Lithium ion battery electrical abuse stability evaluation method and device and electronic equipment

Abstract

The invention discloses a lithium ion battery electrical abuse stability evaluation method and device and electronic equipment, and belongs to the technical field of lithium ion batteries. The method comprises the following steps: carrying out multiple overcharge cycles on the lithium ion battery by adopting constant current; wherein one overcharge cycle comprises discharging the lithium ion battery to a discharge cut-off voltage and charging the lithium ion battery to an overcharge cut-off voltage; and evaluating the overcharge stability of the lithium ion battery according to the discharge capacity of the lithium ion battery before multiple overcharge cycles and the discharge capacity of the lithium ion battery after multiple overcharge cycles. According to the method, the voltage is used as the cut-off condition of overcharge, so that side reactions caused by overcharge in the battery stability evaluation process can be reduced, the evaluation result is more reliable, the discharge capacity of the battery before and after multiple overcharge cycles is used for evaluation, and the evaluation efficiency is improved. The influence of factors such as a battery manufacturing process and a use environment on an evaluation result can be reduced, and the accuracy of electric abuse stability evaluation of the lithium ion battery is improved.

Description

Technical Field

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

[0002] Lithium-ion batteries are widely used in electric vehicles and other fields due to their high energy density, long cycle life and environmental protection. However, during use, lithium-ion batteries may encounter electrical abuse such as overcharging, over-discharging, and short circuit, which may cause battery performance degradation and even cause safety problems such as fire and explosion. Therefore, testing and evaluating the electrical abuse stability of lithium-ion batteries is of great significance to ensure the safety and reliability of batteries.

[0003] The existing lithium-ion battery abuse stability assessment method is mainly to evaluate the stability of the battery by conducting overcharge, over-discharge, short-circuit and other tests on the battery, and then observing the changes in battery parameters such as voltage, current, and temperature. In addition, there are some methods that evaluate the stability of the battery by dissecting the battery and observing the changes in the internal structure of the battery.

[0004] However, there are some problems with the existing lithium-ion battery abuse stability assessment methods. First, these methods can only simulate the stability of the battery under extreme conditions, but cannot reflect the stability of the battery in actual use. Second, the test results of these methods often cannot accurately reflect the true performance of the battery, because the performance of the battery is affected by many factors, such as the battery manufacturing process, the battery usage environment, etc. Summary of the invention

[0005] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a lithium-ion battery electrical abuse stability assessment method, device and electronic device to improve the accuracy of lithium-ion battery electrical abuse stability assessment.

[0006] In a first aspect, the present application provides a method for evaluating the electrical abuse stability of a lithium-ion battery, comprising:

[0007] The lithium-ion battery is subjected to multiple overcharging cycles using a constant current; wherein one overcharging cycle includes discharging the lithium-ion battery to a discharge cut-off voltage and charging the lithium-ion battery to an overcharging cut-off voltage;

[0008] The overcharge stability of the lithium ion battery is evaluated according to the discharge capacity of the lithium ion battery before multiple overcharge cycles and the discharge capacity of the lithium ion battery after multiple overcharge cycles.

[0009] According to the lithium-ion battery electrical abuse stability evaluation method of the present application, the lithium-ion battery is subjected to multiple overcharge cycles by using a constant current; wherein one overcharge cycle includes discharging the lithium-ion battery to a discharge cut-off voltage and charging the lithium-ion battery to an overcharge cut-off voltage; the overcharge stability of the lithium-ion battery is evaluated based on the discharge capacity of the lithium-ion battery before multiple overcharge cycles and the discharge capacity of the lithium-ion battery after multiple overcharge cycles. The embodiment of the present application adopts voltage as the overcharge cut-off condition, which can reduce the side reactions caused by overcharging during the battery stability evaluation process, making the evaluation result more reliable, and the use of the battery discharge capacity before and after multiple overcharge cycles for evaluation can reduce the impact of factors such as battery manufacturing process and use environment on the evaluation result, thereby improving the accuracy of the lithium-ion battery electrical abuse stability evaluation.

[0010] According to one embodiment of the present application, the overcharge stability of the lithium-ion battery is evaluated according to the discharge capacity of the lithium-ion battery before multiple overcharge cycles and the discharge capacity of the lithium-ion battery after multiple overcharge cycles, including:

[0011] Calculating the capacity retention rate of the lithium ion battery after multiple overcharge cycles according to the discharge capacity of the lithium ion battery before multiple overcharge cycles and the discharge capacity of the lithium ion battery after multiple overcharge cycles;

[0012] The overcharge stability of the lithium ion battery was evaluated based on the capacity retention rate.

[0013] In this embodiment, the capacity retention rate directly reflects the degree of battery performance degradation after multiple overcharging cycles, and is a key indicator for evaluating the battery health status and predicting its remaining service life. The capacity retention rate is used as an evaluation indicator to improve the reliability of battery overcharging stability assessment.

[0014] According to one embodiment of the present application, evaluating the overcharge stability of the lithium-ion battery according to the capacity retention rate includes:

[0015] Calculating the degree of loss of active material of the lithium-ion battery after multiple overcharge cycles;

[0016] The overcharge stability of the lithium ion battery was evaluated based on the active material loss degree and the capacity retention rate.

[0017] In this embodiment, the calculation of the degree of active material loss can reveal the tolerance of the battery under extreme conditions. Combined with the capacity retention rate, this indicator reflects the ability of the battery to maintain its initial discharge capacity after an overcharge cycle, and further provides quantitative data on battery performance degradation. This evaluation method can not only be used for laboratory research, but also for battery production and quality control, and has important practical value for improving the stability and safety of lithium-ion batteries for electric vehicles.

[0018] According to one embodiment of the present application, the calculating the degree of loss of active material of the lithium-ion battery after multiple overcharge cycles includes:

[0019] Differentiating a first relationship curve between the voltage and capacity of the lithium-ion battery before multiple overcharging cycles to obtain a first differential voltage curve; Differentiating a second relationship curve between the voltage and capacity of the lithium-ion battery after multiple overcharging cycles to obtain a second differential voltage curve;

[0020] Calculating respectively the positive electrode active material loss, the negative electrode active material loss and the active lithium ion loss of the lithium ion battery after multiple overcharge cycles according to the first differential voltage curve and the second differential voltage curve;

[0021] The active material loss degree is calculated according to the positive electrode active material loss, the negative electrode active material loss and the active lithium ion loss.

[0022] According to one embodiment of the present application, according to the formula

[0023]

[0024] Calculate the loss of positive electrode active materials, negative electrode active materials and active lithium ion loss;

[0025] Among them, K LAM Indicates the loss of positive electrode active material, K' LAM Indicates the loss of negative electrode active material, K LI+ represents the loss of active lithium ions, Q 1,0 represents the distance between the positive peaks of the first differential voltage curve, Q 1,n represents the distance between the positive peaks of the second differential voltage curve, Q 2,0 represents the distance between the negative peaks of the first differential voltage curve, Q 1,n represents the distance between the negative peaks of the second differential voltage curve, Q 3,0 represents the distance between the positive peak and the negative peak of the first differential voltage curve, Q 3,n Represents the distance between the positive peak and the negative peak of the second differential voltage curve.

