CN112736309B - Method for solving abnormal K value of power lithium ion reworked battery after capacity division - Google Patents
Method for solving abnormal K value of power lithium ion reworked battery after capacity division Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 40
- 230000002159 abnormal effect Effects 0.000 title claims abstract description 25
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 14
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 14
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 24
- 230000004913 activation Effects 0.000 claims abstract description 5
- 238000007600 charging Methods 0.000 claims description 24
- 238000007599 discharging Methods 0.000 claims description 24
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical group [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 2
- 230000005856 abnormality Effects 0.000 abstract description 3
- 230000014759 maintenance of location Effects 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- 238000010280 constant potential charging Methods 0.000 description 4
- 238000010277 constant-current charging Methods 0.000 description 4
- 230000010287 polarization Effects 0.000 description 4
- 238000012795 verification Methods 0.000 description 4
- 238000010281 constant-current constant-voltage charging Methods 0.000 description 3
- 230000000630 rising effect Effects 0.000 description 3
- 230000003213 activating effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000012797 qualification Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- 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
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- 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
- H01M10/446—Initial charging measures
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Tests Of Electric Status Of Batteries (AREA)
Abstract
The invention discloses a method for solving abnormal K value after capacity division of a power lithium ion reworked battery, which relates to the technical field of lithium ion batteries and comprises the following steps: 1) The formation component data before the reworked battery is put in storage is recorded as initial data; carrying out primary capacity division on the reworked battery according to a 3.0V capacity division process, and standing for T after capacity division 1 Recording voltage value V3, and standing still for T 2 Recording voltage values V4, K 1 ＝(V3‑V4)/T 2 The method comprises the steps of carrying out a first treatment on the surface of the Will K 1 Value of K Standard of Comparing when K 1 The value is not at K Standard of When the battery is in the range, comparing the charge and discharge time and voltage, charge and discharge capacity and charge and discharge platform data of the first capacity division of the reworked battery with initial data of the battery, and analyzing whether the reworked battery is abnormal or not and the activation degree; when no abnormality exists, repeating the capacity-dividing operation to divide the capacity of the reworked battery for the nth time, and comparing related data; when K is n At K Standard of And in the range, integrating the data difference and determining the rework capacity division times. According to the invention, a 3.0V capacity-dividing process is selected, so that the battery cells with abnormal K values can be better screened out.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a method for solving the problem of abnormal K value of a power lithium ion reworked battery after capacity division.
Background
The lithium ion battery is placed in a finished product warehouse for a period of time (more than 6 months) after being produced, and due to the long placement time, the battery can inevitably have abnormal problems such as internal resistance rise, discharge characteristics are in a descending trend, capacity irreversible loss and the like, and serious problems such as large-range (92% -98%) K value abnormality (K < 0) can occur after the capacity separation of a reworking capacity separation process (3.0V). One of the main reasons for the problems is that polarization is large and the material property inside the activated cell is not thorough in the reworking capacity-dividing process, so that the performance and the use of the battery are seriously affected.
Disclosure of Invention
Based on the technical problems in the background technology, the invention provides a method for solving the problem of abnormal K value of a power lithium ion reworked battery after capacity division.
The invention provides a method for solving the problem of abnormal K value after capacity division of a power lithium ion reworked battery, which comprises the following steps:
1) Taking the volume-divided data after formation before storage of the reworked battery as initial data, and recording the initial data as battery formation volume-divided initial data;
2) The reworked batteries which are kept stand in a finished product warehouse for 6-12 months are subjected to primary capacity division according to the capacity division process of the reworked batteries of 3.0V, and are kept stand after capacity division, and the standing time is recorded as T 1 Recording the voltage value V3, standing, and re-timing, wherein the standing time is recorded as T 2 Recording a voltage value V4; calculating the voltage drop K in the unit time of reworked battery 1 Value, K 1 ＝(V3-V4)/T 2 ；
3) K for dividing reworked battery into capacity for the first time 1 Value of K Standard of Comparing 0 < K Standard of Less than or equal to 4mV/d; when K is 1 The value is K Standard of When the volume of the battery is within the range, the reworked battery can be normally used after the first capacity division; when K is 1 The value is not at K Standard of When the battery is in the range, comparing the charge and discharge time and voltage data, charge and discharge capacity data and charge and discharge platform data of the first capacity division of the reworked battery with initial data of the battery, and analyzing whether the reworked battery is abnormal or not and the activation degree;
4) When the reworked battery is judged to be abnormal, repeating the operations of the step 2) and the step 3), carrying out n-th capacity division on the reworked battery by adopting a 3.0V reworked battery capacity division process, and calculating the voltage drop K in unit time after the n-th capacity division of the reworked battery n The value is compared with the charging and discharging time and voltage data, the charging and discharging capacity data and the charging and discharging platform data of the nth capacity division of the reworked battery and the battery formation composition initial data;
5) When K is n At K Standard of And in the range, the difference between the capacity of the reworked battery and the initial data of the capacity of the battery is synthesized, and the number of times of reworking capacity division is determined, so that the reworked battery can be used as a normal battery.
