Lithium ion battery pulse heating boundary parameter testing method

Abstract

The invention relates to the technical field of battery detection, in particular to a lithium ion battery pulse heating boundary parameter testing method. According to the method, three key parameters including the battery SOC, the battery temperature and the battery working frequency are comprehensively considered, and a plurality of test condition groups are formed by combining different values, so that the response of the lithium ion battery to electronic pulse heating under different conditions can be systematically evaluated; the comprehensiveness is beneficial to more accurate understanding of the performance of the battery under different working conditions. Meanwhile, in the calculation of the pulse current, the induced electromotive force generated by the wire rod when the pulse current is injected into the battery is considered, the accuracy of pulse current calculation is improved through the detail processing, and then the reliability of the whole test result is improved.

Description

Technical Field

[0001] The invention relates to the technical field of battery detection, in particular to a method for testing pulse heating boundary parameters of a lithium ion battery. Background Art

[0002] Lithium-ion batteries cannot be charged quickly at low temperatures, and the vehicle's endurance will also be greatly reduced at low temperatures, which seriously restricts the development of electric vehicles. Therefore, a variety of heating technologies have been developed for low-temperature battery environments to increase the operating temperature of the battery.

[0003] At present, in addition to conventional PTC heating films and nickel-platinum heating methods, commonly used heating technologies usually also use battery pulse heating. Battery pulse heating generates heat directly inside the battery during the heating process, thereby achieving faster and more uniform heating. However, the effect of battery pulse heating is also limited by heating conditions. When the initial temperature of the battery is low, the conductivity of the electrolyte decreases, and under the action of high current and high frequency during the battery pulse heating process, lithium ions may grow unevenly on the surface of the electrode to form lithium dendrites, which poses a great safety hazard. Therefore, it is necessary to find the battery pulse heating boundary parameters under different conditions in battery pulse heating.

[0004] At present, the determination of battery pulse heating boundary parameters in the industry mainly takes the value range of the quotient of polarization voltage and battery impedance as the battery pulse heating boundary parameters. However, in the actual testing process, the wiring harness between the power output line of the detection cabinet and the lithium-ion battery to be tested has a certain length, which will cause the inductive impedance generated when the pulse current is injected from the detection cabinet into the lithium-ion battery to be tested to have a non-negligible impact on the polarization voltage of the battery. The above method does not take this influence into account when calculating the battery pulse heating boundary parameters, which leads to deviations in the calculation of the battery pulse heating boundary parameters and reduces the accuracy of the calculation of the battery pulse heating boundary parameters. It can be seen that considering this influence is crucial to accurately calculate the battery pulse heating boundary parameters. Summary of the invention

[0005] In order to avoid and overcome the technical problems existing in the prior art, the present invention provides a lithium ion battery pulse heating boundary parameter testing method. The present invention can effectively improve the accuracy of battery pulse heating boundary parameter calculation during the battery pulse heating process.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for testing pulse heating boundary parameters of a lithium-ion battery comprises the following testing steps:

[0008] S1, obtaining the battery operating frequency of the lithium-ion battery to be tested having a reference electrode at each battery SOC and each battery temperature;

[0009] S2, let the battery SOC, battery temperature and battery operating frequency be the test condition group of the lithium-ion battery to be tested, and different values ​​of the battery SOC, battery temperature and battery operating frequency constitute different test condition groups;

[0010] S3. Under each test condition group, different pulse currents are used to perform pulse heating of a set time on the lithium-ion battery to be tested, and the potential difference between the negative electrode of the battery and the reference electrode during the pulse heating is obtained; and when calculating the pulse current, the induced electromotive force generated by the wire used to inject the pulse current into the lithium-ion battery to be tested is included in the calculation of the pulse current;

[0011] S4. Based on the obtained potential difference, determine whether the lithium ion battery to be tested has lithium dendrite precipitation: if the potential difference is greater than the potential difference threshold, it means that the current pulse current will not cause lithium dendrite precipitation; otherwise, it means that the current pulse current will cause lithium dendrite precipitation, and a new lithium ion battery to be tested needs to be replaced, and then retest according to steps S1 to S3;

[0012] S5. In the absence of lithium dendrite precipitation, the minimum and maximum values ​​of all pulse currents that make the potential difference within the set potential difference range under the current test condition group are counted; the minimum value is the lower limit value of the electronic pulse heating boundary parameter of the lithium ion battery to be tested under the current test condition group; the maximum value is the upper limit value of the electronic pulse heating boundary parameter of the lithium ion battery to be tested under the current test condition group.

