Attenuation identification method and device applied to battery and medium

Abstract

The invention relates to the technical field of batteries, in particular to an attenuation identification method and device applied to a battery and a medium, and the method comprises the steps: collecting a first average charging voltage of the battery in a plurality of first cycle processes which are used for representing a charging process and a discharging process of the battery; the first average charging voltage is used for representing the average voltage of the positive electrode and the negative electrode of the battery in the charging process, and charging is carried out at preset power in the charging process; acquiring the change trend of the first average charging voltage along with the increase of the cycle index; and judging the attenuation risk of the battery according to the change trend. Besides, according to the technology, through analysis of the voltage trend, the battery maintenance strategy is accurately optimized, the service life of the battery is prolonged, and the system safety is improved.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and specifically provides a method, device and medium for identifying attenuation of a battery. Background Art

[0002] With the empowerment of the electric industry, lithium iron phosphate batteries are being used in more and more fields, such as electric vehicles and energy storage, due to their high battery stability and long cycle life.

[0003] However, lithium iron phosphate batteries are also accompanied by a special phenomenon, namely, the accelerated attenuation of lithium iron phosphate batteries. At this time, the power attenuation rate of lithium iron phosphate batteries will rise sharply, greatly affecting the life of lithium iron phosphate batteries. Therefore, how to know in advance that lithium iron phosphate batteries will enter the accelerated attenuation stage is extremely important for the maintenance of lithium iron phosphate batteries.

[0004] Accordingly, the art needs a new accelerated attenuation identification method for lithium iron phosphate batteries to solve the above problems. Summary of the invention

[0005] In order to overcome the above-mentioned defects, the present invention is proposed to provide a solution or at least partially solve the problem in the prior art that the accelerated decay of lithium iron phosphate batteries is difficult to identify.

[0006] In a first aspect, the present invention provides an attenuation identification method for a battery, the method comprising: collecting a first average charging voltage of the battery during multiple first cycle processes, wherein the first cycle process is used to characterize a charging process and a discharging process of the battery, and the first average charging voltage is used to characterize the average voltage of the positive and negative electrodes of the battery during the charging process, and charging at a preset power during the charging process; obtaining a change trend of the first average charging voltage as the number of cycles increases; and judging the attenuation risk of the battery based on the change trend.

[0007] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, if the change trend is a growth state, it is at least determined that the attenuation risk of the battery is high at this time, wherein the growth state is used to indicate that the rate of change of the first average charging voltage exceeds a preset first amplitude threshold.

[0008] As an alternative or supplement to the above solution, in a method according to an embodiment of the present invention, as the number of cycles increases, if the change trend is a non-increasing state, it is at least determined that the attenuation risk of the battery is low at this time.

[0009] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, based on the first average charging voltage within a preset cycle number interval, the change rate of the first average charging voltage is calculated to obtain the average voltage change rate, wherein the average voltage change rate is used to characterize the change trend of the first average charging voltage; if the average voltage change rate is greater than the first amplitude threshold, the change trend is in a growth state.

[0010] As an alternative or supplement to the above solution, in a method according to an embodiment of the present invention, the accuracy of the first average charging voltage is at least 0.005V.

[0011] As an alternative or supplement to the above solution, in a method according to an embodiment of the present invention, the size of the cycle number interval is proportional to the battery capacity.

[0012] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the voltage change rate within a preset cycle number interval is calculated to obtain an average voltage change rate, including: obtaining a first average charging voltage within a preset cycle number interval; calculating the voltage change rate between every two consecutive first average charging voltages and averaging the voltage change rate to obtain an average voltage change rate; and / or, obtaining the first average charging voltage within a preset cycle number interval; removing outlier first average charging voltages within a preset cycle number interval; calculating the voltage change rate between every two consecutive first average charging voltages and averaging the voltage change rate to obtain an average voltage change rate; and / or, obtaining the first average charging voltage within a preset cycle number interval; fitting based on the first average charging voltage to obtain a fitting curve; obtaining the average voltage change rate based on the fitting curve.

[0013] As an alternative or supplement to the above solution, in a method according to an embodiment of the present invention, the type of the lithium iron phosphate battery is a square shell battery or a soft pack battery.

[0014] As an alternative or supplement to the above solution, in a method according to an embodiment of the present invention, the battery is a lithium iron phosphate battery.

