CN115036598A - Method for repairing rechargeable battery by breaking lithium dendrites - Google Patents

Abstract

The invention discloses a method for repairing a rechargeable battery by breaking lithium dendrites, which adopts a mode of applying current to a battery cell of a ternary lithium battery or a lithium iron phosphate battery for repairing; the method comprises three repair stages in sequence: s1, in the first stage, applying square wave pulse current to the battery cell to repair; s2, in the second stage, applying sinusoidal current to the battery cell for repairing; and S3, in the third stage, applying the current of the | sinT | periodic function to the battery cell for repairing. After the first stage, the activity of the battery can be effectively activated, lithium dendrites can be effectively stripped, the formation of the lithium dendrites is inhibited, the voltage of the battery cell is recovered, and the internal resistance of the battery cell is reduced; after the second-stage repair, the residual lithium dendritic crystals of the battery core can be further crushed; after the repairing is carried out in the third stage, the repairing effect can be further consolidated, the structure of the anode and cathode materials is stabilized, the activity of the electrolyte is activated, the long-term effect of the repairing result is guaranteed, the internal resistance of the battery core is stabilized, and the stability between batteries is improved.

Description

A method for breaking lithium dendrites to repair rechargeable batteries

technical field

The invention relates to the technical field of battery charging, in particular to a method for repairing a rechargeable battery by breaking lithium dendrites.

Background technique

Emerging industries such as high-end communication terminals, electric vehicle industry, aerospace field, and large-scale energy storage stations have entered a stage of rapid development, so lithium batteries are also widely used in all walks of life. From the perspective of market statistics, lithium batteries are mainly portable digital products such as mobile phones, notebook computers, and digital cameras in electronic products; electric vehicles such as electric bicycles and electric vehicles in transportation; Aerospace and energy storage applications.

One of the cores of the lithium battery system is the negative electrode of the battery, and the negative electrode of the lithium battery is usually made of lithium metal materials. Although lithium metal has great advantages as a battery anode, there are still some shortcomings that need to be solved urgently. There are still two difficulties in the application of lithium metal anodes. On the one hand, during the continuous electrodeposition process on the lithium metal surface, due to the different liquid-phase mass transfer fluxes of local lithium ions, it is easy to cause uneven lithium deposition, which in turn produces dendritic lithium dendrites. Li dendrite growth is one of the fundamental problems affecting the safety and stability of Li-ion batteries. The growth of lithium dendrites can lead to the instability of the electrode and electrolyte interface in Li-ion batteries during cycling, and destroy the resulting solid electrolyte interface (SEI) film. The irreversible deposition of dead lithium results in low coulombic efficiency. The formation of lithium dendrites can even pierce the separator and cause a short circuit inside the lithium-ion battery, resulting in a thermal runaway of the battery and a combustion explosion.

Therefore, solving the problems caused by lithium dendrites is an urgent problem to be solved in the field of lithium batteries. Among the existing technologies for solving lithium dendrites, the industry mostly adopts methods to inhibit the growth of lithium dendrites, such as passively inhibiting the growth of lithium dendrites by adding a coating separator. The piezoelectric polymer coating is in contact with the negative electrode of the battery. When the battery has a small amount of lithium dendrites formed during the cycle, the coated separator is squeezed at the point where the small amount of lithium dendrites is generated to generate a piezoelectric potential. The lithium element is inhibited from continuing to deposit at this point, so as to achieve the purpose of inhibiting the growth of lithium dendrites.

In addition, the industry has also adopted the method of removing lithium dendrites to solve the above problems. Specifically, the solid electrolyte interface film on the surface of the positive and negative electrodes is positioned, and then an electromagnetic shock wave is used to impact it, thereby removing the trace lithium dendrites generated on the surface of the positive and negative electrodes during the formation process.

However, neither the coating separator nor the method of removing lithium dendrites by electromagnetic shock waves can quickly and efficiently remove lithium dendrites from lithium batteries.