[0026] In this embodiment, by differentiating the voltage-capacity curve of the battery, the differential voltage curve obtained can reveal the sensitivity of the voltage to the capacity change of the battery during the charge and discharge process, thereby reflecting the dynamic characteristics of the electrochemical reaction inside the battery. Before and after the overcharge cycle, the electrochemical behavior of the battery may change. These changes are manifested as changes in peak values, valley values ​​and their areas on the differential voltage curve. The changes in these characteristic points are directly related to the loss of positive and negative active materials and active lithium ions. By comparing the differential voltage curves before and after the cycle, the degree of loss of positive and negative active materials and the reduction of active lithium ions can be accurately analyzed.

[0027] According to one embodiment of the present application, before a lithium-ion battery is subjected to multiple overcharging cycles using a constant current, the method includes:

[0028] Use target current values ​​of different rates to perform overcharge tests on lithium-ion batteries, and obtain a curve showing the relationship between the rate of the target current value and the battery rupture valve voltage;

[0029] The constant current value used for performing multiple overcharging cycles on the lithium-ion battery is determined according to the relationship curve between the multiple of the target current value and the battery rupture valve voltage.

[0030] In this embodiment, the lithium-ion battery is overcharged by using target current values ​​of different rates, and a relationship curve between the target current value rate and the battery rupture valve voltage is obtained accordingly. This can effectively determine a constant current value suitable for use when performing multiple overcharge cycles, and can provide a scientific current setting basis for the battery overcharge test, so that the test can fully challenge the safety limit of the battery without causing excessive side reactions of the battery due to excessive current, thereby losing the meaning of the test, thereby improving the reliability of the battery overcharge stability assessment.

[0031] According to one embodiment of the present application, before a lithium-ion battery is subjected to multiple overcharging cycles using a constant current, the method includes:

[0032] Use constant current to perform overcharge test on fully charged lithium-ion batteries, and obtain the curve of voltage change with battery capacity during the test;

[0033] The overcharge cut-off voltage is determined according to a curve of voltage variation with battery capacity during the test process.

[0034] In this embodiment, by using a constant current to perform an overcharge test on a fully charged lithium-ion battery, and determining the overcharge cut-off voltage based on a curve of voltage variation with battery capacity during the test, a clear safety threshold can be provided for the safe use and testing of lithium-ion batteries, and a reasonable overcharge voltage upper limit can be set based on the actual battery response to reduce excessive side reactions of the battery during the overcharge process, thereby improving the reliability of the battery overcharge stability assessment.

[0035] In a second aspect, the present application provides a lithium-ion battery electrical abuse stability assessment device, comprising:

[0036] An overcharge cycle module, used for performing multiple overcharge cycles on the lithium-ion battery using a constant current; wherein one overcharge cycle includes discharging the lithium-ion battery to a discharge cut-off voltage and charging the lithium-ion battery to an overcharge cut-off voltage;

[0037] The evaluation module is used to evaluate the overcharge stability of the lithium ion battery according to the discharge capacity of the lithium ion battery before multiple overcharge cycles and the discharge capacity of the lithium ion battery after multiple overcharge cycles.

[0038] According to the lithium-ion battery electrical abuse stability evaluation method of the present application, the lithium-ion battery is subjected to multiple overcharge cycles by using a constant current; wherein one overcharge cycle includes discharging the lithium-ion battery to a discharge cut-off voltage and charging the lithium-ion battery to an overcharge cut-off voltage; the overcharge stability of the lithium-ion battery is evaluated based on the discharge capacity of the lithium-ion battery before multiple overcharge cycles and the discharge capacity of the lithium-ion battery after multiple overcharge cycles. The embodiment of the present application adopts voltage as the overcharge cut-off condition, which can reduce the side reactions caused by overcharging during the battery stability evaluation process, making the evaluation result more reliable, and the use of the battery discharge capacity before and after multiple overcharge cycles for evaluation can reduce the impact of factors such as battery manufacturing process and use environment on the evaluation result, thereby improving the accuracy of the lithium-ion battery electrical abuse stability evaluation.

[0039] In a third aspect, the present application provides a controller comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method for evaluating the electrical abuse stability of a lithium-ion battery as described in the first aspect above is implemented.

[0040] In a fourth aspect, the present application provides a non-transitory computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the method for evaluating the electrical abuse stability of a lithium-ion battery as described in the first aspect above is implemented.

[0041] In a fifth aspect, the present application provides a chip, comprising a processor and a communication interface, wherein the communication interface is coupled to the processor, and the processor is used to run a program or instruction to implement the lithium-ion battery electrical abuse stability assessment method as described in the first aspect above.

[0042] In a sixth aspect, the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the lithium-ion battery electrical abuse stability assessment method as described in the first aspect above.

[0043] The above one or more technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0044] According to the lithium-ion battery electrical abuse stability evaluation method of the present application, the lithium-ion battery is subjected to multiple overcharge cycles by using a constant current; wherein one overcharge cycle includes discharging the lithium-ion battery to a discharge cut-off voltage and charging the lithium-ion battery to an overcharge cut-off voltage; the overcharge stability of the lithium-ion battery is evaluated based on the discharge capacity of the lithium-ion battery before multiple overcharge cycles and the discharge capacity of the lithium-ion battery after multiple overcharge cycles. The embodiment of the present application adopts voltage as the overcharge cut-off condition, which can reduce the side reactions caused by overcharging during the battery stability evaluation process, making the evaluation result more reliable, and adopts the discharge capacity of the battery before and after multiple overcharge cycles for evaluation, which can reduce the influence of factors such as battery manufacturing process and use environment on the evaluation result, and improves the accuracy of the lithium-ion battery electrical abuse stability evaluation.

[0045] Furthermore, in some embodiments, the capacity retention rate directly reflects the degree of battery performance degradation after multiple overcharging cycles, and is a key indicator for evaluating the battery health status and predicting its remaining service life. The capacity retention rate is used as an evaluation indicator to improve the reliability of battery overcharge stability assessment.

[0046] Furthermore, in some embodiments, the calculation of the degree of loss of active materials can reveal the tolerance of the battery under extreme conditions. Combined with the capacity retention rate, this indicator reflects the ability of the battery to maintain its initial discharge capacity after an overcharge cycle, and further provides quantitative data on battery performance degradation. This evaluation method can not only be used for laboratory research, but also for battery production and quality control, and has important practical value for improving the stability and safety of lithium-ion batteries for electric vehicles.

[0047] Furthermore, in some embodiments, by differentiating the voltage-capacity curve of the battery, the differential voltage curve obtained can reveal the sensitivity of the voltage to the capacity change of the battery during the charge and discharge process, thereby reflecting the dynamic characteristics of the electrochemical reaction inside the battery. Before and after the overcharge cycle, the electrochemical behavior of the battery may change. These changes are manifested as changes in peak values, valley values ​​and their areas on the differential voltage curve. The changes in these characteristic points are directly related to the loss of positive and negative active substances and active lithium ions. By comparing the differential voltage curves before and after the cycle, the degree of loss of positive and negative active substances and the reduction of active lithium ions can be accurately analyzed.

[0048] Furthermore, in some embodiments, by using constant currents of different rates to perform overcharge tests on lithium-ion batteries, and obtaining a relationship curve between the constant current rate and the battery rupture valve voltage, it is possible to effectively determine a constant current value suitable for use when performing multiple overcharge cycles, and provide a scientific current setting basis for battery overcharge testing, so that the test can fully challenge the safety limit of the battery without causing excessive side reactions of the battery due to excessive current, thereby losing the meaning of the test, thereby improving the reliability of battery overcharge stability assessment.

