A method of analyzing the constitution of internal resistance of a battery

Abstract

The application discloses a method for analyzing the constitution of battery internal resistance. The steps are as follows: based on the voltage data collected according to a preset first rule, target data is extracted according to a preset second rule, a differential curve of target internal resistance relative to target logarithmic conversion frequency is constructed, a junction point where electrochemical reaction polarization and concentration polarization play roles in a frequency domain is identified, and the resistance values of electrochemical activation internal resistance and concentration polarization internal resistance are evaluated; and the membrane diffusion internal resistance and charge transfer internal resistance can be further evaluated according to the collected voltage data. The test current ratio applied in the analysis and test of the application is smaller than the pulse current ratio used in conventional direct current internal resistance test, and the battery is not damaged; the data collection process can be embedded into the battery charging and discharging test process without relying on an electrochemical workstation, and the test is relatively convenient and flexible, and especially for internal resistance analysis with test temperature requirements, the feasibility is relatively high.

Description

Technical Field

[0001] This invention relates to the field of battery internal resistance analysis technology, and in particular to a method for analyzing the composition of battery internal resistance. Background Technology

[0002] DC impedance and AC impedance are important indicators for evaluating the polarization of a battery.

[0003] Existing DC-IR analysis methods apply a constant current pulse of a relatively large current to the battery for a certain period of time, and calculate the DC-IR corresponding to that period by dividing the voltage change before and after the pulse by the current change. While this method is extremely simple to operate, it cannot effectively identify the boundary between the effects of electrochemical polarization and concentration polarization. Consequently, it cannot objectively assess the values ​​(magnitudes) and variation patterns of electrochemical activation resistance and concentration resistance, nor can it estimate film diffusion resistance and charge transfer resistance. This method has certain limitations in resolving battery impedance information. CN113093038A uses conventional DCIR testing. First, it obtains the time series of voltage difference values ​​during pulsed charging and discharging. Then, it compares each difference value sequentially with the first difference value, using the inflection point of the difference change as the starting point for the concentration polarization resistance to take effect. This method analyzes voltage difference change data from a time domain perspective. It requires the testing equipment to have the ability to collect voltage data at extremely dense time intervals (Δt no greater than 0.001 seconds), and the pulse current ratio used is relatively large. Repeated use of a large pulse current ratio may have a negative effect on the battery.

[0004] AC internal resistance meters are used to measure the ohmic internal resistance of batteries, but provide limited information. Electrochemical impedance spectroscopy (EIS) can assess impedance across multiple timescales, but requires a costly electrochemical workstation. When studying the impedance characteristics of a battery at a specific temperature, the workstation needs to be moved to a temperature-controlled chamber, connected to a computer, and its test leads and battery clamps placed inside the chamber. Transferring a battery in a specific state to the workstation's clamps is also a complex procedure. Generally, to prevent equipment damage, electrochemical workstations should not be moved arbitrarily. Summary of the Invention

[0005] The purpose of this invention is to address the technical deficiencies in the existing technology by providing a method for analyzing the internal resistance of a battery. This method does not rely on an electrochemical workstation and can effectively identify the boundary points where electrochemical reaction polarization and concentration polarization play their roles in the frequency domain. It can then evaluate the resistance values ​​of electrochemical activation internal resistance and concentration polarization internal resistance, and can further calculate the film diffusion internal resistance and charge transfer internal resistance.

[0006] A method for analyzing the composition of battery internal resistance includes the following steps:

[0007] Step 1: Place the battery under test in a preset state at a preset temperature environment; in the preset state, the current of the battery under test is I0, and the value of current I0 is in the range of 0-0.1C;

[0008] Step 2: Collect the applied test current I of the battery according to the preset first rule. app The instant before and the applied test current I app The voltage during the period forms a set of acquisition time t. test ={t0,t1,t2,…,t n The corresponding set of collected voltages U test ={U0,U1,U2,…,U n}, t0=0, U0 is the voltage sampled instantaneously before the test current is applied;

[0009] Step 3: Extract target data from the voltage and time data set in Step 2 according to the preset second rule, and construct the target voltage set U. filter and target time set t filter ;

