CN115298561A - Electrochemical device lithium analysis detection method and system and electrochemical device - Google Patents

Electrochemical device lithium analysis detection method and system and electrochemical device Download PDF

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CN115298561A
CN115298561A CN202180021655.5A CN202180021655A CN115298561A CN 115298561 A CN115298561 A CN 115298561A CN 202180021655 A CN202180021655 A CN 202180021655A CN 115298561 A CN115298561 A CN 115298561A
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electrochemical device
lithium
soc
curve
intermittent
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甄杰明
揭晓
吉登粤
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Dongguan Amperex Technology Ltd
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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
    • G01R31/387—Determining ampere-hour charge capacity or SoC
    • G01R31/388—Determining ampere-hour charge capacity or SoC involving voltage measurements
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/46—Accumulators structurally combined with charging apparatus
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • 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

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Abstract

An electrochemical device lithium precipitation detection method, a system and an electrochemical device comprise an intermittent charging operation on the electrochemical device, wherein the intermittent charging operation comprises a plurality of charging periods and a plurality of interruption periods, the SOC of the electrochemical device is increased by a unit amplitude in each charging period, the unit amplitude ranges from 2% to 5%, and the duration of the interruption periods ranges from 8 seconds to 10 seconds; maintaining the temperature at a predetermined temperature T1 during the intermittent charging operation; for each of the plurality of intermittent periods, acquiring the SOC and the internal resistance of the electrochemical device for the intermittent period, obtaining a first curve based on the plurality of SOCs of the electrochemical device and the plurality of internal resistances of the electrochemical device corresponding to the plurality of SOCs, and determining the lithium deposition SOC of the electrochemical device based on a first order differential curve of the first curve. The detection sensitivity of the electrochemical device for lithium analysis SOC is improved, and therefore the safety of the electrochemical device in the using process is improved.

Description

Electrochemical device lithium analysis detection method and system and electrochemical device
Technical Field
The application relates to the technical field of electrochemistry, in particular to a lithium analysis detection method and system for an electrochemical device and the electrochemical device.
Background
Lithium ion batteries have many advantages of high specific energy density, long cycle life, high nominal voltage, low self-discharge rate, small volume, light weight, etc., and have wide applications in the consumer electronics field.
With the rapid development of consumer electronics products such as tablet computers and mobile phones in recent years, the market demand for lithium ion batteries is increasing. But lithium ion batteries can generate lithium precipitation due to side reaction, impact and the like in the use process, the battery is easy to be short-circuited to generate safety risk, and the safety of the battery is affected. Therefore, lithium analysis detection is required for the lithium ion battery to find the lithium analysis risk of the lithium ion battery.
Disclosure of Invention
An object of the embodiments of the present application is to provide a method and a system for detecting lithium deposition in an electrochemical device, and an electrochemical device, so as to improve the detection sensitivity of lithium deposition SOC (State of Charge) in the electrochemical device. The specific technical scheme is as follows:
in a first aspect of the present application, there is provided a method for detecting lithium in an electrochemical device, wherein the method comprises the step of detecting lithium in the electrochemical devicePerforming an intermittent charging operation including a plurality of charging periods in each of which the SOC of the electrochemical device is increased by a unit amplitude ranging from 2% to 5% and a plurality of intermittent periods having a duration ranging from 8 seconds to 10 seconds; maintaining the temperature at a predetermined temperature T during intermittent charging operation 1 (ii) a For each of the plurality of intermittent periods, obtaining the SOC and the internal resistance of the electrochemical device for the intermittent period, and obtaining a first curve representing a mapping curve corresponding to the SOC and the internal resistance of the electrochemical device based on the obtained plurality of SOCs and the plurality of internal resistances of the electrochemical device corresponding to the SOCs; and determining a lithium evolution SOC of the electrochemical device based on a first order differential curve of the first curve.
The beneficial effects of the embodiment of the application are as follows: according to the embodiment of the application, the unit amplitude of SOC increase and the time length of the intermittent period in the intermittent charging operation are controlled, the temperature of the electrochemical device in the intermittent charging operation is cooperatively controlled to be kept at the preset temperature, the detection sensitivity of lithium separation SOC of the electrochemical device is improved, and therefore the safety of the electrochemical device in the using process is improved.
In one embodiment of the present application, the step of performing an intermittent charging operation on the electrochemical device includes performing an intermittent charging operation on the electrochemical device at a detection rate of 1.1C to 1.9C. Through cooperative control of the detection rate and the heat preservation temperature, the lithium ion battery can be charged at a proper detection rate in the detection process, and meanwhile, lithium analysis of the lithium ion battery cannot occur too early or too late within the temperature range, so that the detection accuracy of the lithium analysis SOC of the lithium ion battery after circulation is improved.
In one embodiment of the present application, the step of determining the lithium evolution SOC of the electrochemical device based on a first order differential curve of the first curve comprises performing a second order differentiation on the first order differential curve to obtain a second curve; and determining the SOC corresponding to the point where the ordinate of the second curve is less than zero for the first time as the lithium analysis SOC.
In one embodiment of the present application, the method further includes determining a lithium deposition starting voltage of the electrochemical device based on the lithium deposition SOC of the electrochemical device and a pre-established SOC-charging voltage mapping relationship, where the lithium deposition starting voltage is a charging voltage of the electrochemical device when lithium deposition occurs, and determining the lithium deposition starting voltage of the electrochemical device without complex calculation is performed, so that the determination process of the lithium deposition starting voltage of the electrochemical device is simpler.
In one embodiment of the present application, the step of determining the lithium deposition start voltage of the electrochemical device based on the lithium deposition SOC of the electrochemical device and a pre-established SOC-charging voltage mapping relationship comprises obtaining a third curve of the electrochemical device, the third curve representing a mapping curve corresponding to the SOC and the charging voltage of the electrochemical device at the detection rate; and taking the lithium analysis SOC determined under the detection multiplying power as the current SOC, searching the charging voltage corresponding to the current SOC in the third curve as the lithium analysis starting voltage, and determining the lithium analysis starting voltage of the electrochemical device without complex calculation, so that the determination process of the lithium analysis starting voltage of the electrochemical device is simpler and more convenient.
