Single-particle mechanical property testing system

Abstract

The utility model discloses a single particle mechanical property test system, which can realize the whole process of observing and detecting micro particles from being extruded to a crushing state, and comprises a test frame, an objective table, a glass slide, a pressure head, an objective lens, a lower light source, an eyepiece, an imaging device and a refraction single lens, the objective table is mounted on the test frame in an X-Y axis adjustable manner, and is provided with a through hole; the glass slide stretches across the through hole and is used for placing a particle sample to be tested; the pressure head is matched above the objective table in a lifting manner along the Z-axis direction; the objective lens is arranged below the through hole; the lower light source is arranged on the side below the objective lens; the eyepiece is arranged on the surface of the test frame; the imaging device is arranged in the test frame; the refraction single lens is arranged below the objective lens, and the reflection surface of the refraction single lens simultaneously faces the objective lens and the imaging device; the refraction single lens refracts light emitted by the lower light source to the direction of the objective lens, the light in the direction of the objective lens is reflected to the imaging device through the reflection face, and the imaging device presents collected images on the eyepiece.

Description

Technical Field

[0001] The utility model relates to the technical field of material testing equipment, in particular to a single-particle mechanical property testing system. Background Technique

[0002] On the microscale, the electrodes of lithium-ion batteries are composed of nanoparticles or microparticles; at the same time, the inherent particle characteristics of the electrode materials play a decisive role in the electrochemical performance of the batteries. In terms of mechanical properties, testing the compressive strength of individual particles of battery materials can be used to evaluate the pressure resistance of the materials and guide the rolling process. Materials with higher mechanical strength will also have better subsequent cycle stability.

[0003] On the one hand, a high compressive strength of the particles indicates that the particles can withstand higher-intensity external forces and are less likely to be crushed. Corresponding to the pressing process, it can make the material or the electrode sheet have a higher compaction density, load more positive or negative electrode materials in a unit space, and contribute to improving the battery capacity density.

[0004] On the other hand, there is also a certain correlation between the overall compressive strength of the particles and the performance of the finally manufactured battery cells. During the cycling process of the battery cells, as lithium ions are inserted and extracted, internal stresses in the particles gradually accumulate, and finally cracks or fractures occur. The lower the mechanical strength of the particles, the shorter the expected service life of the battery cells. Therefore, materials with relatively higher compressive strength will improve the comprehensive electrochemical performance of the batteries.

[0005] In summary, testing the mechanical properties of single particles of lithium battery materials can not only provide key material property parameters but also help to deeply understand the relationship between material properties and battery performance, thereby guiding the battery design and manufacturing process and improving the performance and life of the batteries.

[0006] Currently, the characterization methods for the microscale mechanical properties of materials, such as the force curve test of atomic force microscopy and the hardness test of nanoindenters (see patents CN201220605459.0, CN202311050486.5), etc., mainly test the mechanical properties of thin films or coatings and substrates, and are not applicable to battery material particles at the micron level, and cannot test the mechanical properties of microscale particles (2 - 20 μm) and reflect the particle compressive resistance. Some other characterization methods, such as using scanning electron microscopy (SEM), can only observe the phase of the material after certain experimental conditions, but cannot observe the phase change process during the experiment, compare the crack and fracture states on the particle surface, and determine the compressive resistance of the particles based on the phase situation, which also has limitations and lags. If the microscale particles of the material are not damaged during the compression process, or the microscale particle changes of different materials are similar during the compression process, it is impossible to effectively and quantitatively describe the compressive resistance of the particles. Content of the Utility Model

[0007] The purpose of the present utility model is to provide a single-particle mechanical property testing system, which solves the problems existing in the prior art and can observe and detect the whole process of a microscopic particle being extruded until it is crushed.

[0008] To achieve the above object, the solution of the present utility model is:

[0009] A single-particle mechanical property testing system includes a test stand, a stage, a glass slide, a press head, an objective lens, a lower light source, an eyepiece, an imaging device, and a refractive single lens; the stage is adjustably installed on the test stand and is provided with a through hole; the stage adjusts its position in the XY axes relative to the test stand; the glass slide spans over the through hole and is used to place the particle sample to be tested; the press head is arranged above the stage and is lifted and lowered along the Z axis; the objective lens is arranged below the through hole; the lower light source is arranged on the side below the objective lens; the eyepiece is arranged on the surface of the test stand; the imaging device is arranged inside the test stand; the refractive single lens is arranged below the objective lens, and its reflecting surface faces both the objective lens and the imaging device at the same time; the refractive single lens refracts the light emitted by the lower light source towards the direction of the objective lens and reflects the light in the direction of the objective lens to the imaging device through the reflecting surface, and the imaging device presents the collected image on the eyepiece.