[0010] Step 4: Based on the target time set t filter and target voltage set U filter Construct the target logarithmic transformation frequency set f filter and the target internal resistance set R filter ; Target time set t filter Target voltage set U filter Target logarithmic transformation frequency set f filter and the target internal resistance set R filter The elements are in a one-to-one correspondence; plot the differential curve of the target internal resistance relative to the target logarithmic transformation frequency, and mark the x-coordinate of the differential curve when it reaches its maximum value in the range of logarithmic transformation frequency ≤ 0.1Hz. c f c It is the boundary point where electrochemical reaction polarization and concentration polarization exert their effects in the frequency domain, f c The corresponding target internal resistance is R c ;

[0011] For any target time t x ∈t filter The corresponding target logarithmic transformation frequency set f filter The target logarithmic transformation frequency element f x =log(C / t) x C is the conversion factor, with a value ranging from 0.25 to 0.50;

[0012] For any target time t x ∈t filter The corresponding target internal resistance set Rfilter The target internal resistance R in x =(U x -U0) / (I app -I0), U x It is any target time t x The corresponding voltage; then R c =(U c -U0) / (I app -I0);

[0013] Step 5: Calculate the electrochemical activation internal resistance R act Concentration resistance R diff And estimate the membrane diffusion resistance R f and charge transfer internal resistance R ct Electrochemical activation internal resistance R act =R c -R ohm Concentration resistance R diff =R sum -R c Membrane diffusion internal resistance R f =R1-R ohm internal resistance of charge transfer R ct =R c -R1, R ohm The internal resistance of the battery to be tested is in ohms.

[0014] R1=(U1-U0) / (I app -I0);

[0015] R sum Applying a test current I to the battery in step two app The DC internal resistance corresponding to the action time of 25s, i.e., the sampling time t = 25s, U sum R is the corresponding sampling voltage. sum =(U sum -U0) / (I app -I0).

[0016] Based on the relationship between the real part of the electrochemical impedance spectrum of a battery and its logarithmic frequency, this invention discovers that the abscissa f of the differential curve of the target internal resistance of the battery and the logarithmic conversion frequency reaches its maximum value in the range of logarithmic conversion frequency ≤ 0.1 Hz. c It can be used as the boundary point where electrochemical reaction polarization and concentration polarization play their roles in the frequency domain, and the composition of the battery's DC internal resistance can be analyzed accordingly.

[0017] In this invention, the process of transforming the test time of the battery under test into a logarithmic transformation frequency is designed based on the relationship between the battery's electrochemical impedance spectrum and its DC internal resistance in the time and frequency domains, and a set of logarithmic transformation frequencies f is created. filter any element f inx The calculation formula ultimately allows the analysis of the battery's DC internal resistance to be performed in the frequency domain, similar to an AC impedance spectrum. Analyzing the problem from a frequency domain perspective reduces the requirements for the data acquisition time resolution of the equipment.

[0018] In step one, the preset states include the battery under test being in a static state and a very low current charging / discharging state. When in a static state, the static time should be no less than 1 hour. When in a very low current charging / discharging state, the charging / discharging time should be no less than 2 minutes. The default charging current is positive and the discharging current is negative. The unit of current is ampere (A).

[0019] In step two, the test current I applied to the battery is collected according to the preset first rule. app The instant before and the applied test current I app The voltage steps during the process include:

[0020] Used to calculate the electrochemical activation internal resistance R act Concentration resistance R diff When a test current I is applied app The duration of action t≤t s When the time change is ≥0.03s or the voltage change is ≥0.005V, at least one voltage data point should be collected; when t>t s At least one voltage data point must be collected when the time change is ≥1s or the voltage change is ≥0.01V.

[0021] Used to calculate the internal resistance of membrane diffusion R f and charge transfer internal resistance R ct In addition to satisfying the above conditions for calculating the electrochemical activation internal resistance R, act Concentration resistance R diff In addition to the rules for acquiring voltage data at the time, the applied test current I must also be satisfied. app The acquisition time t1 ∈ [0.002s, 0.008s] corresponds to the first voltage data U1 acquired later.

[0022] If the acquisition time t1 does not satisfy t1∈[0.002s,0.008s], then it can be adjusted in any of the following ways to make t1 satisfy the condition:

[0023] Adjust the test current I app Until t1 is satisfied;

[0024] Set when the test current I is applied app The duration of action t ≤ 0.01s, and the change in time ≥ t d At least one voltage data point should be collected, t d ∈[0.002s,0.008s].

