CN113894067A - A sorting method for cascade utilization of ternary lithium batteries - Google Patents

Abstract

The invention discloses a sorting method for gradient utilization of a ternary lithium battery, which comprises the following steps: adjusting the voltage of the battery to be sorted to a specified voltage in a constant current mode; performing charge and discharge processing on the battery according to the specified voltage and a first preset voltage; calculating the actual direct current resistance of the battery to be sorted according to the direct current resistance of the battery to be sorted in the charging and discharging process; processing the battery to be sorted by adopting constant current, and calculating parameters required by sorting in the processing process; the method comprises the steps of obtaining a battery temperature change curve and a peak temperature, sorting and eliminating the batteries according to the battery temperature change curve and the peak temperature, and sorting the batteries into groups according to actual direct current resistance of the batteries to be sorted and parameters required by sorting. The invention solves the problem that the aging degree and the aging speed of the batteries are inconsistent after grouping because the batteries are not sorted according to the internal mechanism characteristics of the batteries.

Description

A sorting method for cascade utilization of ternary lithium batteries

technical field

The invention relates to the technical field of lithium ion batteries, in particular to a sorting method for cascaded utilization of ternary lithium batteries.

Background technique

With the rise of the electric vehicle industry, the sales of electric vehicles are increasing, and at the same time, the sales of lithium-ion batteries have also risen sharply. As a high-quality lithium-ion battery, ternary lithium batteries are widely used in electric vehicles.

For electric vehicles, in order to ensure the endurance of the car, when the capacity of the battery drops to a certain level (for example, 80%), it needs to be eliminated from the car. If it is eliminated directly, the residual value of the battery will be wasted. Therefore, The retired ternary lithium battery needs to be used in cascade.

However, due to the large difference in performance of ternary lithium batteries after different charging and discharging processes, if they are used directly without being grouped, the capacity performance, power performance and the remaining life of the battery pack will be affected. , while retired batteries are more likely to fail. The current sorting methods are generally based on the external characteristics of the battery, and the internal mechanism characteristics of the battery are rarely sorted. As a result, after the batteries are grouped, the aging degree of the battery is inconsistent with the aging speed, which affects the service life of the battery pack.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the above-mentioned technical deficiencies, and to provide a sorting method for using ternary lithium batteries in a cascade, so as to solve the problem that the aging degree of the batteries and the Technical issues with inconsistent aging rates.

In order to achieve the above-mentioned technical purpose, the present invention has adopted the following technical solutions:

The present invention provides a sorting method for cascade utilization of ternary lithium batteries, comprising:

Step 1. Adjust the voltage of the battery to be sorted to the specified voltage by means of constant current;

Step 2, charging and discharging the battery according to the specified voltage and the first preset voltage;

Step 3: Calculate the actual DC resistance of the battery to be sorted according to the DC resistance of the battery to be sorted during the charging and discharging process;

Step 4. Use constant current to process the battery to be sorted, and calculate the parameters required for sorting in the process;

Step 5: Obtain the battery temperature change curve and peak temperature in the process of step 1 to step 4, after sorting and eliminating the battery according to the battery temperature change curve and the peak temperature, according to the actual DC resistance of the battery to be sorted and the temperature. Select the required parameters to sort the batteries into groups.

Preferably, in the sorting method using ternary lithium batteries in steps, the specified voltage is an average value of open circuit voltages of several batteries to be sorted.

Preferably, in the sorting method using ternary lithium batteries in steps, in the second step, when the specified voltage is higher than the first preset voltage, a large current is used to sequentially perform pulse discharge and Pulse charging; when the specified voltage is lower than the first preset voltage, a large current is used to sequentially perform pulse charging and pulse discharging of the batteries to be sorted.

Preferably, in the sorting method using ternary lithium batteries in a cascade, the pulse charging and the pulse discharging time are both 10-30 seconds, and the pulse discharging and the pulse charging current are both 3-5C.

Preferably, in the sorting method for ternary lithium batteries using cascaded utilization, the step 3 specifically includes:

Calculate the DC resistance of the battery to be sorted during pulse discharge and pulse charging, calculate the average value of the DC resistance during pulse discharge and pulse charging, and use the average value as the actual DC resistance of the battery to be sorted.

