Battery prediction and early warning method and device

Abstract

The invention provides a battery prediction and early warning method and device, and the method can obtain an actually measured expansive force curve of a lithium iron phosphate battery in a charging process, and respectively determines a maximum expansive force value of the actually measured expansive force curve at SOC = about 30% and a maximum expansive force value of the actually measured expansive force curve at SOC = about 100%. And carrying out capacity loss prediction and / or sharp degradation judgment on the lithium iron phosphate battery according to the actual pressure difference between the two expansive forces and a pre-constructed capacity loss model. Therefore, capacity loss prediction and / or rapid degradation early warning can be realized by using the size relationship between the two expansion force peak values and the pressure difference in the charging process based on the charging and discharging platform characteristics of the lithium iron phosphate battery, so that the accuracy of prediction and early warning can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery prediction and early warning method and device. Background Art

[0002] Lithium-ion batteries, with their high energy density and long cycle life, are currently widely used in various electronic products and new energy vehicles. Among lithium-ion batteries, lithium iron phosphate batteries (LIFP) dominate the power battery market due to their safety, high specific energy and power, and long cycle life. However, due to the unique charging and discharging characteristics of LFP batteries, existing technologies have difficulty accurately predicting and warning LFP battery performance. Summary of the Invention

[0003] The purpose of this application is to solve at least one of the above-mentioned technical deficiencies, especially the technical defect of low accuracy of prediction and early warning in the prior art.

[0004] In a first aspect, an embodiment of the present application provides a battery prediction and warning method, comprising:

[0005] Obtaining a measured expansion force curve of the lithium iron phosphate battery during charging; wherein the measured expansion force curve is used to reflect the change of the expansion force of the lithium iron phosphate battery during charging with SOC;

[0006] determining a maximum expansion force value of the measured expansion force curve in a first SOC interval and obtaining a first pressure value; wherein an upper limit value of the first SOC interval is greater than 30% and a lower limit value is less than 30%;

[0007] determining a maximum expansion force of the measured expansion force curve in a second SOC interval and obtaining a second pressure value; wherein an upper limit value of the second SOC interval is 100% and a lower limit value is greater than or equal to the SOC corresponding to the minimum expansion force value in the measured expansion force curve;

[0008] calculating an actual pressure difference according to the first pressure value and the second pressure value;

[0009] Based on the actual pressure difference and a pre-constructed capacity loss model, the capacity loss prediction and / or rapid deterioration judgment of the lithium iron phosphate battery are performed; wherein the capacity loss model is used to describe the relationship between the capacity loss rate of the lithium iron phosphate battery and the expansion force pressure difference during the charging process.

[0010] In some embodiments, judging the rapid degradation of the lithium iron phosphate battery based on the actual pressure difference and a pre-built capacity loss model includes:

[0011] Determining whether it is necessary to perform a rapid degradation determination process on the lithium iron phosphate battery according to the actual pressure difference;

[0012] If necessary, performing a capacity loss test on the lithium iron phosphate battery and obtaining an actual capacity loss value and a latest actual pressure difference;

[0013] Substituting the actual capacity loss value into the capacity loss model for calculation, and obtaining a predicted pressure difference;

[0014] Whether the lithium iron phosphate battery has experienced rapid deterioration is determined based on the difference between the latest actual pressure difference and the predicted pressure difference.

[0015] In some embodiments, judging whether the lithium iron phosphate battery has experienced rapid deterioration based on the difference between the latest actual pressure difference and the predicted pressure difference includes:

[0016] If the difference between the latest actual pressure difference and the predicted pressure difference is less than a first preset threshold, it is determined that the lithium iron phosphate battery has undergone rapid deterioration, and the cause of the rapid deterioration is battery gas production; wherein the first preset threshold is less than zero.

[0017] In some embodiments, judging whether the lithium iron phosphate battery has experienced rapid deterioration based on the difference between the latest actual pressure difference and the predicted pressure difference includes:

[0018] If the difference between the latest actual pressure difference and the predicted pressure difference is greater than a second preset threshold, it is determined that the lithium iron phosphate battery has undergone rapid deterioration, and the cause of the rapid deterioration is other side reactions;

[0019] The second preset threshold is greater than zero, and the other side reactions refer to side reactions other than battery gas production.

[0020] In some embodiments, judging whether it is necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery according to the actual pressure difference includes:

[0021] determining, based on actual pressure differences of the lithium iron phosphate battery during multiple charging processes, whether a sudden change occurs in the actual pressure difference of the lithium iron phosphate battery;

[0022] If so, it is necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery; otherwise, it is not necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery.

[0023] In some embodiments, judging whether it is necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery according to the actual pressure difference includes:

[0024] If the absolute difference between the actual pressure difference and the predicted pressure difference is greater than a third preset threshold, it is necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery; otherwise, it is not necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery.

[0025] In some embodiments, the capacity loss prediction of the lithium iron phosphate battery based on the actual pressure difference and a pre-built capacity loss model includes:

[0026] The actual pressure difference is substituted into the capacity loss model for calculation to obtain a predicted capacity loss value of the lithium iron phosphate battery.

[0027] In some embodiments, the step of constructing the capacity loss model includes:

[0028] Obtain the charge expansion force curve of the sample lithium iron phosphate battery at different charge and discharge cycle times;

[0029] Obtaining a capacity loss curve of the sample lithium iron phosphate battery; the capacity loss curve is used to describe the relationship between the actual capacity loss value of the sample lithium iron phosphate battery and the number of charge and discharge cycles;

[0030] Data fitting is performed based on the capacity loss curve and each of the charge expansion force curves to obtain the capacity loss model.

[0031] In some embodiments, when the lithium iron phosphate battery is disposed in a battery pack or a battery module, obtaining a measured expansion force curve of the lithium iron phosphate battery during charging includes:

[0032] charging the battery pack or battery module;

[0033] During the charging process, the expansion force of the battery pack or battery module is collected by a pressure sensor located at a target position, and the measured expansion force curve is obtained; wherein the target position is the center position of the highest temperature area in the battery pack or battery module.

