Lithium battery electrolyte infiltration detection system and method based on laser ultrasound

Abstract

The application provides a lithium battery electrolyte infiltration detection system and method, and relates to the field of battery detection. The detection system comprises: a laser excitation device for outputting pulsed laser; a laser ultrasonic shaping device; a detection device for acquiring ultrasonic signals generated by a lithium battery sample under the action of pulsed laser, and determining the electrolyte infiltration state of the lithium battery sample based on the ultrasonic signals; and a battery displacement platform for carrying the lithium battery sample and for allowing pulsed laser to act on different positions of the lithium battery sample. The detection device is also used to acquire the first wave flight time of pulsed laser output by the laser excitation device and the ultrasonic signals generated by the lithium battery sample. The laser ultrasonic shaping device is used to adjust the energy uniformity of pulsed laser based on the difference between the first wave flight time of the ultrasonic signals and a reference time, and to allow pulsed laser to act on different positions of the lithium battery with the same central energy intensity. The accuracy of the infiltration detection is improved.

Description

Technical Field

[0001] This invention relates to the field of battery testing, and in particular to a lithium battery electrolyte wetting detection system and method based on ultrasonic laser. Background Technology

[0002] The failure mechanism of energy storage batteries is intricately coupled with various material structural parameters, and their performance degradation process is often driven by multiple factors. Therefore, high-precision detection of relevant characterization parameters and failure mechanism analysis have always been key challenges in this field. To meet the application requirements of energy storage batteries, such as internal defect identification, electrolyte wetting behavior assessment, and rapid early warning of battery faults, a detection method that can balance high precision and rapid response is urgently needed.

[0003] Lasers can be used to excite battery samples to generate corresponding ultrasonic signals, thereby detecting the degree of electrolyte wetting based on the ultrasonic signals. However, the detection accuracy of related electrolyte detection systems is relatively low. Summary of the Invention

[0004] This invention provides a lithium battery electrolyte wetting detection system and method, which improves the accuracy of electrolyte wetting detection by using feedback adjustment to make pulsed laser act on each position of the lithium battery sample with uniform intensity.

[0005] A first aspect of this invention provides a lithium battery electrolyte wetting detection system, comprising: a laser excitation device for outputting pulsed laser light; a laser ultrasonic shaping device for adjusting the uniformity of the pulsed laser excitation energy; a detection device for acquiring ultrasonic signals generated by the lithium battery sample under the action of the pulsed laser, and determining the electrolyte wetting state of the lithium battery sample based on the ultrasonic signals; and a battery displacement platform for carrying the lithium battery sample, for applying the pulsed laser light to different positions of the lithium battery sample; wherein the detection device is further configured to acquire the first-wave flight time of the pulsed laser light output by the laser excitation device and the ultrasonic signal generated by the lithium battery sample, and the laser ultrasonic shaping device is configured to adjust the energy uniformity of the pulsed laser light based on the difference between the first-wave flight time and the reference flight time of the ultrasonic signal, and to apply the pulsed laser light to different positions of the lithium battery with the same central energy intensity.

[0006] In some embodiments, the laser ultrasound shaping device includes a microlens array.

[0007] In some embodiments, the lithium battery electrolyte wetting detection system further includes: a microscope objective, located between the laser ultrasonic shaping device and the lithium battery sample, for focusing the pulsed laser onto the lithium battery sample; a dichroic mirror, located between the laser ultrasonic shaping device and the lithium battery sample, for transmitting the pulsed laser and receiving and reflecting light reflected from the lithium battery surface; and a focal length detection component, for receiving the light emitted from the dichroic mirror and converting the light signal into a detection signal; wherein the moving device adjusts the distance between the lithium battery sample and the microscope objective based on the detection signal output by the focal length detection component.

[0008] In some embodiments, the focal length detection component includes a photomultiplier tube for converting the received optical signal into an electrical signal.

[0009] In some embodiments, the lithium battery electrolyte wetting detection system further includes a confocal plate located between the dichroic mirror and the photomultiplier tube, the confocal plate having a probe hole, and light emitted from the dichroic mirror passing through the probe hole and directed towards the photomultiplier tube.

[0010] In some embodiments, the detection device includes: an ultrasonic probe for acquiring ultrasonic signals output from a lithium battery sample; a digital acquisition card for converting the ultrasonic signals into digital signals; and a computer for processing the digital signals.

