Analytical method and analytical device for foreign matter in positive electrode active material

Abstract

The present application discloses an analysis method and an analysis device for foreign matter in positive electrode active materials. The analysis method for foreign matter in positive electrode active materials comprises: dispersing the positive electrode active material in a solvent to form a suspension; using a driving member to transport the suspension to a filtering device to obtain a retained object, wherein the flow rate of the suspension is Lr, in units of L / min, and the filtering device comprises a filtering member; analyzing the retained object to obtain the size and element type information of the foreign matter; the Lr satisfies: Lr = (K×J×R) / (D 50 ×S), where K is 1×10 ‑2 ‑3×10 ‑2 , J is the pump speed of the driving element, in rpm; R is the pore size of the filter element, in μm; D 50 is the particle size corresponding to when the cumulative particle size distribution percentage of the positive electrode active material reaches 50%, in μm; S is the solid content of the suspension, in %. Thus, foreign matter in the positive electrode active material can be efficiently separated, and the foreign matter loss during the analysis process is low, which helps to improve the efficiency and accuracy of foreign matter analysis.

Description

Technical Field

[0001] The present application relates to the field of positive electrode active material detection, and in particular, to an analysis method and an analysis device for foreign matter in positive electrode active materials. Background Art

[0002] Positive electrode active materials are key components in metal ion batteries such as lithium-ion batteries and sodium-ion batteries, and directly affect the energy density, cycle life, safety and cost of the battery. With the rapid development of new energy vehicles, 3C electronic products and energy storage batteries, the market demand for positive electrode active materials continues to grow, and technological innovation and capacity expansion have become the main trends in the development of the industry. However, the production and preparation process of positive electrode active materials and raw materials will inevitably introduce some foreign matter. The presence of foreign matter will reduce the specific capacity of the positive electrode active material and cause the battery performance to deteriorate. Therefore, it is very important to detect and monitor foreign matter in positive electrode active materials.

[0003] It should be noted that the above statements are only used to provide background technical information related to the present application and do not necessarily constitute prior art. Summary of the invention

[0004] In the first aspect of the present application, the present application proposes a method for analyzing foreign matter in a positive electrode active material, comprising: dispersing the positive electrode active material in a solvent to form a suspension; using a driving member to transport the suspension to a filtering device to obtain a retentate, wherein the flow rate of the suspension is Lr, in units of L / min, and the filtering device includes a filtering member; analyzing the retentate to obtain the size and element type information of the foreign matter; the Lr satisfies: Lr = (K×J×R) / (D 50 ×S), where K is 1×10 -2 -3×10 -2 , J is the pump speed of the driving element, in rpm; R is the pore size of the filter element, in μm; D 50 is the particle size corresponding to when the cumulative particle size distribution percentage of the positive electrode active material reaches 50%, in μm; S is the solid content of the suspension, in %. Thus, foreign matter in the positive electrode active material can be efficiently separated, and the foreign matter loss during the analysis process is low, which helps to improve the efficiency and accuracy of foreign matter analysis.

[0005] In some embodiments, Lr is 0.5 L / min-1.5 L / min. Thus, the analysis time can be shortened and the analysis efficiency can be improved by a faster flow rate.

[0006] In some embodiments, R is greater than D 100 , D 100The particle size corresponding to the cumulative particle size distribution percentage of the positive electrode active material reaches 100%, and the unit is μm. In this way, the interception of foreign matter with a larger particle size can be achieved.

[0007] In some embodiments, R = 25.67 μm + 1.1D 100 This helps the positive electrode active material pass through the filter as completely as possible and traps foreign matter, thereby improving the accuracy of the analysis results.

[0008] In some embodiments, D 100 The particle size is 10 μm to 30 μm. Therefore, it is suitable for analyzing foreign matter in various positive electrode active materials.

[0009] In some embodiments, J is 0.2 L / min-0.6 L / min, thereby facilitating sufficient filtration of the suspension.

[0010] In some embodiments, D 50 The diameter of the cathode active material is 3 μm-10 μm; and / or the diameter of S is 5%-15%. This helps to improve the uniformity of the dispersion of the cathode active material in the suspension.

