DE112020005205T5 - Procedure for quick grouping and repair of dead batteries - Google Patents

Abstract

The present application relates to the technical field of recycling and reusing lithium-ion batteries and discloses a method for rapid grouping and repair of spent batteries. With the method of incomplete charging and discharging, the used batteries are quickly grouped using the key voltage value, then one or more used batteries are selected from each group to grasp their actual capacity, and according to the actual capacity, the repairable used battery group is sorted out; the spent batteries are discharged to their cut-off voltage; the discarded batteries are filled with electrolytes of different weights and sealed, at the end the discarded batteries are activated, after activation, they are grouped again according to the discharge capacity and charge transfer impedance of the batteries, and the activated discarded batteries in the same group form a battery group that reuses becomes. The capacity of the battery repaired by the method of the present invention reaches the level of the power battery in service, and the battery pack formed by the method of the present invention has good recycling performance.

Description

TECHNICAL AREA

The present application relates to the technical field of lithium-ion battery repair, in particular to a method for rapid grouping and repair of spent batteries.

STATE OF THE ART

The electric vehicles have been popular for several years, which has led to a large number of lithium-ion batteries with performance drop and insufficient capacity due to long-term use.

The loss of battery capacity is mainly caused by the increase in impedance caused by the loss of lithium ions and the side reactions caused by the consumption of the electrolyte.

The lost lithium ions mainly include the lithium consumed by the formation of the SEI film during the formation process of the battery, the lithium consumed by the side reactions of the electrolyte, the lithium dendrites generated by the lithium on the negative electrode, and the lack of vacancies for ion acceptance caused by the structural change of the active material caused lithium loss. The irreversible loss of capacity caused by these lithium losses is irreparable.

The electrolyte provides the medium for the conduction of lithium ions between the positive and negative electrodes. During charging and discharging, the electrolyte reacts with the pole plates, the electrolyte is lost, and the resulting concentration polarization impedance and charge transfer impedance affect the battery capacity drop , and the capacity of the lithium battery can be restored by refilling the electrolyte.

In the prior art, the used batteries are first fully charged and discharged to obtain the actual capacity parameters of the used batteries, and repairable used batteries are selected according to the actual capacity, then the repairable used batteries are divided into classes, and a corresponding weight on Electrolyte will be poured into the used batteries in each class. This method requires full charging of all the dead batteries, and charging and discharging all the dead batteries consumes a large amount of power.

CONTENT OF THE PRESENT INVENTION

The present invention aims to provide a method for quickly grouping and repairing spent batteries, which can save power consumption and reduce production costs.

• Schnellgruppierungsverfahren für ausgediente Batterien, umfassend die folgenden Schritte:
  • Stehenlassen der auf die Abschaltspannung entladenen ausgedienten Batterie bei Raumtemperatur für eine erste festgelegte Zeitdauer, Messen der Spannung der ausgedienten Batterie zu diesem Zeitpunkt und Aufzeichnen dieser als eine erste Spannung;
  • Laden der ausgedienten Batterie gemäß dem in der ursprünglichen Fabrik der ausgedienten Batterie eingestellten Ladeverfahren auf eine Sollkapazität eines voreingestellten Prozentsatzes der Nennkapazität, Messen der Spannung der ausgedienten Batterie zu diesem Zeitpunkt und Aufzeichnen dieser als eine zweite Spannung;
  • Stehenlassen der mit der Sollkapazität aufgeladenen ausgedienten Batterie bei Raumtemperatur für eine zweite festgelegte Zeitdauer, Messen der Spannung der ausgedienten Batterie zu diesem Zeitpunkt und Aufzeichnen dieser als eine dritte Spannung;
  • Einstellen einer ersten Beurteilungsbedingung entsprechend der ersten Spannung, Einstellen einer zweiten Beurteilungsbedingung entsprechend der zweiten Spannung und Einstellen einer dritten Beurteilungsbedingung entsprechend der dritten Spannung, Beurteilen der ausgedienten Batterie nacheinander entsprechend der ersten Beurteilungsbedingung, der zweiten Beurteilungsbedingung und der dritten Beurteilungsbedingung;
  • Vervollständigen der obigen Beurteilungsschritte für mehrere ausgediente Batterien, um eine erste Vorauswahlgruppe, eine zweite Vorauswahlgruppe und eine dritte Vorauswahlgruppe zu bilden; und
  • Einteilen der ausgedienten Batterien, die gleichzeitig in die erste Vorauswahlgruppe, die zweite Vorauswahlgruppe und die dritte Vorauswahlgruppe ausgewählt werden, in eine Gruppe.