[0011] The second aspect of this invention provides a method for detecting electrolyte wetting in lithium batteries. This method is implemented using the detection system provided in the first aspect of the aforementioned embodiments. The method includes: step S101, controlling the laser emitting device to output laser light and recording the laser excitation time node; step S102, continuously exciting multiple laser ultrasonic signals at the same detection location and acquiring the first-wave flight time of the ultrasonic signal corresponding to each excitation, calculating a consistency index of the first-wave flight time based on the first-wave flight time sequence; and performing feedback adjustment on the laser ultrasonic shaping device according to the consistency index of the first-wave flight time to improve the consistency of laser excitation conditions at the detection location; step S103, acquiring ultrasonic signal data by the detection device and extracting characteristic parameters for characterizing the electrolyte wetting state; step S104, controlling the battery displacement platform to apply the laser to different positions of the lithium battery sample, repeating step S103 at each position until ultrasonic signal data at each position of the lithium battery sample is obtained, and obtaining the electrolyte wetting state of the lithium battery sample based on the ultrasonic signal data.

[0012] In some embodiments, the laser excitation device is controlled to excite multiple pulsed lasers and apply the multiple pulsed lasers to the lithium battery sample to obtain the first-wave flight time of each excited pulsed laser. The average of the first-wave flight times of each excited pulsed laser is used as a reference time, which is used to evaluate the consistency index of the first-wave flight time.

[0013] In some embodiments, the lithium battery electrolyte wetting detection system further includes a photomultiplier tube and a microscope objective; between step S102 and step S103, the lithium battery electrolyte wetting detection method further includes: acquiring an electrical signal by the photomultiplier tube; controlling the battery displacement platform to adjust the distance between the lithium battery sample and the microscope objective until the electrical signal reaches its maximum value.

[0014] In some embodiments, the lithium battery electrolyte wetting detection system further includes a photomultiplier tube and a microscope objective; between steps S102 and S103, the lithium battery electrolyte wetting detection method further includes: acquiring an electrical signal by the photomultiplier tube and acquiring the amplitude of the first ultrasonic peak by the detection device; calculating a weighted sum of the peak value of the electrical signal and the amplitude of the first ultrasonic peak to obtain a focal length evaluation index; controlling the battery displacement platform to adjust the distance between the lithium battery sample and the microscope objective until the focal length evaluation index reaches its maximum value.

[0015] This invention provides a lithium battery electrolyte wetting detection system. The system includes a laser emitting device for outputting pulsed laser light, a battery displacement platform connected to the lithium battery sample and enabling the pulsed laser to act on different positions of the sample, and an ultrasonic signal generated at each position of the lithium battery sample under pulsed laser excitation. The ultrasonic signals generated at each position of the lithium battery sample under pulsed laser excitation, acquired by the detection device, can determine the electrolyte wetting state of the lithium battery sample. Simultaneously, the system also includes a laser ultrasonic shaping device. The laser ultrasonic shaping device is adjusted based on the first-wave time-of-flight shift as an evaluation criterion for laser intensity, ensuring uniform pulsed laser intensity acting on different positions of the lithium battery sample, thereby improving the accuracy of lithium battery electrolyte wetting detection. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a lithium battery electrolyte wetting detection system provided in an embodiment of the present invention; Figure 2 A schematic diagram of another lithium battery electrolyte wetting detection system is provided for embodiments of the present invention; Figure 3 A schematic diagram of a detection device in a lithium battery electrolyte wetting detection system is provided for embodiments of the present invention; Figure 4 A schematic diagram of another lithium battery electrolyte wetting detection system is provided for embodiments of the present invention; Figure 5 A schematic flowchart of the first lithium battery electrolyte wetting detection method provided in an embodiment of the present invention; Figure 6 A schematic flowchart of the second lithium battery electrolyte wetting detection method provided in this embodiment of the invention; Figure 7 This is a flowchart illustrating the third lithium battery electrolyte wetting detection method provided in this embodiment of the invention.