[0015] As an alternative or supplement to the above solution, in a method according to an embodiment of the present invention, charging is performed at a preset ambient temperature during the charging process.

[0016] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, during each first cycle, the battery is charged from a relatively low state of charge to a higher state of charge, and discharged from a higher state of charge to a lower state of charge, wherein the power level during the charging and discharging process remains consistent.

[0017] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the battery is charged from a relatively low state of charge to a higher state of charge, and discharged from a higher state of charge to a lower state of charge, including: during the charging process, the battery is charged from a first preset power to a higher second preset power, and during the discharging process, the battery is discharged from the second preset power to the first preset power.

[0018] In a second aspect, a control device is provided, which includes a processor and a storage device, wherein the storage device is suitable for storing multiple computer programs, and the computer programs are suitable for being loaded and run by the processor to execute the attenuation identification method applied to a battery as described in any one of the technical solutions of the above-mentioned attenuation identification method applied to a battery.

[0019] In a third aspect, a computer-readable storage medium is provided, wherein a plurality of computer programs are stored in the computer-readable storage medium, wherein the computer programs are suitable for being loaded and run by a processor to execute the attenuation identification method applied to a battery as described in any one of the technical solutions of the attenuation identification method applied to a battery.

[0020] The above one or more technical solutions of the present invention have at least one or more of the following Beneficial effects:

[0021] In the technical solution of the present invention, by collecting the first average charging voltage of the battery in each cycle and analyzing its changing trend with the increase of the number of cycles in real time, when the voltage trend is increasing, it can timely identify that the battery has entered the decay stage, thus realizing early warning of the battery health status. In addition, by analyzing the voltage trend, the technology accurately optimizes the battery maintenance strategy, prolongs the battery life and improves the system safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In addition, similar numbers in the figures are used to represent similar components, among which:

[0023] Figure 1 is a schematic flow chart of main steps of a method for attenuation identification applied to a battery according to an embodiment of the present invention;

[0024] Figure 2 This is a graph showing the relationship between the first average charging voltage and the number of cycles of a 150Ah lithium iron phosphate battery;

[0025] Figure 3 yes Figure 2 A partial enlarged schematic diagram of

[0026] Figure 4 yes Figure 2 Physical picture of the negative electrode and diaphragm interface of lithium iron phosphate battery after the end of the number of cycles shown in the figure;

[0027] Figure 5 This is a graph showing the relationship between the first average charging voltage and the number of cycles of a 50Ah lithium iron phosphate battery;

[0028] Figure 6 yes Figure 5 Physical picture of the negative electrode and diaphragm interface of the lithium iron phosphate battery after the end of the illustrated cycle number. DETAILED DESCRIPTION

[0029] Some embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0030] In the description of the present invention, "module" and "processor" may include hardware, software or a combination of the two. A module may include hardware circuits, various suitable sensors, communication ports, and memories, and may also include software parts, such as computer programs, or a combination of software and hardware. The processor may be a central processing unit, a microprocessor, an image processor, a digital signal processor, or any other suitable processor. The processor has data and / or signal processing functions. The processor may be implemented in software, hardware, or a combination of the two. Non-temporary computer-readable storage media include any suitable medium that can store computer programs, such as magnetic disks, hard disks, optical disks, flash memory, read-only memory, random access memory, etc. The term "A and / or B" means all possible combinations of A and B, such as only A, only B, or A and B. The term "at least one A or B" or "at least one of A and B" has a similar meaning to "A and / or B", and may include only A, only B, or A and B. The singular terms "one" and "the" may also include plural forms.

[0031] Here, some terms related to the present invention are explained first.

[0032] Cycle: A single cycle includes the complete charging and discharging process of a lithium-ion battery. A complete charging and discharging process combined is a single cycle. Sometimes the cycle is also called a "circle". The 200th circle is the 200th cycle of the battery.

[0033] Lithium deposition: refers to the phenomenon of uneven deposition of lithium metal on the negative electrode surface during the charging process of lithium-ion batteries. This usually occurs when the battery is overcharged or aged, and the lithium ions cannot be fully embedded in the negative electrode material, resulting in the accumulation of metallic lithium on the surface. Lithium deposition increases the internal resistance of the battery, causes capacity decay, and may cause safety hazards such as short circuit or thermal runaway, so it is considered a key factor in the degradation of battery performance.