To achieve the above objective, the present invention uses the following technical solution:

• Quick grouping procedure for spent batteries, comprising the following steps:
  • leaving the spent battery discharged to the shutdown voltage at room temperature for a first predetermined period of time, measuring the voltage of the spent battery at that time and recording it as a first voltage;
  • charging the spent battery according to the charging method set at the original factory of the spent battery to a target capacity of a preset percentage of the rated capacity, measuring the voltage of the spent battery at that time and recording it as a second voltage;
  • allowing the used battery charged to the target capacity to stand at room temperature for a second predetermined period of time, measuring the voltage of the used battery at that time and recording it as a third voltage;
  • setting a first judgment condition corresponding to the first tension, setting a second judgment condition corresponding to the second tension, and setting a third judgment dividing condition according to the third voltage, judging the dead battery sequentially according to the first judging condition, the second judging condition, and the third judging condition;
  • completing the above judging steps for a plurality of dead batteries to form a first pre-selection group, a second pre-selection group and a third pre-selection group; and
  • dividing the spent batteries, which are simultaneously selected into the first pre-selection group, the second pre-selection group and the third pre-selection group, into a group.

• Stehenlassen der auf die Abschaltspannung entladenen ausgedienten Batterie bei Raumtemperatur für eine erste festgelegte Zeitdauer, Messen der Spannung der ausgedienten Batterie zu diesem Zeitpunkt und Aufzeichnen dieser als eine erste Spannung;

A dead battery repair procedure comprising the following steps:

• leaving the spent battery discharged to the shutdown voltage at room temperature for a first predetermined period of time, measuring the voltage of the spent battery at that time and recording it as a first voltage;

charging the spent battery according to the charging method set at the original factory of the spent battery to a target capacity of a preset percentage of the rated capacity, measuring the voltage of the spent battery at that time and recording it as a second voltage;

allowing the used battery charged to the target capacity to stand at room temperature for a second predetermined period of time, measuring the voltage of the used battery at that time and recording it as a third voltage;

setting a first judging condition according to the first voltage, setting a second judging condition according to the second voltage, and setting a third judging condition according to the third voltage, judging the dead battery sequentially according to the first judging condition, the second judging condition, and the third judging condition;

completing the above judging steps for a plurality of dead batteries to form a first pre-selection group, a second pre-selection group and a third pre-selection group;

dividing the used batteries, which are simultaneously selected into the first pre-selection group, the second pre-selection group, and the third pre-selection group, into a group;

adjusting the first judging condition, the second judging condition, and the third judging condition and grouping all the dead batteries to obtain a plurality of dead battery groups;

selecting one or more dead batteries from each dead battery group and detecting the actual capacity of the selected dead battery;

sorting out the repairable used battery groups according to the actual capacity of the selected used batteries;

discharging the respective spent batteries in each repairable spent battery bank to their shutdown voltage;

filling an appropriate weight of electrolyte into respective dead batteries in each repairable dead battery group and then sealing; wherein an equal weight of electrolyte is filled in the respective dead batteries in each repairable dead battery group; and

Charging and discharging the used batteries filled with the electrolyte for activation.

• in der vorliegenden Erfindung werden drei Schlüsselspannungswerte, die die Leistung der Batterie charakterisieren können, zuerst erhalten, indem die Batterie nicht vollständig entladen wird, und durch Einstellen der Beurteilungsbedingungen wird die schnelle Gruppierung aller ausgedienten Batterien realisiert, und die elektrischen Eigenschaften der ausgedienten Batterien derselben Gruppe sind ähnlich, was die Testzeit verkürzt und den Energieverbrauch einspart.

The following advantages are achieved by implementing the exemplary embodiment of the present application:

• in the present invention, three key voltage values that can characterize the performance of the battery are obtained first by not fully discharging the battery and by on By setting the judgment conditions, the quick grouping of all the spent batteries is realized, and the electrical characteristics of the spent batteries of the same group are similar, which shortens the test time and saves the energy consumption.

Since the electrical characteristics of the same group of the used batteries are similar, one or more batteries in each group is selected from the used batteries to fully charge and discharge them and measure their actual capacity, and the actual capacity can determine the capacity level of the same represent group of the used batteries, according to the measured actual capacity, the repairable used battery groups are selected, and then a corresponding weight on the electrolyte is poured into each repairable used battery group according to the measured actual capacity, so that the used batteries are brought to the level of operational power batteries can be restored. Since only one or more batteries in each group are fully charged and fully discharged, the number of fully charged batteries is greatly reduced, greatly reducing power consumption and saving production costs.

Since the internal electrolyte of the repaired battery differs from that of the fresh battery, the present invention sorts and rearranges the repaired dead batteries according to the two aspects of battery capacity and battery charge transfer impedance, and its consistency is compared to sorting according to capacity and internal resistance better, improving the recycling performance of the battery group.

The rapid grouping and repairing method according to the present invention is more suitable for batch repair and automatic operation to improve production efficiency.

character list

• 1 zeigt ein Änderungsbeziehungsdiagramm zwischen der Spannung und der Kapazität der Lithiumbatterie während des normalen Ladens und Entladens.
• 2 zeigt ein Vergleichsdiagramm der Entladungskurven einer ausgedienten LiFePO4/Graphit-Batterie mit einer Nennkapazität von 150 Ah vor und nach dem Nachfüllen des Elektrolyten und dem Aktivieren in einem Ausführungsbeispiel der vorliegenden Erfindung.
• 3 zeigt ein Vergleichsdiagramm der Zyklusleistung bei normaler Temperatur von zwei Batteriegruppen, die durch Anwenden unterschiedlicher Gruppierungsverfahren in einem Ausführungsbeispiel der vorliegenden Erfindung erhalten werden.

