A non-destructive testing system and method for lithium battery electrode materials

Abstract

The application relates to the technical field of material component detection, and particularly discloses a nondestructive testing system and method for lithium battery electrode materials, which comprises a laser, a polarization light splitting component for splitting a laser beam emitted by the laser into light ray one and light ray two, a beam splitter for receiving the light ray two and transmitting and reflecting the light ray two, a lens component one for changing the direction of the light ray one, a lens component two for changing the direction of the transmitted light ray two transmitted by the beam splitter, a lens component three for changing the direction of the reflected light ray two reflected by the beam splitter, a sample table for mounting a target material, and a spectrum component for collecting a fluorescent signal of the target material; the application can effectively realize the spectrum detection of high-intensity signals and high-detection consistency under extremely low sample damage conditions.

Description

Technical Field

[0001] This invention relates to the field of material composition testing technology, and more specifically, to a non-destructive testing system and method for lithium battery electrode materials. Background Technology

[0002] Existing laser spectroscopy techniques (such as LIBS) typically use a single high-energy laser pulse to be directly focused onto the sample surface to generate plasma, and then analyze the plasma emission spectrum to detect components. However, this method has significant limitations: 1. Significant damage: High single-pulse energy is required to generate a sufficiently strong signal, which can easily cause irreversible ablation damage to the sample (especially delicate battery electrode materials), affecting subsequent processes or performance.

[0003] 2. Poor consistency: Due to the local non-uniformity of the material, the results of single-point excitation are not representative enough. Multiple measurements are required to take an average, which is inefficient and greatly affected by single-point damage.

[0004] 3. The contradiction between signal-to-noise ratio and efficiency: reducing energy to reduce damage will result in weak signal and low excitation efficiency; increasing energy will aggravate damage and may cause ablation and contamination of optical components. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a non-destructive testing system and method for lithium battery electrode materials, so as to achieve spectral detection with high intensity signal and high detection consistency under extremely low sample damage conditions; The solution adopted by this invention to solve the technical problem is: on the one hand: This invention provides a non-destructive testing system for lithium battery electrode materials, including a laser, a polarization beam splitter that splits a laser beam emitted by the laser into beam one and beam two, a beam splitter that receives beam two and transmits and reflects it, a lens assembly one for changing the direction of beam one, a lens assembly two for changing the direction of transmitted beam two transmitted by the beam splitter, a lens assembly three for changing the direction of reflected beam two reflected by the beam splitter, a sample stage for mounting a target material, and a spectral assembly for collecting fluorescence signals from the target material. The axis of ray 1 after passing through lens assembly 1 lies on the angle bisector of the angle formed by the axis of transmitted ray 2 after passing through lens assembly 2 and the axis of reflected ray 2 after passing through lens assembly 3. The transmitted light ray 2 after passing through lens assembly 2 and the reflected light ray 2 after passing through lens assembly 3 form a plasma grating on the target surface; the light ray 1 after passing through lens assembly 1 is focused on the plasma grating, and the target is excited by the interaction between photons and plasma, and the spectral assembly collects the fluorescence signal of the target.

[0006] In some possible implementations, the delay between the light beam and the plasma grating is 0-200 ps.

[0007] In some possible implementations, the polarization beam splitter includes a half-wave plate and a polarization beam splitter cube; After the laser beam is polarized by a half-wave plate, it is incident on a polarization beam splitter cube. The polarization beam splitter cube splits the laser beam into two beams: beam one is the transmitted beam, and beam two is the reflected beam. The intensity output ratio of beam one to beam two is 1:2.

