Lithium ion battery internal real-time temperature monitoring method based on online impedance

Abstract

The invention relates to a lithium ion battery internal real-time temperature monitoring method based on online impedance. The method comprises the following steps: performing electrochemical impedance spectroscopy test on the lithium ion battery on line, determining fitting coefficients A, B and C in a temperature and impedance relational expression on the basis of battery type and model information, and calculating the internal temperature of the battery at the same time. Nondestructive monitoring of the internal temperature of the battery can be realized, the battery does not need to be disassembled, the influence on the electrochemical process and state in the battery is small, the accuracy is high, and the dynamic response is fast.

Description

Technical field:

[0001] The present invention belongs to the technical field of lithium ion battery temperature management, and in particular relates to a method for monitoring the real-time temperature inside a lithium ion battery based on online impedance. Background technology:

[0002] Lithium-ion batteries are widely used in energy storage stations, new energy vehicles, and various electronic devices due to their advantages such as long cycle life, high energy density, low self-discharge rate, and no memory effect. However, lithium-ion batteries still face many problems in the application process. Lithium-ion batteries are sensitive to temperature changes, and temperature will affect the performance of the battery. At high temperatures, the electrode material will decompose, which can easily induce safety accidents. When the temperature changes, the maximum available capacity of the lithium-ion battery will also change, which will cause errors in the online estimation of the battery's state of charge (SOC) and state of health (SOH). In severe cases, it will cause the battery management system (BMS) algorithm to not converge, endangering the user's personal safety. Therefore, during the use of lithium-ion batteries, being able to achieve accurate online estimation of the internal temperature is one of the essential key technologies.

[0003] At present, the temperature monitoring of lithium-ion batteries is achieved by installing thermocouples on the surface of the battery. However, due to the structural characteristics of lithium-ion batteries, the thermal conductivity coefficients in all directions vary greatly. This method has low estimation accuracy and cannot respond promptly when the battery temperature changes rapidly. Implanting thermocouples inside the battery can also monitor the internal temperature of the battery, but this method is affected by the electrochemical corrosion environment inside the battery, which will destroy the original structure of the battery and affect the battery performance. The internal temperature of lithium-ion batteries can be monitored based on electrochemical impedance spectroscopy. However, the traditional method is based on the assumption that the overall temperature of the battery is consistent when the battery is in a steady-state offline state. However, when the battery is under different charging and discharging conditions, the heat transfer between the inside and the surface of the battery will be asynchronous, and there may be a high radial difference between the surface temperature and the internal temperature. At this time, the temperature monitored based on the electrochemical impedance spectroscopy may have a large error.

[0004] CN116576987A is a method for predicting the internal temperature of a battery based on variable frequency impedance measurement. The method for predicting the internal temperature of a battery proposed in the invention is when the battery is in an offline state, and does not consider the online internal temperature estimation when the battery is in different working conditions of charging and discharging.

[0005] CN112578298A battery temperature estimation method, device, electronic device and storage medium, the invention also estimates the internal temperature of the battery in an offline state, and also considers the temperature distribution model of batteries of different shapes and sizes, which is cumbersome to implement and cannot be applied online Summary of the invention:

[0006] The purpose of the present invention is to address the above-mentioned problems existing in the existing methods for monitoring the internal temperature of lithium-ion batteries, and disclose a method for monitoring the real-time internal temperature of lithium-ion batteries based on online impedance. The method is: to perform electrochemical impedance spectroscopy test on the lithium-ion battery online, and then determine the fitting coefficients A, B and C in the temperature and impedance relationship: T = A*exp(-B*-Z″) + C based on the battery type and model information, and calculate the internal temperature of the battery at the same time. The present invention can realize non-destructive monitoring of the internal temperature of the battery without disassembling the battery, has little effect on the electrochemical process and state inside the battery, has high accuracy, and fast dynamic response.