SUMMARY OF THE INVENTION

In order to solve this problem in the prior art, the present invention provides a method for repairing a rechargeable battery by breaking lithium dendrites, which is carried out by applying current to the battery cell; it is characterized in that, the method includes three steps in sequence. repair phase:

S1. In the first stage, a square wave pulse current is applied to the battery cells for repair;

S2, the second stage, apply sinusoidal current to the battery cells to repair;

S3. In the third stage, the current of the periodic function of |sinT| is applied to the battery cells to repair.

Wherein, the rechargeable battery is a ternary lithium battery or a lithium iron phosphate battery.

Further, in the first stage, the voltage amplitude of the square wave pulse current applied by the repairing ternary lithium battery is 5.8V; or the voltage amplitude of the square wave pulse current applied by the repairing lithium iron phosphate battery is 5V. The pulse frequency, pulse duty cycle and pulse recovery time of the square wave pulse satisfy the following expressions:

Pulse frequency: 1000+145X(Hz) (1)

Duty cycle: (55+X)% (2)

Repair time: 30+10X (3)

Wherein, X is the first-stage evaluation variable, the unit of pulse frequency is Hz, and the unit of repair time is minutes; the variable X is determined by the following table;

Among them, the charging completion voltage U ₁ , cell capacity C ₁ , internal resistance increase ΔR ₁ , charging temperature rise ΔT ₁ , and charge stop voltage drop ΔU ₁ are measured from the start to completion of charging of the rechargeable battery.

Further, the pulse frequency, peak voltage and repair time of the sinusoidal current in the second stage satisfy the following expressions:

Pulse frequency: 180+35Y (4)

Peak voltage: ternary lithium battery 6.2±Y or lithium iron phosphate battery 5.1±Y (5)

Repair time: 30+12Y (6)

Wherein, Y is the evaluation variable of the second stage, the unit of pulse frequency is Hz, and the unit of repair time is minutes; the variable Y is determined by the following table;

In the second stage, the charging completion voltage U ₁₁ , cell capacity C ₂ , internal resistance increase ΔR ₂ , and charging temperature rise ΔT are measured by measuring the charging completion voltage of the ternary lithium battery or lithium iron phosphate after the first stage. ₂ to determine the variable Y.

Further, the pulse frequency of the current applying the |sinT| periodic function, the peak voltage of the current and the repair time in the third stage satisfy the following expressions:

Pulse frequency: 120+60Z (7)

Peak voltage: 5.8±Z for ternary lithium battery or 4.9±Z for lithium iron phosphate battery (8)

Repair time: 30+15Z (9)

Wherein Z is the evaluation variable of the third stage, the unit of pulse frequency is Hz, and the unit of repair time is minutes; the variable Z is determined by the following table:

The value of the variable Z is determined by measuring the charging completion voltage U ₁₃ and the cell capacity C ₃ of the rechargeable battery after the second stage.

Further, in any stage of repairing the rechargeable battery; when the charging completion voltage U ₁₁ or the charging completion voltage U ₁₂ or the charging completion voltage U ₁₃ of the ternary lithium battery reaches 4.17V or more, the repairing of the rechargeable battery is stopped. ;

Alternatively, when the charging completion voltage U ₁₁ or the charging completion voltage U ₁₂ or the charging completion voltage U ₁₃ of the lithium iron phosphate battery reaches 3.48V or higher, the repairing of the rechargeable battery is stopped.

Description of drawings

FIG. 1 is a schematic diagram of a method for repairing a rechargeable battery by breaking lithium dendrites proposed by the present invention.

FIG. 2 is a schematic diagram of a square wave input of a method for breaking lithium dendrites to repair a rechargeable battery proposed by the present invention.

FIG. 3 is a schematic diagram of the input sine wave of a method for breaking lithium dendrites to repair a rechargeable battery proposed by the present invention.

FIG. 4 is a schematic diagram of the input |sinx| period function current of a method for breaking lithium dendrites to repair a rechargeable battery proposed by the present invention.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Referring to FIG. 1 , it shows the circuit structure of the method for breaking lithium dendrites and repairing a rechargeable battery proposed by the present invention by adopting a switching power supply to input a high-frequency current i _in .