[0049] Furthermore, in some embodiments, by using a constant current to perform an overcharge test on a fully charged lithium-ion battery, and determining the overcharge cut-off voltage based on a curve of voltage variation with battery capacity during the test, a clear safety threshold can be provided for the safe use and testing of lithium-ion batteries, and a reasonable overcharge voltage upper limit can be set based on the actual battery response to reduce excessive side reactions of the battery during the overcharge process, thereby improving the reliability of the battery overcharge stability assessment.

[0050] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0052] Figure 1 It is a schematic flow chart of a method for evaluating the electrical abuse stability of a lithium-ion battery provided in an embodiment of the present application;

[0053] Figure 2It is one of the relationship curves between voltage, temperature and SOC of the lithium iron phosphate battery provided in the embodiment of the present application;

[0054] Figure 3 is a curve showing the relationship between the voltage of the lithium iron phosphate battery provided in the embodiment of the present application and the rate of change of the battery capacity and the SOC;

[0055] Figure 4 It is one of the relationship curves between voltage, temperature and SOC of the ternary lithium battery provided in the embodiment of the present application;

[0056] Figure 5 is a curve showing the relationship between the voltage of the ternary lithium battery provided in the embodiment of the present application and the rate of change of the battery capacity and the SOC;

[0057] Figure 6 This is the second relationship curve between voltage, temperature and SOC of the lithium iron phosphate battery provided in the embodiment of the present application;

[0058] Figure 7 This is the third relationship curve between voltage, temperature and SOC of the lithium iron phosphate battery provided in the embodiment of the present application;

[0059] Figure 8 This is the second relationship curve between voltage, temperature and SOC of the ternary lithium battery provided in the embodiment of the present application;

[0060] Fig. 9 This is the third relationship curve between voltage, temperature and SOC of the ternary lithium battery provided in the embodiment of the present application;

[0061] Fig.10 is a curve showing the relationship between the ratio of the target current value and the battery rupture valve voltage provided in the embodiment of the present application;

[0062] Fig.11 is a differential voltage curve of a ternary lithium battery before and after an overcharge cycle provided in an embodiment of the present application;

[0063] Fig.12 is a differential voltage curve of a ternary lithium battery before and after an overcharge cycle provided in an embodiment of the present application;

[0064] Fig.13 is a schematic diagram of the structure of a lithium-ion battery electrical abuse stability assessment device provided in an embodiment of the present application;

[0065] Fig.14 It is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0067] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0068] Since lithium batteries generate heat and gas when overcharged, the heat includes ohmic heat and heat generated by side reactions, of which ohmic heat accounts for the majority. The side reactions of batteries caused by overcharging are, first, excessive lithium is embedded in the negative electrode, and lithium dendrites grow on the surface of the negative electrode. Secondly, excessive lithium is released from the positive electrode, causing the positive electrode structure to collapse, releasing heat and oxygen. Oxygen will accelerate the decomposition of the electrolyte, and the internal pressure of the battery will continue to rise. After a certain level, the safety valve will open, and the contact between the active material and the air will further generate more heat.

[0069] There are several problems with existing lithium battery overcharge test methods: they mainly rely on observing the performance during the test, such as whether there is smoke, fire or explosion to evaluate the overcharge level. However, this method is difficult to distinguish the differences between similar phenomena, and cannot accurately evaluate the safety performance of the lithium battery to be tested, which brings troubles to the benchmarking evaluation and safety performance optimization development of products. In addition, the state, SOC (State of Charge) and temperature data of different battery samples change inconsistently, and it is impossible to provide quantifiable evaluation results.

[0070] The present application considers that if voltage can be used as the overcharging cutoff condition, the side reactions caused by overcharging during the battery stability evaluation process can be reduced, making the evaluation results more reliable. In addition, by using the discharge capacity of the battery before and after multiple overcharging cycles for evaluation, the impact of factors such as the battery manufacturing process and the use environment on the evaluation results can be reduced. This is expected to solve the problem of inaccurate stability evaluation of lithium-ion batteries in the prior art.

[0071] In conjunction with the accompanying drawings, the lithium-ion battery electrical abuse stability assessment method, device and electronic device provided in the embodiments of the present application are described in detail through specific embodiments and their application scenarios.

[0072] Among them, the lithium-ion battery electrical abuse stability assessment method can be applied to a terminal, and can be specifically executed by hardware or software in the terminal.

[0073] The terminal includes, but is not limited to, a portable communication device such as a mobile phone or tablet computer with a touch-sensitive surface (e.g., a touch screen display and / or a touch pad). It should also be understood that in some embodiments, the terminal may not be a portable communication device, but a desktop computer with a touch-sensitive surface (e.g., a touch screen display and / or a touch pad).

[0074] In the following various embodiments, a terminal including a display and a touch-sensitive surface is described. However, it should be understood that the terminal may include one or more other physical user interface devices such as a physical keyboard, a mouse and a joystick.

[0075] The lithium-ion battery electrical abuse stability assessment method provided in the embodiment of the present application can be executed by an electronic device or a functional module or functional entity in the electronic device that can implement the lithium-ion battery electrical abuse stability assessment method. The electronic devices mentioned in the embodiment of the present application include but are not limited to mobile phones, tablet computers, computers, etc. The lithium-ion battery electrical abuse stability assessment method provided in the embodiment of the present application is described below using the electronic device as an example of the execution subject.

[0076] like Figure 1 As shown, the lithium-ion battery electrical abuse stability assessment method includes: step 110 and step 120.

[0077] Step 110, using a constant current to perform multiple overcharging cycles on the lithium-ion battery; wherein one overcharging cycle includes discharging the lithium-ion battery to a discharge cut-off voltage and charging the lithium-ion battery to an overcharging cut-off voltage.

[0078] In the embodiment of the present application, the lithium-ion battery cell can be overcharged by the battery charge and discharge tester. For example, the constant current value can be preset, and in an overcharge cycle, the lithium-ion battery cell can be charged with a constant current using the set constant current value, and the charging is stopped when the voltage of the lithium-ion battery reaches the overcharge cut-off voltage, and the lithium-ion battery cell is discharged with a constant current using the set constant current value, and the discharge is stopped when the voltage of the lithium-ion battery reaches the discharge cut-off voltage, thus completing an overcharge cycle.

[0079] In the embodiment of the present application, the number of overcharging cycles can be set according to actual conditions, for example, it can be 30 times, 50 times, 100 times, etc., and the embodiment of the present application does not limit this.

[0080] The discharge cut-off voltage refers to the lowest voltage limit set during the battery discharge process. When the battery voltage drops to this set value, the discharge should be stopped to avoid over-discharge of the battery. The discharge cut-off voltage can be determined based on the stability of the battery material and the discharge characteristics of the battery, or analyzed and determined by the discharge curve of the battery.

[0081] The charge cut-off voltage refers to the maximum voltage limit set during the battery charging process. When the battery voltage reaches this set value, the charger will stop charging or switch to trickle charging mode to prevent the battery from overcharging. The setting of the charge cut-off voltage is usually based on the stability of the battery positive electrode material and the safety of the battery design. Different battery chemistries and designs will have different charge cut-off voltages. For example, the location of the oxidation peak and the reduction peak can be determined by cyclic voltammetry scanning to determine the appropriate charge cut-off voltage; different charge cut-off voltages can also be preset through actual testing to observe the changes in battery capacity and then adjust to the optimal charge cut-off voltage.