[0017] Explanation of reference numerals in the attached figures 50. Laser excitation device; 30. Detection device; 31. Ultrasonic probe; 32. Data acquisition card; 33. Computer; 34. Dual-wave mixer interferometer; 40. Battery displacement platform; 70. Focal length detection assembly; 80. Confocal plate; 81. Detection pinhole; 1. Pulsed laser; 2. Concave lens; 3. Convex lens; 4. Laser ultrasonic shaping device; 5. Dichroic mirror; 6. Aperture; 7. Microscope objective; 8. Lithium battery sample; 9. Battery displacement platform; 10. Ultrasonic probe; 11. Two-wave mixing interferometer; 12. Digital acquisition card; 13. Computer; 14. Digital signal generator; 15. Focusing lens; 16. CMOS camera. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] The specific technical features described in the various embodiments in the detailed implementation can be combined in various ways without contradiction. For example, different implementation methods can be formed by combining different specific technical features. In order to avoid unnecessary repetition, the various possible combinations of the specific technical features in this invention will not be described separately.

[0020] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0021] Additionally, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, 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, method, article, or apparatus. In the following description, the terms "first," "second," etc., are used merely to distinguish different objects and do not indicate any similarity or connection between them. It should be understood that the directional descriptions such as "above," "below," "inside," and "outside" refer to the orientation under normal use conditions.

[0022] In some embodiments, such as Figure 1 As shown, the lithium battery electrolyte wetting detection system includes: a laser excitation device 50, a laser ultrasonic shaping device 20, a detection device 30, and a battery displacement platform 40. The laser excitation device 50 outputs a pulsed laser. When the pulsed laser acts on the lithium battery sample, it excites the sample to generate an ultrasonic signal. Since the degree of electrolyte wetting varies at different locations, the intensity of the generated ultrasonic signal also varies, thus allowing the determination of the electrolyte wetting degree at that location based on the intensity of the ultrasonic signal. The detection device 30 receives the ultrasonic signal. By receiving and processing the ultrasonic signal, the oscillation waveform of the ultrasonic signal in the time domain can be obtained. After the wetting degree detection at one location of the lithium battery sample is completed, the lithium battery sample is moved by the battery displacement platform 40. The direction of movement of the lithium battery sample is perpendicular to the incident direction of the pulsed laser, allowing the pulsed laser to act on different locations of the lithium battery sample. This enables the detection device to obtain the electrolyte wetting degree at each location of the lithium battery sample, and ultimately, the overall electrolyte wetting degree of the lithium battery sample.

[0023] It should be noted that the intensity of the pulsed laser excited by the laser excitation device may fluctuate, resulting in different intensities of pulsed laser acting on different locations of the lithium battery sample. This phenomenon affects the accuracy of the wetting degree detection. Therefore, the laser ultrasonic shaping device 20 is needed to adjust the uniformity of laser energy intensity acting on each location of the lithium battery sample, thereby improving the accuracy of electrolyte wetting degree detection. Specifically, the uniformity of laser action on the lithium battery sample can be reflected by the first-wave flight time offset. The time of the first peak of the ultrasonic signal acquired by the detection device 30 can determine the first-wave flight time. Subtracting this first-wave flight time from the reference time yields the first-wave flight time offset. The detection device acquires the first-wave flight time of the corresponding ultrasonic signals from multiple excitations at the same detection location, and calculates a consistency index based on the first-wave flight time sequence. When the consistency index deviates from a preset range, the laser ultrasonic shaping device 20 is adjusted to improve laser excitation stability, thereby ensuring consistent laser excitation conditions at different detection locations and improving the accuracy of lithium battery electrolyte wetting degree detection.

[0024] Please note that the uniform adjustment device does not simply reshape the pulsed laser into a flat-top beam and then apply the flat-top beam to various positions of the lithium battery sample. Instead, it adjusts the pulsed laser with the same energy based on the flight time of the first wave, so that the pulsed lasers apply the same energy to different positions of the lithium battery sample sequentially.

[0025] The laser ultrasonic shaping device 20 can be any structure capable of adjusting the laser intensity. For example, the laser ultrasonic shaping device 20 can be a diffractive optical element, and the uniformity of the pulsed laser can be adjusted by adjusting the position of the diffractive optical element. For example, the laser ultrasonic shaping device 20 can also be a microlens array. Specifically, the microlens array includes multiple microlenses arranged in a preset form. By adjusting the distance between each microlens and the lithium battery sample, the convergence of the pulsed laser can be fine-tuned, thereby adjusting the uniformity of the pulsed laser intensity and further improving the detection accuracy of the lithium battery electrolyte wetting degree.