[0034] In a second aspect, an embodiment of the present application provides a battery prediction and warning device, comprising:

[0035] a first curve acquisition module, configured to acquire a measured expansion force curve of the lithium iron phosphate battery during charging; wherein the measured expansion force curve is configured to reflect changes in the expansion force of the lithium iron phosphate battery as a function of SOC during charging;

[0036] a first pressure value determination module, configured to determine a maximum expansion force value of the measured expansion force curve in a first SOC interval and obtain a first pressure value; wherein an upper limit value of the first SOC interval is greater than 30% and a lower limit value is less than 30%;

[0037] a second pressure value determination module, configured to determine a maximum expansion force of the measured expansion force curve in a second SOC interval and obtain a second pressure value; wherein an upper limit of the second SOC interval is 100% and a lower limit is greater than or equal to the SOC corresponding to the minimum expansion force value in the measured expansion force curve;

[0038] an actual pressure difference calculation module, configured to calculate an actual pressure difference based on the first pressure value and the second pressure value;

[0039] A prediction and warning module is used to predict capacity loss and / or judge rapid deterioration of the lithium iron phosphate battery based on the actual pressure difference and a pre-constructed capacity loss model; wherein the capacity loss model is used to describe the relationship between the capacity loss rate of the lithium iron phosphate battery and the expansion force pressure difference during the charging process.

[0040] In a third aspect, an embodiment of the present application provides a storage medium storing computer-readable instructions. When the computer-readable instructions are executed by one or more processors, the one or more processors execute the steps of the battery prediction and warning method described in any of the above embodiments.

[0041] In a fourth aspect, an embodiment of the present application provides a computer device, the computer device comprising: one or more processors, and a memory;

[0042] The memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the battery prediction and warning method described in any one of the above embodiments are executed.

[0043] In the battery prediction and early warning methods and devices provided in some embodiments of the present application, the measured expansion force curve of the lithium iron phosphate battery during the charging process can be obtained, and the maximum expansion force value of the measured expansion force curve at approximately SOC = 30% and the maximum expansion force value of the measured expansion force curve at approximately SOC = 100% can be determined respectively. Based on the actual pressure difference between the two expansion forces and a pre-established capacity loss model, capacity loss prediction and / or rapid degradation judgment can be performed on the lithium iron phosphate battery. In this way, based on the charge and discharge platform characteristics of the lithium iron phosphate battery, the relationship between the two expansion force peaks and the pressure difference during the charging process can be used to achieve capacity loss prediction and / or rapid degradation early warning, thereby improving the accuracy of the prediction and early warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0045] Figure 1 A flowchart of a battery prediction and warning method in some embodiments;

[0046] Figure 2 A schematic flow chart of steps for constructing a capacity loss model in some embodiments;

[0047] Figure 3 A schematic diagram of a charging expansion force curve of a sample lithium iron phosphate battery over its entire life cycle in some embodiments;

[0048] Figure 4 A schematic diagram of a capacity loss curve of a sample lithium iron phosphate battery in some embodiments;

[0049] Figure 5 The corresponding relationship between the actual capacity loss value and the actual pressure difference of the sample lithium iron phosphate battery at different cycle numbers in some embodiments;

[0050] Figure 6 A schematic diagram of a capacity loss model curve in some embodiments;

[0051] Figure 7 Schematic diagram of a flow chart of the steps for determining rapid degradation of a lithium iron phosphate battery in some embodiments;

[0052] Figure 8 A comparison chart of the prior art and the prediction of this application;

[0053] Figure 9 FIG1 is a schematic diagram showing how the first pressure value of a lithium iron phosphate battery changes with the number of charge and discharge cycles in some embodiments;

[0054] Figure 10 FIG1 is a schematic diagram showing how the second pressure value of a lithium iron phosphate battery changes with the number of charge and discharge cycles in some embodiments;

[0055] Figure 11 FIG1 is a schematic diagram showing how the actual pressure difference of a lithium iron phosphate battery changes with the number of charge and discharge cycles in some embodiments;

[0056] Figure 12 FIG2 is a second schematic diagram of how the first pressure value of a lithium iron phosphate battery changes with the number of charge and discharge cycles in some embodiments;

[0057] Figure 13 FIG2 is a second schematic diagram of how the second pressure value of a lithium iron phosphate battery changes with the number of charge and discharge cycles in some embodiments;

[0058] Figure 14 Schematic diagram 2 of the change in actual pressure difference of a lithium iron phosphate battery with the number of charge and discharge cycles in some embodiments;

[0059] Figure 15 A schematic diagram of the structure of a battery prediction and warning device in some embodiments;

[0060] Figure 16 This is a diagram of the internal structure of a computer device in some embodiments. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0062] In some embodiments, this application provides a battery prediction and early warning method. The following embodiments illustrate this method using a computer device as an example. It is understood that the computer device described herein can be an electronic device with data acquisition and data processing capabilities, including, but not limited to, various personal computers, notebook computers, laptop computers, tablet computers, smartphones, and the like. Furthermore, the computer device can be a standalone device or integrated into various battery data collection and analysis devices, and this application does not impose specific limitations on this.

[0063] like Figure 1 As shown, the battery prediction and warning method provided by this application may include the following steps:

[0064] S102: Obtaining a measured expansion force curve of the lithium iron phosphate battery during charging; wherein the measured expansion force curve is used to reflect changes in the expansion force of the lithium iron phosphate battery during charging as a function of SOC;

[0065] S104: Determine a maximum expansion force value of the measured expansion force curve in a first SOC interval and obtain a first pressure value; wherein an upper limit value of the first SOC interval is greater than 30% and a lower limit value is less than 30%;

[0066] S106: Determine the maximum expansion force of the measured expansion force curve in the second SOC interval and obtain a second pressure value; wherein the upper limit of the second SOC interval is 100%, and the lower limit is greater than or equal to the SOC corresponding to the minimum expansion force value in the measured expansion force curve;

[0067] S108: Calculating an actual pressure difference based on the first pressure value and the second pressure value;

[0068] S110: Predicting capacity loss and / or determining rapid degradation of the lithium iron phosphate battery based on the actual pressure difference and a pre-established capacity loss model; wherein the capacity loss model is used to describe the relationship between the capacity loss rate of the lithium iron phosphate battery and the expansion force pressure difference during the charging process.

[0069] Specifically, the inventors discovered that during the charging process of lithium iron phosphate batteries, the expansion force of the lithium iron phosphate battery exhibits an increase-decrease-increase trend. This is due to the fact that during the battery charging process, the lithium iron phosphate (LiFePO4) phase of the cathode moves towards the iron phosphate (FePO4) phase. Lithium iron phosphate and iron phosphate have similar structures, but the volume of iron phosphate is approximately 6.81% smaller than that of lithium iron phosphate. Therefore, the thickness of the battery's cathode electrode plate continues to decrease during charging. The battery's anode graphite, on the other hand, has a layered structure. After lithium is embedded between the layers, the thickness of the anode electrode plate continues to increase. Therefore, the thickness of the anode electrode plate gradually increases during charging.