[0034] The accelerated attenuation of lithium-ion batteries is largely due to lithium plating. Lithium plating causes uneven deposition of lithium metal on the negative electrode surface, increasing the internal resistance and polarization effect of the battery, which in turn hinders the battery's charge and discharge process, ultimately accelerating the decline in battery capacity and performance degradation, and shortening the service life of lithium-ion batteries. Therefore, identifying the severity of lithium plating can determine the life of lithium-ion batteries.

[0035] In this embodiment, in order to facilitate the explanation of the present technology, the subsequent lithium-ion battery is explained by taking a lithium iron phosphate battery as an example. The lithium-ion battery can also be a ternary lithium battery, a lithium cobalt oxide battery, a lithium manganese oxide battery or a lithium titanate battery and other lithium-ion batteries, which are not limited here.

[0036] See attached Figure 1 , Figure 1 FIG. 1 is a flow chart showing the main steps of a method for identifying battery attenuation according to an embodiment of the present invention. Figure 1 As shown, the attenuation identification method applied to a battery in the embodiment of the present invention mainly includes the following steps S10 to S30.

[0037] Step S10: collecting a first average charging voltage of the lithium iron phosphate battery during a plurality of first cycles.

[0038] In this embodiment, the first cycle process specifically refers to a cycle process that satisfies the charging power to be a preset power. The preset power can be a power value, or a preset power range, which is not limited here. The first cycle process includes a charging process and a discharging process. Among all the cycle processes of the lithium iron phosphate battery, only the cycle process in which the charging process at least satisfies the charging power less than the preset power error range is called the first cycle process.

[0039] For example, during the charging process, the battery is charged at a preset ambient temperature, where the preset ambient temperature can be a temperature value or a preset temperature range, which is not limited here.

[0040] The reason for limiting the charging power is that the charging power directly affects the average charging voltage. If the same battery is charged with different powers, the average charging voltage will vary greatly, so it is meaningless to compare the average charging voltage at different powers. The temperature is similar, but the difference is that the change in temperature has a relatively weak effect on the average charging voltage. Therefore, when using the same international unit, the absolute value of the temperature error range can be larger than the power error range.

[0041] In addition, the first average charging voltage is used to characterize the average voltage of the positive and negative electrodes of the battery during the charging process.

[0042] In one embodiment, the average charging voltage is calculated as the ratio of energy to capacity during a single charging process.

[0043] Energy refers to the total power consumption during the entire charging process, and capacity refers to the total amount of charge stored in the battery during the charging process.

[0044] The energy calculation formula is as follows:

[0045] Energy = ∫V(t) × I(t)dt, where V(t) is the voltage at time t and I(t) is the current at time t.

[0046] The capacity is calculated as follows:

[0047] Capacity = ∫I(t)dt.

[0048] In this embodiment, the accuracy of the first average charging voltage is at least 0.005V. In other words, the minimum requirement for measuring the first average charging voltage is to achieve an accuracy of 0.005V. For example, when collecting the first average charging voltage of a first cycle process, the first average charging voltage may be 3.33V. Furthermore, in one embodiment, the accuracy of the first average charging voltage is between 0.001V and 0.0005V. In one embodiment, the accuracy of the first average charging voltage is 0.001V. That is, when the accuracy of the first average charging voltage is 0.001V, the first average charging voltage collected in a first cycle process may be 3.334V.

[0049] In the embodiment, the charging voltage has the best effect when its accuracy is between 0.001V and 0.0005V. The reason is that the higher the accuracy, the higher the cost of the required voltage measuring device, such as a voltmeter. At the same time, higher accuracy does not mean better effect, because when the accuracy of the first average charging voltage is 0.005V, the change trend is easier to judge. When the accuracy of the first average charging voltage is 0.001V, the change trend is already very clear. At the same time, the first average charging voltage obtained by the voltage measuring device with an accuracy lower than 0.005V in multiple first cycle processes is difficult to meet the needs and it is difficult to observe the trend, so the accuracy of the first average charging voltage is at least 0.005V.

[0050] Through the above operations, this step realizes the comprehensive collection and acquisition of the first average charging voltage of the lithium iron phosphate battery during multiple first cycles, ensuring the accuracy and reliability of the data basis for battery degradation risk judgment in subsequent steps.