Preferably, in the sorting method using ternary lithium batteries in a cascade, the calculation formula of the actual DC resistance of the batteries to be sorted is:

表示待分选电池的实际直流电阻，R1表示待分选电池在脉冲放电过程中的直流电阻，R2表示待分选电池在脉冲充电过程中的直流电阻，U1表示脉冲放电开始前的电压，U2表示脉冲放电结束前的电压，U3表示脉冲充电开始前的电压，U4表示脉冲充电结束前的电压，I为脉冲放电以及脉冲充电的电流大小。in,

Represents the actual DC resistance of the battery to be sorted, R1 represents the DC resistance of the battery to be sorted during the pulse discharge process, R2 represents the DC resistance of the battery to be sorted during the pulse charging process, U1 represents the voltage before the pulse discharge begins, U2 Represents the voltage before the end of the pulse discharge, U3 represents the voltage before the start of the pulse charge, U4 represents the voltage before the end of the pulse charge, and I is the current size of the pulse discharge and pulse charge.

Preferably, in the sorting method using ternary lithium batteries in a cascade, in the step 4, the parameter required for the sorting is the battery terminal voltage, and the step 4 specifically includes:

The battery to be sorted is discharged with a constant current for a short time until the ΔSOC of the battery is 10-25%, and the battery terminal voltage is recorded after standing for a preset time.

Preferably, in the sorting method for ternary lithium batteries using cascaded utilization, in the step 4, the parameter required for the sorting is the charging capacity, and the step 4 specifically includes:

The battery to be sorted is charged to a specified voltage with a constant current, and the current is recorded as I1, and the charging capacity Q of the battery to be sorted during this time period is recorded.

Preferably, in the sorting method for ternary lithium batteries using cascaded utilization, the formula for calculating the charging capacity is:

Among them, Q represents the charging capacity Q of the battery to be sorted in the time period t, and I 1 represents the magnitude of the constant current.

Preferably, in the sorting method for ternary lithium batteries using cascaded utilization, in the step 5, the sorting and elimination of the batteries according to the battery temperature change curve and the peak temperature is specifically:

Calculate the average temperature value of the battery to be sorted according to the battery temperature change curve, and sort and eliminate the battery according to the average temperature value and peak temperature of the battery to be sorted.

Compared with the prior art, the sorting method of the ternary lithium battery provided by the present invention firstly adjusts the voltage of the battery to be sorted to a specified voltage, and then adjusts the initial state of each battery according to the specified voltage and the battery open circuit voltage. Carry out consistent initialization processing, so as to better use the parameter differences in the test process to sort the batteries, and adjust the batteries to the same voltage value in the shortest time possible, and then calculate the battery's The actual DC resistance, and then use the constant current processing method to obtain the required parameters for sorting, and then directly eliminate the battery with abnormal temperature during the test process, use the actual DC resistance of the battery to be sorted and the parameters required for the sorting. The batteries are sorted into groups and tested at the time end, which greatly reduces the time cost and labor cost of sorting, and integrates the internal characteristic parameters of the battery, which makes the sorting accuracy higher, and integrates the electrochemical characteristics of the ternary lithium battery. The characteristics of the battery’s voltage mutation are used to sort the batteries, so that the sorting process takes into account the internal mechanism characteristics of the battery, avoiding the inconsistency of the aging degree and aging speed of the battery when using the ternary lithium battery in the cascade utilization, and ensuring the cascade battery pack. service life.

Description of drawings

FIG. 1 is a flow chart of a preferred embodiment of the sorting method for ternary lithium batteries provided by the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Referring to FIG. 1 , the sorting method for ternary lithium batteries provided by the embodiment of the present invention includes the following steps:

S100, using a constant current method to adjust the voltage of the battery to be sorted to a specified voltage;

S200, charging and discharging the battery according to the specified voltage and the first preset voltage;

S300, according to the DC resistance of the battery to be sorted during the charging and discharging process, calculate the actual DC resistance of the battery to be sorted;

S400, using a constant current to process the battery to be sorted, and calculating the parameters required for sorting during the processing;

S500: Obtain the battery temperature change curve and the peak temperature in the process from step S100 to step S400, after sorting and eliminating the batteries according to the battery temperature change curve and the peak temperature, according to the actual DC resistance of the battery to be sorted and the Select the required parameters to sort the batteries into groups.