[0082] In the embodiment of the present application, the overcharge cut-off voltage is slightly greater than the charge cut-off voltage to implement an overcharge test on the lithium-ion battery. For example, when determining the charge cut-off voltage, a value greater than the charge cut-off voltage can be set as the overcharge cut-off voltage.

[0083] In the embodiment of the present application, the voltage is selected as the overcharge cutoff condition for multiple overcharge cycles of the lithium-ion battery because the voltage change is more sensitive to the change of the battery power when the battery cell is in an overcharge state. Figure 2-5 As shown, in Figure 2 The lithium iron phosphate battery cell 1 is in the extreme overcharge stage I: charging to the voltage of 4.015V, 100.3% SOC, there is no temperature rise on the side of the cell during the process, and the cell does not change or have a temperature rise; overcharge stage II: the cell is charged to 111.2% SOC, the voltage reaches 4.700V, the negative electrode valve ruptures and sprays liquid, and the center of the side is 38.7℃; overcharge stage III: 188.6% SOC: voltage 11.5V, the positive pole explosion-proof valve starts to smoke, 189.8% SOC: voltage 19.244V, the negative pole explosion-proof valve starts to smoke, and the center of the side is 127.3℃. Figure 3 The relationship between the change rate of the voltage of cell 1 and cell 2 with the battery capacity and SOC, combined with Figure 3 It can be seen that the voltage of cell 1 and cell 2 increases slightly in the early stage of overcharging, and the SOC state does not change much. The voltage is better than the SOC to trigger the thermal runaway risk prediction. It is more reasonable to use the voltage as the end point for the overcharging of lithium iron phosphate cells. Figure 4The cell 1 of the medium ternary lithium battery is in the extreme overcharge stage I: charged to a voltage of 4.785V, 111.0% SOC, with no temperature rise on the side of the cell during the process, and the cell has no change or temperature rise; overcharge stage II: the cell is charged to 115.0% SOC, the voltage reaches 5.311V, the negative valve ruptures and liquid sprays, and the center of the side is 22.2℃; overcharge stage III: 155.2% SOC: voltage 5.196V, smoke begins to come out of the positive explosion-proof valve, and the center of the side is 83.8℃; continue charging to failure at 204% SOC: voltage 5.828V, and the center of the side is 116.8℃. Figure 5 It is the relationship between the change rate of the voltage of cell 1 and cell 2 with the battery capacity and SOC.

[0084] according to Figure 2-5 It can be seen that lithium iron phosphate batteries and ternary lithium batteries show different voltage and temperature behaviors under extreme overcharge conditions; lithium iron phosphate overcharge has a voltage platform stage: when overcharging continues, the voltage remains relatively stable between 4.5 and 5V. This may be because the chemical reaction inside the battery has reached a certain equilibrium state. Although lithium ions continue to be forced into the negative electrode, the rate of the electrochemical reaction may have slowed down; the increase in voltage and temperature of lithium iron phosphate batteries during overcharge is relatively slow, while the changes in voltage and temperature of ternary lithium batteries during overcharge are more drastic. This shows that in terms of safety, lithium iron phosphate batteries may have better stability, while ternary lithium batteries may be more prone to thermal runaway under overcharge conditions.

[0085] In some embodiments, a constant current may be used to perform an overcharge test on a fully charged lithium-ion battery to obtain a curve of voltage variation with battery capacity during the test;

[0086] The overcharge cut-off voltage is determined based on the curve of voltage change with battery capacity during the test.

[0087] In this embodiment, one or more lithium-ion batteries can be pre-selected as test objects, and the battery is in a fully charged state, that is, the SOC is 100%. A constant charging current is set to start charging, and the battery voltage changes with the battery capacity. In this process, the battery will be charged beyond its normal charging cut-off voltage.

[0088] During overcharge, the battery voltage rises as lithium ions are over-deintercalated. Typically, the battery voltage rises slowly as it charges, and then the voltage rises faster as the battery approaches its normal charge cutoff voltage.

[0089] In this embodiment, the voltage can be observed as a function of the battery capacity to find the inflection point where the voltage rises sharply and then changes slowly. This inflection point indicates that a side reaction has occurred inside the battery, such as electrolyte decomposition or changes in the structure of the positive electrode material, which are signs of overcharging. A safe overcharge cutoff voltage can be determined based on this inflection point, and this voltage should be less than or equal to the voltage value corresponding to the inflection point. Of course, the inflection point can also be determined by taking the derivative of the voltage as a function of the battery capacity curve. Figure 6 and Figure 7 As shown, Figure 6 and Figure 7 In an example, different lithium iron phosphate batteries are tested to obtain a curve of voltage variation with battery capacity. It can be seen that the voltage corresponding to the inflection point is 4.5V, and 4.5V can be used as the overcharge cut-off voltage of the lithium iron phosphate battery. Figure 8 and Fig. 9 In an example, different ternary lithium batteries are tested to obtain a curve of voltage versus battery capacity. It can be seen that there is no obvious inflection point in the graph.

[0090] In this embodiment, by using a constant current to perform an overcharge test on a fully charged lithium-ion battery, and determining the overcharge cut-off voltage based on a curve of voltage variation with battery capacity during the test, a clear safety threshold can be provided for the safe use and testing of lithium-ion batteries, and a reasonable overcharge voltage upper limit can be set based on the actual battery response to reduce excessive side reactions of the battery during the overcharge process, thereby improving the reliability of the battery overcharge stability assessment.

[0091] In some implementations, the constant current may be any current value, and may also be determined according to a current value corresponding to a rated capacity of the lithium-ion battery.

[0092] In some embodiments, before the lithium-ion battery is subjected to multiple overcharging cycles using a constant current, the method includes:

[0093] Use target current values ​​of different rates to perform overcharge tests on lithium-ion batteries, and obtain a curve showing the relationship between the rate of the target current value and the battery rupture valve voltage;

[0094] According to the relationship curve between the multiple of the target current value and the battery rupture valve voltage, it is determined that the lithium-ion battery is subjected to multiple overcharge cycles and several lithium-ion batteries of the same model are selected as test objects.

[0095] In this embodiment, the target current value may be a current value corresponding to the rated capacity of the lithium-ion battery. For example, the current value corresponding to the rated capacity of the lithium-ion battery may be determined as a reference charging current value. For example, the reference charging current value may be 1C, where 1C represents the current value corresponding to the rated capacity of the lithium-ion battery. Then, the multiplier is determined according to the reference charging current value. For example, it may be 1C, 3C, 5C, etc.

[0096] The battery is overcharged using target current values ​​at different rates. In each test, the battery is charged at a constant current until the battery voltage reaches the valve rupture voltage. When the battery voltage exceeds the charge cut-off voltage, continued charging will force lithium ions to continue to pass through the diaphragm from the positive electrode and accumulate on the surface of the negative electrode. When the gas generated by the side reaction causes the pressure to exceed the stress limit of the explosion-proof valve, a rupture will occur. The battery voltage corresponding to the rupture is the valve rupture voltage. During the test, the valve rupture voltage at each current rate is recorded, and a curve is drawn showing the relationship between the target current value rate and the battery valve rupture voltage. Analyze the curve to determine the effect of different current rates on the battery valve rupture voltage and select a suitable constant current value. For example, the current value corresponding to a lower rate and a smaller valve rupture voltage can be selected as the constant current value.