[0007] The specific technical solution adopted by the present invention is:

[0008] A method for monitoring the real-time temperature inside a lithium-ion battery based on online impedance comprises the following steps:

[0009] Step 1: Input the type and model information of the battery into the microcontroller of the monitoring device;

[0010] Step 2: The working electrode and the sensitive electrode of the impedance test device are connected to the positive electrode of the battery, and the reference electrode and the auxiliary electrode are connected to the negative electrode of the battery. The electrochemical impedance spectroscopy test of the battery is performed online, and the impedance data is obtained;

[0011] Step 3: The impedance testing device transmits the acquired impedance data to the single chip microcomputer in real time;

[0012] Step 4: The single chip microcomputer converts the impedance data into the internal temperature of the battery and outputs it in real time based on the type and model information of the battery and the measured impedance data using the internal temperature online estimation mathematical model corresponding to the battery in the database;

[0013] The monitoring device comprises a data processing module and an impedance testing device;

[0014] The data processing module is a single chip microcomputer, which is provided with information on the type and model of the battery, as well as fitting coefficients A, B, and C of a corresponding mathematical model for online estimation of the internal temperature of the lithium-ion battery.

[0015] The temperature range of the monitored battery is -10 to 50°C.

[0016] The method for establishing a mathematical model database for online estimation of the internal temperature of a lithium-ion battery comprises the following steps:

[0017] Step 1, select the type and model of lithium-ion battery and determine the actual capacity of the battery: according to the standard charge and discharge requirements in the battery specification, take a fresh battery at room temperature (25°C) and perform 3 to 5 standard charge and discharge cycles to determine the actual discharge capacity of the battery at room temperature;

[0018] Under steady-state conditions, an impedance test device is used to perform electrochemical impedance spectroscopy tests on the battery at different temperatures and different SOCs. First, a fully charged battery is discharged at a constant current at room temperature, and the battery SOC is controlled to 80%. A thermocouple is attached to the battery surface to monitor the battery surface temperature in real time, and the temperature of the thermostat is controlled to -10°C. The battery is placed in the thermostat for 3 to 4 hours. At this time, the temperature monitored by the thermocouple is the internal temperature of the lithium-ion battery. After the internal and external temperatures of the battery reach equilibrium, the battery is subjected to an electrochemical impedance spectroscopy test, with an excitation current of 100mA and an excitation frequency range of 10000 to 0.01Hz. After the test, the battery SOC is controlled to 80%, and the temperature of the thermostat is adjusted to 0°C, 10°C, 20°C, 30°C, 40°C, and 50°C, respectively. The battery is also The battery was allowed to stand for 3 to 4 hours at the corresponding temperature to allow the battery to reach thermal equilibrium, and electrochemical impedance spectroscopy tests were performed to obtain electrochemical impedance spectroscopy data at different temperatures under 80% SOC; after the 80% SOC and different temperature tests were completed, the temperature of the thermostat was adjusted to 25°C, and after the battery reached thermal equilibrium, the battery was discharged at a constant current to allow the battery SOC to be 70%, and the temperature of the thermostat was adjusted to -10°C. After the battery reached thermal equilibrium, the battery was subjected to an electrochemical impedance spectroscopy test, and the above steps were repeated until all electrochemical impedance spectroscopy tests at 70% SOC and different temperatures were completed; the battery SOC was controlled to be 60%, 50%, 40%, 30%, and 20%, and the above process was repeated at the corresponding SOC and different temperatures until all SOCs and all temperatures were tested;

[0019] Step 2, determine the frequency range that is sensitive to temperature changes but relatively insensitive to SOC changes;

[0020] Select three temperatures -10℃, 20℃, 50℃, corresponding to the imaginary part of impedance at different SOCs, and three SOCs: 20%, 50%, 80%, and compare the imaginary part of impedance at different temperatures to determine the frequency range in which the imaginary part of impedance is sensitive to temperature changes but relatively insensitive to SOC changes;

[0021] Step 3, after determining the frequency range, it is necessary to determine the optimal characteristic frequency point. In the selected frequency range, 8 to 12 frequency points are taken between each decade in logarithmic form to extract the imaginary part of the impedance and the corresponding temperature at different temperatures and different SOCs, respectively, according to the formula:

[0022] T=A*exp(-B*-Z″)+C

[0023] Where T is the internal temperature of the battery, -Z″ is the imaginary part of the impedance, and A, B, and C are fitting coefficients;

[0024] Obtain the fitting coefficients A, B, and C of the mathematical model for online estimation of the internal temperature of lithium-ion batteries of this type and model;

[0025] Step 4, uploading the fitting coefficients A, B, and C of the online estimation mathematical model of the internal temperature of the lithium-ion battery of the type and model to the single chip microcomputer;

[0026] Step 5, select other types and models of lithium-ion batteries, repeat steps 1 to 4 for each model of battery, obtain the fitting coefficients A, B, and C of the corresponding mathematical model for online estimation of the internal temperature of the lithium-ion battery, and finally establish a database of the mathematical model for online estimation of the internal temperature of the lithium-ion battery.

