Heating method and system for power battery of vehicle, vehicle and equipment
By using pulsed current with specific frequency and amplitude to self-heat the power battery, the problems of declining charging performance and safety of lithium batteries in low-temperature environments are solved, achieving rapid heating and reduced damage.
Patent Information
- Application Number
- CN202511406980.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-29
- Publication Date
- 2025-12-19
AI Technical Summary
In low-temperature environments, the charging performance of lithium batteries declines, the activation resistance of the battery increases, leading to lithium deposition and separator puncture, which affects the battery's durability and safety. Existing heating methods are difficult to meet the requirements of fast charging.
The power battery is self-heated by using pulse currents with specific frequencies and varying charging and discharging current amplitudes. This utilizes the Joule heating effect to rapidly raise the temperature and prevent lithium deposition and separator puncture. The process includes obtaining the power battery temperature, determining the characteristic frequency and current amplitude of the alternating pulse current, and using the alternating pulse current for self-heating.
It enables rapid heating of the power battery, increases the heating rate, reduces the risk of lithium deposition, avoids separator puncture, and reduces battery damage.
Smart Images
Figure CN121157732A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of vehicles, in particular to a heating method and system for a power battery of a vehicle, a vehicle and equipment. BACKGROUND
[0002] As the ambient temperature decreases, the lithium ion mobility and diffusion rate in the lithium cell are affected, leading to a decrease in charge transfer reaction activity, a decline in battery charging performance, and a performance decay and safety hazard. At low temperatures, the battery activation impedance increases, and the negative electrode surface potential decreases, exacerbating lithium precipitation, forming moss or dendritic deposition, which not only loses active lithium ions, but also may pierce the separator, causing internal short circuit, seriously affecting the durability and safety of the battery. Therefore, effective thermal management of the battery system in a low temperature environment has become a problem to be solved.
[0003] Currently, the low-temperature preheating technology of the battery mainly relies on heating resistance wires or cooling media to heat the battery through heat conduction or convection, but is limited by cost and volume, and the heating power is usually low, the temperature rising speed is slow, and it is difficult to meet the demand for fast charging. The new energy vehicle field is exploring internal heating strategies, which induce Ohmic effect by injecting high-frequency alternating pulse current to rapidly heat up. The self-heating efficiency of lithium ion battery depends on the internal resistance value, specific heat capacity, and pulse current amplitude and frequency. Reducing the frequency and increasing the amplitude can accelerate the heating, but increase the risk of overcharging and overdischarging, which may cause problems such as lithium precipitation and solid electrolyte interface film decomposition. SUMMARY
[0004] Therefore, it is necessary to provide a heating method and system for a power battery of a vehicle, a vehicle and equipment to solve the above technical problems, which can rapidly heat the power battery, maximize the generation of Joule heat, improve the temperature rising rate, and effectively reduce or even avoid lithium precipitation and piercing the separator, thereby reducing the damage to the power battery.
[0005] In a first aspect, a heating method for a power battery of a vehicle is provided, comprising: obtaining a temperature of the power battery; obtaining a characteristic frequency of an alternating pulse current, a minimum current at which lithium precipitation occurs in the power battery, and a minimum current at which solid electrolyte interface film decomposition occurs according to the temperature of the power battery, wherein different temperatures of the power battery correspond to different characteristic frequencies of the alternating pulse current, different minimum currents at which lithium precipitation occurs in the power battery, and different minimum currents at which solid electrolyte interface film decomposition occurs; obtaining a charging and discharging current amplitude of the alternating pulse current according to the minimum current at which lithium precipitation occurs in the power battery and the minimum current at which solid electrolyte interface film decomposition occurs; using the alternating pulse current to self-heat the power battery.
[0006] In some examples, the characteristic frequency of the alternating pulse current, the minimum current at which lithium precipitation occurs in the power battery, and the minimum current at which the solid electrolyte interface film decomposes are obtained according to the temperature of the power battery, comprising: determining a temperature interval in which the temperature of the power battery is located; obtaining the characteristic frequency of the alternating pulse current corresponding to the temperature interval from a pre-stored characteristic frequency table, wherein the characteristic frequency table includes a plurality of characteristic frequencies corresponding to a plurality of different temperature intervals one by one; obtaining the minimum current at which lithium precipitation occurs in the power battery corresponding to the temperature interval from a pre-stored minimum current table at which lithium precipitation occurs, wherein the minimum current table at which lithium precipitation occurs includes a plurality of minimum currents at which lithium precipitation occurs corresponding to a plurality of different temperature intervals one by one; obtaining the minimum current at which the solid electrolyte interface film decomposes corresponding to the temperature interval from a pre-stored minimum current table at which the solid electrolyte interface film decomposes, wherein the minimum current table at which the solid electrolyte interface film decomposes includes a plurality of minimum currents at which the solid electrolyte interface film decomposes corresponding to a plurality of different temperature intervals one by one.
[0007] In some examples, the characteristic frequency corresponding to any temperature interval in the characteristic frequency table is obtained in the following manner: for any temperature interval, selecting a target temperature from the temperature interval; placing a plurality of power batteries of the same specification at different states of charge at the target temperature respectively; when the plurality of power batteries reaches the target temperature, performing electrochemical impedance spectroscopy test on each of the power batteries respectively to obtain a corresponding Bode plot; selecting a frequency value at which the reactance is equal to zero from each of the Bode plots respectively; obtaining an average value of a plurality of the frequency values, and taking the average value as the characteristic frequency of the alternating pulse current corresponding to the temperature interval.