[0097] In one example, a battery with NCM (ternary lithium) and LFP (lithium iron phosphate) mixed material positive electrode was tested, and the ratio of the target current value and the battery rupture valve voltage U R The relationship curve is as follows Fig.10 As shown in the figure, for both batteries, the rupture voltage increases first and then decreases with the increase of charging rate. The rupture voltage reaches a peak at 1.5C, and the rupture voltage of LFP batteries is generally higher than that of NCM batteries. This also reflects that LFP batteries are safer under overcharge abuse conditions. In this example, the current value corresponding to a lower rate and a smaller rupture valve voltage can be selected as the constant current value. For example, As a constant current value used for multiple overcharge cycles of lithium-ion batteries.

[0098] In this embodiment, the lithium-ion battery is overcharged by using target current values ​​of different rates, and a relationship curve between the target current value rate and the battery rupture valve voltage is obtained accordingly. This can effectively determine a constant current value suitable for use when performing multiple overcharge cycles, and can provide a scientific current setting basis for the battery overcharge test, so that the test can fully challenge the safety limit of the battery without causing excessive side reactions of the battery due to excessive current, thereby losing the meaning of the test, thereby improving the reliability of the battery overcharge stability assessment.

[0099] Step 120: Evaluate the overcharge stability of the lithium-ion battery according to the discharge capacity of the lithium-ion battery before and after multiple overcharge cycles.

[0100] In an embodiment of the present application, before the lithium-ion battery is subjected to an overcharge cycle, the fully charged lithium-ion battery may be discharged to determine the discharge capacity of the lithium-ion battery. After the lithium-ion battery is subjected to multiple overcharge cycles, the fully charged lithium-ion battery may be discharged to determine the discharge capacity of the lithium-ion battery. Then, the overcharge stability of the lithium-ion battery may be evaluated based on the changes in the discharge capacity of the lithium-ion battery before multiple overcharge cycles and the discharge capacity of the lithium-ion battery after multiple overcharge cycles. For example, if the discharge capacity of the lithium-ion battery after multiple overcharge cycles decays less than the discharge capacity of the lithium-ion battery before multiple overcharge cycles, it means that the overcharge stability of the lithium-ion battery is good; if it decays more, it means that the overcharge stability of the lithium-ion battery is poor.

[0101] According to the lithium-ion battery electrical abuse stability evaluation method of the present application, the lithium-ion battery is subjected to multiple overcharge cycles by using a constant current; wherein one overcharge cycle includes discharging the lithium-ion battery to a discharge cut-off voltage and charging the lithium-ion battery to an overcharge cut-off voltage; the overcharge stability of the lithium-ion battery is evaluated based on the discharge capacity of the lithium-ion battery before the multiple overcharge cycles and the discharge capacity of the lithium-ion battery after the multiple overcharge cycles. The embodiment of the present application adopts voltage as the overcharge cut-off condition, which can reduce the side reactions caused by overcharging during the battery stability evaluation process, making the evaluation result more reliable, and the discharge capacity of the battery before and after multiple overcharge cycles is used for evaluation, which can reduce the influence of factors such as battery manufacturing process and use environment on the evaluation result, thereby improving the accuracy of the lithium-ion battery electrical abuse stability evaluation.

[0102] In some embodiments, the overcharge stability of the lithium-ion battery is evaluated according to the discharge capacity of the lithium-ion battery before multiple overcharge cycles and the discharge capacity of the lithium-ion battery after multiple overcharge cycles, including:

[0103] Calculating the capacity retention rate of the lithium-ion battery after multiple overcharge cycles based on the discharge capacity of the lithium-ion battery before multiple overcharge cycles and the discharge capacity of the lithium-ion battery after multiple overcharge cycles;

[0104] The overcharge stability of lithium-ion batteries was evaluated based on the capacity retention rate.

[0105] In this embodiment, the overcharge stability of the lithium-ion battery can be evaluated by using the capacity retention rate, wherein the capacity retention rate reflects the degree of performance degradation of the battery after the overcharge cycle. The capacity retention rate is the ratio of the discharge capacity of the lithium-ion battery after multiple overcharge cycles to the discharge capacity of the lithium-ion battery before multiple overcharge cycles. The greater the capacity retention rate, the better the overcharge stability of the battery. For example, the overcharge stability of the lithium-ion battery can be graded according to the capacity retention rate. If the capacity retention rate of the battery is above 95%, the overcharge stability of the battery is considered to be excellent; if the capacity retention rate of the battery is between 92%-95%, the overcharge stability of the battery is considered to be good; if the capacity retention rate of the battery is between 87%-92%, the overcharge stability of the battery is considered to be qualified; if the capacity retention rate of the battery is lower than 87%, the overcharge stability of the battery is considered to be unqualified.

[0106] In one example, for a fully charged lithium-ion battery cell with a rated capacity of 130Ah, it is placed in a room temperature environment for a preset time, wherein the room temperature may be 25°C, and the preset time may be 12 hours, 24 hours, etc., and then a constant current value is used, such as The battery was discharged at a constant current with a discharge cut-off voltage of 2.5V, and the discharge capacity of the battery was recorded as 130.468Ah. After the lithium-ion battery was overcharged 30 times, the fully charged lithium-ion battery was placed at room temperature for a preset time, and then a constant current value was used, such as The battery was discharged at a constant current with a discharge cut-off voltage of 2.5V, and the discharge capacity of the battery was recorded as 126.606Ah. The capacity retention rate of the battery was calculated to be 97.04%, which means that after 30 overcharge cycles, the capacity retention rate of the battery was still above 95%, indicating that the overcharge stability of the battery was good.

[0107] In this embodiment, the capacity retention rate directly reflects the degree of battery performance degradation after multiple overcharging cycles, and is a key indicator for evaluating the battery health status and predicting its remaining service life. The capacity retention rate is used as an evaluation indicator to improve the reliability of battery overcharging stability assessment.

[0108] In some embodiments, evaluating the overcharge stability of a lithium-ion battery according to the capacity retention rate comprises:

[0109] Calculate the extent of active material loss in lithium-ion batteries after multiple overcharge cycles;

[0110] The overcharge stability of lithium-ion batteries was evaluated based on the degree of active material loss and capacity retention.

[0111] In this embodiment, the overcharge stability of the lithium-ion battery can also be evaluated in combination with the degree of loss of active materials after multiple overcharge cycles. The degree of loss of active materials refers to the amount of active materials lost in the positive and negative electrodes of the battery (such as lithium metal oxides at the positive electrode, graphite or other materials at the negative electrode) due to chemical or physical reasons during battery use, charge and discharge cycles, overcharge, overdischarge or storage. This loss usually leads to a decrease in battery capacity, an increase in internal resistance, and a deterioration in cycle stability, which ultimately affects the overall performance and service life of the battery.

[0112] For example, the overcharge stability of lithium-ion batteries can be graded according to the capacity retention rate and the degree of active material loss. If the capacity retention rate of the battery is above 95% and the degree of active material loss is within the normal range, the overcharge stability of the battery is considered to be excellent; if the capacity retention rate of the battery is between 92% and 95%, the degree of active material loss has decreased but is still within the normal range, the overcharge stability of the battery is considered to be good; if the capacity retention rate of the battery is between 87% and 92%, the degree of active material loss has significantly decreased but is still within the normal range, the overcharge stability of the battery is considered to be qualified; if the capacity retention rate of the battery is lower than 87%, or the degree of active material loss exceeds the normal range, the overcharge stability of the battery is considered to be unqualified.