[0026] This invention provides a lithium battery electrolyte wetting detection system. The system includes a laser emitting device for outputting pulsed laser light, a battery displacement platform connected to the lithium battery sample and enabling the pulsed laser to act on different positions of the sample, and an ultrasonic signal generated at each position of the lithium battery sample under pulsed laser excitation. The ultrasonic signals generated at each position of the lithium battery sample under pulsed laser excitation, acquired by the detection device, can determine the electrolyte wetting state of the lithium battery sample. Simultaneously, the system also includes a laser ultrasonic shaping device, which uses the first-wave flight time offset as an evaluation criterion for laser intensity to provide feedback adjustment to the uniformity adjustment device, ensuring that the pulsed laser intensity acting on different positions of the lithium battery sample remains uniform, thereby improving the accuracy of detecting the degree of lithium battery electrolyte wetting.

[0027] In some embodiments, such as Figure 1 As shown, the lithium battery electrolyte wetting detection system also includes: a microscope objective 7, a dichroic mirror 5, and a focal length detection component 70. The microscope objective 7 is located between the laser ultrasonic shaping device 20 and the lithium battery sample, and is used to focus the pulsed laser onto the lithium battery sample. This focusing structure can concentrate the energy of the laser pulse on the location to be detected. While reducing the detection area to make the detection location more accurate, it also increases the overall energy intensity acting on each detection location. Under the condition that the difference in wetting degree is the same, the higher laser intensity can make the generated ultrasonic signal produce a greater difference, thereby further improving the accuracy of the lithium battery electrolyte wetting degree. Furthermore, in order to keep the measurement position of the lithium battery sample at the focal position of the microscope objective, the lithium battery sample needs to be moved along the laser direction by the battery displacement platform 40 to adjust the distance between the lithium battery sample and the microscope objective 7. That is, an autofocus structure is needed. The structure and principle of this autofocus are described below by way of example.

[0028] The dichroic mirror 5 is located between the laser ultrasonic shaping device 20 and the lithium battery sample, allowing the laser beam directed at the lithium battery sample to pass through. The light reflected from the lithium battery sample reaches the dichroic mirror 5 and is reflected by the dichroic mirror 5, thereby changing the propagation direction of the reflected light so that the reflected light can be directed to the focal length detection component 70. The focal length detection component 70 is used to convert the received reflected light into a detection signal. The battery displacement platform 40 is used to drive the lithium battery sample to move along the direction of the pulsed laser based on the intensity of the detection signal, so as to adjust the distance between the lithium battery sample and the microscope objective 7 until the lithium battery sample is located at the focal position of the microscope objective 7.

[0029] The focal length detection component 70 can be any sensor capable of detecting the focal distance between the lithium battery sample and the microscope objective 7. For example, the focal length detection component 70 can be a camera, and the image sharpness acquired by the camera can determine whether the lithium battery sample is located at the focal position of the microscope objective 7. For example, the focal length detection component 70 can also be a photomultiplier tube, which can convert light signals into electrical signals. The closer the lithium battery sample is to the focal point of the microscope objective 7, the higher the intensity of the reflected light acquired by the photomultiplier tube, and thus the higher the intensity of the electrical signal output by the photomultiplier tube. The distance between the lithium battery sample and the microscope objective 7 is adjusted based on the intensity of the electrical signal output by the photomultiplier tube. When the electrical signal intensity reaches a maximum value, the lithium battery sample is located at the focal position of the microscope objective 7.

[0030] In some embodiments, such as Figure 2 As shown, the lithium battery electrolyte wetting detection system also includes a confocal plate 80, which is located between the dichroic mirror 5 and the photomultiplier tube. The confocal plate 80 is provided with a probe hole 81. The light reflected by the dichroic mirror 5 passes through the probe hole 81 and is directed to the photomultiplier tube. Only the light at the focal point of the eyepiece 50 has a high intensity that passes through the probe hole and is directed to the photomultiplier tube. The light reflected by the lithium battery sample at the focal point causes the photomultiplier tube to generate an electrical signal intensity that is much greater than the light reflected by the lithium battery sample at a non-focal point. This makes it easier to achieve automatic focusing by using this electrical signal intensity. Moreover, the confocal method can also get rid of the influence of the surface shape of the tested object on focusing.