In order to explain the technical solution in the embodiments of the present application or the prior art more clearly, the figures to be used in the explanation of the embodiment or the prior art are briefly introduced below. Obviously, the figures below only show some embodiments of the present application. Those of ordinary skill in the art can obtain other figures based on these figures without having any creative work.

• 1 FIG. 12 shows a change-relationship diagram between the voltage and the capacity of the lithium battery during normal charging and discharging.
• 2 FIG. 12 shows a comparative diagram of the discharge curves of a used LiFePO4/graphite battery with a nominal capacity of 150 Ah before and after topping up the electrolyte and activating in an embodiment of the present invention.
• 3 FIG. 12 shows a comparison chart of the normal temperature cycle performance of two battery groups obtained by applying different grouping methods in an embodiment of the present invention.

DETAILED DESCRIPTION

In connection with figures in the embodiment of the present application, the technical solutions in the embodiment of the present application are explained clearly and fully in the following. Obviously, the illustrated embodiments do not represent all embodiments, but only part of embodiments of the present application. All other embodiments obtained by those skilled in the art on the basis of the embodiments in the present application without creative works are intended to be considered within the scope of protection of the present application.

The invention consists in repairing the battery, whose capacity is dampened by the loss of electrolyte, so that it can reach the level of the performance battery in service, and re-sorting and pairing it so that it can be further used on the battery vehicle and recycled.

In the prior art, the selection of a repairable end-of-life battery from the end-of-life batteries typically consists of fully charging the battery and then leaving it at 5 days or more Leave at room temperature to test the voltage and get the voltage drop and actual capacity data, and then discharge the battery to the cut-off voltage with a constant current to get the actual capacity of the battery. This sorting process takes a long time, and at the same time, full charging also consumes a lot of energy resources. Internal resistance, voltage, capacity, and self-discharge rate are four parameters that reflect battery consistency, and they represent the key control points for battery sorting. As in 1 1, it is a charge-discharge curve diagram of a lithium battery, with the ordinate being the voltage and the abscissa being the cumulative charge and discharge capacity. Namely, the cumulative value of charging or discharging capacity with the passage of time when charging or discharging. If the abscissa is replaced by time, it can be understood as a change in cell voltage with the lapse of time during charging or discharging. It can be seen that in a single charge or discharge event, the voltage value and capacitance value are in a one-to-one correspondence, which is also the fundamental basis in the present patent for using voltage to characterize capacitance.

In this embodiment, by detecting the key voltage parameters of each battery, a plurality of judgment conditions related to the internal resistance, voltage, capacity and self-discharge rate, which reflect the battery consistency, are set to obtain the characterization quantity, which can reflect the battery capacity and the voltage difference, without the Fully charge and discharge battery, reducing test time and test energy consumption while improving reconstituted battery performance and degree of compliance.

The lithium battery quick sorting method in this embodiment is aimed at the discarded batteries of the same model and lot produced by the same manufacturer. Assuming end-of-life batteries of the same model and lot, the specific voltage conditions are linked to other battery performance parameters. In different types of batteries, the correlation of performance parameters is not the same, and different types of batteries have different shapes, so there is no recombination between different models and different batches of spent batteries.

• (1) Stehenlassen der auf die Abschaltspannung entladenen ausgedienten Batterie bei Raumtemperatur für eine erste festgelegte Zeitdauer, Messen der Spannung der ausgedienten Batterie zu diesem Zeitpunkt und Aufzeichnen dieser als eine erste Spannung. Die erste Spannung kann den Polarisationsinnenwiderstand der Batterie widerspiegeln.

The present invention provides a dead battery fast grouping method that does not fully charge and discharge the batteries to shorten the sorting time, improve the sorting efficiency and save power consumption at the same time, and the method includes the following steps:

• (1) Allowing the spent battery discharged to the cut-off voltage to stand at room temperature for a first predetermined period of time, measuring the voltage of the spent battery at that time and recording it as a first voltage. The first voltage may reflect the internal polarization resistance of the battery.

In this step, the spent battery is discharged to the shutdown voltage according to the discharge method set in the original factory of the spent battery.

In this step, the first specified period of time is the time that the battery voltage is fully equalized, and the fully equalized time is different for batteries made of different materials.

(2) Charge the spent battery according to the charging method set in the original factory of the spent battery to a target capacity of a preset percentage of the rated capacity, measure the voltage of the spent battery at that time and record it as a second voltage. The second voltage may reflect the voltage and capacity of the battery.

In this step, the target capacity can be in the range of 20%-35% of the nominal capacity.