[0113] In this embodiment, the extent of active material loss in a lithium-ion battery after multiple overcharge cycles can be determined in any manner. For example, the loss of active material can be estimated by measuring the weight change of the lithium-ion battery before and after overcharge; the crystal structure change of the battery material can be analyzed by X-ray diffraction to evaluate the loss of active material; the surface morphology and structural changes of the battery material can be observed by scanning electron microscopy to evaluate the loss of active material; the change of the internal impedance of the battery can be analyzed by electrochemical impedance spectroscopy to indirectly evaluate the loss of active material, etc.

[0114] In this embodiment, the calculation of the degree of active material loss can reveal the tolerance of the battery under extreme conditions. Combined with the capacity retention rate, this indicator reflects the ability of the battery to maintain its initial discharge capacity after an overcharge cycle, and further provides quantitative data on battery performance degradation. This evaluation method can not only be used for laboratory research, but also for battery production and quality control, and has important practical value for improving the stability and safety of lithium-ion batteries for electric vehicles.

[0115] In some embodiments, calculating the extent of active material loss of a lithium-ion battery after multiple overcharge cycles includes:

[0116] A first differential voltage curve is obtained by differentiating a first relationship curve between the voltage and capacity of the lithium-ion battery before multiple overcharging cycles; a second differential voltage curve is obtained by differentiating a second relationship curve between the voltage and capacity of the lithium-ion battery after multiple overcharging cycles;

[0117] Calculating the positive electrode active material loss, the negative electrode active material loss and the active lithium ion loss of the lithium ion battery after multiple overcharge cycles according to the first differential voltage curve and the second differential voltage curve;

[0118] The degree of active material loss is calculated based on the positive electrode active material loss, negative electrode active material loss and active lithium ion loss.

[0119] In this embodiment, before the overcharge cycle, the lithium-ion battery is charged and discharged, and the voltage V and capacity Q data are recorded to draw a first relationship curve. After the overcharge cycle, the charge and discharge test is performed again, and the voltage and capacity data are recorded to draw a second relationship curve. The first relationship curve is differentiated to obtain a first differential voltage curve (dV / dQ). The second relationship curve is differentiated to obtain a second differential voltage curve (dV / dQ).

[0120] The peaks on the differential voltage curve usually correspond to phase changes or electrochemical processes during the battery's charge and discharge process. Compare the first differential voltage curve and the second differential voltage curve to observe changes in the peak values, which can indicate changes in the battery material structure and electrochemical performance. By comparing the changes in the differential voltage peak values ​​of the positive electrode material before and after the overcharge cycle, the loss of the positive electrode active material can be estimated. By comparing the changes in the differential voltage peak values ​​of the negative electrode material before and after the overcharge cycle, the loss of the negative electrode active material can be estimated. The loss of active lithium ions can be estimated by the changes in the differential voltage peak values ​​of the positive and negative electrode materials before and after the overcharge cycle.

[0121] According to one embodiment of the present application, according to the formula

[0122]

[0123] Calculate the loss of positive electrode active materials, negative electrode active materials and active lithium ion loss;

[0124] Among them, K LAM Indicates the loss of positive electrode active material, K' LAM Indicates the loss of negative electrode active material, K LI+ represents the loss of active lithium ions, Q 1,0 represents the distance between the positive peaks of the first differential voltage curve, Q 1,n represents the distance between the positive peaks of the second differential voltage curve, Q 2,0 represents the distance between the negative peaks of the first differential voltage curve, Q 1,nrepresents the distance between the negative peaks of the second differential voltage curve, Q 3,0 represents the distance between the positive peak and the negative peak of the first differential voltage curve, Q 3,n Represents the distance between the positive peak and the negative peak of the second differential voltage curve.

[0125] In one example, a ternary lithium battery and a lithium iron phosphate battery are subjected to multiple overcharge cycles, and the voltage-capacity curves obtained before and after the multiple overcharge cycles are differentiated to remove the abnormal points caused by the sampling error of the equipment, and the differential voltage curve of the ternary lithium battery is obtained as follows: Fig.11 As shown, and the differential voltage curve of the lithium iron phosphate battery is as follows Fig.12 As shown. Fig.11 and Fig.12 As shown. Peaks ①, ②, ③, and ④ are contributed by the negative electrode, and peaks ⑤ and ⑥ are contributed by the positive electrode. Therefore, the distance between peaks ⑤ and ⑥ can be used to represent the distance between positive peaks; the distance between peaks ① and ④ can be used to represent the distance between negative peaks; and the distance between peaks ④ and ⑥ can be used to represent the distance between positive and negative peaks.

[0126] In this embodiment, by differentiating the voltage-capacity curve of the battery, the differential voltage curve obtained can reveal the sensitivity of the voltage to the capacity change of the battery during the charge and discharge process, thereby reflecting the dynamic characteristics of the electrochemical reaction inside the battery. Before and after the overcharge cycle, the electrochemical behavior of the battery may change. These changes are manifested as changes in peak values, valley values ​​and their areas on the differential voltage curve. The changes in these characteristic points are directly related to the loss of positive and negative active materials and active lithium ions. By comparing the differential voltage curves before and after the cycle, the degree of loss of positive and negative active materials and the reduction of active lithium ions can be accurately analyzed.

[0127] To further illustrate the implementation process of the lithium-ion battery electrical abuse stability assessment method of the embodiment of the present application, the present application is introduced through specific examples.

[0128] In this example, the following steps are included:

[0129] Step 1: Prepare a lithium-ion battery cell with a rated capacity of 130Ah and place it at room temperature of 25°C for 24 hours.

[0130] Step 2: Use a fully charged battery The current is continuously charged until the battery valve ruptures, leaks, or eventually thermally runs away. The overcharge boundary under continuous overcharging conditions is preliminarily explored, and the total charging amount during the overcharging period is counted. The overcharge capacity value of the battery under this continuous overcharging condition is obtained as 103.013Ah. By observing the voltage change curve with the battery capacity, the small overcharge cutoff voltage is determined to be 4.5V.

[0131] Step 3: Prepare a lithium-ion battery cell with a rated capacity of 130Ah and place it at room temperature of 25°C for 24 hours.

[0132] Step 4: Use a battery charge and discharge tester to The battery was discharged at a constant current with a cut-off voltage of 2.5V, and the discharge capacity of the battery was recorded to be 130.468Ah.

[0133] Step 5: Replace the battery The overcharge cut-off voltage is 4.5V, and the battery is in a slightly overcharged state. The battery is discharged at a constant current with a discharge cut-off voltage of 2.5V, completing an overcharge cycle.

[0134] Step 6: Repeat step 5 and perform 30 overcharge cycles.

[0135] Step 7: Repeat The battery was discharged at a constant current with a cut-off voltage of 2.5V, and the discharge capacity of the battery was recorded to be 126.606Ah.

[0136] Step 8: The calculated capacity retention rate of the battery is 97.04%, which means that after 30 overcharge cycles, the capacity retention rate of the battery is still above 95%, indicating that the battery has good overcharge stability.

[0137] Step 9: Use the dV / dQ curve to calculate the active material loss degree of 4.8% to further evaluate the overcharge stability of the battery.