[0025] Among them, when collecting the voltage of the battery under test, the applied test current I app The following conditions must be met:

[0026] When I0 = 0, (5A·mΩ / R) ohm )≤|I app |≤(50A·mΩ / R ohm The internal resistance R of the battery to be tested (ohmic resistance) ohm The unit is mΩ; when I0≠0, 1.5·|I0|≤|I app |≤5·|I0|;

[0027] Preferably, when acquiring the voltage of the battery under test, the applied test current I app The following conditions must be met:

[0028] When I0 = 0, (5A·mΩ / R) ohm )≤|I app |≤(25A·mΩ / R ohm When I0 ≠ 0, 2·|I0| ≤ |I app |≤5·|I0|.

[0029] In step two, a test current I is applied. app Total time t n The value range is 25-60s, t s The value range is 2-5s. More preferably, when tested in a low-temperature environment with a temperature ≤10℃, t s The value range is 3-5s.

[0030] The step of extracting target data from the voltage and time data set in step two according to a preset second rule includes:

[0031] From the first set of collected voltages Extract As the first target voltage data, it constitutes the first target voltage set. The corresponding first target time set Subscript x0 = 0, x0 < x1 < ... < x m ≤p; from U test (t≤t s The interval parameter for extracting the first target voltage data is α, and its value range is I. app *0.0003V / AI app *0.0012V / A, where V and A represent voltage and current, respectively. The extracted first target voltage data must meet the following requirements:

[0032] and and

[0033] and

[0034] From the second set of collected voltages extract As the second target voltage data, it constitutes the second target voltage set. The corresponding second target time set is Subscript q≤x (m+1) <x (m+2) <...<x M ≤n; from U test (t>t s The interval parameter for extracting the second target voltage data is β, and its value range is I. app *0.001V / AI app *0.005V / A, the extracted second target voltage data must meet the following requirements:

[0035] and

[0036] and ...and so on;

[0037] Target voltage set U filter Equal to the first target voltage set U filter (t≤t s ) and the second target voltage set U filter (t>t s The union of ) is, i.e.

[0038]

[0039] The corresponding target time set

[0040] If the density of the differential or difference curve data points of the target internal resistance R relative to the target logarithmic conversion frequency is greater than the preset density threshold, is too dense and has a preset dense jump point phenomenon on the negative half axis, such as an abnormal dense jump point phenomenon, then the values ​​of a and / or b are increased within the preset specified range until the preset dense jump point phenomenon disappears.

[0041] If the sparsity of the differential or difference curve of the target internal resistance R relative to the target logarithmic conversion frequency reaches a predetermined sparsity threshold, and is too sparsy to predict the maximum value, then the values ​​of a and / or b are reduced within a preset range until the maximum value can be observed on the negative half-axis.

[0042] In step five, an internal resistance meter is used to test the ohmic internal resistance R of the battery. ohm .

[0043] The method for analyzing the internal resistance of a battery according to this invention effectively identifies the boundary points (i.e., the endpoint of electrochemical polarization and the starting point of concentration polarization) where electrochemical polarization and concentration polarization play their roles in the frequency domain by constructing a series of differential or difference curves of small-current DC internal resistance relative to the logarithmic conversion frequency at different test times. This allows for the evaluation of the resistance values ​​of electrochemical activation internal resistance and concentration polarization internal resistance. Furthermore, compared to conventional DCIR testing which uses a larger current pulse rate that may potentially damage the battery, the method applies a smaller rate of charging or discharging test current than the conventional DCIR pulse current, thus causing no damage to the battery.

[0044] The data acquisition process of this invention does not require the use of an electrochemical workstation, and the data acquisition process can be embedded into the battery charge and discharge test process, making the test relatively convenient and flexible. It is particularly feasible for internal resistance analysis with requirements such as test temperature and environment. Attached Figure Description

[0045] Figure 1 This is a flowchart of a method for analyzing the internal resistance of a battery according to an embodiment of the present invention.

[0046] Figure 2 This is the differential curve of the target internal resistance relative to the target logarithmic conversion frequency of the battery in Embodiment 1 of the present invention after 100 cycles at 10°C and 30% SOC. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0048] The method for analyzing the internal resistance of a battery according to the present invention involves placing the battery in a preset temperature environment during analysis, such as below zero or above zero, testing at room temperature or low temperature, such as testing in a low temperature environment of ≤10°C or testing in a high temperature environment.