(3) allowing the discharged battery charged to the target capacity to stand at room temperature for a second predetermined period of time, measuring the discharged battery voltage at that time and recording it as a third voltage; the third voltage can reflect the self-discharge and AC internal resistance of the battery.

In this step, the second specified period of time is the time that the battery voltage is fully equalized, and the fully equalized time is different for batteries made of different materials.

(4) setting a first judging condition according to the first voltage, setting a second judging condition according to the second voltage, and setting a third judging condition according to the third voltage, judging the dead battery sequentially according to the first judging condition, the second judging condition, and the third judging condition; Complete the above assessment steps for multiple dead batteries to form a first pre-selection group, a second pre-selection group, and a third pre-selection group.

In this step, referring to Table 1 taking 22 batteries as an example, specifically, the first voltage, the second voltage, and the third voltage of each dead battery are counted.

The first voltage difference value, the second voltage difference value, and the third voltage difference value of each dead battery relative to the first dead battery are counted.

Setting a first threshold, a second threshold and a third threshold, wherein the first threshold is the voltage difference threshold of the first voltage, the second threshold is the voltage difference threshold of the second voltage, and the third threshold is the voltage difference threshold of the third voltage. It is assumed that the first threshold is ≦50 mV, the second threshold is ≦50 mV, and the third threshold is ≦30 mV.

The counted dead batteries are sorted according to the voltage difference threshold of the first voltage to form a first pre-selection group, and batteries Nos. 1 to 6 are the first pre-selection group.

The counted dead batteries are sorted according to the voltage difference threshold of the second voltage to form a second pre-selection group, and batteries Nos. 1 to 6 are the second pre-selection group.

The counted dead batteries are sorted according to the voltage difference threshold of the third voltage to form a third preselection group, and batteries Nos. 1 to 8 are the third preselection group.

(5) selecting the dead batteries, which are simultaneously selected into the first pre-selection group, the second pre-selection group and the third pre-selection group, into one group, namely, batteries Nos. 1 to 6 are the first group;

adjusting the first judging condition, the second judging condition, and the third judging condition, and grouping all the spent batteries to obtain a plurality of spent battery groups.

Setting the first threshold ≤ 100mV, the second threshold ≤ 100mV, and the third threshold ≤ 60mV, then No. 7 to 11 batteries are the second group, and so on, all the batteries can be divided into multiple battery groups the electrical characteristics of the batteries in each battery group are similar.

The discarded battery is sorted according to the first threshold, the second threshold and the third threshold, realizing the purpose of sorting out and reorganizing the discarded battery according to the four key control points - the internal resistance, voltage, capacity and self-discharge. Table 1: Key voltage and voltage differential statistics for end-of-life batteries battery number U1 (V) ΔU1 (mV) U2 (V) ΔU2 (mV) U3 (V) ΔU3 (mV) 1 2,903 0 3,551 0 3.36 0 2 2,914 11 3.56 9 3.37 10 3 2,916 13 3,569 18 3.37 10 4 2,927 24 3,594 43 3,376 16 5 2,935 32 3,596 45 3,377 17 6 2,942 39 3.6 49 3,379 19 7 2,979 76 3,606 55 3,387 27 8th 2.99 87 3,609 58 3.39 30 9 2,991 88 3,609 58 3.41 50 10 2,994 91 3,611 60 3.411 51 11 3 97 3,612 61 3.411 51 12 3.019 116 3,614 63 3,416 56 13 3,023 120 3.62 69 3,418 58 14 3,029 126 3,632 81 3,421 61 15 3.03 127 3,641 90 3,434 74 16 3,035 132 3,642 91 3,436 76 17 3,035 132 3,656 105 3,437 77 18 3,052 149 3.67 119 3,446 86 19 3,058 155 3,697 146 3,447 87 20 3,063 160 3,708 157 3,447 87 21 3,082 179 3,716 165 3,448 88 22 3,092 189 3.74 189 3,448 88

1. (1) Auswählen einer oder mehrere ausgedienten Batterien aus jeder ausgedienten Batteriegruppe und Erfassen der tatsächlichen Kapazität der ausgewählten ausgedienten Batterie;

A dead battery repair procedure is provided below, comprising the following steps:

1. (1) selecting one or more dead batteries from each dead battery group and detecting the actual capacity of the selected dead battery;

Since the electrical characteristics of the batteries in each battery group are similar, the actual capacity of the selected used batteries may represent the actual capacity of the group of used batteries, and preferably 2 to 5 used batteries are selected from each used battery group.

(2) Detecting the actual capacity of the selected used batteries and discarding the repairable used battery groups.

Preferably, the discarded battery whose actual capacity is 60%-80% of the rated capacity is selected for repair, when the actual capacity of the selected discarded batteries is 60%-80% of the rated capacity is the discarded battery group in which the selected discarded Batteries are located, the repairable discarded battery group.

A lithium iron phosphate single battery for electric buses is taken as an example, the rated capacity is 150Ah, and the selected discarded battery, whose actual capacity is in the range of 90Ah-120Ah, is a repairable discarded battery.