In one embodiment of the present application, the electrochemical device comprises one of a lithium iron phosphate system electrochemical device, a nickel cobalt lithium manganate system electrochemical device, or a lithium cobaltate system electrochemical device, wherein the electrochemical device is a lithium iron phosphate system electrochemical device, the unit amplitude ranges from 2% to 5%, and the duration of the interruption period ranges from 8 seconds to 9 seconds; the electrochemical device is a nickel cobalt lithium manganate system electrochemical device, the unit amplitude range is 2-5%, and the time length range of the interruption period is 8-10 seconds; the electrochemical device is a lithium cobaltate system electrochemical device, the unit amplitude range is 2-3%, the time length range of the interruption period is 9-10 seconds, intermittent charging operation is performed on the electrochemical devices of different systems in a targeted manner, and lithium precipitation SOCs of the electrochemical devices of different systems can be obtained more accurately. The applicant finds that the electrochemical device selects a lithium iron phosphate system or a lithium nickel cobalt manganese oxide system through research, and the detection sensitivity of the lithium separation state is higher by adopting the lithium separation detection method provided by the application.
In one embodiment of the present application, the predetermined temperature T 1 In the range of from 20 ℃ to 30 ℃. The influence due to the rise in the temperature of the lithium ion battery in the intermittent charging operation can be reduced, thereby further increasing the detection temperature of the lithium analysis SOC.
A second aspect of the present application provides a battery system including an intermittent charging device for performing an intermittent charging operation on an electrochemical device, the intermittent charging operation including a plurality of charging periods in which SOC of the electrochemical device is increased by a unit amplitude ranging from 2% to 5% and a plurality of intermittent periods in which a time length ranges from 8 seconds to 10 seconds; maintaining the temperature at a predetermined temperature T during intermittent charging operation 1 (ii) a The lithium analysis SOC analysis device is used for acquiring the SOC of the electrochemical device and the internal resistance of the electrochemical device in each intermittent period of the plurality of intermittent periods, and obtaining a first curve based on the plurality of acquired SOCs of the electrochemical device and the plurality of internal resistances of the electrochemical device corresponding to the SOCs, wherein the first curve represents a mapping curve corresponding to the SOC and the internal resistance of the electrochemical device; and determining a lithium evolution SOC of the electrochemical device based on a first order differential curve of the first curve. According to the embodiment of the application, the unit amplitude of SOC increase and the time length of the intermittent period in the intermittent charging operation are controlled, the temperature of the electrochemical device in the intermittent charging operation is cooperatively controlled to be kept at the preset temperature, the detection sensitivity of lithium separation SOC of the electrochemical device is improved, and therefore the safety of the electrochemical device in the using process is improved.
In one embodiment of the present application, the intermittent charging device is specifically configured to perform an intermittent charging operation on the electrochemical device at a detection rate of 1.1C to 1.9C. Through cooperative control of the detection rate and the heat preservation temperature, the lithium ion battery can be charged at a proper detection rate in the detection process, and meanwhile, lithium analysis of the lithium ion battery cannot occur too early or too late within the temperature range, so that the detection accuracy of the lithium analysis SOC of the lithium ion battery after circulation is improved.
In an embodiment of the present application, the lithium analysis SOC analysis device is specifically configured to perform second order differentiation on the first order differential curve to obtain a second curve; and determining the SOC corresponding to the point where the ordinate of the second curve is less than zero for the first time as the lithium analysis SOC. The lithium analysis SOC analysis device may be integrated in a controller unit of the battery management system board.
In an embodiment of the present application, the system further includes a lithium analysis starting voltage determining device, configured to determine a lithium analysis starting voltage of the electrochemical device based on the lithium analysis SOC of the electrochemical device and a pre-established SOC-charging voltage mapping relationship, where the lithium analysis starting voltage is a charging voltage when lithium analysis occurs in the electrochemical device, and the lithium analysis starting voltage of the electrochemical device does not need to be determined through complicated calculation, so that a process of determining the lithium analysis starting voltage of the electrochemical device is simpler.
In one embodiment of the present application, the lithium deposition starting voltage determining device is specifically configured to obtain a third curve of the electrochemical device, where the third curve represents a mapping curve corresponding to the SOC and the charging voltage of the electrochemical device at the detection rate; and taking the lithium analysis SOC determined under the detection multiplying power as the current SOC, searching the charging voltage corresponding to the current SOC in the third curve as the lithium analysis starting voltage, and determining the lithium analysis starting voltage of the electrochemical device without complex calculation, so that the determination process of the lithium analysis starting voltage of the electrochemical device is simpler and more convenient.
In one embodiment of the present application, the electrochemical device comprises one of a lithium iron phosphate-based electrochemical device, a lithium nickel cobalt manganese oxide-based electrochemical device, or a lithium cobalt oxide-based electrochemical device, wherein the electrochemical device is a lithium iron phosphate-based electrochemical device, the unit amplitude ranges from 2% to 5%, and the duration of the interruption period ranges from 8 seconds to 9 seconds; the electrochemical device is a nickel cobalt lithium manganate system electrochemical device, the unit amplitude range is 2-5%, and the time length range of the interruption period is 8-10 seconds; the electrochemical device is a lithium cobaltate system electrochemical device, the unit amplitude range is 2-5%, the time length range of the interruption period is 9-10 seconds, intermittent charging operation is performed on the electrochemical devices of different systems in a targeted manner, and lithium precipitation SOCs of the electrochemical devices of different systems can be obtained more accurately. The electrochemical device selects a lithium iron phosphate system or a lithium nickel cobalt manganese oxide system, and the lithium analysis detection method provided by the application has higher detection sensitivity for a lithium analysis state.
In one embodiment of the present application, the predetermined temperature T 1 Is in the range of 20 ℃ to 30 ℃, and is capable of reducing the influence due to the temperature rise of the lithium ion battery in the intermittent charging operation, thereby further increasing the detection temperature of the lithium analysis SOC.
A third aspect of embodiments of the present application provides an electrochemical device comprising a processor and a machine-readable storage medium storing machine-executable instructions executable by the processor to perform the method steps of any one of the above aspects when the processor executes the machine-executable instructions.
A fourth aspect of embodiments of the present application provides a powered device comprising the electrochemical apparatus of the third aspect.