[0008] In some examples, the minimum current at which lithium precipitation occurs in the power battery corresponding to any temperature interval in the minimum current table at which lithium precipitation occurs is obtained in the following manner: performing constant current charging on the power battery at the target temperature and a set charge rate to a preset state of charge to obtain an open circuit voltage change of the power battery within a set time, and obtaining a voltage-time curve according to the open circuit voltage change of the power battery within the set time; differentially processing the voltage-time curve, and determining the minimum current at which lithium precipitation occurs in the power battery corresponding to the temperature interval at the charge rate according to an inflection point in the voltage-time curve.
[0009] In some examples, the method for obtaining the minimum current table of solid electrolyte interface film decomposition corresponding to any temperature interval in the minimum current table of solid electrolyte interface film decomposition includes: performing constant current discharge on the power battery at the target temperature and a set discharge rate to a preset state of charge to obtain an open circuit voltage change of the power battery within a set time, and obtaining a voltage-time curve according to the open circuit voltage change of the power battery within the set time; performing differential processing on the voltage-time curve, and determining the minimum current of solid electrolyte interface film decomposition corresponding to the temperature interval at the discharge rate according to an inflection point in the voltage-time curve.
[0010] In some examples, the self-heating of the power battery by using the alternating pulse current includes: determining a sum of the charging time and the discharging time according to the characteristic frequency of the alternating pulse current; determining a relationship model of the charging current amplitude, the charging time, the discharging current amplitude and the discharging time of the alternating pulse current under the condition that the charging amount and the discharging amount are equal; solving the charging time and the discharging time according to the relationship model and the sum of the charging time and the discharging time; self-heating the power battery by using the alternating pulse current based on the charging time and the discharging time.
[0011] In some examples, during the self-heating of the power battery by using the alternating pulse current, the method further includes: determining whether the temperature of the power battery reaches a set temperature; if yes, obtaining a temperature rising rate of the power battery according to the time consumption of the self-heating process and the temperature rise of the power battery.
[0012] In a second aspect, a heating system of a power battery of a vehicle is provided, including: an acquisition module configured to obtain a power battery temperature; a current frequency determination module configured to obtain a characteristic frequency of an alternating pulse current, a minimum current at which lithium precipitation exists in the power battery and a minimum current of solid electrolyte interface film decomposition according to the power battery temperature, wherein different power battery temperatures correspond to different characteristic frequencies of the alternating pulse current, different minimum currents at which lithium precipitation exists in the power battery and different minimum currents of solid electrolyte interface film decomposition; a current amplitude determination module configured to obtain charging and discharging current amplitudes of the alternating pulse current according to the minimum current at which lithium precipitation exists in the power battery and the minimum current of solid electrolyte interface film decomposition. a control module configured to self-heat the power battery by using the alternating pulse current.
[0013] In a third aspect, a vehicle is provided, comprising the heating system of the power battery of the vehicle according to the second aspect above.
[0014] In a fourth aspect, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and capable of running on the processor, wherein the processor implements the heating method of the power battery according to the first aspect above when executing the program.
[0015] By using the pulse with the specific frequency and the charging and discharging current amplitude, the power battery can be quickly heated, the Joule heat can be maximized, the temperature rising rate can be improved, and the lithium precipitation can be effectively reduced or even avoided and the puncture of the diaphragm can be avoided or even eliminated, thereby reducing the damage of the power battery. BRIEF DESCRIPTION OF DRAWINGS
[0016] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, read in conjunction with the accompanying drawings: Figure 1 A flow chart of the heating method of the power battery of the vehicle provided by the embodiments of the application is shown; Figure 2 A curve diagram is shown for the amplitude and time of the pulse charging and discharging; Figure 3 A temperature rising rate curve diagram of the power battery is shown; Figure 4 A structure block diagram of the heating system of the power battery of the vehicle provided by the embodiments of the application is shown; Figure 5 A structure block diagram of the computer device provided by the embodiments of the application is shown. DETAILED DESCRIPTION
[0017] The application will be further described in conjunction with the embodiments and the accompanying drawings. It can be understood that the specific embodiments described herein are only used to explain the related application, but not to limit the application. In addition, it should be noted that, for the convenience of description, only the parts related to the application are shown in the drawings.
[0018] It should be noted that the features of the embodiments in the application, i.e., the features of the embodiments, can be combined with each other without conflict. The application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.
[0019] The heating method, system, vehicle, and device of the power battery of the vehicle according to the embodiments of the application are described in detail below in conjunction with the accompanying drawings.
[0020] The implementation environment of the embodiment of the present application can obtain the temperature of the power battery by a computing device such as a computer; obtain the characteristic frequency of the alternating pulse current, the minimum current at which the power battery exists lithium precipitation, and the minimum current at which the solid electrolyte interface film decomposes according to the temperature of the power battery, wherein different power battery temperatures correspond to different characteristic frequencies of the alternating pulse current, different minimum currents at which the power battery exists lithium precipitation, and different minimum currents at which the solid electrolyte interface film decomposes; obtain the charge-discharge current amplitude of the alternating pulse current according to the minimum current at which the power battery exists lithium precipitation and the minimum current at which the solid electrolyte interface film decomposes; and perform self-heating on the power battery by using the alternating pulse current.
[0021] The computing device can be a controller configured on the vehicle.
