CN115184823A - Method for detecting consistency of secondary battery - Google Patents
Method for detecting consistency of secondary battery Download PDFInfo
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- CN115184823A CN115184823A CN202210909875.8A CN202210909875A CN115184823A CN 115184823 A CN115184823 A CN 115184823A CN 202210909875 A CN202210909875 A CN 202210909875A CN 115184823 A CN115184823 A CN 115184823A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/385—Arrangements for measuring battery or accumulator variables
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/389—Measuring internal impedance, internal conductance or related variables
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a consistency detection method of a secondary battery, which comprises the following steps: providing a battery to be tested and a plurality of reference batteries; acquiring a Nyquist map of each reference battery; acquiring a first characteristic frequency in a Nyquist map of each reference battery, wherein the first characteristic frequency is a frequency corresponding to the ohm internal resistance of the reference battery in the Nyquist map; acquiring a first average characteristic frequency according to the first characteristic frequency of each reference battery; inputting a first test current with a first average characteristic frequency into a battery to be tested to obtain a corresponding first response voltage; and acquiring the ohmic internal resistance of the battery to be tested according to the first response voltage and the first test current of the first average characteristic frequency, and judging the consistency of the battery to be tested according to the ohmic internal resistance of the battery to be tested. The consistency detection method provided by the invention can efficiently and accurately detect the consistency of the secondary battery.
Description
Technical Field
The invention relates to the technical field of secondary battery performance testing, in particular to a consistency detection method of a secondary battery.
Background
With the increasingly prominent problems of energy crisis, environmental pollution and the like, the development of sustainable new energy and the construction of a low-carbon-cost society become more and more important. The new energy automobile is widely accepted and paid attention to the significance of relieving the energy crisis and protecting the environment. The large-scale commercial popularization of the electric automobile puts high requirements on the service life and the safety performance of the power battery cell and the module Pack. The ohmic internal resistance parameter is one of important marks reflecting the power characteristics and the internal electrochemical state of the power battery cell, and is also an important data basis for evaluating the power characteristics, capacity attenuation and service life attenuation of a battery system in the management of a power battery BMS system.
At present, battery manufacturers mainly detect the consistency of batteries through ohmic internal resistance, and the methods for measuring the ohmic internal resistance mainly comprise three methods: (1) Charging (or discharging) the battery at a constant pulse current to measure a change in voltage, and calculating direct current internal resistance (DCR) as ohmic internal resistance of the battery using ohm's law R = U/I; (2) Applying a small-amplitude alternating current sinusoidal signal with a wide frequency range (from a micro-hertz level to a megahertz level) to the battery, and converting the output current and potential signals by using a spectrum analyzer to obtain impedance, modulus of the impedance and a phase angle under different frequencies so as to analyze different electrochemical reaction processes of the battery system and obtain ohmic internal resistance of the battery; (3) The battery is input with fixed 1KHz sine wave frequency, and a series of data such as voltage, rectification and filtering are collected through an effective conversion circuit, so that the actual impedance value under the characteristic frequency of 1KHz is accurately measured to replace the ohmic internal resistance of the battery.
In the prior art (1), the pulse current is large, and the battery to be tested may cause irreversible damage to the battery after passing through the large pulse current, and has certain safety risk; the larger pulse current can cause the polarization of the battery, and the real ohmic internal resistance is difficult to reflect as a result; the test process requires charging the battery under test to a specific state of charge (SOC), increasing the test time. In the prior art (2), an effective value of an alternating current signal needs to be converted into a voltage value, and the test frequency ranges from a micro-hertz level to a megahertz level, so that the production cost of test equipment is increased, the test period is long, and the direct application to mass production battery test is not feasible. (3) The actual impedance value under the characteristic frequency of 1KHz comprises ohmic internal resistance, electrochemical reaction impedance and inductive reactance, and cannot reflect the real ohmic internal resistance of the battery.
In conclusion, the prior art is difficult to efficiently and accurately detect the consistency of the secondary batteries.
Disclosure of Invention
Therefore, the technical problem to be solved by the present invention is to overcome the defect that it is difficult to efficiently and accurately detect the consistency of the secondary battery in the prior art, thereby providing a method for detecting the consistency of the secondary battery.
The invention provides a consistency detection method of a secondary battery, which comprises the following steps: providing a battery to be tested and a plurality of reference batteries; acquiring a Nyquist map of each reference battery; acquiring a first characteristic frequency in a Nyquist map of each reference battery, wherein the first characteristic frequency is a frequency corresponding to the ohm internal resistance of the reference battery in the Nyquist map; acquiring a first average characteristic frequency according to the first characteristic frequency of each reference battery; inputting a first test current with a first average characteristic frequency into a battery to be tested to obtain a corresponding first response voltage; acquiring the ohmic internal resistance of the battery to be tested according to the first response voltage and the first test current of the first average characteristic frequency; and/or acquiring a second characteristic frequency in the Nyquist map of each reference battery, wherein the second characteristic frequency is a frequency corresponding to the electrochemical reaction resistance of the reference battery in the Nyquist map; acquiring a second average characteristic frequency according to the second characteristic frequency of each reference battery; inputting a first test current with a second average characteristic frequency into the battery to be tested to obtain a corresponding second response voltage; acquiring the electrochemical reaction resistance of the battery to be tested according to the second response voltage and the first test current of the second average characteristic frequency; and judging the consistency of the battery to be tested according to the ohmic internal resistance of the battery to be tested and/or the electrochemical reaction internal resistance of the battery to be tested.