The embodiment of the application provides a lithium separation detection method and system for an electrochemical device and the electrochemical device, wherein in the intermittent charging operation process, the temperature is kept at a preset temperature T 1 The SOC of the electrochemical device and the internal resistance of the electrochemical device during the intermittent period are obtained by performing intermittent charging operation on the electrochemical device, so that a first curve is determined, and the lithium analysis SOC of the electrochemical device is determined based on a first-order differential curve of the first curve. According to the embodiment of the application, the unit amplitude of SOC increase and the time length of the intermittent period in the intermittent charging operation are controlled, the temperature of the electrochemical device in the intermittent charging operation is cooperatively controlled to be kept at the preset temperature, the detection sensitivity of lithium separation SOC of the electrochemical device is improved, and therefore the electrochemical device is improvedThe safety of the device during use. Of course, not all advantages described above need to be achieved at the same time in the practice of any one product or method of the present application.
Drawings
In order to illustrate the technical solutions of the present application and the prior art more clearly, the following briefly introduces examples and figures that need to be used in the prior art, it being obvious that the figures in the following description are only some examples of the present application.
FIG. 1 is a schematic flow chart of a lithium-analysis detection method of an electrochemical device according to an embodiment of the present application;
FIG. 2 is a schematic illustration of a first curve of an embodiment of the present application;
FIG. 3 is a schematic of a first order differential curve of an embodiment of the present application;
FIG. 4 is a schematic of a third curve and a first order differential curve of an embodiment of the present application;
FIG. 5 is a schematic structural diagram of a battery system according to an embodiment of the present application;
fig. 6 is a schematic structural view of a battery system according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below with reference to the accompanying drawings and examples. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other technical solutions obtained by a person of ordinary skill in the art based on the embodiments in the present application belong to the scope of protection of the present application.
In the embodiments of the present application, the present application is explained by taking a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.
An embodiment of the present application provides an electrochemical device management method, as shown in fig. 1, the method including the steps of:
s101: the electrochemical device is subjected to an intermittent charging operation,the intermittent charging operation includes a plurality of charging periods in each of which an SOC (State of Charge) of the electrochemical device is increased by a unit amplitude ranging from 2% to 5%, and a plurality of intermittent periods in which a time length ranges from 8 seconds to 10 seconds; maintaining the temperature at a predetermined temperature T during intermittent charging operation 1 (wherein the device temperature is maintained at T 1 In the range of + -0.5 deg.C, the device temperature is considered to be maintained at T 1 )。
The execution subject of the embodiment of the present application may be a BMS (Battery Management System). During operation of the electrochemical device, the battery management system may manage the electrochemical device, such as managing the charging and discharging processes of the electrochemical device. The battery management system may be integrated within the electrochemical device or may be communicatively coupled to the electrochemical device independent of the electrochemical device.
In the embodiment of the present application, the intermittent charging operation may refer to a process of intermittently charging the electrochemical device. The lithium evolution SOC may refer to an SOC associated with a lithium evolution state of the electrochemical device. For example, an intermittent charging device in a battery management system may perform an intermittent charging operation on an electrochemical device. The embodiment of the present application does not particularly limit the intermittent charging device as long as the intermittent charging operation can be achieved. The intermittent charging device may be an MCU (micro controller Unit) in a battery management system.
The intermittent charging operation includes a plurality of charging periods in each of which the SOC of the electrochemical device is increased by a unit magnitude, that is, the SOC of the electrochemical device is increased by a certain magnitude during each charging period, and a plurality of intermittent periods. In the present embodiment, the unit amplitude ranges from 2% to 5%, i.e., the SOC of the electrochemical device is increased by an amplitude of 2% to 5% during each charge. Illustratively, the unit amplitude is 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value of the period. The inventor of the present application finds that, when the unit amplitude is too small (for example, less than 2%), because the amount of electricity charged each time is small, the electrochemical device is usually in a static state in the discontinuous period, the static times of the electrochemical device in the whole detection process are increased, the detection time of the lithium deposition SOC is prolonged, and the improvement of the detection efficiency is not facilitated; when the unit amplitude is too large (for example, more than 5%), it is difficult to ensure detection sensitivity. According to the embodiment of the application, the range of unit amplitude is controlled to be within the range, so that the number of standing times of the electrochemical device can be reduced while the detection sensitivity is kept, and the detection efficiency is improved.
In the embodiment of the present application, the time duration of the interruption period ranges from 8 seconds to 10 seconds. Illustratively, the above-mentioned intermittent period may be 8 seconds, 8.5 seconds, 9 seconds, 9.5 seconds, 10 seconds, or any value of the period. The inventors of the present application have also found that, when the interruption period is too short, the relaxation time of the electrochemical device decreases, the degree of change in the voltage difference between the charging period and the interruption period is small, and the detection sensitivity decreases; when the discontinuous period is too long, the relaxation process of the electrochemical device gradually ends along with the prolongation of the discontinuous period, the change degree of the voltage difference between the charging period and the discontinuous period is reduced, and the detection sensitivity is also reduced. According to the embodiment of the application, the relaxation time of the electrochemical device is long by controlling the intermittent period within the range, so that a larger voltage difference between the charging period and the intermittent period is obtained, namely, the voltage difference between the electrochemical device during the charging period and the intermittent period is amplified.
The inventors of the present application have also found that the temperature of the electrochemical device is maintained at a predetermined temperature T by performing a soaking treatment on the electrochemical device during the intermittent charging operation 1 The detection sensitivity of the lithium analysis SOC can be improved. The inventors of the present application have found that the electrochemical device is less prone to lithium deposition as the temperature increases. In an intermittent charging operation for an electrochemical device, a technician may tend to focus only on the effect of unit amplitude and duration of the off-period on detection sensitivity, ignoring the change in temperature of the electrochemical device during the intermittent charging operation. Since lithium evolution of the electrochemical device is temperature dependent, although the electrochemical device may be placed at a certain temperature at the time of detectionIn an environment, however, the temperature of the electrochemical device increases as the intermittent charging operation proceeds, and the detection sensitivity of the lithium deposition SOC is affected. Based on this, the embodiments of the present application maintain the temperature of the electrochemical device at a predetermined temperature T 1 The influence of the temperature rise of the electrochemical device in the intermittent charging operation can be reduced, thereby further improving the detection sensitivity of the lithium analysis SOC. The embodiment of the present application is directed to maintaining the temperature of an electrochemical device at a predetermined temperature T 1 The method of (3) is not particularly limited, and for example, the electrochemical device may be placed in a thermostat to perform lithium analysis SOC detection. The thermostat device is not particularly limited in the present application, and may be, for example, a jacket, an incubator, or the like.
