Measurement method for accelerated calorimeter test based on in-situ electrochemical impedance spectroscopy

Abstract

The invention discloses a measurement method for accelerated calorimeter test based on in-situ electrochemical impedance spectroscopy. The measurement method comprises the following steps: applying excitation current to a battery to be detected; measuring the battery to be detected under the current condition through the EIS module to obtain real part impedance and imaginary part impedance under different frequencies; determining phase angles and impedances under different frequencies according to the real part impedances and the imaginary part impedances under different frequencies; the voltage of the battery to be detected at different surface temperatures is collected through the ARC module, and the corresponding temperature rise rate is determined; determining an impedance modulus deviation, a phase deviation, a voltage sharp change deviation and a temperature rise rate deviation according to the phase angles and the impedances under the different frequencies, the voltages under the different surface temperatures and the corresponding temperature rise rates, and generating an error signal; generating a corresponding sampling rate control instruction according to the error signal based on dynamic PID control; and the ARC module adjusts the sampling frequency according to the sampling rate control instruction so as to perform high-precision measurement.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of accelerated rate calorimeter test, and particularly relates to a measurement method for accelerated rate calorimeter test based on in-situ electrochemical impedance spectroscopy. BACKGROUND

[0002] The ARC device is arranged with heating blocks on the top, sidewall and bottom respectively, and the power of the heating blocks is controlled through feedback point temperature closed loop, so as to realize the adiabatic tracking of the battery temperature. Since the temperature change rate of the battery after thermal runaway is usually more than 10℃ per second, if the sampling rate is low, the measured values of the peak temperature and the maximum temperature rise rate will be low. However, since the test duration is usually more than 80h, if high-frequency sampling is used for a long time, the load pressure of the device will be increased. SUMMARY

[0003] Therefore, the main purpose of the present application is to provide a measurement method for accelerated rate calorimeter test based on in-situ electrochemical impedance spectroscopy.

[0004] To achieve the above purpose, the technical scheme of the present application is as follows:

[0005] A measurement method for accelerated rate calorimeter test based on in-situ electrochemical impedance spectroscopy, the method is as follows:

[0006] An excitation current with a frequency of 0.1Hz-5kHz and an amplitude of 0.1C is applied to the battery to be detected;

[0007] The in-situ electrochemical impedance spectroscopy (EIS) module is used to measure the battery to be detected under the current condition, and the real part impedance Z Re and the imaginary part impedance Z Im under different frequencies are obtained;

[0008] The phase angle θ and the impedance Z under different frequencies are determined according to the real part impedance Z Re and the imaginary part impedance Z Im under different frequencies;

[0009] The voltage V of the battery to be detected under different surface temperatures T is collected by the accelerated rate calorimeter (ARC) module, and the corresponding temperature rise rate dT / dt is determined;

[0010] The impedance modulus deviation Δ|Z|, the phase deviation Δθ, the voltage sharp change deviation ΔV and the temperature rise rate deviation

[0011] The impedance modulus deviation Δ|Z|, the phase deviation Δθ, the voltage sharp change deviation ΔV and the temperature rise rate deviation are fused to generate an error signal E(t);

[0012] Based on dynamic PID control, a corresponding sampling rate control command is generated according to the error signal E(t);

[0013] The ARC module adjusts the sampling frequency according to the sampling rate control command to perform high-precision measurements.

[0014] In the above scheme, the step of determining the real part impedance Z at different frequencies... Re and imaginary impedance Z Im Determining the phase angle θ and impedance Z at different frequencies specifically includes:

[0015] The real part impedance Z at different frequencies Re and imaginary impedance Z Im according to Obtain the impedance Z, where R0 is the ohmic resistance, R ct and C dl These are the charge transfer impedance and the double-layer capacitance, respectively, and ω is the angular frequency;

[0016] The real part impedance Z at different frequencies Re and imaginary impedance Z Im According to θ = arctan -1 (-Z Im / Z Re The phase angle θ is obtained.

[0017] In the above scheme, the impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharp change deviation ΔV, and temperature rise rate deviation are determined based on the phase angle θ and impedance Z at different frequencies, the voltage V at different surface temperatures T, and the corresponding temperature rise rate dT / dt. Previously, this method also included: performing dynamic baseline calibration on the impedance modulus deviation Δ|Z| and phase deviation Δθ to obtain the impedance modulus reference |Z|. bastline Phase reference θ bastline .

[0018] In the above scheme, dynamic baseline calibration is performed on the impedance modulus deviation Δ|Z| and phase deviation Δθ to obtain the impedance modulus reference |Z|. bastline Phase reference θ bastline Specifically, it includes:

[0019] Based on the fitted value y k =at k +b and minimizing the sum of squared residuals Determine the fitted slope α.