Preferably, the power lithium ion reworked battery is a lithium iron phosphate battery.
Preferably, the battery-formed composition data is obtained according to a 3.2V volumetric process.
Preferably, the 3.0V reworked battery capacity-dividing process comprises the following steps: the reworked battery is charged to 3.65V at constant current of 0.33C to 2.0V,0.45C to 3.65V,0.55C to 2.0V,0.2C to 2.0V, and 0.2C to 3.0V.
Preferably T 1 ＝18-24h，T 2 ＝4-7d。
The beneficial effects are that: the invention provides a method for solving the problem of abnormal K value after capacity division of a power lithium ion reworked battery, which selects a 3.0V capacity division process, and because 3.0V is smaller than a charge-discharge platform, self discharge is larger and more obvious, so that a battery core with abnormal K value can be better screened out, and the best capacity division scheme is determined by combining the difference and correlation between the charge-discharge capacity of the reworked battery core and the battery formation component before warehousing and the corresponding SOC and the charge-discharge platform thereof in the capacity division process. The invention can realize the performance of gradually eliminating polarization and activating the battery cells for more than 6 months, has obvious improvement and lifting effects on a platform for recovering the charge and discharge of the battery cells, further improves the qualification rate and the utilization rate of the reworked battery cells in a high proportion, and simultaneously provides a feasible verification method for solving the problem of abnormal K value of the reworked battery cells.
Drawings
FIG. 1 is a graph of charge-discharge time versus voltage for a battery formed component in accordance with the present invention;
FIG. 2 is a graph of charge-discharge time versus voltage for a first capacity division of a reworked battery according to the present invention;
FIG. 3 is a graph of charge-discharge time versus voltage for a second partial capacity of a reworked battery according to the present invention;
FIG. 4 is a graph of charge-discharge time versus voltage for a third partial capacity of a reworked battery according to the present invention;
fig. 5 is a graph of charge-discharge time versus voltage for the fifth capacity division of the reworked battery according to the present invention.
Detailed Description
The technical scheme of the invention is described in detail through specific embodiments.
Example 1 reworked cell number: 480 only
1. And (3) carrying out primary capacity division on the reworked batteries which are kept stand in the finished product warehouse for 6-10 months according to a 3.0V capacity division process: constant current and constant voltage of 0.33C are discharged to 2.0V, constant current and constant voltage of 0.45C are charged to 3.65V, constant current and constant voltage of 0.55C are discharged to 2.0V, constant current and constant voltage of 0.2C are discharged to 2.0V, and constant current and constant voltage of 0.2C are charged to 3.0V (charging to 5.1% SOC is stopped).
2. After the capacity division is finished, standing for 18-24 hours, and then confirming a voltage value, wherein the voltage value is defined as V3, and the average value of the detected V3 is 2992mV; then the cell is kept stand for 7 days, and then the voltage value is confirmed, wherein the voltage value is defined as V4, and the average value of the detected V4 is 2.995mV; calculating the voltage drop K value in the unit time of the reworked battery, wherein K= (V3-V4)/7, and the K value of the first capacity of the reworked battery is recorded as K 1 ，K 1 The average value was-0.4 mV/d. The purpose of calculating the K value is to verify whether the reworked cell activated by the capacitive activation meets the voltage drop (0 < K) of the normal cell within 7 days Standard of Less than or equal to 4 mV/d), and the K value is an index for measuring the self-discharge rate of the lithium battery. K (K) 1 ＜K Standard of The reworked battery can not be used as a normal battery after one-time capacity division.