S102: for each of the plurality of intermittent periods, the SOC of the electrochemical device and the internal resistance of the electrochemical device for the intermittent period are acquired, and a first curve is obtained based on the plurality of SOCs of the electrochemical device and the plurality of internal resistances of the electrochemical device corresponding to the plurality of SOCs acquired.
In the intermittent charging operation, the internal resistance of the electrochemical device may be determined based on the detected charging voltage and charging current. After acquiring the SOC and the internal resistance of the electrochemical device during the plurality of intermittent periods, a plurality of data pairs consisting of the SOC and the internal resistance may be obtained, referring to fig. 2, the SOC of the electrochemical device may be used as an abscissa and the internal resistance of the electrochemical device may be used as an ordinate, points represented by the data pairs may be filled in a coordinate system, and a first curve may be obtained after fitting, where the first curve represents a mapping curve corresponding to the SOC and the internal resistance of the electrochemical device.
It can be understood that the more intensive the SOC and internal resistance data of the electrochemical device are collected, the more data pairs are obtained, and the more detailed first curve can be obtained. In the embodiment of the present application, the SOC and the internal resistance of all the intermittent periods do not necessarily need to be acquired, that is, "each intermittent period" may refer to each intermittent period of the intermittent periods in which the SOC and the internal resistance data have been acquired, rather than necessarily acquiring the SOC and the internal resistance data of all the intermittent periods, as long as a sufficient number of SOC and internal resistance data are acquired to obtain the first curve. The process of curve fitting using the data is well known to those skilled in the art, and the examples of the present application are not particularly limited.
S103: and determining the lithium analysis SOC of the electrochemical device based on the first order differential curve of the first curve.
As shown in fig. 3, in one example, first order differentiation of the first curve results in a first order differentiation curve of the first curve, which represents a rate of change of the internal resistance of the electrochemical device with the SOC. Because the first order differential curve represents the change rate of the internal resistance along with the SOC, when the change rate does not abnormally reduce in a curve flat area, no active lithium is precipitated, when the change rate abnormally reduces in a curve flat area, the active lithium is precipitated on the surface of the negative electrode and is in contact with the negative electrode, namely the graphite part of the negative electrode is connected with a lithium metal device in parallel, so that the impedance of the whole negative electrode part is reduced, the impedance of an electrochemical device is abnormally reduced when the active lithium is precipitated, and correspondingly, the flat area of the first order differential curve abnormally reduces. Referring to fig. 3,B, the point where the slope of the first-order differential curve is negative first appears, that is, the flat area of the first-order differential curve at the point B is abnormally reduced first, which indicates that the electrochemical device has a lithium precipitation tendency or has already been subjected to lithium precipitation at the point B, and then the SOC corresponding to the point B may be determined as the lithium precipitation SOC.
The lithium analysis SOC may not be measured in real time, but may be found from a charging voltage obtained in the intermittent charging operation and an SOC-charging voltage mapping table, which may be stored in a storage medium of the battery management system in advance. An SOC-charging voltage map, in which the SOCs of the electrochemical devices corresponding to different charging voltages are recorded, may be previously stored in the BMS, for example, 4.2V for 85% SOC and 4.3V for 90% SOC. As can be seen, the SOC of the electrochemical device may be determined based on the charging voltage and the SOC-charging voltage map.
In one embodiment of the present application, the electrochemical device is subjected to an intermittent charging operation at a detection rate of 1.1C (rate) to 1.9C. The inventor of the present application finds that the detection rate and the detection temperature affect the detection accuracy of the lithium deposition SOC. Specifically, the ratio of the magnification is detectedWhen the change of the temperature is detected, the electrochemical device can generate lithium precipitation too early or too late, so that the accuracy of lithium precipitation SOC is reduced, and particularly, the electrochemical device after the cycle, such as the electrochemical device after 600-700 cycles of charge and discharge, is greatly influenced by the detection rate and the temperature. When the detection rate is too small (for example, less than 1.1C), the lithium deposition SOC of the electrochemical device cannot be detected effectively; since lithium deposition occurs more easily in the electrochemical device after such cycling, when the detection rate is too large (for example, more than 2C), lithium deposition of the electrochemical device occurs early, resulting in a decrease in the detection accuracy of the lithium deposition SOC. The detection multiplying power of the embodiment of the application is 1.1C to 1.9C, and the temperature is kept to be the preset temperature T in the intermittent charging operation process 1 Through cooperative control of the detection rate and the heat preservation temperature, the electrochemical device can be charged at a proper detection rate in the detection process, and meanwhile, lithium precipitation of the electrochemical device cannot occur too early or too late within the temperature range, so that the lithium precipitation SOC detection accuracy of the electrochemical device after circulation is improved. It can be understood that, when the capacity of the electrochemical device is constant, the charging rate is proportional to the charging current, and based on this, the embodiments of the present application can also detect the current to perform the intermittent charging operation on the electrochemical device, which is reasonable.
In one embodiment of the present application, the step of determining the lithium deposition SOC of the electrochemical device based on the first order differential curve of the first curve may be:
and i, carrying out second-order differentiation on the first-order differential curve to obtain a second curve. It is understood that the second curve is a second order differential curve of the first order differential curve.
And ii, determining the SOC corresponding to the point where the ordinate of the first occurrence of the second curve is less than zero as the lithium analysis SOC.
And if the ordinate of the second curve is less than zero, determining the SOC corresponding to the point of the second curve with the ordinate less than zero for the first time as the lithium analysis SOC. In the embodiment of the present application, the ordinate of the second curve is the second-order differential internal resistance, and the abscissa of the second curve is the state of charge.
In one embodiment of the present application, the battery management system may determine the lithium deposition start voltage of the electrochemical device based on the lithium deposition SOC of the electrochemical device and a pre-established SOC-charging voltage mapping relationship.
In the embodiment of the present application, the storage medium of the battery management system may store an SOC-charging voltage mapping table in advance. After the lithium analysis SOC of the electrochemical device is determined, the voltage corresponding to the lithium analysis SOC can be obtained by searching based on the lithium analysis SOC and the SOC-charging voltage mapping relation table, namely the lithium analysis initial voltage, and the lithium analysis initial voltage of the electrochemical device is determined without complex calculation, so that the determination process of the lithium analysis initial voltage of the electrochemical device is simpler and more convenient.