[0022] Figure 1 FIG. 1 is a flowchart of a heating method of a power battery of a vehicle according to an embodiment of the present application. As shown in FIG. 1, the heating method of the power battery of the vehicle according to an embodiment of the present application comprises the following steps: Figure 1 S101: obtaining the temperature of the power battery.
[0023] In the embodiment of the present application, the temperature of the power battery generally refers to the current temperature of the power battery.
[0024] S102: obtaining the characteristic frequency of the alternating pulse current, the minimum current at which the power battery exists lithium precipitation, and the minimum current at which the solid electrolyte interface film decomposes according to the temperature of the power battery, wherein different power battery temperatures correspond to different characteristic frequencies of the alternating pulse current, different minimum currents at which the power battery exists lithium precipitation, and different minimum currents at which the solid electrolyte interface film decomposes.
[0025] In an embodiment of the present application, obtaining the characteristic frequency of the alternating pulse current, the minimum current at which the power battery exists lithium precipitation, and the minimum current at which the solid electrolyte interface film decomposes according to the temperature of the power battery comprises: determining the temperature interval in which the temperature of the power battery is located; obtaining the characteristic frequency of the alternating pulse current corresponding to the temperature interval from a pre-stored characteristic frequency table, wherein the characteristic frequency table comprises a plurality of characteristic frequencies corresponding to a plurality of different temperature intervals one by one; obtaining the minimum current at which the power battery exists lithium precipitation corresponding to the temperature interval from a pre-stored minimum current table at which lithium precipitation exists, wherein the minimum current table at which lithium precipitation exists comprises a plurality of minimum currents at which lithium precipitation exists corresponding to a plurality of different temperature intervals one by one; and obtaining the minimum current at which the solid electrolyte interface film decomposes corresponding to the temperature interval from a pre-stored minimum current table at which the solid electrolyte interface film decomposes, wherein the minimum current table at which the solid electrolyte interface film decomposes comprises a plurality of minimum currents at which the solid electrolyte interface film decomposes corresponding to a plurality of different temperature intervals one by one.
[0026] In the above examples, the method for obtaining the characteristic frequency corresponding to any temperature interval in the characteristic frequency table comprises: for any temperature interval, selecting a target temperature from the temperature interval; placing a plurality of power batteries of the same specification at different states of charge at the target temperature; when the plurality of power batteries reach the target temperature, performing electrochemical impedance spectroscopy on each of the power batteries to obtain a corresponding Bode plot; selecting a frequency value corresponding to a zero reactance from each of the Bode plots; obtaining an average value of the plurality of frequency values, and taking the average value as the characteristic frequency of the alternating pulse current corresponding to the temperature interval.
[0027] The method for obtaining the minimum current at which lithium precipitation occurs in the power battery corresponding to any temperature interval in the minimum current table at which lithium precipitation occurs comprises: performing constant-current charging on the power battery at the target temperature and a set charging rate to a preset state of charge, obtaining an open-circuit voltage change of the power battery within a set time, and obtaining a voltage-time curve according to the open-circuit voltage change of the power battery within the set time. Differentiate the voltage-time curve, and determine the minimum current at which lithium precipitation occurs in the power battery corresponding to the temperature interval at the charging rate according to the inflection point in the voltage-time curve.
[0028] The method for obtaining the minimum current at which the solid electrolyte interface film decomposes corresponding to any temperature interval in the minimum current table at which the solid electrolyte interface film decomposes comprises: performing constant-current discharging on the power battery at the target temperature and a set discharging rate to a preset state of charge, obtaining an open-circuit voltage change of the power battery within a set time, and obtaining a voltage-time curve according to the open-circuit voltage change of the power battery within the set time; differentiating the voltage-time curve, and determining the minimum current at which the solid electrolyte interface film decomposes corresponding to the temperature interval at the discharging rate according to the inflection point in the voltage-time curve.
[0029] wherein one temperature interval is also referred to as one single pulse heating interval, and the characteristic frequency of the alternating pulse current corresponding to one single pulse heating interval, such as pulse heating interval n, is denoted as f n , the minimum current at which lithium precipitation occurs is denoted as I cn , and the minimum current at which the solid electrolyte interface film decomposes is denoted as I dn .
[0030] The characteristic frequency of lithium battery at different temperature is different. If the characteristic frequency of each temperature is measured, it will be very cumbersome. Therefore, the characteristic frequency of pulse self-heating should remain the same in a certain temperature range. If the temperature range is too large, the error will be larger. If the temperature range is too small, the calculation amount will be increased. Selecting the characteristic frequency of the middle temperature in a heated range will reduce the error.
[0031] Assuming that the initial temperature of pulse self-heating is T℃, five lithium batteries of the same specification at different states of charge are placed in environments at (T+2n-1)℃ (n=1, 2, 3…) respectively, and are left until the temperature of the lithium battery is equal to the set temperature.
[0032] The lithium battery after the completion of the standing is tested by electrochemical impedance spectroscopy to obtain the corresponding Bode plot, and a frequency value f n1 , f n2 , …, f n5 is selected when the reactance is equal to zero. The average value of the characteristic frequency value f n is obtained. At this characteristic frequency, most of the Joule heat can be effectively utilized, that is, the heat effect generated by Ohmic resistance. In addition, there is no response of activated impedance at this frequency, and no reaction heat should be generated. The characteristic frequency at a specific temperature basically does not change with the state of charge SOC, so the characteristic frequency is the safety frequency.
