A method for quickly identifying the chemical system of retired power lithium-ion batteries

Abstract

The present invention discloses a method for rapidly identifying the chemical system of retired power lithium-ion batteries. The identification method comprises the following steps: (1) establishing the relationship between the capacitance, resistance, battery capacity, and battery electrode area of the lithium-ion battery; (2) establishing the relationship between the Weber impedance of the lithium-ion battery and the battery electrode area; and (3) establishing a characteristic parameter model of the battery system of the lithium-ion battery to determine the chemical system of the lithium-ion battery. The present invention utilizes the electrochemical impedance method to establish a characteristic parameter model of the battery system that is independent of the battery capacity, and integrates the model into a specific device operating on the principle of electrochemical impedance spectroscopy. While detecting battery health parameters, information on the chemical system of the power lithium-ion battery can also be obtained. This method can rapidly detect and evaluate the chemical system of retired power lithium-ion batteries, providing direct assistance for the secondary utilization of retired power lithium-ion batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of power lithium-ion battery applications, and in particular relates to a method for rapidly identifying the chemical system of retired power lithium-ion batteries. Background Art

[0002] Electric vehicles are becoming increasingly popular because they can significantly reduce carbon emissions and urban air pollution. However, the power battery, a key component of electric vehicles, has a significantly shorter service life than the entire vehicle. When it reaches its end of life, it needs to be replaced. Consequently, a large number of power lithium-ion batteries are retired annually. Furthermore, with growing environmental awareness and the increasing number of electric vehicles, the number of retired power lithium-ion batteries is expected to increase further. Unlike batteries with other chemistries, many retired power lithium-ion batteries still exhibit good performance, such as specific energy and remaining capacity, making them highly economical. A growing number of studies indicate that repurposing these retired power lithium-ion batteries, such as for power storage, can fully utilize their residual value while also effectively overcoming the high initial investment cost of lithium-ion batteries for energy storage. This approach also reduces environmental impact, making it a promising solution for retired batteries.

[0003] However, for retired power lithium-ion batteries from different sources, their remaining reversible capacity, internal resistance, state of charge, etc. are all in a relatively discrete state, and they need to be re-tested for charge and discharge, and then divided into groups based on the test results before reuse. However, before charging and discharging the battery, it is necessary to first determine the battery's chemical system and set parameters based on the chemical system, otherwise it will cause battery damage or even cause danger. The power lithium-ion batteries currently used in various types of electric vehicles are mainly lithium iron phosphate systems or nickel-cobalt-manganese ternary material systems. Although their working principles are similar, their working characteristics are different and cannot be mixed. In addition, the two types of batteries are also different in important parameters such as battery safety, cycle life and recycling economy. Therefore, before evaluating the battery health status, it is first necessary to screen the battery's chemical system and identify the chemical system to avoid damaging the battery or causing danger.

[0004] Battery manufacturers rarely label individual batteries with the battery system or use a custom numbering system, making it difficult to directly identify the battery's chemical system. A common quick way to identify a battery is to measure its voltage. However, the operating voltage of lithium iron phosphate batteries ranges from 2.0-3.75V, while the operating voltage range of lithium nickel cobalt manganese oxide batteries is 2.75-4.2V, with significant overlap. This makes it difficult to identify the battery's chemical system simply by measuring voltage, especially for retired batteries with different states of charge.

[0005] Electrochemical impedance spectroscopy (EIS) uses the resistance and capacitance equivalent to the battery structure to approximate the electrical characteristics of a battery. It is less affected by the battery's state of charge. However, the resistance and capacitance data directly obtained from impedance spectroscopy are related to the battery's capacity. Higher capacity results in lower internal resistance and higher capacitance, making it difficult to determine the battery's chemical system. The present invention utilizes EIS to establish a characteristic parameter for the chemical system that is independent of battery capacity, allowing identification of the battery's chemical system. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention provides a method for rapidly identifying the chemical systems of retired power lithium-ion batteries. This method is simple and can quickly detect and evaluate the chemical systems of retired power lithium-ion batteries, providing direct support for the secondary use of retired power lithium-ion batteries.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for quickly identifying the chemical system of retired power lithium-ion batteries comprises the following steps:

[0009] (1) Establish the relationship between the capacitance, resistance, battery capacity and battery electrode area of lithium-ion batteries;

[0010] (2) Establish the relationship between the Weber impedance of lithium-ion batteries and the battery electrode area;

[0011] (3) Establish a characteristic parameter model of the lithium-ion battery system and determine the chemical system of the lithium-ion battery.