[0011] In some embodiments, after obtaining the intercepted material, the method further comprises: using a driving member to transport the solvent to the filtering device, thereby helping to reduce foreign matter loss and reduce waste of positive electrode active materials.

[0012] In some embodiments, the analysis of the intercepted material includes at least one of X-ray fluorescence spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, and transmission electron microscopy-energy dispersive X-ray spectroscopy, thereby facilitating accurate analysis to obtain information on the size and element type of the foreign matter.

[0013] In the second aspect of the present application, the present application proposes an analysis device, which adopts the above-mentioned analysis method. Therefore, the analysis device has all the characteristics and advantages of the above-mentioned analysis method, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0015] Figure 1 This is a schematic diagram of the structure of an analysis device according to an embodiment of the present application.

[0016] Figure 2 This is a partial structural schematic diagram of a filtering device according to an embodiment of the present application.

[0017] Figure 3 for Figure 2Section view at AA in the middle.

[0018] Figure 4 This is a partial structural schematic diagram of a filtering device according to another embodiment of the present application.

[0019] Figure 5 yes Figure 4 Cross-sectional view at BB in the middle.

[0020] Figure 6 This is an X-ray fluorescence spectrum analysis diagram of the foreign matter in Example 1.

[0021] Figure 7 This is an X-ray fluorescence spectrum analysis diagram of the foreign matter in Example 2.

[0022] Figure 8 This is a diagram of the retained material on the filter membrane surface after filtration in Comparative Example 1.

[0023] Reference numerals:

[0024] Filter device 1; drive member 2; hose 3; liquid storage container 4;

[0025] First housing 10; containing groove 11; first sub-groove 111; internal thread 1111; second sub-groove 112; first channel 12; third sub-channel 121; fourth sub-channel 122;

[0026] The second shell 20 ; the second channel 21 ; the first sub-channel 211 ; the second sub-channel 212 ; the connecting portion 22 ; the shell body 23 ; the first sub-shell 231 ; the second sub-shell 232 ; the first matching portion 2321 ; the external thread 23211 ; the second matching portion 2322 ; and the anti-slip portion 24 . DETAILED DESCRIPTION

[0027] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the drawings, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of actually identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0028] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0029] In the description of this application, regardless of whether the words "about" or "approximately" are used, all the numbers disclosed herein are approximate values. The value of each number may differ by less than 10% or a reasonable difference considered by those skilled in the art, such as 1%, 2%, 3%, 4% or 5%.

[0030] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0031] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. "First feature" and "second feature" may include one or more of the features.

[0032] In the description of the present application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for examples and may be any technical feature connected by "and / or" in the present application.

[0033] There are many types of foreign matter in the positive electrode active materials. Among them, since the pipes, screens and other equipment used in the preparation of positive electrode active materials are made of metal materials, metal foreign matter will be mixed into the final positive electrode active materials, for example, single substances, oxides, alloys, etc. corresponding to metal elements such as Fe and Cr. In addition to reducing the specific capacity of the positive electrode active material and causing the battery performance to deteriorate, the presence of metal foreign matter may also dissolve in the electrolyte and cause side reactions, affecting the service life and safety of the battery. Therefore, the analysis of metal foreign matter in positive electrode active materials is particularly important. The methods for analyzing metal foreign matter in positive electrode active materials in related technologies have the problems of multiple sample transfers during the separation process of metal foreign matter, low analysis efficiency, easy loss of metal foreign matter during the sample preparation process, and easy mixing with dust and other debris in the air, which has a great impact on the accuracy and efficiency of the analysis of metal foreign matter.

[0034] In the present application, by optimizing the design of the key influencing factors of foreign matter analysis in positive electrode active materials and reducing the manual operations in the foreign matter separation process, the separation steps can be reduced and the separation time can be shortened while ensuring that the foreign matter and the positive electrode active materials are accurately separated, thereby effectively improving the efficiency and accuracy of foreign matter analysis in positive electrode active materials.