In this embodiment, the above-mentioned actual capacity detection method is as follows: perform a charge and discharge cycle for the dead battery according to a certain constant current value, specifically, the constant current value may be 0.2C of the rated capacity, and record its discharge capacity, which is the actual capacity is.

• Berechnen des maximalen Kapazitätsverlusts der ausgewählten ausgedienten Batterie, und der maximale Kapazitätsverlust ist die Differenz zwischen der Nennkapazität und der tatsächlichen Kapazität, die verlorene Batterieleistung wird gemäß dem maximalen Kapazitätsverlust berechnet, um die Masse des Elektrolyten, der für jede ausgediente Batterie in der reparierbaren ausgedienten Batteriegruppe nachgefüllt werden muss, zu berechnen, insbesondere beträgt die tatsächliche Kapazität der aus einer reparierbaren ausgedienten Batteriegruppe ausgewählten ausgedienten Batterien 90 Ah und 100 Ah, die Nennkapazität beträgt 150 Ah, der Kapazitätsverlust beträgt j eweils 60 Ah und 50 Ah, und der maximale Kapazitätsverlust beträgt 60 Ah, und die Masse des Elektrolyten, der für jede ausgediente Batterie in der reparierbaren ausgedienten Batteriegruppe nachgefüllt werden muss, beträgt jeweils 75 g.

(3) Calculate the weight of electrolyte to be placed in each end-of-life battery in each repairable end-of-life battery group, specifically as follows:

• Calculate the maximum capacity loss of the selected end-of-life battery, and the maximum capacity loss is the difference between the rated capacity and the actual capacity, the lost battery power is calculated according to the maximum capacity loss to determine the mass of the electrolyte used for each end-of-life battery in the repairable end-of-life battery group needs to be refilled, specifically, the actual capacity of the used batteries selected from a repairable used battery group is 90Ah and 100Ah, the rated capacity is 150Ah, the capacity loss is 60Ah and 50Ah respectively, and the maximum capacity loss is 60 Ah, and the mass of electrolyte to be replenished for each spent battery in the repairable spent battery group is 75g each.

(4) Discharging the respective spent batteries in each repairable spent battery group to their shutdown voltage to realize full discharge. The internal environment of the battery, including the electrolyte, positive and negative pole plates, spacer plate, etc., is isolated from the external environment. When the battery is charged, the negative electrode lithium material is very active and easily reacts with water and oxygen in the air to release the heat, the heat can cause the electrolyte to reach a high temperature, and the high temperature will cause other negative chain reactions or even cause thermal runaway. Therefore, the battery must be fully discharged to ensure battery safety.

In particular, a certain constant current value is used for discharging to the cut-off voltage, and the cut-off voltage refers to a very low voltage range. Different batteries have different cut-off voltage values in the standard.

(5) Filling of the electrolyte, it is preferable to fill the electrolyte under vacuum condition in order to avoid the reaction between the air and the electrolyte and the influence of the air on the electrolyte. The specific procedure for filling the electrolyte into the discarded battery is as follows: removing the top cover of the discarded battery, cutting off a part of the protective rubber on the battery cover plate to form a rubber hole in an environment where the dew point temperature is lower than or equal to -35 °C, aligning a drill to the rubber hole and piercing the battery cover plate, and aligning the liquid injection nozzle to the rubber hole to start vacuuming, after vacuuming is complete, it will start filling the electrolyte, preferably the electrolyte several times filled, and each time before filling the electrolyte, vacuuming is carried out. Preferably, the degree of vacuum of the vacuum condition is equal to or less than -0.085 MPa.

In the present exemplary embodiment, 75 g of electrolyte are filled into each used battery in a used battery group. The electrolyte is filled three times, first vacuuming to -0.085 MPa, filling 1/3 of the electrolyte to be filled, i.e. 25 g; then vacuuming to -0.085 MPa, filling 1/3 of the electrolyte to be filled, i.e. 25 g; finally vacuuming to -0.085 MPa and filling 1/3 of the electrolyte to be filled, i.e. 25 g.

Sealing is performed after filling of the electrolyte is completed. The respective used batteries of the same group are filled with the same weight of electrolyte.

(6) Charging and discharging the respective spent batteries filled with the electrolyte for activation. The procedure of charging and discharging to activate is as follows: the discarded battery filled with the electrolyte is left to let the electrolyte fully permeate the inside of the battery, the battery is charged with the first constant current up to the upper limit of the battery voltage, and then with the second constant current discharged to the cut-off voltage of the battery. Since the battery has been completely discharged before the electrolyte is filled, the charging current should be as small as possible to better repair the SEI film during the charging process. The first constant current is preferably 0.01 C-0.1 C of the nominal capacity of the used battery. When discharging, to speed up discharging, a larger constant current can be used for discharging, preferably the second constant current is 0.5 C-1 C of the rated capacity of the used battery. Since the electrolyte in the battery flows faster at high temperatures, it is easy to place the battery in a high-temperature environment to allow the filled electrolyte to permeate the inside of the battery quickly. However, if the temperature is too high, the reaction inside the battery will be enhanced, causing adverse effects, for example, the SEI film is easily decomposed at high temperature. To the above two Therefore, to balance aspects, the spent battery filled with the electrolyte is preferably left to stand at 35°C-50°C for 1 day to 5 days. In this embodiment, each discarded battery, after the electrolyte was filled, left for 3 days at 45 degrees and charged with 0.05 C of the rated capacity to 3.45 V and discharged with 0.5 C of the rated capacity to 2 V to the implement activation.