[0013] As a further solution of the present invention: the calculation formula of the pulse current is expressed as follows:

[0014]

[0015] U cell,t =U p,t -U L,t ;

[0016] U p,t =|U limit,t -U OCV,t |;

[0017] In the formula, I t It represents the pulse current used for pulse current heating of the lithium-ion battery under the tth test condition group; U OCV,t Indicates the open circuit voltage of the lithium-ion battery to be tested under the tth test condition group; U limit,t Indicates the battery cut-off voltage set for the lithium-ion battery to be tested under the tth test condition group; U p,tIndicates the polarization voltage of the lithium-ion battery to be tested under the tth test condition group; U L,t It means that under the tth test condition group, when the pulse current is injected into the lithium-ion battery to be tested, the wiring harness injected with the pulse current generates the induced electromotive force of the lithium-ion battery to be tested; U cell,t Indicates U p,t and U L,t The difference between |Z t | represents the battery impedance Z of the lithium-ion battery to be tested under the tth test condition group t Impedance modulus value.

[0018] As a further solution of the present invention: when the lithium-ion battery to be tested is subjected to pulse current heating, the pulse current corresponding to each test condition group is first calculated by the pulse current calculation formula; then the lithium-ion battery to be tested is placed under the current test condition group, and all the pulse currents are used in turn to perform pulse heating on the lithium-ion battery to be tested, and then the corresponding voltage difference is obtained, and it is determined whether lithium dendrites are precipitated.

[0019] As a further solution of the present invention: the impedance modulus calculation formula is as follows:

[0020]

[0021] In the formula, R e,t It represents the real impedance of the lithium-ion battery under the tth test condition group when the phase angle is equal to zero; I m,t It represents the battery imaginary impedance when the phase angle of the lithium-ion battery to be tested is zero under the tth test condition group.

[0022] As a further solution of the present invention: the specific content of step S3 is as follows:

[0023] S31, locking the values ​​of the battery SOC and the battery temperature in the test condition group, gradually changing the value of the battery operating frequency from high to low within the set battery operating frequency value range, and under the same battery operating frequency, sequentially using pulse currents from small to large within the set pulse current value range to perform pulse heating of the lithium-ion battery to be tested for a set time, so as to obtain the potential difference between the battery negative electrode and the reference electrode during the pulse heating;

[0024] S32, only locking the value of the battery temperature in the test condition group, gradually changing the value of the battery temperature from high to low within the set battery temperature value range, and gradually changing the value of the battery operating frequency from high to low within the set battery operating frequency value range, and under the same group of battery temperature and battery operating frequency, using pulse current from small to large in the set pulse current value range to perform pulse heating for a set time on the lithium-ion battery to be tested, so as to obtain the potential difference between the negative electrode of the battery and the reference electrode during the pulse heating;

[0025] S33. Gradually change the value of the battery SOC from high to low within the set battery SOC value range, gradually change the value of the battery temperature from high to low within the set battery temperature value range, and at the same time gradually change the value of the battery operating frequency from high to low within the set battery operating frequency value range, and under the same set of battery temperatures, battery SOC and battery operating frequencies, use pulse currents from small to large in the set pulse current value range to perform pulse heating for a set time on the lithium-ion battery to be tested, so as to obtain the potential difference between the battery negative electrode and the reference electrode during the pulse heating.