Optionally, the number of the batteries to be tested is several; acquiring the average ohmic internal resistance of a plurality of batteries to be tested according to the ohmic internal resistances of the plurality of batteries to be tested; if the absolute value of the difference value between the ohmic internal resistance of the battery to be tested and the average ohmic internal resistance of the battery to be tested is greater than or equal to the average ohmic internal resistance of the battery to be tested which is multiplied by the first threshold value, the battery to be tested does not accord with the consistency requirement of the battery to be tested; if the absolute value of the difference value between the ohmic internal resistance of the battery to be tested and the average ohmic internal resistance of the battery to be tested is smaller than the average ohmic internal resistance of the battery to be tested which is multiple of the first threshold value, the battery to be tested accords with the consistency requirement of the battery to be tested; the first threshold multiple is less than or equal to 0.005.
Optionally, the first threshold multiple is 0.003.
Optionally, the number of the batteries to be tested is several; obtaining the average electrochemical reaction resistance of a plurality of batteries to be tested according to the electrochemical reaction resistance of the plurality of batteries to be tested; if the absolute value of the difference value between the electrochemical reaction resistance of the battery to be tested and the average electrochemical reaction resistance of the battery to be tested is greater than or equal to the average electrochemical reaction resistance of the battery to be tested which is multiplied by the second threshold value, the battery to be tested does not accord with the consistency requirement of the battery to be tested; if the absolute value of the difference value between the electrochemical reaction resistance of the battery to be detected and the average electrochemical reaction resistance of the battery to be detected is smaller than the average electrochemical reaction resistance of the battery to be detected, which is multiplied by a second threshold value, the battery to be detected meets the requirement of battery consistency; the second threshold multiple is less than or equal to 0.005.
Optionally, the second threshold multiple is 0.003.
Optionally, the ohmic internal resistance of each reference battery is obtained, and the average ohmic internal resistance of the reference battery and the standard deviation of the ohmic internal resistance of the reference battery are obtained according to the ohmic internal resistance of each reference battery; if the absolute value of the difference value between the ohmic internal resistance of the test battery and the average ohmic internal resistance of the reference battery is greater than or equal to the ohmic internal resistance standard difference of the reference battery of the third threshold multiple, the battery to be tested does not meet the consistency requirement of the test battery; if the absolute value of the difference value between the ohmic internal resistance of the test battery and the average ohmic internal resistance of the reference battery is smaller than the ohmic internal resistance standard difference of the reference battery of the multiple of the third threshold value, the battery to be tested meets the consistency requirement of the test battery; the third threshold multiple is less than or equal to 5.
Optionally, the third threshold multiple is 3.
Optionally, the electrochemical reaction resistance of each reference cell is obtained, and the average electrochemical reaction resistance of the reference cell and the standard deviation of the electrochemical reaction resistance of the reference cell are obtained according to the electrochemical reaction resistance of each reference cell; if the absolute value of the difference value between the electrochemical reaction resistance of the test battery and the average electrochemical reaction resistance of the reference battery is greater than or equal to the electrochemical reaction resistance of the reference battery of the fourth threshold multiple, the battery to be tested does not meet the consistency requirement of the test battery; if the absolute value of the difference value between the electrochemical reaction resistance of the test battery and the average electrochemical reaction resistance of the reference battery is smaller than the standard deviation of the electrochemical reaction resistance of the reference battery multiplied by a third threshold value, the battery to be tested meets the requirement of the consistency of the test battery; the fourth threshold multiple is less than or equal to 5.
Optionally, the fourth threshold multiple is 3.
Optionally, the method for obtaining a nyquist map of any reference battery includes: inputting a first test current signal to a reference battery, and acquiring a first response voltage signal of the reference battery corresponding to the first test current signal with different frequencies in a test frequency range; acquiring the internal resistance of the reference battery according to the first response voltage signal and the corresponding first test electric signal of the reference battery under different frequencies; acquiring a Nyquist map of the reference battery according to the internal resistance and the corresponding frequency of the reference battery; the test frequency range is 10 KHz-0.1 Hz.
Optionally, the method further includes: before acquiring the Nyquist map of each reference battery, performing standing treatment on each reference battery; the standing treatment time is 2-10 h; the environmental temperature of the standing treatment is-30 ℃ to 60 ℃.
Optionally, the ambient temperature of the reference battery in the process of obtaining the nyquist diagram of each reference battery is consistent with the ambient temperature of the standing treatment.
Optionally, after the reference batteries are subjected to standing processing and before nyquist maps of the reference batteries are obtained, the reference batteries are charged to a reference state of charge; the reference state of charge is 20-80%.
Optionally, before acquiring the first characteristic frequency and/or the second characteristic frequency, the method further includes: standing the battery to be tested; after the battery to be tested is subjected to standing treatment, the battery to be tested is charged to a reference charge state; the time condition for standing the battery to be tested is the same as the time condition for standing each reference battery; the environmental temperature for the standing treatment of the battery to be measured is the same as the environmental temperature for the standing treatment of each reference battery.