[0070] In the early stages of charging, the cathode's LiFePO4 doesn't shrink significantly, while the anode's graphite expands, causing the lithium iron phosphate battery's expansion force to rise. In the middle stages of charging, the cathode's FePO4 contracts, partially offsetting the pressure change caused by the anode's graphite expansion, causing the battery's expansion force to decline. In the late stages of charging, the cathode's FePO4 no longer shrinks, but the anode's graphite continues to expand, causing the battery's expansion force to rise again. Based on this analysis, the lithium iron phosphate battery's expansion force exhibits an increase-decrease-increase trend during charging, while the expansion force change trend during discharge is the opposite of that during charging.

[0071] The inventors' research has found that when the SOC (State of Charge) is around 30%, the expansion rate of the anode graphite is greater than the contraction rate of the cathode LiFePO4, causing the battery cell to expand and the battery's expansion force to increase. When the SOC is between 30% and 65%, the expansion rate of the anode graphite is less than the contraction rate of the cathode FePO4, causing the battery cell to contract and the battery's expansion force to decrease. When the SOC is between 65% and 100%, the expansion rate of the anode graphite is greater than the contraction rate of the cathode FePO4, causing the battery cell to expand and the expansion force to increase.

[0072] Based on the above findings, in the battery early warning prediction solution provided by this application, the measured expansion force curve of the lithium iron phosphate battery during the charging process can be obtained first. The measured expansion force curve can show how the expansion force of the lithium iron phosphate battery during the charging process changes with the SOC. For example, the horizontal coordinate of the measured expansion force curve can be SOC, and the vertical coordinate can be the battery expansion force. For another example, the horizontal coordinate of the measured expansion force curve can be battery expansion force, and the vertical coordinate can be SOC. It should be noted that the expansion force described in this application can be the pressure on the large surface of the lithium iron phosphate battery casing. Since the expansion force changes the most here, the expansion force change can be more clearly reflected, thereby improving the detection accuracy.

[0073] When a measured expansion force curve is obtained, the present application can determine the maximum expansion force value of the measured expansion force curve in the first SOC range and obtain a first pressure value. Since the upper limit of the first SOC range is greater than 30% and the lower limit of the first SOC range is less than 30%, the first pressure value can be understood as the peak expansion force of the lithium iron phosphate battery in the early and middle stages of charging.

[0074] Furthermore, the present application can determine the maximum expansion force of the measured expansion force curve in the second SOC range and obtain a second pressure value. Since the upper limit of the second SOC range is 100%, and the lower limit of the second SOC range is greater than or equal to the SOC corresponding to the expansion force in the measured expansion force curve, the second pressure value can be understood as the peak expansion force of the lithium iron phosphate battery in the middle and late stages of charging. In other words, the first pressure value and the second pressure value are the two peak expansion force values ​​of the lithium iron phosphate battery during the charging process.

[0075] After obtaining a first pressure value and a second pressure value, the present application can calculate the numerical difference between the two pressure values ​​and obtain the actual pressure difference. It will be appreciated that the specific formula for calculating the actual pressure difference can be determined based on actual circumstances and is not specifically limited in the present application. It is sufficient that the actual pressure difference reflects the numerical difference between the first and second pressure values. For example, a computer device may use the difference between the first pressure value and the second pressure value as the actual pressure difference. For ease of illustration and description, some embodiments of the present application use the difference between the second pressure value and the first pressure value as the actual pressure difference.

[0076] Once the actual pressure difference is calculated, the computer device can predict capacity loss and / or provide a rapid degradation warning for the lithium iron phosphate battery based on the actual pressure difference and a capacity loss model that describes the relationship between the capacity loss rate and the expansion force pressure difference, thereby achieving battery early warning prediction. Capacity loss prediction refers to predicting the capacity loss rate of the lithium iron phosphate battery, and rapid degradation warning refers to determining whether the performance of the lithium iron phosphate battery will drop sharply within a short period of time.

[0077] Compared to solutions that use the expansion force peak itself for prediction and early warning, this application utilizes the magnitude relationship and pressure difference between two expansion force peaks during charging to predict capacity loss and / or early warning of rapid degradation, which can improve the accuracy of prediction and early warning. This is described in detail below.

[0078] The capacity loss model is described in detail below:

[0079] In some embodiments, as Figure 2 As shown in Figure 2, the steps for constructing the capacity loss model include:

[0080] S202: Obtaining a charge expansion force curve of a sample lithium iron phosphate battery under different charge and discharge cycle times;

[0081] S204: Obtaining a capacity loss curve of the sample lithium iron phosphate battery; the capacity loss curve is used to describe the relationship between the actual capacity loss value of the sample lithium iron phosphate battery and the number of charge and discharge cycles;

[0082] S206: Perform data fitting based on the capacity loss curve and each charging expansion force curve to obtain a capacity loss model.

[0083] Specifically, in the process of constructing the capacity loss model, the charging expansion force curve of the sample lithium iron phosphate battery throughout its life cycle can be obtained. The full life cycle described in this application may include charge and discharge cycle conditions and storage conditions. Figure 3 As shown, Figure 3 A schematic diagram of the charging expansion force curve of the sample lithium iron phosphate battery throughout its life cycle is shown. Since the curve records the expansion force change trend of the sample lithium iron phosphate battery under different charge and discharge cycles (i.e., different numbers of cycles), the peak pressure difference of the expansion force of the sample lithium iron phosphate battery throughout its life cycle can be collected, and the pressure difference under different numbers of cycles can be obtained.

[0084] It can be understood that the pressure difference ΔF of the sample lithium iron phosphate battery at the target cycle number is determined based on the maximum expansion force value F1 of the target expansion force curve in the first SOC range and the maximum expansion force value F2 of the target expansion force curve in the second SOC range. For example, ΔF can be the value of (F2-F1). The target expansion force curve refers to the charging expansion force curve corresponding to the target cycle number, and the target cycle number refers to each cycle number.