[0051] In addition, during a single first cycle, the charge and discharge rate of the lithium iron phosphate battery is charged and discharged within the design operating condition range of the lithium iron phosphate battery, where the design operating condition refers to safe power and safe temperature. In this embodiment, by setting reasonable design operating conditions, the stability of the electrochemical reaction of the battery is ensured to avoid overheating caused by too high a rate and reduced energy efficiency or battery performance caused by too low a rate. Violation of this design operating condition range may lead to accelerated battery capacity decay and shorten the battery life. However, since the design and use of batteries and supporting charging facilities in industrial and commercial applications are often subject to relevant protocols or standards, the design operating condition range will not be violated in most cases in actual use.

[0052] Step S20: Obtaining a variation trend of the first average charging voltage as the number of cycles increases.

[0053] In this embodiment, the change trend includes a growing state and a non-growing state.

[0054] The growth state is used to indicate that the rate of change of the first average charging voltage exceeds a preset first amplitude threshold, and the rate of change of the first average charging voltage is used to characterize the rate of change of the first average charging voltage as the number of cycles increases within a certain cycle interval. The opposite of the growth state is the non-growth state, which can be considered to include a steady state, a decreasing state, and a slowly growing state. The steady state is used to characterize that the amplitude of change of the first average charging voltage with the number of cycles fluctuates within a preset range, and there is no significant increase or decrease trend.

[0055] Step S30: determining the attenuation risk of the lithium iron phosphate battery according to the change trend.

[0056] If the change trend is an increasing state, it is at least determined that the attenuation risk of the lithium iron phosphate battery is high. If the change trend is a non-increasing state, it is at least determined that the attenuation risk of the lithium iron phosphate battery is low.

[0057] In this embodiment, the high attenuation risk refers to the attenuation risk of the same lithium iron phosphate battery in a non-increasing state of change trend.

[0058] In the prior art, the attenuation risk of lithium iron phosphate batteries is usually judged by observing the degree of lithium deposition inside the battery. In order to monitor the lithium deposition phenomenon, the prior art often adopts two methods: one is to disassemble the battery for internal analysis and directly evaluate the lithium deposition through microscopic observation or other analytical means; the other is to use a reference electrode to indirectly measure the degree of lithium deposition. However, disassembling the battery for analysis is not only costly, but also involves complex operating steps and damage to the battery structure, which is difficult to use for battery monitoring in actual operation. On the other hand, although the use of a reference electrode can monitor lithium deposition without destroying the battery, with long-term use, the reference electrode is prone to drift, resulting in inaccurate measurement data, which further affects the judgment of the attenuation risk. Therefore, in actual applications, the prior art is often difficult to accurately predict the risk of battery attenuation through direct lithium deposition detection.

[0059] However, after my research, I found that, unlike the prior art, if the change trend is an increasing state, then the attenuation risk of the lithium iron phosphate battery is high. On the contrary, if the change trend is a non-increasing attenuation risk, then the attenuation risk of the lithium iron phosphate battery is low. A more detailed description of this technical feature will be explained later.

[0060] In this embodiment, by collecting the first average charging voltage of the lithium iron phosphate battery in each first cycle and observing the change trend, the battery attenuation risk is judged. This step avoids the high cost and operational complexity of the traditional lithium plating monitoring method by real-time monitoring of the voltage change during the charging process, and does not require disassembling the battery, so it is suitable for battery monitoring in practical applications.

[0061] In this embodiment, the battery degradation risk is judged by observing the change trend.

[0062] In one embodiment, the voltage variation trend is calculated by step AC as follows:

[0063] Step A: Calculate the voltage change rate within a preset cycle number interval to obtain an average voltage change rate.

[0064] In this embodiment, the average voltage change rate is obtained based on the first average charging voltage in the cycle number interval.

[0065] In one embodiment, the cycle number interval refers to a continuous cycle number range pre-set for data collection and analysis during the charge and discharge cycle of the battery. Specifically, the cycle number interval starts from a specific cycle process as the starting point and continues to a set end point, wherein the cycle number interval includes a plurality of first cycle processes. It should be noted that the starting point and the end point of the cycle number interval are not necessarily the first cycle process, as long as there are multiple first cycle processes in the cycle number interval, which is not limited here.

[0066] The purpose of the cycle number interval is to evaluate the changing trend of the lithium iron phosphate battery within a limited range of times, so as to judge the attenuation risk of the lithium iron phosphate battery.