The technical scheme of the invention has the following advantages:
according to the consistency detection method for the secondary batteries, provided by the technical scheme of the invention, in the process of acquiring the Nyquist map of each reference battery, the reference batteries are less damaged, and the more obvious battery polarization of the reference batteries cannot be caused. When the first average characteristic frequency obtained according to the Nyquist diagram of the reference battery is used as the frequency of the first test current of the test battery, the ohmic internal resistance of the test battery can be accurately obtained, and other interference impedance contained in the ohmic internal resistance of the test battery is less. When the second characteristic frequency obtained according to the Nyquist spectrum of the reference battery is used as the frequency of the first test current of the test battery, the electrochemical reaction resistance of the test battery can be accurately obtained, and other interference impedance contained in the electrochemical reaction resistance of the test battery is less. The real ohmic internal resistance and/or the electrochemical reaction resistance of the battery to be tested can be accurately reflected respectively, so that the consistency screening result of the battery to be tested is accurate. In conclusion, the consistency detection method of the secondary battery provided by the invention can efficiently and accurately detect the consistency of the secondary battery.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a flowchart of a method for detecting the consistency of a secondary battery provided in embodiment 1 of the present invention;
FIG. 2 is an equivalent circuit diagram of the electrochemical impedance principle in example 1 of the present invention;
FIG. 3 is a histogram of internal resistance detection results of 30 times of ohm of a battery to be tested with an internal resistance of 0.3382mΩ in example 2 of the present invention;
fig. 4 is a graph of the relationship between the cracking number of different tabs and the ohmic internal resistance in example 2 of the present invention;
FIG. 5 is a graph showing the distribution of the ohmic internal resistance of the cell to be tested of example 3 of the present invention and the internal resistance of the cell to be tested of comparative example 1;
FIG. 6 is a graph showing the relationship between the average ohmic internal resistance of the reference cell and the temperature according to test example 1 of the present invention;
FIG. 7 is a graph of the average electrochemical reaction resistance versus frequency versus temperature for a baseline cell in test example 1 of the present invention;
FIG. 8 is a graph showing the relationship between the average ohmic internal resistance and the temperature of a reference cell in test example 1 of the present invention;
fig. 9 is a distribution diagram of ohmic resistance of the battery to be tested according to test example 2 of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Furthermore, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1
The present embodiment provides a method for detecting the consistency of a secondary battery, which, with reference to fig. 1, includes:
s1, providing a battery to be tested and a plurality of reference batteries;
s2, acquiring a Nyquist map of each reference battery;
s3, acquiring first characteristic frequency in a Nyquist map of each reference battery, wherein the first characteristic frequency is the frequency corresponding to the ohm internal resistance of the reference battery in the Nyquist map; acquiring a first average characteristic frequency according to the first characteristic frequency of each reference battery; inputting a first test current with a first average characteristic frequency into a battery to be tested to obtain a corresponding first response voltage; acquiring the ohmic internal resistance of the battery to be tested according to the first response voltage and the first test current of the first average characteristic frequency; and/or the presence of a gas in the gas,
s4, acquiring second characteristic frequency in the Nyquist map of each reference battery, wherein the second characteristic frequency is the frequency corresponding to the electrochemical reaction resistance of the reference battery in the Nyquist map; acquiring a second average characteristic frequency according to the second characteristic frequency of each reference battery; inputting a first test current with a second average characteristic frequency into a battery to be tested to obtain a corresponding second response voltage; acquiring the electrochemical reaction resistance of the battery to be tested according to the second response voltage and the first test current of the second average characteristic frequency;
and S5, judging the consistency of the battery to be detected according to the ohmic internal resistance of the battery to be detected and/or the electrochemical reaction internal resistance of the battery to be detected.
In the method for detecting the consistency of the secondary battery provided by the embodiment, in the process of acquiring the nyquist map of each reference battery, the damage to the reference battery is small, and the battery polarization of the reference battery is not obvious. When the first average characteristic frequency obtained according to the Nyquist diagram of the reference battery is used as the frequency of the first test current of the test battery, the ohmic internal resistance of the test battery can be accurately obtained, and other interference impedance contained in the ohmic internal resistance of the test battery is less. When the second average characteristic frequency obtained according to the Nyquist diagram of the reference battery is used as the frequency of the first test current of the test battery, the electrochemical reaction resistance of the test battery can be accurately obtained, and other interference impedance contained in the electrochemical reaction resistance of the test battery is less. The real ohmic internal resistance and/or the electrochemical reaction resistance of the battery to be tested can be accurately reflected respectively, so that the consistency screening result of the battery to be tested is accurate. In conclusion, the consistency detection method of the secondary battery provided by the invention can efficiently and accurately detect the consistency of the secondary battery.
In this embodiment, the method for obtaining the nyquist map of any reference cell includes: inputting a first test current signal to a reference battery, and acquiring a first response voltage signal of the reference battery corresponding to the first test current signal with different frequencies in a test frequency range; acquiring the internal resistance of the reference battery according to the first response voltage signal and the corresponding first test electric signal of the reference battery under different frequencies; and acquiring a Nyquist map of the reference battery according to the internal resistance and the corresponding frequency of the reference battery.