[0012] Furthermore, in step (1), the relationship between the capacitance of the lithium-ion battery and the area of the battery electrode is as shown in formula (1):

[0013] C=AC 0 (1)

[0014] Among them, C is the capacitance of the electrode, A is the total area of the electrode, and C 0 is the specific capacitance per unit area.

[0015] Furthermore, the resistance of the lithium-ion battery in step (1) includes the battery interface reaction resistance R r and the battery static internal resistance R l .

[0016] Furthermore, the battery interface reaction resistance R r The relationship with the battery electrode area is shown in formula (2):

[0017]

[0018] Among them, Rr 0 is the reaction resistance per unit area, is the current density.

[0019] Furthermore, the battery static internal resistance R l The relationship with the battery electrode area is shown in formula (3):

[0020]

[0021] Where ρ is the conductivity of the electrolyte, l is the distance between the positive and negative electrodes of the battery, is the liquid phase resistance per unit area.

[0022] Furthermore, the relationship between the battery capacity n and the battery electrode area in step (1) is shown in formula (4):

[0023]

[0024] Among them, k is the coating amount of active material on the electrode sheet per unit area, that is, the surface density. Batteries with the same chemical system are usually constant or change very little.

[0025] Furthermore, the Weber impedance of the lithium-ion battery in step (2) includes an oxidation Weber impedance and a reduction Weber impedance; wherein the oxidation Weber impedance and the reduction Weber impedance of the positive electrode of the battery are respectively shown in formulas (5) and (6), and the oxidation Weber impedance and the reduction Weber impedance of the negative electrode of the battery are respectively shown in formulas (7) and (8):

[0026] For the positive battery terminal:

[0027]

[0028] Similarly, for the negative electrode of the battery:

[0029]

[0030] Furthermore, the specific steps of establishing the characteristic parameter model of the battery system in step (3) are as follows:

[0031] Step S1: Based on a widely recognized equivalent circuit diagram, models of the real part R and imaginary part X of the power battery impedance are established as follows:

[0032]

[0033]

[0034] Step S2: Substitute equations (1) to (8) into the models of the real part R and the imaginary part X of the power battery impedance, respectively, as follows:

[0035]

[0036] You will get:

[0037]

[0038] You will get:

[0039] Step S3: Compare the models of the real part R and the imaginary part X of the power battery impedance simplified in step S2 to obtain the characteristic parameter model of the battery system as follows:

[0040]

[0041] R of batteries with different chemical systems 0 and X 0 The ratio of is different, based on which the above characteristic parameter model can be used to identify the chemical system of the battery.

[0042] Compared with the prior art, the present invention has the following positive and beneficial effects:

[0043] The present invention utilizes electrochemical impedance spectroscopy to establish a characteristic parameter model of a battery system that is independent of battery capacity. Since electrochemical impedance spectroscopy can also be used to detect the health status of a battery, the characteristic parameters of the battery system established by the present invention are integrated into a specific device operating on the principle of electrochemical impedance spectroscopy. While detecting the battery health parameters, information about the chemical system of the power lithium-ion battery can also be obtained. This allows for rapid detection and evaluation of the chemical system of retired power lithium-ion batteries, providing direct assistance for the secondary utilization of retired power lithium-ion batteries. This solves the problem of excessively high primary investment costs for lithium-ion batteries used for energy storage, while also alleviating environmental pollution problems caused by retired power lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a widely recognized equivalent circuit diagram adopted by the present invention. DETAILED DESCRIPTION