[0035] In the first aspect of the present application, the present application proposes a method for analyzing foreign matter in a positive electrode active material, referring to Figure 1 , including: dispersing the positive electrode active material in a solvent to form a suspension; using a driving member 2 to transport the suspension to a filtering device 4 to obtain a retentate, wherein the flow rate of the suspension is Lr, in units of L / min, and the filtering device includes a filtering member; analyzing the retentate to obtain the size and element type information of the foreign matter; the Lr satisfies: Lr = (K×J×R) / (D 50 ×S), where K is 1×10 -2 -3×10 -2 , J is the pump speed of the driving element, in rpm; R is the pore size of the filter element, in μm; D 50 is the particle size corresponding to when the cumulative particle size distribution percentage of the positive electrode active material reaches 50%, in μm; S is the solid content of the suspension, in %. Thus, the flow rate of the suspension matches the key influencing factor in the separation of foreign matter in the positive electrode active material, and the foreign matter in the positive electrode active material can be efficiently separated, and the foreign matter loss during the analysis process is low, which helps to improve the efficiency and accuracy of foreign matter analysis.

[0036] In some embodiments, reference Figure 1, the driving member 2 needs to suck out the suspension in the liquid storage container 4 through the hose 3, and transmit the sucked suspension to the filter device 4 through the hose 3. The above parameter K is related to the inner diameter of the hose, the length of the hose and the inner wall material of the hose, among which the inner wall material of the hose will affect the friction resistance between the inner wall of the hose and the suspension. Taking the silicone tube with a diameter of 5mm-8mm as an example, its K value is about 2×10 -2 .

[0037] As an example, the liquid storage container 4 may be a beaker with a cover.

[0038] As an example, the filter element may be a filter membrane.

[0039] As an example, the driving member may be, but is not limited to, a peristaltic pump, an impeller pump, or the like.

[0040] It should be noted that the solvent used to disperse the positive electrode active material in the present application is not particularly limited, as long as the positive electrode active material can be evenly dispersed therein to form a suspension and does not react with the positive electrode active material and foreign matter. For example, the solvent can be water and / or ethanol.

[0041] In some embodiments, Lr is 0.5 L / min-1.5 L / min. Thus, the analysis time can be shortened and the analysis efficiency can be improved by a faster flow rate.

[0042] As an example, Lr may be 0.5 L / min, 0.6 L / min, 0.7 L / min, 0.8 L / min, 0.9 L / min, 1.0 L / min, 1.1 L / min, 1.2 L / min, 1.3 L / min, 1.4 L / min, or 1.5 L / min.

[0043] When Lr is within the aforementioned range, the flow rate of the suspension is faster. Under the premise of the same suspension volume, the separation efficiency of foreign matter in the positive electrode active material can be improved without causing a large amount of positive electrode active material to accumulate on the surface of the filter element, making it impossible to complete the filtration.

[0044] In some embodiments, R is greater than D 100 , D 100 The particle size corresponding to the cumulative particle size distribution percentage of the positive electrode active material reaches 100%, and the unit is μm. Therefore, the positive electrode active material with a particle size smaller than the pore size of the filter element can pass through the filter element, while the foreign matter with a particle size larger than the pore size of the filter element will be intercepted by the filter element, thereby achieving the separation of foreign matter with a larger particle size.

[0045] D 100 , the particle size corresponding to when the cumulative particle size distribution percentage of a sample reaches 100%. Its physical meaning is that particles with a particle size larger than it account for 0%, and particles with a particle size smaller than it account for 100%. 100Often used to indicate the maximum particle size of a powder.

[0046] The volume particle size distribution can be tested by methods known in the art. For example, GB / T19077-2016 can be referred to, and a Malvern laser particle size analyzer can be used for characterization testing, such as a Malvern Mastersizer-3000 or other instrument.

[0047] In some embodiments, R = 25.67 μm + 1.1D 100 This helps the positive electrode active material pass through the filter as completely as possible and traps foreign matter, thereby improving the accuracy of the analysis results.