The discarded LiFeP04/graphite single battery is taken as an example, the comparison chart of the discharge curves before and after repair and activation by refilling the electrolyte is shown in 2 shown, and curve B in 2 is the discharge curve of the used battery after the repair of the present invention, the curve A is the discharge curve of the used battery before the repair. Out of 2 it can be seen that the capacity of the spent LiFePO 4 /graphite single battery after the repair by the method of the present invention is remarkably improved than that before the repair.

1. 1. Erfassen der Entladekapazität und der Ladungsübertragungsimpedanz der aktivierten ausgedienten Batterien. In dem spezifischen Ausführungsbeispiel werden die Batterien mit Konstantstrom von 1C der Nennkapazität auf die obere und untere Grenzspannung geladen und entladen, und die Entladekapazität und der DC-Innenwiderstand der jeweiligen ausgedienten Batterien werden aufgezeichnet; die elektrochemische Arbeitsstation testet den AC-Innenwiderstand der jeweiligen ausgedienten Batterien, und der Frequenzbereich beträgt 1000 Hz bis 0,01 Hz, und die Ladungsübertragungsimpedanz wird durch Anpassen mit der ZView2-Simulationssoftware berechnet.

(7) grouping the depleted batteries activated in step (6) to form a battery group and further optimizing the performance of the battery group, specifically comprising the following steps:

1. 1. Detecting the discharge capacity and charge transfer impedance of the activated dead batteries. In the specific embodiment, the batteries are charged and discharged with a constant current from 1C of the rated capacity to the upper and lower limit voltages, and the discharge capacity and the DC internal resistance of the respective spent batteries are recorded; the electrochemical workstation tests the AC internal resistance of the respective spent batteries, and the frequency range is 1000Hz to 0.01Hz, and the charge transfer impedance is calculated by fitting with the ZView2 simulation software.

Here, the information of discharge capacity C, DC internal resistance DC-IR and charge transfer resistance RCt of 20 batteries repaired and activated by filling the electrolyte are shown in Table 2. Table 2: Discharge capacity C, DC internal resistance DC-IR and charge transfer resistance RCt of the repaired and activated batteries battery number C/Ah DC-IR/Ω _RCt /Ω battery number C/Ah DC-IR/Ω _RCt /Ω 1 106.3 0.557 0.473 11 116.5 0.514 0.413 2 106.7 0.591 0.434 12 117.5 0.517 0.375 3 108.4 0.574 0.415 13 117.9 0.526 0.342 4 109 0.554 0.391 14 118.8 0.531 0.356 5 111.1 0.54 0.423 15 118.9 0.533 0.362 6 111.8 0.581 0.386 16 120.1 0.511 0.389 7 111.1 0.531 0.395 17 120.7 0.51 0.341 8th 111.9 0.513 0.382 18 121.3 0.531 0.317 9 114.7 0.589 0.386 19 121.6 0.521 0.324 10 116.3 0.523 0.375 20 121.9 0.519 0.339

2. Classifying the activated dead batteries according to the discharge capacity. Specifically, with the set capacity difference as an interval, the discharge capacity is divided into different classification intervals, and the activated dead batteries are classified according to the classification interval in which the discharge capacity is. The capacity difference is preferably 0-5% of the nominal capacity of the used battery. In this specific embodiment, the above-mentioned 20 batteries are classified according to the capacity difference of 10 Ah, and Nos. 1-4, Nos. 5-15, and Nos. 16-20 are of the same class, respectively.

3. Grouping the spent batteries in the same class according to charge transfer resistance. Specifically, with the charge transfer impedance difference set as the interval, the charge transfer impedance of the discarded batteries is divided into different grouping intervals divides, and the activated dead batteries are grouped according to the grouping interval in which the charge transfer impedance of the dead batteries is. Preferably, the charge transfer impedance difference is 10%-15% of the average charge transfer impedance of activated spent batteries in the same class. In this specific embodiment, in the batteries of the same class, such as batteries #5-15, the average value of the

Charge transfer resistance of the batteries of this class is 0.3814, and 13% of the average value is used as the charge transfer impedance difference, namely 0.05, the batteries are grouped according to the charge transfer impedance difference ΔRCt=0.05, then the batteries with a charge transfer impedance of 0.35-0, 4 one group, and the batteries with a charge transfer impedance of 0.4-0.45 another group, namely, batteries No. 6,7,8,9,10,12,14,15 have a charge transfer impedance in the range of 0, 35-0.4 and are divided into a group, and batteries No. 5, 11 have a charge transfer impedance in the range of 0.35-0.4 and remain. Similarly, battery #1 is left over when batteries #1 through 4 are classified, and battery #16 is left over when batteries #16 through 20 are classified.

