CN111751741B - Nondestructive testing method for lithium ion battery lithium analysis threshold voltage - Google Patents
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- G—PHYSICS
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- 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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- 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]
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Abstract
The invention discloses a nondestructive testing method for lithium ion battery lithium analysis threshold voltage, which comprises the following steps: step one, charging a battery at a constant current by using a normal charging current I with a preset magnitude, and immediately entering a charging stopping sleep stage at intervals of a fixed time or a fixed voltage value at intervals until the battery is charged to a set cut-off voltage; secondly, drawing to obtain a first resistance-voltage curve; thirdly, performing constant current charging on batteries of the same type at a small current I' with a preset magnitude, and drawing to obtain a second resistance-voltage curve; fourthly, comparing the second resistance-voltage curve serving as a reference curve with the first resistance-voltage curve; the threshold voltage at which lithium deposition begins to occur when the battery is charged with a constant current at a current I is read. The invention determines the threshold voltage of lithium analysis of the battery in the charging process by intermittently measuring the direct current resistance of the battery in the charging process of the battery and analyzing the resistance-voltage curve.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a nondestructive testing method for lithium analysis threshold voltage of a lithium ion battery.
Background
At present, lithium ion batteries have the advantages of high specific energy, many recycling times, long storage time and the like, and are widely applied to portable electronic equipment such as mobile phones, digital cameras and portable computers, and also widely applied to large and medium-sized electric equipment such as electric automobiles, electric bicycles, electric tools and the like, so that the performance requirements on the lithium ion batteries are higher and higher.
In the current commercialized lithium ion battery, graphite is still a commonly used lithium ion battery cathode material, and because the lithium intercalation potential of the graphite is close to that of metallic lithium, under certain use conditions, such as large-current charging or low-temperature charging, a lithium precipitation phenomenon easily occurs, so that the cycle performance of the lithium ion battery is seriously affected, and even safety problems such as short circuit in the battery and the like may be caused by formation of lithium dendrite.
At present, a common lithium precipitation detection method is generally to determine whether metallic lithium exists on the surface of a negative plate by manually observing the presence of metallic lithium according to experience in a mode of disassembling a battery. Although this method is relatively straightforward, it is a post-determination method and cannot detect the threshold voltage parameter when lithium deposition in the battery begins.
It should be noted that the threshold means a limit, so the threshold is also called a critical value, and means the lowest value or the highest value that an effect can produce. In this patent, the threshold voltage at which lithium deposition in the battery starts is represented by: the lowest voltage corresponding to the time when the battery begins to generate lithium deposition in the charging process, namely, the time when the voltage is exceeded, the battery begins to continuously generate lithium deposition, so that the threshold voltage of the battery for generating lithium deposition is called, namely, the critical voltage of the battery for generating lithium deposition.
The threshold voltage of lithium precipitation is detected under different temperatures and different charging currents of the battery, so that the time when the battery begins to precipitate lithium under the conditions can be determined, and the charging cut-off voltage under the corresponding charging current is limited to be below the threshold voltage, so that the good performance and the use safety of the battery are ensured. Particularly, under the requirement of the current market end on improving the quick charging capacity of the battery, research and development personnel can effectively avoid lithium separation of the battery in the use process by referring to parameters such as lithium separation threshold voltage and the like while shortening the charging time as much as possible when developing a quick charging system. Once the battery generates lithium precipitation, the battery is easy to generate side reaction with electrolyte due to the high activity of the precipitated lithium, and the generated side reaction product is deposited on the surface of a negative electrode, so that the impedance of the battery is increased, and the performance of the battery is influenced; when the lithium precipitation amount of the battery is increased, lithium continuously grows on the surface of a negative electrode, and the formed lithium dendrite easily pierces a diaphragm to cause internal short circuit of the battery, even the battery has safety accidents such as thermal runaway and the like.
As the battery is used, its performance will degrade and the original charging regime will likely no longer be suitable. Therefore, in the following specific technical solution of the present invention, the present invention provides a method for detecting a lithium analysis threshold voltage, which can be applied to detection in a full life cycle of a battery, and appropriately adjust a charging system according to a periodic detection result of the lithium analysis threshold voltage of the battery, which is helpful for prolonging the service life of the battery and ensuring safety.
Disclosure of Invention
The invention aims to provide a nondestructive testing method for lithium ion battery lithium analysis threshold voltage aiming at the technical defects in the prior art.