[0027] The types and models of the lithium-ion batteries are NCM111 cylindrical 18650, NCM523 cylindrical 18650, NCM811 cylindrical 18650, LFP cylindrical 18650, NCM111 soft pack, NCM523 soft pack, NCM811 soft pack or LFP soft pack.

[0028] The beneficial effects of the present invention are:

[0029] 1. This monitoring method can realize non-destructive monitoring of the internal temperature of the battery without disassembling the battery, has little impact on the electrochemical process and state inside the battery, has high accuracy and fast dynamic response;

[0030] 2. This monitoring method can realize online monitoring of the internal temperature of the battery, and can monitor the internal temperature of the battery in real time during the charge and discharge process of the battery at different rates. Compared with the offline estimation method, this method has higher accuracy and more practical application value;

[0031] 3. This monitoring method can realize online monitoring of the internal temperature of batteries of different types and models. It only needs to perform electrochemical impedance spectroscopy test on the battery through an impedance testing device, and the impedance testing device can transmit the obtained impedance data to the single-chip microcomputer. At the same time, the single-chip microcomputer can determine the relationship between the impedance data and the internal temperature of the battery according to the input battery type and model, using the established database, and convert the impedance data into the internal temperature of the battery and output it in real time. Description of the drawings:

[0032] Figure 1 Schematic diagram of an experimental device for real-time temperature monitoring inside a lithium-ion battery using online impedance according to the present embodiment;

[0033] Figure 2 It is a flow chart of a real-time temperature monitoring method for a lithium-ion battery based on online impedance according to the present invention;

[0034] Figure 3 is the imaginary part of the impedance of the lithium-ion battery of this embodiment at different SOCs at -10°C;

[0035] Figure 4 is the imaginary part of the impedance of the lithium-ion battery of this embodiment at different SOCs at 20° C.;

[0036] Figure 5 is the imaginary part of the impedance of the lithium-ion battery of this embodiment at different SOCs at 50° C.;

[0037] Figure 6 is the imaginary part of the impedance of the lithium-ion battery of this embodiment at different temperatures when the SOC is 20%;

[0038] Figure 7 is the imaginary part of the impedance of the lithium-ion battery of this embodiment at different temperatures when the SOC is 50%;

[0039] Figure 8 is the imaginary part of the impedance of the lithium-ion battery of this embodiment at different temperatures when the SOC is 80%;

[0040] Fig. 9 is the correlation between the temperature and the imaginary part of the impedance of the lithium-ion battery of this embodiment at different frequencies;

[0041] Fig.10 Schematic diagram of the relationship between the temperature and the imaginary part of impedance of the lithium-ion battery of this embodiment when the frequency is 398 Hz. Specific implementation method:

[0042] The experimental device of real-time temperature monitoring inside lithium-ion battery based on online impedance in this embodiment is as follows: Figure 1 As shown, it includes a host computer 1, an impedance test device 2, a single-chip computer 3, a charge and discharge test device 4, a constant temperature box 5, a thermocouple 6, and a lithium-ion battery 7. The host computer 1 is connected to the single-chip computer 3 to control it and transmit temperature data in real time; the host computer 1 is connected to the charge and discharge test device 4 to control it and transmit charge and discharge information in real time; the impedance test device 2 is connected to the single-chip computer 3 to transmit impedance data in real time; the impedance test device 2 is connected to the lithium-ion battery 7 to provide an AC excitation signal to the battery and obtain the battery impedance data in real time; the charge and discharge test device 4 is connected to the lithium-ion battery 7 to charge and discharge the battery; the thermocouple 6 is attached to the surface of the lithium-ion battery 7 to monitor the battery surface temperature in real time, and the thermocouple 6 and the lithium-ion battery 7 are placed in the constant temperature box 5.

[0043] The impedance testing device 2 is an electrochemical workstation, produced by Jiangsu Donghua Company.

