Measurement method for measuring compressive strength of particles

Abstract

A measurement method for measuring strength of particles, according to an embodiment of the present invention, may include the steps of: loading a particle sample into a sample loading space of a chamber unit; applying vibrations to the chamber unit by using a vibration generation unit so as to uniformly distribute the particle sample; and lowering an upper pressing unit at a predetermined speed to compress the particle sample and measure strength.

Description

Method for measuring the compressive strength of particles

[0001] The present invention relates to a method for measuring the compressive strength of a particle.

[0002]

[0003] As technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and accordingly, extensive research is being conducted on secondary batteries that can meet various needs.

[0004] In terms of the shape of secondary batteries, there is a high demand for square secondary batteries and pouch-type secondary batteries that can be applied to products such as mobile phones due to their thin thickness. In terms of materials, there is a high demand for lithium secondary batteries such as lithium-ion batteries and lithium-ion polymer batteries that have advantages such as high energy density, discharge voltage, and output stability.

[0005] In addition, the secondary battery includes an electrode assembly comprising a positive electrode, a negative electrode, and a separator structure interposed between the positive electrode and the negative electrode. The positive electrode is rolled in the final stage of electrode manufacturing to secure energy density and conductivity. During this process, numerous cracks may occur in the positive electrode active material, and broken positive electrode active material can be a fatal cause of reduced lifespan, gas generation, and reduced thermal stability. Therefore, in order to measure the compressive strength of the positive electrode active material, the strength of each particle of the positive electrode active material is measured using a nano-indenter. However, this method has the problem that accurate strength cannot be measured because it only measures a very small number of particles contained in a large number of positive electrode active materials.

[0006] In addition, secondary batteries use a mixture of two or more types of positive electrode active materials in the positive electrode, making it difficult to accurately measure the compressive strength of the mixed positive electrode active material powder, which causes a problem in that the electrochemical performance of the manufactured secondary battery deteriorates.

[0007]

[0008] One object of the present invention is to provide a method for measuring the compressive strength of heterogeneous particles in which two or more particles are mixed.

[0009]

[0010] A method for measuring the strength of heterogeneous particles according to one embodiment of the present invention may include the steps of: loading a particle sample into a sample receiving space of a chamber; applying vibration to the chamber using a vibration generating unit to evenly distribute the particle sample; and lowering an upper pressurizing unit at a predetermined speed to compress the particle sample and measure the strength.

[0011] In the step of applying vibration to the chamber section using the vibration generating section to evenly distribute the particle sample, the vibration intensity and vibration time of the vibration generating section can be adjusted according to the particle size of the particle sample.

[0012] The above particle sample may be a heterogeneous particle containing a mixture of large-diameter particles and small-diameter particles.

[0013] The average particle size of the above large particle size particles may be 7 µm to 35 µm, and the average particle size of the above small particle size particles may be 1 µm to 5 µm.

[0014] The above particle sample may be at least one selected from lithium metal oxide or lithium metal salt.

[0015] The above particle sample can be accommodated in the chamber portion in an amount of 1 / 3 to 2 / 3 of the volume of the sample accommodation space.

[0016] In the step of lowering the upper pressurizing unit at a predetermined speed to compress the particle sample and measure the strength, the upper pressurizing unit can move at a speed of 0.005 mm / s to 1 mm / s.

[0017] In the step of lowering the upper pressurizing unit at a predetermined speed to compress the particle sample and measure the strength, the size of the pressure applied to the particle sample can be measured in real time and transmitted to the data collection unit.

[0018] The strength of a particle sample can be measured by starting from the point when the magnitude of the pressure applied to the particle sample reaches 10 MPa.

[0019]

[0020]

[0021] A particle strength measurement method according to one embodiment of the present invention can effectively measure strength for heterogeneous particles.

[0022]

[0023] FIG. 1 is a schematic diagram of a particle strength measuring device according to one embodiment of the present invention.

[0024] Figure 2 is a photograph of a particle strength measuring device used in an embodiment of the present invention.

[0025] Figures 3 and 4 show the results of a compressive strength measurement experiment according to an embodiment of the present invention.

[0026] Figures 5 and 6 show the results of particle size analysis of a particle sample according to an embodiment of the present invention.

[0027] Figures 7 and 8 show SEM images of particle samples before and after compression according to an embodiment of the present invention.

[0028]

[0029] In this specification, the terms first, second, and third, etc. are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "singular" and "comprising" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising" as used herein specifies a particular feature, region, integer, step, operation, element, and / or component, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0031] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0032] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0033] In this specification, the term "combination(s) thereof" described in the expression in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expression in the Makushi format, and means including any one or more selected from the group consisting of said components.

[0034] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0035]

[0036] One embodiment of the present invention provides a particle strength measuring device for measuring the strength of particles of various particle sizes.