Therefore, the invention provides a nondestructive testing method for lithium ion battery lithium analysis threshold voltage, which comprises the following steps:
step one, performing constant current charging on a battery by using a normal charging current I with a preset magnitude, and immediately entering a charging stopping dormancy stage at intervals of a fixed time or a fixed voltage value in the constant current charging process until the battery is charged to a set cut-off voltage;
wherein, in each sleep stage of stopping charging, the initial voltage V of the battery when the charging is just stopped is collected in real time s And after the preset time length of dormancy, collecting the end voltage V of the battery at the end of dormancy in real time r Then, according to a preset calculation formula, calculating and obtaining the initial direct current resistance R when the battery is charged with the constant current of the normal charging current I and the charging is just stopped at each charging stopping dormancy stage s (ii) a Namely, intermittently measuring to obtain the direct current resistance of the battery;
secondly, using the initial voltage V of the battery in each sleep stage of stopping charging s, As abscissa, with the corresponding measured initial DC resistance R of the battery at each rest period s Drawing a resistance-voltage curve of the battery in the constant current charging process by using the normal charging current I as a vertical coordinate, and defining the curve as a first resistance-voltage curve;
the third step is to preThe method comprises the steps that a small current I' with a set magnitude is used for carrying out constant current charging on batteries with the same type, and in the constant current charging process, a charging stopping sleep stage is immediately started at intervals of a fixed time or a fixed magnitude of voltage value at intervals until the batteries are charged to a set cut-off voltage; then, the initial voltage V of the battery in each charging stop sleep stage is used s ' is abscissa, to correspond to the measured initial DC resistance R of the battery at each rest period s The resistance-voltage curve is drawn and obtained in the process that the battery is charged at constant current by small current I', and the resistance-voltage curve is defined as a second resistance-voltage curve;
wherein, in each sleep stage of stopping charging, the initial voltage V of the battery when the charging is just stopped is collected in real time s ' and after the preset time length of dormancy, collecting the end voltage V of the battery at the end of dormancy in real time r 'then according to the preset calculation formula, calculating and obtaining the initial direct current resistance R when the battery is charged with a constant current at a small current I', and the charging is stopped at the beginning of each charging stopping sleep stage s '; namely, the direct current resistance of the battery is obtained by intermittent measurement;
fourthly, taking the second resistance-voltage curve as a reference curve, and comparing the reference curve with the first resistance-voltage curve; when the first resistance-voltage curve has the inflection point of the 1 st direct current resistance value decrease with the trend different from that of the reference curve in the process of voltage increase, the battery begins to precipitate lithium, and the corresponding battery voltage V in the first resistance-voltage curve at the moment is read s,L I.e. the threshold voltage at which lithium precipitation begins to occur when the battery is subjected to constant current charging at the normal charging current I.
In the first step, a preset calculation formula is as follows:
starting DC resistance R when the battery is charged with a constant current of a normal charging current I and just starts to stop charging in each sleep stage of stopping charging s ＝(V s -V r )/I；
In the third step, the preset calculation formula is as follows:
when the battery is charged with a constant current of small current I', at each timeInitial DC resistance R when charging is stopped just after a sleep stage of stopping charging s ’＝(V s ’-V r ’)/I’。
In the first step and the third step, a charging stop sleep stage is immediately entered at regular intervals, wherein:
for a fixed time interval, the time length T of the fixed time is calculated as follows:
length of time T ═ Q/I 0 3600 a%, in milliseconds;
wherein Q is the battery capacity, I 0 Is the magnitude of the charging current; the value range of A% is 0.02% -5%;
in a first step, the magnitude of the charging current I 0 Equal to the normal charging current I; in a third step, the magnitude of the charging current I 0 Equal to the small current I'.
In the first step and the third step, a charging stop sleep stage is immediately entered at intervals of a fixed voltage value, wherein:
the voltage value with fixed magnitude is set to be 1mV-100 mV;
in the first step and the third step, the dormancy lasts for a preset time, specifically 0.01-50 s.
Wherein, the set value range of the voltage value with fixed magnitude is 5mV-50 mV;
in the first step and the third step, the preset dormancy time is 0.1s-10 s.
Wherein, the value range of the small current I' is 0.01C-0.5C.
Wherein, the value range of the small current I' is 0.05C-0.3C.
Compared with the prior art, the nondestructive testing method for lithium ion battery lithium analysis threshold voltage provided by the invention has great practical significance by measuring the direct current resistance of the battery intermittently in the battery charging process and analyzing the resistance-voltage curve to determine the lithium analysis threshold voltage of the battery in the charging process.
