CN114879064A - Method for judging SOC (state of charge) of lithium metal module battery pack and life prediction method - Google Patents
Method for judging SOC (state of charge) of lithium metal module battery pack and life prediction method Download PDFInfo
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- CN114879064A CN114879064A CN202210602373.0A CN202210602373A CN114879064A CN 114879064 A CN114879064 A CN 114879064A CN 202210602373 A CN202210602373 A CN 202210602373A CN 114879064 A CN114879064 A CN 114879064A
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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
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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]
- G01R31/392—Determining battery ageing or deterioration, e.g. state of health
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Abstract
The invention discloses a method for judging the SOC of a lithium metal module battery pack and a method for predicting the service life, wherein the method for judging the SOC of the lithium metal module battery pack comprises the following steps: s1, introducing a pressure sensor between the battery cores; s2, charging the lithium metal module battery from a full discharge state to a full charge state, and recording the average pressure value P of the plurality of battery cells when the SOC is 0 0 Average value P of pressures of a plurality of cells when SOC is 1 1 A 1 is to P 1 And P 0 Substitution formula SOC ═ k (P) 1 ‑P 0 ) SOC is 1, obtain k value and record P y ＝P 0 (ii) a S3, carrying out charge-discharge circulation on the lithium metal module battery, monitoring the terminal voltage of the lithium metal module battery and recording the terminal voltage as V x When V is x ≥V 0.8 Then, giving an SOC value through terminal voltage; when V is x＜ V 0.8 Measuring the real-time pressure value of each cell, and taking the average value to be recorded as P x According to the formula SOC x ＝k*(P x ‑P y ) Calculating SOC x Value, P y The initial pressure average value or the recalibrated pressure average value of a plurality of battery cells is obtained; s4, monitoring the residual service life of the lithium metal module battery, and comparing P when the residual service life is reduced by 50 circles y And carrying out recalibration.
Description
Technical Field
The invention relates to a lithium battery technology, in particular to a method for predicting the SOC of a lithium metal module battery pack and a method for predicting the service life of the lithium metal module battery pack.
Background
State of charge (SOC) is the ratio of the remaining charge to the total charge of the battery under the same conditions at a certain discharge rate. The estimation of the state of charge (SOC) of the power battery is one of the important functions of a battery management system, and for an electric vehicle, the accurate estimation of the SOC of the power battery is the basis of the functions of estimation of the remaining mileage of the electric vehicle, estimation of the capacity of the power battery, fault diagnosis and the like.
In the practical application of the lithium battery, the accurate SOC value can reflect the actual residual working time of the electric equipment, and once the SOC measurement is abnormal, the electric equipment can not utilize the actual effective capacity of the battery to the maximum extent, so that the performance of the battery is seriously influenced. In current battery management systems, the measurement of SOC is mostly based on a technique that gives a corresponding SOC value by a terminal voltage of a corresponding battery pack. This approach is sufficient for testing the SOC of a typical lithium ion battery pack, but this technique is not suitable for use in a lithium metal battery, since the negative electrode of the lithium metal battery uses lithium metal rather than graphite, the charging/discharging platform of the battery is more stable, that is, in a certain part of the SOC interval, the voltage value changes too little to correspond to the actual SOC effectively. And the normal working interval of the electric equipment is in the range, so that SOC misjudgment is easy to occur in the working process of the equipment, and unnecessary system errors are caused.
The practical long-time endurance of the lithium metal battery pack is often needed, and if the charging mode is unreasonable, the lithium metal battery pack can not reach the expected electric quantity, the endurance time is insufficient, and the service life of the lithium metal battery pack is directly influenced.