[0044] In order to obtain the online estimation mathematical model of the internal temperature of different types and models of batteries, and input the model into the single chip microcomputer, so as to establish the database of the online estimation model of the internal temperature of the battery, the following processes 1 to 3 are required:

[0045] 1. When the battery is in a steady state, use an impedance test device to perform electrochemical impedance spectroscopy tests on the battery at different excitation frequencies to obtain impedance spectrum data of the battery at different temperatures and different SOCs. The imaginary part of impedance can sensitively reflect the dynamic response characteristics inside the battery and is greatly affected by temperature. Then, the relationship between the imaginary part of impedance and temperature is analyzed to determine the characteristic frequency that is most affected by temperature and least affected by SOC;

[0046] 2. After determining the characteristic frequency, extract the imaginary part of the impedance and the corresponding temperature at different temperatures and different SOCs, and establish a mathematical model for online estimation of the internal temperature of the battery similar to the Arrhenius formula:

[0047] T=A*exp(-B*-Z″)+C

[0048] In the formula, T is the internal temperature of the battery, -Z″ is the imaginary part of the impedance, and A, B, and C are fitting coefficients. The model and the type and model of the battery are uploaded to the microcontroller;

[0049] 3. Repeat processes 1 to 2, upload the types and models of multiple batteries and the determined online estimation mathematical model of the battery internal temperature to the microcontroller, thereby establishing a database;

[0050] 4. Use the impedance testing device to perform electrochemical impedance spectroscopy test on the battery online, and transmit the acquired impedance imaginary part data to the single-chip microcomputer. At the same time, input the type and model of the battery into the single-chip microcomputer. The single-chip microcomputer can automatically identify the internal temperature online estimation mathematical model corresponding to the battery according to the type and model of the battery, thereby converting the imaginary part of the impedance into the internal temperature of the battery and outputting it in real time.

[0051] like Figure 2 As shown, a method for monitoring the real-time temperature inside a lithium-ion battery based on online impedance provided by this embodiment includes the following steps:

[0052] Steps 1 to 3 are to determine the online estimation mathematical model of the internal temperature of the battery.

[0053] Step 1, the lithium-ion battery selected in this embodiment is a NCM811 cylindrical 18650 battery with a rated capacity of 2.9Ah. Take a fresh battery and perform 5 standard charge and discharge cycles at room temperature (25°C), that is, 1C constant current discharge to the battery lower cut-off voltage of 2.75V; then 0.5C constant current charge to the battery upper cut-off voltage of 4.2V, and then switch to constant voltage charging until the current drops to 0.05C; repeat 5 times, so as to determine that the actual discharge capacity of the battery at room temperature is 2.7Ah.

[0054] Under steady-state conditions, an impedance test device is used to perform electrochemical impedance spectroscopy tests on the battery at different temperatures and different SOCs. First, a fully charged battery is discharged at a constant current at room temperature, and the battery SOC is controlled to 80%. A thermocouple is attached to the battery surface to monitor the battery surface temperature in real time. The temperature of the thermostat is controlled to -10°C, and the battery is placed in the thermostat for 3 hours to allow the battery to reach thermal equilibrium and ensure that the overall temperature of the battery is consistent. At this time, the temperature monitored by the thermocouple is the internal temperature of the lithium-ion battery. After the internal and external temperatures of the battery reach equilibrium, the battery is tested for electrochemical impedance spectroscopy. The excitation current is 100mA, and the excitation frequency range is: 10000~0.01Hz, covering all electrochemical processes of lithium-ion batteries, avoiding the influence of inductive reactance due to excessively high frequency, and the increased time cost due to excessively low frequency. After the test is completed, the battery SOC is controlled to 80%, and the temperature of the thermostat is adjusted to 0℃, 10℃, 20℃, 30℃, 40℃, and 50℃ respectively. The battery is also left at the corresponding temperature for 3 hours to allow the battery to reach thermal equilibrium, and electrochemical impedance spectroscopy tests are performed to obtain electrochemical impedance spectroscopy data at different temperatures under 80% SOC. After the 80% SOC and different temperature tests are completed, the temperature of the thermostat is adjusted to 25℃. After the battery reaches thermal equilibrium, the battery is discharged at a constant current to make the battery SOC 70%. The temperature of the thermostat is adjusted to -10℃. After the battery reaches thermal equilibrium, the battery is tested for electrochemical impedance spectroscopy. Repeat the above steps until all electrochemical impedance spectroscopy tests at 70% SOC and different temperatures are completed. Control the battery SOC to 60%, 50%, 40%, 30%, and 20%, and repeat the above process at the corresponding SOC and different temperatures until all SOCs and all temperatures are tested.