Drawings
FIG. 1 is a flow chart of a nondestructive testing method for lithium ion battery lithium analysis threshold voltage according to the present invention;
FIG. 2 is a schematic diagram of the DC impedance test in example 1 of the improved nondestructive testing method for lithium-ion battery lithium-analyzing threshold voltage of the present invention;
FIG. 3 is a schematic diagram of a resistance-voltage curve of a lithium ion battery in example 1 during constant current charging with 1C current according to an improved nondestructive testing method for lithium ion battery lithium analysis threshold voltage of the present invention;
FIG. 4 is a schematic diagram of a resistance-voltage reference curve of a lithium ion battery with a 0.2C current constant current charging process in example 1 according to an improved nondestructive testing method for lithium ion battery lithium separation threshold voltage of the present invention;
FIG. 5 is a schematic diagram of a resistance-voltage curve of a lithium ion battery in example 2 during constant current charging with a current of 0.7C according to an improved nondestructive testing method for lithium ion battery lithium analysis threshold voltage of the present invention;
fig. 6 is a schematic diagram of a resistance-voltage reference curve of a lithium ion battery in the constant current charging process of the battery at 0.2C according to the nondestructive testing method for lithium analysis threshold voltage of the lithium ion battery provided by the present invention in example 2.
Detailed Description
In order that those skilled in the art will better understand the technical solution of the present invention, the following detailed description of the present invention is provided in conjunction with the accompanying drawings and embodiments.
Referring to fig. 1 to 6, the invention provides a nondestructive testing method for lithium ion battery lithium deposition threshold voltage, which specifically comprises the following steps:
step one, performing constant current charging on a battery by using a normal charging current I with a preset magnitude, and immediately entering a charging stopping sleep stage in the constant current charging process at intervals of a fixed time or a fixed voltage value at intervals until the battery is charged to a set cut-off voltage;
wherein, in each sleep stage of stopping charging, the initial voltage of the battery when the charging is just stopped is collected in real timeV s (the voltage of the battery is charged for a certain time or voltage value at constant current with a preset current I), and after the battery is in dormancy for a preset time, the end voltage V of the battery at the end of dormancy is collected in real time r (namely the voltage of the battery after the dormancy for the preset time), then according to a preset calculation formula, calculating and obtaining the initial direct current resistance R when the battery is charged with the constant current of the normal charging current I and the charging is just stopped at each charging stopping dormancy stage s (ii) a Namely, intermittently measuring to obtain the direct current resistance of the battery;
secondly, using the initial voltage V of the battery in each sleep stage of stopping charging s, As an abscissa, the measured initial DC resistance R of the battery in each sleep stage of stopping charging s Drawing a resistance-voltage curve of the battery in the constant current charging process by using the normal charging current I as a vertical coordinate, and defining the curve as a first resistance-voltage curve;
thirdly, constant-current charging is carried out on batteries of the same type (for example, batteries of the same product type in the same batch, namely batteries with the same specification, such as 21700 cylindrical lithium ion batteries, as described below) at a low current I' of a preset magnitude, and in the constant-current charging process, a dormant stage of stopping charging is immediately entered at a fixed time interval or at a fixed voltage interval until the batteries are charged to a set cut-off voltage; then, the initial voltage V of the battery in each stop charging dormant stage is used s ' is abscissa, to correspond to the measured initial DC resistance R of the battery at each rest period s The resistance-voltage curve is drawn and obtained in the process that the battery is charged at constant current by small current I', and the resistance-voltage curve is defined as a second resistance-voltage curve;
wherein, in each sleep stage of stopping charging, the initial voltage V of the battery when the charging is just stopped is collected in real time s ' (voltage when the battery is charged for a certain time or voltage value with a constant current of preset current I) and after the dormancy is carried out for a preset time period, acquiring the end voltage V of the battery when the dormancy is ended in real time r ' (i.e. the voltage of the battery after the preset time period of dormancy), and then according to a preset calculation formula, calculating to obtain the batteryStarting direct current resistance R when the charging is stopped at the beginning of each charging stopping dormancy stage during the low current I' constant current charging s '; namely, the direct current resistance of the battery is obtained by intermittent measurement;
fourthly, taking the second resistance-voltage curve as a reference curve, and comparing the reference curve with the first resistance-voltage curve; when the first resistance-voltage curve has a 1 st inflection point (namely, an inflection point of reduced direct current resistance) of reduced direct current resistance value with a trend different from that of a reference curve in the process of increasing the voltage, the first resistance-voltage curve indicates that the battery begins to generate lithium separation, and the corresponding battery voltage V in the first resistance-voltage curve at the moment is read sL That is, the threshold voltage at which lithium deposition starts to occur when the battery is charged at a normal charging current I, may also be referred to as the maximum threshold voltage at which lithium deposition does not occur when the battery is charged at the normal charging current I.