[0026] As a further solution of the present invention: during the pulse heating process, when the battery SOC of the lithium-ion battery to be tested is above 50%, the lithium-ion battery to be tested is first pulse-discharged with a pulsating current to set a discharge time, and then the pulse current is used to pulse-charge the lithium-ion battery to be tested to set a charging time;

[0027] When the battery SOC of the lithium-ion battery to be tested is lower than 50%, the lithium-ion battery to be tested is first pulse-charged using a pulse current to set a charging time, and then the lithium-ion battery to be tested is pulse-discharged using the pulse current to set a discharging time.

[0028] As a further solution of the present invention: during the pulse heating process, the set time length is the sum of the set charging time and the set discharging time; and the set time length is an integer multiple of the reciprocal of the frequency F0 when the phase angle of the lithium-ion battery to be tested is equal to zero.

[0029] As a further solution of the present invention: the pulse current changes periodically in a sinusoidal wave, a triangular wave or a square wave; and when the pulse current is used to perform pulse charging on the lithium ion battery to be tested, the pulse charging peak current I of the lithium ion battery to be tested under the tth test condition group is max,CH,t Less than or equal to U up,limit -U OCV,t Impedance modulus |Z t |, and at the same time less than the maximum current I allowed to pass through the lithium-ion battery under test limit ;

[0030] When a pulse current is used to perform pulse discharge on the lithium-ion battery to be tested, the pulse discharge peak current I of the lithium-ion battery to be tested under the tth test condition group is max,DC,t Less than or equal to U OCV,t -U low,limit Impedance modulus |Z t |, and is less than the maximum current I allowed to pass through the lithium-ion battery under test limit ; U up,limit Indicates the pulse charging cut-off voltage of the lithium-ion battery to be tested; U low,limit Indicates the pulse discharge cut-off voltage of the lithium-ion battery to be tested.

[0031] As a further solution of the present invention: during the pulse heating process, the initial value of the battery operating frequency is the frequency corresponding to a zero phase angle between the real impedance and the imaginary impedance in the battery EIS impedance spectrum of the lithium ion battery to be tested.

[0032] As a further solution of the present invention: during the pulse heating process, the initial value of the battery temperature is in the range of [-5°C, 5°C]; the initial value of the pulse current is in the range of [0.1C, 3C].

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention comprehensively considers the three key parameters of battery SOC (state of charge), battery temperature and battery operating frequency, and forms multiple test condition groups by combining different values, so as to systematically evaluate the response of lithium-ion batteries to electronic pulse heating under different conditions. This comprehensiveness helps to more accurately understand the performance of batteries under different working conditions. At the same time, in the calculation of pulse current, the induced electromotive force generated by the wire when the pulse current is injected into the battery is taken into account. This detail processing improves the accuracy of pulse current calculation, thereby improving the reliability of the entire test result.

[0035] 2. The present invention can quickly determine whether the current pulse current will cause lithium dendrites to precipitate by real-time monitoring of the potential difference between the negative electrode of the battery and the reference electrode. This real-time monitoring mechanism not only improves the test efficiency, but also enables timely measures (such as replacing the battery) to be taken when potential problems (such as lithium dendrite precipitation) are found, avoiding the waste of test resources and potential safety risks.

[0036] 3. The present invention determines the boundary parameters of electronic pulse heating by statistically analyzing the minimum and maximum values ​​of the pulse current that keep the potential difference within the set range. These boundary parameters are of great significance in guiding the formulation of pulse heating strategies in practical applications, and help to maximize the use of pulse heating technology to improve battery performance while ensuring battery safety.

[0037] 4. The entire test process of the present invention is clear, the steps are clear, and it has strong repeatability and verifiability. This means that different researchers or laboratories can perform tests according to the same steps and methods to obtain consistent or comparable results, which enhances the credibility and application value of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a test flow chart of the present invention.

[0039] Figure 2 In the present invention, U cell , U L and U p 's change curve graph.

[0040] Figure 3 It shows the curves of voltage difference and battery operating current changing with time during pulse heating at 0℃-5Hz-0.5C-50%.