[0045] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0046] Example

[0047] A method for quickly identifying the chemical system of retired power lithium-ion batteries, the identification method comprising the following steps:

[0048] (1) Establish the relationship between the capacitance, resistance, battery capacity and battery electrode area of lithium-ion batteries, as follows:

[0049] 1) The relationship between the capacitance of a lithium-ion battery and the area of the battery electrode is shown in formula (1):

[0050] C=AC 0 (1)

[0051] Among them, C is the capacitance of the electrode, A is the total area of the electrode, and C 0 is the specific capacitance per unit area;

[0052] 2) The resistance of lithium-ion batteries includes the battery interface reaction resistance R r and the battery static internal resistance R l ; Among them, the battery interface reaction resistance R r The relationship with the battery electrode area is shown in formula (2):

[0053]

[0054] Among them, R r 0 is the reaction resistance per unit area, is the current density;

[0055] Battery static internal resistance R l The relationship with the battery electrode area is shown in formula (3):

[0056]

[0057] Among them, ρ is the conductivity of the electrolyte, l is the distance between the positive and negative electrodes of the battery, and R l 0 is the liquid phase resistance per unit area.

[0058] 3) The relationship between battery capacity n and battery electrode area is shown in formula (4):

[0059]

[0060] Where k is the coating amount of active material per unit area of the electrode sheet, i.e., the surface density. Batteries of the same chemical system are usually constant or have little variation. Substituting equation (4) into equations (1)-(3) respectively, we obtain the following equations:

[0061]

[0062] (2) Establish the relationship between the Weber impedance of lithium-ion batteries and the area of the battery electrode. When AC current passes through the electrodes, the concentration of the reactive ions in the electrodes will fluctuate with the AC current, showing a phase difference, and thus producing an obstruction to the current, which is called Weber impedance. The Weber impedance of lithium-ion batteries includes oxidation Weber impedance and reduction Weber impedance, as follows: the oxidation Weber impedance and reduction Weber impedance of the positive electrode of the battery are shown in equations (5) and (6), respectively, and the oxidation Weber impedance and reduction Weber impedance of the negative electrode of the battery are shown in equations (7) and (8):

[0063] For the positive battery terminal:

[0064]

[0065] Similarly, for the negative electrode of the battery:

[0066]

[0067] (3) Establishing a characteristic parameter model of the battery system of the lithium-ion battery to determine the chemical system of the lithium-ion battery; the specific steps for establishing the characteristic parameter model of the battery system are as follows:

[0068] Step S1: According to the widely recognized equivalent circuit diagram, as shown in the attached Figure 1 As shown, the corresponding impedance formulas are listed according to the combination relationship of each device in the equivalent circuit. After sorting, the impedance formula containing all devices is obtained. After separating the real part and imaginary part of the impedance formula containing all devices, the following model of the real part R and imaginary part X of the power battery impedance is obtained:

[0069]

[0070] Step S2: Since the model parameters of the real part R and the imaginary part X of the battery impedance in step S1 are affected by the total area A of the battery electrode, the formula and Substitute the real part R and imaginary part X of the power battery impedance into the model in step S1, as follows:

[0071]

[0072] You will get:

[0073]

[0074] You will get:

[0075] From the simplified model of the real part R and imaginary part X of the power battery impedance, it can be seen that the real and imaginary part values obtained on the impedance spectrum are inversely proportional to the battery capacity and cannot be directly used to identify the battery's chemical system.

[0076] Step S3: Compare the models of the real part R and the imaginary part X of the power battery impedance simplified in step S2 to obtain the characteristic parameter model of the battery system as follows:

[0077]

[0078] It can be seen from the above formula that the characteristic parameter model of the battery system does not change with the change of the battery capacity n. 0 With X 0 If the ratio is different, the ratio of the real part R and the imaginary part X of the power battery Weber impedance will also be different, so the chemical system of the battery can be judged based on the above characteristic parameter model.