3. The method comprises the steps of finding out capacity-dividing data after formation before storage of reworked batteries as initial battery data;
4. and comparing the charge and discharge time and voltage data of the first capacity division of the reworked battery with the initial data of the capacity division of the battery formation. And respectively drawing a charge-discharge time-voltage curve graph of the first capacity division and the battery formation component of the reworked battery by taking the charge-discharge time as a Y axis and the voltage as an X axis. In this embodiment, 10 reworked batteries are selected randomly for comparison, graphs are respectively shown in fig. 1 and fig. 2, the data difference of voltage data in each stage of charge and discharge is found, whether the voltage data of the normal battery cell and the capacity of the reworked battery cell have great fluctuation and difference is analyzed, and whether the reworked battery cell can be used as the normal battery cell is evaluated. The fluctuation trend of the graph is analyzed and compared to find that the voltage data curves of the first capacity division and the battery formation component of the reworked battery have no obvious difference, so that the reworked battery core has no abnormality.
5. And comparing the capacity data in the first capacity-dividing charge and discharge process of the reworked battery with the initial data of the battery formation capacity-dividing, so as to analyze the recovery rate and the retention rate of the corresponding capacity of the reworked battery after the reworked battery is activated by capacity division. Capacity data of battery formation component capacity: constant flow at 0.33C to 2.0V, capacity average 811.5mah; constant current and constant voltage of 0.45C are charged to 3.65V, and the capacity average value 32206mah; constant flow 0.55C to 2.0V, capacity average 31162mah; constant flow of 0.2C to 2.0V, capacity mean 835mah; constant current and constant voltage of 0.2C are charged to 3.2V, and the capacity average value is 1586mah; capacity data of the first capacity division of the reworked battery: constant flow at 0.33C to 2.0V, capacity average 5256mah; constant current and constant voltage of 0.45C are charged to 3.65V, and the capacity average value is 29875mah; constant flow at 0.55C to 2.0V, capacity average 29798mah; constant flow of 0.2C to 2.0V, capacity average 158mah; constant current and constant voltage of 0.2C are charged to 3.0V, and the capacity average value is 567mah. The capacity recovery rate of the reworked battery core is 91% and the retention rate is 95% through calculation.
The SOC corresponding to the capacity division is found out for comparison, and the purpose is to analyze the state of the electric quantity of the reworked battery core after capacity division activation after charge and discharge. SOC data of battery pack components: constant current of 0.33C is put to 2.0V, and SOC is 2.6%; constant current and constant voltage of 0.45C are charged to 3.65V, and SOC is 100%; constant current of 0.55C is put to 2.0V, and SOC is 100%; constant current of 0.2C is put to 2.0V, and SOC is 2.7%; constant current and constant voltage of 0.2C are charged to 3.2V, and SOC is 6.3%; SOC data of the first capacity division of the reworked battery: constant current of 0.33C is put to 2.0V, and SOC is 17.6%; constant current and constant voltage of 0.45C is charged to 3.65V, and SOC is 92%; constant current of 0.55C is put to 2.0V, and SOC is 95%; constant current of 0.2C is put to 2.0V, and SOC is 0.5%; constant current and constant voltage of 0.2C are charged to 3.0V, and SOC is 1.9%. Through comparison of SOC, the battery core has a tendency of low charging and discharging after the reworking battery is subjected to capacity division for the first time.
6. The method is characterized in that the first capacity-dividing charge and discharge platform data of the reworked battery is compared with the initial data of battery formation components, and the purpose is to find out the numerical difference between the reworked battery cell and normal battery cell charge and discharge to analyze the state of the battery cell. The battery is formed into a component: 0.45C constant current and constant voltage charging platform 3446mV,0.55C constant current to 2.0V discharging platform 3120mV; reworked batteries are subjected to capacity division for the first time: 0.45C constant current constant voltage charging platform 3403mV,0.55C constant current to 2.0V discharging platform 3167mV. Comparison results: the charging and discharging platform of the reworked battery is slightly lower after the first capacity division.
Example 2 reworked cell number: 480 only
1. Again according to the 3.0V capacity-dividing process: the second capacity division was performed with constant current and constant voltage of 0.33C to 2.0V, constant current and constant voltage of 0.45C to 3.65V, constant current and constant voltage of 0.55C to 2.0V, constant current and constant voltage of 0.2C to 3.0V (5.1% soc termination).
2. After the capacity division is finished, standing for 18-24 hours, and then confirming a voltage value, wherein the V3 average value is 2994.3mV; then standing the battery cell for 7 days, and then, confirming that the V4 average value is 2993.2 by the voltage value; the K value of the secondary capacity of the reworked battery is recorded as K 2 Calculated K 2 Average value: -0.50mV/d.