[0033] The minimum current I cn of lithium precipitation of the lithium battery at a specific temperature is obtained by using the method of non-destructive voltage relaxation: The lithium battery is charged at a constant current from small to large at a set temperature (T+2n-1)℃ and a set charge rate (1C, 2C, …) to a set SOC, and then stopped. The open circuit voltage change of the lithium battery within a set time is recorded to obtain a voltage-time curve.
[0034] The voltage-time curve is differentiated. If there is an inflection point in the time curve, it is determined that there is lithium precipitation when the lithium battery is charged to the set SOC at the set temperature and the set charge rate. The charging current at this charge rate is recorded as I cn .
[0035] The minimum current I dn of the decomposition of the solid electrolyte interface film (SEI) of the lithium battery at a specific temperature is obtained by using the method of non-destructive voltage relaxation: The lithium battery is discharged at a constant current from small to large at a set temperature (T+2n-1)℃ and a set discharge rate (1C, 2C, …) to a set SOC, and then stopped. The open circuit voltage change of the lithium battery within a set time is recorded to obtain a voltage-time curve.
[0036] Differential the voltage-time curve, if there is an inflection point in the time curve, it is determined that the lithium cell has SEI film decomposition when discharged to the set SOC at the set temperature and the set discharge rate, and the discharge current at this discharge rate is recorded as I dn .
[0037] Among them, the voltage relaxation method is a non-destructive testing technology, which can be detected without damaging the battery structure, which has high importance for the long-term use and safety evaluation of the battery.
[0038] S103: Obtain the charge-discharge current amplitude of the alternating pulse current according to the minimum current of lithium precipitation and the minimum current of solid electrolyte interface film decomposition of the power battery.
[0039] S104: Self-heat the power battery by using the alternating pulse current.
[0040] In an embodiment of the present application, self-heating the power battery by using the alternating pulse current comprises: determining the sum of the charging time and the discharging time according to the characteristic frequency of the alternating pulse current; determining the relationship model of the charging current amplitude of the alternating pulse current, the charging time, the discharging current amplitude of the alternating pulse current and the discharging time while keeping the charging amount and the discharging amount equal; solving the charging time and the discharging time according to the relationship model and the sum of the charging time and the discharging time; and self-heating the power battery by using the alternating pulse current based on the charging time and the discharging time.
[0041] In an embodiment of the present application, during the process of self-heating the power battery by using the alternating pulse current, it further comprises: judging whether the temperature of the power battery reaches the set temperature; if yes, obtaining the temperature rising rate of the power battery according to the time consumption of the self-heating process and the temperature rise of the power battery.
[0042] As a specific example, in order to alleviate the capacity attenuation of the battery cell caused by pulse self-heating, the SOC of the lithium battery cell should be kept unchanged during pulse self-heating, and the specific requirements are as follows: In a single pulse self-heating temperature interval, the pulse curve of self-heating is as shown in Figure 2 The charging time and the discharging time satisfy the following conditions, I cn t cn =I dn t dn , t cn +t dn =1 / f n .
[0043] The total time of pulse self-heating and the temperature rising rate are obtained according to the following steps: The temperature T of the lithium battery cell is continuously monitored l , and the next set of characteristic frequencies f is replaced every 2℃ of temperature rise n , the charging current amplitude I cn , and the discharging current amplitude I dn .
[0044] wherein the temperatures of the positive electrode side, the negative electrode side, the center of the large face, and the center of the bottom side of the large face of the lithium battery cell are respectively measured, and the average value is calculated as the temperature T of the lithium battery cell l .
[0045] The temperature is raised to the normal charging temperature range of the lithium battery cell, and the pulse heating is stopped, wherein the total temperature rising time is t, the difference between the initial temperature and the target heating temperature is T a ; the temperature rising rate Q is calculated, Q = T a / t, with the unit of ℃ / min.
[0046] Example 1: A lithium battery cell with a rated capacity of 24 Ah is used for testing. In this embodiment, the method for determining the pulse self-heating conditions of the lithium battery cell comprises the following steps: first, the pulse self-heating initial temperature is -20℃, and five 24 Ah lithium battery cells of the same specification with different SOCs of 5%, 10%, 20%, 50%, and 70% are selected, and are placed in an environment at -19℃ until the temperature of the lithium battery cell reaches the set temperature.
[0047] Second, the lithium battery cell reaching the set temperature is tested by electrochemical impedance spectroscopy to obtain the corresponding Bode plot, and a frequency value f 11 , f 12 , …, f 15 is selected when the reactance is equal to zero, and the average value is taken to obtain the characteristic frequency value f1. Through testing and calculation, the characteristic frequency at -19℃ is 310 Hz.
[0048] Third, the lithium battery cell is charged at a constant current from small to large at the set temperature -19℃ and the set charge rate (1C, 2C, …) to the set SOC = 80%, and then stopped, and the open circuit voltage change of the lithium battery cell within the set time is recorded to obtain the voltage-time curve.
[0049] Fourth, the voltage-time curve is differentiated, and if there is an inflection point in the time curve, it is determined that lithium precipitation exists when the lithium battery cell is charged to the set SOC at the set temperature and the set charge rate. The charging current at this charge rate is recorded as I c1 , and the amplitude of the charging current is 8C through testing and calculation.
[0050] Step 5, constant current discharge the lithium battery at a set temperature of -19℃ and a set discharge rate (1C, 2C, …) to the cut-off voltage of the lithium battery, record the open circuit voltage change of the lithium battery within a set time, and obtain the voltage-time curve; Step 6, differentiate the voltage-time curve, if there is an inflection point in the time curve, it is determined that lithium precipitation exists when the lithium battery is discharged to the set SOC at the set temperature and the set discharge rate, and the discharge current at this discharge rate is recorded as I d1 , and the amplitude of the charging current is 10C after testing and calculation.