[0085] In addition, the present application can also obtain the capacity loss curve of the sample lithium iron phosphate battery, which can be shown as Figure 4As shown. Since the capacity loss curve describes the relationship between the actual capacity loss value Qloss of the sample lithium iron phosphate battery and the number of charge and discharge cycles, that is, it describes the actual capacity loss value of the sample lithium iron phosphate battery under different cycle numbers, and step S202 obtains the charging expansion force curve of the sample lithium iron phosphate battery under different cycle numbers, the present application can use the number of cycles as an intermediate parameter for data fitting, and perform data fitting on the capacity loss curve and each charging expansion force curve, thereby obtaining the capacity loss model of the present application. Since the number of cycles itself is the cumulative amount of capacity decay and the cumulative beam of expansion force change, the two originally independent curves can be fitted through the common independent variable "number of cycles" without considering the time dimension, avoiding the complexity of high-dimensional curve fitting, and retaining the characteristic value of the expansion force pressure difference that is most relevant to capacity decay. In this way, the capacity loss model can more accurately describe the relationship between the capacity loss rate and the expansion force pressure difference of the lithium iron phosphate battery.

[0086] For example, in the data fitting process, the present application can obtain the actual capacity loss value and actual pressure difference under multiple cycle numbers respectively, and use the actual capacity loss value and actual pressure difference under the same cycle number as a coordinate point on the coordinate system, thereby obtaining multiple coordinate points. For example, the present application can use the actual capacity loss value as the x-value coordinate and the actual pressure difference as the y-value coordinate, then according to Figure 5 The data shown can be used to obtain coordinate points (0, 78.2), (2.78%, 50.00), (5.28%, 42.50), (7.95%, 16.50), (10.4.%, 3.80), and (13.90%, 9.70). When multiple coordinate points are obtained, the present application can perform curve fitting on the multiple coordinate points to establish a curve relationship between the capacity loss rate and the expansion force pressure difference. The curve relationship can be as follows: Figure 6 shown.

[0087] Furthermore, in some examples, in actual applications, the present application can determine the current cycle number of the lithium iron phosphate battery, and execute step S110 when the lithium iron phosphate battery cycles to a preset number of cycles to determine the actual capacity loss value of the lithium iron phosphate battery and determine whether the battery has undergone rapid deterioration.

[0088] In some embodiments, as Figure 7 As shown, based on the actual pressure difference and the pre-built capacity loss model, the rapid degradation of the lithium iron phosphate battery is judged, including:

[0089] S302: Determine whether it is necessary to perform a rapid degradation determination process on the lithium iron phosphate battery based on the actual pressure difference;

[0090] S304: If necessary, perform a capacity loss test on the lithium iron phosphate battery and obtain an actual capacity loss value and a latest actual pressure difference;

[0091] S306: Substituting the actual capacity loss value into the capacity loss model for calculation, and obtaining a predicted pressure difference;

[0092] S308: Determine whether the lithium iron phosphate battery has experienced rapid deterioration based on the difference between the latest actual pressure difference and the predicted pressure difference.

[0093] The inventors have discovered that if a lithium iron phosphate battery experiences rapid degradation, its capacity will drop dramatically and its expansion force will increase dramatically. This application can use the battery expansion force to preliminarily determine whether a lithium iron phosphate battery is at risk of rapid degradation, and further determine whether a more in-depth rapid degradation determination process is needed.

[0094] Specifically, during the rapid degradation assessment of a lithium iron phosphate battery, the computer device can first preliminarily determine whether the lithium iron phosphate battery is at risk of rapid degradation based on the actual pressure difference. If the risk of rapid degradation is preliminarily determined, the rapid degradation assessment process can be executed on the lithium iron phosphate battery to further analyze whether the lithium iron phosphate battery is at risk of rapid degradation. Furthermore, if the risk of rapid degradation is preliminarily determined not to be present, the rapid degradation assessment process can be omitted. This allows for online testing with minimal computational effort, saving resources.

[0095] It is understood that the present application may implement step S302 in a variety of ways. The specific implementation method may be determined based on actual circumstances, such as the calculation formula for the actual pressure difference, the required calculation speed, and the required accuracy, and the present application does not impose any specific limitations thereon. For example, if the actual pressure difference is less than a preset pressure difference threshold, the computer device may determine that the rapid deterioration determination process needs to be executed. Conversely, if the actual pressure difference is greater than or equal to the preset pressure difference threshold, the computer device may determine that the rapid deterioration determination process does not need to be executed.

[0096] If it is determined that a rapid degradation judgment process needs to be performed on the lithium iron phosphate battery, a capacity loss test can be performed on the lithium iron phosphate battery to test the actual capacity loss of the battery and the pressure difference between the two expansion force peaks during the charging process of the lithium iron phosphate battery can be tested again to obtain the actual capacity loss value and the latest actual pressure difference. In some examples, the present application can perform a complete charge and discharge test on the lithium iron phosphate battery and obtain the actual capacity loss value and the latest actual pressure difference.

[0097] Since the capacity loss model is used to describe the relationship between the capacity loss rate of a lithium iron phosphate battery and the expansion force pressure difference of the battery during charging, the present application can substitute the actual capacity loss value into the capacity loss model for calculation to obtain the predicted pressure difference predicted by the capacity loss model. It can be understood that the predicted pressure difference is the expansion force pressure difference corresponding to the actual capacity loss value of the battery when the lithium iron phosphate battery does not have the problem of rapid degradation.

[0098] When the predicted pressure difference is obtained, the computer equipment can compare the predicted pressure difference with the latest actual pressure difference, and warn of rapid battery degradation based on the deviation between the two, thereby achieving accurate rapid degradation warning. In addition, this application makes a preliminary judgment based on the actual pressure difference, which can improve the efficiency of rapid degradation warning, exclude most healthy batteries at the lowest computing cost, and save overall resources.

[0099] Compared with the existing technology, this application can amplify the problem of rapid capacity decay caused by battery gas production or other side reactions, and judge whether the lithium iron phosphate battery has undergone rapid deterioration based on this, thereby achieving more accurate battery warning. For example, Figure 8 The predictions and actual measurements of the prior art are compared with those of the present application. Figure 8 It can be seen that even if the lithium iron phosphate battery has experienced rapid degradation, the difference between the predicted value and the measured value in the existing technology is small, and it is impossible to judge whether the battery has experienced rapid degradation based on the difference between the predicted value and the measured value. However, the method provided by this application is different from the existing technology. In the case of rapid degradation of the battery, the measured value deviates significantly from the predicted value. Therefore, the difference between the predicted value and the measured value can be used to judge whether the battery has experienced rapid degradation.

[0100] It should be noted that the solution of the present application does not require manual distinction between hard expansion of the battery cell (core expansion) and gas expansion of the battery cell (expansion caused by gas production). The present application can automatically determine whether the lithium iron phosphate battery is rapidly deteriorating due to gas expansion or other side reactions.