After the grouping of the discarded batteries in each class is completed, the remaining discarded batteries in each class are reclassified and grouped according to the above procedure.

In this specific embodiment, the maximum battery capacity difference between the remaining batteries No. 5, 11 and batteries Nos. 2, 3 and 4 is less than the capacity difference standard of 10 Ah, and they are classified into the same class, and batteries 5, 11 and 2 reclassified B. 3.4 batteries, and the maximum charge transfer impedance difference between No. 5, 11 batteries and Nos. 2, 3 and 4 batteries is 0.043, which is smaller than the standard of charge transfer impedance difference ΔRCt = 0.05, therefore, batteries #5, 11 and batteries #2, 3, 4 are divided into one group. The grouping procedure for other batteries is the same as the above procedure.

5. The discarded batteries classified into the same group form a battery group.

From batteries Nos. 6, 7, 8, 9, 10, 12, 14 and 15 divided into a group, 4 batteries are selected to combine them in series and parallel to form a battery group B; No. 1, 2, 3, 4 batteries with similar capacities and internal DC resistances to those of the 4 batteries in battery group B are combined in series and in parallel to form battery group A. Battery group A and battery group B are each tested for cycle performance at normal temperature. The cycle performance test comparison chart is in 3 shown. In 3 curve B is the cycle performance curve of battery group B selected by the grouping method of the present invention, and curve A is the cycle performance curve of battery group A selected using the conventional capacitance and DC internal resistance method. Out of 3 it can be seen that the battery group B selected by the battery grouping method of the present invention is superior to the battery group A selected by the conventional method with the capacity and the DC internal resistance in cycle performance. The battery group obtained by the battery grouping method of the present invention has better consistency.

Claims (20)

