Lithium battery aging characteristic construction method under multi-stage constant current charging mode

Abstract

The application discloses a kind of lithium battery aging characteristics construction methods under multi-section constant current charging mode, the method includes the following steps: step one: representative voltage point determination based on IC curve peak feature position and voltage interval determination based on charging voltage curve slope;Step two: the construction method of IC curve under multi-section constant current charging mode;Step three: IC curve and aging feature construction strategy based on future charging estimation assistance.This method can improve the applicability of existing aging feature construction method and provide a basis for effective estimation of SOH by solving the fluctuation caused by multi-section constant current charging mode on charging voltage curve and considering the complex use conditions in actual charging, to make up for the defects of aging feature effective construction technology under multi-section constant current charging mode.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery performance evaluation, and relates to an aging feature construction method, in particular to a lithium battery aging feature construction method suitable for a multi-stage constant current charging mode. BACKGROUND

[0002] The data-driven state of health (SOH) estimation method has attracted widespread attention because it does not need to consider the complex aging mechanism inside the battery. However, the data-driven SOH estimation method needs to construct effective aging input features. In addition, under actual application conditions, there is no large amount of aging data set for offline analysis and construction of effective aging features, and the battery has incomplete charging and discharging conditions, which all affect the effective construction of the aging features. Therefore, effective aging input features need to be constructed under the consideration of the actual application conditions of the battery to provide a basis for effective data-driven SOH modeling.

[0003] At present, there are three main types of aging feature construction methods: incremental capacity (IC) curve-based aging feature construction method, charging voltage curve-based aging feature construction method, and electrochemical impedance spectroscopy-based aging feature construction method. Compared with the IC curve-based aging feature construction method and the electrochemical impedance spectroscopy-based aging feature construction method, the charging voltage curve-based aging feature construction method does not need to perform complex data processing like the IC curve construction method, nor does it need a specific test device like the electrochemical impedance spectroscopy acquisition. It only needs to monitor the constant current charging time and other factors to construct the aging features. This method generally needs to make the battery meet the full charging and discharging conditions. However, in actual applications, random partial charging makes it difficult for the charging voltage curve-based aging feature construction method to construct effective aging features. In addition, the partial voltage interval used to construct effective aging features needs to meet certain charging conditions. Therefore, under the condition of no large amount of aging data, the charging voltage interval for constructing effective aging features needs to be obtained as much as possible under the full SOC range, so that the aging feature construction method can more easily meet the random partial charging conditions in the actual charging process.

[0004] The existing aging feature construction method is based on constant current and constant voltage charging mode to construct the aging feature and establish the SOH estimation model. However, with the popularity of electric vehicles, the development of battery technology and charging technology, the multi-section constant current fast charging mode has become the mainstream of the existing electric vehicle charging mode, so the existing aging feature construction technology needs to adapt to the multi-section constant current fast charging mode. The multi-section constant current fast charging mode uses large current charging when the battery voltage is low and small current charging when the battery voltage is high based on the charging mechanism, thereby improving the charging efficiency. However, the multi-section constant current charging mode considering the battery temperature considers the thermal safety of the battery, but this charging mode is more complex. Although the multi-section constant current charging mode can improve the charging performance of the battery, the actual voltage jump and slow rise or fall of the battery voltage after the current switching will make the charging voltage curve unstable, thereby affecting the construction of the IC curve, and further causing the construction of the aging feature and the establishment of the SOH estimation model.

[0005] In summary, the existing aging feature construction method is based on constant current and constant voltage charging mode, and the voltage curve is stable, but needs to meet certain charging conditions, and the applicability in the actual application environment is poor. For the multi-section constant current fast charging mode, there is no effective aging feature construction method in the existing research, which makes the existing aging feature construction and SOH estimation method unable to effectively match the development of the existing electric vehicles and battery charging technology. SUMMARY

[0006] In order to solve the problems in the background art, the present application provides a lithium battery aging feature construction method under multi-section constant current charging mode. The method solves the fluctuation influence of the multi-section constant current charging mode on the charging voltage curve, and improves the applicability of the existing aging feature construction method and provides a basis for effective SOH estimation under the consideration of complex use conditions in actual charging, so as to make up for the defects of the aging feature construction technology under the multi-section constant current charging mode.