In this embodiment, the voltage of the battery to be sorted is adjusted to the specified voltage first, and then the initial state of each battery is initialized consistently according to the specified voltage and the battery open-circuit voltage, so as to make better use of the parameter difference in the test process. Sort the battery, and adjust the battery to the same voltage value in the shortest time possible, then calculate the actual DC resistance of the battery by pulse charging and discharging, and then use the constant current process to obtain the parameters required for sorting , and then directly eliminate the batteries with abnormal temperature during the test process, use the actual DC resistance of the batteries to be sorted and the parameters required for the sorting to sort the batteries into groups, and test the time end, which greatly shortens the sorting time. cost and labor cost, and the internal characteristic parameters of the battery are integrated, so that the sorting accuracy is higher, the electrochemical characteristics of the ternary lithium battery are integrated, and the battery's voltage mutation characteristics are used to sort the battery, so that the sorting process is Taking into account the internal mechanism characteristics of the battery, it avoids the inconsistency of the aging degree and aging speed of the battery when using the ternary lithium battery in the cascade utilization, and ensures the service life of the cascade battery pack.

In a preferred embodiment, before the step S100, it further includes:

The appearance of the battery is tested, and the battery with appearance failure is eliminated to obtain the battery to be sorted.

In this embodiment, the appearance failures include at least flatulence, mechanical damage, corrosion and thermal dissolution. In the embodiment of the present invention, the batteries with appearance failures are directly eliminated, so as to avoid potential safety hazards in the subsequent use of ternary lithium batteries.

In a preferred embodiment, in the step S100, since the initial voltages of the batteries to be sorted are inconsistent, in order to ensure the consistency of the initial states of the sorting, a consistent initialization process is performed on the batteries, and the voltages of the batteries are adjusted to Specify the voltage, if the current open circuit voltage of the battery is higher than the specified voltage, the battery voltage will be adjusted to the specified voltage by discharging mode, and left for 1min; if the current battery open circuit voltage is lower than the specified voltage, the battery voltage will be charged by charging mode. Adjust to the specified voltage and let stand for 1min. By setting the specified voltage, the voltage of each battery can be adjusted to the same voltage value in the shortest time.

Preferably, in this embodiment, the specified voltage is an average value of open circuit voltages of several batteries to be sorted. Therefore, the voltage of each battery can be adjusted to the same voltage value in the shortest time.

In a preferred embodiment, in the step S200, when the specified voltage is higher than the first preset voltage, a large current is used to sequentially perform pulse discharge and pulse charge on the battery to be sorted; when the specified voltage is lower than At the first preset voltage, a large current is used to sequentially perform pulse charging and pulse discharging of the batteries to be sorted. Thus, the actual DC resistance of the battery can be calculated according to the actual situation.

Specifically, in this embodiment, the magnitude of the first preset voltage is 3.7V, that is, the average discharge voltage of the ternary battery, and it can be understood that the SOC is close to 50%. When the SOC is low, it is charged, and when the SOC is high, it is discharged, which can prevent the battery from being overcharged or over-discharged, causing irreversible damage to the battery.

Preferably, in the step S200, the pulse discharge process is specifically as follows: use a large current to perform pulse discharge on the battery to be sorted, and leave it for a first time. The specific process of pulse charging is as follows: use a large battery to perform pulse charging on the battery to be sorted, and let it stand for a second time. Wherein, the first time and the second time are both 1 minute, and standing for 1 minute can shorten the detection time and eliminate the polarization of the battery. Of course, in other embodiments, the standing time can also be selected according to the actual situation. This embodiment of the present invention does not limit this.

Among them, the time of pulse charging and pulse discharging is the same, which is 10 to 30 seconds. In addition, the polarization internal resistance is a key factor in evaluating battery aging. In order to better reflect the polarization internal resistance of the battery, generally speaking, the discharge rate is The larger the value is, the more obvious the polarization is. However, if the current is too large, it is easy to cause irreversible damage to the battery. Therefore, in the embodiment of the present invention, the currents of pulse charging and pulse discharging are set to be the same, and both are selected to be 3 to 5C, and the first time is 1 minutes, the second time is 1 minute.

In a preferred embodiment, the step S300 specifically includes:

Calculate the DC resistance of the battery to be sorted during pulse discharge and pulse charging, calculate the average value of the DC resistance during pulse discharge and pulse charging, and use the average value as the actual DC resistance of the battery to be sorted.

