A nondestructive testing method for lithium deposition in lithium-ion batteries
By measuring the electrochemical impedance spectrum and phase angle change of lithium batteries, non-destructive testing is performed using threshold judgment method, which solves the problem of low time and accuracy of lithium-ion detection in the prior art, and achieves high-precision and low-cost analysis Lithium detection.
Patent Information
- Application Number
- CN202210954524.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-08-10
- Publication Date
- 2024-12-06
- Estimated Expiration
- 2042-08-10
AI Technical Summary
The existing lithium-ion battery lithium-ion battery detection methods have problems such as long-term, high-power and low accuracy, especially non-destructive detection methods such as measurement thickness method, differential capacity method and DC internal resistance method have high requirements for voltage and current signal accuracy, but The equipment has low accuracy and cannot accurately determine whether lithium is excreted.
By measuring the electrochemical impedance spectrum of the lithium battery to be tested and the fresh lithium battery of the same model, calculating the phase angle change amount at different frequencies, using the threshold judgment method for non-destructive testing, establishing a relationship chart of frequency and angular change amounts, and judging the lithium analysis phenomenon.
It realizes lithium-ion battery lithium-ion battery non-destructive testing with simple operation, short time and high accuracy, avoids secondary damage to lithium batteries and reduces detection time and cost.
Smart Images
Figure CN115267583B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium deposition detection of lithium batteries, and in particular to a nondestructive detection method for lithium deposition of lithium ion batteries. Background Art
[0002] Lithium-ion batteries have been widely used in electric vehicles, grid energy storage, aerospace and other fields due to their high specific energy density, high coulomb efficiency and low production cost. When lithium-ion batteries are charged at low temperatures or at high rates, a large amount of lithium metal is easily precipitated on the negative electrode surface. This phenomenon is generally referred to as lithium precipitation. Lithium precipitation has a great impact on the life and safety of lithium-ion batteries. First, lithium precipitation reduces the available lithium in lithium-ion batteries and causes the battery capacity to decay. Second, the precipitated lithium metal reacts easily with the electrolyte, causing the battery to produce gas or other side reactions. Third, the lithium metal on the negative electrode surface may generate lithium dendrites on the surface. Further growth of lithium dendrites can easily puncture the diaphragm, causing an internal short circuit in the battery. Therefore, lithium precipitation research has become an indispensable part of battery safety research.
[0003] At present, the commonly used lithium plating detection methods can be divided into the following two categories:
[0004] Destructive testing: Disassemble the battery and observe the surface morphology of the negative electrode to determine whether the battery has lithium deposition. Although this method is simple, it consumes a lot of manpower and material resources.
[0005] Nondestructive testing: Common methods include thickness measurement, differential capacity method, DC internal resistance method, etc.; the reason for the change of battery thickness is not only lithium deposition, gas production, electrolyte drying and electrode expansion have a greater impact on battery thickness, and the thickness measurement method has a large error; the differential capacity method and DC internal resistance method have high requirements on the accuracy of voltage and current signal acquisition. Ordinary charging and discharging equipment has low accuracy and cannot accurately determine whether lithium deposition has occurred. Summary of the invention
[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a non-destructive detection method for lithium deposition in lithium ion batteries which is simple to operate, short in time and high in accuracy.
[0007] The purpose of the present invention can be achieved by the following technical solutions:
[0008] The present invention provides a nondestructive detection method for lithium deposition in lithium-ion batteries. The method measures the electrochemical impedance of a lithium battery to be tested and a fresh lithium battery of the same model respectively to calculate the phase angle variation of the two at different frequencies, and adopts a threshold-based judgment method to perform nondestructive detection on lithium deposition in the lithium battery to be tested.
[0009] Preferably, the method comprises the following steps:
[0010] Step S1, under set temperature conditions, obtaining an electrochemical impedance spectrum of a fresh lithium battery of the same model as the battery to be tested at a set state of charge, and obtaining the phase angle of the fresh lithium battery at different frequencies;
[0011] Step S2, under the same temperature condition, measuring the electrochemical impedance spectrum of the lithium battery to be tested, and obtaining the phase angle of the lithium battery to be tested at different frequencies; wherein the excitation signal of the lithium battery to be tested is consistent with the excitation signal of the fresh lithium battery;
[0012] Step S3, subtracting the phase angle of the lithium battery to be tested from the phase angle of the fresh lithium battery at the same frequency, and establishing a relationship diagram between frequency and angle change;
[0013] Step S4: Based on the threshold value of the phase angle change in the set frequency interval, non-destructive testing is performed on the lithium deposition of the lithium battery to be tested.