In this embodiment, the method for obtaining the frequency corresponding to the ohmic internal resistance in the nyquist plot (i.e., the first characteristic frequency) of each reference battery is to decompose the nyquist plot of the reference battery based on the electrochemical impedance principle (as shown in fig. 2, where L1 represents the inductive resistance of the battery, R1 represents the ohmic internal resistance of the battery, R2 represents the electrochemical reaction impedance of the battery, C2 represents the capacitance of the battery, and W3 represents the diffusion impedance of the battery) to obtain the frequency corresponding to the ohmic internal resistance, which is the frequency point corresponding to the intersection of the nyquist plot curve and the nyquist real part plot, and the resistance value of the intersection is the ohmic internal resistance of the reference battery.
In this embodiment, the method for obtaining the corresponding frequency of the electrochemical reaction resistance in the nyquist diagram (i.e., the second characteristic frequency) of each reference cell is to decompose the nyquist diagram of the reference cell based on the electrochemical impedance principle equivalent circuit diagram (as shown in fig. 2) to obtain the corresponding frequency of the electrochemical reaction resistance, which is the corresponding frequency at the first approximate semicircular inflection point of the nyquist diagram curve, and the impedance corresponding to the real part of the inflection point is the electrochemical reaction resistance of the reference cell.
In this embodiment, the test frequency range is 10KHz to 0.1Hz, such as 10KHz to 0.1Hz, or 1000Hz to 0.1Hz.
In this embodiment, the method for detecting the uniformity of a secondary battery further includes: before acquiring the nyquist map of each reference cell, performing standing treatment on each reference cell, wherein the standing treatment time is 2-10 h, for example: 3h, 4h, 8h or 10h; the environmental temperature of the standing treatment is-30 ℃ to 60 ℃, for example: -20 ℃,0 ℃,10 ℃, 30 ℃ or 45 ℃. The standard battery is subjected to standing treatment, so that the performance of the test battery is relatively stable, and the adverse effect of non-uniform temperature of the test battery on the test result is avoided. The standing treatment time is more determined by the size of the battery and the original temperature. The temperature of the standing treatment is determined by the reference battery use temperature.
In this embodiment, the ambient temperature of the reference battery and the temperature of the standing treatment are the same in the process of acquiring the nyquist diagram of each reference battery.
In the embodiment, after the standing processing is performed on each reference battery and before the nyquist map of each reference battery is obtained, the reference battery is charged to the reference state of charge; the reference state of charge is 20% to 80%, for example: 20%, 30%, 50% or 75%. In order to achieve accurate testing, the reference battery needs to be debugged to have the same state of charge, so as to avoid different battery polarizations generated by different states of charge, which makes the contrast of the detection result poor.
In this embodiment, before acquiring the first characteristic frequency and/or the second characteristic frequency, the method further includes: standing the battery to be tested; after the battery to be tested is subjected to standing treatment, the battery to be tested is charged to a reference charge state; the time condition for standing the battery to be tested is the same as the time condition for standing each reference battery; the environmental temperature for the standing treatment of the battery to be measured is the same as the environmental temperature for the standing treatment of each reference battery.
In one embodiment, the number of the batteries to be tested is several; acquiring the average ohmic internal resistance of a plurality of batteries to be tested according to the ohmic internal resistances of the plurality of batteries to be tested; if the absolute value of the difference value between the ohmic internal resistance of the battery to be tested and the average ohmic internal resistance of the battery to be tested is larger than or equal to the average ohmic internal resistance of the battery to be tested, which is multiplied by the first threshold value, the battery to be tested does not accord with the consistency requirement of the battery to be tested; if the absolute value of the difference value between the ohmic internal resistance of the battery to be tested and the average ohmic internal resistance of the battery to be tested is smaller than the average ohmic internal resistance of the battery to be tested which is multiple of the first threshold value, the battery to be tested accords with the consistency requirement of the battery to be tested; the first threshold multiple is less than or equal to 0.05, such as 0.05,0.01,0.005, or 0.003; in this embodiment, the first threshold multiple is 0.003.
In another embodiment, the number of the batteries to be tested is several; obtaining the average electrochemical reaction resistance of a plurality of batteries to be tested according to the electrochemical reaction resistance of the plurality of batteries to be tested; if the absolute value of the difference value between the electrochemical reaction resistance of the battery to be tested and the average electrochemical reaction resistance of the battery to be tested is greater than or equal to the average electrochemical reaction resistance of the battery to be tested which is multiplied by the second threshold value, the battery to be tested does not accord with the consistency requirement of the battery to be tested; if the absolute value of the difference value between the electrochemical reaction resistance of the battery to be detected and the average electrochemical reaction resistance of the battery to be detected is smaller than the average electrochemical reaction resistance of the battery to be detected, which is multiplied by a second threshold value, the battery to be detected meets the requirement of battery consistency; the second threshold multiple is less than or equal to 0.05, such as 0.05,0.01,0.005, or 0.003; in this embodiment, the second threshold multiple is 0.003.