[0031] In some embodiments, such as Figure 3 As shown, the detection device 30 includes an ultrasonic probe 31, a data acquisition card 32, and a processing device 33. The ultrasonic probe 31 is used to acquire the ultrasonic signal output by the lithium battery sample. The digital acquisition card 12 discretizes the ultrasonic signal for subsequent processing by the processing device 33. The processing device 33 processes the discretized ultrasonic signal to obtain the electrolyte wetting degree of the lithium battery sample. For example, the larger the amplitude of the ultrasonic signal, the higher the wetting degree of the lithium battery sample. Optionally, the detection device 30 also includes a dual-wave mixing interferometer 34, used to filter the ultrasonic signal to filter the ultrasonic signal acquired by the ultrasonic probe 31, and to screen out the ultrasonic signal generated by the laser acting on the lithium battery sample to improve the signal-to-noise ratio.

[0032] In some embodiments, such as Figure 4 As shown, the lithium battery electrolyte wetting detection system includes: a laser ultrasonic optical path structure, a three-dimensional displacement platform, a dual-wavelength mixing interferometry system, an automatic focusing module, and a control module. The following provides a detailed description of each unit in the device: The laser ultrasound optical path structure includes a pulsed laser 1 (laser excitation device 90), a concave lens 2, a convex lens 3, a beam shaping module 4, a dichroic mirror 5, an aperture 6, and a microscope objective 7. The pulsed laser 1 generates pulsed laser light; the concave lens 2 and convex lens 3 form a beam expander system positioned along the propagation direction of the pulsed laser, with their surfaces perpendicular to the laser beam, used to increase the diameter of the generated pulsed laser and collimate it; the beam shaping system 4 shapes the Gaussian beam into a flat-top beam; the dichroic mirror 5, with its surface at a 45° angle to the pulsed laser beam, is used to transmit the pulsed laser light onto the surface of the microscope objective 7; the aperture 6 reduces the beam diameter; and the microscope objective 7 is used to focus the laser light onto the sample to generate an ultrasonic signal.

[0033] The dual-wave mixing interferometer system includes an ultrasonic probe 10, a dual-wave mixing interferometer 11, and a digital acquisition card 12. The detection beam emitted by the dual-wave mixing interferometer is focused and then vertically irradiates the back surface of the sample to obtain surface micro-vibration information generated by ultrasonic propagation in that area. The digital acquisition card 12 is used to convert the ultrasonic signal into a digital signal and input it into a computer 13 for processing.

[0034] The autofocus module consists of a dichroic mirror 5, a focusing lens 15, a CMOS camera 16, and a computer 13, forming a focusing system. The CMOS camera 16 reflects visible light through the dichroic mirror 5, and the image signal of the lithium battery sample is acquired through the microscope objective 7. The image is then transmitted to the computer 13 for image processing, and the computer controls the movement of the displacement platform 9 along the X and Y axes to achieve autofocus.

[0035] The control module includes a computer 13 and a digital signal generator 14; the digital signal generator 14 is a DG645, used to control the emission delay time of the pulsed laser, and the computer 13 is used to control the movement of the sample displacement platform 9 and the acquisition of laser ultrasonic signals, so as to read the ultrasonic signals and perform analysis.

[0036] Preferably, the pulsed laser 1 is a high-energy Nd:YAG nanosecond pulsed Q-switched laser; the concave lens 2 and convex lens 3 are aspherical concave-convex lenses with laser antireflection coatings, with wavelengths selected from 200 nm to 8000 nm and diameters selected from 25.4 mm. In other embodiments, the diameter, focal length, and other parameters of the second focusing lens can also be customized according to actual needs. The dichroic mirror 5 is a long-pass dichroic mirror, which has high reflectivity in the short-wavelength region and high transmittance in the long-wavelength region, and is also used to reflect stray light from the incident laser. The microscope objective is a long working distance objective with a magnification of 50x, a wavelength range of 480-1800 nm, and a working distance of 17 mm. In other embodiments, the objective focal length and magnification can be customized as needed.

[0037] This invention also provides a method for detecting electrolyte wetting in lithium batteries, which is based on the above. Figures 1 to 4The lithium battery electrolyte wetting detection system shown in any of the diagrams is implemented. The specific steps of the detection method are illustrated below with reference to various embodiments.

[0038] In some embodiments, such as Figure 5 As shown, the lithium battery electrolyte wetting detection method mainly includes the following steps: Step S101: Control the laser emitting device to output laser and record the laser excitation time node.

[0039] That is, control the laser emitter to output pulsed laser, and at the same time record the time node when the laser starts to be emitted. For ease of explanation, this node will be referred to as the first time node below.