In view of the above problems, no effective solution has been proposed.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for judging the SOC of a lithium metal module battery pack and a method for predicting the service life of the lithium metal module battery pack.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a method for judging the SOC of a lithium metal module battery pack comprises the following steps:
s1, introducing a pressure sensor between the module battery cores;
s2, in the initialization process: let lithium metal module battery charge to full charge state under from full discharge state to when recording SOC ═ 0, pressure average value P of a plurality of electric cores in the lithium metal module battery 0 When SOC is 1, the average value P of the pressures of the plurality of cells in the lithium metal module battery 1 P to be obtained 1 And P 0 Substituted into the formula SOC ═ k (P) 1 -P 0 ) When SOC is 1, k is obtained and P is recorded y ＝P 0 ；
S3, measurement of SOC: carrying out charge-discharge circulation on the lithium metal module battery, monitoring the terminal voltage of the lithium metal module battery in real time and recording the terminal voltage as V x When V is x ≥V 0.8 Then, giving an SOC value through terminal voltage; when V is x＜ V 0.8 Respectively measuring the real-time pressure value of each battery cell, and taking the average value as P x According to the formula SOC x ＝k*(P x -P y ) Calculating to obtain SOC x A value of wherein P y The initial pressure average value or the recalibrated pressure average value of the plurality of battery cells is obtained;
s4, recalibrating P y : monitoring the residual service life S of the lithium metal module battery in real time, and when the residual service life S of the lithium metal module battery is reduced by 50 circles every time, comparing P with P y Recalibrating, namely discharging the lithium metal module battery to SOC (state of charge) 0, and recording the pressure of a plurality of battery cells in the lithium metal module batteryAverage value P y 。
Preferably, lithium metal module battery includes frame construction and a plurality of electric core, and is a plurality of electric core stacks in frame construction in proper order, frame construction includes splint one and splint two, splint one and splint two are located the two electric core outsides in the outside respectively, and in the initialization process, through the pressure sensor detection pressure value between splint and the electric core and between electric core and the electric core.
Preferably, in step S3, the formula for calculating SOC by terminal voltage is SOC ═ terminal voltage-discharge cutoff voltage)/(charge cutoff voltage-discharge cutoff voltage.
A method for predicting the service life of a lithium metal module battery pack comprises the following steps:
c1, in the initialization process, charging the lithium metal module battery from a full discharge state to a full charge state, and recording a corresponding pressure value P when the SOC is 0.8 0.8 And terminal voltage V 0.8 ；
C2, carrying out charge-discharge circulation on the lithium metal module battery, monitoring the terminal voltage of the lithium metal module battery in real time and recording the terminal voltage as V x When V is x ＝V 0.8 In the process, the real-time pressure average value of a plurality of battery cells in the lithium metal module battery is measured and recorded as P x 0.8 When P is x 0.8 ＞1.5*P 0.8 In the process, the lithium metal module battery is degraded and used, and the maximum SOC charge value is set to be 0.8; when P is present x 0.8 ≤1.5*P 0.8 And calculating the residual service life S of the lithium metal module battery, and normally circulating the lithium metal module battery.
Preferably, in step C2, the remaining service life S of the lithium metal module battery is calculated by the following formula: s ═ 1.5 × P 0.8 -P x 0.8 )/(P x 0.8 -P x-1 0.8 ) In which P is x 0.8 When the number of cycles is x, and the SOC is 0.8, the average value of the pressure of a plurality of battery cells in the lithium metal module battery is P x-1 0.8 When the number of cycles is x-1 and the SOC is 0.8, the average value of the pressures of the plurality of battery cells in the lithium metal module battery is obtained.
Compared with the prior art, the method for predicting the SOC of the lithium metal module battery pack and the method for predicting the service life have the advantages that:
(1) the lithium negative electrode used in the lithium metal module battery is different from the conventional graphite negative electrode, and the working principle of the lithium metal module battery is that the lithium ion is stored in a mode that the lithium ion is directly deposited/dissolved on the surface of the negative electrode. Therefore, inevitable can make the volume of lithium metal module battery take place deformation of certain degree, uses the mode of adding frame construction at a plurality of electric cores in the use of actual lithium metal module battery to control electric core. In the charging process, the pressure between the frame structure and the battery cell and the pressure between the battery cell and the battery cell can be increased/reduced along with the charging/discharging process, then the pressure sensor is used for accurately measuring the SOC of the battery cell according to the corresponding relation between the pressure and the capacity, the scheme is low in cost, and the accuracy is high.
(2) Lithium metal module battery is at the circulation in-process, along with going on of charge-discharge, can form "dying lithium" in lithium negative pole one side, because the thickness increase of these existence feasible electric cores of "dying lithium", the increase that is shown for both sides pressure because of the existence of frame construction and adjacent electric core in the use of actual lithium metal electricity core. In the charging and discharging front section, the lithium metal module battery takes lithium as a negative electrode, the working voltage change value of the lithium metal module battery is small, and the SOC is difficult to judge through the voltage change.
(3) In different cycles, the same voltage will correspond to different pressures due to the generation of dead lithium. The increase of the pressure numerical value reflects the increase of dead lithium, so that the service life of the lithium metal module battery is accurately predicted and calculated through the application of the invention.