[0138] Step 10: Evaluate the overcharge stability of the battery based on the test results. If the battery capacity retention rate is above 95%, and the dV / dQ curve, active material loss degree and other indicators are within the normal range, the battery overcharge stability is considered to be excellent; if the battery capacity retention rate is between 92% and 95%, the dV / dQ curve, active material loss degree and other indicators have decreased, but are still within the normal range, the battery overcharge stability is considered to be good; if the battery capacity retention rate is between 87% and 92%, the dV / dQ curve, active material loss degree and other indicators have significantly decreased, but are still within the normal range, the battery overcharge stability is considered to be qualified; if the battery capacity retention rate is lower than 87%, or the dV / dQ curve, active material loss degree and other indicators are beyond the normal range, the battery overcharge stability is considered to be unqualified.

[0139] Step 11: During the entire test process, if the battery has safety problems such as fire, explosion, leakage, open circuit, short circuit, etc., the test is terminated immediately and the overcharge stability of the battery is determined to be unqualified. The above is a specific example of the present invention. Through this embodiment, the performance of lithium-ion battery cells under overcharge conditions can be effectively evaluated, thereby improving the safety of electric vehicles.

[0140] In order to further evaluate the effectiveness of the lithium-ion battery electrical abuse stability assessment method of the embodiment of the present application, a plurality of lithium-ion batteries with different rated capacities were selected for assessment, and the capacity was used as the overcharge cutoff condition for comparison. The results are shown in the following table.

[0141] Example Rated capacity / Ah Overcharge cut-off voltage / V Cycle times / n Capacity retention rate % Active substance loss% Example 1 304 4.5 30 97.04％ 4.8％ Example 2 130 4.5 30 94.18％ 5.8％ Example 3 230 4.5 30 98.96％ 4.6％ Comparative Example 4 130 105% SOC 9 / /

[0142] In Comparative Example 4, after 9 overcharge cycles, the lithium-ion battery caught fire, so the test was terminated. The capacity retention rate of these examples varies with the number of cycles as shown in the following table.

[0143]

[0144] The lithium-ion battery electrical abuse stability assessment method provided in the embodiment of the present application can be executed by a lithium-ion battery electrical abuse stability assessment device. In the embodiment of the present application, the lithium-ion battery electrical abuse stability assessment method is executed by a lithium-ion battery electrical abuse stability assessment device as an example to illustrate the lithium-ion battery electrical abuse stability assessment method provided in the embodiment of the present application.

[0145] The embodiment of the present application also provides a lithium-ion battery electrical abuse stability assessment device.

[0146] like Fig.13 As shown, the lithium-ion battery electrical abuse stability evaluation device comprises:

[0147] The overcharge cycle module 1310 is used to perform multiple overcharge cycles on the lithium-ion battery using a constant current; wherein one overcharge cycle includes discharging the lithium-ion battery to a discharge cut-off voltage and charging the lithium-ion battery to an overcharge cut-off voltage;

[0148] The evaluation module 1320 is used to evaluate the overcharge stability of the lithium-ion battery according to the discharge capacity of the lithium-ion battery before multiple overcharge cycles and the discharge capacity of the lithium-ion battery after multiple overcharge cycles.

[0149] According to the lithium-ion battery abuse stability assessment device of the present application, the lithium-ion battery is pulse charged; the pulse charging includes multiple executions of the alternating process of charging and standing still; the equivalent DC internal resistance of the lithium-ion battery is calculated according to the voltage change of the lithium-ion battery during the alternating process of charging and standing still, and the pulse current value used in the pulse charging; and whether the lithium-ion battery has lithium plating is analyzed according to the change trend of the equivalent DC internal resistance over time. The embodiment of the present application makes the negative electrode of the lithium-ion battery and the lithium ions in the electrolyte in a better equilibrium state by performing multiple alternations of charging and standing still during the pulse charging of the lithium-ion battery. By calculating the equivalent DC internal resistance, the change of the internal impedance of the battery can be quantified, and the internal resistance abnormality caused by lithium deposition can be sensitively captured, so as to determine whether lithium plating has occurred, without the need to disassemble a large number of batteries, and can realize online lithium plating detection, timely discover potential lithium plating problems, and improve the efficiency of lithium plating detection.

[0150] In some embodiments, the evaluation module 1320 is further configured to:

[0151] Calculating the capacity retention rate of the lithium-ion battery after multiple overcharge cycles based on the discharge capacity of the lithium-ion battery before multiple overcharge cycles and the discharge capacity of the lithium-ion battery after multiple overcharge cycles;

[0152] The overcharge stability of lithium-ion batteries was evaluated based on the capacity retention rate.

[0153] In this embodiment, the capacity retention rate directly reflects the degree of battery performance degradation after multiple overcharging cycles, and is a key indicator for evaluating the battery health status and predicting its remaining service life. The capacity retention rate is used as an evaluation indicator to improve the reliability of battery overcharging stability assessment.

[0154] In some embodiments, the evaluation module 1320 is further configured to:

[0155] Calculate the extent of active material loss in lithium-ion batteries after multiple overcharge cycles;

[0156] The overcharge stability of lithium-ion batteries was evaluated based on the degree of active material loss and capacity retention.

[0157] In this embodiment, the calculation of the degree of active material loss can reveal the tolerance of the battery under extreme conditions. Combined with the capacity retention rate, this indicator reflects the ability of the battery to maintain its initial discharge capacity after an overcharge cycle, and further provides quantitative data on battery performance degradation. This evaluation method can not only be used for laboratory research, but also for battery production and quality control, and has important practical value for improving the stability and safety of lithium-ion batteries for electric vehicles.

[0158] In some embodiments, the evaluation module 1320 is further configured to:

[0159] A first differential voltage curve is obtained by differentiating a first relationship curve between the voltage and capacity of the lithium-ion battery before multiple overcharging cycles; a second differential voltage curve is obtained by differentiating a second relationship curve between the voltage and capacity of the lithium-ion battery after multiple overcharging cycles;

[0160] Calculating the positive electrode active material loss, the negative electrode active material loss and the active lithium ion loss of the lithium ion battery after multiple overcharge cycles according to the first differential voltage curve and the second differential voltage curve;

[0161] The degree of active material loss is calculated based on the positive electrode active material loss, negative electrode active material loss and active lithium ion loss.

[0162] In some embodiments, the evaluation module 1320 is further configured to:

[0163] According to the formula

[0164]

[0165] Calculate the loss of positive electrode active materials, negative electrode active materials and active lithium ion loss;

[0166] Among them, K LAM Indicates the loss of positive electrode active material, K' LAM Indicates the loss of negative electrode active material, K LI+ represents the loss of active lithium ions, Q 1,0 represents the distance between the positive peaks of the first differential voltage curve, Q 1,n represents the distance between the positive peaks of the second differential voltage curve, Q 2,0 represents the distance between the negative peaks of the first differential voltage curve, Q 1,n represents the distance between the negative peaks of the second differential voltage curve, Q 3,0 represents the distance between the positive peak and the negative peak of the first differential voltage curve, Q 3,n Represents the distance between the positive peak and the negative peak of the second differential voltage curve.

[0167] In some embodiments, the overcharge cycle module 1310 is further configured to:

[0168] Use target current values ​​of different rates to perform overcharge tests on lithium-ion batteries, and obtain a curve showing the relationship between the rate of the target current value and the battery rupture valve voltage;

[0169] The constant current value used for multiple overcharge cycles of the lithium-ion battery is determined based on the relationship curve between the target current value ratio and the battery rupture valve voltage.

[0170] In some embodiments, the overcharge cycle module 1310 is further configured to:

[0171] Use constant current to perform overcharge test on fully charged lithium-ion batteries, and obtain the curve of voltage change with battery capacity during the test;

[0172] The overcharge cut-off voltage is determined based on the curve of voltage change with battery capacity during the test.