[0101] Specifically, when lithium is deposited inside the battery, gas production increases, the expansion force increases, and the battery capacity drops sharply. In this case, the actual ΔF-Qloss relationship of the lithium iron phosphate battery deviates from the normal corresponding relationship described by the capacity loss model. When gas production inside the battery cell is severe, the slope of the actual ΔF-Qloss curve will suddenly change. However, hard cell expansion is related to electrode rebound, which does not cause the problem of sudden changes in the curve slope. Therefore, judging rapid deterioration based on the difference between the actual pressure difference and the predicted pressure difference can eliminate the interference of hard cell expansion and ensure the accuracy of the judgment.

[0102] Furthermore, in some embodiments, the battery early warning prediction method provided in the present application can not only detect whether the battery has a rapid degradation problem, but also distinguish whether the rapid degradation is caused by battery gas production or other side reactions.

[0103] In some embodiments, judging whether the lithium iron phosphate battery has experienced rapid degradation based on the difference between the latest actual pressure difference and the predicted pressure difference includes:

[0104] If the difference between the latest actual pressure difference and the predicted pressure difference is greater than a second preset threshold, it is determined that the lithium iron phosphate battery has undergone rapid deterioration, and the cause of the rapid deterioration is other side reactions; wherein the second preset threshold is greater than zero, and other side reactions refer to side reactions other than battery gas production.

[0105] Specifically, when the latest actual pressure difference deviates significantly from the predicted pressure difference, and the latest actual pressure difference is greater than the predicted pressure difference, it can be determined that the lithium iron phosphate battery has experienced rapid degradation, and the cause of the rapid degradation is other side reactions, such as lithium deposition. For ease of explanation, the following embodiments use lithium deposition as an example, and the impact of other side reactions on battery expansion force besides battery gassing can be understood in the same way.

[0106] Since the first pressure value is the maximum expansion force in the first SOC range, and the first SOC range is the range of approximately SOC=30%, the first pressure value is the maximum expansion force of the lithium iron phosphate battery in a low SOC state. Since the second pressure value is the maximum expansion force in the second SOC range, and the second SOC range is the range of approximately SOC=100%, the second pressure value is the maximum expansion force of the lithium iron phosphate battery in a high SOC state.

[0107] Under low SOC conditions, lithium (Li) is normally embedded in graphite and no lithium is deposited on the anode surface. Therefore, the anode thickness does not increase abnormally, and the battery expansion force increases with the expansion of the anode electrode. Compared with the case where no rapid deterioration occurs, the increasing trend of the battery expansion force remains unchanged. Figure 9 The figure shows the variation of the first pressure value of lithium iron phosphate batteries with capacity loss in some examples. The green dots are the predicted values ​​of the first pressure value when the battery does not have a rapid degradation problem, and the red dots are the measured values ​​of the first pressure value when the battery has a rapid degradation problem caused by other side reactions. Figure 9 It can be seen that the difference between the red point and the green point is small, which is consistent with the change trend described above.

[0108] If the battery undergoes a lithium deposition side reaction, the amount of lithium embedded in the anode decreases at high SOC, and lithium is deposited on the anode surface as a single substance or as a byproduct, resulting in an abnormal increase in anode thickness. In addition to increasing the battery expansion force with the increase in anode expansion force, it also increases with the thickness of the anode plate. Because lithium deposition on the anode surface causes an abnormal increase in anode plate thickness, the slope of the battery expansion force increases at high SOC. Figure 10 The figure shows the variation of the second pressure value of lithium iron phosphate batteries with capacity loss in some examples. The green dots are the predicted values ​​of the second pressure value when the battery does not have a rapid degradation problem, and the red dots are the measured values ​​of the second pressure value when the battery has a rapid degradation problem caused by other side reactions. Figure 10 It can be seen that there is a large difference between the red point and the green point, and the red point is larger than the green point, that is, the measured value is significantly larger than the predicted value, which is consistent with the change trend described above.

[0109] Based on the changes in the first and second pressure values ​​described above, if lithium deposition occurs in the battery, the second pressure value increases while the first pressure value remains essentially unchanged. Therefore, compared to a situation where the battery does not rapidly deteriorate, rapid battery degradation caused by side reactions will increase the difference between the second and first pressure values.

[0110] So, in Figure 11 In the curve shown, the green dot is the predicted pressure difference when the battery does not have a rapid degradation problem (i.e., the predicted value output by the capacity loss model), and the red dot is the actual pressure difference when the battery has a rapid degradation problem caused by other side reactions (i.e., the measured value obtained by the test). Figure 11 It can be seen that when other side reactions occur in the battery, the red dot deviates more from the green dot, and the red dot is above the green dot, that is, the difference between the measured pressure difference and the predicted pressure difference is large, and the difference between the two is greater than the second preset threshold, and the measured pressure difference is greater than the predicted pressure difference. Based on this, it can be judged that other side reactions have occurred in the battery.

[0111] In some embodiments, judging whether the lithium iron phosphate battery has experienced rapid degradation based on the difference between the latest actual pressure difference and the predicted pressure difference includes:

[0112] If the difference between the latest actual pressure difference and the predicted pressure difference is less than a first preset threshold, it is determined that the lithium iron phosphate battery has undergone rapid deterioration, and the cause of the rapid deterioration is battery gas production; wherein the first preset threshold is less than zero.

[0113] Specifically, when a battery produces gas, the amount of gas produced increases with the number of cycles, gradually increasing the internal pressure and overall battery pressure. Whether in high or low SOC states, the battery continues to produce gas, and the battery's expansion force increases.

[0114] For example, Figure 12 The graph shows how the first pressure value of lithium iron phosphate batteries changes with capacity loss in some examples. The green dots are the predicted values ​​of the first pressure values ​​when the battery does not have a rapid degradation problem, and the red dots are the measured values ​​of the first pressure values ​​when the battery has a rapid degradation problem caused by battery gas production. Figure 13 The figure shows the variation of the second pressure value of lithium iron phosphate batteries with the loss of charge capacity in some examples. The green dots are the predicted values ​​of the second pressure value when the battery does not have a rapid deterioration problem, and the red dots are the measured values ​​of the second pressure value when the battery has a rapid deterioration problem caused by battery gas production. Figure 12 and Figure 13 It can be seen that the overall pressure value of the battery increases synchronously, and the difference between the first pressure value of the predicted value and the measured value is small, and the difference between the second pressure value is also small.