In one embodiment of the present application, the step of determining a lithium deposition start voltage of the electrochemical device based on the lithium deposition SOC of the electrochemical device and a pre-established SOC-charging voltage mapping relationship comprises:
acquiring a third curve of the electrochemical device, wherein the third curve represents a mapping curve corresponding to the SOC and the charging voltage of the electrochemical device under the detection magnification;
the SOC-charging voltage mapping relationship may be represented by a third curve shown in the upper half of fig. 4, referring to fig. 4, where the abscissa of the third curve is SOC and the ordinate is charging voltage, and the third curve represents a mapping curve corresponding to SOC and charging voltage of the electrochemical device at a detection magnification (e.g., 1.3C).
And taking the lithium analysis SOC determined under the detection multiplying power as the current SOC, and searching the charging voltage corresponding to the current SOC in the third curve as the lithium analysis starting voltage.
The rate of change of the internal resistance of the electrochemical device with respect to the SOC may be represented by a first order differential curve shown in the lower half of fig. 4. Illustratively, the first order differential curve represents the rate of change of the internal resistance of the electrochemical device at the detection rate (e.g., 1.3C) with the SOC. If the determined lithium analysis SOC is 53% as indicated by point C in fig. 4, a charging voltage corresponding to the SOC of 53% may be searched in the third curve shown in fig. 4, for example, when the charging voltage searched in the third curve is 4.23V, the charging voltage is the lithium analysis starting voltage, and the lithium analysis starting voltage of the electrochemical device does not need to be determined by complicated calculation, so that the determination process of the lithium analysis starting voltage of the electrochemical device is simpler and more convenient.
The electrochemical device of the embodiment of the application comprises one of a lithium iron phosphate system electrochemical device, a lithium nickel cobalt manganese oxide system electrochemical device or a lithium cobalt oxide system electrochemical device. Generally, in the intermittent charging operation, different systems of electrochemical devices correspond to different unit amplitudes and different intermittent period durations. Based on this:
in one embodiment, the electrochemical device is a lithium iron phosphate system electrochemical device with a unit amplitude in the range of 2% to 5% and a time duration during the off period in the range of 8 seconds to 9 seconds.
In one embodiment, the electrochemical device is a lithium nickel cobalt manganese oxide system electrochemical device having a unit amplitude in a range of 2% to 3% and a period of time during the off period in a range of 8 seconds to 9 seconds.
In one embodiment, the electrochemical device is a lithium cobaltate system electrochemical device, the unit amplitude ranges from 2% to 3%, and the duration of the off period ranges from 9 seconds to 10 seconds.
According to the embodiment of the application, the electrochemical devices of different systems are set with different unit amplitudes and different time durations during the interruption, so that the intermittent charging operation is performed on the electrochemical devices of different systems more pertinently, and the lithium analysis SOC of the electrochemical devices of different systems can be obtained more accurately.
In one embodiment of the present application, the predetermined temperature T 1 Is in the range of 20 ℃ to 30 ℃, preferably 25 ℃ to 30 ℃, can reduce the influence due to the temperature rise of the electrochemical device in the intermittent charging operation, thereby further increasing the detection temperature of the lithium deposition SOC.
In one embodiment, the step of generating the first curve comprises:
step a: acquiring a first voltage, a first current and a first SOC of the electrochemical device at a second moment, and a second voltage and a second current of the electrochemical device at a third moment;
the second time is the time of stopping charging, and the voltage, the current and the SOC of the electrochemical device at the second time, namely the first voltage, the first current and the first SOC, can be obtained and are respectively marked as V 1 、I 1 And SOC 1 . Similarly, the voltage and current of the electrochemical device at the third moment, i.e. the second voltage and the second current, respectively denoted as V, can be obtained 2 And I 2 。
Step b: and calculating the voltage change value and the current change value of the electrochemical device during the interruption period.
The duration of the discontinuous period is the time interval between the third moment and the second moment, the voltage change value of the electrochemical device during the discontinuous period is delta V, and delta V = V 2 -V 1 The current change value of the electrochemical device during the interruption is Delta I, delta I = I 2 -I 1 。
Step c: calculating a first internal resistance of the electrochemical device during the interruption period based on the voltage change value and the current change value, and taking the first internal resistance and the first SOC as one data pair of a first curve, wherein the data pair is the corresponding relation of the internal resistance and the SOC;
the first internal resistance of the electrochemical device during the interruption is R 1 ，R 1 = Δ V/Δ I. R is to be 1 And SOC 1 One of the data pairs as a first curve.
In the same way as described above, a plurality of data pairs can be obtained.
Step d: based on the calculated plurality of data pairs, a first curve is generated.
And filling points represented by the data pairs into a coordinate system by taking the SOC of the electrochemical device as an abscissa and the internal resistance of the electrochemical device as an ordinate, and fitting to obtain a first curve. After the first curve is obtained, the lithium precipitation SOC of the electrochemical device can be determined through the first curve, and therefore the SOC of the electrochemical device with the lithium precipitation tendency can be determined.
The embodiment of the application provides a lithium separation detection method for an electrochemical device, which is used for keeping the temperature to be a preset temperature T in the intermittent charging operation process 1 The SOC of the electrochemical device and the internal resistance of the electrochemical device during the intermittent period are obtained by performing an intermittent charging operation on the electrochemical device, thereby determining a first curve, and then determining the electrochemical device based on a first order differential curve of the first curveThe lithium deposition SOC. According to the embodiment of the application, the unit amplitude of SOC increase and the time length of the intermittent period in the intermittent charging operation are controlled, the temperature of the electrochemical device in the intermittent charging operation is cooperatively controlled to be kept at the preset temperature, the detection sensitivity of lithium separation SOC of the electrochemical device is improved, and therefore the safety of the electrochemical device in the using process is improved.
The present application also provides a battery system, as shown in fig. 5, the battery system 500 includes an intermittent charging device 501 and a lithium analysis SOC analysis device 502. The intermittent charging device 501 is used to perform an intermittent charging operation on the electrochemical device, the intermittent charging operation including a plurality of charging periods and a plurality of intermittent periods, the SOC of the electrochemical device is increased by a unit amplitude in each charging period, the unit amplitude is in a range of 2% to 5%, and the duration of the intermittent period is in a range of 8 seconds to 10 seconds; maintaining the temperature at a predetermined temperature T during the intermittent charging operation 1 (ii) a The lithium analysis SOC analysis device 502 is configured to, for each of the plurality of intermittent periods, acquire the SOC of the electrochemical device and the internal resistance of the electrochemical device for the intermittent period, and obtain a first curve based on the acquired plurality of SOCs of the electrochemical device and the plurality of internal resistances of the electrochemical device corresponding to the plurality of SOCs, the first curve representing a mapping curve corresponding to the SOC and the internal resistance of the electrochemical device; and determining the lithium analysis SOC of the electrochemical device based on the first-order differential curve of the first curve.