[0041] Figure 4 It shows the curves of voltage difference and battery operating current changing with time during pulse heating at 0℃-1Hz-0.5C-50%.

[0042] Figure 5 It is a curve showing the change of voltage difference and battery operating current over time during pulse heating at 0℃-5Hz-2C-50%.

[0043] Figure 6 It is a curve showing the change of voltage difference and battery operating current over time during pulse heating at -10℃-1Hz-0.5C-50%.

[0044] Figure 7 It is a curve showing the change of voltage difference and battery operating current over time during pulse heating at -15℃-1Hz-0.5C-50%.

[0045] Figure 8 It is a graph showing the change of voltage difference and battery operating temperature over time during pulse heating at -20℃-50Hz-3C-9%.

[0046] Fig. 9 It is a graph showing the change of voltage difference and battery operating temperature over time during pulse heating at -20℃-50Hz-3C-50%. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] See also Figures 1 to 9 , the present invention includes the following contents.

[0049] 1. Get the battery operating frequency.

[0050] Obtain the battery operating frequency of the lithium-ion battery to be tested with a reference electrode at each battery SOC and each battery temperature. The details are as follows:

[0051] S11. The lithium-ion battery to be tested is a three-electrode battery with a reference electrode. A small current lithium plating is performed on a charge and discharge detection cabinet, and a temperature sensor is arranged on its surface.

[0052] S12, placing the lithium-ion battery to be tested with a temperature sensor arranged on the surface in a constant temperature box to change the battery temperature of the lithium-ion battery to be tested, and at the same time charging and discharging the lithium-ion battery to be tested to change the battery SOC of the lithium-ion battery to be tested, thereby adjusting the battery temperature and battery SOC of the lithium-ion battery to be tested.

[0053] S13, at different battery SOC and battery temperature, the lithium ion battery to be tested is subjected to EIS test to obtain the corresponding battery operating frequency and pulse voltage value range [U low,limit ,U up,limit ] and pulse current range [0,I max ].

[0054] 2. Calculate the pulse current.

[0055] The battery SOC, the battery temperature and the battery operating frequency are set as the test condition group of the lithium-ion battery to be tested, and different values ​​of the battery SOC, the battery temperature and the battery operating frequency constitute different test condition groups.

[0056] When the lithium-ion battery to be tested is subjected to pulse current heating, the pulse current corresponding to each test condition group is first calculated by the pulse current calculation formula; then the lithium-ion battery to be tested is placed under the current test condition group, and all the pulse currents are used in turn to perform pulse heating on the lithium-ion battery to be tested, and then the corresponding voltage difference is obtained, and it is determined whether lithium dendrites are precipitated. Figure 1 and Figure 2 As shown in the figure, during the pulse heating process of the lithium-ion battery to be tested, in addition to the polarization voltage U generated by the impedance of the lithium-ion battery itself, cell,t(U cell ) and U p,t (U p ) In addition, due to the influence of pulse current injection, the wire between the test cabinet and the lithium-ion battery to be tested will also produce corresponding impedance, that is, generate induced electromotive force. The voltage corresponding to the induced electromotive force is the inductive reactance polarization voltage U L,t (U L ), this part of the inductive reactance and the impedance of the lithium-ion battery itself will increase the actual voltage of the lithium-ion battery to be tested. Therefore, when calculating the maximum value of the pulse current, the induced electromotive force should be included in the calculation range.