In a preferred embodiment, the calculation formula of the actual DC resistance of the battery to be sorted is:

表示待分选电池的实际直流电阻，R1表示待分选电池在脉冲放电过程中的直流电阻，R2表示待分选电池在脉冲充电过程中的直流电阻，U1表示脉冲放电开始前的电压，U2表示脉冲放电结束前的电压，U3表示脉冲充电开始前的电压，U4表示脉冲充电结束前的电压，I为脉冲放电以及脉冲充电的电流大小。in,

Represents the actual DC resistance of the battery to be sorted, R1 represents the DC resistance of the battery to be sorted during the pulse discharge process, R2 represents the DC resistance of the battery to be sorted during the pulse charging process, U1 represents the voltage before the pulse discharge begins, U2 Represents the voltage before the end of the pulse discharge, U3 represents the voltage before the start of the pulse charge, U4 represents the voltage before the end of the pulse charge, and I is the current size of the pulse discharge and pulse charge.

In a preferred embodiment, in the step S400, the parameter required for the sorting is the battery terminal voltage or the charging capacity. Therefore, the present invention provides two embodiments of the step S400. Specifically,

In the first embodiment, the parameter required for the sorting is the battery terminal voltage, and the step S400 specifically includes:

The battery to be sorted is discharged with a constant current for a short time until the ΔSOC of the battery is 10-25%, and the battery terminal voltage is recorded after standing for a preset time.

In this embodiment, the terminal voltage is used to evaluate the battery performance. For a ternary lithium battery, in the range of 30-70%, its voltage does not change much with the SOC (there is a stable voltage platform), and in the selected Within the test SOC range of , the battery voltage changes significantly with SOC. For lithium batteries of different health states, after discharging the same ΔSOC power, the voltage changes significantly. Therefore, this embodiment performs battery sorting based on this, which has high accuracy. Among them, the constant current discharge current is 0.5-2C; the preset time is 3-30min.

In the second embodiment, the parameter required for the sorting is the charging capacity, and the step S400 specifically includes:

The battery to be sorted is charged to a specified voltage with a constant current, and the current is recorded as I1, and the charging capacity Q of the battery to be sorted during this time period is recorded.

In this embodiment, the calculation formula of the charging capacity is:

Among them, Q represents the charging capacity Q of the battery to be sorted in the time period t, and I 1 represents the magnitude of the constant current.

In this example, the internal performance of the battery is reflected by the battery capacity. The initial soc is 0, so it needs to be charged, and the charging cut-off battery is 2.8-3.1V, which is lower than the discharge platform battery of the ternary lithium battery. The battery is sorted by the characteristics of the voltage abrupt change in the low SOC state.

In a preferred embodiment, in the step S500, the sorting and elimination of the battery according to the battery temperature change curve and the peak temperature is specifically:

Calculate the average temperature value of the battery to be sorted according to the battery temperature change curve, and sort and eliminate the battery according to the average temperature value and peak temperature of the battery to be sorted.

对于峰值温度高于

的电池，直接淘汰。In this embodiment, the batteries are sorted and eliminated directly according to the temperature value in the test process, and the batteries with unqualified temperature are directly eliminated, so as to avoid potential safety hazards in the future. In specific implementation, calculate the average value of the measured battery temperature

For peak temperatures above

The battery is directly eliminated.

Further, in the step S500, there are two ways to sort the batteries into groups according to the actual DC resistance of the batteries to be sorted and the parameters required for the sorting. Specifically,

以及电池端电压U绘制电池性能二维分布图，分布在同一区域内的电池进行分选成组。其中，区域的大小根据应用场景来设定，本发明对此不做限定。In the first way, according to the DC internal resistance

And the battery terminal voltage U draws a two-dimensional distribution map of battery performance, and the batteries distributed in the same area are sorted into groups. The size of the area is set according to the application scenario, which is not limited in the present invention.

以及充电容量Q绘制电池性能二维分布图，分布在同一区域内的电池进行分选成组。其中，区域的大小根据应用场景来设定，本发明对此不做限定。In the second way, according to the DC internal resistance

As well as the charging capacity Q to draw a two-dimensional distribution map of battery performance, the batteries distributed in the same area are sorted into groups. The size of the area is set according to the application scenario, which is not limited in the present invention.

To sum up, the sorting method of the ternary lithium battery provided by the present invention firstly adjusts the voltage of the battery to be sorted to a specified voltage, and then aligns the initial state of each battery according to the specified voltage and the battery open circuit voltage. In order to make better use of the parameter differences in the test process to sort the batteries, and adjust the batteries to the same voltage value in the shortest time as possible, then calculate the actual DC current of the batteries by pulse charging and discharging. resistance, and then use constant current processing to obtain the parameters required for sorting, and then directly eliminate the battery with abnormal temperature during the test process, and use the actual DC resistance of the battery to be sorted and the parameters required for sorting. Sorting into groups and testing the time end greatly reduces the time cost and labor cost of sorting, and integrates the internal characteristic parameters of the battery, making the sorting accuracy higher, synthesizing the electrochemical characteristics of the ternary lithium battery, using the battery The battery is sorted due to the characteristics of sudden change in voltage, so that the sorting process takes into account the internal mechanism characteristics of the battery, avoiding the inconsistency of the aging degree and aging speed of the battery when using the ternary lithium battery in the cascade utilization, and ensuring the use of the cascade battery pack. life.

