated at the end of charging on the standard voltage-SOC curve to obtain the pressure-SOC curve to be compared during the charging process of the lithium ion battery to be evaluated.

4. The lithium ion battery lithium deposition evaluation method according to claim 1, wherein The determining, based on the positional relationship between the second pressure difference-SOC curve and the updated threshold curve, the lithium plating condition of the lithium-ion battery to be evaluated includes: If, in the standard coordinate system, the second pressure difference-SOC curve is below the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has not undergone lithium deposition; If, in the standard coordinate system, the second pressure difference-SOC curve is above the updated threshold curve, or the second pressure difference-SOC curve coincides with the updated threshold curve, then after reducing the value of A and recalculating the second pressure difference-SOC curve, the threshold curve is updated, and the step of determining the lithium deposition condition of the lithium-ion battery to be evaluated based on the positional relationship between the second pressure difference-SOC curve and the updated threshold curve is performed, until A is less than or equal to the interval threshold. If the second pressure difference-SOC curve is below the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has not deposited lithium; if the second pressure difference-SOC curve is above the updated threshold curve, or the second pressure difference-SOC curve coincides with the updated threshold curve, it is determined that the lithium-ion battery to be evaluated has deposited lithium.

5. The lithium ion battery lithium deposition evaluation method according to claim 4, wherein After determining that the lithium ion battery to be evaluated has deposited lithium, the method includes: Charging the lithium-ion battery to be evaluated using a first current and a second current, respectively, obtaining a pressure difference corresponding to the same SOC value of the lithium-ion battery to be evaluated under the first current and the second current, and obtaining a third pressure difference-SOC curve; the first current is a current under low current, and the second current is a current less than the operating current; The third pressure difference-SOC curve is compared with a standard third pressure difference-SOC curve to optimize the non-lithium precipitation charging current and SOC charging range of the lithium-ion battery to be evaluated. The standard third pressure difference-SOC curve is the third pressure difference-SOC curve of the fresh battery at two different currents.

6. A lithium ion battery lithium deposition evaluation device, characterized in that: include: a pressure-SOC curve generation module for comparison, configured to obtain a pressure-SOC curve for comparison during the charging process of the lithium-ion battery to be evaluated based on the surface pressure, open circuit voltage, and SOC value of the lithium-ion battery to be evaluated during the charging process; a pressure difference-SOC curve generating module, configured to: obtain a first pressure difference by subtracting the surface pressure corresponding to each SOC value of the pressure-SOC curve to be compared from the surface pressure corresponding to the same SOC value of the standard pressure-SOC curve, and assigning a one-to-one correspondence between the first pressure difference and each SOC value to generate a first pressure difference-SOC curve; the standard pressure-SOC curve is a pressure-SOC curve of a fresh battery under the same operating conditions as the lithium-ion battery to be evaluated; the fresh battery is a lithium-ion battery that has not been subjected to any operating conditions after pre-charging and formation; a first lithium deposition evaluation module, configured to: determine that the lithium-ion battery to be evaluated has not deposited lithium if the first pressure difference-SOC curve is below a threshold curve in a standard coordinate system; the standard coordinate system is a coordinate system with the SOC value as the horizontal axis and the pressure value as the vertical axis; A second lithium deposition assessment module is configured to obtain a second pressure difference-SOC curve based on a surface pressure change difference of the lithium-ion battery to be assessed during charging if the first pressure difference-SOC curve is above the threshold curve in the standard coordinate system, or the first pressure difference-SOC curve coincides with the threshold curve, including: Select the surface pressure and SOC value corresponding to the Nth charging process, the NAth charging process, the Ath charging process, and the first charging process of the lithium-ion battery to be evaluated, where A is an integer greater than or equal to 1 and less than or equal to 500, and N is an integer greater than A; Subtracting the surface pressure corresponding to each SOC value during the Nth charging cycle from the surface pressure corresponding to the same SOC value during the NAth charging cycle to obtain a first sub-pressure difference; Subtract the surface pressure corresponding to each SOC value during the Ath week of charging from the surface pressure corresponding to the same SOC value during the first week of charging to obtain a second sub-pressure difference; A second pressure difference value obtained by subtracting the second sub-pressure difference value corresponding to each SOC value from the first sub-pressure difference value corresponding to the same SOC value is corresponded to each SOC value one by one to obtain a second pressure difference value-SOC curve; The threshold curve is updated, and the lithium plating condition of the lithium-ion battery to be evaluated is determined according to the positional relationship between the second pressure difference-SOC curve and the updated threshold curve, wherein each updated threshold curve is located below the previous threshold curve.

7. An electronic device comprising a processor and a memory storing a computer program, characterized in that: When the processor executes the computer program, the steps of the lithium ion battery lithium deposition evaluation method according to any one of claims 1 to 5 are implemented.

8. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the lithium ion battery lithium deposition evaluation method according to any one of claims 1 to 5 are implemented.

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