[0057] The calculation formula of pulse current is shown in formula (1)-formula (3):

[0058]

[0059] U cell,t =U p,t -U L,t (2)

[0060] U p,t =|U limit,t -U OCV,t | (3)

[0061] As a further solution of the present invention:

[0062] In the formula, I t It indicates the pulse current used for pulse current heating of the lithium-ion battery under the t-th test condition group, which can be detected in real time through the corresponding current rheology. OCV,t It means that under the tth test condition group, the open circuit voltage of the lithium-ion battery to be tested can be detected in real time by a voltmeter installed at the voltage end of the lithium-ion battery to be tested. limit,t Indicates the battery cutoff voltage set for the lithium-ion battery to be tested under the tth test condition group, which can be obtained in the EIS test. p,t Indicates the polarization voltage of the lithium-ion battery to be tested under the tth test condition group, which can be obtained in the EIS test. L,t It means that under the tth test condition group, when the pulse current is injected into the lithium-ion battery to be tested, the induced electromotive force generated by the wiring harness injected with the pulse current to the lithium-ion battery to be tested can be detected by a voltmeter. cell,t Indicates U p,t and U L,t The difference between |Z t | represents the battery impedance Z of the lithium-ion battery to be tested under the tth test condition group t Impedance modulus value.

[0063] The impedance modulus calculation formula is shown in formula (4):

[0064]

[0065] In the formula, R e,t It indicates the real impedance of the lithium-ion battery under the tth test condition group when the phase angle is equal to zero, which can be detected by an ohmmeter. m,t It indicates the battery imaginary impedance when the phase angle of the lithium-ion battery to be tested is zero under the tth test condition group, which can be detected by an ohmmeter.

[0066] 3. Perform pulse heating.

[0067] Under each test condition group, different pulse currents are used to perform pulse heating of a set duration on the lithium-ion battery to be tested, and the potential difference between the negative electrode of the battery and the reference electrode during the pulse heating is obtained.

[0068] The specific process is as follows:

[0069] S31. Lock the values ​​of the battery SOC and battery temperature in the test condition group, gradually change the value of the battery operating frequency from high to low within the set battery operating frequency value range, and under the same battery operating frequency, use pulse current from small to large in the set pulse current value range to perform pulse heating on the lithium-ion battery to be tested for a set time, so as to obtain the potential difference between the battery negative electrode and the reference electrode during the pulse heating.

[0070] S32, only lock the value of the battery temperature in the test condition group, gradually change the value of the battery temperature from high to low within the set battery temperature value range, and gradually change the value of the battery operating frequency from high to low within the set battery operating frequency value range, and under the same group of battery temperatures and battery operating frequencies, use pulse currents from small to large in the set pulse current value range to perform pulse heating for a set time on the lithium-ion battery to be tested, so as to obtain the potential difference between the battery negative electrode and the reference electrode during the pulse heating.

[0071] S33. Gradually change the value of the battery SOC from high to low within the set battery SOC value range, gradually change the value of the battery temperature from high to low within the set battery temperature value range, and at the same time gradually change the value of the battery operating frequency from high to low within the set battery operating frequency value range, and under the same set of battery temperatures, battery SOC and battery operating frequencies, use pulse currents from small to large in the set pulse current value range to perform pulse heating for a set time on the lithium-ion battery to be tested, so as to obtain the potential difference between the battery negative electrode and the reference electrode during the pulse heating.

[0072] During the pulse heating process, when the battery SOC of the lithium-ion battery to be tested is above 50%, the lithium-ion battery to be tested is first pulse-discharged with a pulsating current to set the discharge time, and then the pulse current is used to pulse charge the lithium-ion battery to be tested to set the charging time. When the battery SOC of the lithium-ion battery to be tested is lower than 50%, the lithium-ion battery to be tested is first pulse-charged with a pulse current to set the charging time, and then the lithium-ion battery to be tested is pulse-discharged with the pulse current to set the discharge time.

[0073] During the pulse heating process, the set time is the sum of the set charging time and the set discharging time; and the set time is an integer multiple of the reciprocal of the frequency F0 when the phase angle of the lithium-ion battery to be tested is equal to zero.

[0074] During the pulse heating process, the initial value of the battery operating frequency is the frequency corresponding to a zero phase angle between the real impedance and the imaginary impedance in the battery EIS impedance spectrum of the lithium-ion battery to be tested.

[0075] During the pulse heating process, the initial value of the battery temperature ranges from [-5°C, 5°C]; the initial value of the pulse current ranges from [0.1C, 3C].