The first resistance-voltage curve shows a trend different from the reference curve in the process of increasing voltage, for example, the first resistance-voltage curve is an upward trend (direct current resistance is increased), and the reference curve is a downward trend; or the first resistance-voltage curve is falling (DC resistance falling) and the reference curve is rising
In the first step and the third step, in particular implementation, time, voltage, current and capacity data in the battery charging process are collected in real time.
In the first step, in terms of specific implementation, a preset calculation formula is as follows:
starting DC resistance R when the battery is charged with a constant current of a normal charging current I and just starts to stop charging in each sleep stage of stopping charging s ＝(V s -V r )/I。
In the third step, in particular, the preset calculation formula is as follows:
initial DC resistance R when the battery is charged with a constant current of a small current I', just starting to stop charging in each sleep stage of stopping charging s ’＝(V s ’-V r ’)/I’。
For the specific implementation of the invention, the test environment (i.e. working environment) of the first step is the same as the test environment (i.e. working environment) of the third step of constant current charging with a small current I'.
In the third step, specifically, in terms of implementation, the preset small current I' is preferably a charging current at which lithium deposition does not occur in the battery under the evaluation condition, for example, 0.01C to 0.5C at normal temperature (e.g., 5 to 25 ℃), and the intermittent dc resistance test is performed with the small current, and the drawn resistance-voltage curve shape is used as a reference curve.
It should be noted that, for the present invention, the method for detecting a lithium deposition threshold voltage provided by the present invention is a nondestructive detection, and does not need to perform additional processing on the battery, and does not need high-precision testing equipment, so that the method is suitable for detecting lithium deposition threshold voltages of all types of batteries in various working environments, and is suitable for detecting lithium deposition threshold voltages of batteries at various stages of a full life cycle.
In the first step and the third step, in particular, a charging stop sleep stage is immediately entered at a fixed time interval, wherein:
for each interval of a fixed time, the time length T of the fixed time (i.e., the interval time) may be calculated as a charging time required for each charging of the battery by a preset percentage a% of the battery capacity Q (e.g., a charging amount of SOC of 0.02% to 5%); the calculation formula of the time length T is as follows:
length of time T ═ Q/I 0 3600 a%, in milliseconds;
wherein Q is the battery capacity, I 0 Is the magnitude of the charging current; the preferable value range of A% is 0.02% -5%;
in a first step, the magnitude of the charging current I 0 Equal to the normal charging current I; in a third step, the magnitude of the charging current I 0 Equal to the small current I'.
For example, when charging at 1C current, the charging time (i.e., 36 seconds, i.e., 3600 seconds multiplied by 1%) required for charging at 1% SOC (state of charge) is calculated to obtain a time interval of 36s (i.e., equal to the charging time), i.e., the battery is charged at 1C current at constant current, and is put to sleep once every 36s for intermittent test of dc impedance.
In the present invention, in the first step and the third step, a sleep stage for stopping charging is immediately entered at intervals of a fixed voltage value, wherein:
the voltage value (i.e. the interval voltage value) with a fixed magnitude can be set in a range of 1mV-100mV, preferably 5mV-50 mV.
In the first step and the third step, specifically, in terms of implementation, the preset sleeping time is 0.01-50 s, and preferably 0.1-10 s.
In the fourth step, the method obtains the threshold voltage of the lithium deposition of the battery by comparing and analyzing the shape of a first resistance-voltage curve obtained when the constant current charging is carried out on the normal charging current I and a reference curve (namely, a second resistance-voltage curve) obtained under the condition of no lithium deposition under low current.
In the third step, the value range of the small current I' is generally 0.01C to 0.5C, preferably 0.05C to 0.3C, depending on different test environments.
In the fourth step, specifically, the method compares the shape of a first resistance-voltage curve obtained when the normal charging current I is subjected to constant current charging with the shape of a reference curve (i.e., a second resistance-voltage curve) obtained under the condition that lithium is not analyzed at a low current, when a first resistance-voltage curve measured by the normal charging current I in the charging process has a 1 st descending inflection point with a trend different from that of the reference curve along with the rise of voltage, the first resistance-voltage curve indicates that lithium analysis of the battery starts, and reads a corresponding battery voltage Vs and L in the first resistance-voltage curve at the moment, namely a threshold voltage at which lithium analysis of the battery starts when the battery is subjected to constant current charging at the normal charging current I, which can also be referred to as a maximum threshold voltage at which lithium analysis does not occur in the battery when the battery is subjected to constant current charging at the normal charging current I.