[0014] Preferably, the set state of charge in step S1 is any state of charge in the range of 0% SOC to 100% SOC.
[0015] Preferably, the set temperature condition in step S1 is a normal temperature condition.
[0016] Preferably, the range of the different frequencies in step S2 is 20 kHz to 0.05 Hz.
[0017] Preferably, the set frequency interval in step S4 is 10 kHz to 0.01 Hz.
[0018] Preferably, the excitation signal in step S2 is a sinusoidal potential or a sinusoidal current.
[0019] Preferably, step S4 is specifically as follows: obtaining the maximum value of the phase angle variation and the frequency corresponding to the maximum value in the frequency and angle variation relationship diagram; when the phase angle variation at the lowest point is greater than a set phase angle variation threshold, lithium deposition occurs in the lithium battery to be tested at this frequency.
[0020] Compared with the prior art, the present invention has the following advantages:
[0021] The present invention determines lithium deposition by testing the electrochemical impedance spectrum of the lithium-ion battery and comparing the change of the characteristic frequency phase angle. This method will not cause secondary damage to the lithium-ion battery and solves the dependence of the test method on high-precision test equipment. The test time is short and the accuracy is high, which can greatly reduce the detection time and cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 is a flow chart of the method of the present invention;
[0023] Figure 2is a frequency-phase angle relationship diagram in Examples 1 to 4;
[0024] Figure 3 Schematic diagram of disassembly of lithium battery pole pieces in Examples 1 to 4. DETAILED DESCRIPTION
[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.
[0026] like Figure 1 As shown, the present invention provides a nondestructive detection method for lithium deposition in lithium-ion batteries, comprising the following steps:
[0027] 1) First, at room temperature, use an electrochemical workstation to obtain the electrochemical impedance spectrum of a fresh lithium battery of the same model as the battery to be tested. The state of charge can be any SOC state from 0% SOC to 100% SOC, the measurement frequency range is 10kHz to 0.01Hz, and the excitation is sinusoidal potential or current;
[0028] 2) At room temperature, the battery to be tested is subjected to an electrochemical impedance test, with the state of charge ranging from 0% SOC to 100% SOC, the measurement frequency range is 10kHz to 0.01Hz, and the excitation signal is consistent with that of a fresh lithium battery;
[0029] 3) Compare the phase angles of the battery to be tested and the fresh lithium battery at the same state of charge. When comparing the phase angles, the frequencies of the two batteries are kept consistent, and the frequency and phase angle changes of the battery to be tested are obtained;
[0030] 4) Select the relationship diagram between the characteristic frequency of 20 Hz to 0.05 Hz and the phase angle change to determine the lithium deposition, specifically: obtain the maximum value of the phase angle change and the frequency corresponding to the maximum value in the relationship diagram between the characteristic frequency of 20 Hz to 0.05 Hz and the phase angle change. When the phase angle change at the lowest point is greater than the set phase angle change threshold, the lithium deposition phenomenon occurs in the lithium battery to be tested at this frequency.
[0031] Example 1
[0032] Take the battery under test with a state of charge of 100% SOC and a fresh lithium battery of the same model, and excite the battery from a high frequency of 10kHz to a low frequency of 0.01Hz at a current of 2A at 25°C to obtain the electrochemical impedance spectrum of the battery, which contains the relationship between frequency and phase angle;
[0033] like Figure 2 The relationship between the frequency and phase angle change of the battery under test and the fresh lithium battery is shown in the figure. The phase angle changes the most at a frequency of 1 Hz, which is -3.4°.
[0034] When the battery was disassembled later, no lithium deposition was found on the negative electrode surface.