[0007] The purpose of the present application is achieved by the following technical solutions:

[0008] A lithium battery aging feature construction method under multi-section constant current charging mode, comprising the following steps:

[0009] Step one: determination of representative voltage points based on IC curve peak feature position and determination of voltage interval based on charging voltage curve slope

[0010] Step one: determination of representative voltage points based on IC curve peak feature position

[0011] The representative voltage points based on the IC curve peak feature position are determined based on the following constructed peak features to obtain more voltage intervals:

[0012] Peak feature 1: construction feature based on adjacent peaks

[0013]

[0014] In the above formula, F p is a representative voltage point constructed based on the construction feature of adjacent peaks, U p is a voltage point of the IC curve, U a and U b are the left end point and the right end point of the voltage interval, respectively, represents adjacent maximum points of the IC curve (i.e., adjacent IC peaks: U p,max,1 and U p,max,2 ), and f represents the IC value corresponding to the voltage point;

[0015] Peak feature 2: construction feature based on adjacent valleys

[0016]

[0017] In the above formula, F v is a representative voltage point constructed based on the construction feature of adjacent valleys, represents adjacent minimum points of the IC curve (i.e., adjacent IC valleys: U p,min,1 and U p,min,2 );

[0018] Step 1-2: determination of voltage interval based on the slope of the charging voltage curve

[0019] Based on the representative voltage points determined in step 1-1, the voltage interval containing these representative voltage points is determined based on the change in the slope of the charging voltage curve under the consideration of partial charging conditions, wherein:

[0020] ① For a straight line, if the slope of the charging voltage curve changes little in a certain voltage interval, it is determined that the voltage curve under this voltage interval is approximately a straight line, and at this time, the interval of this voltage curve is determined as the voltage interval for constructing the aging feature;

[0021] ② For a circular arc, if the slope of the tangent line of the point on the charging voltage curve generally shows a trend of increasing or decreasing, it is determined that the voltage curve under this voltage interval is approximately a circular arc, and at this time, the interval of this voltage curve is determined as the voltage interval for constructing the aging feature;

[0022] Step 2: construction method of IC curve under multi-section constant current charging mode

[0023] Step 2-1: monitoring of current switching

[0024] Current switching is determined based on the absolute difference value of the front and rear currents:

[0025] |ΔI(k)|≥δ

[0026] In the above formula, ΔI(k) = I(k) - I(k-1), k is the current sampling time, I(k) is the current at the current sampling time, I(k-1) is the current at the previous sampling time, and δ is the current switching threshold value set based on the charging mechanism;

[0027] Step two: monotonic voltage curve acquisition without voltage repetitive feedback process

[0028] Based on the voltage curve at the current charging current obtained in step two one, considering the fluctuation of the voltage curve caused by the polarization reaction of the battery after current switching, the voltage curve at the current charging current is intercepted based on the charging voltage point before current switching, so as to obtain a monotonic curve without voltage repetitive feedback process:

[0029]

[0030] In the above formula, I a is the current before current switching, is the cut-off voltage at the I a charging stage, I b is the current after current switching, is the differential value of the voltage at the current time, is the obtained battery voltage without voltage repetitive feedback process;

[0031] Step two three: construction of IC curve under equal charging capacity

[0032] Step two three one: assuming that the current size of the initial charging current stage is I0, and the charging interval capacity set for constructing the IC curve is ΔQ0, then for the current size I b of the current charging current stage after current switching, the charging capacity interval ΔQ b for constructing the IC curve at the current charging stage is:

[0033]

[0034] In the above formula, I0 is the current size of the initial charging current stage, and ΔQ0 is the charging interval capacity set for constructing the IC curve;

[0035] Step two three two: based on the voltage curve based on sampling time obtained in step two two, in order to further obtain the voltage point for constructing the IC curve, based on the ΔQ b of the current charging stage, the voltage curve based on sampling time is interpolated in proportion to obtain the voltage point for finally constructing the IC curve:

[0036]

[0037] In the above formula, k1 and k2 are respectively the current charging capacity based on the charging capacity interval ΔQ b the end point of the interval segment, the determined voltage value for constructing the IC curve, υ is the proportionality coefficient for determining the voltage interval;

[0038] Step 233: Based on the U and Q obtained in steps 231 and 232 for IC construction, the IC curve is constructed based on the following formula:

[0039]

[0040] In the above formula, the determined differential value for constructing the IC curve voltage point;

[0041] Step 3: IC curve and aging feature construction strategy based on future charging estimation assistance

[0042] Step 3-1: Battery temperature calculation based on the two-state battery thermal model and battery terminal voltage calculation based on the Rint electrical model

[0043] The discretized battery internal and external temperature calculation equation and the battery terminal voltage calculation equation are as follows:

[0044]

[0045] U t (k) = U OCV (k) - I(k)R0

[0046] In the above formula, ΔT is the interval size of the sampling, T c is the internal temperature of the battery, T s is the external temperature of the battery, R c is the internal thermal resistance of the battery, R s is the external thermal resistance of the battery to the external environment, C c is the heat capacity inside the battery, C s is the heat capacity of the battery shell, Q is the heat generation, T f is the ambient temperature, U t is the terminal voltage of the battery, U OCV is the open-circuit voltage of the battery, I is the current of the battery, and R0 is the ohmic internal resistance of the battery;

[0047] Step 3-2: Future current selection based on charging current mechanism

[0048] Based on the battery internal and external temperature and the battery terminal voltage calculated in step 3-1, the estimated charging current at the next time based on the charging mechanism is obtained:

[0049]

[0050] In the above formula, I k is the determined charging current, Table 2-D is a charging mechanism based on the voltage and temperature of the battery; is the terminal voltage of the battery at the last time; is the surface temperature of the battery at the last time;

[0051] wherein the predicted charging current at the next time is used for the calculation of Q in the two-state battery thermal model and the calculation of the terminal voltage in the Rint model;

[0052] Step three: construction of IC curve and aging characteristics in multi-section constant current charging mode

[0053] Based on the predicted future charging voltage curve, the IC curve is constructed based on the IC curve construction method of step two, and the voltage interval determination method of step one provides a basis for the construction of the aging characteristics.

[0054] Compared with the prior art, the present application has the following advantages:

[0055] 1. The present application expands the construction of aging characteristics under different charging current modes. Since constant current constant voltage charging can be regarded as a special multi-section constant current charging mode, the method proposed in the present application has wide applicability and is more suitable for the construction of aging characteristics in current actual electric vehicles, and provides a basis for data-driven SOH estimation.

[0056] 2. The voltage interval determination method for effective aging characteristics construction of the present application does not require a large amount of aging data set for analysis and processing, and is suitable for the construction of aging characteristics under different charging modes, different charging environments, and different battery types.

[0057] 3. The IC curve and aging characteristics auxiliary construction strategy based on the charging mechanism can further expand the application range of existing methods, making the method proposed in the present application more suitable for practical application, and being able to provide a basis for battery fault diagnosis, range prediction, state of charge estimation, etc., which is beneficial to the safe driving of electric vehicles. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 is a flow chart of the lithium battery aging characteristics construction method in multi-section constant current charging mode;

[0059] Figure 2 is the other peak characteristics constructed;

[0060] Figure 3 is the voltage interval determination principle based on the change of the slope of the charging voltage curve;

[0061] Figure 4 is the current curve and voltage curve under the multi-stage constant current charging mode;

[0062] Figure 5 is the IC curve constructed under the multi-stage constant current charging mode;

[0063] Figure 6 is the dual-state battery thermal model and Rint electrical model used for future charging estimation;

[0064] Figure 7 is the basic principle of future charging estimation;

[0065] Figure 8 is the IC curve constructed based on the proposed IC curve construction strategy;

[0066] Figure 9 is the coordinate system constructed for aging characteristic construction;

[0067] Figure 10 is the battery temperature estimated based on the battery thermal model;

[0068] Figure 11 is the comparison chart of the IC curve constructed based on future temperature estimation and the IC curve constructed based on actual charging. DETAILED DESCRIPTION

[0069] The technical solutions of the present application will be further described below in combination with the drawings, but are not limited thereto, and any modification or equivalent replacement to the technical solutions of the present application without departing from the spirit and scope of the technical solutions of the present application shall be covered in the protection scope of the present application.