In one embodiment, the intermittent charging device is specifically configured to: the electrochemical device was subjected to an intermittent charging operation at a detection rate of 1.1C to 1.9C.
In one embodiment, the lithium analysis SOC analysis device is specifically configured to: carrying out second order differentiation on the first order differential curve to obtain a second curve; and determining the SOC corresponding to the point where the ordinate of the second curve is less than zero for the first time as the lithium analysis SOC.
In one embodiment, the system further comprises a lithium deposition start voltage determining device for determining a lithium deposition start voltage of the electrochemical device based on the lithium deposition SOC of the electrochemical device and a pre-established SOC-charging voltage mapping relationship, wherein the lithium deposition start voltage is a charging voltage at which lithium deposition occurs in the electrochemical device.
In one embodiment, the lithium extraction onset voltage determining means is specifically configured to: acquiring a third curve of the electrochemical device, wherein the third curve represents a mapping curve corresponding to the SOC and the charging voltage of the electrochemical device under the detection magnification; and taking the lithium analysis SOC determined under the detection multiplying power as the current SOC, and searching the charging voltage corresponding to the current SOC in the third curve as the lithium analysis starting voltage.
In one embodiment, the electrochemical device comprises one of a lithium iron phosphate system electrochemical device, a lithium nickel cobalt manganese oxide system electrochemical device or a lithium cobalt oxide system electrochemical device, wherein the electrochemical device is a lithium iron phosphate system electrochemical device, the unit amplitude ranges from 2% to 5%, and the duration of the interruption period ranges from 8 seconds to 9 seconds; the electrochemical device is a nickel cobalt lithium manganate system electrochemical device, the unit amplitude range is 2-5%, and the time length range of the interruption period is 8-10 seconds; the electrochemical device is a lithium cobaltate system electrochemical device, the unit amplitude ranges from 2% to 5%, and the time length of the intermittent period ranges from 9 seconds to 10 seconds.
In one embodiment, the predetermined temperature T 1 In the range of 20 ℃ to 30 ℃.
The embodiment of the present application further provides a battery system, as shown in fig. 6, the system 600 includes a controller unit 601 and a machine-readable storage medium 602, and the system 600 may further include an interface 603, a power interface 604, and a rectification circuit 605. The controller unit 601 is configured to perform an intermittent charging operation on the lithium ion battery 505, obtain the SOC of the electrochemical device and the internal resistance of the electrochemical device during the intermittent period, obtain a first curve based on the obtained SOCs of the electrochemical device and the internal resistances of the electrochemical device corresponding to the SOCs, and determine a lithium analysis SOC of the electrochemical device based on a first-order differential curve of the first curve; the interface 603 is used for electrically connecting with the lithium ion battery 505; the power interface 604 is used for connecting with an external power supply; the rectifier circuit 605 is used to rectify the input current; the machine-readable storage medium 602 stores machine-executable instructions executable by the controller unit 601 to perform the method steps described in any of the above embodiments when the controller unit 601 executes the machine-executable instructions.
There is also provided in an embodiment of the present application an electrochemical device comprising a processor and a machine-readable storage medium having stored thereon machine-executable instructions executable by the processor to perform a method according to any one of the embodiments described above.
The embodiment of the application also provides electric equipment, which comprises the electrochemical device of the embodiment. The electrochemical device provides electrical energy to the electrical equipment. Exemplary powered devices include laptop computers, cell phones, and the like.
The machine-readable storage medium may include a Random Access Memory (RAM) or a non-volatile Memory (non-volatile Memory), such as at least one disk Memory. Optionally, the memory may also be at least one memory device located remotely from the processor.
The Processor may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; the Integrated Circuit may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other Programmable logic device, a discrete Gate or transistor logic device, or a discrete hardware component.
For the electrochemical device/consumer embodiments, since they are substantially similar to the method embodiments, the description is relatively simple, and reference may be made to the partial description of the method embodiments for relevant points.
Preparation example 1
Preparation of lithium nickel cobalt manganese oxide system lithium ion battery：
Preparing a positive pole piece: mixing the nickel cobalt lithium manganate serving as the positive electrode active material, acetylene black and polyvinylidene fluoride (PVDF) according to the mass ratio of 94: 3, adding N-methylpyrrolidone (NMP) serving as a solvent, blending into slurry with the solid content of 75wt%, and uniformly stirring. And uniformly coating the slurry on one surface of an aluminum foil with the thickness of 12 micrometers, drying at 90 ℃, carrying out cold pressing to obtain a positive pole piece with the thickness of a positive active material layer of 100 micrometers, and repeating the steps on the other surface of the positive pole piece to obtain the positive pole piece with the positive active material layer coated on the two surfaces. Cutting the positive pole piece into the specification of 74mm multiplied by 867mm, and welding the pole ear for standby.
Preparing a negative pole piece: mixing the negative active material artificial graphite, acetylene black, styrene butadiene rubber and sodium carboxymethylcellulose according to the mass ratio of 96: 1: 1.5, adding deionized water as a solvent, preparing slurry with the solid content of 70wt%, and uniformly stirring. And uniformly coating the slurry on one surface of a copper foil with the thickness of 8 mu m, drying at 110 ℃, obtaining a negative pole piece with the negative active material layer coated on one surface and the thickness of the negative active material layer of 150 mu m after cold pressing, and then repeating the coating steps on the other surface of the negative pole piece to obtain the negative pole piece with the negative active material layer coated on the two surfaces. Cutting the negative pole piece into the specification of (74 mm multiplied by 867 mm) and welding a pole ear for later use.
Preparing an isolating membrane: a Polyethylene (PE) porous polymer film having a thickness of 15 μm was used as a separator.
Preparing an electrolyte: mixing non-aqueous organic solvents of Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) at a mass ratio of 1: 1 in an environment with a water content of less than 10ppm, and adding lithium hexafluorophosphate (LiPF) to the non-aqueous organic solvent 6 ) Dissolving and mixing uniformly to obtain electrolyte, wherein the LiPF is 6 The concentration of (2) is 1.15mol/L.