[0010] The imaging device is a CCD camera, and the eyepiece is an electronic eyepiece.

[0011] The imaging device is a mirror, and the eyepiece is a convex lens.

[0012] The single-particle mechanical property testing system further includes an upper light source arranged above the press head.

[0013] An adjustable turntable is rotatably fitted inside the test stand, and a plurality of mounting grooves are arranged on the turntable, and each mounting groove is provided with an objective lens, and the magnification ratios of the objective lenses are different.

[0014] An X-axis adjustment plate is slidably installed on the test stand along the X axis, and a Y-axis adjustment plate is slidably installed on the X-axis adjustment plate along the Y axis. The X-axis adjustment plate and the Y-axis adjustment plate share a regulating rod, and the regulating rod is used to control the movement of the X-axis adjustment plate in the X axis and the movement of the Y-axis adjustment plate in the Y axis; the stage is installed on the Y-axis adjustment plate.

[0015] A Z-axis driving device is installed on the test stand through a bracket, and a lifting seat is installed at the output end of the Z-axis driving device; the press head is installed inside the lifting seat.

[0016] Preferably, a force displacement sensor is installed inside the lifting seat, and the press head is installed at the detection end of the force displacement sensor.

[0017] The single-particle mechanical property testing system further includes a housing covering the outside of the testing frame, and the housing has a flip cover that can be opened and closed movably.

[0018] After adopting the above technical solution, the present utility model has the following technical effects:

[0019] Compared with the prior art, the present utility model is designed with a unique inverted optical path system. The lower light source is located below the stage and the glass slide. The light emitted by the lower light source is refracted by the refractive single lens to the position of the glass slide to illuminate the particle sample. After the light is reflected by the particle sample, it will be focused by the objective lens and concentrated on the reflecting surface of the refractive single lens to form an enlarged real image. Then, this real image is collected by the imaging device, magnified again and imaged on the eyepiece for the operator to observe. Therefore, during the entire process of the indenter pressing down completely, the operator can continuously observe the entire process of the particle sample being squeezed and deformed by the indenter until it is crushed, realizing a clear observation of the microscopic change state of the particle sample, rather than only being able to observe the crushed state of the particle sample after it is crushed; at the same time, combined with the data collection during the instrument experiment process, the present utility model can more accurately judge the cracking and crushing states of the particles. Description of the Drawings

[0020] Figure 1 is a schematic external view of a specific embodiment of the present utility model;

[0021] Figure 2 is a three-dimensional view of a partial structure of a specific embodiment of the present utility model (hiding the housing);

[0022] Figure 3 is a partial structure cross-sectional view of a specific embodiment of the present utility model (hiding the housing);

[0023] Figure 4 is a schematic working principle diagram of a specific embodiment of the present utility model;

[0024] Explanation of the Reference Numerals in the Drawings:

[0025] 1 - testing frame; 2 - stage; 21 - through hole; 3 - glass slide; 4 - indenter; 5 - objective lens; 6 - lower light source; 7 - eyepiece; 8 - imaging device; 9 - refractive single lens; 91 - reflecting surface; 10 - upper light source; 20 - turntable; 201 - mounting groove; 30 - X-axis adjustment plate; 40 - Y-axis adjustment plate; 50 - adjustment rod; 60 - Z-axis driving device; 70 - lifting seat; 80 - force-displacement sensor; 90 - housing; 901 - flip cover; 902 - handle;

[0026] a - particle sample. Detailed Embodiments

[0027] To further explain the technical solution of the present invention, the present invention will be elaborated in detail through specific embodiments below.

[0028] Referring to Figures 1 to 4 As shown, the present invention discloses a single-particle mechanical property testing system, including a test stand 1, a stage 2, a glass slide 3, a indenter 4, an objective lens 5, a lower light source 6, an eyepiece 7, an imaging device 8 and a refractive single lens 9;

[0029] The stage 2 is adjustably mounted on the test stand 1 and is provided with a through hole 21; the stage 2 adjusts its position in the XY axes relative to the test stand 1;

[0030] The glass slide 3 spans over the through hole 21 and is used to place the particle sample a to be tested;

[0031] The indenter 4 is arranged above the stage 2 to move up and down along the Z axis;

[0032] The objective lens 5 is arranged below the through hole 21;

[0033] The lower light source 6 is arranged on the side below the objective lens 5;

[0034] The eyepiece 7 is arranged on the surface of the test stand 1 for observation;

[0035] The imaging device 8 is arranged inside the test stand 1;

[0036] The refractive single lens 9 is arranged below the objective lens 5, and its reflecting surface 91 faces both the objective lens 5 and the imaging device 8; the refractive single lens 9 refracts the light emitted by the lower light source 6 towards the direction of the objective lens 5, and reflects the light in the direction of the objective lens 5 to the imaging device 8 through the reflecting surface 91, and the imaging device 8 presents the collected image to the eyepiece 7.