[0055] Step 2, determine the frequency range that is sensitive to temperature changes but relatively insensitive to SOC changes. Therefore, three temperatures (-10°C, 20°C, 50°C), corresponding to the imaginary part of the impedance at different SOCs, and three SOCs (20%, 50%, 80%), corresponding to the imaginary part of the impedance at different temperatures are selected for analysis. Figure 3 , 4 , 5 are the imaginary part of impedance at different SOCs at -10℃, 20℃ and 50℃ respectively. When the frequency is higher than 100Hz, the imaginary part of impedance is almost unaffected by SOC at the three temperatures. Figure 6 , 7 , 8 are the imaginary impedance parts at different temperatures when 20% SOC, 50% SOC, and 80% SOC, respectively. The frequency range is within the range of 10 to 1000 Hz. Under the three SOCs, the relationship between temperature and the imaginary impedance part is obvious, that is, as the temperature increases, the imaginary impedance part gradually decreases. Therefore, when the frequency range is 100 to 1000 Hz, the imaginary impedance part is sensitive to temperature changes, but relatively insensitive to SOC changes.

[0056] Step 3: After determining the frequency range, the optimal characteristic frequency point needs to be determined. For the 11 frequency points in the frequency range of 100-1000 Hz, the imaginary part of the impedance and the corresponding temperature at different temperatures and different SOCs are extracted respectively, and a mathematical model for online estimation of the internal temperature of the battery similar to the Arrhenius formula is established:

[0057] The Arrhenius equation is an empirical formula for the relationship between the chemical reaction rate constant and temperature, which was created by Arrhenius of Sweden.

[0058] T=A*exp(-B*-Z″)+C

[0059] Where T is the internal temperature of the battery, -Z″ is the imaginary part of the impedance, and A, B, and C are fitting coefficients.

[0060] Analyze the correlation coefficient R at different frequencies 2 ,like Fig. 9 As shown, when the frequency is 398Hz, the correlation coefficient R 2 The maximum value is 0.9936, so the optimal characteristic frequency point is 398Hz, such as Fig.10 As shown, the optimal frequency is 398Hz, and the mathematical model for online estimation of the internal temperature of the lithium-ion battery is:

[0061] T=84.718*exp(-0.138*-Z″)-30.737

[0062] Among them, A is 84.718, B is 0.138, and C is -30.737.

[0063] Step 4: Upload the battery type and model and the internal temperature online estimation mathematical model obtained to the single chip microcomputer. For other types and models of batteries, the above steps 1 to 3 can be used to obtain the corresponding internal temperature online estimation mathematical model, and upload it to the single chip microcomputer to establish a battery internal temperature online estimation mathematical model database.

[0064] The software, database or protocol involved in the present invention are all well-known technologies.

[0065] Step 5. In actual applications, an impedance testing device is used to perform an electrochemical impedance spectroscopy test on the battery online, and the acquired impedance imaginary part data is transmitted to the single-chip microcomputer. At the same time, the type and model of the battery are input into the single-chip microcomputer. The single-chip microcomputer can automatically identify the internal temperature online estimation mathematical model corresponding to the battery according to the type and model of the battery, thereby converting the imaginary part of the impedance into the internal temperature of the battery and outputting it in real time.

[0066] Matters not covered by the present invention are known technologies.