[0035] Example 2
[0036] Take the battery under test with a state of charge of 0% SOC and a fresh lithium battery of the same model, and excite the battery from a high frequency of 10kHz to a low frequency of 0.01Hz at a current of 2.8A at 25℃ to obtain the electrochemical impedance spectrum of the battery, which contains the relationship between frequency and phase angle;
[0037] The relationship between the frequency and phase angle change of the battery to be tested is shown in the figure below: Figure 2 As shown, the phase angle changes the most at a frequency of 1 Hz, which is -5.2°;
[0038] When the battery was disassembled, no lithium deposition was found on the surface of the negative electrode of the battery.
[0039] Example 3
[0040] Take the battery under test with a state of charge of 50% SOC and a fresh lithium battery of the same model, and excite the battery from a high frequency of 10kHz to a low frequency of 0.01Hz at a current of 2.5A at 25℃ to obtain the electrochemical impedance spectrum of the battery, which contains the relationship between frequency and phase angle;
[0041] The relationship between frequency and phase angle change is shown in the figure Figure 2 As shown, the phase angle changes the most at a frequency of 2 Hz, which is -10°;
[0042] After disassembling the battery, it was found that a small amount of lithium was deposited locally on the surface of the negative electrode of the battery.
[0043] Example 4
[0044] Take the battery under test with a state of charge of 0% SOC and a fresh lithium battery of the same model, and excite the battery from a high frequency of 10kHz to a low frequency of 0.01Hz at a current of 2.5A at 25℃ to obtain the electrochemical impedance spectrum of the battery, which contains the relationship between frequency and phase angle;
[0045] The relationship between frequency and phase angle change is shown in the figure Figure 2 As shown, the phase angle changes the most at a frequency of 1 Hz, which is -13°;
[0046] When the battery was disassembled, it was found that there was an obvious area of lithium deposition on the surface of the negative electrode of the battery.
[0047] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.
Claims
1. A nondestructive testing method for lithium deposition in lithium-ion batteries, characterized in that: The method measures the electrochemical impedance of the lithium battery to be tested and a fresh lithium battery of the same model respectively to calculate the phase angle change of the two at different frequencies, and adopts a threshold-based judgment method to perform non-destructive detection of lithium plating in the lithium battery to be tested. The method comprises the following steps: Step S1, under set temperature conditions, obtaining an electrochemical impedance spectrum of a fresh lithium battery of the same model as the battery to be tested at a set state of charge, and obtaining the phase angle of the fresh lithium battery at different frequencies; Step S2, under the same temperature condition, measuring the electrochemical impedance spectrum of the lithium battery to be tested, and obtaining the phase angle of the lithium battery to be tested at different frequencies; wherein the excitation signal of the lithium battery to be tested is consistent with the excitation signal of the fresh lithium battery; Step S3, subtracting the phase angle of the lithium battery to be tested from the phase angle of the fresh lithium battery at the same frequency, and establishing a relationship diagram between frequency and angle change; Step S4: Based on the threshold value of the phase angle change in the set frequency interval, non-destructive testing is performed on the lithium deposition of the lithium battery to be tested.
2. A lithium ion battery lithium deposition nondestructive testing method according to claim 1, characterized in that: The set state of charge in step S1 is any state of charge in the range of 0% SOC to 100% SOC.
3. A lithium ion battery lithium plating nondestructive testing method according to claim 1, characterized in that: The set temperature condition in step S1 is a normal temperature condition.
4. A lithium ion battery lithium plating nondestructive testing method according to claim 1, characterized in that: The range of the different frequencies in step S2 is 20 kHz to 0.05 Hz.
5. A lithium ion battery lithium deposition nondestructive testing method according to claim 4, characterized in that: The frequency interval in step S4 is set to be 10 kHz to 0.01 Hz.
6. A lithium ion battery lithium plating nondestructive testing method according to claim 1, characterized in that: The excitation signal in step S2 is a sinusoidal potential or a sinusoidal current.
7. A lithium ion battery lithium plating nondestructive testing method according to claim 1, characterized in that: The step S4 is specifically as follows: obtaining the maximum phase angle variation and the frequency corresponding to the maximum phase angle variation in the frequency and angle variation relationship diagram; when the phase angle variation at the lowest point is greater than the set phase angle variation threshold, lithium deposition occurs in the lithium battery to be tested at this frequency.