Based on the technical scheme, the invention provides a nondestructive testing method for lithium analysis threshold voltage of a lithium ion battery, which can determine the threshold voltage of lithium analysis in the battery charging process by measuring the direct current resistance of the battery intermittently in the battery charging process and analyzing a resistance-voltage curve. The method comprises the following specific steps: charging the battery at a constant current by a set current (namely a normal charging current I with a preset magnitude), sleeping for a certain time at intervals of a certain time or voltage, and measuring the direct current resistance under the voltage until the battery is charged to a set cut-off voltage; taking the charging voltage of the battery as an abscissa and the measured direct current resistance as an ordinate, and drawing a first resistance-voltage curve; compared with a reference resistance-voltage curve in a small-current charging process with a preset size, when a first falling inflection point with a trend different from that of the reference curve appears in a measured first resistance-voltage curve, the fact that the lithium analysis of the battery starts is indicated, and the corresponding battery voltage in the first resistance-voltage curve at the moment is read, namely the threshold voltage of the lithium analysis of the battery during the charging under the current.
Therefore, the detection method does not need to carry out additional processing treatment on the battery, belongs to nondestructive detection on the battery, does not need to use high-precision expensive equipment, and is suitable for detecting the lithium analysis threshold voltage of all types of batteries under various working environments and is suitable for detecting the lithium analysis threshold voltage of each stage of the full life cycle of the battery.
In order to more clearly understand the technical solution of the present invention, the following description is given with reference to specific embodiments.
The present invention will be described in detail below with reference to the accompanying drawings by taking the test of a commercial cylindrical lithium ion battery as an example to further illustrate the essential features and significant progress of the present invention.
Example 1.
In this example, the test sample is 21700 cylindrical lithium ion experimental battery, the 1C capacity is 4.62Ah, in this example, whether the battery generates lithium deposition during the constant current charging process with 1C current is tested, and the threshold voltage of the battery generating lithium deposition during the 1C charging is tested.
The battery test equipment is a conventional charge and discharge instrument, and in the embodiment, the equipment is an Arbin BT2000 charge and discharge test system. The method specifically comprises the following testing steps:
the first step is as follows: the normal charging current I with the preset magnitude is 4.62A (namely 1C), the battery is charged with constant current, and the cut-off voltage is 4.2V. Considering that lithium deposition should not occur when the battery is charged in a low state of charge, when a test interval of the dc resistance is set, the 40% SOC previous interval is set to be 3s of rest per 180s of charge, and 3s of rest per 36s of charge from the 40% SOC is set for intermittently measuring the dc resistance of the battery. During charging, time, voltage, current and capacity data during the battery charging process are collected.
The intermittent direct current resistance calculation method comprises the following steps: as shown in FIG. 2, the voltage when the battery is charged with a constant current of 4.62A for a certain time is denoted as V s 3.588V, the battery voltage after dormancy for 3s is V r 3.468V, the battery is charged to V s R as direct current resistance at 3.588V s ＝(V s -V r )/I＝(3.588-3.468)/4.62＝0.0260Ω＝26.0mΩ。
The second step is that: when the constant current charging is carried out by the normal charging current I, the charging voltage V of the battery in each charging stage is used s Is an abscissa and the measured corresponding direct current resistance Rs is an ordinate, and a first resistance-voltage curve of the battery in the process of charging at 1C current is plotted, as shown in fig. 3;
the third step: as shown in fig. 4, the second resistance-voltage curve measured during the charging process with a small current I' of 0.2C is used as a reference curve, and the first resistance-voltage curve measured during the charging process with a normal charging current I of 1C is compared with the reference curve, so that it can be found that the first resistance-voltage curve measured during the charging process with 1C has a falling inflection point around 4.11V, and at this time, the lithium precipitation of the battery starts, i.e. the threshold voltage at which the lithium precipitation of the battery starts when the battery is charged with 1C current is 4.11V, and is also the maximum threshold voltage at which the lithium precipitation does not occur when the battery is charged with 1C current.
It should be noted that the second resistance-voltage curve measured during the charging process for the small current I' of 0.2C is obtained in the same manner as the charging process for the 1C current. The method comprises the following specific steps: the batteries of the same model are subjected to constant current charging at 0.92A, and the batteries are dormant for 3s every 180s of charging, and are dormant for 3s every 36s of charging from 40% SOC, so that the batteries are used for intermittently measuring the direct current resistance of the batteries. During charging, time, voltage, current and capacity data during the battery charging process are collected.
According to R s ’＝(V s ’-V r ')/I ', the charging voltage V of the battery at each stage can be calculated when charging is carried out by calculating small current I ' with the size of 0.2C s ' lower intermittent DC resistance R s ', then at a charging voltage V s 'is plotted on the abscissa and the corresponding measured dc resistance Rs' is plotted on the ordinate to obtain a second resistance-voltage curve (i.e., the reference curve) during charging of the battery at a current of 0.2C, as shown in fig. 4. It was found that during the 0.2C current charging process, the dc resistance of the battery decreased gradually as the battery voltage increased, and then leveled off, and increased slightly by the end of the charge.