In Figure 1, i _in is the high-frequency current generated by the switching power supply, which is input to the positive and negative poles of the rechargeable battery. The method proposed by the invention can be applied to ternary lithium batteries and lithium iron phosphate batteries.

The method for repairing a rechargeable battery by breaking lithium dendrites proposed by the present invention sequentially includes three repair stages:

S1. The first stage of the method of breaking the lithium dendrite to repair the rechargeable battery:

In order to break the lithium dendrites of the rechargeable battery, referring to Figures 1 and 2, the first stage of repairing the rechargeable battery by breaking the lithium dendrites is to apply a square wave pulse current to the battery cells for repairing. For different types of rechargeable batteries, the voltage of the repair current is different. Specifically, for ternary lithium batteries, the voltage amplitude U of the square wave pulse current used for repair is 5.8V; for lithium iron phosphate batteries, the voltage amplitude U of the square wave pulse current used for repair is 5V . And in the first stage of repairing the rechargeable battery by breaking the lithium dendrite, the pulse frequency, pulse duty cycle and pulse repair time of the repairing square wave pulse satisfy the following expressions:

Pulse frequency: 1000+145X(Hz) (1)

Duty cycle: (55+X)% (2)

Repair time: 30+10X (3)

Wherein, X is the first-stage evaluation variable, the unit of pulse frequency is Hz, and the unit of repair time is minutes; the variable X is determined by Table 1 below;

Table 1

In Table 1, according to the characteristics of ternary lithium and lithium iron phosphate cells, the charging completion voltage U ₁ , the cell capacity C ₁ , the increase in internal resistance ΔR ₁ , the charging temperature rise and the charging completion voltage U 1 measured from the start to the completion of the battery charging are proposed According to the 4-level evaluation standard of the five dimensions of the amount ΔT ₁ and the charge stop voltage drop ΔU ₁ , the variable X is marked according to the 4-level evaluation standard, and the obtained value of the variable X is applied to the above formulas (1)-(3), Thereby, the square wave pulse of the first stage of the method for breaking the lithium dendrite to repair the rechargeable battery is obtained. For example, for a ternary lithium battery, the method of breaking the lithium dendrite to repair the ternary lithium battery is: first, the voltage amplitude of the square wave pulse is 5.8V; when the measured voltage, cell capacity, and internal resistance increase The voltage drop, charging temperature rise, and charge stop voltage drop are in the first gear, that is, charging completion voltage < 3.7V, cell capacity < 55%, internal resistance increase ≥ 40%, charging temperature rise ≥ 2°C, and charging stops When the voltage drop is greater than or equal to 0.5V, the variable X is in the first gear in Table 1, and the variable X is assigned a value of 4, so that the obtained square wave pulse frequency is 1000+145×4=1580(Hz), and the duty cycle is 54%, the square wave pulse is applied to the ternary lithium battery to break the lithium dendrite to repair the battery, and the repair time is 30+40=70 minutes.

For other situations, it is similar to the above-mentioned ternary lithium battery and will not be repeated here.

After the first stage of the method for repairing the rechargeable battery by breaking the lithium dendrite, it can effectively activate the battery activity, effectively strip the lithium dendrite, inhibit the formation of the lithium dendrite, restore the voltage of the battery cell, reduce the internal resistance of the battery cell, and increase the capacity. There is obvious effect.

S2, the second stage of the method for breaking the lithium dendrite to repair the rechargeable battery;

After the first stage is completed, the second stage of breaking the lithium dendrites to repair the rechargeable battery is followed; in the second stage, the battery cells are repaired by applying a sinusoidal current, as shown in FIG. 3 . The voltage amplitude of the sinusoidal current at this stage is divided into: the voltage peak value U of the sinusoidal current for repairing the ternary lithium battery and the voltage peak value U of the sinusoidal current for repairing the lithium iron phosphate battery, the frequency of the sinusoidal current and the repairing time of the sinusoidal current meet the following requirements expression:

Pulse frequency: 180+35Y (4)

Peak voltage: ternary lithium battery 6.2±Y or lithium iron phosphate battery 5.1±Y (5)

Repair time: 30+12Y (6)

Among them, Y is the evaluation variable of the second stage, the unit of pulse frequency is Hz, and the unit of repair time is minutes. The variable Y is determined from Table 2 below.