[0037] Figure 1 is a schematic diagram of a particle intensity measuring device according to one embodiment of the present invention.

[0038] Referring to FIG. 1, a particle strength measuring device (10) according to one embodiment of the present invention may include an upper jig part (100), a chamber part (300), a lower jig part (200), and a vibration generating part (400).

[0039] The upper jig portion (100) may include an upper pressurizing unit (110), an upper flange (120), and an upper connecting rod (130).

[0040] The upper pressurizing unit (110) may be positioned below the upper flange (120), the upper connecting rod (130) may be positioned above the upper flange (120), and the upper pressurizing unit (110) may be inserted into the through hole (310) of the chamber portion (300) described later from above the through hole (310).

[0041] The upper jig part (100) may be electrically connected to a speed control part (not shown), and the vertical movement speed may be controlled by the speed control part. The transmission control part may be electrically connected to the upper connecting rod (130) or the upper connecting rod (130). Meanwhile, the upper jig part (100) may be supported by a support part (not shown).

[0042] The upper pressurizing unit (110), upper flange (120) and upper connecting rod (130) may have the same central axis in the vertical direction.

[0043] The ratio (L1 / L3) of the length (L1) of the upper pressurizing unit to the depth (L3) of the above-described through hole may be 1 to 1.5. By satisfying the above range, it is preferable to effectively pressurize the particles accommodated in the accommodation space of the chamber portion (300) described later.

[0044] The upper pressurizing unit (110) can move up and down within the upper flange (120) and the upper connecting rod (130), and the downward exposure length of the upper flange (120) can be adjusted by an electrically connected control unit. By configuring it in this way, the length introduced into the receiving space located in the chamber section (300) described later can be adjusted, and the length of the upper pressurizing unit (110) can be adjusted according to the amount of particles to be measured, which is preferable.

[0045] In one embodiment of the present invention, the horizontal cross-section of the upper pressurizing unit (110) may be circular with a diameter of 8 mm and a vertical length of 32 mm. The upper flange may have a horizontal diameter of 40 mm and a vertical height of 15 mm, and the upper connecting rod may have a horizontal cross-section with a diameter of 12 mm and a length of 70 mm.

[0046]

[0047] The above chamber portion (300) may have a through hole (310) formed in the central portion in the vertical direction (z-axis direction).

[0048] The above chamber part (300) can be electrically connected to the vibration generating part (400).

[0049] The vibration generating unit (400) can apply vibration to the particle samples loaded into the receiving space formed in the chamber unit (300) so that the particle samples are uniformly dispersed. Meanwhile, the vibration intensity and / or vibration time of the vibration generating unit (400) can be adjusted according to the particle size and type of the particle samples. By applying vibration to the particle samples as described above, the gap between particles can be minimized, thereby reducing the measured particle strength error range, which is preferable.

[0050] Meanwhile, the vibration generating unit (400) can be electrically connected to a control unit (not shown), and the vibration intensity and vibration time can be adjusted according to the characteristics of the particle sample input to the control unit.

[0051] An additional support plate (not shown) may be positioned at the inner lower portion of the above-mentioned through hole (310). Including the support plate is preferable because it allows for stable accommodation of particle samples. However, the present invention is not limited thereto.

[0052] Meanwhile, in the present invention, the maximum particle size of the particle sample may be 35 μm or less.

[0053] Meanwhile, in the present invention, the maximum particle size of the particle sample may be 35 μm or less. The particle sample may be a heterogeneous sample in which large-diameter particles and small-diameter particles are mixed, and the average particle size of the large-diameter particles may be 7 μm to 35 μm, and the average particle size of the small-diameter particles may be 1 μm to 5 μm.

[0054] The above particle sample may be at least one selected from lithium metal oxide or lithium metal salt.

[0055] The particle sample can be accommodated in 1 / 3 to 2 / 3 of the volume of the accommodation space. By accommodating the particle sample in the above range, it is possible to prevent particle leakage during the strength measurement process and reduce the error range of the measured particle strength, which is desirable.

[0056] In one embodiment of the present invention, the chamber portion (300) may have a horizontal cross-sectional diameter of 40 mm and a height of 25 mm, and the horizontal cross-sectional diameter of the through hole (310) may be 8 mm.

[0057]

[0058] The lower jig (200) may include a lower support unit (210), a lower flange (220), and a lower connecting rod (230).

[0059] Meanwhile, the lower support unit (210) described later can be inserted into the inside of the through hole (310) from the lower portion of the through hole (310).

[0060] The ratio (L2 / L3) of the length (L2) of the lower support unit (210) and the depth (L3) of the through hole (310) may be 0.2 to 0.3. The lower support unit (210) having the above ratio is inserted into the through hole (310) in the downward direction of the through hole (310), thereby forming a receiving space capable of receiving particles formed by the upper surface of the lower support unit (210) and the internal space of the through hole (310), and is preferably stably supported so that the particles received inside do not leak to the outside even when pressurized.