3. And comparing the charge and discharge time and voltage data of the secondary capacity division of the reworked battery with the initial data of the battery formation capacity division, and drawing a charge and discharge time-voltage curve chart. By comparing fig. 1-3, it is found that the voltage data curves of the second capacity division and the battery formation component of the reworked battery are not obviously different, which indicates that the reworked battery core is not abnormal.
4. And comparing the second capacity-dividing charge-discharge capacity data of the reworked battery with the initial data of the battery formation components. The battery is formed into a component: constant flow at 0.33C to 2.0V, capacity average 811.5mah; constant current and constant voltage of 0.45C are charged to 3.65V, and the capacity average value 32206mah; constant flow 0.55C to 2.0V, capacity average 31162mah; constant flow of 0.2C to 2.0V, capacity mean 835mah; constant current and constant voltage of 0.2C are charged to 3.0V, and the capacity average value is 1586mah; and (3) carrying out secondary capacity division on the reworked battery: constant flow of 0.33C to 2.0V, capacity average 691mah; constant current and constant voltage of 0.45C are charged to 3.65V, the capacity average 3064mah, constant current of 0.55C is discharged to 2.0V, and the capacity average 30557 mah; constant flow of 0.2C to 2.0V, capacity average 127mah; constant current and constant voltage of 0.2C are charged to 3.0V, and the capacity average value is 566mah. The reworked battery core capacity recovery rate is 91.6 percent through calculation; the retention rate was 97%;
finding out the SOC corresponding to the capacity for comparison: and (3) carrying out secondary capacity division on the reworked battery: constant current of 0.33C is put to 2.0V SOC 2.3%; constant current and constant voltage of 0.45C are charged to 3.65V SOC100%, and constant current of 0.55C is discharged to 2.0V SOC100%; constant current of 0.2C is discharged to 0.42% of SOC of 2.0V; the constant current and the constant voltage of 0.2C are charged to 3.0V SOC 1.9 percent. Comparison results: the battery cell still has the tendency of being low and low after the secondary rework capacity division.
5. Comparing the charge and discharge platforms: and (3) carrying out secondary capacity division on the reworked battery: 0.45C constant current constant voltage charging platform 3407mV,0.55C constant current to 2.0V discharging platform 3170mV. Comparison results: the charging and discharging platform has a rising trend from the first reworking to the second reworking for separating capacity, and rises by 2-4mV.
Example 3 reworked cell number: 480 only
1. Again according to the 3.0V capacity-dividing process: and the third capacity division is carried out by constant-current discharging of 0.33C to 2.0V, constant-current and constant-voltage charging of 0.45C to 3.65V, constant-current discharging of 0.55C to 2.0V, constant-current discharging of 0.2C to 2.0V and constant-current and constant-voltage charging of 0.2C to 3.0V (charging to 5.1 percent of SOC termination).
2. After the capacity division is finished, standing for 18-24 hours, confirming the voltage value, wherein the V3 average value is 2995mV, and then, after the battery cell stands for 7 days, confirming the voltage value, wherein the V4 average value is 2992mV; the K value of the third capacity division of the reworked battery is recorded as K 3 Calculated K 3 The value was 0.42mV/d, K was changed from a negative value to a positive value.
3. And comparing the charge and discharge time and voltage data of the third capacity division of the reworked battery with the initial data of the battery formation capacity division, and drawing a charge and discharge time-voltage curve chart. By comparing fig. 1-4, it is found that the voltage data curves of the third capacity division and the battery formation component of the reworked battery are not obviously different, which indicates that the reworked battery core is not abnormal.
4. And comparing the data of the third capacity-dividing charge-discharge capacity of the reworked battery with the initial data of the battery formation components. And (3) carrying out third capacity division on the reworked battery: constant flow of 0.33C to 2.0V, volume average 6611mah; constant current and constant voltage of 0.45C are charged to 3.65V, and the capacity average value is 32359mah; constant flow at 0.55C to 2.0V, capacity average 31914mah; constant flow of 0.2C to 2.0V, capacity average 307mah; constant current and constant voltage of 0.2C are charged to 3.0V, and the capacity average value is 526mah. The calculated recovery rate of the capacity of the battery core after the third capacity division of the reworked battery is 97.6 percent; the retention was 99.6%. Comparison results: in the third capacity division process of the reworked battery, the battery core has a tendency that the charging amount is increased from 0.2C current, and the discharging amount is decreased from 0.2C current.