[0020] If the fitting slope a of the current impedance modulus deviation Δ|Z| or phase deviation Δθ satisfies |a| < threshold a th Once the battery under test is determined to be in a stable state, the current impedance modulus deviation Δ|Z| or phase deviation Δθ is updated to the corresponding baseline value.

[0021] If the fitting slope a of the current impedance modulus deviation Δ|Z| or phase deviation Δθ satisfies |a| greater than or equal to the threshold a th If the battery under test is determined to be in an unstable state, the corresponding baseline value is updated using the previous impedance modulus deviation Δ|Z| or phase deviation Δθ.

[0022] In the above scheme, the impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharp change deviation ΔV, and temperature rise rate deviation are determined based on the phase angle θ and impedance Z at different frequencies, the voltage V at different surface temperatures T, and the corresponding temperature rise rate dT / dt. Specifically, it includes:

[0023] The impedance Z at different frequencies is based on Determine the impedance modulus deviation Δ|Z|;

[0024] The phase angle θ at different frequencies is based on Determine the phase deviation Δθ;

[0025] The voltage V at different surface temperatures T is based on Determine the voltage sharp change deviation ΔV;

[0026] The temperature rise rate dT / dt is based on Determine the temperature rise rate deviation

[0027] In the above scheme, the impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharp change deviation ΔV, and temperature rise rate deviation are... The fusion process generates an error signal E(t), specifically including: based on E(t) = ω1x |Z| +ω2x |θ| +ω3x |V| +ω4x |T| +ω2x dT / dt Combined impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharp change deviation ΔV, and temperature rise rate deviation Obtain the error signal E(t); where ω1, ω2, ω3, ω4, and ω5 are weighting coefficients.

[0028] In the above scheme, the step of generating a corresponding sampling rate control command based on the error signal E(t) according to dynamic PID control specifically includes: based on... Determine the corresponding sampling rate control command.

[0029] In the above scheme, the ARC module adjusts the sampling frequency according to the sampling rate control command to perform high-precision measurement. Specifically, this includes adjusting the sampling frequency F when u(t) < 0.3. s (t) to 1Hz; when 0.3≤u(t)<0.7, adjust the sampling frequency F. s (t) to 10Hz; when 0.7≤u(t)<0.9, adjust the sampling frequency F. s (t) to 100Hz; when u(t)≥0.7, adjust the sampling frequency F s (t) up to 1000Hz.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention reduces equipment load while ensuring accurate detection of temperature changes during battery thermal runaway by matching different sampling rates to the battery status. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and, together with their descriptions, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0033] Figure 1 This is a schematic diagram of the structure of an accelerated calorimeter test method based on in-situ electrochemical impedance spectroscopy provided in an embodiment of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0035] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, article, or apparatus that includes that element.

[0036] This invention provides a measurement method for accelerated calorimetry based on in-situ electrochemical impedance spectroscopy, such as... Figure 1 As shown, the method is as follows:

[0037] Step 101: Apply an excitation current of 0.1Hz-5kHz with an amplitude of 0.1C to the cell under test;

[0038] Step 102: Measure the real impedance Z of the battery under test under the current conditions using an in-situ electrochemical impedance spectroscopy (EIS) module to obtain the real impedance Z at different frequencies. Re and imaginary impedance Z Im ;

[0039] Step 103: Based on the real impedance Z at different frequencies Re and imaginary impedance Z Im Determine the phase angle θ and impedance modulus |Z| at different frequencies;

[0040] Specifically, the real part impedance Z at different frequencies Re and imaginary impedance Z Im according to Obtain the impedance Z, where R0 is the battery internal resistance obtained from EIS testing, and R ct and C dl These are the charge transfer impedance and the double-layer capacitance, respectively, and ω is the angular frequency;

[0041] according to Obtain the impedance modulus |Z|.

[0042] The real part impedance Z at different frequencies Re and imaginary impedance Z Im According to θ = arctan -1 (-Z Im / Z Re The phase angle θ is obtained.

[0043] Step 104: Collect the voltage V of the battery under test at different surface temperatures T using the accelerated calorimeter (ARC) module, and determine the corresponding temperature rise rate dT / dt;

[0044] Step 105: Filter the impedance, voltage, phase, and temperature data points;

[0045] Specifically, regarding the time window Assuming the signal follows a linear trend, we construct a linear model using the impedance, voltage, phase, and temperature data points within the data set.

[0046] y(t) = at + b

[0047] Where a is the slope (reflecting the rate of change of the parameter) and b is the intercept.

[0048] By minimizing the sum of squared residuals Solving for the coefficients:

[0049]

[0050] Filtered output: using the fitted value y k =at k +b is used as the denoised signal value to replace the original data y. k .