Table 2

In the second stage, the value of the variable Y is determined according to Table 2, by measuring the voltage U ₁₁ , the cell capacity C ₂ , and the internal resistance of the ternary lithium battery or lithium iron phosphate after the first stage. For the four parameters of increase ΔR ₂ and charging temperature rise ΔT ₂ , the variable Y is assigned the corresponding value according to the corresponding relationship in Table 2, so as to determine the pulse frequency of the sinusoidal current, the peak voltage and the repair time of the sinusoidal current.

For example, when the measured voltage of the ternary lithium battery is less than 3.8V, the cell capacity is less than 70%, the internal resistance increase is greater than or equal to 30%, and the charging temperature rise is greater than or equal to 1.8°C, the variable Y is assigned a value of 4; Therefore, according to formulas (4)-(6), the current frequency of the sinusoidal current is 180+35×4=320Hz, the peak voltage of the sinusoidal current is 6.2±4V, and the repair time is 30+12Y=30+48=78 minutes.

For other situations, it is similar to the above-mentioned ternary lithium battery and will not be repeated here.

After the second stage of repair, the residual lithium dendrites in the battery can be further broken, which largely prevents the safety risks caused by lithium dendrites piercing the battery separator, consolidates the repair effect, and prolongs the use of the battery. life.

S3, the third stage of the method for breaking the lithium dendrite to repair the rechargeable battery;

After the second stage is completed, the third stage of breaking the lithium dendrites to repair the rechargeable battery is carried out; in the third stage, the current of the periodic function of |sinT| is applied to the rechargeable battery cells to repair, as shown in Figure 4; The current frequency of the repair current, the peak voltage U of the current, and the repair time of the applied |sinT| periodic function satisfy the following expressions:

Pulse frequency: 120+60Z (7)

Peak voltage: 5.8±Z for ternary lithium battery or 4.9±Z for lithium iron phosphate battery (8)

Repair time: 30+15Z (9)

Wherein Z is the evaluation variable of the third stage, the unit of pulse frequency is Hz, the unit of repair time is minute; Described variable Z is determined by following table 3:

table 3

In the third stage, the value of the variable Z is determined according to Table 3. After the second stage, the ternary lithium battery or the lithium iron phosphate battery is charged to complete the voltage U ₁₃ and the cell capacity C ₃ by measuring the voltage U 13 and the cell capacity C 3 . The corresponding relationship of 3 assigns the corresponding value to the variable Z, thereby determining the pulse frequency, peak voltage and repair time of the |sinT| periodic function current.

For example, when the measured ternary lithium battery is charged with a voltage of 3.9-4.05V and a cell capacity of 70-82%, the variable Z is assigned a value of 3; therefore, according to equations (7)-(9), The current frequency of the |sinT| periodic function current is 120+60×3=300Hz, the peak voltage is 5.8±3V, and the repair time is 30+15Z=30+45=75 minutes.

For other situations, it is similar to the above-mentioned ternary lithium battery and will not be repeated here.

The third stage of the method of breaking the lithium dendrite to repair the rechargeable battery can further consolidate the repair effect, stabilize the structure of the positive and negative materials, activate the electrolyte activity, ensure the long-term effect of the repair result, stabilize the internal resistance of the cell, and improve the battery stability between.

Further, it should be noted that, in any of the first, second and third stages, if it is detected that the charging completion voltage of the battery reaches a certain value, the repairing of the broken lithium dendrites of the battery ends, for example In the first stage, for the ternary lithium battery, when the charging completion voltage U ₁₁ ≥ 4.17V; or for the lithium iron phosphate battery, when the charging completion voltage U ₁₁ ≥ 3.48V, the repair ends.

Similarly, for the second stage, for the ternary lithium battery, when the charging completion voltage U ₁₂ ≥ 4.17V; or for the lithium iron phosphate battery, when the charging completion voltage U ₁₂ ≥ 3.48V, the repair ends.