[0061] The length of the lower support unit (310) inserted into the through hole (310) may be the entire length of the lower support unit (310), specifically, may be 1 / 5 or more, and more specifically, may be 1 / 2 or more.

[0062] Meanwhile, the lower support unit (310) is equipped with a pressure sensor unit (not shown) to measure the pressure applied to the particle sample in real time.

[0063] The lower jig part (200) and the chamber part (300) may be an integrated structure, and specifically, the lower flange (220) and the chamber part (300) may be a structure in which they are coupled to a separate coupling member (not shown). As long as the lower flange (220) and the chamber part (300) can be stably coupled and disengaged, the structure and form of the coupling member are not particularly limited. By forming a structure for coupling or disengaging the lower flange (220) and the chamber part (300) as described above, it is preferable to effectively clean the device after measuring the strength of each sample, thereby reducing measurement errors.

[0064] In one embodiment of the present invention, the lower support unit may have a horizontal cross-sectional diameter of 8 mm and a vertical length of 6 mm. The lower flange may have a horizontal diameter of 40 mm and a vertical height of 15 mm, and the lower connecting rod may have a horizontal cross-sectional diameter of 12 mm and a vertical length of 70 mm.

[0065] In one embodiment of the present invention, the upper jig part (100), the lower jig part (200), and the chamber part (300) may be made of steel or ceramic material.

[0066]

[0067] A particle intensity measurement method according to another embodiment of the present invention can utilize the particle intensity measurement device.

[0068] The lower jig part and the chamber part of the particle intensity measuring device are stably connected, and then a particle sample is loaded into the receiving space formed in the chamber part, and then the vibration generating part is operated to uniformly distribute the received particle sample.

[0069] At this time, the vibration intensity and / or vibration time of the vibration generating unit can be controlled according to the particle size of the particle sample. Meanwhile, the vibration generating unit can be electrically connected to the control unit, and the vibration intensity and vibration time can be adjusted according to the characteristics of the particle sample input to the control unit. At this time, when the particle size of the target particle sample and the quantity ratio information according to the particle size are input to the control unit, the vibration intensity and vibration time of the vibration generating unit can be automatically controlled by the control unit to apply vibration to the particle sample.

[0070] At this time, the maximum particle size of the particle sample may be 35 μm or less, and the particle sample may be accommodated in 1 / 3 to 2 / 3 of the volume of the accommodation space. By accommodating the particle sample within the above range, it is possible to prevent particle leakage during the strength measurement process and reduce the error range of the measured particle strength, which is desirable.

[0071]

[0072] Next, the upper jig section is moved downward, and the upper pressurizing unit is inserted into the receiving space to pressurize the particle sample.

[0073] At this time, the descending speed of the upper pressurizing unit may be 1 mm / s or less, specifically 0.005 to 1 mm / s, and more specifically 0.01 to 0.5 mm / s, 0.01 to 0.1 mm / s, or 0.01 to 0.05 mm / s.

[0074] When the above-mentioned descent speed is satisfied, particle strength can be effectively measured. Exceeding the above-mentioned descent speed range results in rapid collisions between particles, which can cause cracks in the particles, increasing the error in the measured strength value, which is undesirable. Decreasing the descent speed range below the above-mentioned range makes mechanical operation difficult and makes it difficult to accurately measure particle strength, which is undesirable.

[0075]

[0076] The magnitude of the pressure applied to the above particle sample is measured by a sensor unit provided in the lower jig unit, and the value can be transmitted to a data collector in real time. At this time, the work hardening point can be confirmed using the pressure value and displacement transmitted from the data collector.

[0077] Meanwhile, in the present invention, the strength of the particle sample can be calculated by the data collection unit using the point in time when the magnitude of the pressure applied to the particle sample reaches 10 MPa as the starting point.

[0078] Hereinafter, embodiments of the present invention will be described in more detail through examples. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0079]

[0080] Example

[0081] Particle strength was measured for the particles shown in the table below. The samples shown in the table below may be lithium metal oxides, and are specifically cathode active materials for lithium secondary batteries.

[0082]

[0083] Chemical composition D10 D50 D90 Sample A (Poly-poly) LiNi 0.9 Co 0.04 Mn 0.04 Al 0.02 O210.713.618.2 Sample B (Poly small particle) LiNi 0.86 Co 0.06 Mn 0.07 Al 0.01 O22.33.65.3 Sample C(Single)LiNi 0.86 Co 0.06 Mn 0.07 Al 0.01 O22.53.55.1

[0084] Meanwhile, the above samples were mixed as described in Table 2 below to prepare particle sample 1 and particle sample 2, and the particle strength measuring device is shown in Fig. 2.