In another embodiment, the ohmic internal resistance of each reference battery is obtained, and the average ohmic internal resistance of the reference battery and the standard deviation of the ohmic internal resistance of the reference battery are obtained according to the ohmic internal resistance of each reference battery; if the absolute value of the difference value between the ohmic internal resistance of the test battery and the average ohmic internal resistance of the reference battery is greater than or equal to the ohmic internal resistance standard difference of the reference battery of the third threshold multiple, the battery to be tested does not meet the consistency requirement of the test battery; if the absolute value of the difference value between the ohmic internal resistance of the test battery and the average ohmic internal resistance of the reference battery is smaller than the ohmic internal resistance standard difference of the reference battery of the multiple of the third threshold value, the battery to be tested meets the consistency requirement of the test battery; the third threshold multiple is less than or equal to 5, such as 1, 2, 3, or 5; in this embodiment, the third threshold multiple is 3.
In another embodiment, the electrochemical reaction resistance of each reference cell is obtained, and the average electrochemical reaction resistance of the reference cell and the standard deviation of the electrochemical reaction resistance of the reference cell are obtained according to the electrochemical reaction resistance of each reference cell; if the absolute value of the difference value between the electrochemical reaction resistance of the test battery and the average electrochemical reaction resistance of the reference battery is greater than or equal to the electrochemical reaction resistance of the reference battery which is multiplied by the fourth threshold value, the battery to be tested does not meet the consistency requirement of the test battery; if the absolute value of the difference value between the electrochemical reaction resistance of the test battery and the average electrochemical reaction resistance of the reference battery is smaller than the electrochemical reaction resistance standard deviation of the reference battery of the multiple of the third threshold value, the battery to be tested meets the consistency requirement of the test battery; the fourth threshold multiple is less than or equal to 5, such as 1, 2, 3, or 5; in this embodiment, the fourth threshold multiple is 3.
Example 2
Providing 10 pure electric square batteries with good states and the same model as a reference battery, standing the reference battery at 25 ℃ for 6 hours, adjusting the charge state of the reference battery to 50% of the charge state, inputting a first test current signal to a test reference battery through a BT4560 type frequency conversion daily internal resistance instrument at 25 ℃ to obtain first response voltage signals of the reference battery corresponding to the first test current signals with different frequencies within the frequency range of 1000 Hz-0.1 Hz (wherein, one point is collected at every 1Hz within the frequency range of 1000 Hz-10 Hz, and one point is collected at every 0.1Hz within the frequency range of 10 Hz-0.1 Hz), and obtaining the internal resistance of the reference battery according to the first response voltage signals and the corresponding first test electric signals of the reference battery under different frequencies; and acquiring a Nyquist map of the reference battery according to the internal resistance and the corresponding frequency of the reference battery.
Acquiring the corresponding frequency of the ohmic internal resistance of each reference battery and the ohmic internal resistance based on an electrochemical impedance principle equivalent circuit diagram model (refer to fig. 2) of the reference battery and a nyquist diagram of the reference battery, averagely calculating to acquire the corresponding frequency of the average ohmic internal resistance of the reference battery to be 66Hz, averagely calculating to acquire the average ohmic internal resistance of the reference battery to be 0.3061m omega, calculating to acquire the standard deviation of the ohmic internal resistance of the reference battery to be 0.001m omega, and taking the third threshold multiple to be 3.
The method comprises the steps of providing 10 batteries to be tested (2 of which are good batteries, 2 of which are two-layer batteries, 2 of which are four-layer batteries, 2 of which are six-layer batteries and 2 of which the tabs are cracked, and eight-layer batteries) which are the same as a reference battery in type but have different tab cracking degrees, standing the batteries to be tested at 25 ℃ for 6 hours, adjusting the charge state of the batteries to be tested to be 50% of the charge state, inputting a first test current signal of 66Hz to the batteries to be tested through a BT4560 type frequency conversion daily internal resistance instrument at 25 ℃, obtaining corresponding first response voltage, and obtaining the ohmic internal resistance of the batteries to be tested according to the first response voltage and the first test current of the first characteristic frequency.
The ohmic internal resistance value of the battery to be tested is sequentially as follows according to the increasing sequence (0 layer, 2 layers, 4 layers, 6 layers and 8 layers) of the cracking layer number of the lug: 0.3052m omega, 0.3051m omega, 0.3187m omega, 0.3183m omega, 0.3262m omega, 0.3264m omega, 0.3315m omega, 0.3317m omega, 0.3382m omega and 0.3387m omega, and comparison shows that the internal ohmic resistance values of the tested batteries can be divided into 5 groups, and the batteries respectively correspond to good batteries in a good state, two-layer batteries with cracked lugs, four-layer batteries with cracked lugs, six-layer batteries with cracked lugs and eight-layer batteries with cracked lugs. The comparison of the difference value between the ohmic internal resistance value of the battery to be tested and the average ohmic internal resistance value of the reference battery and the standard deviation of the ohmic internal resistances shows that when the cracking number of the lug is 2 layers, the battery does not meet the requirement of testing the consistency of the battery.
The method comprises the steps of detecting a battery to be tested with the ohmic internal resistance of 0.3382m omega for 30 times through a BT4560 type frequency conversion daily internal resistance instrument test (the test conditions are the same as the test conditions), and obtaining that the ohmic internal resistance of the battery to be tested accords with normal distribution through a Minitab software frequency and ohmic internal resistance histogram (shown in figure 3), and the diagram 3 shows that the standard deviation value is small, so that the measurement system has small fluctuation, high sensitivity and low test error.