[0008] In some possible implementations, the intensity output ratio of the second transmitted ray to the second reflected ray is 1:1. In some possible implementations, the lens assembly 2 includes multiple sets of reflecting mirrors 2A and curved mirrors 2A arranged sequentially along an optical path; the transmitted light 2 is reflected by reflecting mirrors 2A and focused into filaments on the target surface by the curved mirrors; The lens assembly three includes multiple sets of reflective mirrors threeA and curved mirrors threeA arranged sequentially according to the optical path; the reflected light two is reflected by the multiple sets of reflective mirrors threeA in sequence, and then focused by the curved mirrors into filaments on the target surface to form a plasma grating in conjunction with the transmitted light two.

[0009] In some possible implementations, the lens assembly includes multiple sets of reflectors A and short-focal-length lenses A arranged sequentially along an optical path; after being reflected by the multiple sets of reflectors A, light is focused onto the plasma grating by the short-focal-length lenses A.

[0010] In some possible implementations, reflector A, reflector B, and reflector C are all small-angle reflectors.

[0011] In some possible implementations, the spectral assembly includes a lens, a spectrometer, and fiber optic cables for connecting the lens and the spectrometer; the lens is positioned above the target.

[0012] In some possible implementations, a gas injector is provided at the end of the lens near the target; a short focal length lens group is provided inside the lens.

[0013] on the other hand: The present invention also provides a testing method for a non-destructive testing system for lithium battery electrode materials according to the above description, specifically including the following steps: The target material is placed on the sample stage, and inert gas is sprayed onto the lens of the spectral component through a gas injector. The inert gas forms a barrier on the lens. The laser emits a laser beam, which is then split into beam one and beam two by a polarization beam splitter. Light beam 2 is split into two beams of equal intensity by a beam splitter: transmitted light beam 2 and reflected light beam 2. Transmitted light beam 2 and reflected light beam 2 are then used by lens assembly 2 and lens assembly 3 to form a plasma grating on the surface of the target material, respectively. After the plasma grating is formed, the light beam is focused onto the plasma grating after passing through the polarization beam splitter; the sample is excited by laser, and the fluorescence signal of the target material is collected by two short-focal-length lenses and transmitted to the spectrometer. Compared with the prior art, the beneficial effects of the present invention are as follows: This invention proposes and realizes the use of a plasma grating formed on the target surface by the coupling interference of reflected beam 2 and transmitted beam 2 as a low-energy, high-efficiency excitation source. Combined with the precise time delay of beam 1 for synergistic excitation, the excitation efficiency is greatly improved. Under the premise of extremely low sample damage, the spectral signal intensity surpasses that of traditional single-beam high-energy laser excitation, achieving a breakthrough of "stronger excitation and lower damage". This invention can reduce detection damage to an extremely low level, enabling the component detection of sensitive functional materials such as lithium battery electrode sheets to be performed directly during the production process (such as after coating or rolling). The electrode material after testing does not affect subsequent processes such as slicing, stacking, and packaging, as well as its final electrochemical performance. It provides an unprecedented in-situ, online, and non-destructive analysis tool for lithium battery process optimization and quality control, and is expected to promote the refined development of battery manufacturing technology. This invention integrates a gas jetting device, which effectively solves the problem of trace contaminant accumulation that may still exist in low-damage testing, and ensures the long-term maintenance-free operation of the optical system in industrial environments and the stability of the test results. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the optical path in this invention; Figure 3 The spectrum of lithium iron phosphate electrode material detected using the present invention; in: 1. Half-dip; 2. Polarizing beam splitter cube; 3. Beam splitter; 4. Mirror 2A; 5. Curved mirror 2A; 6. Mirror 3A; 7. Curved mirror 3A; 8. Mirror 1A; 9. Short focal length lens 1A; 10. Sample stage; 11. Laser; 12. Spectrometer; 121. Lens; 122. Fiber optic cable. Detailed Implementation

[0015] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. The terms "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, "a" or "one," etc., do not indicate a quantity limitation, but rather indicate the existence of at least one. In the implementation of this application, "and / or" describes the association relationship of related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more. For example, multiple positioning posts refer to two or more positioning posts. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0016] The present invention will now be described in detail.