[0051] Step 7, at intervals of 2℃, sequentially at -17℃, -15℃, …, 1℃, obtain the characteristic frequencies f2, f3, …, f 11 , the minimum current I c2 , I c3 , …, I c11 , and the minimum current I d2 , I d3 , …, I d11 .
[0052] Step 8, within the single pulse self-heating temperature range, the charging time and the discharging time meet the following conditions, I cn t cn =I dn t dn , t cn +t dn =1 / f n .
[0053] Step 9, cycle step 8, continuously monitor the temperature of the lithium battery until the next target temperature is reached, obtain the pulse charging and discharging heating time t n , and enter the next stage of pulse heating at the characteristic frequency.
[0054] Respectively measure the temperature of the positive electrode side, the negative electrode side, the center of the large face, and the center of the bottom side of the large face of the lithium battery, and calculate the average value as the temperature T l of the lithium battery.
[0055] Step 10, pulse self-heating to the normal charging temperature range of the lithium battery, stop pulse heating, calculate the total pulse heating time t = t1 + t2 + … + t 11 , the total pulse heating time t is 10.50 min; the difference between the initial temperature and the target heating temperature is T a , the temperature rise rate Q = T a / t, and the temperature rise rate of example 1 is 1.99 ℃ / min.
[0056] Example 2: The lithium battery cell with a rated capacity of 24 Ah is used for testing, and the pulse self-heating condition determination method of the lithium battery cell in the embodiment comprises: In the first step, the pulse self-heating starting temperature is-15℃, and five 24 Ah lithium battery cells with the same specification and different SOCs are selected, and the SOCs are 5%, 10%, 20%, 50% and 70% respectively, and the lithium battery cells are placed in an environment at-14℃ and kept still until the temperature of the lithium battery cell is equal to the set temperature.
[0057] In the second step, the lithium battery cell reaching the set temperature is tested by electrochemical impedance spectroscopy to obtain a corresponding Bode plot, and a frequency value f 21 , f 22 , …, f 25 is selected when the reactance is equal to zero, and the average value is obtained to obtain the characteristic frequency value f1, and the characteristic frequency is 255 Hz at-14℃ through testing and calculation.
[0058] In the third step, the lithium battery cell is charged at the set temperature-14℃ and the set charge rate (1C, 2C, …) from small to large to the set SOC=80% and then stopped, and the open circuit voltage change of the lithium battery cell within the set time is recorded to obtain a voltage-time curve.
[0059] In the fourth step, the voltage-time curve is differentiated, and if there is an inflection point in the time curve, it is determined that lithium precipitation exists when the lithium battery cell is charged to the set SOC at the set temperature and the set charge rate, and the charging current at this charge rate is recorded as I c1 , and the amplitude of the charging current is 9C through testing and calculation; In the fifth step, the lithium battery cell is discharged at the set temperature-14℃ and the set discharge rate (1C, 2C, …) from small to large to the cut-off voltage of the lithium battery cell, and the open circuit voltage change of the lithium battery cell within the set time is recorded to obtain a voltage-time curve; In the sixth step, the voltage-time curve is differentiated, and if there is an inflection point in the time curve, it is determined that lithium precipitation exists when the lithium battery cell is discharged to the set SOC at the set temperature and the set discharge rate, and the discharge current at this charge rate is recorded as I d1 , and the amplitude of the charging current is 11C through testing and calculation.
[0060] In the seventh step, the interval is 2℃, and the characteristic frequencies f2, f3, …, f 11 are obtained at-12℃, -10℃, …, 0℃ respectively according to the second to sixth steps, the minimum current I c2 , I c3 , …, I c8 , and the minimum current I d2 , I d3 , …, I d8.
[0061] Eighth step, within the single pulse self-heating temperature interval, the charging time and discharging time meet the following conditions, I cn t cn =I dn t dn , t cn +t dn =1 / f n .
[0062] Ninth step, cycle the eighth step, continuously monitor the temperature of the lithium battery cell until the next target temperature is reached, obtain the pulse charging and discharging heating time t n , and enter the next stage of characteristic frequency pulse heating.
[0063] The temperature of the lithium battery cell is measured at the positive electrode side, the negative electrode side, the center of the large face, and the center of the bottom side of the large face, respectively, and the average value is calculated as the temperature T l of the lithium battery cell.
[0064] Tenth step, pulse self-heating to the normal charging temperature interval of the lithium battery cell, stop pulse heating, calculate the total pulse heating time t=t1+t2+…+t8, the total pulse heating time t of example 2 is 6.38 min; the difference between the initial temperature and the target heating temperature is T a , the temperature rise rate Q=T a / t, the temperature rise rate of this example 2 is 2.35 ℃ / min.
[0065] Example 3: A lithium battery cell with a rated capacity of 24 Ah is tested, the lithium battery cell pulse self-heating condition determination method in this example includes: First step, the pulse self-heating starting temperature is -10℃, select five 24 Ah lithium battery cells of the same specification with different SOCs, SOCs are 5%, 10%, 20%, 50% and 70%, place them in a -9℃ environment and stand until the lithium battery cell temperature equals the set temperature.
[0066] Second step, perform electrochemical impedance spectroscopy test on the lithium battery cell that reaches the set temperature to obtain the corresponding Bode plot, select a frequency value f 11 , f 12 , …, f 15 , take the average value to obtain the characteristic frequency value f1, the characteristic frequency at -9℃ is 195 Hz after testing and calculation.