[0070] The present application provides an aging characteristic construction method under a multi-stage constant current charging mode, as shown in Figure 1 The method comprises the following steps:

[0071] Step one: determination of representative voltage points based on peak characteristic positions of IC curves and determination of voltage intervals based on slopes of charging voltage curves

[0072] Step one: determination of representative voltage points based on peak characteristic positions of IC curves

[0073] IC curve reflects the key information of battery internal state more sensitively by transforming the voltage plateau of traditional voltage curve into a peak feature, which provides an effective tool for analyzing the battery aging mechanism and performance changes. With the aging of the battery, the peak features of IC curve will change significantly, so the voltage interval containing the peak features is the voltage interval for constructing effective aging features from the dimension of IC curve. And IC curve is from different angles to describe the conventional charging voltage curve, so the effective aging features can also be constructed in the corresponding voltage interval of the conventional charging voltage curve. Since the peak or valley of IC curve has maximum or minimum points, the representative voltage points contained in the voltage interval for constructing aging features can be determined based on the peak features of IC curve. And considering that as many voltage intervals as possible for constructing effective aging features should be obtained as possible in the full SOC range, the determination of representative voltage points based on IC curve is no longer limited to the monitoring of peaks or valleys, and more representative voltage points are determined based on other peak features constructed as shown in Figure 2

[0074] Peak feature 1: constructed feature based on adjacent peaks

[0075]

[0076] In the above formula, F p is the representative voltage point of the constructed feature based on adjacent peaks, U p is the voltage point of IC curve, U a and U b are the left end point and the right end point of the voltage interval respectively, indicates the adjacent maximum points of IC curve (i.e. adjacent IC peaks: U p,max,1 and U p,max,2 ), and f indicates the IC value corresponding to the voltage point.

[0077] Peak feature 2: constructed feature based on adjacent valleys

[0078]

[0079] In the above formula, F v is the representative voltage point of the constructed feature based on adjacent valleys, indicates the adjacent minimum points of IC curve (i.e. adjacent IC valleys: U p,min,1 and U p,min,2 ).

[0080] Step one two: voltage interval determination based on charging voltage curve slope

[0081] ​Based on the representative voltage points determined in step one, voltage intervals containing these representative voltage points are determined based on the change of the slope of the charging voltage curve under the consideration of partial charging condition.

[0082] Considering the partial charging condition in practical application, the voltage curve segment of the partial charging voltage interval should still be able to map the charging voltage curve in the complete interval. The circle or straight line has good properties, that is, any arc or line segment on the circle or straight line can still map the complete circle or straight line. The slope change of the circle or straight line has obvious change characteristics, as shown in the following table, in particular: Figure 3

[0083] ① For a straight line, its slope is kept unchanged. Therefore, if the slope change of the charging voltage curve in a certain voltage interval is very small, it can be judged that the voltage curve under this voltage interval is approximately a straight line, and at this time the interval of this voltage curve can be determined as the voltage interval for constructing the aging feature.

[0084] ② For an arc, consider the arc curve on the unit circle (r = 1) with the origin (O(0, 0)) as the center. Any point on the unit circle can be represented by polar coordinates (cos θ, sin θ), where θ represents the angle from the x-axis counterclockwise to OP. The tangent slope k of point P on the unit circle is:

[0085]

[0086] In the above formula, S k is the tangent slope of the point on the circle, and θ represents the angle from the x-axis counterclockwise to OP.

[0087] Therefore, for S k , the derivative of θ has the following relationship.

[0088]

[0089] For the above formula, since sin 2 θ is always positive for θ ≠ nπ, the increase or decrease of k is completely determined by -cos2θ, so the following relationship can be obtained:

[0090]

[0091] Therefore, if the slope change of the tangent line of the point on the voltage curve generally shows a trend of increasing or decreasing, it can be judged that the voltage curve under this voltage interval is approximately an arc, and at this time the interval of this voltage curve can be determined as the voltage interval for constructing the aging feature.

[0092] Step 2: Construction method of IC curve under multi-segment constant current charging mode

[0093] ​Based on the representative voltage point determination strategy of IC curve peak feature position in step one and the voltage interval determination strategy based on the slope of the charging voltage curve, the construction of the aging feature first needs to construct the IC curve to determine the voltage interval. For multi-stage constant current charging mode, such as Figure 4 As shown, due to the influence of the internal polarization reaction of the battery, the current switching will make the charging voltage curve no longer stable, which will cause the constructed IC curve to be abnormal, as shown in Figure 5 Therefore, an effective IC curve construction method needs to be designed under the multi-stage constant current charging mode.