[0048] In the process of testing the volume distribution particle size of the positive electrode active material by the particle size analyzer, the positive electrode active material solution is in a state of continuous stirring, at which time the single particles can be evenly dispersed, and there is less adhesion between the positive electrode active material particles. In the process of conveying the suspension, real-time stirring cannot be performed, and at this time, a large amount of adhesion will occur between the positive electrode active materials, resulting in the actual maximum particle size of the positive electrode active material being larger than the D obtained by the particle size analyzer test when the suspension passes through the filter. 100 Therefore, when the pore size of the filter element satisfies the above relationship, the positive electrode active material particles that are adhered can still fully pass through the filter element, thereby intercepting the particles with larger particle sizes.

[0049] In some embodiments, D 100 The particle size is 10 μm to 30 μm. Therefore, it is suitable for analyzing foreign matter in various positive electrode active materials.

[0050] As an example, D 100 It may be 10 μm, 15 μm, 17 μm, 19 μm, 21 μm, 23 μm, 25 μm, 27 μm, 29 μm or 30 μm.

[0051] In some embodiments, J is 0.2 L / min-0.6 L / min, thereby facilitating sufficient filtration of the suspension.

[0052] As an example, J can be 0.2 L / min, 0.25 L / min, 0.3 L / min, 0.35 L / min, 0.4 L / min, 0.45 L / min, 0.5 L / min, 0.55 L / min, 0.6 L / min.

[0053] When J is within the aforementioned range, it is helpful to extract the suspension from the liquid storage container and control the flow rate of the suspension to be moderate, thereby reducing the accumulation of positive electrode active materials on the surface of the filter element and improving the separation efficiency.

[0054] In some embodiments, D 50This helps to improve the uniformity of the dispersion of the positive electrode active material in the suspension.

[0055] As an example, D 50 It may be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

[0056] D 50 , the particle size corresponding to the cumulative particle size distribution percentage of a sample reaches 50%. Its physical meaning is that particles with a particle size larger than it account for 50%, and particles with a particle size smaller than it also account for 50%. 50 Also called median diameter or median particle size. 50 Often used to indicate the average particle size of a powder.

[0057] In some embodiments, S is 5%-15%.

[0058] As an example, S may be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%.

[0059] When S is within the aforementioned range, the viscosity of the suspension is moderate, and the frictional resistance between the suspension and the hose for conveying the suspension is small, which is helpful to achieve flow rate control of the suspension.

[0060] In some embodiments, after obtaining the retentate, the method further includes: using a driving member to transport the solvent to the filtering device.

[0061] At the final stage of filtration, the solvent content in the suspension is low. At this time, some of the positive electrode active materials that should pass through the filter element are accumulated on the surface of the filter element due to lack of solvent flushing. Completing the final operation by adding solvent for flushing helps to reduce foreign matter loss and reduce waste of positive electrode active materials.

[0062] In some embodiments, the analysis of the intercepted material includes at least one of X-ray fluorescence spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, and transmission electron microscopy-energy dispersive X-ray spectroscopy, thereby facilitating accurate analysis to obtain information on the size and element type of the foreign matter.

[0063] It should be noted that the foreign matter analysis method described above in the present application is also applicable to foreign matter in negative electrode active materials, foreign matter in conductive agents, etc. Those skilled in the art can make corresponding adjustments based on actual conditions, which will not be elaborated here.

[0064] Reference below Figure 2-Figure 5 A filtering device according to an embodiment of the present application is described.

[0065] like Figure 2-Figure 5As shown, the filtering device includes: a first shell 10 and a second shell 20 .

[0066] The first shell 10 defines a receiving groove 11 and a first channel 12, and the receiving groove 11 is suitable for receiving a filter element (not shown in the figure); the second shell 20 is detachably connected to the first shell 10, and a partial structure of the second shell 20 can be accommodated in the receiving groove 11 and the filter element is clamped between the bottom wall of the receiving groove 11 and the second shell 20, and the second shell 20 defines a second channel 21, the first channel 12 is connected to the second channel 21, and the filter element is located between the first channel 12 and the second channel 21.

[0067] As an example, the material of the first shell 10 and the second shell 20 may be but is not limited to PVC (Polyvinylchloride) and the like.

[0068] The receiving tank 11 and the first channel 12 are connected and arranged, and the receiving tank 11 can receive a filter element, and the filter element can filter metal impurities in the suspension, that is, the metal impurities cannot pass through the filter element but will be retained on the filter element.