And (3) testing each battery to be tested 10 times respectively by using a BT4560 type frequency conversion daily internal resistance tester (the testing conditions are the same as the testing conditions), recording the corresponding ohmic internal resistance, and drawing a relation graph of the tab cracking number and the ohmic internal resistance by using Minitab software (as shown in figure 4). As can be seen from fig. 4, as the number of cracked layers of the tab increases, the ohmic internal resistance basically has a linear increasing relationship, and the increasing rate of the ohmic internal resistance can reach about 10% at most, which indicates that under the condition of small ohmic internal resistance difference, the method can accurately and effectively identify the ohmic internal resistance, thereby improving the identifying precision of the ohmic internal resistance, effectively solving the problem of screening the consistency of the ohmic internal resistance of the battery, and improving the product yield.
Example 3
Providing 10 square batteries with good states for hybrid electric vehicles of the same model as a reference battery, standing the reference battery at 25 ℃ for 6 hours, adjusting the charge state of the reference battery to 50% of the charge state, inputting a first test current signal to a test reference battery through an electrochemical workstation at 25 ℃ to obtain first response voltage signals of the reference battery corresponding to first test current signals with different frequencies within the frequency range of 10 kHz-10 mHz, and obtaining the internal resistance of the reference battery according to the first response voltage signals of the reference battery at different frequencies and the corresponding first test electrical signals; and acquiring a Nyquist map of the reference battery according to the internal resistance and the corresponding frequency of the reference battery.
Acquiring the corresponding frequency of the ohmic internal resistance of each reference battery based on an electrochemical impedance principle equivalent circuit diagram model (refer to fig. 2) of the reference battery and a nyquist diagram of the reference battery, and averagely calculating to acquire the corresponding frequency of the average ohmic internal resistance of the reference battery to be 245Hz.
Providing 100 to-be-tested batteries (the to-be-tested batteries are numbered from 1 to 100) with the same model as the reference battery, standing the to-be-tested batteries for 6 hours at 25 ℃, adjusting the charge state of the to-be-tested batteries to 50% charge state, inputting a 245Hz first test current signal to the to-be-tested batteries through a production line variable frequency internal resistance instrument at 25 ℃, obtaining corresponding first response voltage, obtaining ohmic internal resistance of each to-be-tested battery according to the first response voltage and the first test current with first characteristic frequency, averagely calculating the average ohmic internal resistance of the to-be-tested batteries, comparing the ohmic internal resistance of each to-be-tested battery with the average ohmic internal resistance, and if the absolute value of the difference value of the ohmic internal resistance of the to-be-tested battery and the average ohmic internal resistance is greater than or equal to 0.3% of the average ohmic internal resistance, determining that the to-be-tested batteries do not accord with the consistency of the to-tested batteries; and if the absolute value of the difference value of the ohmic internal resistance of the battery to be tested and the average ohmic internal resistance is less than 0.3 percent of the average ohmic internal resistance, the battery to be tested accords with the consistency of the battery to be tested. The test results refer to fig. 5.
Screening out 2 batteries to be tested which do not accord with the consistency of the batteries.
Comparative example 1
Detecting 100 batteries in embodiment 3, standing the battery to be tested at 25 ℃ for 6 hours, adjusting the charge state of the battery to be tested to 50% of the charge state, inputting a 1000Hz first test current signal to the battery to be tested through a production line internal resistance instrument at 25 ℃, obtaining a corresponding first response voltage, obtaining the ohmic internal resistance of each battery to be tested according to the first response voltage and the first test current of the first characteristic frequency, averagely calculating the average ohmic internal resistance of the ohmic internal resistances of the batteries to be tested, comparing the ohmic internal resistance of each battery to be tested with the average ohmic internal resistance, and if the absolute value of the difference between the ohmic internal resistance of the battery to be tested and the average ohmic internal resistance is greater than or equal to 0.3% of the average ohmic internal resistance, determining that the battery to be tested does not conform to the consistency of the battery to be tested; and if the absolute value of the difference value between the ohmic internal resistance and the average ohmic internal resistance of the battery to be tested is less than 0.3 percent of the average ohmic internal resistance, the battery to be tested accords with the consistency of the battery to be tested. The test results refer to fig. 5.
And screening 4 batteries to be tested which do not accord with the consistency of the batteries.
Because the internal resistance obtained under the first test current signal of 1000Hz contains a large amount of inductive reactance, the internal resistance has larger fluctuation, and the battery to be tested which accords with the battery consistency is easy to sieve.
Test example 1
After 10 reference batteries in embodiment 3 are allowed to stand at 25 ℃ for 6 hours, the state of charge of the reference batteries is adjusted to 50% state of charge, a first test current signal is input to a test reference battery through an electrochemical workstation at 25 ℃ to obtain first response voltage signals of the reference batteries corresponding to first test current signals with different frequencies within a frequency range of 10 kHz-10 mHz, and the internal resistance of the reference batteries is obtained according to the first response voltage signals and the corresponding first test electrical signals of the reference batteries with different frequencies; and acquiring a Nyquist map of the reference battery according to the internal resistance and the corresponding frequency of the reference battery.