The specific embodiments of the present invention described above do not limit the protection scope of the present invention. Any other corresponding changes and modifications made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims (10)

1. A sorting method for utilizing a ternary lithium battery in a gradient manner is characterized by comprising the following steps of:

step one, adjusting the voltage of a battery to be sorted to a specified voltage in a constant current mode;

secondly, charging and discharging the battery according to the specified voltage and the first preset voltage;

step three, calculating the actual direct current resistance of the battery to be sorted according to the direct current resistance of the battery to be sorted in the charging and discharging process;

processing the battery to be sorted by adopting constant current, and calculating parameters required for sorting in the processing process;

and step five, acquiring a battery temperature change curve and a peak temperature in the processes of the step one to the step four, sorting and eliminating the batteries according to the battery temperature change curve and the peak temperature, and sorting the batteries into groups according to the actual direct current resistance of the batteries to be sorted and the parameters required by sorting.

2. The method for sorting a ternary lithium battery by stepwise use according to claim 1, wherein the specified voltage is an average value of open-circuit voltages of a plurality of batteries to be sorted.

3. The method for sorting a ternary lithium battery by echelon utilization according to claim 1, wherein in the second step, when the designated voltage is higher than a first preset voltage, the batteries to be sorted are subjected to pulse discharge and pulse charge in sequence by using a large current; and when the specified voltage is lower than a first preset voltage, pulse charging and pulse discharging are sequentially carried out on the battery to be sorted by adopting a large current.

4. The method for sorting the ternary lithium battery by using the echelon according to claim 3, wherein the pulse charging and the pulse discharging are both performed for 10-30 seconds, and the pulse discharging and the pulse charging are both performed at a current of 3-5 ℃.

5. The method for sorting ternary lithium batteries by gradient utilization according to claim 3, wherein the step three specifically comprises:

and calculating the direct current resistance of the battery to be sorted in the pulse discharging and pulse charging processes, calculating the average value of the direct current resistance in the pulse discharging and pulse charging processes, and taking the average value as the actual direct current resistance of the battery to be sorted.

6. The method for sorting a ternary lithium battery by echelon utilization according to claim 5, wherein the calculation formula of the actual direct current resistance of the battery to be sorted is as follows:

wherein,

the actual direct current resistance of the battery to be sorted is shown, R1 shows the direct current resistance of the battery to be sorted in the pulse discharging process, R2 shows the direct current resistance of the battery to be sorted in the pulse charging process, U1 shows the voltage before the pulse discharging starts, U2 shows the voltage before the pulse discharging ends, U3 shows the voltage before the pulse charging starts, U4 shows the voltage before the pulse charging ends, and I is the current magnitude of the pulse discharging and the pulse charging.

7. The method for sorting ternary lithium batteries by gradient utilization according to claim 1, wherein in the fourth step, the parameter required for sorting is battery terminal voltage, and the fourth step specifically comprises:

discharging the battery to be sorted by adopting constant current for a short time until the delta SOC of the battery is 10-25%, and recording the terminal voltage of the battery after standing for a preset time.

8. The method for sorting ternary lithium batteries by gradient utilization according to claim 1, wherein in the fourth step, the parameter required for sorting is charging capacity, and the fourth step specifically comprises:

and (3) charging the battery to be sorted to a specified voltage by constant current with constant current, recording the current as I1, and recording the charging capacity Q of the battery to be sorted in the time period.

9. The method for sorting a ternary lithium battery by stepwise use according to claim 8, wherein the calculation formula of the charge capacity is:

wherein Q represents the charging capacity Q of the battery to be sorted in the time period t, and I1 represents the magnitude of the constant current.

10. The method for sorting ternary lithium batteries by gradient utilization according to claim 1, wherein in the fifth step, the sorting and elimination of the batteries according to the battery temperature change curve and the peak temperature specifically comprises:

and calculating the average temperature value of the batteries to be sorted according to the battery temperature change curve, and sorting and eliminating the batteries according to the average temperature value and the peak temperature of the batteries to be sorted.

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