[0115] If the actual pressure difference deviates significantly from the predicted pressure difference, and the actual pressure difference is less than the predicted pressure difference, it indicates an abnormal increase in the internal pressure of the lithium iron phosphate battery. However, since the thickness of the electrode increases evenly and slowly, without sudden increases, it can be determined that the rapid deterioration is caused by battery gassing.

[0116] For example, in Figure 14 In the curve, the green point is the pressure difference when the battery does not have a rapid degradation problem (that is, the predicted value output by the capacity loss model), and the red point is the pressure difference when the battery has a rapid degradation problem caused by battery gas production (that is, the actual measured value obtained by the test). Figure 14 It can be seen that when the battery produces gas, the red point deviates more from the green point, and the red point is below the green point, that is, the difference between the measured pressure difference and the predicted pressure difference is greater than the preset threshold, and the measured pressure difference is less than the predicted pressure difference, it can be judged as rapid deterioration caused by gas production.

[0117] In some embodiments, judging whether it is necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery based on the actual pressure difference includes:

[0118] According to the actual pressure difference of the lithium iron phosphate battery during multiple charging processes, it is determined whether the actual pressure difference of the lithium iron phosphate battery has a sudden change;

[0119] If so, it is necessary to perform the rapid degradation judgment process on the lithium iron phosphate battery; otherwise, it is not necessary to perform the rapid degradation judgment process on the lithium iron phosphate battery.

[0120] In this embodiment, when the lithium iron phosphate battery has not experienced rapid deterioration, the pressure difference of the lithium iron phosphate battery will gradually decrease from a positive value to 0, and then gradually decrease from 0 to a negative value as the number of charge and discharge cycles increases. However, when the lithium iron phosphate battery experiences rapid deterioration, the pressure difference of the lithium iron phosphate battery will suddenly change. Therefore, the present application can determine whether the pressure difference of the lithium iron phosphate battery has suddenly changed based on the actual pressure difference of the lithium iron phosphate battery during multiple charging processes, thereby preliminarily determining whether the lithium iron phosphate battery needs to be judged for rapid deterioration, thereby improving the accuracy of the preliminary judgment.

[0121] If the actual pressure difference of the lithium iron phosphate battery changes suddenly, it can be preliminarily determined that the lithium iron phosphate battery is at risk of rapid degradation. In this case, it is necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery to deeply analyze whether the lithium iron phosphate battery has a rapid degradation problem and further determine the type of rapid degradation problem.

[0122] If the actual pressure difference of the lithium iron phosphate battery does not change suddenly, it can be preliminarily determined that the lithium iron phosphate battery does not have the risk of rapid degradation, and therefore the rapid degradation judgment process does not need to be executed.

[0123] In some embodiments, judging whether it is necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery based on the actual pressure difference includes:

[0124] If the absolute difference between the actual pressure difference and the predicted pressure difference is greater than the third preset threshold, it is necessary to perform the rapid degradation judgment process on the lithium iron phosphate battery; otherwise, it is not necessary to perform the rapid degradation judgment process on the lithium iron phosphate battery.

[0125] In this embodiment, a preliminary judgment can be made as to whether the lithium iron phosphate battery needs an acute deterioration warning based on the relationship between the absolute difference between the actual pressure difference and the predicted pressure difference of the lithium iron phosphate battery during a single charging process and the third preset threshold value, so as to improve the efficiency of the preliminary judgment.

[0126] Specifically, if the absolute difference between the actual pressure difference and the predicted pressure difference of the lithium iron phosphate battery during a single charge is greater than the third preset threshold, it can be preliminarily determined that the lithium iron phosphate battery is at risk of rapid degradation. In this case, it is necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery to conduct an in-depth analysis of whether the lithium iron phosphate battery has a rapid degradation problem. Conversely, if the absolute difference between the actual pressure difference and the predicted pressure difference of the lithium iron phosphate battery during a single charge is less than or equal to the third preset threshold, it can be preliminarily determined that the lithium iron phosphate battery is not at risk of rapid degradation, and the rapid degradation judgment process may not be performed on it. The predicted pressure difference can also be determined by the number of cycles corresponding to the actual pressure difference, by acting as an expansion force curve. The third preset threshold can be set as needed.

[0127] In some embodiments, capacity loss prediction of a lithium iron phosphate battery is performed based on the actual pressure difference and a pre-built capacity loss model, including:

[0128] The actual pressure difference is substituted into the capacity loss model for calculation, and the predicted capacity loss value of the lithium iron phosphate battery is obtained.

[0129] In this embodiment, since the capacity loss model is used to describe the relationship between the capacity loss rate of the lithium iron phosphate battery and the expansion force pressure difference during the charging process, when the expansion force pressure difference is determined, the capacity loss value of the battery can be accurately predicted based on the capacity loss model, and the actual SOH (State of Health) of the lithium iron phosphate battery can be corrected accordingly.

[0130] In some examples, since the actual pressure difference can be obtained only through the large-surface pressure of the lithium iron phosphate battery, this embodiment can predict the capacity loss value by monitoring the large-surface pressure of the battery, thereby improving the convenience of prediction.

[0131] In some embodiments, when a lithium iron phosphate battery is disposed in a battery pack or a battery module, obtaining a measured expansion force curve of the lithium iron phosphate battery during charging includes:

[0132] Charge the battery pack or battery module;

[0133] During charging, a pressure sensor located at a target location measures the expansion force of the battery pack or module, generating a measured expansion force curve. The target location is the center of the largest surface of the hottest battery cell in the battery pack or module. Specifically, the hottest battery cell in the battery pack or module can be determined based on pre-simulated charge and discharge conditions, and this application does not impose any restrictions.

[0134] In this embodiment, by collecting the measured expansion force curve at the center of the largest battery surface with the highest temperature in the battery pack or battery module, more reliable expansion force data can be obtained, thereby improving the accuracy and reliability of subsequent predictions and warnings.

[0135] Furthermore, in this embodiment, considering that a battery pack or battery module may include multiple lithium iron phosphate batteries, after obtaining the measured expansion force curve and calculating the actual pressure difference ΔF, ΔF can be multiplied by the battery quantity coefficient a to obtain the final actual pressure difference. This can further improve the reliability of subsequent prediction and warning.

[0136] The battery prediction and warning device provided in an embodiment of the present application is described below. The battery prediction and warning device described below and the battery prediction and warning method described above can be referenced to each other.