[0076] 4. Determine whether lithium dendrites are precipitated.

[0077] Based on the obtained potential difference, determine whether the lithium-ion battery to be tested has lithium dendrite precipitation: if the potential difference is greater than the potential difference threshold (the potential difference threshold is 0V), it means that the current pulse current will not cause lithium dendrite precipitation; otherwise, it means that the current pulse current will cause lithium dendrite precipitation. At this time, it is necessary to replace a new lithium-ion battery to be tested, and then re-test according to the previous content.

[0078] 5. Determine the pulse heating boundary parameters.

[0079] In the absence of lithium dendrite precipitation, the minimum and maximum values ​​of all pulse currents that make the potential difference within the set potential difference range (the set potential difference range is 0-100mV) under the current test condition group are counted; the minimum value is the lower limit value of the electronic pulse heating boundary parameter of the lithium ion battery to be tested under the current test condition group; the maximum value is the upper limit value of the electronic pulse heating boundary parameter of the lithium ion battery to be tested under the current test condition group.

[0080] Embodiment 1:

[0081] Combination Figure 1-Figure 4 , the battery was assembled and formed under the above conditions, and the following operations and analyses were performed: when the battery temperature was 0°C, the battery SOC was 50%, and the battery operating frequency was 5Hz and 1Hz respectively, the lithium-ion battery to be tested was pulse heated with a pulse current of 0.5C, and the voltage difference in the three-electrode battery was observed.

[0082] Figure 3 It shows the curves of voltage difference and battery operating current changing with time during pulse heating at 0℃-5Hz-0.5C-50%. Figure 4 The curves of voltage difference and battery operating current changing with time during pulse heating at 0℃-1Hz-0.5C-50%. Figure 3 and Figure 4 It can be seen that during the pulse heating process with a pulse current of 0.5C, when the battery operating frequency is 5Hz and 1Hz, the voltage difference is 0.093V and 0.079V respectively, no lithium dendrites are generated, and various parameters of this condition are recorded.

[0083] Embodiment 2:

[0084] Combination Figure 1 , Figure 2 , Figure 4 , Figure 5 , Figure 6 and Figure 7 , the battery was assembled and formed under the above conditions, and the following operations and analyses were performed: the lithium-ion battery to be tested with a battery SOC of 50% was pulse heated at battery temperatures of 0°C, -10°C and -15°C, a battery operating frequency of 1Hz, and a pulse current of 0.5C, and the potential difference of the three-electrode battery was observed.

[0085] Figure 5 It is a curve showing the change of voltage difference and battery operating current over time during pulse heating at 0℃-5Hz-2C-50%. Figure 6 It is a curve showing the change of voltage difference and battery operating current over time during pulse heating at -10℃-1Hz-0.5C-50%. Figure 7 It is a curve showing the change of voltage difference and battery operating current over time during pulse heating at -15℃-1Hz-0.5C-50%.

[0086] from Figure 5 , Figure 6 and Figure 7 It can be seen that when the battery temperature is 0°C, the minimum voltage difference is 0.093V, no lithium dendrites are generated, and the various parameters of this condition are recorded. When the battery temperature is -10°C, the minimum voltage difference is 0.016V, no lithium dendrites are generated, and the various parameters of this condition are recorded. When the battery temperature is -15°C, the minimum voltage difference is -0.013V, and lithium dendrites are generated.

[0087] Embodiment three:

[0088] Combination Figure 8 and Fig. 9, the battery was assembled and formed under the above conditions, and the following operations and analyses were performed: At a battery temperature of -20°C, a pulse current of 3C and a battery operating frequency of 50Hz, the lithium-ion battery to be tested was pulse heated at a battery SOC of 50% and a battery SOC of 10%, respectively, and the change in the voltage difference in the three-electrode battery was observed.