[0017] on the one hand: This invention provides a non-destructive testing system for lithium battery electrode materials, including a laser 11, a polarization beam splitter that splits a laser beam emitted by the laser 11 into beam one and beam two, a beam splitter 3 that receives beam two and transmits and reflects it, a lens assembly one for changing the direction of beam one, a lens assembly two for changing the direction of transmitted beam two transmitted by the beam splitter 3, a lens assembly three for changing the direction of reflected beam two reflected by the beam splitter 3, a sample stage 10 for mounting a target material, and a spectral assembly for collecting fluorescence signals from the target material. The transmitted light ray 2 after passing through lens assembly 2 and the reflected light ray 2 after passing through lens assembly 3 form a plasma grating on the target surface; the light ray 1 after passing through lens assembly 1 is focused on the plasma grating, and the target is excited by the interaction between photons and plasma, and the spectral assembly collects the fluorescence signal of the target. The axis of ray 1 after passing through lens assembly 1 lies on the angle bisector of the angle formed by the axis of transmitted ray 2 after passing through lens assembly 2 and the axis of reflected ray 2 after passing through lens assembly 3.

[0018] Specifically, the second transmitted light beam is spatially modulated through the second lens assembly, and the second reflected light beam is spatially modulated through the third lens assembly, thereby forming a plasma grating on the target surface. Due to the energy localization enhancement effect of the interference field (the second transmitted light beam and the second reflected light beam), the plasma grating structure can form an electric field energy density in its periodic region that is much higher than that of a single beam of light. This allows for efficient ionization and excitation of the material while significantly reducing the total input energy of a single pulse, fundamentally reducing the ablation damage to the sample during the initial excitation process. The plasma grating formed by the combination of the second transmitted light beam and the second lens assembly, and the second reflected light beam and the third lens assembly, has a large interference area (large-format interference pattern), covering a surface area on the sample rather than a single point. The spectral component simultaneously collects spectral signals from multiple regions on the target material's microstructure, naturally averaging the fluctuations caused by uneven electrode material coating and microscopic compositional variations. Highly representative and consistent compositional information can be obtained with a single excitation, avoiding the tedious and cumulative damage of traditional methods that require multiple single-point ablation.

[0019] In some possible implementations, the delay between the light beam and the plasma grating is 0-200 ps.

[0020] In some possible implementations, the polarization beam splitter includes a half-wave plate 1 and a polarization beam splitter cube 2; After the laser beam is polarized by half-wave plate 1, it is incident on polarization beam splitter cube 2. Polarization beam splitter cube 2 splits the laser beam into beam one and beam two. Beam one is a transmitted beam and beam two is a reflected beam. The intensity output ratio of beam one to beam two is 1:2.

[0021] In some possible implementations, the light intensity output ratio of the second transmitted ray to the second reflected ray is 1:1.

[0022] In some possible implementations, the lens assembly two includes multiple sets of reflective mirrors two A4 and a set of curved mirrors two A5 arranged sequentially along the optical path; the transmitted light beam two is reflected by the reflective mirrors two A4 and focused into a filament on the target surface by the curved mirrors two A5; preferably, there are two sets of reflective mirrors two A4; The lens assembly three includes multiple sets of reflective mirrors three A6 and a set of curved mirrors three A7 arranged sequentially according to the optical path; the reflected light two is reflected sequentially by the multiple sets of reflective mirrors three A6, and then focused by the curved mirrors three A7 into filaments on the target surface, which, together with the transmitted light two focused into filaments on the target surface, forms a plasma grating; preferably, there are three sets of reflective mirrors three A6.

[0023] In some possible implementations, the lens assembly includes multiple sets of reflectors A8 and a set of short-focal-length lenses A9 arranged sequentially along an optical path; after being reflected by the multiple sets of reflectors A8, the light is focused onto the plasma grating by the short-focal-length lenses A9; preferably, there are two sets of reflectors A8.