[0094] Step two one: monitoring of current switching

[0095] Due to the influence of the internal polarization reaction of the battery, the current switching will cause fluctuations in the charging voltage response curve. Therefore, first, the switching of the current is monitored to obtain the voltage curve under the current charging current, providing a basis for subsequent IC curve construction. The specific monitoring strategy is based on the absolute difference value of the current before and after the switching, that is:

[0096] |ΔI(k)|≥δ

[0097] In the above formula, ΔI(k) = I(k) - I(k-1). Wherein, k is the sampling time, I(k) is the current size at the current sampling time, I(k-1) is the current size at the last sampling time, and δ is the current switching threshold set based on the charging mechanism.

[0098] Step two two: monotonic voltage curve without voltage repeated feedback process

[0099] Based on the voltage curve under the current charging current obtained in step two one, considering the fluctuations in the voltage curve caused by the polarization reaction of the battery after the current switching, the voltage curve under the current charging current is intercepted based on the charging voltage point before the current switching, to ensure that a monotonic curve without voltage repeated feedback process is obtained.

[0100]

[0101] In the above formula, I a is the current before the current switching, is the cutoff voltage under the I a charging stage, I b is the current after the current switching, is the difference value of the voltage at the current time, is the obtained battery voltage without voltage repeated feedback process.

[0102] Step two three: construction of IC curve under equal charging capacity

[0103] To construct the stable IC curve, based on the stable voltage curve obtained in step two, the voltage value and the charge capacity value for constructing the IC curve are obtained based on the equal charge capacity.

[0104] Assuming that the current size of the initial charging current stage is I0, the set charge interval capacity for constructing the IC curve is ΔQ0, then for the current charging current stage, the current size I b The charge capacity interval ΔQ b for the current charging stage for constructing the IC curve can be obtained.

[0105]

[0106] In the above formula, I0 is the current size of the initial charging current stage, ΔQ0 is the set charge interval capacity for constructing the IC curve, and ΔQ b is the charge capacity interval for the current charging stage for constructing the IC curve.

[0107] And in the voltage curve based on the sampling time obtained in step two, to further obtain the voltage point for constructing the IC curve, based on the ΔQ b The voltage curve based on the sampling time is interpolated in equal proportion to obtain the voltage point for constructing the IC curve, that is:

[0108]

[0109] In the above formula, k1 and k2 are the end points of the interval segment where the current charging capacity is based on the charge capacity interval ΔQ b , The determined voltage value for constructing the IC curve is υ, and the proportion factor for determining the voltage in the interval is calculated as:

[0110]

[0111] In the above formula, T is the charging time of the current charging stage, and Q is the charge capacity.

[0112] Then based on the U and Q obtained in step three for constructing the IC curve, the IC curve is constructed based on the following formula:

[0113]

[0114] In the above formula, The determined differential value of the voltage point for constructing the IC curve is υ.

[0115] Step three: IC curve and aging feature construction strategy based on future charging estimation assistance

[0116] The initial SOC range for charging in practical applications is random, and steps one to two need to satisfy at least one complete SOC charging cycle to build a complete IC curve for the voltage interval selection strategy in step one. In addition, the multi-section constant current charging mode considers the temperature and voltage of the battery based on the charging mechanism to intelligently determine and select the required charging current size at the next time. Therefore, if the future temperature change and future voltage change of the battery can be obtained, the IC curve can be constructed based on the future charging voltage curve and the constructed features can be calculated.

[0117] Step three one: battery temperature calculation based on the dual-state battery thermal model and battery terminal voltage calculation based on the Rint electrical model

[0118] As shown in Figure 6 , the dual-state battery thermal model is selected for battery temperature calculation, and the discrete battery internal and external temperature calculation equation and the terminal voltage calculation equation are as follows:

[0119]

[0120] U t (k)=U OCV (k)-I(k)R0

[0121] In the above formula, ΔT is the interval size of the sampling time, T c is the internal temperature of the battery, T s is the external temperature of the battery, R c is the internal thermal resistance, R s is the external thermal resistance of the battery and the external environment, C c is the internal heat capacity of the battery, C s is the heat capacity of the battery shell, Q is the heat generation, T f is the ambient temperature, U t is the terminal voltage of the battery, U OCV is the open-circuit voltage of the battery, I is the current of the battery, and R0 is the ohmic internal resistance of the battery.