[0089] from Figure 8 and Fig. 9 It can be seen that the minimum voltage difference when the battery SOC is 50% is 0.009V, no lithium dendrites are generated, the battery cell temperature rises from -18.24℃ to -17.82℃, and the various parameters of this condition are recorded. The minimum voltage difference when the battery SOC is 50% is -0.179V, lithium dendrites are generated, and the battery cell temperature rises from -18.29℃ to -17.81℃.

[0090] By adjusting the battery's state of charge, current, frequency and temperature, the battery pulse heating boundary parameters can be obtained.

[0091] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A lithium-ion battery pulse heating boundary parameter testing method, characterized in that: The test steps include: S1, obtaining the battery operating frequency of the lithium-ion battery to be tested having a reference electrode at each battery SOC and each battery temperature; S2, let the battery SOC, battery temperature and battery operating frequency be the test condition group of the lithium-ion battery to be tested, and different values ​​of the battery SOC, battery temperature and battery operating frequency constitute different test condition groups; S3, under each test condition group, using different pulse currents to perform pulse heating of a set time on the lithium-ion battery to be tested, and obtaining the potential difference between the negative electrode of the battery and the reference electrode during the pulse heating; And when calculating the pulse current, the induced electromotive force generated by the wire used to inject the pulse current into the lithium-ion battery to be tested is included in the calculation of the pulse current; S4. Based on the obtained potential difference, determine whether the lithium ion battery to be tested has lithium dendrite precipitation: if the potential difference is greater than the potential difference threshold, it means that the current pulse current will not cause lithium dendrite precipitation; otherwise, it means that the current pulse current will cause lithium dendrite precipitation, and a new lithium ion battery to be tested needs to be replaced, and then retest according to steps S1 to S3; S5. In the absence of lithium dendrite precipitation, the minimum and maximum values ​​of all pulse currents that make the potential difference within the set potential difference range under the current test condition group are counted; the minimum value is the lower limit value of the electronic pulse heating boundary parameter of the lithium ion battery to be tested under the current test condition group; the maximum value is the upper limit value of the electronic pulse heating boundary parameter of the lithium ion battery to be tested under the current test condition group.

2. A lithium-ion battery pulse heating boundary parameter testing method according to claim 1, characterized in that: The calculation formula of pulse current is as follows: IN cell,t =U p,t -IN L,t ; IN p,t =|U limit,t -IN OCV,t |; In the formula, I t It represents the pulse current used for pulse current heating of the lithium-ion battery under the tth test condition group; U OCV,t Indicates the open circuit voltage of the lithium-ion battery to be tested under the tth test condition group; U limit,t Indicates the battery cut-off voltage set for the lithium-ion battery to be tested under the tth test condition group; U p,t Indicates the polarization voltage of the lithium-ion battery to be tested under the tth test condition group; U L,t It means that under the tth test condition group, when the pulse current is injected into the lithium-ion battery to be tested, the wiring harness injected with the pulse current generates the induced electromotive force of the lithium-ion battery to be tested; U cell,t Indicates U p,t and U L,t The difference between |Z t | represents the battery impedance Z of the lithium-ion battery to be tested under the tth test condition group t Impedance modulus value.

3. A lithium-ion battery pulse heating boundary parameter testing method according to claim 1 or 2, characterized in that: When the lithium-ion battery to be tested is subjected to pulse current heating, the pulse current corresponding to each test condition group is first calculated by the pulse current calculation formula; then the lithium-ion battery to be tested is placed under the current test condition group, and all the pulse currents are used in turn to perform pulse heating on the lithium-ion battery to be tested, and then the corresponding voltage difference is obtained, and it is determined whether lithium dendrites are precipitated.

4. A lithium-ion battery pulse heating boundary parameter testing method according to claim 3, characterized in that: The impedance modulus calculation formula is as follows: In the formula, R e,t It represents the real impedance of the lithium-ion battery under the tth test condition group when the phase angle is equal to zero; I m,t It represents the battery imaginary impedance when the phase angle of the lithium-ion battery to be tested is zero under the tth test condition group.