[0069] The second shell 20 is detachably connected to the first shell 10 , and the connection method of the second shell 20 and the first shell 10 may be but is not limited to threaded connection, snap-on connection, etc. As an example, the second shell 20 and the first shell 10 are connected by threaded connection.

[0070] Partial structure of the second shell 20 can be accommodated in the accommodating groove 11, that is, partial structure of the second shell 20 and the accommodating groove 11 can cooperate with each other so that partial structure of the second shell 20 can be accommodated in the accommodating groove 11, and partial structure of the second shell 20 can clamp the filter element between the bottom wall of the accommodating groove 11 and the second shell 20, that is, the filter element is arranged on the bottom wall of the accommodating groove 11, and the filter element is clamped between the bottom wall of the accommodating groove 11 and the second shell 20.

[0071] During assembly, the filter element can be placed in the receiving groove 11 first, and then a part of the structure of the second housing 20 is extended into the receiving groove 11 to clamp the filter element between the bottom wall of the receiving groove 11 and the second housing 20, and the second housing 20 is connected to the first housing 10 to complete the assembly. The size of the filter element can be adapted to the size of the receiving groove 11.

[0072] The second shell 20 defines a second channel 21 , the first channel 12 is connected to the second channel 21 , the receiving groove 11 is connected between the first channel 12 and the second channel 21 , the filter is received in the receiving groove 11 and is located between the first channel 12 and the second channel 21 .

[0073] It should be noted that during filtering, the suspension can flow through the second channel 21 of the second shell 20, the filter element, the first channel 12 and then flow out of the filter device. The filter element can effectively filter the suspension and retain the metal impurities in the suspension in the filter element. Moreover, by clamping the filter element between the bottom wall of the receiving groove 11 and the second shell 20, the installation of the filter element can be stabilized, reducing the risk of displacement and wrinkling of the filter element during use, improving the filtering performance, and enhancing the filtering effect of the filtering device. In addition, since the second shell 20 is detachably connected to the first shell 10, it is convenient to disassemble and assemble the filtering device, thereby facilitating the placement, removal or replacement of the filter element, which is conducive to improving the convenience of use of the filtering device.

[0074] Therefore, by making the second shell 20 detachably connected to the first shell 10, the filter device can be easily disassembled and assembled. By making part of the structure of the second shell 20 able to be accommodated in the accommodating groove 11 and the filter element able to be clamped between the bottom wall of the accommodating groove 11 and the second shell 20, the filter element can be firmly fixed, reducing the risk of the filter element shifting or wrinkling during use, which is beneficial to improving the filtering performance of the filter device, thereby facilitating the separation and filtering operation of impurities.

[0075] In some embodiments, Figure 4 and Figure 5 As shown, the second channel 21 is located upstream of the first channel 12. The second channel 21 includes a first sub-channel 211 and a second sub-channel 212. The second sub-channel 212 is connected between the first sub-channel 211 and the first channel 12. From approaching the first sub-channel 211 to away from the first sub-channel 211, the flow area of ​​the second sub-channel 212 gradually increases.

[0076] The second channel 21 is located upstream of the first channel 12 , that is, the suspension first flows through the second channel 21 and then flows through the first channel 12 .

[0077] The second subchannel 212 is connected between the first subchannel 211 and the first channel 12, that is, the first subchannel 211, the second subchannel 212, and the first channel 12 are connected in sequence, and the second subchannel 212 has an end close to the first subchannel 211 and an end away from the first subchannel 211. From the direction close to the first subchannel 211 to the direction away from the first subchannel 211, the flow area of ​​the second subchannel 212 gradually increases, that is, along the flow direction of the suspension, the flow area of ​​the second subchannel 212 gradually increases. In other words, the shape of the second subchannel 212 is constructed to be similar to an inverted funnel.

[0078] By gradually increasing the flow area of ​​the second subchannel 212 from the direction close to the first subchannel 211 to the direction away from the first subchannel 211, the impact force of the suspension flowing through the second subchannel 212 can be reduced, and the risk of the filter being destroyed can be reduced. In addition, such an arrangement can also increase the contact area between the suspension and the filter, avoiding the impact force from being concentrated at one point, thereby further reducing the risk of the filter being destroyed, which is beneficial to improving the reliability of the filter device.