For the third stage, when the charging completion voltage U ₁₃ ≥ 4.17V; or for the lithium iron phosphate battery, when the charging completion voltage U ₁₃ ≥ 3.48V, the repair ends.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (7)

1. A method for repairing a rechargeable battery by breaking lithium dendrites adopts a mode of applying current to a battery cell to repair; the method is characterized by comprising three repairing stages in sequence:

s1, in the first stage, applying square wave pulse current to the battery cell for repairing;

s2, in the second stage, applying sinusoidal current to the battery cell to repair;

and S3, in the third stage, applying the current of the | sinT | periodic function to the battery cell for repairing.

2. The method for repairing rechargeable batteries by breaking lithium dendrites according to claim 1 wherein: the rechargeable battery is a ternary lithium battery or a lithium iron phosphate battery.

3. The method of claim 2, wherein the method comprises the steps of: in the first stage, the voltage amplitude of square wave pulse current applied by the repairing ternary lithium battery is 5.8V; or the voltage amplitude of the square wave pulse current applied by the repaired lithium iron phosphate battery is 5V.

4. The method of claim 3 for repairing a rechargeable battery by breaking lithium dendrites, wherein: the pulse frequency, the pulse duty ratio and the pulse repair time of the square wave pulse meet the following expression:

pulse frequency 1000+145X (Hz) (1)

Duty ratio (55+ X)% (2)

Repair time 30+10X (3)

Wherein X is an evaluation variable of the first stage, the unit of pulse frequency is Hz, and the unit of repair time is minutes; the variable X is determined by the following table;

wherein the charging completion voltage U ₁ And cell capacity C ₁ Increase in internal resistance Δ R ₁ Temperature rise amount of charging delta T ₁ Charge stop voltage drop amount Δ U ₁ Measured from the beginning to the completion of charging the rechargeable battery.

5. The method of claim 4, wherein the method comprises the steps of:

wherein the pulse frequency, peak voltage and repair time of the sinusoidal current of the second stage satisfy the following expression:

pulse frequency: 180+35Y (4)

Peak voltage: ternary lithium battery 6.2 + -Y or lithium iron phosphate battery 5.1 + -Y (5)

Repairing time: 30+12Y (6)

Wherein Y is an evaluation variable of the second stage, the unit of pulse frequency is Hz, and the unit of repair time is minutes; the variable Y is determined from the following table;

in the second stage, the voltage U is measured by measuring the charging completion voltage of the ternary lithium battery or the lithium iron phosphate battery after the first stage ₁₁ And battery cell capacity C ₂ Increase in internal resistance Δ R ₂ Temperature rise during charging delta T ₂ The variable Y is determined.

6. The method of claim 5, wherein the method comprises the steps of:

wherein the pulse frequency of the current, the peak voltage of the current, and the repair time of the applied | sinT | periodic function of the third stage satisfy the following expressions:

pulse frequency: 120+60Z (7)

Peak voltage: ternary lithium battery 5.8 + -Z or lithium iron phosphate battery 4.9 + -Z (8)

Repairing time: 30+15Z (9)

Wherein Z is an evaluation variable of the third stage, the unit of the pulse frequency is Hz, and the unit of the repair time is minutes; the variable Z is determined by the following table:

wherein the variable Z is obtained by measuring the charging completion voltage U of the rechargeable battery after the second stage ₁₃ And cell capacity C ₃ To determine the variable Z.

7. The method of fragmenting a lithium dendrite repair rechargeable battery according to any one of claims 4-6 wherein:

when the charging of the ternary lithium battery is completed by a voltage U ₁₁ Or charging completion voltage U ₁₂ Or a charge completion voltage U ₁₃ Stopping repairing the rechargeable battery when the voltage reaches more than 4.17V;

or, when the charging of the lithium iron phosphate battery is completed, the voltage U ₁₁ Or a charge completion voltage U ₁₂ Or a charge completion voltage U ₁₃ And stopping repairing the rechargeable battery when the voltage reaches above 3.48V.

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