It should be noted that the principle of the detection method of the present invention is as follows: when the lithium deposition occurs during the charging of the battery, a lithium deposition layer is formed on the surface of the negative electrode, and a parallel circuit is formed with the original negative electrode plate, so that the current during the charging of the battery is partially shunted, and the battery resistance is reduced. The curve of the direct current impedance along with the change of the charging voltage deviates from the original trend to generate an inflection point of impedance reduction when the lithium is separated from the battery, and the inflection point shows that the lithium separation of the battery is started, so that the threshold voltage of the lithium separation of the battery can be obtained.
Example 2.
In this example, the test sample is a 21700 cylindrical experimental battery cycled 1000 times, the battery capacity has decayed to 4.08Ah, and in this example, it is tested whether the battery will have lithium deposition during the 0.7C current constant current charging process, and the threshold voltage of the battery for lithium deposition during the 0.7C charging process is tested.
The battery testing device is a conventional charge and discharge instrument, and the device adopted in the embodiment is an Arbin BT2000 charge and discharge testing system. The method specifically comprises the following testing steps:
the first step is as follows: the normal charging current I with the preset magnitude is 0.7C-2.856A, the battery is subjected to constant current charging, and the cut-off voltage is 4.2V. The battery was dormant for 3s per 260s of charge, starting from 40% SOC, and for 3s per 52s of charge for intermittent measurement of the dc resistance of the battery. During charging, time, voltage, current and capacity data during the charging process of the battery are collected.
The intermittent DC resistance is calculated as shown in FIG. 2, and the voltage of the battery charged at a constant current of 2.856A for a certain time is recorded as V s The battery voltage after 3s of dormancy is V r Then the battery is charged to V s A direct current resistance of R s ＝(V s -V r )/I。
The second step is that: when the constant current charging is carried out at the normal charging current I of 0.7C, the charging voltage Vs of the battery in each charging stage is taken as an abscissa, and the measured corresponding direct current resistance R s As a ordinate, a resistance-voltage curve of the battery during charging at a current of 0.7C was plotted, as shown in fig. 5;
the third step: when the second resistance-voltage curve measured during the charging process with a small current I' of 0.2C, as shown in fig. 6, is used as a reference curve and the first resistance-voltage curve measured during the charging process with a normal charging current I of 0.7C is compared with the reference curve, it can be found that the first falling inflection point appears on the resistance-voltage curve measured during the charging process with 0.7C at about 3.88V, and the lithium deposition on the battery starts at this time, that is, the threshold voltage at which the lithium deposition on the battery starts when the battery is charged with a current of 0.7C is 3.88V.
It should be noted that the second resistance-voltage curve measured during the charging process for the small current I' of 0.2C is obtained in the same manner as the charging process for the current of 0.7C. The method specifically comprises the following steps: the battery was charged at a constant current of 0.816A, 3s of dormancy for every 180s of charging, 3s of dormancy for every 36s of charging, starting from 40% SOC, for intermittent measurement of the dc resistance of the battery. During charging, time, voltage, current and capacity data during the charging process of the battery are collected.
According to R s ’＝(V s ’-V r ')/I ', calculating small current I ' of 0.2C for charging, charging voltage V of the battery at each stage s ' lower intermittent DC resistance R s ', then at a charging voltage V s 'is the abscissa and the corresponding measured dc resistance Rs' is the ordinate, and a second resistance-voltage curve (i.e., a reference curve) is plotted during charging of the battery at a current of 0.2C, as shown in fig. 6. It can be found that during the charging process with a small current I' of the order of 0.2CThe direct current resistance of the battery after the cyclic attenuation is reduced and then becomes smooth along with the increase of the voltage of the battery, the direct current resistance is obviously increased by the last charging stage, and particularly, the direct current resistance at the last charging stage is greatly increased relative to the non-cyclic battery.
Therefore, based on the technical scheme, the nondestructive detection method for the threshold voltage of lithium ion battery lithium analysis provided by the invention has the advantages that the battery does not need to be additionally processed, only intermittent direct current resistance test is carried out on the battery, and the threshold voltage of the battery lithium analysis can be obtained through trend analysis of a resistance-voltage curve, so that the nondestructive detection method is suitable for detection of lithium analysis threshold voltages of all types of batteries in various working environments, is suitable for detection of lithium analysis threshold voltages of the batteries at various stages of the full life cycle, provides a detection method and a formulation basis for determination of battery use boundary conditions and optimization of charging systems, and has a wide application prospect in management of the health state of the battery.