(4) When the pressure increase caused by the generation of the dead lithium exceeds a certain value, the battery is judged to be degraded to use, namely the SOC of the battery does not exceed 80% at most now, and the safety of a battery system is improved.
Drawings
Fig. 1 is a flowchart illustrating a method for determining the SOC of a lithium metal module battery pack according to this embodiment.
Fig. 2 is a block flow diagram of a method for predicting the life of a lithium metal module battery pack in the present embodiment.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
Examples 1,
A method for judging the SOC of a lithium metal module battery pack comprises the following steps:
s1, introducing a pressure sensor between the module battery cores;
s2, in the initialization process: let lithium metal module battery charge to full charge state under the full discharge state to when recording SOC ═ 0, pressure average value P of a plurality of electric cores in lithium metal module battery 0 When SOC is 1, the average value P of the pressures of the plurality of cells in the lithium metal module battery 1 P to be obtained 1 And P 0 Substituted into the formula SOC ═ k (P) 1 -P 0 ) When SOC is 1, k is obtained and P is recorded y ＝P 0 ；
S3, measurement of SOC: carrying out charge-discharge circulation on the lithium metal module battery, monitoring the terminal voltage of the lithium metal module battery in real time and recording the terminal voltage as V x When V is x ≥V 0.8 Then, giving an SOC value through terminal voltage; when V is x＜ V 0.8 In the process, the real-time pressure value of each cell is measured respectively, and the average value is recorded as P x According to the formula SOC x ＝k*(P x -P y ) Calculating to obtain SOC x A value of wherein P y The initial pressure average value or the recalibrated pressure average value of the plurality of battery cells is obtained;
s4, recalibrating P y : monitoring the residual service life S of the lithium metal module battery in real time, and when the residual service life S of the lithium metal module battery is reduced by 50 circles every time, comparing P with P y Recalibrating, namely discharging the lithium metal module battery to SOC (state of charge) 0, and recording the pressure average value P of a plurality of battery cells in the lithium metal module battery y 。
Above-mentioned lithium metal module battery includes frame construction and a plurality of electric core, and a plurality of electric cores stack in frame construction in proper order, and frame construction includes splint one and splint two, and splint one and splint two are located the two electric core outsides in the outside respectively, and in the initialization process, through the pressure sensor detection pressure value between splint and the electric core and between electric core and the electric core.
In step S3, the equation for calculating SOC by terminal voltage is SOC ═ terminal voltage-discharge cutoff voltage)/(charge cutoff voltage-discharge cutoff voltage.
Test example:
a plurality of NCM523/Li 50Ah battery cores are assembled to form the lithium metal module battery, 0.33C and 3.0-4.3V charging and discharging tests are carried out by using a charging and discharging cabinet, and the charging and discharging cabinet can give out voltage change and SOC change of the lithium metal module battery in the charging and discharging process.
In test examples 1 to 3, the SOC is calculated by the actual SOC given by the charge and discharge cabinet and the method of the present application, and the feasibility of the present application is determined by the SOC difference between the two SOC at the same time period.
Comparative examples 1-3 actual SOC given by the charge and discharge cabinet and terminal voltage given by the charge and discharge cabinet were calculated SOC using the prior art and compared with test examples 1-3.
It can be seen that, in the prior art, only the terminal voltage is used for calculating the SOC, and in a certain period of time, because the terminal voltage fluctuation is too small, an accurate SOC value cannot be given.
Examples 2,
A method for predicting the life of a lithium metal module battery pack, as shown in fig. 2, comprises the following steps:
c1, in the initialization process, charging the lithium metal module battery from the full discharge state to the full charge state, and recording the corresponding pressure when the SOC is 0.8Value P 0.8 And terminal voltage V 0.8 ；
C2, carrying out charge-discharge circulation on the lithium metal module battery, monitoring the terminal voltage of the lithium metal module battery in real time and recording the terminal voltage as V x When V is x ＝V 0.8 In the process, the real-time pressure average value of a plurality of battery cells in the lithium metal module battery is measured and recorded as P x 0.8 When P is x 0.8 ＞1.5*P 0.8 In the process, the lithium metal module battery is degraded and used, and the maximum SOC charge value is set to be 0.8; when P is present x 0.8 ≤1.5*P 0.8 And calculating the residual service life S of the lithium metal module battery, and normally circulating the lithium metal module battery.