[0067] Third step, constant current charge the lithium battery cell from small to large at the set temperature -9℃ and the set charge rate (1C, 2C, …) to the set SOC=80% and stop, record the open circuit voltage change of the lithium battery cell within the set time to obtain the voltage-time curve.
[0068] Fourth step, the voltage-time curve is differentiated, if there is an inflection point in the time curve, it is determined that lithium precipitation exists when the lithium battery is charged to the set SOC at the set temperature and the set charge rate, and the charging current at this charge rate is recorded as I c1 , the amplitude of the charging current is 12C after testing and calculation.
[0069] Fifth step, the lithium battery is discharged at a constant current from small to large at the set temperature-9℃ and the set discharge rate (1C, 2C, …) to the cut-off voltage of the lithium battery, and the open-circuit voltage change of the lithium battery within the set time is recorded to obtain the voltage-time curve.
[0070] Sixth step, the voltage-time curve is differentiated, if there is an inflection point in the time curve, it is determined that lithium precipitation exists when the lithium battery is discharged to the set SOC at the set temperature and the set discharge rate, and the discharge current at this charge rate is recorded as I d1 , the amplitude of the charging current is 14C after testing and calculation.
[0071] Seventh step, at intervals of 2℃, the characteristic frequencies f2, f3, …, f 11 , the minimum current I c2 , I c3 , …, I c6 and the minimum current I d2 , I d3 , …, I d6 of SEI film decomposition are obtained at-7℃, -5℃, …, 1℃ respectively according to steps two to six.
[0072] Eighth step, within the single pulse self-heating temperature interval, the charging time and the discharging time meet the following conditions, I cn t cn =I dn t dn , t cn +t dn =1 / f n .
[0073] Ninth step, cycle the eighth step, continuously monitor the temperature of the lithium battery until the next target temperature is reached, obtain the pulse charging and discharging heating time t n , and enter the next stage of characteristic frequency pulse heating.
[0074] The temperature of the positive electrode side, the negative electrode side, the center of the large face and the center of the bottom side of the large face of the lithium battery is measured respectively, and the average value is calculated as the temperature T l of the lithium battery.
[0075] The tenth step is to pulse self-heat to the normal charging temperature range of the lithium battery cell, stop the pulse heating, calculate the total pulse heating time t=t1+t2+…+t6, and the total pulse heating time t of Example 3 is 4.43 min; the difference between the starting temperature and the target heating temperature is T a , the temperature rise rate Q=T a / t, and the temperature rise rate of this embodiment 3 is 2.48 ℃ / min.
[0076] As Figure 3 shown, the temperature rise rate of the power battery in Examples 1 to 3 is shown.
[0077] According to the heating method of the power battery of the vehicle, the power battery can be quickly heated by using pulses with specific frequencies and different charge and discharge current amplitudes, the Joule heat can be maximized to improve the temperature rise rate, and in addition, the lithium precipitation can be effectively reduced or even avoided, and the puncture of the separator can be avoided or even eliminated, thereby reducing the damage of the power battery.
[0078] Figure 4 is a structural diagram of a heating system of a power battery of a vehicle according to an embodiment of the present application. As Figure 4 shown, the heating system of the power battery of the vehicle according to an embodiment of the present application comprises an acquisition module 410, a current frequency determination module 420, a current amplitude determination module 430 and a control module 440, wherein: The acquisition module 410 is configured to obtain the temperature of the power battery. The current frequency determination module 420 is configured to obtain the characteristic frequency of the alternating pulse current, the minimum current at which lithium precipitation occurs in the power battery and the minimum current at which the solid electrolyte interface film decomposes according to the temperature of the power battery, wherein different temperatures of the power battery correspond to different characteristic frequencies of the alternating pulse current, different minimum currents at which lithium precipitation occurs in the power battery and different minimum currents at which the solid electrolyte interface film decomposes. The current amplitude determination module 430 is configured to obtain the charge and discharge current amplitude of the alternating pulse current according to the minimum current at which lithium precipitation occurs in the power battery and the minimum current at which the solid electrolyte interface film decomposes. The control module 440 is configured to self-heat the power battery by using the alternating pulse current.
[0079] According to the heating method of the power battery of the vehicle, the power battery can be quickly heated by using pulses with specific frequencies and different charge and discharge current amplitudes, the Joule heat can be maximized to improve the temperature rise rate, and in addition, the lithium precipitation can be effectively reduced or even avoided, and the puncture of the separator can be avoided or even eliminated, thereby reducing the damage of the power battery.
[0080] The specific definition of the heating system of the power battery of the vehicle can refer to the definition of the heating method of the power battery of the vehicle in the above, which will not be repeated here. The above various modules of the heating system of the power battery of the vehicle can be implemented by software, hardware and their combinations. The above various modules can be embedded in or independent of the processor in the computer device in the form of hardware, or stored in the memory of the computer device in the form of software, so that the processor calls and executes the operations corresponding to the above various modules.
[0081] Further, a vehicle is provided, comprising: the heating system of the power battery of the vehicle according to the above embodiments, which can quickly heat the power battery by using pulses with different frequency and charge-discharge current amplitude, can maximize the generation of Joule heat, improve the heating rate, and further can effectively reduce or even avoid lithium precipitation and avoid or eliminate puncture of the separator, thereby reducing the damage of the power battery.