[0037] Through the above solution, compared with the prior art, the present invention is designed with a unique inverted optical path system. The lower light source 6 is located below the stage 2 and the glass slide 3. Referring to Figure 4 , the light emitted by the lower light source 6 is refracted by the refractive single lens 9 to the position of the glass slide 3 to illuminate the particle sample a. After the light is reflected by the particle sample a, it will be focused by the objective lens 5 and concentrated on the reflecting surface 91 of the refractive single lens 9 to form an enlarged real image. Then, this real image is collected by the imaging device 8, magnified again and imaged on the eyepiece 7, and observed by the operator. Therefore, during the entire downward pressing process of the indenter 4, the operator can continuously observe the entire process of the particle sample a being squeezed and deformed by the indenter 4 until it is crushed, realizing a clear observation of the microscopic change state of the particle sample a, rather than only being able to observe the crushed state of the particle sample a after it is crushed; at the same time, combined with the data collection during the instrument experiment process, the present invention can more accurately judge the cracking and breaking states of the particles.

[0038] The following shows specific embodiments of the present utility model.

[0039] In this embodiment, the above imaging device 8 is a CCD camera, and image acquisition is achieved by photographing the reflecting surface 91. At this time, the eyepiece 7 is an electronic eyepiece. In addition, the imaging device 8 can also be a reflecting mirror, and at this time, the eyepiece 7 is a convex lens with a certain magnification.

[0040] The present utility model further includes an upper light source 10 arranged above the indenter 4. Since the actual size of the particulate sample a is very small, before the crushing experiment, it is necessary to align the indenter 4 with the particulate sample a. Therefore, setting the upper light source 10 is more convenient for the alignment operation before the experiment; at the same time, it is precisely because after the indenter 4 comes into contact with the particulate sample a, the upper light source 10 will be blocked by the indenter 4, and at this time, the situation of the particulate sample a cannot be observed. Therefore, the lower light source 6 designed by the present utility model is particularly important and can provide supplementary light for observing the crushing process.

[0041] The above test stand 1 is rotationally and movably fitted with an adjustable turntable 20. A plurality of mounting grooves 201 are arranged on the turntable 20, and an objective lens 5 is installed in each mounting groove 201. The magnification ratios of the objective lenses 5 are different and can be replaced according to different requirements during the experiment. By combining different objective lenses 5 with the imaging device 8, different magnification ratios can be achieved.

[0042] The above test stand 1 is slidably installed with an X-axis adjustment plate 30 along the X-axis direction, and a Y-axis adjustment plate 40 is slidably installed on the X-axis adjustment plate 30 along the Y-axis direction. The X-axis adjustment plate 30 and the Y-axis adjustment plate 40 share an adjustment rod 50. The adjustment rod 50 is used to control the X-axis movement of the X-axis adjustment plate 30 and the Y-axis movement of the Y-axis adjustment plate 40; the stage 2 is installed on the Y-axis adjustment plate 40. During the experiment, especially when aligning the indenter 4 with the particulate sample a, the operator adjusts the positions of the Y-axis adjustment plate 30 and / or the Y-axis adjustment plate 40 by turning different parts of the adjustment rod 50, so as to adjust the relative positions of the stage 2 / glass slide 3 / particulate sample a and the indenter 4.

[0043] The above test stand 1 is installed with a Z-axis driving device 60 through a bracket. The output end of the Z-axis driving device 60 is installed with a lifting seat 70; the indenter 4 is installed in the lifting seat 70. In this embodiment, the above Z-axis driving device 60 performs a coarse adjustment at the 0.01 mm level through a high-precision servo linear motor, and then performs a fine adjustment of a constant displacement at the 5 nm level through a piezoelectric ceramic control system. The overall movement process of the Z-axis driving device 60 is controlled by software at high speed to ensure the accuracy of the displacement. The mechanical structure related to the Z-axis driving device 60 can be realized by using the prior art and will not be elaborated here.