[0173] The lithium-ion battery electrical abuse stability assessment device in the embodiment of the present application can be an electronic device, or a component in an electronic device, such as an integrated circuit or a chip. The electronic device can be a terminal, or it can be other devices other than a terminal. Exemplarily, the electronic device can be a mobile phone, a tablet computer, a laptop computer, a PDA, a vehicle-mounted electronic device, a mobile Internet device (Mobile Internet Device, MID), an augmented reality (augmented reality, AR) / virtual reality (virtual reality, VR) device, a robot, a wearable device, an ultra-mobile personal computer (ultra-mobile personal computer, UMPC), a netbook or a personal digital assistant (personal digital assistant, PDA), etc., and can also be a server, a network attached storage (Network Attached Storage, NAS), a personal computer (personal computer, PC), a television (television, TV), a teller machine or a self-service machine, etc., and the embodiment of the present application is not specifically limited.

[0174] The lithium-ion battery abuse stability assessment device in the embodiment of the present application may be a device having an operating system. The operating system may be a Microsoft (Windows) operating system, an Android (Android) operating system, an IOS operating system, or other possible operating systems, which are not specifically limited in the embodiment of the present application.

[0175] In some embodiments, Fig.14 As shown, an embodiment of the present application further provides an electronic device 1400, including a processor 1401, a memory 1402, and a computer program stored in the memory 1402 and executable on the processor 1401. When the program is executed by the processor 1401, each process of the above-mentioned lithium-ion battery electrical abuse stability assessment method embodiment is implemented, and the same technical effect can be achieved. To avoid repetition, it will not be described here.

[0176] The embodiment of the present application also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the various processes of the above-mentioned lithium-ion battery electrical abuse stability assessment method embodiment are implemented, and the same technical effect can be achieved. To avoid repetition, it will not be repeated here.

[0177] The processor is the processor in the electronic device in the above embodiment. The readable storage medium includes a computer readable storage medium, such as a computer read-only memory ROM, a random access memory RAM, a magnetic disk or an optical disk.

[0178] An embodiment of the present application also provides a computer program product, including a computer program, which implements the above-mentioned lithium-ion battery electrical abuse stability assessment method when executed by a processor.

[0179] The processor is the processor in the electronic device in the above embodiment. The readable storage medium includes a computer readable storage medium, such as a computer read-only memory ROM, a random access memory RAM, a magnetic disk or an optical disk.

[0180] The embodiment of the present application further provides a chip, which includes a processor and a communication interface, the communication interface and the processor are coupled, and the processor is used to run programs or instructions to implement the various processes of the above-mentioned lithium-ion battery electrical abuse stability assessment method embodiment, and can achieve the same technical effect. To avoid repetition, it will not be repeated here.

[0181] It should be understood that the chip mentioned in the embodiments of the present application can also be called a system-level chip, a system chip, a chip system or a system-on-chip chip, etc.

[0182] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0183] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a computer software product, which is stored in a storage medium (such as ROM / RAM, a disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0184] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

[0185] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0186] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for evaluating the stability of lithium-ion battery electrical abuse, It is characterized in that include: The lithium-ion battery is subjected to multiple overcharging cycles using a constant current; wherein one overcharging cycle includes discharging the lithium-ion battery to a discharge cut-off voltage and charging the lithium-ion battery to an overcharging cut-off voltage; The overcharge stability of the lithium ion battery is evaluated according to the discharge capacity of the lithium ion battery before multiple overcharge cycles and the discharge capacity of the lithium ion battery after multiple overcharge cycles.

2. The method according to claim 1, It is characterized in that The overcharge stability of the lithium ion battery is evaluated according to the discharge capacity of the lithium ion battery before multiple overcharge cycles and the discharge capacity of the lithium ion battery after multiple overcharge cycles, comprising: Calculating the capacity retention rate of the lithium ion battery after multiple overcharge cycles according to the discharge capacity of the lithium ion battery before multiple overcharge cycles and the discharge capacity of the lithium ion battery after multiple overcharge cycles; The overcharge stability of the lithium ion battery was evaluated based on the capacity retention rate.

3. The method according to claim 2, It is characterized in that The step of evaluating the overcharge stability of the lithium-ion battery according to the capacity retention rate comprises: Calculating the extent of active material loss of the lithium-ion battery after multiple overcharge cycles; The overcharge stability of the lithium ion battery was evaluated based on the active material loss degree and the capacity retention rate.

4. The method according to claim 3, It is characterized in that The calculating the degree of loss of active material of the lithium-ion battery after multiple overcharge cycles includes: Differentiating a first relationship curve between the voltage and capacity of the lithium-ion battery before multiple overcharging cycles to obtain a first differential voltage curve; Differentiating a second relationship curve between the voltage and capacity of the lithium-ion battery after multiple overcharging cycles to obtain a second differential voltage curve; Calculating respectively the positive electrode active material loss, the negative electrode active material loss and the active lithium ion loss of the lithium ion battery after multiple overcharge cycles according to the first differential voltage curve and the second differential voltage curve; The active material loss degree is calculated according to the positive electrode active material loss, the negative electrode active material loss and the active lithium ion loss.

5. The method according to claim 4, It is characterized in that According to the formula Calculate the loss of positive electrode active materials, negative electrode active materials and active lithium ion loss; Among them, K LAM Indicates the loss of positive electrode active material, K' LAM Indicates the loss of negative electrode active material, K LI+ represents the loss of active lithium ions, Q 1,0 represents the distance between the positive peaks of the first differential voltage curve, Q 1,n represents the distance between the positive peaks of the second differential voltage curve, Q 2,0 represents the distance between the negative peaks of the first differential voltage curve, Q 1,n represents the distance between the negative peaks of the second differential voltage curve, Q 3,0 represents the distance between the positive peak and the negative peak of the first differential voltage curve, Q 3,n Represents the distance between the positive peak and the negative peak of the second differential voltage curve.

6. The method according to claim 1, It is characterized in that Before using constant current to overcharge lithium-ion batteries for multiple cycles, including: Use target current values ​​of different rates to perform overcharge tests on lithium-ion batteries, and obtain a curve showing the relationship between the rate of the target current value and the battery rupture valve voltage; The constant current value used for performing multiple overcharging cycles on the lithium-ion battery is determined according to the relationship curve between the multiple of the target current value and the battery rupture valve voltage.

7. The method according to claim 1, It is characterized in that Before using constant current to overcharge lithium-ion batteries for multiple cycles, including: Use constant current to perform overcharge test on fully charged lithium-ion batteries, and obtain the curve of voltage change with battery capacity during the test; The overcharge cut-off voltage is determined according to a curve of voltage variation with battery capacity during the test process.

8. A lithium-ion battery abuse stability assessment device, It is characterized in that include: An overcharge cycle module, used for performing multiple overcharge cycles on the lithium-ion battery using a constant current; wherein one overcharge cycle includes discharging the lithium-ion battery to a discharge cut-off voltage and charging the lithium-ion battery to an overcharge cut-off voltage; The evaluation module is used to evaluate the overcharge stability of the lithium ion battery according to the discharge capacity of the lithium ion battery before multiple overcharge cycles and the discharge capacity of the lithium ion battery after multiple overcharge cycles.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, It is characterized in that When the processor executes the program, the method according to any one of claims 1 to 7 is implemented.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, It is characterized in that When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

Images