Of course, those skilled in the art can also calculate other lithium analysis threshold parameters according to other parameters acquired during charging, such as the corresponding charge state during lithium analysis, and the like, all of which are within the protection scope of the present invention.
In summary, compared with the prior art, the nondestructive testing method for lithium ion battery lithium analysis threshold voltage provided by the invention has great practical significance in determining the lithium analysis threshold voltage of the battery in the charging process by intermittently measuring the direct current resistance of the battery in the battery charging process and analyzing the resistance-voltage curve.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.
Claims (7)
1. A nondestructive testing method for lithium ion battery lithium analysis threshold voltage is characterized by comprising the following steps:
step one, performing constant current charging on a battery by using a normal charging current I with a preset magnitude, and immediately entering a charging stopping sleep stage in the constant current charging process at intervals of a fixed time or a fixed voltage value at intervals until the battery is charged to a set cut-off voltage;
wherein, in each sleep stage of stopping charging, the initial voltage V of the battery when the charging is just stopped is collected in real time s And after the preset time length of dormancy, collecting the end voltage V of the battery at the end of dormancy in real time r Then, according to a preset calculation formula, calculating and obtaining the initial direct current resistance R when the battery is charged with the normal charging current I and the charging is stopped at the beginning of each charging stopping dormancy stage s (ii) a Namely, the direct current resistance of the battery is obtained by intermittent measurement;
secondly, using the initial voltage V of the battery in each sleep stage of stopping charging s As an abscissa, the measured initial DC resistance R of the battery in each sleep stage of stopping charging s Drawing a resistance-voltage curve of the battery in the constant current charging process by using the normal charging current I as a vertical coordinate, and defining the curve as a first resistance-voltage curve;
thirdly, constant current charging is carried out on the batteries of the same model by using a small current I' with a preset magnitude, and in the constant current charging process, a charging stopping dormancy stage is immediately started at intervals of a fixed time or a fixed voltage value at intervals until the batteries are charged to a set cut-off voltage; then, the initial voltage V of the battery in each charging stop sleep stage is used s ' is abscissa, to correspond to the measured initial DC resistance R of the battery at each rest period s The resistance-voltage curve is drawn and obtained in the process that the battery is charged at constant current by small current I', and the resistance-voltage curve is defined as a second resistance-voltage curve;
wherein, in each sleep stage of stopping charging, the initial voltage V of the battery when the charging is just stopped is collected in real time s ' and after the preset time length of dormancy, collecting the end voltage V of the battery at the end of dormancy in real time r ', then calculating according to a presetCalculating the initial DC resistance R when the battery is charged with a constant current at a low current I' and just starts to stop charging at each stage of stopping charging and sleeping s '; namely, intermittently measuring to obtain the direct current resistance of the battery;
fourthly, taking the second resistance-voltage curve as a reference curve, and comparing the reference curve with the first resistance-voltage curve; when the first resistance-voltage curve has the inflection point of the 1 st direct current resistance value decrease with the trend different from that of the reference curve in the process of voltage increase, the battery begins to precipitate lithium, and the corresponding battery voltage V in the first resistance-voltage curve at the moment is read s,L I.e. the threshold voltage at which lithium precipitation begins to occur when the battery is subjected to constant current charging at the normal charging current I.
2. The nondestructive testing method according to claim 1, wherein in the first step, the preset calculation formula is as follows:
starting DC resistance R when the battery is charged with a constant current of a normal charging current I and just starts to stop charging in each sleep stage of stopping charging s ＝(V s -V r )/I；
In the third step, the preset calculation formula is as follows:
initial DC resistance R when the battery is charged with a constant current of small current I', just starting to stop charging at each sleep stage of stopping charging s ’＝(V s ’-V r ’)/I’。
3. The nondestructive inspection method according to claim 1, wherein in the first step and the third step, a charge stop sleep phase is entered at regular intervals, wherein:
for a fixed time interval, the time length T of the fixed time is calculated as follows:
length of time T ═ Q/I 0 3600 a%, in milliseconds;
wherein Q is the battery capacity, I 0 Is the magnitude of the charging current; the value range of A% is 0.02% -5%;
in a first step, the magnitude of the charging current I 0 Equal to the normal charging current I; in a third step, the magnitude of the charging current I 0 Equal to the small current I'.
4. The nondestructive inspection method according to claim 1, wherein in the first step and the third step, a charge stop sleep phase is immediately entered every other voltage value of a fixed magnitude, wherein:
the voltage value with fixed magnitude is set to be 1mV-100 mV;
in the first step and the third step, the dormancy lasts for a preset time, specifically 0.01-50 s.