Preparing a lithium ion battery: and (3) stacking the prepared positive pole piece, the isolating film and the negative pole piece in sequence, so that the isolating film is positioned between the positive pole piece and the negative pole piece to play an isolating role, and winding to obtain the electrode assembly. And (3) putting the electrode assembly into an aluminum-plastic film packaging bag, dehydrating at 80 ℃, injecting the prepared electrolyte, and performing vacuum packaging, standing, formation, shaping and other processes to obtain the lithium ion battery, wherein the rated capacity of the lithium ion battery is 5Ah.
Preparation example 2
Preparation of lithium iron phosphate system lithium ion battery：
Preparing a positive pole piece: mixing the positive active material lithium iron phosphate, acetylene black and polyvinylidene fluoride (PVDF) according to the mass ratio of 94: 3, adding N-methylpyrrolidone (NMP) as a solvent, preparing slurry with the solid content of 75%, and uniformly stirring. And uniformly coating the slurry on one surface of an aluminum foil with the thickness of 12 mu m, drying at 90 ℃, obtaining a positive pole piece with the thickness of a positive active material layer of 100 mu m after cold pressing, and then repeating the steps on the other surface of the positive pole piece to obtain the positive pole piece with the positive active material layer coated on the two surfaces. Cutting the positive pole piece into the specification of 74mm multiplied by 867mm, and welding the pole ear for standby.
The preparation of the negative electrode plate, the preparation of the isolating membrane, the preparation of the electrolyte and the preparation method of the lithium ion battery are the same as the preparation example 1. The rated capacity of the lithium ion battery is 4Ah.
Example 1
< detection of lithium deposition SOC >
Taking 10 lithium ion batteries prepared in preparation example 1, each lithium ion battery was tested according to the following intermittent charging operation steps: after the lithium ion battery is subjected to charge-discharge cycle for 600 times, the lithium ion battery is placed into a heat-insulating sleeve, and the heat-insulating temperature is set to be 25 ℃. And carrying out intermittent charging operation on the lithium ion battery, wherein the unit amplitude of the intermittent charging operation is 2%, the time length of an intermittent period is 8 seconds, the detection multiplying power is 1.5 ℃, and carrying out lithium analysis detection to obtain a lithium analysis detection result. Then, disassembling the 10 batteries, observing the actual lithium separation condition, and observing whether a gray white or white solid matter exists on the surface of the negative electrode, wherein if the gray white or white solid matter does not exist on the surface of the negative electrode, the lithium separation of the lithium ion battery is not performed; if yes, the lithium ion battery is indicated to have lithium separation. According to the actual lithium analysis condition and the lithium analysis detection result of 10 lithium ion batteries, the lithium analysis detection rate shown in table 1 is obtained.
Wherein, the lithium analysis detection rate = accurately detecting the number of lithium analysis battery particles/actually detecting the number of lithium analysis battery particles.
Examples 2 to 8
The procedure was the same as in example 1, except that in the intermittent charging operation, the unit width, the time length of the intermittent period, the keeping warm temperature, and the detection magnification during the intermittent charging operation were adjusted as shown in table 1.
Example 9
The procedure of example 1 was repeated, except that the lithium ion battery was subjected to charge/discharge cycles 700 times.
Example 10
The procedure of example 1 was repeated, except that the lithium ion battery of preparation example 2 was used and the time period of the intermittent period was adjusted to 9 seconds.
Comparative example 1
The procedure of example 1 was repeated, except that the intermittent period was adjusted to 3 seconds in < detection of lithium deposition SOC > and the lithium ion battery was not placed in the jacket.
Comparative example 2
The same as example 1 was repeated except that the time period of the intermittent period was adjusted to 3 seconds in < detection of lithium deposition SOC >.
Comparative example 3
The procedure of example 1 was repeated, except that the intermittent period was set to 8 seconds in < detection of lithium evolution SOC > and the lithium ion battery was not placed in the jacket.
Comparative example 4
Except that in < detection of lithium evolution SOC >, the lithium ion battery was subjected to charge and discharge cycles 700 times, and the rest was the same as in comparative example 1.
TABLE 1
Figure BDA0003848837230000141
As can be seen from example 1 and comparative examples 1 to 3, the lithium deposition detection rate of example 1 substantially coincides with the actual lithium deposition rate; and the lithium precipitation detection rate in comparative examples 1 to 3 is much lower than the actual lithium precipitation rate. It can be seen that the detection conditions of lithium analysis of the lithium ion battery are basically consistent with the lithium analysis conditions observed during actual disassembly through cooperative control of the unit amplitude, the duration of the interruption period, the detection rate and the temperature of the lithium ion battery during the detection process in the intermittent charging process, and the detection sensitivity of the lithium analysis SOC is improved.
As can be seen from examples 1 to 9, by cooperatively controlling the unit amplitude, the duration of the interruption period, the detection rate in the intermittent charging process, and the temperature of the lithium ion battery in the detection process within the range of the present application, the detected lithium analysis condition is substantially consistent with the lithium analysis condition observed in actual disassembly, which indicates that the lithium analysis detection method of the present application can effectively detect the lithium analysis phenomenon of the lithium ion battery, and the detection sensitivity of the lithium analysis SOC is improved.
As can be seen from example 9 and comparative example 4, for the lithium ion batteries with different cycle numbers, for example, the lithium ion battery with example 9 for 700 cycles, the lithium analysis detection rate is substantially consistent with the actual lithium analysis rate; while comparative example 4 shows a much lower detectable rate of lithium deposition than the actual rate. Therefore, for lithium ion batteries with different cycle times, the lithium analysis detection method can effectively detect the lithium analysis phenomenon of the lithium ion batteries.
As can be seen from examples 1 and 10, the lithium analysis detection method of the present application can also effectively detect the lithium analysis phenomenon of lithium ion batteries of different systems (for example, the lithium nickel cobalt manganese oxide system lithium ion batteries of examples 1 to 9 and the lithium iron phosphate system lithium ion battery of example 10), especially lithium ion batteries that actually have lithium analysis after charge and discharge cycles.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims (16)

1. An electrochemical device lithium analysis detection method, wherein the method comprises:
performing an intermittent charging operation on an electrochemical device, said intermittent charging operation comprising a plurality of charging periods and a plurality of intermittent periods, said electrochemical device during each of said charging periodsIncreasing the unit amplitude of the set SOC, wherein the unit amplitude ranges from 2% to 5%, and the duration of the discontinuous period ranges from 8 seconds to 10 seconds; maintaining the temperature at a predetermined temperature T during intermittent charging operation 1 ；
Acquiring the SOC of the electrochemical device and the internal resistance of the electrochemical device during each of the plurality of intermittent periods, and obtaining a first curve based on the plurality of acquired SOCs of the electrochemical device and the plurality of internal resistances of the electrochemical device corresponding to the plurality of SOCs, wherein the first curve represents a mapping curve corresponding to the SOC and the internal resistance of the electrochemical device; and
determining a lithium evolution SOC of the electrochemical device based on a first order differential curve of the first curve.