[0044] Furthermore, a force-displacement sensor 80 is installed inside the lifting seat 70, and the indenter 4 is installed at the detection end of the force-displacement sensor 80. Through high-precision displacement and pressure control, the present utility model can collect the stress-strain curve after the indenter 4 is loaded onto a single-particle sample a, and analyze the particle crushing force from the mutation point of the curve; during the test, the morphology of the particles before and after pressing and the size information of the particles can also be observed through the eyepiece 7.

[0045] The present utility model further includes a housing 90 covering the outside of the test stand 1, and the housing 90 has a flip cover 901 that can be opened and closed. The housing 90 can provide a relatively stable test environment and will not be interfered by external factors. A handle 902 can be provided on the flip cover 901 for easy opening and closing.

[0046] The present utility model also discloses a measurement method using the above single-particle mechanical property test system, including the following steps:

[0047] Step 1: Disperse the particle sample a to be measured in a specific dispersant (such as ethanol) to prepare a dispersion liquid, suck a certain amount of the dispersion liquid with a disposable dropper or pipette, and evenly drop it on the center of the glass slide 3; wait for the dispersant to completely volatilize;

[0048] Step 2: Turn on the single-particle mechanical property test system, connect the optical path and open the test software; fix the glass slide 3 to the stage 2, adjust the observation area, find the particle sample a to be tested, and align it with the indenter 4;

[0049] Step 3: After adjusting the Z-axis position of the indenter 4 to a suitable height, set the parameters in the test software and start the experiment;

[0050] Step 4: Continuously press down (displacement control) or apply a specific pressure (pressure control) using the indenter 4, and record the relationship curve between the stress and the compression displacement of the particle sample a.

[0051] The above embodiments and diagrams do not limit the product form and style of the present utility model. Any appropriate changes or modifications made by those of ordinary skill in the art shall be regarded as not departing from the patent scope of the present utility model.

Claims

1. A single particle mechanical properties testing system, characterized by: It includes a test stand, a stage, a slide, a pressure head, an objective lens, a lower light source, an eyepiece, an imaging device and a refractive single lens; The stage is adjustably mounted on the test frame and is provided with a through hole; the stage is capable of adjusting the position of the XY axis relative to the test frame; The glass slide spans over the through hole and is used for placing the particle sample to be tested; The pressure head is mounted above the stage so as to be lifted and lowered along the Z-axis direction; The objective lens is arranged below the through hole; The lower light source is arranged on the side below the objective lens; The eyepiece is arranged on the surface of the test frame; The imaging device is arranged in the test frame; The refractive single lens is arranged below the objective lens, and its reflective surface faces the objective lens and the imaging device at the same time; the refractive single lens refracts the light emitted by the lower light source to the direction of the objective lens, and reflects the light in the direction of the objective lens to the imaging device through the reflective surface, and the imaging device presents the collected image to the eyepiece.

2. The single particle mechanical properties testing system according to claim 1, characterized in that: The imaging device is a CCD camera, and the eyepiece is an electronic eyepiece.

3. The single particle mechanical properties testing system according to claim 1, characterized in that: The imaging device is a reflector, and the eyepiece is a convex lens.

4. The single particle mechanical properties testing system according to claim 1, characterized in that: It also includes an upper light source arranged above the pressure head.

5. The single particle mechanical property testing system according to claim 1, characterized in that: An adjustable turntable is rotatably provided in the test frame, and a plurality of mounting slots are arranged on the turntable. An objective lens is installed in each mounting slot, and the magnification of each objective lens is different.

6. The single particle mechanical property testing system according to claim 1, characterized in that: An X-axis adjustment plate is slidably installed on the test frame along the X-axis direction, and a Y-axis adjustment plate is slidably installed on the X-axis adjustment plate along the Y-axis direction. The X-axis adjustment plate and the Y-axis adjustment plate share an adjustment rod, and the adjustment rod is used to control the X-axis movement of the X-axis adjustment plate and the Y-axis movement of the Y-axis adjustment plate; the stage is installed on the Y-axis adjustment plate.

7. The single particle mechanical property testing system according to claim 1, characterized in that: A Z-axis driving device is installed on the test frame through a bracket, and a lifting seat is installed at the output end of the Z-axis driving device; the pressure head is installed in the lifting seat.

8. The single particle mechanical property testing system according to claim 7, characterized in that: A force displacement sensor is installed in the lifting seat, and the pressure head is installed at the detection end of the force displacement sensor.

9. The single particle mechanical property testing system according to claim 1, characterized in that: It also includes a shell which is arranged outside the test frame, and the shell has a flip cover which can be opened and closed movably.

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