In step C2, the remaining service life S of the lithium metal module battery is calculated by the following formula: s ═ 1.5 × P 0.8 -P x 0.8 )/(P x 0.8 -P x-1 0.8 ) In which P is x 0.8 When the number of cycles is x, and the SOC is 0.8, the average value of the pressure of a plurality of battery cells in the lithium metal module battery is P x-1 0.8 When the number of cycles is x-1 and the SOC is 0.8, the average value of the pressures of the plurality of battery cells in the lithium metal module battery is obtained.
Test example:
a plurality of NCM523/Li 50Ah battery cores are assembled to form a lithium metal module battery, a charge and discharge cabinet is used for conducting a 0.33C,3.0-4.3V charge and discharge test, the number of turns and the capacity retention rate are recorded, and meanwhile, the number of remaining turns is predicted through the method for predicting the service life of the lithium metal module battery in the patent application.
Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that modifications and variations of the present invention are possible to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A method for judging the SOC of a lithium metal module battery pack is characterized by comprising the following steps: the method comprises the following steps:
s1, introducing a pressure sensor between the module battery cores;
s2, in the initialization process: let lithium metal module battery charge to full charge state under the full discharge state to when recording SOC ═ 0, pressure average value P of a plurality of electric cores in lithium metal module battery 0 When SOC is 1, the average value P of the pressures of the plurality of cells in the lithium metal module battery 1 P to be obtained 1 And P 0 Substituted into the formula SOC ═ k (P) 1 -P 0 ) When SOC is 1, k is obtained and P is recorded y ＝P 0 ；
S3, measurement of SOC: carrying out charge-discharge circulation on the lithium metal module battery, monitoring the terminal voltage of the lithium metal module battery in real time and recording the terminal voltage as V x When V is x ≥V 0.8 Then, giving an SOC value through terminal voltage; when V is x＜ V 0.8 Respectively measuring the real-time pressure value of each battery cell, and taking the average value as P x According to the formula SOC x ＝k*(P x -P y ) Calculating to obtain SOC x A value of wherein P y The initial pressure average value or the recalibrated pressure average value of the plurality of battery cells is obtained;
s4, recalibrating P y : monitoring the residual service life S of the lithium metal module battery in real time, and when the residual service life S of the lithium metal module battery is reduced by 50 circles every time, comparing P with P y Recalibrating, namely discharging the lithium metal module battery to SOC (state of charge) 0, and recording the pressure average value P of a plurality of battery cells in the lithium metal module battery y 。
2. The method of determining the SOC of a lithium metal module battery pack according to claim 1, wherein: lithium metal module battery includes frame construction and a plurality of electric core, and is a plurality of the electric core stacks in frame construction in proper order, frame construction includes splint one and splint two, splint one and splint two are located the two electric core outsides in the outside respectively, and in the initialization process, through the pressure sensor detection pressure value between splint and the electric core and between electric core and the electric core.
3. The method of determining the SOC of a lithium metal module battery pack according to claim 1, wherein: in step S3, the equation for calculating SOC by terminal voltage is SOC ═ terminal voltage-discharge cutoff voltage)/(charge cutoff voltage-discharge cutoff voltage.
4. A method for predicting the service life of a lithium metal module battery pack is characterized in that: the method comprises the following steps:
c1, in the initialization process, charging the lithium metal module battery from a full discharge state to a full charge state, and recording a corresponding pressure value P when the SOC is 0.8 0.8 And terminal voltage V 0.8 ；
C2, carrying out charge-discharge circulation on the lithium metal module battery, monitoring the terminal voltage of the lithium metal module battery in real time and recording the terminal voltage as V x When V is x ＝V 0.8 In the process, the real-time pressure average value of a plurality of battery cells in the lithium metal module battery is measured and recorded as P x 0.8 When P is x 0.8 ＞1.5*P 0.8 In the process, the lithium metal module battery is degraded and used, and the maximum SOC charge value is set to be 0.8; when P is present x 0.8 ≤1.5*P 0.8 And calculating the residual service life S of the lithium metal module battery, and normally circulating the lithium metal module battery.
5. The method of claim 4, wherein the method comprises: in step C2, the remaining service life S of the lithium metal module battery is calculated by the following formula: s ═ 1.5 × P 0.8 -P x 0.8 )/(P x 0.8 -P x -1 0.8 ) In which P is x 0.8 When the number of cycles is x, SOC is 0.8, and a plurality of lithium metal module batteriesAverage value of cell pressure, P x-1 0.8 When the number of cycles is x-1 and the SOC is 0.8, the average value of the pressures of the plurality of battery cells in the lithium metal module battery is obtained.
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