[0024] In some possible implementations, the reflector A8, reflector A4, and reflector A6 are all small-angle reflectors, wherein the angle between the incident direction of light and the normal of the small-angle reflector is less than 30°.

[0025] In this invention, for the second transmitted ray and the second reflected ray forming the plasma grating, multiple sets of small-angle reflectors are used to guide them to the corresponding curved mirrors, which then focus the target material. A focusing spot that is conducive to achieving a large field of view and good aberration correction is used, which facilitates the formation of a high-quality large-format interference pattern. The first ray uses a lens assembly as an independent tight-focusing optical element to ensure that the first ray can be accurately incident on the plasma grating area.

[0026] In some possible implementations, the spectral assembly includes a lens 121, a spectrometer 12, and an optical fiber cable 122 for connecting the lens 121 and the spectrometer 12; the lens 121 is located above the target.

[0027] In some possible implementations, a gas injector is provided at the end of the lens 121 near the target material; a short focal length lens group is provided inside the lens 121.

[0028] A gas ejector is integrated and installed at the front end of lens 121; before, during, and after laser action, inert gas is continuously or pulsedly ejected to form a barrier at the front end of the lens. The ejected inert gas will form a barrier at the front end of the lens 121, which can effectively blow away and drive away the feathers and sputtering particles generated by laser ablation, prevent them from contaminating the surface of the focusing lens 121, ensure the long-term stable operation and detection reliability of the optical system, and is an important aid to achieving efficient and low-damage continuous detection. The gas injector can be a supersonic air knife, and the inert gas can be argon or nitrogen.

[0029] on the other hand: The present invention also provides a testing method for a non-destructive testing system for lithium battery electrode materials according to the above description, specifically including the following steps: The target material is placed on the sample stage 10, and inert gas is sprayed through the gas ejector. The inert gas forms a barrier at the front end of the lens 121. Here, the front end of the lens 121 is the end of the lens 121 that is close to the target material. Before the laser interacts with the material, the gas ejector at the front end of the lens 121 is turned on, which can effectively prevent particles generated by ablation from contaminating the lens 121.

[0030] Laser 11 emits a laser beam, which is split into beam one and beam two by a polarization beam splitter; preferably, laser 11 can be a femtosecond laser. The second beam is split into two beams of equal intensity by a beam splitter: a transmitted beam and a reflected beam. The transmitted beam and the reflected beam are then separated into lens assembly 2 and lens assembly 3, respectively, to form a plasma grating on the surface of the target material. The formed plasma grating first ablates the target material to generate plasma, which contains a high density of free electrons. After the plasma grating is formed, the light beam is focused onto the plasma grating after passing through the polarization beam splitter; the laser excites the sample, and the fluorescence signal of the target material is collected by two short focal length lenses and transmitted to the spectrometer 12; Specifically, the light beam bombards the plasma grating, forming a synergistic excitation of laser and electrons. The laser beam repeatedly collides within the plasma grating channel, inducing avalanche ionization within hundreds of nanoseconds after the bombardment, which greatly improves the excitation efficiency and provides a unique fingerprint spectrum for the electrode material.

[0031] Example 1: In this embodiment, laser 11 is a femtosecond laser that can emit 800nm ​​femtosecond laser light, with a single pulse energy of 3mJ, a pulse width of 50fs, and a repetition frequency of 1kHz; the target material is lithium iron phosphate electrode material. Place the lithium iron phosphate electrode material on the sample stage 10, turn on the gas injector, and the test can be performed; During testing, after the femtosecond laser emits a laser beam, it first passes through half-wave plate 1, which can adjust the polarization state of the laser. The laser beam passes through a polarization beam splitter 2, which changes the ratio of transmitted to reflected light according to the polarization state of the laser. By combining a half-wave plate 1 and a polarization beam splitter 2, rotating the half-wave plate 1 can achieve a light intensity output ratio of 2:1 between the reflected light ray 2 and the transmitted light ray 2.