[0067] Furthermore, in one embodiment, for ease of description, it is assumed that all cycle processes in the cycle number interval are first cycle processes. The selection of the cycle number interval starts from the starting point of the first average charging voltage obtained most recently, and moves forward a certain number of cycles. For example, if there are 500 first cycle processes in the cycle number interval, the cycle number interval may correspond to the 4500th cycle to the 5000th cycle. Within the cycle number interval, the first average charging voltage is collected and used for subsequent trend analysis. With the use of lithium iron phosphate batteries, new cycle number intervals are constantly generated. For example, when it is used for 6000 cycles, the cycle number interval may correspond to the 5500th cycle to the 6000th cycle.

[0068] Furthermore, in one embodiment, the number of first cycle processes in the cycle number interval is proportional to the battery capacity.

[0069] As the battery capacity increases, the battery can usually operate at a lower charging current density, so the pressure on the negative electrode surface becomes smaller and the side effects caused by lithium plating are also weakened. Therefore, more continuous first cycle processes (larger cycle number range) are required to observe obvious trends.

[0070] In this embodiment, the average voltage change rate is obtained by processing a plurality of first average charging voltages in the interval. In one embodiment, the average voltage change rate can reflect a change trend.

[0071] In this embodiment, the average voltage change rate may be obtained in a variety of ways, such as directly calculating the change rate based on the first average charging voltage values ​​at the starting point and the end point within the cycle number interval.

[0072] In another embodiment, a method for calculating the average voltage change rate is provided. Method 1: that is, calculating the average change rate of the first average charging voltage within a preset cycle number interval, specifically as follows:

[0073] First, within a preset cycle number interval, all first average charging voltages are acquired to obtain multiple data points. Assume that within a cycle number interval, N first average charging voltages are acquired, namely V1, V2, …, V N .

[0074] Then calculate the voltage change rate between every two consecutive first average charging voltages: i and V i+1 , calculate the voltage change rate R between them i , the formula is as follows:

[0075]

[0076] Where R i is the rate of change between the i-th and i+1-th charging voltages, expressed in voltage change per cycle.

[0077] Next, take the average of all the change rates: average all the voltage change rates R1, R2, ..., R N-1 Average to get the average rate of change in the interval

[0078]

[0079] By summing up the voltage change rate of each adjacent first average charging voltage within a preset cycle number interval and taking the average value, this method can reflect the overall trend of voltage change in the entire cycle interval. By taking the average change rate, the influence of a single outlier is eliminated, ensuring the robustness of the voltage change rate.

[0080] In another embodiment, another method for calculating the average voltage change rate is provided, namely, method 2. Method 2 is generally similar to the previous method 1, except that method 2 removes outliers within a preset cycle number interval by an identification method. For example, the standard deviation method or the interquartile range method is used to remove the first average charging voltage that obviously deviates from the normal range, and then the change rate is calculated for the remaining data using the method of method 1. This method ensures that the calculation results are more representative and reduces the interference of occasional errors on voltage trend analysis.

[0081] In another embodiment, another method for calculating the average voltage change rate is provided, namely, method 3. Method 3 uses polynomial fitting or linear regression technology to fit the data within a preset cycle number interval, wherein the horizontal and vertical coordinates of the curve are the numerical value of the first average charging voltage and the number of cycles corresponding to the first average charging voltage, respectively. That is, fitting is performed based on the first average charging voltage to obtain a fitting curve; based on the fitting curve, the average voltage change rate is obtained. After fitting, the change rate is calculated by the slope of the fitting curve. For example, the average change rate can be calculated for a preset cycle number interval after derivation. This method can smooth out short-term fluctuations and capture longer-term trends. At the same time, since there is a fitting curve, the overall ups and downs can be intuitively seen after derivation.

[0082] Step B: If the average voltage change rate is greater than the first amplitude threshold, the change trend is an increasing state.

[0083] In one implementation, the change trend can be determined by calculating the average voltage change rate and comparing the average voltage change rate with a preset first amplitude threshold.

[0084] like Figure 2 As shown, Figure 2 It is a graph of the first average charging voltage and the number of cycles of a lithium iron phosphate battery, wherein each cycle process meets the requirements of the first cycle process.