[0049] The battery under test can be in a static state or in a state of extremely low current charging / discharging. When in a static state, the static time should be no less than 1 hour; when in a state of extremely low current charging / discharging, the charging / discharging time should be no less than 2 minutes. The default charging current is positive, and the discharging current is negative. The unit of current is ampere (A). The current I0 of the battery under test ranges from 0 to 0.1C.

[0050] The present invention will now be illustrated by taking the battery test and voltage data collection as an example when the battery is in a static state.

[0051] Example 1:

[0052] A pouch cell battery with a capacity of 5.4 Ah (1C = 5.4A) has lithium cobalt oxide as the positive electrode and graphite as the negative electrode. After 100 cycles at 10°C using a specific charge-discharge cycle, the internal resistance of this pouch cell battery at 30% SOC (state of charge) in a 10°C environment was analyzed. The procedure is as follows:

[0053] Step 1: The battery to be tested is kept at 10℃ for 1 hour.

[0054] Step 2: The voltage U0 = 3.811975956V is collected instantaneously before the test current is applied, corresponding to the time t0 = 0; the test charging / discharging current I is applied. app =0.1C=0.54A, the total time t for applying the test current. n =60s; all data acquisition times are t0, t1, t2, ..., t n This constitutes the collection time set t test ={t0,t1,t2,…,t n}; The sampling voltage corresponding to each of the above sampling times is U0, U1, U2, ..., U n This constitutes the voltage collection set U test ={U0,U1,U2,…,U n}

[0055] The voltage data acquisition rules (preset first rule) followed in performing the above voltage data acquisition include:

[0056] When the duration of the applied test current is t≤3s, at least one voltage data point should be collected if the time change is ≥0.03s or the voltage change is ≥0.005V; when t>3s, at least one voltage data point should be collected if the time change is ≥1s or the voltage change is ≥0.01V.

[0057] The first voltage data U1 acquired after applying current is 3.831163645V, and the corresponding acquisition time t1 should be 0.0034s, satisfying the additional condition t1∈[0.002s,0.008s].

[0058] Step 3: Extract target data from the voltage and time data set in Step 2 according to the preset second rule, and construct the target voltage set U. filter and target time set t filter .

[0059] The preset data extraction rules are described as follows:

[0060] From the first set of collected voltages Extract As the first target voltage data, it constitutes the first target voltage set. The corresponding first target time set Subscript x0 = 0, x0 < x1 < ... < x m ≤p; from U test The interval parameter for extracting the first target voltage data within the time interval (t≤3s) is α=0.0005V, and the extracted first target voltage data must satisfy:

[0061] and and

[0062] and

[0063] From the second set of collected voltages extract As the second target voltage data, it constitutes the second target voltage set. The corresponding second target time set is Subscript q≤x (m+1) <x (m+2) <...<x M ≤n; from U test The interval parameter for extracting the second target voltage data in (t>3s) is β=0.0014V, and the extracted second target voltage data must satisfy:

[0064] and

[0065] and ...and so on;

[0066] Target voltage set U filter Equal to the first target voltage set U filter (t≤3s) and the second target voltage set U filter The union of (t>3s), i.e.

[0067]

[0068] The corresponding target time set

[0069] Step 4: Based on the target time set t filter and target voltage set U filter Construct the target logarithmic transformation frequency set f filter and the target internal resistance set R filter ; Target time set tfilter Target voltage set U filter Target logarithmic transformation frequency set f filter and the target internal resistance set R filter The elements are in a one-to-one correspondence; plot the differential curve of the target's internal resistance relative to the target's logarithmic transformation frequency (e.g., Figure 2 Find the x-coordinate f of the differential curve when it reaches its maximum value in the interval where the logarithmic transformation frequency is ≤0.1Hz. c f c It is the boundary point where electrochemical reaction polarization and concentration polarization exert their effects in the frequency domain. In this embodiment, f c The corresponding target internal resistance R is -0.530Hz. c， It is the sum of ohmic internal resistance and electrochemical activation internal resistance.

[0070] In step four, the target logarithmic transformation frequency set f filter any element f in x The calculation method is as follows: For any target time t x ∈t filter The corresponding target logarithmic transformation frequency f x =log(0.25 / t) x ).

[0071] In step four, the target internal resistance set R filter Any element R in x The calculation method is as follows: For any target time t x ∈t filter The corresponding voltage is U x The corresponding target internal resistance is R. x =(U x -U0) / (I app -I0), in this embodiment I0=0, the above formula simplifies to R x =(U x -U0) / I app Then R c =(U c -U0) / I app =68.2mΩ.