[0040] Step S102: Continuously excite multiple laser ultrasonic signals at the same detection location and obtain the first-wave flight time of the ultrasonic signal corresponding to each excitation. Calculate the consistency index of the first-wave flight time based on the first-wave flight time sequence. Adjust the laser beam shaping parameters according to the consistency index of the first-wave flight time to improve the consistency of laser excitation conditions at the detection location.

[0041] This can be understood as follows: the ultrasonic signal acquired by the detection device can be understood as an oscillating signal in the time domain. The time point corresponding to the first peak of this vibration signal is recorded as the time node of the first ultrasonic peak. This time node is the first wave flight time. Subtracting the first wave flight time from the reference time yields the first wave flight time offset. Multiple laser ultrasonic signals are continuously excited at the same detection position, and the first wave flight time corresponding to each excitation is acquired. Based on the first wave flight time sequence, a consistency index of the first wave flight time is calculated, and the laser ultrasonic shaping device is adjusted according to the consistency index to improve the stability of laser excitation, thereby adjusting the uniformity of the laser intensity at the test position.

[0042] Optionally, the consistency of the first-wave flight time can be determined by the variance of each first-wave flight time.

[0043] Optionally, the consistency of the first-wave flight time can be determined by the difference from a reference time. The reference time can be determined by the average of the first-wave flight times of multiple pulsed lasers. Specifically, the laser emitting device excites multiple pulsed lasers, which act on the lithium battery sample. Each pulsed laser acting on the lithium battery sample yields a first-wave flight time. The average of the first-wave flight times corresponding to each pulsed laser can be used as a reference time. It can be understood that the intensity of the pulsed laser excited by the laser generating device may fluctuate within a certain range. By calculating the average of the first-wave flight times corresponding to multiple excited pulsed lasers, the average intensity of the pulsed laser excited by the laser generating device can be obtained. In subsequent tests, this average reference time is used as the adjustment benchmark for the first-wave flight time, which is equivalent to using the average intensity of the pulsed laser as the target value for laser intensity adjustment. This can reduce the risk that the laser intensity is difficult to adjust to the target value due to a large difference between the laser intensity and the adjustment target value, and can also speed up the adjustment speed of laser intensity.

[0044] Step S103: The detection device acquires ultrasonic signal data and extracts characteristic parameters used to characterize the electrolyte wetting state.

[0045] It should be noted that the feature parameters can be obtained in any way, such as by inputting ultrasonic data into a trained neural network model, and then using the neural network model to extract feature parameters from the ultrasonic signal data that can determine the electrolyte wetting state of the lithium battery.

[0046] Step S104: Control the battery displacement platform to apply the laser to different positions of the lithium battery sample. Repeat step S103 at each position until the ultrasonic signal data of each lithium battery sample position is obtained, and the electrolyte wetting state of the lithium battery sample is obtained based on the ultrasonic signal data.

[0047] In some embodiments, the lithium battery electrolyte wetting detection system further includes a photomultiplier tube and a microscope objective, such as... Figure 6 As shown, with Figure 5 The detection method shown is different in that, Figure 5 Between steps S102 and S103, the detection method further includes: Step S201: Obtain electrical signals from the photomultiplier tube.

[0048] This can be understood as follows: the photomultiplier tube is used to convert light signals into electrical signals, and the microscope objective is used to focus the laser. Placing the lithium battery sample at the focal point of the microscope objective can improve the detection accuracy. The closer the lithium battery sample is to the focal point, the higher the intensity of the light reflected from the lithium battery sample to the photomultiplier tube, thus making the intensity of the electrical signal acquired by the photomultiplier tube greater.

[0049] Step S202: Control the battery displacement platform to adjust the distance between the lithium battery sample and the microscope objective until the electrical signal reaches its maximum value.

[0050] That is, by controlling the battery displacement platform, the lithium battery sample is moved along the laser direction to change the distance between the lithium battery sample and the microscope objective, thereby searching for the focal position of the microscope objective within a certain range. During the movement within this range, the position where the electrical signal intensity acquired by the photomultiplier tube reaches its maximum value is the position where the lithium battery sample is located at the focal point of the microscope objective, thus achieving automatic focusing.

[0051] Optionally, during each execution of step S104, steps S201 and S202 are repeated before obtaining the characteristic parameters of the electrolyte wetting state of the lithium battery sample based on the ultrasonic signal data. That is, automatic focusing is performed after each change of measurement position.