[0085] In one embodiment, during each first cycle, the battery is charged from a relatively low state of charge to a higher state of charge, and discharged from a higher state of charge to a lower state of charge, wherein the power level during the charging and discharging process remains consistent. The power level during the charging and discharging process refers to the power level during the charging process and the power level during the discharging process. The power level during the charging and discharging process remains consistent means that during a first cycle of the battery, the power during the charging process is roughly equivalent to the power during the discharging process. In other words, the difference between the power during the charging process and the power during the discharging process is within a preset error. For example, the error can be 0.05W, and during a cycle, the power during the charging process can be 10.01W, and the power during the discharging process can be 10.05W. It can be found that the difference between the two is 0.04W, which is within the preset error range, so during the cycle, the power level during the charging and discharging process is consistent. The power during the charging process can be the average power during the entire charging process, and the power during the discharging process can be the average power during the entire discharging process.

[0086] For example, during the charging process in each first cycle, the battery is charged from a first preset power level to a higher second preset power level, and during the discharging process, the battery is discharged from the second preset power level to the first preset power level.

[0087] The first preset power and the second preset power are both preset values. During the charging and discharging process, the charging and discharging power is basically the same, which means that the charging power and the discharging power used are roughly the same in value, or the difference between the charging power and the discharging power is within a preset deviation range.

[0088] and Figure 2 Each cycle in the process of charging is to fully charge the battery from 0% power, and discharge it from 100% power to 0% power during the process of discharging, and the power during the charging process is the same as the power during the discharging process. Figure 2 Give an example. Figure 2 After analysis, it can be found that the first average charging voltage drops rapidly in the first few hundred cycles and then stabilizes. This phenomenon can be attributed to the self-stabilization process of the lithium iron phosphate battery in the early stage. In the initial charge and discharge cycle, the active lithium and electrolyte inside the battery will gradually adjust to a stable state, which will cause the voltage to drop rapidly in the first few hundred cycles. After that, throughout the entire intermediate stage, the curve is relatively flat, which means that no significant lithium precipitation occurs in the lithium iron phosphate battery. At the position after the coordinate system is positioned, about 5000 cycles later, it can be seen that the first average charging voltage rises rapidly in this stage.

[0089] like Figure 3 As shown, Figure 3 yes Figure 2 The enlarged diagram better shows the part when the first average charging voltage is rising. The average voltage change rate in the cycle number interval can be obtained by any of the above-mentioned methods 1 to 3 or other existing methods, and then compared with the preset first amplitude threshold. Assuming a is the slope curve represented by the preset first amplitude threshold, it can be obtained Figure 3 The changing trend of the lithium iron phosphate battery is in an increasing state, so the attenuation risk of the lithium iron phosphate battery is high at this time.

[0090] Step C: When the average voltage change rate is less than or equal to the preset first amplitude threshold, the change trend is determined to be a non-increasing state.

[0091] In one implementation, by analyzing the average voltage change rate, when the change trend is a non-increasing state, it is at least determined that the attenuation risk of the lithium iron phosphate battery is low at this time.

[0092] Figure 2 This is a graph showing the relationship between the first average charging voltage and the number of cycles of a 150Ah lithium iron phosphate battery;

[0093] Figure 4 yes Figure 2 Physical picture of the negative electrode and diaphragm interface of lithium iron phosphate battery after the end of the number of cycles shown in the figure;

[0094] Figure 5 This is a graph showing the relationship between the first average charging voltage and the number of cycles of a 50Ah lithium iron phosphate battery;

[0095] Figure 6 yes Figure 5 Physical picture of the negative electrode and diaphragm interface of the lithium iron phosphate battery after the end of the illustrated cycle number.

[0096] In this embodiment, according to Figure 2 , Figure 4 , Figure 5 , Figure 6 Prove the conclusion of this technical solution: if the change trend is a growth state, then at least it is determined that the attenuation risk of the lithium iron phosphate battery is high at this time; if the change trend is a non-growth state with the increase in the number of cycles, then at least it is determined that the attenuation risk of the lithium iron phosphate battery is low at this time.

[0097] first Figure 2 and Figure 4 It is the same lithium iron phosphate battery, Figure 4 The black circles mark some of the lithium phenomena in the analysis. Figure 4 There are obvious circular structures and traces of sediments in it. This is a physical picture of the negative electrode of lithium iron phosphate. After analysis, it was identified that the circular structure sediment here is lithium precipitated from the positive electrode.