Acquiring ohmic internal resistance corresponding frequency and ohmic internal resistance of each reference battery and electrochemical reaction resistance corresponding frequency based on an electrochemical impedance principle equivalent circuit diagram model (refer to fig. 2) of the reference battery and a Nyquist diagram of the reference battery, and averagely calculating to acquire average ohmic internal resistance corresponding frequency, average ohmic internal resistance and average electrochemical reaction resistance corresponding frequency of the reference battery.
According to the method, the average ohmic internal resistance corresponding frequency, the average ohmic internal resistance and the average electrochemical reaction resistance corresponding frequency of the 10 reference batteries at-30 ℃, 25 ℃, 20 ℃,10 ℃,0 ℃,10 ℃ and 25 ℃ are obtained in sequence.
The average ohmic resistance versus frequency versus temperature is shown in fig. 6, and the average electrochemical reaction resistance versus frequency versus temperature is shown in fig. 7.
The relationship between the average ohmic internal resistance and the temperature is shown in fig. 8, and as can be seen from fig. 8, the relationship between the average ohmic internal resistance and the temperature conforms to the arrhenius equation:
σT＝Ae -Ea/RT
where σ represents the ion mobility rate, σ = L/(R × S); t represents temperature, ea represents activation energy; k is a constant; a is a pre-factor, L represents the length of the electrode material, and S represents the area of the electrode material; r represents resistance (ohmic internal resistance or electrochemical reaction resistance).
Through fig. 8, it can be illustrated that the test value of the average ohmic internal resistance is relatively accurate within a relatively wide temperature range, and the method for detecting the consistency of the secondary battery provided by the invention can efficiently and accurately detect the consistency of the secondary battery within a relatively wide temperature range.
Test example 2
Providing 10 square batteries with good states and the same model for a hybrid electric vehicle as a reference battery, standing the reference battery at 25 ℃ for 6 hours, adjusting the charge state of the reference battery to 50% of the charge state, inputting a first test current signal to a test reference battery through a BT4560 type frequency conversion daily internal resistance instrument at 25 ℃ to obtain first response voltage signals of the reference battery corresponding to the first test current signals with different frequencies within the frequency range of 1000Hz to 0.1Hz (wherein, one point is collected at every 1Hz within the frequency range of 1000Hz to 10Hz, and one point is collected at every 0.1Hz within the frequency range of 10Hz to 0.1 Hz), and obtaining the internal resistance of the reference battery according to the first response voltage signals of the reference battery under different frequencies and the corresponding first test electric signals; and acquiring a Nyquist map of the reference battery according to the internal resistance and the corresponding frequency of the reference battery.
Acquiring the corresponding frequency of the ohmic internal resistance of each reference battery and the ohmic internal resistance based on an electrochemical impedance principle equivalent circuit diagram model (refer to fig. 2) of the reference battery and a Nyquist diagram of the reference battery, and averagely calculating to acquire the corresponding frequency of the average ohmic internal resistance of the reference battery, wherein the corresponding frequency of the average ohmic internal resistance is 300Hz.
Randomly providing 9 batteries to be tested with the same model (carrying out battery numbering), standing the batteries to be tested at 25 ℃ for 6 hours, adjusting the charge state of the batteries to be tested to 50% charge state, inputting a first test current signal of 300Hz to the batteries to be tested through a BT4560 type frequency conversion daily internal resistance meter at 25 ℃ to obtain corresponding first response voltage, and obtaining the ohmic internal resistance of the batteries to be tested according to the first response voltage and the first test current of the first characteristic frequency. The test results are shown in FIG. 9.
The ohmic internal resistance of the batteries in the same type and volume production can be visually seen to have certain difference through the graph 9, and the ohmic internal resistance of the batteries can be accurately and effectively identified, so that the volume production batteries which do not accord with the consistency requirement of the batteries can be screened out, and the yield of good products is improved.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications derived therefrom are intended to be within the scope of the invention.
Claims (10)
1. A method for detecting the consistency of a secondary battery, comprising:
providing a battery to be tested and a plurality of reference batteries;
acquiring a Nyquist map of each reference battery;
acquiring a first characteristic frequency in a Nyquist map of each reference battery, wherein the first characteristic frequency is a frequency corresponding to the ohm internal resistance of the reference battery in the Nyquist map;
acquiring a first average characteristic frequency according to the first characteristic frequency of each reference battery;
inputting a first test current with a first average characteristic frequency into a battery to be tested to obtain a corresponding first response voltage;
acquiring the ohmic internal resistance of the battery to be tested according to the first response voltage and the first test current of the first average characteristic frequency; and/or the presence of a gas in the atmosphere,
acquiring a second characteristic frequency in the Nyquist map of each reference battery, wherein the second characteristic frequency is a frequency corresponding to the electrochemical reaction resistance of the reference battery in the Nyquist map; acquiring a second average characteristic frequency according to the second characteristic frequency of each reference battery; inputting a first test current with a second average characteristic frequency into the battery to be tested to obtain a corresponding second response voltage; acquiring the electrochemical reaction resistance of the battery to be tested according to the second response voltage and the first test current of the second average characteristic frequency;
and judging the consistency of the battery to be tested according to the ohmic internal resistance of the battery to be tested and/or the electrochemical reaction internal resistance of the battery to be tested.