And (5) corresponding SOC comparison. And (3) carrying out third capacity division on the reworked battery: constant current of 0.33C is discharged to 2.0V SOC 20.7%; constant current and constant voltage of 0.45C are charged to 3.65V SOC 99%, and constant current of 0.55C is discharged to 2.0V SOC 98.6%; constant current of 0.2C is discharged to 0.96% of SOC of 2.0V; the constant current and the constant voltage of 0.2C are charged to 3.0V SOC 1.65 percent. Comparison results: the battery cell still has the tendency of high and low charging after the reworked battery is subjected to capacity division for the third time.
4. Comparing the charge-discharge platform for the third capacity division of the reworked battery with the battery formation component: 0.45C constant current constant voltage charging platform 3433mV,0.55C constant current discharge platform 3168mV. Comparison results: the charging platform has a rising trend after the secondary capacity division to the third capacity division of the reworked battery, and the discharging platform descends by 1.8mV.
Example 4 reworked cell number: 480 only
1. According to the 3.0V capacity-dividing process: constant current and constant voltage of 0.33C are discharged to 2.0V, constant current and constant voltage of 0.45C are charged to 3.65V, constant current and constant voltage of 0.55C are discharged to 2.0V, constant current and constant voltage of 0.2C are charged to 3.0V (charging to 5.1 percent of SOC is stopped), and the continuous re-capacity is realized for 2 weeks.
2. After the capacity division is finished, standing for 18-24 hours, and then confirming a voltage value, wherein the V3 average value is 2996mV; after the battery cell is kept stand for 7 days, the voltage value is confirmed to be 2992mV as the average value of V4, and the fifth capacity-dividing K of the reworked battery is obtained through calculation 5 A value of 0.57mV/d; positive values.
3. Comparing the charge and discharge time and voltage data of the fifth capacity division of the reworked battery with the curve of the corresponding original data; by comparing fig. 1-5, it is found that the fifth capacity division of the reworked battery and the voltage data curves of the first, second and third capacity division and the battery formation component of the reworked battery are not obviously different, which indicates that the reworked battery core is not abnormal.
4. And comparing the capacity data of the reworked battery in the fifth capacity-dividing charging and discharging process with the initial data of the battery-formed components. And (3) carrying out rework capacity division for the fifth time: constant flow at 0.33C to 2.0V, capacity average 6721mah; constant current and constant voltage of 0.45C are charged to 3.65V, the volume average value 313 mah, and constant current of 0.55C is discharged to 2.0V, the volume average value 31030mah; constant flow of 0.2C to 2.0V, capacity average 315mah; constant current and constant voltage of 0.2C are charged to 3.0V, and the capacity average value is 593mah. The battery cell capacity recovery rate of the fifth reworking is 98.2% through calculation; the retention was 99.5%.
Comparing the corresponding SOC; and (3) carrying out rework capacity division for the fifth time: constant current of 0.33C was put to 2.0V SOC 21%; constant current and constant voltage of 0.45C are charged to 3.65V SOC 99%, and constant current of 0.55C is discharged to 2.0V SOC 98.6%; constant current of 0.2C is put to 2.0V SOC 1.0%; constant current and constant voltage of 0.2C are charged to 1.9% of 3.0V SOC;
5. the charge-discharge plateau is compared with the previous data. And (3) carrying out rework capacity division for the fifth time: 0.45C constant-current and constant-voltage charging platform 3445mV, and 0.55C constant-current discharging platform 3172mV; comparison results: the charging and discharging platforms have rising trend after the secondary to the fifth capacity division of the reworked battery.
In summary, for the treatment of abnormal K value after capacity division of reworked battery cells (especially standing for 6 months to more than 12 months), a series of verification shows that: 1. the first step of the capacity-dividing process needs to discharge with small current of 0.25-0.33C, the middle charge and discharge needs to charge and discharge with current of 0.4-0.55C, and the last two steps of charging and charging are finished by the small current (0.02-0.01C) which is set; 2. aiming at the situation that a period of standing (7-14 days) is needed from the first capacity division to the third capacity division after the battery core is activated in the process of reworking and capacity division of a battery core with longer standing time; 3. in the multiple capacity division process, abnormal cells, SOC and a charging platform are screened according to charge and discharge capacity to judge the state of the cells, and the number of times of capacity division is increased to activate the state of the reworked cells. The key index is that the final small current (0.2C) discharging and charging electric quantity SOC of the last 2 steps of the process is in the interval of 0.92-2.3 percent; the charging and discharging platform (the charging platform is 3430-3440mV and the discharging platform is 3160-3170 mV) can effectively solve and improve the problem of abnormal K value of the reworked battery core and maximize the normal use rate of the reworked battery core under the condition that the charging platform is 3430-3440mV and the discharging platform is 3160-3170 mV.