2. The electrochemical device lithium analysis detection method of claim 1, wherein the step of intermittently charging the electrochemical device comprises:
the electrochemical device is subjected to an intermittent charging operation at a detection rate of 1.1C to 1.9C.
3. The electrochemical device lithium analysis detection method of claim 1, wherein the step of determining the lithium analysis SOC of the electrochemical device based on the first order differential curve of the first curve comprises:
carrying out second order differentiation on the first order differential curve to obtain a second curve;
and determining the SOC corresponding to the point where the ordinate of the second curve is less than zero for the first time as the lithium analysis SOC.
4. The electrochemical device lithium extraction detection method of claim 2, wherein the method further comprises:
determining a lithium analysis starting voltage of the electrochemical device based on the lithium analysis SOC of the electrochemical device and a pre-established SOC-charging voltage mapping relation, wherein the lithium analysis starting voltage is a charging voltage when lithium analysis occurs to the electrochemical device.
5. The electrochemical device lithium deposition detection method according to claim 4, wherein the step of determining the lithium deposition start voltage of the electrochemical device based on the lithium deposition SOC of the electrochemical device and a pre-established SOC-to-charging voltage mapping relationship comprises:
acquiring a third curve of the electrochemical device, wherein the third curve represents a mapping curve corresponding to the SOC and the charging voltage of the electrochemical device under the detection magnification;
and taking the lithium analysis SOC determined under the detection multiplying power as the current SOC, and searching the charging voltage corresponding to the current SOC in the third curve as the lithium analysis starting voltage.
6. The electrochemical device lithium extraction detection method of claim 1, wherein the electrochemical device comprises one of a lithium iron phosphate system electrochemical device, a lithium nickel cobalt manganese oxide system electrochemical device, or a lithium cobalt oxide system electrochemical device, wherein,
the electrochemical device is a lithium iron phosphate system electrochemical device, the unit amplitude range is 2-5%, and the time length range of the interruption period is 8-9 seconds;
the electrochemical device is a nickel cobalt lithium manganate system electrochemical device, the unit amplitude range is 2-5%, and the time length range of the interruption period is 8-10 seconds;
the electrochemical device is a lithium cobaltate system electrochemical device, the unit amplitude ranges from 2% to 3%, and the time length of the intermittent period ranges from 9 seconds to 10 seconds.
7. The electrochemical device lithium analysis detection method of claim 1, wherein the predetermined temperature T 1 In the range of 20 ℃ to 30 ℃.
8. A battery system, comprising: an intermittent charging device and a lithium analysis SOC analysis device,
the intermittent charging device is used for intermittently charging the electrochemical deviceA charging operation including a plurality of charging periods in each of which the SOC of the electrochemical device is increased by a unit amplitude ranging from 2% to 5%, and a plurality of intermittent periods having a duration ranging from 8 seconds to 10 seconds; maintaining the temperature at a predetermined temperature T during intermittent charging operation 1 ；
The lithium deposition SOC analysis device is used for acquiring the SOC of the electrochemical device and the internal resistance of the electrochemical device in each intermittent period in the intermittent periods, and obtaining a first curve based on the acquired SOC of the electrochemical device and the internal resistances of the electrochemical device corresponding to the SOC, wherein the first curve represents a mapping curve corresponding to the SOC and the internal resistance of the electrochemical device; and
determining a lithium evolution SOC of the electrochemical device based on a first order differential curve of the first curve.
9. The system of claim 8, wherein the intermittent charging device is specifically configured to:
the electrochemical device is subjected to an intermittent charging operation at a detection rate of 1.1C to 1.9C.
10. The system of claim 8, wherein the lithium analysis SOC analysis device is specifically configured to:
carrying out second order differentiation on the first order differential curve to obtain a second curve;
and determining the SOC corresponding to the point where the ordinate of the second curve is less than zero for the first time as the lithium analysis SOC.
11. The system according to claim 9, wherein the system further comprises a lithium deposition start voltage determination means for determining a lithium deposition start voltage of the electrochemical device based on a lithium deposition SOC of the electrochemical device and a pre-established SOC-to-charging voltage mapping relationship, the lithium deposition start voltage being a charging voltage at which lithium deposition occurs in the electrochemical device.
12. The system of claim 11, wherein the lithium deposition onset voltage determination device is specifically configured to:
acquiring a third curve of the electrochemical device, wherein the third curve represents a mapping curve corresponding to the SOC and the charging voltage of the electrochemical device under the detection magnification;
and taking the lithium analysis SOC determined under the detection multiplying power as the current SOC, and searching the charging voltage corresponding to the current SOC in the third curve as the lithium analysis starting voltage.
13. The system of claim 8, wherein the electrochemical device comprises one of a lithium iron phosphate system electrochemical device, a lithium nickel cobalt manganese oxide system electrochemical device, or a lithium cobalt oxide system electrochemical device, wherein,
the electrochemical device is a lithium iron phosphate system electrochemical device, the unit amplitude range is 2-5%, and the time length range of the interruption period is 8-9 seconds;
the electrochemical device is a nickel cobalt lithium manganate system electrochemical device, the unit amplitude range is 2-5%, and the time length range of the interruption period is 8-10 seconds;
the electrochemical device is a lithium cobaltate system electrochemical device, the unit amplitude ranges from 2% to 5%, and the time length of the interruption period ranges from 9 seconds to 10 seconds.
14. The system of claim 8, wherein the predetermined temperature T 1 In the range of 20 ℃ to 30 ℃.
15. An electrochemical device comprising a processor and a machine-readable storage medium having stored thereon machine-executable instructions executable by the processor, the processor when executing the machine-executable instructions implementing the method of any one of claims 1 to 7.
16. An electric device comprising the electrochemical device according to claim 15.
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