2. The method according to claim 1, wherein the number of the batteries to be tested is several; acquiring the average ohmic internal resistance of a plurality of batteries to be tested according to the ohmic internal resistances of the plurality of batteries to be tested; if the absolute value of the difference value between the ohmic internal resistance of the battery to be tested and the average ohmic internal resistance of the battery to be tested is more than or equal to the average ohmic internal resistance of the battery to be tested, the battery to be tested does not accord with the consistency requirement of the battery to be tested; if the absolute value of the difference value between the ohmic internal resistance of the battery to be tested and the average ohmic internal resistance of the battery to be tested is smaller than the average ohmic internal resistance of the battery to be tested, which is multiplied by the first threshold value, the battery to be tested meets the requirement of consistency of the battery to be tested; the first threshold multiple is less than or equal to 0.05.
3. The method according to claim 1, wherein the number of the batteries to be tested is several; obtaining the average electrochemical reaction resistance of a plurality of batteries to be tested according to the electrochemical reaction resistance of the plurality of batteries to be tested; if the absolute value of the difference value between the electrochemical reaction resistance of the battery to be tested and the average electrochemical reaction resistance of the battery to be tested is greater than or equal to the average electrochemical reaction resistance of the battery to be tested which is multiple of the second threshold, the battery to be tested does not accord with the consistency requirement of the battery to be tested; if the absolute value of the difference value between the electrochemical reaction resistance of the battery to be detected and the average electrochemical reaction resistance of the battery to be detected is smaller than the average electrochemical reaction resistance of the battery to be detected, which is multiplied by a second threshold value, the battery to be detected meets the requirement of battery consistency; the second threshold multiple is less than or equal to 0.05.
4. The method according to claim 1, wherein the ohmic internal resistances of the reference cells are obtained, and the average ohmic internal resistance of the reference cells and the standard deviation of the ohmic internal resistances of the reference cells are obtained based on the ohmic internal resistances of the reference cells; if the absolute value of the difference value between the ohmic internal resistance of the test battery and the average ohmic internal resistance of the reference battery is greater than or equal to the ohmic internal resistance standard difference of the reference battery of the multiple of the third threshold, the battery to be tested does not meet the consistency requirement of the test battery; if the absolute value of the difference value between the ohmic internal resistance of the test battery and the average ohmic internal resistance of the reference battery is smaller than the ohmic internal resistance standard difference of the reference battery of the third threshold multiple, the battery to be tested meets the consistency requirement of the test battery; the third threshold multiple is less than or equal to 5.
5. The method according to claim 1, wherein the electrochemical reaction resistance of each reference cell is obtained, and the average electrochemical reaction resistance of the reference cell and the standard deviation of the electrochemical reaction resistance of the reference cell are obtained from the electrochemical reaction resistance of each reference cell; if the absolute value of the difference value between the electrochemical reaction resistance of the test battery and the average electrochemical reaction resistance of the reference battery is greater than or equal to the electrochemical reaction resistance of the reference battery of the fourth threshold multiple, the battery to be tested does not meet the consistency requirement of the test battery; if the absolute value of the difference value between the electrochemical reaction resistance of the test battery and the average electrochemical reaction resistance of the reference battery is smaller than the standard deviation of the electrochemical reaction resistance of the reference battery multiplied by a third threshold value, the battery to be tested meets the requirement of the consistency of the test battery; the fourth threshold multiple is less than or equal to 5.
6. The method of detecting the uniformity of a secondary battery according to claim 1, wherein the method of obtaining a nyquist map of a reference battery comprises: inputting a first test current signal to a reference battery, and acquiring a first response voltage signal of the reference battery corresponding to the first test current signal with different frequencies in a test frequency range; acquiring the internal resistance of the reference battery according to the first response voltage signal and the corresponding first test electric signal of the reference battery under different frequencies; acquiring a Nyquist map of the reference battery according to the internal resistance and the corresponding frequency of the reference battery; the test frequency range is 10 KHz-0.1 Hz.
7. The method for detecting the consistency of a secondary battery according to claim 1, characterized by further comprising: before acquiring the Nyquist map of each reference battery, performing standing treatment on each reference battery; the standing treatment time is 2-10 h; the environmental temperature of the standing treatment is-30 ℃ to 60 ℃.
8. The method according to claim 7, wherein the ambient temperature of the reference battery in the step of obtaining the nyquist map of each reference battery is matched with the ambient temperature of the standing treatment.
9. The method according to claim 7, wherein the reference cells are charged to a reference state of charge after the standing process of each reference cell and before the nyquist plot of each reference cell is obtained; the reference state of charge is 20-80%.
10. The method for detecting the consistency of the secondary battery according to claim 9, further comprising, before acquiring the first characteristic frequency and/or the second characteristic frequency: standing the battery to be tested; after the battery to be tested is subjected to standing treatment, the battery to be tested is charged to a reference charge state; the time condition for carrying out standing treatment on the battery to be detected is the same as the time condition for carrying out standing treatment on each reference battery; the environmental temperature for the standing treatment of the battery to be measured is the same as the environmental temperature for the standing treatment of each reference battery.
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| CN116774679A (en) * | 2023-08-25 | 2023-09-19 | 北京斯年智驾科技有限公司 | Automatic driving vehicle testing method, system, device and storage medium |
| CN116774679B (en) * | 2023-08-25 | 2023-11-28 | 北京斯年智驾科技有限公司 | Automatic driving vehicle testing method, system, device and storage medium |
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