[0051] Step 106: Determine the impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharpness deviation ΔV, and temperature rise rate deviation based on the phase angle θ and impedance Z at different frequencies after filtering, the voltage V at different surface temperatures T, and the corresponding temperature rise rate dT / dt.

[0052] Specifically, dynamic baseline calibration is performed on the impedance modulus deviation Δ|Z| and phase deviation Δθ to obtain the impedance modulus reference |Z|. bastline Phase reference θ bastline .

[0053] In other words, based on the fitted value y k =at k +b and minimizing the sum of squared residuals Determine the fitted slope α.

[0054] If the fitting slope a of the current impedance modulus deviation Δ|Z| or phase deviation Δθ satisfies |a| < threshold a th Once the battery under test is determined to be in a stable state, the current impedance modulus deviation Δ|Z| or phase deviation Δθ is updated to the corresponding baseline value.

[0055] If the fitting slope a of the current impedance modulus deviation Δ|Z| or phase deviation Δθ satisfies |a| greater than or equal to the threshold a th If the battery under test is determined to be in an unstable state, the corresponding baseline value is updated using the previous impedance modulus deviation Δ|Z| or phase deviation Δθ.

[0056] Then, based on the impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharpness deviation ΔV, and temperature rise rate deviation updated to the baseline value... Determine the deviation value.

[0057] The impedance Z at different frequencies is based on Determine the impedance modulus deviation Δ|Z|;

[0058] The phase angle θ at different frequencies is based on Determine the phase deviation Δθ;

[0059] The voltage V at different surface temperatures T is based on Determine the voltage sharp change deviation ΔV;

[0060] The temperature rise rate dT / dt is based on Determine the temperature rise rate deviation

[0061] Where Δt is the sampling interval and t is time.

[0062] Step 107: Calculate the impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharp change deviation ΔV, and temperature rise rate deviation. The signals are fused together to generate an error signal E(t);

[0063] Specifically, according to E(t)=ω1x |Z| +ω2x |θ| +ω3x |V| +ω4x |T| +ω2x dT / dt Combined impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharp change deviation ΔV, and temperature rise rate deviation Obtain the error signal E(t); where ω1, ω2, ω3, ω4, and ω5 are weighting coefficients.

[0064] Step 108: Based on dynamic PID control, generate the corresponding sampling rate control command according to the error signal E(t);

[0065] Specifically, according to Determine the corresponding sampling rate control command.

[0066] Step 109: The ARC module adjusts the sampling frequency according to the sampling rate control command to perform high-precision measurement.

[0067] Specifically, when u(t) < 0.3, the internal state of the battery is stable and slow, and the rate of change of battery voltage and temperature is small. At this time, the sampling frequency F is adjusted. s (t) to 1Hz; when 0.3≤u(t)<0.7, as the temperature rises, side reactions gradually occur inside the battery. At this point, the battery's self-generated heat temperature T1 is approached, so the sampling frequency F is adjusted. s The sampling frequency was adjusted to 10 Hz to accurately record the temperature during battery self-heating. When 0.7 ≤ u(t) < 0.9, the battery temperature rise rate exceeded 0.02℃ / min, the internal side reactions of the battery intensified, and the battery was close to thermal runaway. At this time, in order to accurately record the thermal runaway initiation temperature, the sampling frequency F was adjusted. s (t) up to 100Hz; when u(t)≥0.7, the battery thermally runs away, and the temperature rise rate increases sharply. At this time, in order to accurately record the peak temperature of thermal runaway and the maximum temperature rise rate, the sampling frequency F is adjusted. s (t) up to 1000Hz.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention.

Claims

1. A measurement method for accelerated calorimetry based on in-situ electrochemical impedance spectroscopy, characterized in that, The method is as follows: An excitation current of 0.1Hz-5kHz with an amplitude of 0.1C is applied to the cell under test. The real impedance Z at different frequencies was obtained by measuring the battery under test under the current conditions using an in-situ electrochemical impedance spectroscopy (EIS) module. Re and imaginary impedance Z Im ; Based on the real impedance Z at different frequencies Re and imaginary impedance Z Im Determine the phase angle θ and impedance Z at different frequencies; The voltage V of the battery under test is collected at different surface temperatures T using an accelerated calorimeter (ARC) module, and the corresponding temperature rise rate dT / dt is determined. The impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharpness deviation ΔV, and temperature rise rate deviation are determined based on the phase angle θ and impedance Z at different frequencies, the voltage V at different surface temperatures T, and the corresponding temperature rise rate dT / dt. The impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharp change deviation ΔV, and temperature rise rate deviation are included. The signals are fused to generate an error signal E(t); Based on dynamic PID control, a corresponding sampling rate control command is generated according to the error signal E(t); The ARC module adjusts the sampling frequency according to the sampling rate control command to perform high-precision measurements.