[0137] In some embodiments, as Figure 15 As shown, the present application provides a battery prediction and warning device 400, comprising:

[0138] A first curve acquisition module 402 is configured to acquire a measured expansion force curve of the lithium iron phosphate battery during charging; wherein the measured expansion force curve is configured to reflect changes in the expansion force of the lithium iron phosphate battery during charging as a function of SOC;

[0139] A first pressure value determination module 404 is configured to determine a maximum expansion force value of the measured expansion force curve in a first SOC interval and obtain a first pressure value; wherein the upper limit of the first SOC interval is greater than 30% and the lower limit is less than 30%;

[0140] A second pressure value determination module 406 is configured to determine a maximum expansion force of the measured expansion force curve in a second SOC interval and obtain a second pressure value; wherein the upper limit of the second SOC interval is 100% and the lower limit is greater than or equal to the SOC corresponding to the minimum expansion force value in the measured expansion force curve;

[0141] an actual pressure difference calculation module 408, configured to calculate an actual pressure difference based on the first pressure value and the second pressure value;

[0142] The prediction and warning module 410 is used to predict the capacity loss and / or judge the rapid deterioration of the lithium iron phosphate battery based on the actual pressure difference and a pre-constructed capacity loss model; wherein the capacity loss model is used to describe the relationship between the capacity loss rate of the lithium iron phosphate battery and the expansion force pressure difference during the charging process.

[0143] In some embodiments, the prediction and warning module 410 of the present application includes:

[0144] an execution judgment unit, configured to judge whether it is necessary to execute a rapid degradation judgment process for the lithium iron phosphate battery according to the actual pressure difference;

[0145] A capacity loss testing unit, configured to perform a capacity loss test on the lithium iron phosphate battery if necessary, and obtain an actual capacity loss value and a latest actual pressure difference;

[0146] a first calculation unit, configured to substitute the actual capacity loss value into the capacity loss model for calculation and obtain a predicted pressure difference;

[0147] A rapid degradation warning unit is used to determine whether the lithium iron phosphate battery has undergone rapid degradation based on the difference between the latest actual pressure difference and the predicted pressure difference.

[0148] In some embodiments, the rapid degradation warning unit of the present application includes:

[0149] The first rapid degradation judgment unit is used to determine that the lithium iron phosphate battery has undergone rapid degradation, and the cause of the rapid degradation is battery gas production, if the difference between the latest actual pressure difference and the predicted pressure difference is less than a first preset threshold value; wherein the first preset threshold value is less than zero.

[0150] In some embodiments, the rapid degradation warning unit of the present application includes:

[0151] The second rapid degradation judgment unit is used to determine that the lithium iron phosphate battery has undergone rapid degradation, and the cause of the rapid degradation is other side reactions if the difference between the latest actual pressure difference and the predicted pressure difference is greater than a second preset threshold value; wherein the second preset threshold value is greater than zero, and the other side reactions refer to side reactions other than battery gas production.

[0152] In some embodiments, the execution judgment unit of the present application includes:

[0153] a pressure mutation determination unit, configured to determine whether a sudden change occurs in the actual pressure difference of the lithium iron phosphate battery according to the actual pressure difference of the lithium iron phosphate battery during multiple charging processes;

[0154] The first judgment unit is configured to: if yes, execute a rapid degradation judgment process on the lithium iron phosphate battery; otherwise, do not execute the rapid degradation judgment process on the lithium iron phosphate battery.

[0155] In some embodiments, the execution judgment unit of the present application includes:

[0156] The second judgment unit is used to execute the rapid degradation judgment process for the lithium iron phosphate battery if the absolute difference between the actual pressure difference and the predicted pressure difference is greater than a third preset threshold; otherwise, the rapid degradation judgment process does not need to be executed for the lithium iron phosphate battery.

[0157] In some embodiments, the prediction and warning module 410 of the present application includes:

[0158] A capacity loss prediction unit is used to substitute the actual pressure difference into the capacity loss model for calculation, and obtain a predicted capacity loss value of the lithium iron phosphate battery.

[0159] In some embodiments, the battery prediction and warning device 400 of the present application further includes a model construction module, which includes:

[0160] An expansion force curve acquisition unit, used to obtain the charge expansion force curve of the sample lithium iron phosphate battery under different charge and discharge cycle numbers;

[0161] a capacity loss curve acquisition unit configured to acquire a capacity loss curve of the sample lithium iron phosphate battery, the capacity loss curve being used to describe a relationship between an actual capacity loss value of the sample lithium iron phosphate battery and a number of charge-discharge cycles;

[0162] a data fitting unit configured to perform data fitting according to the capacity loss curve and each of the charge swelling force curves, and obtain the capacity loss model.

[0163] In some embodiments, when the lithium iron phosphate battery is arranged in a battery pack or a battery module, the swelling force curve acquisition unit of the present application comprises:

[0164] a charging unit configured to charge the battery pack or the battery module;

[0165] a swelling force acquisition unit configured to acquire a measured swelling force curve of the battery pack or the battery module by a pressure sensor arranged at a target position during the charging process, wherein the target position is a center position of a highest temperature region in the battery pack or the battery module.

[0166] In one embodiment, the present application further provides a storage medium having computer readable instructions stored therein, the computer readable instructions being executed by one or more processors to cause the one or more processors to perform the steps of the battery prediction and early warning method in any embodiment.

[0167] In one embodiment, the present application further provides a computer device having computer readable instructions stored therein, the computer readable instructions being executed by one or more processors to cause the one or more processors to perform the steps of the battery prediction and early warning method in any embodiment.

[0168] Schematically, Figure 16 An internal structure schematic diagram of a computer device provided by an embodiment of the present application is shown in one example, which can be a server. Referring to Figure 16 The computer device 900 comprises a processing component 902, which further comprises one or more processors, and a memory resource represented by a memory 901, for storing instructions executable by the processing component 902, such as an application program. The application program stored in the memory 901 can comprise one or more than one module each corresponding to a set of instructions. In addition, the processing component 902 is configured to execute the instructions to perform the steps of the battery prediction and early warning method described in any embodiment above.

[0169] The computer device 900 may further include a power supply component 903 configured to perform power management of the computer device 900, a wired or wireless network interface 904 configured to connect the computer device 900 to a network, and an input / output (I / O) interface 905. The computer device 900 may operate based on an operating system stored in the memory 901, such as Windows Server™, Mac OS X™, Unix™, Linux™, Free BSD™, or the like.