[0098] Figure 5 and Figure 6 It is also the same lithium iron phosphate battery. You can see Figure 6 The negative electrode and separator remained clean after more than 7000 cycles, and no obvious lithium deposition was found. Figure 2 and Figure 4 The corresponding 150Ah lithium iron phosphate battery Figure 5 and Figure 6 The corresponding 50Ah lithium iron phosphate battery differs only in capacity.

[0099] Therefore, in summary, when it is determined that the attenuation risk of the lithium iron phosphate battery is high at this time, the lithium plating phenomenon of the lithium iron phosphate battery is more obvious than the lithium plating phenomenon of the same lithium iron phosphate battery when the attenuation risk is low.

[0100] From the actual picture, we can see that both lithium iron phosphate batteries are the same square shell battery, but this conclusion can be extended to other lithium iron phosphate batteries such as soft pack batteries. The type of lithium iron phosphate battery is square shell battery or soft pack battery. Here is a theoretical explanation of the relationship between the trend and attenuation of this technical solution, as follows:

[0101] Inside the lithium iron phosphate battery, when there is no obvious accelerated capacity decay or "diving" phenomenon caused by lithium plating, the voltage change of the battery is mainly determined by its material properties. Since the lithium iron phosphate positive electrode material has a relatively stable voltage platform during the charging process, that is, the voltage does not change much with the charging time, the voltage fluctuation of the entire battery is small under normal working conditions. The decay of battery capacity is mainly caused by the loss of active lithium. When the number of lithium ions embedded in the negative electrode material during charging decreases, the lithium insertion voltage of the negative electrode will be higher. If there is no lithium plating phenomenon, the total voltage of the battery can be expressed as the positive electrode voltage minus the negative electrode voltage. Therefore, as the number of battery cycles increases, although the active lithium gradually decreases, the total voltage will still show a slow downward trend, and there will be no obvious accelerated decay or diving phenomenon.

[0102] On the contrary, when there is significant lithium precipitation inside the battery, it will lead to accelerated decay of the battery capacity during the cycle. At this time, although the positive electrode voltage does not change much, the impedance of the negative electrode will increase due to lithium precipitation, which will lead to a significant enhancement of the polarization effect. The intensified polarization of the negative electrode will increase the polarization voltage of the battery during charging, thereby increasing the overall charging voltage of the battery. Although the loss of active lithium is still the main cause of capacity decay, due to the influence of negative electrode polarization, the increase in battery voltage will mask the voltage decrease trend caused by the loss of active lithium, causing the average voltage of the battery to gradually increase. This phenomenon is a risk signal of accelerated capacity decay or diving in the late cycle.

[0103] It is understood by those skilled in the art that the present invention implements all or part of the processes in the method of the above embodiment, and can also be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of each of the above method embodiments when executed by the processor. Among them, the computer program includes a computer program, and the computer program can be in source code form, object code form, executable file or some intermediate form. The computer-readable storage medium may include: any entity or device, medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electric carrier signal, telecommunication signal and software distribution medium that can carry a computer program. It should be noted that the content contained in the computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, the computer-readable storage medium does not include electric carrier signals and telecommunication signals.

[0104] Furthermore, the present invention also provides a control device. In one embodiment of the control device according to the present invention, the control device includes a processor and a storage device. The storage device can be configured to store a program for executing the attenuation identification method applied to the battery in the above method embodiment. The processor can be configured to execute the program in the storage device, which includes but is not limited to executing the attenuation identification method applied to the battery in the above method embodiment. For ease of explanation, only the parts related to the embodiment of the present invention are shown. For specific technical details not disclosed, please refer to the method part of the embodiment of the present invention. The control device can be a control device device formed by various electronic devices.

[0105] Furthermore, the present invention also provides a computer-readable storage medium. In a computer-readable storage medium embodiment according to the present invention, the computer-readable storage medium can be configured to store a program for executing the attenuation identification method applied to a battery in the above-mentioned method embodiment, and the program can be loaded and run by a processor to implement the above-mentioned attenuation identification method applied to a battery. For ease of explanation, only the parts related to the embodiment of the present invention are shown. For specific technical details not disclosed, please refer to the method part of the embodiment of the present invention. The computer-readable storage medium can be a storage device formed by various electronic devices. Optionally, the computer-readable storage medium in the embodiment of the present invention is a non-temporary computer-readable storage medium.

[0106] Further, it should be understood that since the setting of each module is only for illustrating the functional units of the device of the present invention, the physical devices corresponding to these modules may be the processor itself, or a part of the software in the processor, a part of the hardware, or a part of the combination of software and hardware. Therefore, the number of each module in the figure is only schematic.