[0122] Step three two: future current selection based on the charging current mechanism

[0123] As shown in Figure 7 , based on the calculated internal and external temperatures of the battery and the terminal voltage of the battery in step three one, the estimated charging current at the next time can be obtained based on the charging mechanism:

[0124]

[0125] In the above formula, I k is the determined charging current, Table 2-Dfor a battery-based charging mechanism, for the terminal voltage of the battery at the previous time, for the surface temperature of the battery at the previous time.

[0126] where the predicted charging current at the next time is used for the calculation of Q in the two-state battery thermal model and the calculation of the terminal voltage in the Rint model.

[0127] Step three: construction of IC curve and aging signature in multi-stage constant current charging mode

[0128] Based on the predicted future charging voltage curve, the IC curve is constructed based on the IC curve construction method of step two, and the voltage interval determination method of step one provides the basis for the construction of the aging signature.

[0129] Embodiment:

[0130] This embodiment is verified based on a ternary lithium battery. Table 1 is the basic information of the selected battery.

[0131] Table 1. Battery information

[0132]

[0133] The charging mechanism of the above ternary lithium battery is shown in Table 2:

[0134] Table 2. Charging mechanism

[0135]

[0136] The IC curve constructed based on the proposed IC curve construction strategy is shown in Figure 8 , and the representative voltage points based on the peak characteristics of the constructed IC curve are shown in Table 3 as follows:

[0137] Table 3. Representative voltage points based on peak characteristics

[0138]

[0139] The voltage interval for constructing the aging signature determined based on the above determined representative voltage points is shown in Table 4 as follows:

[0140] Table 4. Voltage interval determined based on representative voltage points based on peak characteristics

[0141]

[0142] Based on the above determined voltage interval, the aging signature is constructed as Figure 9As shown, the coordinate axis is constructed with time as the horizontal coordinate and voltage as the vertical coordinate, the included angle of the charging curve (arc AD or chord AD) with the X-axis and Y-axis forming a right triangle is α and β respectively, the length of AD formed (feature 1), the slope of AD formed (feature 2), and the sum of the two sides of the right triangle formed by AD and the coordinate axis (feature 3) are selected as the aging features, and the correlation between the aging features and the reference capacity is shown in Table 5:

[0143] Table 5. Pearson correlation coefficient value between the constructed features and the capacity

[0144]

[0145] As can be seen from the above table, the Pearson correlation coefficient value constructed is high, which proves that the determination strategy of the voltage interval and the construction strategy of the aging features are effective.

[0146] The temperature estimation results of the battery shown in Table 1 are shown in Figure 10 As shown, the specific error size of the estimation is shown in Table 6.

[0147] Table 6. Battery temperature estimation error

[0148]

[0149] The comparison of the IC curve constructed based on the future temperature prediction and the IC curve constructed based on the actual charging is shown in Figure 11 As can be seen from the above table, the IC curve constructed based on the actual charging current is similar to the IC curve constructed based on the future current prediction, which can provide useful information for the construction of the future IC curve and the construction of the aging features.