A method for quickly grouping spent batteries, characterized in that it comprises the steps of: leaving the spent battery discharged to the cut-off voltage at room temperature for a first predetermined period of time, measuring the voltage of the spent battery at that time and recording it as a first voltage; charging the spent battery according to the charging method set at the original factory of the spent battery to a target capacity of a preset percentage of the rated capacity, measuring the voltage of the spent battery at that time and recording it as a second voltage; allowing the used battery charged to the target capacity to stand at room temperature for a second predetermined period of time, measuring the voltage of the used battery at that time and recording it as a third voltage; setting a first judgment condition according to the first voltage, setting a second judgment condition according to the second voltage, and setting a third judging condition according to the third voltage, judging the dead battery sequentially according to the first judging condition, the second judging condition, and the third judging condition; completing the above judging steps for a plurality of dead batteries to form a first pre-selection group, a second pre-selection group and a third pre-selection group; and dividing the used batteries, which are simultaneously selected into the first pre-selection group, the second pre-selection group, and the third pre-selection group, into a group. Fast sorting procedure for used batteries claim 1 , characterized in that the target capacity is in the range of 20%-35% of the nominal capacity. Fast sorting procedure for used batteries according to one of the Claims 1 until 2 , characterized in that a first threshold, a second threshold and a third threshold are set, wherein the first threshold is the voltage difference threshold of the first voltage, the second threshold is the voltage difference threshold of the second voltage and the third threshold is the voltage difference threshold of the third voltage. Fast sorting procedure for used batteries claim 3 , characterized in that the step of sequentially judging the used battery according to the first judging condition, the second judging condition and the third judging condition comprises: counting the first voltage, the second voltage and the third voltage of each used battery; counting the first voltage difference value, the second voltage difference value, and the third voltage difference value of each dead battery relative to the first dead battery; sorting the counted dead batteries according to the voltage difference threshold of the first voltage to form a first preselection group; sorting the counted dead batteries according to the voltage difference threshold of the second voltage to form a second preselection group; sorting the counted dead batteries according to the voltage difference threshold of the third voltage to form a third preselection group. A dead battery repairing method, characterized in that it comprises the steps of: leaving the dead battery discharged to the shutdown voltage at room temperature for a first predetermined period of time, measuring the voltage of the dead battery at that time and recording it as a first voltage; charging the spent battery according to the charging method set at the original factory of the spent battery to a target capacity of a preset percentage of the rated capacity, measuring the voltage of the spent battery at that time and recording it as a second voltage; allowing the used battery charged to the target capacity to stand at room temperature for a second predetermined period of time, measuring the voltage of the used battery at that time and recording it as a third voltage; setting a first judging condition according to the first voltage, setting a second judging condition according to the second voltage, and setting a third judging condition according to the third voltage, judging the dead battery sequentially according to the first judging condition, the second judging condition, and the third judging condition; completing the above judging steps for a plurality of dead batteries to form a first pre-selection group, a second pre-selection group and a third pre-selection group; dividing the used batteries, which are simultaneously selected into the first pre-selection group, the second pre-selection group, and the third pre-selection group, into a group; adjusting the first judging condition, the second judging condition, and the third judging condition and grouping all the dead batteries to obtain a plurality of dead battery groups; selecting one or more dead batteries from each dead battery group and detecting the actual capacity of the selected dead battery; sorting out the repairable used battery groups according to the actual capacity of the selected used batteries; discharging the respective spent batteries in each repairable spent battery bank to their shutdown voltage; pouring an appropriate weight of electrolyte into respective dead batteries in each repairable dead battery group and then sealing; wherein an equal weight of electrolyte is filled in the respective dead batteries in each repairable dead battery group; and charging and discharging the spent batteries filled with the electrolyte for activation. Fast sorting procedure for used batteries claim 5 , characterized in that the target capacity is in the range of 20%-35% of the nominal capacity. Fast sorting procedure for used batteries according to one of the Claims 5 until 6 , characterized in that a first threshold, a second threshold and a third threshold are set, wherein the first threshold is the voltage difference threshold of the first voltage, the second threshold is the voltage difference threshold of the second voltage and the third threshold is the voltage difference threshold of the third voltage. Fast sorting procedure for used batteries claim 7 , characterized in that the step of sequentially judging the used battery according to the first judging condition, the second judging condition and the third judging condition comprises: counting the first voltage, the second voltage and the third voltage of each used battery; counting the first voltage difference value, the second voltage difference value, and the third voltage difference value of each dead battery relative to the first dead battery; sorting the counted dead batteries according to the voltage difference threshold of the first voltage to form a first preselection group; sorting the counted dead batteries according to the voltage difference threshold of the second voltage to form a second preselection group; sorting the counted dead batteries according to the voltage difference threshold of the third voltage to form a third preselection group. repair procedures for dead batteries claim 5 , characterized in that when the actual capacity of the selected used batteries is 60%-80% of the rated capacity, the used battery group in which the selected used batteries are located is the repairable used battery group. repair procedures for dead batteries claim 5 , characterized in that the method of charging and discharging for activation is as follows: leaving the discarded battery filled with the electrolyte to allow the electrolyte to fully permeate the inside of the battery, charging the battery with the first constant current up to the upper limit of the battery voltage, and then discharging the battery with the second constant current to the shutdown voltage. repair procedures for dead batteries claim 10 , characterized in that the first constant current is 0.01 C-0.1 C of the rated capacity of the used battery, wherein the second constant current is 0.5 C-1 C of the rated capacity of the used battery. repair procedures for dead batteries claim 10 characterized in that the standing of the spent battery filled with the electrolyte is as follows: leaving the repairable spent battery filled with the electrolyte at 35°C-50°C for 1 day to 5 days. repair procedures for dead batteries claim 5 , characterized in that the step of grouping the activated used batteries and forming a battery group comprises: detecting the discharge capacity and the charge transfer impedance of the activated used batteries; classifying the activated dead batteries according to the discharge capacity; grouping the activated dead batteries into the same class according to charge transfer resistance; Forming a battery group by the discarded batteries classified into the same group. repair procedures for dead batteries Claim 13 , characterized in that the method for classifying the activated dead batteries according to the discharge capacity is as follows: that with the set capacity difference as an interval, the discharge capacity into different Classification intervals is divided, the activated used batteries are classified according to the classification interval in which the discharge capacity is located. repair procedures for dead batteries Claim 14 , characterized in that the capacity difference is 0-5% of the nominal capacity of the used battery. repair procedures for dead batteries Claim 13 , characterized in that the method for grouping the activated discarded batteries in the same class according to the charge transfer resistance is as follows: that with the set charge transfer impedance difference as the interval, the charge transfer impedance is divided into different grouping intervals, the activated discarded batteries according to the grouping interval in which the charge transfer impedance is located. repair procedures for dead batteries Claim 13 , characterized in that the charge transfer impedance difference is 10%-15% of the average charge transfer impedance of the activated spent batteries in the same class. repair procedures for dead batteries claim 5 , characterized in that the procedure for filling the electrolyte is as follows: removing the top cover of the repairable discarded battery, cutting off a part of the protective rubber on the battery cover plate to form a rubber hole in an environment where the dew point temperature is lower than or equal to - 35°C, aligning with the rubber hole and piercing the battery cover plate, and aligning the liquid injection nozzle with the rubber hole to start vacuuming, filling the electrolyte after vacuuming. repair procedures for dead batteries claim 5 , characterized in that the actual capacity detection method is as follows: subjecting the spent battery to a charge and discharge cycle with a certain constant current value and recording its discharge capacity, which is the actual capacity. repair procedures for dead batteries claim 5 , characterized in that the method of calculating the weight of the electrolyte to be filled in each discarded battery in each repairable discarded battery group is as follows: calculating the maximum capacity loss of the selected discarded battery, calculating the mass of the electrolyte charged for each discarded battery must be refilled in the repairable used battery group.

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