[0107] Those skilled in the art will appreciate that the modules in the device can be adaptively split or merged. Such splitting or merging of specific modules will not cause the technical solution to deviate from the principle of the present invention, and therefore, the technical solutions after splitting or merging will fall within the protection scope of the present invention.

[0108] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for identifying battery attenuation, characterized in that: include: Collecting a first average charging voltage of the battery during a plurality of first cycle processes, wherein the first cycle process is used to characterize a charging process and a discharging process of the battery, and the first average charging voltage is used to characterize an average voltage of the positive and negative electrodes of the battery during the charging process, and charging is performed at a preset power during the charging process; Obtaining a variation trend of the first average charging voltage as the number of cycles increases; The battery degradation risk is determined based on the change trend.

2. According to the attenuation identification method for a battery according to claim 1, the step of judging the attenuation risk of the battery according to the change trend comprises: If the change trend is an increasing state, it is at least determined that the attenuation risk of the battery is high at this time, wherein the increasing state is used to indicate that the change rate of the first average charging voltage exceeds a preset first amplitude threshold.

3. The attenuation identification method for a battery according to claim 2, characterized in that: The method for obtaining the change trend includes the following steps: Based on the first average charging voltage within a preset cycle number interval, calculating a change rate of the first average charging voltage to obtain an average voltage change rate, wherein the average voltage change rate is used to characterize a change trend of the first average charging voltage; If the average voltage change rate is greater than the first amplitude threshold, the change trend is an increasing state.

4. The attenuation identification method for a battery according to claim 3, characterized in that: The calculating the change rate of the first average charging voltage based on the first average charging voltage within a preset cycle number interval to obtain the average voltage change rate includes: Obtaining a first average charging voltage within a preset cycle number interval; Calculating the voltage change rate between every two consecutive first average charging voltages and averaging the voltage change rates to obtain an average voltage change rate; and / or, Obtaining a first average charging voltage within a preset cycle number interval; Remove the outlier first average charging voltage within the preset cycle number interval; Calculating the voltage change rates between a plurality of two consecutive first average charging voltages and averaging the voltage change rates to obtain an average voltage change rate; and / or, Obtaining a first average charging voltage within a preset cycle number interval; Fitting the first average charging voltage and the number of cycles to obtain a fitting curve; Based on the fitting curve, the average voltage change rate is obtained.

5. The attenuation identification method for a battery according to claim 2, characterized in that: As the number of cycles increases, if the change trend is a non-increasing state, it is at least determined that the attenuation risk of the battery is low at this time.

6. The attenuation identification method for a battery according to any one of claims 1 to 4, characterized in that: The accuracy of the first average charging voltage is at least 0.005V.

7. The attenuation identification method for a battery according to any one of claims 1 to 4, characterized in that: The battery is a square-shell battery or a soft-pack battery.

8. The attenuation identification method applied to a battery according to claim 3 or 4, characterized in that: The number of first cycle processes in the cycle number interval is proportional to the battery capacity.

9. The attenuation identification method for a battery according to claim 1, characterized in that: The battery is a lithium iron phosphate battery.

10. The attenuation identification method for a battery according to claim 1, characterized in that: In the charging process, charging is performed at a preset ambient temperature.

11. The attenuation identification method for a battery according to any one of claims 1 to 10, characterized in that: During each first cycle, the battery is charged from a relatively low state of charge to a higher state of charge, and discharged from a higher state of charge to a lower state of charge, wherein the power level during the charging and discharging process remains constant.

12. The attenuation identification method for a battery according to claim 11, characterized in that: The battery is charged from a relatively low state of charge to a higher state of charge, and discharged from a higher state of charge to a lower state of charge, including: during the charging process, the battery is charged from a first preset power to a higher second preset power, and during the discharging process, the battery is discharged from the second preset power to the first preset power.

13. A control device, comprising a processor and a storage device, wherein the storage device is suitable for storing a plurality of computer programs, characterized in that: The computer program is suitable for being loaded and run by the processor to execute the attenuation identification method for a battery according to any one of claims 1 to 12.

14. A computer-readable storage medium storing a plurality of computer programs, characterized in that: The computer program is suitable for being loaded and run by a processor to execute the attenuation identification method for a battery according to any one of claims 1 to 12.

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