Claims

1. A method of constructing an aging characteristic of a lithium battery in a multi-stage constant current charging mode, characterized by The method comprises the following steps: Step one: representative voltage point determination based on IC curve peak feature position and voltage interval determination based on charging voltage curve slope Step one one: representative voltage point determination based on IC curve peak feature position Determine representative voltage points based on IC curve peak feature position to obtain more voltage intervals based on the following constructed peak features: Peak feature 1: based on the structural characteristics of adjacent peaks In the above formulae, is a representative voltage point constructed based on the neighboring peaks, is a voltage point of the IC curve, and are left and right endpoints of the voltage interval, respectively, denotes the neighboring maximum points of the IC curve, i.e., the neighboring IC peaks: and , denotes the IC value corresponding to the voltage point. Peak feature 2: based on the structural characteristics of adjacent valleys In the above formula, is a representative voltage point constructed based on the features of adjacent valleys, represents the minimum points adjacent to the IC curve, i.e., adjacent IC valleys: and ; Step one two: voltage interval determination based on charging voltage curve slope Based on the representative voltage points determined in step one one, determine the voltage intervals containing these representative voltage points based on the changes in the charging voltage curve slope under the consideration of partial charging conditions; Step two: construction method of IC curve under multi-section constant current charging mode Step two one: current switching monitoring Determine current switching based on the absolute difference value of the current before and after the current switching: In the above formula, , is the current sampling time, is the current size at the current sampling time, is the current size at the previous sampling time, is the current switching threshold set based on the charging mechanism; Step two two: monotonic voltage curve acquisition without voltage repeated feedback process Based on the voltage curve under the current obtained in step two one, considering the fluctuation of the voltage curve caused by the polarization reaction of the battery after the current switching, intercept the voltage curve under the current based on the charging voltage point before the current switching, to ensure that the monotonic curve without voltage repeated feedback process is obtained: In the above formula, is the charging current before current switching, is the current charging current after current switching, is the cut-off voltage under the charging phase, is the charging current before current switching, is the differential value of the voltage at the current moment, is the obtained battery voltage without voltage repetitive feedback process; Step two three: construction of IC curve under equal charging capacity Step two three one: assuming the current size of the initial charging current stage is , the charging interval capacity set for constructing the IC curve is , then for the current size of the current charging current stage after the current is switched , the charging capacity interval for constructing the IC curve in the current charging stage is obtained as : In the above formula, is the current magnitude for the initial charging current phase, is the set charging interval capacity for constructing the IC curve; Step two three two: Based on the voltage curve based on sampling time obtained in step two two, for further obtaining the voltage points used to construct the IC curve, based on the charging of this stage Interpolate the voltage curve based on sampling time in equal proportion to obtain the final voltage points used to construct the IC curve: In the above formulae, and are the current charge capacity based on the charge capacity interval the end point of the interval segment in which the current charge capacity is located, is the determined voltage value for constructing the IC curve, is the proportionality factor for determining the interval in which the voltage is located. Step two three three: based on the U and Q obtained in step two three one and step two three two for IC construction, construct the IC curve based on the following formula: In the above formula, is the determined differential value for constructing the IC curve voltage point; Step three: IC curve and aging feature construction strategy based on future charging estimation assistance Step three one: battery temperature calculation based on the two-state battery thermal model and battery terminal voltage calculation based on the Rint electrical model The discretized battery internal and external temperature calculation equation and the battery terminal voltage calculation equation are as follows: in the above formula, is the interval size of the sampling, is the internal temperature of the battery, is the external temperature of the battery, is the internal thermal resistance of the battery, is the external thermal resistance of the battery to the environment, is the heat capacity inside the battery, is the heat capacity of the battery housing, is the heat generation, is the ambient temperature, is the terminal voltage of the battery, is the open-circuit voltage of the battery, is the current of the battery, is the ohmic internal resistance of the battery; Step three two: future current selection based on charging current mechanism Based on the battery internal and external temperature and the battery terminal voltage calculated in step three one, obtain the estimated charging current at the next time based on the charging mechanism: In the above formula, is the determined charging current, is a charging mechanism based on the voltage and temperature of the battery; is the terminal voltage of the battery at the previous time; is the surface temperature of the battery at the previous time; wherein the predicted charging current at the next time is used for the calculation of Q in the two-state battery thermal model and the calculation of the terminal voltage in the Rint model; Step three three: construction of IC curve and aging feature under multi-section constant current charging mode Based on the predicted future charging voltage curve, construct the IC curve based on the IC curve construction method of step two, and provide a basis for the construction of the aging feature based on the voltage interval determination method of step one.

2. The method of claim 1, wherein the lithium battery aging characteristic construction method in a multi-stage constant current charging mode is characterized by In step one two, ① for a straight line, if the slope of the charging voltage curve changes little in a certain voltage interval, it is judged that the voltage curve in this voltage interval is approximately a straight line, and at this time the interval of this voltage curve is determined as the voltage interval for constructing the aging feature; ② for a circular arc, if the slope of the tangent line on the charging voltage curve generally shows a trend of increasing or decreasing, it is judged that the voltage curve in this voltage interval is approximately a circular arc, and at this time the interval of this voltage curve is determined as the voltage interval for constructing the aging feature.

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