[0032] The second beam is then split into two laser beams of equal intensity by a beam splitter 3 with a beam intensity output ratio of 1:1. One beam is reflected, becoming the second reflected beam, and the other is transmitted, becoming the second transmitted beam. The two beams (the second transmitted beam and the second reflected beam) pass through several small-angle mirrors and are then focused into filaments by corresponding curved mirrors. The small-angle mirrors can guide the corresponding beams to a precise direction while preserving the original characteristics of the beams to the greatest extent. The advantage of using curved mirrors for focusing is that there is absolutely no chromatic aberration.

[0033] By precisely controlling the synchronization of two beams of light (transmitted beam two and reflected beam two), a plasma grating is formed in the interference region of the two beams; After the light beam passes through the polarization beam splitter 2, its direction is changed by two small-angle reflectors, and then it is focused onto the plasma grating by a short-focal-length lens A9, with the delay between the light beam and the plasma grating controlled to be 50 ps. The target material is placed on the sample stage 10, the sample is excited by laser, and the fluorescence signal of the target material is collected by two short-focal-length lenses and transmitted to the spectrometer 12.

[0034] Before the laser interacts with matter, opening the gas ejector below the lens can effectively prevent particles generated by ablation from contaminating the lens 121.

[0035] Fluorescence signals were collected using spectrometer 12, such as Figure 3 The image shows the spectrum of detection using lithium iron phosphate electrode material as the target material; the characteristic peaks of iron and lithium are clearly visible in the image; since the lithium iron phosphate electrode material is attached to the aluminum foil, the characteristic peak of aluminum is also detected. This invention enables high-precision non-destructive testing. Specifically, the second transmitted light beam and the second reflected light beam form a plasma grating on the target surface. Both the laser intensity and electron density exhibit periodic modulation, which concentrates the laser energy within the periodic structure. This helps to overcome the peak power clamping effect of the femtosecond filament and achieve better ablation. After the plasma grating is formed 0-200 ps, ​​light ray 1 passes through lens assembly 1 and propagates along the angle bisector of the transmitted and reflected light rays 2. When light ray 1 passes through the plasma grating, Bragg diffraction occurs, causing its energy to no longer be uniformly distributed but periodically distributed, thus allowing the pulse to self-focus directly along the formed plasma grating. In other words, light ray 1 undergoes filamentation by following the same plasma modulation structure as the formed plasma grating. Therefore, even light ray 1 itself can break through the peak power clamping formed by a single filament in air. During the lifetime of the formed plasma grating, the continuous plasma modulation acts as the modulation seed for light ray 1. The zero-order Bragg diffraction of light ray 1 with a 0-200 ps delay forces the formed plasma grating to regenerate, where the plasma density and plasma modulation contrast are enhanced, thereby prolonging the plasma grating excitation and contributing to the formation of a high signal-to-noise ratio breakdown spectral line.

[0036] Because plasma is sensitive to the local distribution of electrode materials, a large-format interference pattern is used to avoid high single-point damage, achieving high consistency and high efficiency with low damage in electrode material composition detection. The plasma grating channel generated by the nonlinear interference of three high-intensity femtosecond laser filaments exhibits a periodic structural distribution. By confining the pulse energy to the periodic structure, a very high optical field intensity can be achieved with only a very low pulse energy. In addition, the periodic structure ensures that the interaction between the laser and the electrode material occurs on a large surface with many points. The integration of these many points generates the final spectral signal, avoiding the problem of high single-point damage in traditional techniques.