5. A lithium-ion battery pulse heating boundary parameter testing method according to claim 4, characterized in that: The specific content of step S3 is as follows: S31, locking the values ​​of the battery SOC and the battery temperature in the test condition group, gradually changing the value of the battery operating frequency from high to low within the set battery operating frequency value range, and under the same battery operating frequency, sequentially using pulse currents from small to large within the set pulse current value range to perform pulse heating of the lithium-ion battery to be tested for a set time, so as to obtain the potential difference between the battery negative electrode and the reference electrode during the pulse heating; S32, only locking the value of the battery temperature in the test condition group, gradually changing the value of the battery temperature from high to low within the set battery temperature value range, and gradually changing the value of the battery operating frequency from high to low within the set battery operating frequency value range, and under the same group of battery temperature and battery operating frequency, using pulse current from small to large in the set pulse current value range to perform pulse heating for a set time on the lithium-ion battery to be tested, so as to obtain the potential difference between the negative electrode of the battery and the reference electrode during the pulse heating; S33. Gradually change the battery SOC value from high to low within the set battery SOC value range, gradually change the battery temperature value from high to low within the set battery temperature value range, and at the same time gradually change the battery operating frequency value from high to low within the set battery operating frequency value range, and under the same set of battery temperatures, battery SOC and battery operating frequencies, use pulse currents from small to large in the set pulse current value range to perform pulse heating for a set time on the lithium-ion battery to be tested, so as to obtain the potential difference between the battery negative electrode and the reference electrode during the pulse heating.

6. A lithium-ion battery pulse heating boundary parameter testing method according to claim 5, characterized in that: During the pulse heating process, when the battery SOC of the lithium-ion battery to be tested is above 50%, the lithium-ion battery to be tested is firstly pulse-discharged with a pulsating current to set a discharge time, and then the pulse current is used to pulse-charge the lithium-ion battery to be tested to set a charging time; When the battery SOC of the lithium-ion battery to be tested is lower than 50%, the lithium-ion battery to be tested is first pulse-charged using a pulse current to set a charging time, and then the lithium-ion battery to be tested is pulse-discharged using the pulse current to set a discharging time.

7. A lithium-ion battery pulse heating boundary parameter testing method according to claim 6, characterized in that: During the pulse heating process, the set time length is the sum of the set charging time and the set discharging time; and the set time length is the reciprocal of the frequency F0 when the phase angle of the lithium-ion battery to be tested is equal to zero.

8. A lithium-ion battery pulse heating boundary parameter testing method according to claim 7, characterized in that: The pulse current changes periodically in the form of a sine wave, a triangular wave or a square wave; and when the pulse current is used to perform pulse charging on the lithium-ion battery to be tested, the pulse charging peak current I of the lithium-ion battery to be tested under the tth test condition group is max,CH,t Less than or equal to U up,limit -U OCV,t Impedance modulus |Z t |, and at the same time less than the maximum current I allowed to pass through the lithium-ion battery under test limit ; When a pulse current is used to perform pulse discharge on the lithium-ion battery to be tested, the pulse discharge peak current I of the lithium-ion battery to be tested under the tth test condition group is max,DC,t Less than or equal to U OCV,t -U low,limit Impedance modulus |Z t |, and is less than the maximum current I allowed to pass through the lithium-ion battery under test limit ; U up,limit Indicates the pulse charging cut-off voltage of the lithium-ion battery to be tested; U low,limit Indicates the pulse discharge cut-off voltage of the lithium-ion battery to be tested.

9. A lithium-ion battery pulse heating boundary parameter testing method according to claim 8, characterized in that: During the pulse heating process, the initial value of the battery operating frequency is the frequency corresponding to a zero phase angle between the real impedance and the imaginary impedance in the battery EIS impedance spectrum of the lithium-ion battery to be tested.

10. A lithium-ion battery pulse heating boundary parameter testing method according to claim 9, characterized in that: During the pulse heating process, the initial value of the battery temperature ranges from [-5°C, 5°C]; the initial value of the pulse current ranges from [0.1C, 3C].

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