[0082] Reference will be made to the following Figure 5 , Figure 5 A structure schematic diagram of a computer device suitable for implementing the embodiments of the present application is shown.
[0083] As shown in Figure 5 , the computer system 1000 includes a central processing unit (CPU) 1001, which can perform various appropriate actions and processes according to programs stored in a read-only memory (ROM) 1002 or programs loaded from a storage portion 1008 into a random access memory (RAM) 1003. In the RAM 1003, various programs and data required for operation instructions of the system are also stored. The CPU 1001, the ROM 1002 and the RAM 1003 are connected to each other through a bus 1004. An input / output (I / O) interface 1005 is also connected to the bus 1004.
[0084] The following components are connected to the I / O interface 1005: an input portion 1006 including a keyboard, a mouse, etc.; an output portion 1007 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker, etc.; a storage portion 1008 including a hard disk, etc.; and a communication portion 1009 including a network interface card such as a LAN card, a modem, etc. The communication portion 1009 performs communication processing via a network such as the Internet. A drive 1010 is also connected to the I / O interface 1005 as needed. A removable medium 1011 such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc. is mounted on the drive 1010 as needed, so that a computer program read therefrom is installed in the storage portion 1008 as needed.
[0085] In particular, according to the embodiments of the present application, the above reference flowchart Figure 1The described processes can be implemented as computer-readable storage media. For example, an embodiment of the present application includes a computer-readable storage medium comprising a computer program containing program code for executing the methods illustrated in the flowcharts, for example, to: obtain a temperature of the power battery; obtain a characteristic frequency of the alternating pulse current, a minimum current at which lithium precipitation exists in the power battery, and a minimum current at which the solid electrolyte interface film decomposes according to the temperature of the power battery, wherein different temperatures of the power battery correspond to different characteristic frequencies of the alternating pulse current, different minimum currents at which lithium precipitation exists in the power battery, and different minimum currents at which the solid electrolyte interface film decomposes; obtain a charge-discharge current amplitude of the alternating pulse current according to the minimum current at which lithium precipitation exists in the power battery and the minimum current at which the solid electrolyte interface film decomposes; perform self-heating on the power battery using the alternating pulse current.
[0086] In particular, according to embodiments of the present application, the above reference to the flowcharts Figure 1 The described processes can be implemented as computer software programs. For example, an embodiment of the present application includes a computer program product comprising a computer program containing program code for executing the methods illustrated in the flowcharts, for example, to: obtain a temperature of the power battery; obtain a characteristic frequency of the alternating pulse current, a minimum current at which lithium precipitation exists in the power battery, and a minimum current at which the solid electrolyte interface film decomposes according to the temperature of the power battery, wherein different temperatures of the power battery correspond to different characteristic frequencies of the alternating pulse current, different minimum currents at which lithium precipitation exists in the power battery, and different minimum currents at which the solid electrolyte interface film decomposes; obtain a charge-discharge current amplitude of the alternating pulse current according to the minimum current at which lithium precipitation exists in the power battery and the minimum current at which the solid electrolyte interface film decomposes; perform self-heating on the power battery using the alternating pulse current.
[0087] In such embodiments, the computer program contains program code for executing the methods illustrated in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network by the communication section 1009, and / or installed from the detachable medium 1011. When the computer program is executed by the central processing unit (CPU) 1001, the above-described functions defined in the system of the present application are executed.
[0088] It should be noted that the computer-readable medium shown in the application can be a computer-readable signal medium or a computer-readable storage medium or any combination of the two. The computer-readable storage medium may, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or component, or any combination of the above. More specific examples of computer-readable storage media can include, but are not limited to, an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this application, the computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, device or component. In this application, the computer-readable signal medium can include a data signal carried in a baseband or as a carrier wave part of a carrier wave, which carries computer-readable program code. Such a propagated data signal can take many forms, including but not limited to an electromagnetic signal, an optical signal, or any suitable combination of the above. The computer-readable signal medium can also be any computer-readable medium that can send, propagate or transmit a program for use by or in conjunction with an instruction execution system, device or component. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to wireless, wire, optical cable, RF, etc., or any suitable combination of the above.
[0089] The flowcharts and block diagrams in the drawings illustrate the possible implementation architectures, functions and operation instructions of the systems, methods and computer program products according to various embodiments of the application. In this regard, each block in the flowchart or block diagram can represent a module, a program segment or a part of code, which contains one or more executable instructions for implementing the specified logical functions. It should also be noted that in some alternative implementations, the functions noted in the blocks can also occur in different order from that noted in the drawings. For example, two connected blocks can actually be executed substantially in parallel, and sometimes in reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and the combination of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for executing the specified functions or operation instructions, or can be implemented by a combination of dedicated hardware and computer instructions.
[0090] The units or modules described in the embodiments of the present application can be implemented in the form of software or in the form of hardware. The described units or modules can also be arranged in a processor. In some cases, the names of the units or modules do not constitute a limitation on the units or modules themselves.
[0091] The technical features of the above embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above embodiments are not described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present application.
[0092] The above embodiments only express several implementation manners of the present application, and the description is specific and detailed, but it should not be understood as a limitation on the patent scope of the application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.