[0079] Since electrochemical impedance spectroscopy can also be used to detect the health status of batteries, this characteristic parameter is integrated into a specific device that works on the principle of electrochemical impedance spectroscopy. While detecting the battery health parameters, information about the chemical system of the power lithium-ion battery can also be obtained. This can quickly detect and evaluate the chemical system of retired power lithium-ion batteries, providing direct assistance for the secondary utilization of retired power lithium-ion batteries.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit its scope of protection. Although the present application has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading this application, those skilled in the art may still make various changes, modifications or equivalent substitutions to the specific implementation methods of the application, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the application.

Claims

1. A method for quickly identifying the chemical system of retired power lithium-ion batteries, characterized in that: The following steps are involved: (1) Establish the relationship between the capacitance, resistance, battery capacity and battery electrode area of lithium-ion batteries; (2) Establish the relationship between the Weber impedance of lithium-ion batteries and the battery electrode area; (3) Establish a characteristic parameter model of the lithium-ion battery system and determine the chemical system of the lithium-ion battery; The specific steps for establishing the characteristic parameter model of the battery system in step (3) are as follows: Step S1: Based on a widely recognized equivalent circuit diagram, models of the real part R and imaginary part X of the power battery impedance are established as follows: in, is the static internal resistance of the battery; Step S2: Substitute equations (1) to (8) into the models of the real part R and the imaginary part X of the power battery impedance, respectively, as follows: You will get: ; You will get: ; Where n is the battery capacity, is the coating amount of active material on the electrode per unit area, that is, the surface density, is the liquid phase resistance per unit area; Step S3: Compare the models of the real part R and the imaginary part X of the power battery impedance simplified in step S2 to obtain the characteristic parameter model of the battery system as follows: R of batteries with different chemical systems 0 and X 0 The ratio of is different, based on which the above characteristic parameter model can be used to identify the chemical system of the battery.

2. The method for rapidly identifying the chemical system of retired power lithium-ion batteries according to claim 1, characterized in that: The relationship between the capacitance of the lithium-ion battery and the area of the battery electrode in step (1) is shown in formula (1): （1） Where C is the capacitance of the electrode, A is the total area of the electrode, C 0 is the specific capacitance per unit area.

3. The method for rapidly identifying the chemical system of retired power lithium-ion batteries according to claim 1, characterized in that: The resistance of the lithium-ion battery in step (1) includes the battery interface reaction resistance R r and the battery's static internal resistance .

4. The method for rapidly identifying the chemical system of retired power lithium-ion batteries according to claim 3, characterized in that: The battery interface reaction resistance R r The relationship with the battery electrode area is shown in formula (2): （2） Among them, R r 0 is the reaction resistance per unit area, is the current density, and A is the total area of the electrode.

5. The method for rapidly identifying the chemical system of retired power lithium-ion batteries according to claim 3, characterized in that: The static internal resistance of the battery The relationship with the battery electrode area is shown in formula (3): = （3） Where ρ is the conductivity of the electrolyte, is the distance between the positive and negative electrodes of the battery, is the liquid phase resistance per unit area, and A is the total area of the electrode.

6. The method for rapidly identifying the chemical system of retired power lithium-ion batteries according to claim 1, characterized in that: The relationship between the battery capacity n and the battery electrode area in step (1) is shown in formula (4): （4） Where A is the total area of the electrode, It is the coating amount of active material on the electrode per unit area, that is, the surface density. Batteries with the same chemical system are usually constant or have very small changes.

7. The method for rapidly identifying the chemical system of retired power lithium-ion batteries according to claim 1, characterized in that: The Weber impedance of the lithium-ion battery in step (2) includes an oxidation Weber impedance and a reduction Weber impedance; wherein the oxidation Weber impedance and the reduction Weber impedance of the positive electrode of the battery are respectively shown in formulas (5) and (6), and the oxidation Weber impedance and the reduction Weber impedance of the negative electrode of the battery are respectively shown in formulas (7) and (8): For the positive battery terminal: (5) （6） Similarly, for the negative electrode of the battery: (7) （8）。

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