[0072] The logarithmic transformation frequency boundary point f in step four c , which is usually a negative number.

[0073] Step 5: Calculate the electrochemical activation resistance, concentration resistance, membrane diffusion resistance, and charge transfer resistance.

[0074] The ohmic internal resistance R of the battery under test ohm =25.4mΩ, electrochemical activation internal resistance R act =R c-R ohm = 42.8mΩ, concentration internal resistance R diff =R sum -R c = 12.5mΩ. Membrane diffusion internal resistance R f =R1-R ohm =10.1mΩ, internal resistance of charge transfer R ct =R c -R1=32.6mΩ.

[0075] In step five, R1 = (U1 - U0) / (I app -I0)=35.5mΩ.

[0076] In step five, R sum Applying a test current I to the battery in step two app The DC internal resistance corresponding to the action of 25s, i.e., the sampling time t = 25s, and the sampling voltage U sum =3.855602503V, R sum =(U sum -U0) / (I app -I0)=80.7mΩ.

[0077] It is understandable that the membrane diffusion resistance and charge transfer resistance together constitute the electrochemical activation resistance, therefore R act =R f +R ct .

[0078] The ohmic internal resistance of a battery is tested using an internal resistance meter. It should be noted that battery charge / discharge testing equipment generally cannot achieve microsecond-level data acquisition accuracy. Strictly speaking, the instantaneous voltage drop obtained by battery charge / discharge testing equipment is contributed by both the ohmic internal resistance and a portion of the electrochemical activation internal resistance; ohmic internal resistance can only be measured under at least a 1000Hz AC signal. Therefore, using an internal resistance meter or similar equipment to obtain a relatively accurate ohmic internal resistance value for the battery is crucial.

[0079] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and therefore all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

[0080] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for analyzing the composition of battery internal resistance, characterized in that, Including the following steps: Step 1: Place the battery under test in a preset state at a preset temperature environment; in the preset state, the current of the battery under test is I0, and the value of current I0 is in the range of 0-0.1C; Step 2: Collect the applied test current I of the battery according to the preset first rule. app The instant before and the applied test current I app The voltage during the period forms a set of data acquisition time t. test ={t0, t1, t2, …, t n The corresponding set of collected voltages U test ={U0,U1, U2, …, U n }, t0=0, U0 is the voltage sampled instantaneously before the test current is applied; Step 3: Extract target data from the voltage and time data set in Step 2 according to the preset second rule, and construct the target voltage set U. filter and target time set t filter ; Step 4: Based on the target time set t filter and target voltage set U filter Construct the target logarithmic transformation frequency set f filter and the target internal resistance set R filter ; Target time set t filter Target voltage set U filter Target logarithmic transformation frequency set f filter and the target internal resistance set R filter The elements are in a one-to-one correspondence; plot the differential curve of the target internal resistance relative to the target logarithmic transformation frequency, and mark the x-coordinate of the differential curve when it reaches its maximum value in the range of logarithmic transformation frequency ≤ 0.1Hz. c f c It is the boundary point where electrochemical reaction polarization and concentration polarization exert their effects in the frequency domain, f c The corresponding target internal resistance is R c ; For any target time t x ∈t filter The corresponding target logarithmic transformation frequency set f filter The target logarithmic transformation frequency element f x =log(C / t x C is the conversion factor, with a value ranging from 0.25 to 0.50; For any target time t x ∈t filter The corresponding target internal resistance set R filter The target internal resistance R in x =(U x -U0) / (I app -I0), U x It is any target time t x The corresponding voltage; Step 5: Calculate the electrochemical activation internal resistance R act Concentration resistance R diff And estimate the membrane diffusion resistance R f and charge transfer internal resistance R ct Electrochemical activation internal resistance R act =R c -R ohm Concentration resistance R diff =R sum -R c Membrane diffusion internal resistance R f =R1-R ohm internal resistance of charge transfer R ct =R c -R1, R ohm The internal resistance of the battery to be tested is in ohms. R1=(U1-U0) / (I app -I0); R sum Applying a test current I to the battery in step two app The DC internal resistance corresponding to the action time of 25s, i.e., the sampling time t=25s, U sum R is the corresponding sampling voltage. sum =(U sum -U0) / (I app -I0); In step two, the test current I applied to the battery is collected according to the preset first rule. app The instant before and the applied test current I app The voltage steps during the process include: Used to calculate the electrochemical activation internal resistance R act Concentration resistance R diff When a test current I is applied app The duration of action t≤t s When the time change is ≥0.03s or the voltage change is ≥0.005V, at least one voltage data point should be collected; when t>t s At least one voltage data point must be collected when the time change is ≥1s or the voltage change is ≥0.01V. Used to calculate the internal resistance of membrane diffusion R f and charge transfer internal resistance R ct In addition to satisfying the above conditions for calculating the electrochemical activation internal resistance R, act Concentration resistance R diff In addition to the rules for acquiring voltage data at the time, the application of test current I must also be satisfied. app The acquisition time t1 ∈ [0.002s, 0.008s] corresponds to the first voltage data U1 acquired later; The steps for extracting target data from the voltage and time data set in step two according to a preset second rule include: From the first set of collected voltages U test (t≤t s )= Extract As the first target voltage data, it constitutes the first target voltage set U. filter (t≤t s )= The corresponding first target time set t filter (t≤t s )= Subscript x0=0, x0<x1<…<x m ≤p; from U test (t≤t s The interval parameter for extracting the first target voltage data is α, and its value range is I. app 0.0003V / AI app 0.0012V / A, where V and A represent voltage and current, respectively. The extracted first target voltage data must meet the following requirements: , and , and , …, and ; From the second set of collected voltages U test (t>t s )= extract As the second target voltage data, it constitutes the second target voltage set U. filter (t>t s )= The corresponding second target time set is t. filter (t>t s )= Subscript q≤x (m+1) <x (m+2) <...<x M ≤n; from U test (t>t s The interval parameter for extracting the second target voltage data is β, and its value range is I. app 0.001V / AI app The extracted second target voltage data must meet the following requirements: 0.005V / A and , and ... and so on; Target voltage set U filter Equal to the first target voltage set U filter (t≤t s ) and the second target voltage set U filter (t>t s The union of ) is, i.e. U filter = = ， The corresponding target time set t filter = .