5. The nondestructive testing method of claim 4, wherein the voltage value of the fixed magnitude is set to a value ranging from 5mV to 50 mV;
in the first step and the third step, the preset dormancy time is 0.1s-10 s.
6. A nondestructive testing method according to any one of claims 1 to 5 wherein the small current I' has a value in the range of 0.01C to 0.5C.
7. A non-destructive testing method as defined in claim 6, wherein said small current I' is in the range of 0.05C-0.3C.
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| CN112436202B (en) * | 2020-10-22 | 2021-10-15 | 中车长春轨道客车股份有限公司 | Stepped current charging method for preventing lithium precipitation of lithium ion battery cathode |
| CN112098858B (en) * | 2020-11-09 | 2021-02-19 | 天津力神电池股份有限公司 | Nondestructive analysis method for capacity attenuation of lithium ion battery |
| CN112098866B (en) * | 2020-11-09 | 2021-02-19 | 天津力神电池股份有限公司 | Nondestructive analysis method for judging whether lithium separation occurs in battery circulation process |
| WO2022160212A1 (en) * | 2021-01-28 | 2022-08-04 | 宁德时代新能源科技股份有限公司 | Method and apparatus for detecting anomaly of lithium battery, and battery management system and battery system |
| CN112964994A (en) * | 2021-02-01 | 2021-06-15 | 惠州亿纬锂能股份有限公司 | Method and device for measuring maximum current of battery |
| CN113193249B (en) * | 2021-04-27 | 2023-02-10 | 广州小鹏汽车科技有限公司 | Method and device for determining lithium analysis threshold value and electric automobile |
| CN115298561A (en) * | 2021-10-26 | 2022-11-04 | 东莞新能源科技有限公司 | Electrochemical device lithium analysis detection method and system and electrochemical device |
| CN116762206A (en) * | 2021-10-26 | 2023-09-15 | 东莞新能安科技有限公司 | Electrochemical device management method, electrochemical device management system, electronic equipment and charging device |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013182788A (en) * | 2012-03-01 | 2013-09-12 | Nippon Soken Inc | Lithium ion secondary battery and charge control method therefor |
| CN106099230A (en) * | 2016-08-09 | 2016-11-09 | 清华大学 | A kind of lithium ion battery fast charge method preventing to analyse lithium |
| CN106450536A (en) * | 2016-11-09 | 2017-02-22 | 清华大学 | Quick charging method for lithium ion battery |
| CN108732506A (en) * | 2018-04-26 | 2018-11-02 | 合肥国轩高科动力能源有限公司 | A kind of detection method of lithium-ion-power cell analysis lithium |
| CN108761344A (en) * | 2018-06-06 | 2018-11-06 | 江苏塔菲尔新能源科技股份有限公司 | A kind of detection method and system of lithium ion battery analysis lithium |
| CN108872859A (en) * | 2017-05-16 | 2018-11-23 | 宁德时代新能源科技股份有限公司 | Detection method for battery lithium separation, battery management system and battery system |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4952808B2 (en) * | 2010-02-22 | 2012-06-13 | トヨタ自動車株式会社 | Lithium deposition discrimination device for lithium ion secondary battery, method thereof, and vehicle equipped with the device |
-
2020
- 2020-05-14 CN CN202010408062.1A patent/CN111751741B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013182788A (en) * | 2012-03-01 | 2013-09-12 | Nippon Soken Inc | Lithium ion secondary battery and charge control method therefor |
| CN106099230A (en) * | 2016-08-09 | 2016-11-09 | 清华大学 | A kind of lithium ion battery fast charge method preventing to analyse lithium |
| CN106450536A (en) * | 2016-11-09 | 2017-02-22 | 清华大学 | Quick charging method for lithium ion battery |
| CN108872859A (en) * | 2017-05-16 | 2018-11-23 | 宁德时代新能源科技股份有限公司 | Detection method for battery lithium separation, battery management system and battery system |
| CN108732506A (en) * | 2018-04-26 | 2018-11-02 | 合肥国轩高科动力能源有限公司 | A kind of detection method of lithium-ion-power cell analysis lithium |
| CN108761344A (en) * | 2018-06-06 | 2018-11-06 | 江苏塔菲尔新能源科技股份有限公司 | A kind of detection method and system of lithium ion battery analysis lithium |
Non-Patent Citations (1)
| Title |
|---|
| 电量微分法研究锂离子蓄电池碳负极锂的析出;于洪涛等;《电源技术》;20041120;全文 * |
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