Claims
1. A method of heating a power cell, characterized by, The method comprises the following steps: obtaining a temperature of a power battery; obtaining a characteristic frequency of an alternating pulse current, a minimum current at which lithium precipitation occurs in the power battery, and a minimum current at which a solid electrolyte interface film is decomposed according to the temperature of the power battery, wherein different temperatures of the power battery correspond to different characteristic frequencies of the alternating pulse current, different minimum currents at which lithium precipitation occurs in the power battery, and different minimum currents at which the solid electrolyte interface film is decomposed; obtaining a charge-discharge current amplitude of the alternating pulse current according to the minimum current at which lithium precipitation occurs in the power battery and the minimum current at which the solid electrolyte interface film is decomposed; using the alternating pulse current to perform self-heating on the power battery.
2. The method of claim 1, wherein, The step of obtaining the characteristic frequency of the alternating pulse current, the minimum current at which lithium precipitation occurs in the power battery, and the minimum current at which the solid electrolyte interface film is decomposed according to the temperature of the power battery comprises the following steps: determining a temperature interval in which the temperature of the power battery is located; obtaining the characteristic frequency of the alternating pulse current corresponding to the temperature interval from a pre-stored characteristic frequency table, wherein the characteristic frequency table comprises a plurality of characteristic frequencies corresponding to a plurality of different temperature intervals one by one; obtaining the minimum current at which lithium precipitation occurs in the power battery corresponding to the temperature interval from a pre-stored minimum current table at which lithium precipitation occurs, wherein the minimum current table at which lithium precipitation occurs comprises a plurality of minimum currents at which lithium precipitation occurs corresponding to a plurality of different temperature intervals one by one; obtaining the minimum current at which the solid electrolyte interface film is decomposed corresponding to the temperature interval from a pre-stored minimum current table at which the solid electrolyte interface film is decomposed, wherein the minimum current table at which the solid electrolyte interface film is decomposed comprises a plurality of minimum currents at which the solid electrolyte interface film is decomposed corresponding to a plurality of different temperature intervals one by one.
3. The method of claim 2, wherein the heating is performed by applying a voltage to the power cell. The method for obtaining the characteristic frequency corresponding to any temperature interval in the characteristic frequency table comprises the following steps: for any temperature interval, selecting a target temperature from the temperature interval; placing a plurality of power batteries of the same specification at different states of charge at the target temperature respectively and standing; when the plurality of power batteries reach the target temperature, performing electrochemical impedance spectroscopy test on each of the power batteries respectively to obtain a corresponding Bode plot; selecting a frequency value at which the reactance is equal to zero from each of the Bode plots respectively; obtaining an average value of the plurality of frequency values, and taking the average value as the characteristic frequency of the alternating pulse current corresponding to the temperature interval.
4. The method of claim 3, wherein the heating is performed by applying a voltage to the power cell. The method for obtaining the minimum current at which lithium precipitation occurs in the power battery corresponding to any temperature interval in the minimum current table at which lithium precipitation occurs comprises the following steps: performing constant-current charging on the power battery at the target temperature and a set charge rate to a preset state of charge to obtain an open-circuit voltage change of the power battery within a set time, and obtaining a voltage-time curve according to the open-circuit voltage change of the power battery within the set time; differentially processing the voltage-time curve, and determining the minimum current at which lithium precipitation occurs in the power battery corresponding to the temperature interval at the charge rate according to an inflection point in the voltage-time curve.
5. The method of claim 3, wherein the heating is performed by applying a voltage to the power battery. A method for obtaining the minimum current table of the solid electrolyte interface film decomposition corresponding to any temperature interval in the minimum current table of the solid electrolyte interface film decomposition, comprises: carrying out constant current discharge of the power battery at the target temperature and a set discharge rate to a preset state of charge to obtain the open circuit voltage change of the power battery within a set time, and obtaining a voltage-time curve according to the open circuit voltage change of the power battery within the set time; determining the minimum current of the solid electrolyte interface film decomposition corresponding to the temperature interval at the discharge rate according to the inflection point in the voltage-time curve.
6. The method of claim 1-5, wherein, The self-heating of the power battery by the alternating pulse current comprises: determining the sum of the charging time and the discharging time according to the characteristic frequency of the alternating pulse current; determining a relationship model of the charging current amplitude, the charging time, the discharging current amplitude and the discharging time of the alternating pulse current under the condition that the charging amount and the discharging amount are equal; solving the charging time and the discharging time according to the relationship model and the sum of the charging time and the discharging time; self-heating the power battery by the alternating pulse current based on the charging time and the discharging time.
7. The method of claim 1, wherein the heating is performed by a heater. In the process of self-heating the power battery by the alternating pulse current, further comprising: determining whether the temperature of the power battery reaches a set temperature; if yes, obtaining the temperature rising rate of the power battery according to the time consumption of the self-heating process and the temperature rise of the power battery.
8. A heating system for a power cell, characterized by comprises: an acquisition module for obtaining the temperature of the power battery; a current frequency determination module for obtaining the characteristic frequency of the alternating pulse current, the minimum current at which lithium precipitation exists in the power battery and the minimum current of the solid electrolyte interface film decomposition according to the temperature of the power battery, wherein different temperatures of the power battery correspond to different characteristic frequencies of the alternating pulse current, different minimum currents at which lithium precipitation exists in the power battery and different minimum currents of the solid electrolyte interface film decomposition; a current amplitude determination module for obtaining the charging and discharging current amplitude of the alternating pulse current according to the minimum current at which lithium precipitation exists in the power battery and the minimum current of the solid electrolyte interface film decomposition; a control module for self-heating the power battery by the alternating pulse current.
9. A vehicle characterized by comprising: comprises: the heating system of the power battery of the vehicle according to claim 8.
10. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the program to implement the heating method of the power battery according to any one of claims 1-7.