[0085] After purging the inside of the sample receiving space of the chamber section with inert gas, the sample is loaded so that it fills about 1 / 3 to 2 / 3 of the receiving space, and then the vibration generator is operated for 10 to 30 seconds to ensure that the filled sample is uniformly distributed. At this time, the lower support unit of the lower jig section is inserted into the sample space to stably support the particle sample.

[0086] Next, the upper jig section is lowered at a descending speed controlled by the control section at 0.01 mm / s, and the upper pressurizing unit is inserted into the sample receiving space to pressurize the internal sample particles. The pressurization end point is 600 MPa.

[0087] At this time, the pressure applied to the sample particles is detected by a pressure sensor equipped in the lower support unit, and the pressure value can be checked in real time, and the results are shown in Figs. 3 and 4. At this time, the start point of the strength measurement was set to the point when the compression pressure reached 10 MPa.

[0088] After completing the particle strength test, the results of the particle size analysis are shown in Table 2 below.

[0089]

[0090] Sample 1 Sample 2 Mixed weight ratio Sample A: Sample B 80 wt%: 20 wt% Sample A: Sample C 80 wt%: 20 wt% Stress at 1.5 mm (MPa) 271 ± 23 385 ± 18 Max Hardening Displacement (mm) 1.27 ± 0.08 1.65 ± 0.08 Max Hardening Stress (MPa) 300 ± 37 306 ± 25 D[3,2] Before pressurization 9.6 8.7 After pressurization 0.4 6.6 D[4,3] Before pressurization 12.9 9.8 After pressurization 12.6 11.7 D(10) Before pressurization 6.0 1.1 After pressurization 4.0 3.0 D(50) Before pressurization 12.6 9.9 After pressurization 12.5 11.5 D(90) Before pressurization 20.2 18.5 After pressurization Post 20.219.5

[0091] In Table 2 above, “Stress at 1.5 mm” refers to the output pressure value when the upper jig moves 1.5 mm compared to the initial height.

[0092] The compression test results of samples 1 and 2 are shown in Figs. 3 to 6.

[0093]

[0094] Figures 5 and 6 show the particle size analysis results of samples 1 and 2 before and after compression.

[0095] Referring to FIGS. 5 and 6, it can be confirmed that the particle size of both Sample 1 and Sample 2 decreased when compressed to 600 MPa, and it can be confirmed that the particle size decrease of Sample 1 is relatively greater than that of Sample 2.

[0096] Figure 7 shows SEM images of sample 1 before and after compression, and Figure 8 shows SEM images of sample 2 before and after compression.

[0097]

[0098] In the present invention, the particle strength measuring device and particle strength measuring method can confirm the compressive strength of a positive electrode active material to be used in a lithium secondary battery, thereby preventing problems caused by crushing of the positive electrode active material that may occur in the subsequent lithium secondary battery manufacturing process.

[0099]

[0100] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

[0101] Accordingly, the actual scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A step of loading a particle sample into the sample receiving space of the chamber; A step of applying vibration to the chamber section using a vibration generating section to evenly distribute the particle sample; and A step of lowering the upper pressurizing unit at a predetermined speed to compress the particle sample and measure the strength; comprising; Method for measuring particle intensity.

2. In paragraph 1, In the step of evenly distributing particle samples by applying vibration to the chamber using the vibration generating unit, The vibration intensity and vibration time of the vibration generating unit are adjusted according to the particle size of the particle sample. Method for measuring particle intensity.

3. In paragraph 1, The above particle sample is a heterogeneous particle mixed with large-diameter particles and small-diameter particles. Method for measuring particle intensity.

4. In paragraph 3, The average particle size of the above large particle size is 7 ㎛ to 35 ㎛, The average particle size of the above small particle size particles is 1 ㎛ to 5 ㎛. Method for measuring particle intensity.

5. In paragraph 1, The above particle sample is at least one selected from lithium metal oxide or lithium metal salt. Method for measuring particle intensity.

6. In paragraph 1, The above particle sample is accommodated in the chamber portion in 1 / 3 to 2 / 3 of the volume of the sample accommodation space. Method for measuring particle intensity.

7. In paragraph 1, In the step of measuring the strength by lowering the upper pressurizing unit at a predetermined speed to compress the particle sample, The upper pressurizing unit moves at a speed of 0.005 mm / s to 1 mm / s, Method for measuring particle intensity.

8. In paragraph 1, In the step of measuring the strength by lowering the upper pressurizing unit at a predetermined speed to compress the particle sample, The magnitude of the pressure applied to the above particle sample is measured in real time and transmitted to the data collection unit. Method for measuring particle intensity.

9. In paragraph 8, The strength of a particle sample is measured starting from the point when the pressure applied to the particle sample reaches 10 MPa. Method for measuring particle intensity.

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