In the embodiments 1-4 of the invention, the K value of the reworked battery is abnormally changed from a negative value to a positive value after 3 weeks of capacity division, and the reworked battery core is greatly recovered and improved in the capacity division process for eliminating polarization and activating the battery core; the K value has recovered to the normal state. According to the battery formation composition data in the embodiments 1-4 and the comparison of the charge-discharge capacity, the SOC and the charge-discharge platform data of the reworked battery core in the capacity division process, the values of the charge-discharge capacity corresponding to the SOC and the charge-discharge platform in each stage gradually approaching to the charge-discharge platform of the normal battery core can be obviously seen from the data, so that the superiority of the verification method of the patent is fully illustrated;
according to the embodiment of the patent, polarization of the battery cells can be gradually eliminated for more than 6 months, the performance of the battery cells is activated, the platform for recovering the charge and discharge of the battery cells is obviously improved, the lifting effect and the high-proportion lifting of the qualification rate and the utilization rate of the reworked battery cells are achieved, and meanwhile, a feasible verification method for solving the problem of abnormal K value of the reworked battery cells is also provided.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should make equivalent substitutions or modifications according to the technical scheme of the present invention and the inventive concept thereof, and should be covered by the scope of the present invention.
Claims (2)
1. The method for solving the problem of abnormal K value of the power lithium ion reworked battery after capacity division is characterized by comprising the following steps:
1) Taking the volume-divided data after formation before storage of the reworked battery as initial data, and recording the initial data as battery formation volume-divided initial data;
2) The reworked batteries which are kept stand in a finished product warehouse for 6-12 months are subjected to primary capacity division according to the capacity division process of the reworked batteries of 3.0V, and are kept stand after capacity division, and the standing time is recorded as T 1 Recording the voltage value V3, standing, and re-timing, wherein the standing time is recorded as T 2 Recording a voltage value V4; calculating the voltage drop K in the unit time of reworked battery 1 Value, K 1 =（V3-V4）/T 2 ；
3) K for dividing reworked battery into capacity for the first time 1 Value of K Standard of Comparing 0 < K Standard of Less than or equal to 4 mV/day; when K is 1 The value is K Standard of When the volume of the battery is within the range, the reworked battery can be normally used after the first capacity division; when K is 1 The value is not at K Standard of When the battery is in the range, comparing the charge and discharge time and voltage data, charge and discharge capacity data and charge and discharge platform data of the first capacity division of the reworked battery with initial data of the battery, and analyzing whether the reworked battery is abnormal or not and the activation degree;
4) When the reworked battery is judged to be abnormal, repeating the operations of the step 2) and the step 3), carrying out n-th capacity division on the reworked battery by adopting a 3.0V reworked battery capacity division process, wherein n is more than or equal to 2, and calculating the unit time of the reworked battery after n-th capacity divisionVoltage drop K n The value is compared with the charging and discharging time and voltage data, the charging and discharging capacity data and the charging and discharging platform data of the nth capacity division of the reworked battery and the battery formation composition initial data;
5) When K is n At K Standard of In the range, the difference between the capacity of the reworked battery and the initial data of the capacity of the battery is synthesized, and the number of times of reworking capacity division is determined, so that the reworked battery can be used as a normal battery;
the 3.0V reworked battery capacity-dividing process comprises the following steps: the reworked battery is charged to 3.65V at constant current and constant voltage of 0.33C to 2.0V, charged to 2.65V at constant current and constant voltage of 0.45C, charged to 2.0V at constant current and constant voltage of 0.2C to 2.0V, and charged to 3.0V at constant current and constant voltage of 0.2C;
T 1 =18-24h，T 2 =4-7 days.
2. The method for solving the problem of abnormal K value after capacity division of the power lithium ion reworked battery according to claim 1, wherein the power lithium ion reworked battery is a lithium iron phosphate battery.
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