[0170] Those skilled in the art will understand that the internal structure of the computer device shown in the present application is merely a block diagram of a partial structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0171] Finally, it should be noted that, in this article, relational terms such as first and second are merely used to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprise," "include," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. Without further restriction, an element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element. Herein, "one," "said," "the," and "its" may also include plural forms unless the context clearly indicates otherwise. A plurality refers to at least two, such as 2, 3, 5, or 8. "And / or" includes any and all combinations of the relevant listed items.

[0172] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referenced to each other.

[0173] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A battery prediction and warning method, characterized in that: include: Obtaining a measured expansion force curve of the lithium iron phosphate battery during charging; wherein the measured expansion force curve is used to reflect the change of the expansion force of the lithium iron phosphate battery during charging with SOC; determining a maximum expansion force value of the measured expansion force curve in a first SOC interval and obtaining a first pressure value; wherein an upper limit value of the first SOC interval is greater than 30% and a lower limit value is less than 30%; determining a maximum expansion force of the measured expansion force curve in a second SOC interval and obtaining a second pressure value; wherein an upper limit value of the second SOC interval is 100% and a lower limit value is greater than or equal to the SOC corresponding to the minimum expansion force value in the measured expansion force curve; calculating an actual pressure difference according to the first pressure value and the second pressure value; Based on the actual pressure difference and a pre-constructed capacity loss model, the capacity loss prediction and / or rapid deterioration judgment of the lithium iron phosphate battery are performed; wherein the capacity loss model is used to describe the relationship between the capacity loss rate of the lithium iron phosphate battery and the expansion force pressure difference during the charging process.

2. The method according to claim 1, characterized in that According to the actual pressure difference and the pre-built capacity loss model, the lithium iron phosphate battery is judged to be rapidly deteriorated, including: Determining whether it is necessary to perform a rapid degradation determination process on the lithium iron phosphate battery according to the actual pressure difference; If necessary, performing a capacity loss test on the lithium iron phosphate battery and obtaining an actual capacity loss value and a latest actual pressure difference; Substituting the actual capacity loss value into the capacity loss model for calculation, and obtaining a predicted pressure difference; Whether the lithium iron phosphate battery has experienced rapid deterioration is determined based on the difference between the latest actual pressure difference and the predicted pressure difference.

3. The method according to claim 2, characterized in that The determining, based on the difference between the latest actual pressure difference and the predicted pressure difference, whether the lithium iron phosphate battery has undergone rapid deterioration includes: If the difference between the latest actual pressure difference and the predicted pressure difference is less than a first preset threshold, it is determined that the lithium iron phosphate battery has undergone rapid deterioration, and the cause of the rapid deterioration is battery gas production; wherein the first preset threshold is less than zero.

4. The method according to claim 2, characterized in that The determining, based on the difference between the latest actual pressure difference and the predicted pressure difference, whether the lithium iron phosphate battery has undergone rapid deterioration includes: If the difference between the latest actual pressure difference and the predicted pressure difference is greater than a second preset threshold, it is determined that the lithium iron phosphate battery has undergone rapid deterioration, and the cause of the rapid deterioration is other side reactions; The second preset threshold is greater than zero, and the other side reactions refer to side reactions other than battery gas production.

5. The method according to claim 2, characterized in that The determining, based on the actual pressure difference, whether it is necessary to perform a rapid degradation determination process on the lithium iron phosphate battery includes: determining, based on actual pressure differences of the lithium iron phosphate battery during multiple charging processes, whether a sudden change occurs in the actual pressure difference of the lithium iron phosphate battery; If so, it is necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery; otherwise, it is not necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery.

6. The method according to claim 2, characterized in that The determining, based on the actual pressure difference, whether it is necessary to perform a rapid degradation determination process on the lithium iron phosphate battery includes: If the absolute difference between the actual pressure difference and the predicted pressure difference is greater than a third preset threshold, it is necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery; otherwise, it is not necessary to perform a rapid degradation judgment process on the lithium iron phosphate battery.

7. The method according to claim 1, characterized in that The method of predicting the capacity loss of the lithium iron phosphate battery according to the actual pressure difference and a pre-built capacity loss model includes: The actual pressure difference is substituted into the capacity loss model for calculation to obtain a predicted capacity loss value of the lithium iron phosphate battery.

8. The method according to any one of claims 1 to 7, characterized in that The steps of constructing the capacity loss model include: Obtain the charge expansion force curve of the sample lithium iron phosphate battery at different charge and discharge cycle times; Obtaining a capacity loss curve of the sample lithium iron phosphate battery; the capacity loss curve is used to describe the relationship between the actual capacity loss value of the sample lithium iron phosphate battery and the number of charge and discharge cycles; Data fitting is performed based on the capacity loss curve and each of the charge expansion force curves to obtain the capacity loss model.

9. The method according to any one of claims 1 to 6, characterized in that When the lithium iron phosphate battery is provided in a battery pack or a battery module, obtaining a measured expansion force curve of the lithium iron phosphate battery during charging includes: charging the battery pack or battery module; During the charging process, the expansion force of the battery pack or battery module is collected by a pressure sensor located at a target position, and the measured expansion force curve is obtained; wherein the target position is the center position of the highest temperature area in the battery pack or battery module.

10. A battery prediction and warning device, characterized in that: include: a first curve acquisition module, configured to acquire a measured expansion force curve of the lithium iron phosphate battery during charging; wherein the measured expansion force curve is configured to reflect changes in the expansion force of the lithium iron phosphate battery as a function of SOC during charging; a first pressure value determination module, configured to determine a maximum expansion force value of the measured expansion force curve in a first SOC interval and obtain a first pressure value; wherein an upper limit value of the first SOC interval is greater than 30% and a lower limit value is less than 30%; a second pressure value determination module, configured to determine a maximum expansion force of the measured expansion force curve in a second SOC interval and obtain a second pressure value; wherein an upper limit of the second SOC interval is 100% and a lower limit is greater than or equal to the SOC corresponding to the minimum expansion force value in the measured expansion force curve; an actual pressure difference calculation module, configured to calculate an actual pressure difference based on the first pressure value and the second pressure value; A prediction and warning module is used to predict capacity loss and / or judge rapid deterioration of the lithium iron phosphate battery based on the actual pressure difference and a pre-constructed capacity loss model; wherein the capacity loss model is used to describe the relationship between the capacity loss rate of the lithium iron phosphate battery and the expansion force pressure difference during the charging process.

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