Claims

1. A method for monitoring the real-time temperature inside a lithium-ion battery based on online impedance, characterized in that: The method comprises the following steps: Step 1: Input the type and model information of the battery into the microcontroller of the monitoring device; Step 2: The working electrode and the sensitive electrode of the impedance test device are connected to the positive electrode of the battery, and the reference electrode and the auxiliary electrode are connected to the negative electrode of the battery. The electrochemical impedance spectroscopy test of the battery is performed online, and the impedance data is obtained; Step 3: The impedance testing device transmits the acquired impedance data to the single chip microcomputer in real time; Step 4: The single chip microcomputer converts the impedance data into the internal temperature of the battery and outputs it in real time based on the type and model information of the battery and the measured impedance data using the internal temperature online estimation mathematical model corresponding to the battery in the database; The monitoring device comprises a data processing module and an impedance testing device; The method for establishing a mathematical model database for online estimation of the internal temperature of a lithium-ion battery comprises the following steps: Step 1, select the type and model of lithium-ion battery and determine the actual capacity of the battery: according to the standard charge and discharge requirements in the battery specification, take a fresh battery at room temperature (25°C) and perform 3 to 5 standard charge and discharge cycles to determine the actual discharge capacity of the battery at room temperature; Under steady-state conditions, an impedance test device is used to perform electrochemical impedance spectroscopy tests on the battery at different temperatures and different SOCs. First, a fully charged battery is discharged at a constant current at room temperature, and the battery SOC is controlled to 80%. A thermocouple is attached to the battery surface to monitor the battery surface temperature in real time, and the temperature of the thermostat is controlled to -10°C. The battery is placed in the thermostat for 3 to 4 hours. At this time, the temperature monitored by the thermocouple is the internal temperature of the lithium-ion battery. After the internal and external temperatures of the battery reach equilibrium, the battery is subjected to an electrochemical impedance spectroscopy test, with an excitation current of 100mA and an excitation frequency range of 10000 to 0.01Hz. After the test, the battery SOC is controlled to 80%, and the temperature of the thermostat is adjusted to 0°C, 10°C, 20°C, 30°C, 40°C, and 50°C, respectively. The battery is also The battery is allowed to stand at the corresponding temperature for a sufficient time to reach thermal equilibrium, and electrochemical impedance spectroscopy tests are performed to obtain electrochemical impedance spectroscopy data at different temperatures under 80% SOC; after the 80% SOC and different temperature tests are completed, the temperature of the thermostat is adjusted to 25°C, and after the battery reaches thermal equilibrium, the battery is discharged at a constant current to make the battery SOC 70%, and the temperature of the thermostat is adjusted to -10°C. After the battery reaches thermal equilibrium, the battery is subjected to an electrochemical impedance spectroscopy test, and the above steps are repeated until all electrochemical impedance spectroscopy tests at 70% SOC and different temperatures are completed; the battery SOC is controlled to be 60%, 50%, 40%, 30%, and 20%, and the above process is repeated at the corresponding SOC and different temperatures until all SOCs and all temperatures are tested; Step 2, determine the frequency range that is sensitive to temperature changes but relatively insensitive to SOC changes; Select three temperatures -10℃, 20℃, 50℃, corresponding to the imaginary part of impedance at different SOCs, and three SOCs: 20%, 50%, 80%, and compare the imaginary part of impedance at different temperatures to determine the frequency range in which the imaginary part of impedance is sensitive to temperature changes but relatively insensitive to SOC changes; Step 3, after determining the frequency range, it is necessary to determine the optimal characteristic frequency point. In the selected frequency range, 8 to 12 frequency points are taken between each decade in logarithmic form to extract the imaginary part of the impedance and the corresponding temperature at different temperatures and different SOCs, respectively, according to the formula: T=A*exp(-B*-Z″)+C Where T is the internal temperature of the battery, -Z″ is the imaginary part of the impedance, and A, B, and C are fitting coefficients; Obtain the fitting coefficients A, B, and C of the mathematical model for online estimation of the internal temperature of lithium-ion batteries of this type and model; Step 4, uploading the fitting coefficients A, B, and C of the online estimation mathematical model of the internal temperature of the lithium-ion battery of the type and model to the single chip microcomputer; Step 5, select other types and models of lithium-ion batteries, repeat steps 1 to 4 for each model of battery, and obtain the fitting coefficients A, B, and C of the corresponding mathematical model for online estimation of the internal temperature of the lithium-ion battery; finally, establish a database of the mathematical model for online estimation of the internal temperature of the lithium-ion battery.

2. The method for monitoring the internal real-time temperature of a lithium-ion battery based on online impedance as claimed in claim 1, characterized in that: The data processing module is a single chip microcomputer, which is provided with information on the type and model of the battery, as well as fitting coefficients A, B, and C of a corresponding mathematical model for online estimation of the internal temperature of the lithium-ion battery.

3. The method for monitoring the internal real-time temperature of a lithium-ion battery based on online impedance as claimed in claim 1, characterized in that: The temperature range of the monitored battery is -10 to 50°C.

4. The method for monitoring the internal real-time temperature of a lithium-ion battery based on online impedance as claimed in claim 1, wherein the type and model of the lithium-ion battery is NCM111 cylinder 18650, NCM523 cylinder 18650, NCM811 cylinder 18650, LFP cylinder 18650, NCM111 soft pack, NCM523 soft pack, NCM811 soft pack or LFP soft pack.

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