[0037] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A non-destructive testing system for lithium battery electrode materials, characterized in that, The system includes a laser, a polarization beam splitter that splits a laser beam emitted by the laser into beam one and beam two, a beam splitter that receives beam two and transmits and reflects it, a lens assembly one for changing the direction of beam one, a lens assembly two for changing the direction of the transmitted beam two transmitted by the beam splitter, a lens assembly three for changing the direction of the reflected beam two reflected by the beam splitter, a sample stage for mounting a target, and a spectral assembly for collecting the fluorescence signal of the target. The axis of ray 1 after passing through lens assembly 1 lies on the angle bisector of the angle formed by the axis of transmitted ray 2 after passing through lens assembly 2 and the axis of reflected ray 2 after passing through lens assembly 3. The transmitted light beam 2 after passing through lens assembly 2 and the reflected light beam 2 after passing through lens assembly 3 form a plasma grating on the target surface; the light beam 1 after passing through lens assembly 1 is focused on the plasma grating, and the target is excited by the interaction between photons and plasma, and the spectral assembly collects the fluorescence signal of the target.

2. The non-destructive testing system for lithium battery electrode materials according to claim 1, characterized in that, The delay between the light beam and the plasma grating is 0-200 ps.

3. The non-destructive testing system for lithium battery electrode materials according to claim 1, characterized in that, The polarization beam splitter includes a half-wave plate and a polarization beam splitter cube; After the laser beam is polarized by a half-wave plate, it is incident on a polarization beam splitter cube. The polarization beam splitter cube splits the laser beam into two beams: beam one is transmitted and beam two is reflected. The intensity output ratio of beam one to beam two is 1:

2.

4. The non-destructive testing system for lithium battery electrode materials according to claim 1, characterized in that, The intensity output ratio of the second transmitted ray to the second reflected ray is 1:

1.

5. A non-destructive testing system for lithium battery electrode materials according to claim 1, characterized in that, The lens assembly 2 includes multiple sets of reflecting mirrors 2A and curved mirrors 2A arranged sequentially according to the optical path; the transmitted light 2 is reflected by the reflecting mirrors 2A and focused into filaments on the surface of the target material by the curved mirrors; The lens assembly three includes multiple sets of reflective mirrors threeA and curved mirrors threeA arranged sequentially according to the optical path; the reflected light two is reflected by the multiple sets of reflective mirrors threeA in sequence, and then focused by the curved mirrors into filaments on the target surface to form a plasma grating in conjunction with the transmitted light two.

6. A non-destructive testing system for lithium battery electrode materials according to claim 5, characterized in that, The lens assembly includes multiple sets of reflectors A and short-focal-length lenses A arranged sequentially along the optical path; after the light rays are reflected by the multiple sets of reflectors A, they are focused onto the plasma grating by the short-focal-length lenses A.

7. A non-destructive testing system for lithium battery electrode materials according to claim 6, characterized in that, The reflectors A1, A2, and A3 are all small-angle reflectors.

8. A non-destructive testing system for lithium battery electrode materials according to claim 1, characterized in that, The spectral assembly includes a lens, a spectrometer, and an optical fiber cable for connecting the lens and the spectrometer; the lens is located above the target material.

9. A non-destructive testing system for lithium battery electrode materials according to claim 8, characterized in that, A gas injector is provided at the end of the lens near the target material; a short focal length lens group is provided inside the lens.

10. A testing method for a non-destructive testing system for lithium battery electrode materials according to any one of claims 1-9, characterized in that, Specifically, the following steps are included: The target material is placed on the sample stage, and inert gas is sprayed onto the surface of the target material through a gas injector, forming a barrier. The laser emits a laser beam, which is then split into beam one and beam two by a polarization beam splitter. Light beam 2 is split into two beams of equal intensity by a beam splitter: transmitted light beam 2 and reflected light beam 2. Transmitted light beam 2 and reflected light beam 2 are then used by lens assembly 2 and lens assembly 3 to form a plasma grating on the surface of the target material, respectively. After the plasma grating is formed, the light beam is focused onto the plasma grating after passing through the polarization beam splitter; the laser excites the sample, and the fluorescence signal of the target material is collected by two short focal length lenses and transmitted to the spectrometer.

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