2. The measurement method for accelerated calorimetry based on in-situ electrochemical impedance spectroscopy according to claim 1, characterized in that, The real part impedance Z at different frequencies is used as a basis Re and imaginary impedance Z Im Determining the phase angle θ and impedance Z at different frequencies specifically includes: The real part impedance Z at different frequencies Re and imaginary impedance Z Im according to Obtain the impedance Z, where R0 is the ohmic resistance, R ct and C dl These are the charge transfer impedance and the double-layer capacitance, respectively, and ω is the angular frequency; The real part impedance Z at different frequencies Re and imaginary impedance Z Im According to θ = arctan -1 (-Z Im / Z Re The phase angle θ is obtained.

3. The measurement method for accelerated calorimetry based on in-situ electrochemical impedance spectroscopy according to claim 1 or 2, characterized in that, The impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharpness deviation ΔV, and temperature rise rate deviation are determined based on the phase angle θ and impedance Z at different frequencies, the voltage V at different surface temperatures T, and the corresponding temperature rise rate dT / dt. Previously, this method also included: performing dynamic baseline calibration on the impedance modulus deviation Δ|Z| and phase deviation Δθ to obtain the impedance modulus reference |Z|. bastline Phase reference θ bastline .

4. The measurement method for accelerated calorimetry based on in-situ electrochemical impedance spectroscopy according to claim 3, characterized in that, The impedance modulus deviation Δ|Z| and phase deviation Δθ are dynamically baseline calibrated to obtain the impedance modulus reference |Z|. bastline Phase reference θ bastline Specifically, it includes: Based on the fitted value y k =at k +b and minimizing the sum of squared residuals Determine the fitted slope α. If the fitting slope a of the current impedance modulus deviation Δ|Z| or phase deviation Δθ satisfies |a| < threshold a th Once the battery under test is determined to be in a stable state, the current impedance modulus deviation Δ|Z| or phase deviation Δθ is updated to the corresponding baseline value. If the fitting slope a of the current impedance modulus deviation Δ|Z| or phase deviation Δθ satisfies |a| greater than or equal to the threshold a th If the battery under test is determined to be in an unstable state, the corresponding baseline value is updated using the previous impedance modulus deviation Δ|Z| or phase deviation Δθ.

5. The measurement method for accelerated calorimetry based on in-situ electrochemical impedance spectroscopy according to claim 4, characterized in that, The impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharpness deviation ΔV, and temperature rise rate deviation are determined based on the phase angle θ and impedance Z at different frequencies, the voltage V at different surface temperatures T, and the corresponding temperature rise rate dT / dt. Specifically, it includes: The impedance Z at different frequencies is based on Determine the impedance modulus deviation Δ|Z|; The phase angle θ at different frequencies is based on Determine the phase deviation Δθ; The voltage V at different surface temperatures T is based on Determine the voltage sharp change deviation ΔV; The temperature rise rate dT / dt is based on Determine the temperature rise rate deviation 6. The measurement method for accelerated calorimetry based on in-situ electrochemical impedance spectroscopy according to claim 5, characterized in that, The impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharp change deviation ΔV, and temperature rise rate deviation are respectively... The fusion process generates an error signal E(t), specifically including: based on E(t) = ω1x |Z| +v2x |θ| +ω3x |V| +ω4x |T| +ω2x dT / dt Combined impedance modulus deviation Δ|Z|, phase deviation Δθ, voltage sharp change deviation ΔV, and temperature rise rate deviation Obtain the error signal E(t); where ω1, ω2, ω3, ω4, and ω5 are weighting coefficients.

7. The measurement method for accelerated calorimetry based on in-situ electrochemical impedance spectroscopy according to claim 6, characterized in that, The dynamic PID control generates a corresponding sampling rate control command based on the error signal E(t), specifically including: based on... Determine the corresponding sampling rate control command.

8. The measurement method for accelerated calorimetry based on in-situ electrochemical impedance spectroscopy according to claim 7, characterized in that, The ARC module adjusts the sampling frequency according to the sampling rate control command to perform high-precision measurements. Specifically, when u(t) < 0.3, the sampling frequency F is adjusted. s (t) to 1Hz; when 0.3≤u(t)<0.7, adjust the sampling frequency F. s (t) to 10Hz; when 0.7≤u(t)<0.9, adjust the sampling frequency F. s (t) to 100Hz; when u(t)≥0.7, adjust the sampling frequency F s (t) up to 1000Hz.

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