[0052] In some embodiments, the lithium battery electrolyte wetting detection system further includes a photomultiplier tube and a microscope objective, such as... Figure 7 As shown, with Figure 5 The detection method shown is different in that, Figure 5 Between steps S102 and S103, the detection method further includes: Step S301: Obtain the electrical signal from the photomultiplier tube and the amplitude of the first ultrasonic peak from the detection device. Calculate the weighted sum of the peak value of the electrical signal and the amplitude of the first ultrasonic peak to obtain the focal length evaluation index.

[0053] This can be understood as follows: the distance between the lithium battery sample and the focal point of the microscope objective is related to the electrical signal output by the photomultiplier tube. The closer the lithium battery sample is to the focal point of the microscope objective, the greater the light intensity reflected from the lithium battery to the photomultiplier tube, and thus the higher the electrical signal intensity. The position of the lithium battery sample and the focal point of the microscope objective is also related to the ultrasonic data output by the lithium battery sample. The closer the lithium battery sample is to the focal point of the microscope objective, the higher the energy intensity of the laser acting on the lithium battery, and thus the higher the amplitude of the ultrasonic data. By combining the above two aspects of data to construct a focal length evaluation index, the focal point position of the microscope objective can be captured more accurately.

[0054] It should be noted that the purpose of placing the lithium battery sample at the focal point of the microscope objective is to increase the energy intensity of the laser acting on the lithium battery sample. Ultrasonic signal data can essentially determine whether the lithium battery sample is at the focal point. However, if the focal point is searched separately in this way, the lithium battery sample needs to remain for a relatively long time during the adjustment of the distance between the lithium battery sample and the microscope objective to obtain sufficient ultrasonic data, so as to reduce the influence of occasional random jitter in the ultrasonic data on the focal point search. This application only introduces the amplitude of the first wave of ultrasonic waves into the focal point search process and combines it with the electrical signal of the photomultiplier tube to construct a focal length evaluation index, which can improve the accuracy and efficiency of focal length search.

[0055] Step S302: Control the battery displacement platform to adjust the distance between the lithium battery sample and the microscope objective until the focal length evaluation index reaches its maximum value.

[0056] That is, more accurate automatic focusing is achieved through the integrated sound and light detection method.

[0057] Optionally, during each execution of step S104, steps S301 and S302 are repeated before obtaining the characteristic parameters of the electrolyte wetting state of the lithium battery sample based on ultrasonic signal data; that is, automatic focusing is performed after each change of measurement position. In some embodiments, the main process of the lithium battery electrolyte wetting detection method includes: The first step is to use the sample surface information obtained by the microscope objective to acquire sample images through a dichroic mirror, focusing lens, and CMOS camera before performing ultrasonic acquisition. The computer then processes the image information and controls the Z-axis movement of the displacement platform to achieve focusing of the lithium battery sample. The second step is to control the laser excitation device to emit pulsed laser. The pulsed laser passes through a concave lens, a convex lens, a beam shaping system, a dichroic mirror, an aperture, and a microscope objective in sequence before entering the surface of the lithium battery and generating a laser ultrasonic signal. The third step involves controlling the dual-wave mixer interferometer to collect the ultrasonic signals generated by the lithium battery from the opposite direction, and then converting the signals via a digital acquisition card before transmitting them to a computer for display and processing.

[0058] The fourth step involves using a computer-controlled displacement platform to change the position of the lithium battery sample being hit by the beam and repeating the first, second, and third steps to achieve surface scanning and obtain ultrasonic signals at different locations on the lithium battery sample. The fifth step is to image the surface of different lithium battery samples and analyze the ultrasonic signals during the wetting process of different electrolytes to determine the degree of wetting of the lithium batteries.