2. The method for analyzing the internal resistance of a battery according to claim 1, characterized in that, In step one, the preset state includes the battery under test being in a static state or in a state of extremely low current charging / discharging. When in a static state, the static time shall not be less than 1 hour; when in a state of extremely low current charging / discharging, the charging / discharging time shall not be less than 2 minutes.

3. The method for analyzing the internal resistance of a battery according to claim 1, characterized in that, If t1 does not satisfy t1∈[0.002s, 0.008s], then adjust it in any of the following ways to make t1 satisfy it: Adjust the test current I app Until t1 is satisfied; Set when the test current I is applied app The duration of action t ≤ 0.01s, and the change in time ≥ t d At least one voltage data point should be collected, t d ∈[0.002s, 0.008s].

4. The method for analyzing the internal resistance of a battery according to claim 1, characterized in that, In step two, when acquiring the voltage of the battery under test, the applied test current I... app The following conditions must be met: When I0=0, (5A·m / R ohm )≤|I app |≤(50A·m / R ohm The internal resistance R of the battery to be tested (ohmic resistance) ohm The unit is m When I0 ≠ 0, 1.5 · |I0| ≤ |I app |≤5·|I0|;When I0=0, (5A·m / R ohm )≤|I app |≤(25A·m / R ohm When I0 ≠ 0, 2·|I0| ≤ |I app |≤5·|I0|.

5. The method for analyzing the internal resistance of a battery according to claim 1, characterized in that, In step one, a test current I is applied. app Total time t n The value range is 25-60s, t s The value range is 2-5s.

6. The method for analyzing the internal resistance of a battery according to claim 1, characterized in that, If the density of the differential curve data points of the target internal resistance relative to the target logarithmic conversion frequency is greater than the preset density threshold and there is a preset dense jump point phenomenon on the negative half axis, then increase the values ​​of a and / or b within the preset specified range until the preset dense jump point phenomenon disappears. If the sparsity of the differential curve of the target internal resistance relative to the target logarithmic conversion frequency reaches a predetermined sparsity threshold, making it impossible to predict the maximum value, then the values ​​of a and / or b are reduced within a preset range until the maximum value can be observed on the negative half-axis.

7. The method for analyzing the internal resistance of a battery according to claim 1, characterized in that, In step five, an internal resistance meter is used to test the ohmic internal resistance R of the battery. ohm .

Images