[0059] Optionally, in the second step mentioned above, the size of the beam spot is changed by using a Galilean beam expander system and focused by a microscope objective to form a smaller spot size, thereby improving the lateral resolution of the imaging; the Gaussian beam is shaped into a flat-top beam by using diffractive optical elements, so that the energy distribution of the pulse spot that excites the ultrasonic signal is more uniform, which can increase the signal-to-noise ratio, repeatability and quantitative performance.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for detecting the wetting of lithium battery electrolyte, characterized in that, The lithium battery electrolyte wetting detection method is implemented by a lithium battery electrolyte wetting detection system. The lithium battery electrolyte wetting detection system includes: Laser excitation device, used to output pulsed laser; Laser ultrasonic shaping device, used to adjust the uniformity of pulsed laser excitation energy; The detection device is used to acquire the ultrasonic signal generated by the lithium battery sample under the action of the pulsed laser, and the electrolyte wetting state of the lithium battery sample can be determined based on the ultrasonic signal. A battery displacement platform, which carries the lithium battery sample, is used to apply the pulsed laser to different positions of the lithium battery sample. The detection device is also used to acquire the first-wave flight time of the ultrasonic signal, and the laser ultrasonic shaping device is used to adjust the energy uniformity of the pulsed laser based on the difference between the first-wave flight time and the reference flight time of the ultrasonic signal, and to make the pulsed laser act on different positions of the lithium battery with the same central energy intensity; the reference flight time is determined by the average of the first-wave flight times of the ultrasonic signals generated by multiple pulsed lasers. The lithium battery electrolyte wetting detection method includes: Step S101: Control the laser emitting device to output laser light and record the laser excitation time point; Step S102: Continuously excite multiple laser ultrasonic signals at the same detection location and obtain the first-wave flight time of the ultrasonic signal corresponding to each excitation. Calculate the consistency index of the first-wave flight time based on the first-wave flight time sequence. Adjust the laser beam shaping parameters according to the consistency index of the first-wave flight time to improve the consistency of the laser excitation conditions at the detection location. The consistency of the first-wave flight time is determined by the difference from the reference time. Step S103: Acquire ultrasonic signal data by the detection device and extract characteristic parameters used to characterize the electrolyte wetting state; Step S104: Control the battery displacement platform to apply the laser to different positions of the lithium battery sample, repeat step S103 at each position until ultrasonic signal data at each position of the lithium battery sample is obtained, and obtain the electrolyte wetting state of the lithium battery sample based on the ultrasonic signal data.

2. The lithium battery electrolyte wetting detection method according to claim 1, characterized in that, The laser ultrasound shaping device includes a microlens array.

3. The lithium battery electrolyte wetting detection method according to claim 1 or 2, characterized in that, The lithium battery electrolyte wetting detection system also includes: A microscope objective, located between the laser ultrasonic shaping device and the lithium battery sample, is used to focus the pulsed laser onto the lithium battery sample; A dichroic mirror is located between the laser ultrasonic shaping device and the lithium battery sample. It is used to transmit pulsed laser light and receive and reflect light reflected from the surface of the lithium battery. A focal length detection component is used to receive the light reflected by the dichroic mirror and convert the light signal into a detection signal; wherein, the battery displacement platform adjusts the distance between the lithium battery sample and the microscope objective based on the detection signal output by the focal length detection component.

4. The lithium battery electrolyte wetting detection method according to claim 3, characterized in that, The focal length detection component includes a photomultiplier tube, which is used to convert the received optical signal into an electrical signal.

5. The lithium battery electrolyte wetting detection method according to claim 4, characterized in that, The lithium battery electrolyte wetting detection system also includes: A confocal plate is located between the dichroic mirror and the photomultiplier tube. The confocal plate has a probe hole, and the light reflected by the dichroic mirror passes through the probe hole and is directed to the photomultiplier tube.

6. The lithium battery electrolyte wetting detection method according to claim 1, characterized in that, The detection device includes: An ultrasonic probe is used to acquire the ultrasonic signals output by a lithium battery sample. A digital acquisition card is used to convert ultrasound signals into digital signals; A computer for processing the digital signals.

7. The lithium battery electrolyte wetting detection method according to claim 4, characterized in that, Between step S102 and step S103, the lithium battery electrolyte wetting detection method further includes: The electrical signal is acquired by the photomultiplier tube; The battery displacement platform is controlled to adjust the distance between the lithium battery sample and the microscope objective until the electrical signal reaches its maximum value.

8. The lithium battery electrolyte wetting detection method according to claim 4, characterized in that, Between step S102 and step S103, the lithium battery electrolyte wetting detection method further includes: An electrical signal is acquired by the photomultiplier tube, and the amplitude of the first ultrasonic peak is acquired by the detection device. The focal length evaluation index is obtained by calculating the weighted sum of the peak value of the electrical signal and the amplitude of the first ultrasonic peak. The battery displacement platform is controlled to adjust the distance between the lithium battery sample and the microscope objective until the focal length evaluation index reaches its maximum value.

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