[0079] In some embodiments, Figure 2 and Figure 3 As shown, the second channel 21 is located upstream of the first channel 12, and the first channel 12 includes a third sub-channel 121 and a fourth sub-channel 122. The third sub-channel 121 is connected between the fourth sub-channel 122 and the second channel 21. From approaching the third sub-channel 121 to away from the third sub-channel 121, the flow area of ​​the fourth sub-channel 122 gradually increases.

[0080] The second channel 21 is located upstream of the first channel 12 , that is, the suspension first flows into the second channel 21 and then flows into the first channel 12 .

[0081] The third subchannel 121 is connected between the second channel 21 and the fourth subchannel 122, that is, the second channel 21, the third subchannel 121, and the fourth subchannel 122 are connected in sequence, and the fourth subchannel 122 has an end close to the third subchannel 121 and an end far away from the third subchannel 121. From the direction close to the third subchannel 121 to the direction far away from the third subchannel 121, the flow area of ​​the fourth subchannel 122 gradually increases. In other words, the shape of the fourth subchannel 122 is constructed to be similar to an inverted funnel.

[0082] As an example, the first subchannel 211, the second subchannel 212, the third subchannel 121, and the fourth subchannel 122 are connected in sequence, and the suspension can flow through the first subchannel 211, the second subchannel 212, the third subchannel 121, and the fourth subchannel 122 in sequence and flow out of the filtering device.

[0083] By gradually increasing the flow area of ​​the fourth subchannel 122 from the direction close to the third subchannel 121 to the direction away from the third subchannel 121, the flow area of ​​the suspension when flowing out of the filter device can be increased, so that the suspension can be discharged quickly, thereby reducing the risk of the suspension accumulating in the first channel 12, which is conducive to the suspension flowing more smoothly from the second subchannel 212 through the filter element and into the third subchannel 121, thereby improving the filtering performance of the filtering device.

[0084] In some embodiments, the diameter of the outlet of the second subchannel 212 is D1, and the diameter of the inlet of the first channel 12 is D2, satisfying the relationship: 1<D2 / D1<1.5.

[0085] That is to say, the ratio of the diameter at the inlet of the first channel 12 to the diameter at the outlet of the second sub-channel 212 satisfies the relationship: 1<D2 / D1<1.5, which can also be understood as that the diameter D1 at the outlet of the second sub-channel 212 and the diameter D2 at the inlet of the first channel 12 satisfy the relationship: D1<D2<1.5D1, that is, the diameter D2 at the inlet of the first channel 12 is larger than the diameter D1 at the outlet of the second sub-channel 212, and the diameter D2 at the inlet of the first channel 12 is smaller than 1.5 times the diameter D1 at the outlet of the second sub-channel 212.

[0086] Specifically, the ratio of the diameter at the inlet of the first channel 12 to the diameter at the outlet of the second sub-channel 212 can be any value between 1 and 1.5. For example, the ratio of the diameter at the inlet of the first channel 12 to the diameter at the outlet of the second sub-channel 212 can be but not limited to 1.1, 1.2, 1.3, etc. As an example, the ratio of the diameter at the inlet of the first channel 12 to the diameter at the outlet of the second sub-channel 212 is 1.2.

[0087] It should be explained that if D2 is less than D1, the impact force of the suspension in the second subchannel 212 is too large, and the risk of the filter being destroyed is relatively high. If D2 is greater than 1.5D1, the flow rate of the suspension in the second subchannel 212 is too low, which seriously affects the filtration efficiency of the filter device. By making the ratio of the diameter at the inlet of the first channel 12 to the diameter at the outlet of the second subchannel 212 any value between 1 and 1.5, the size design of the diameter at the inlet of the first channel 12 and the diameter at the outlet of the second subchannel 212 can be reasonable, which can take into account both improving the filtration efficiency and reducing the risk of the filter being destroyed, which is conducive to improving the reliability of the filter device.

[0088] In some embodiments, the included angle between the generatrix of the side wall of the second subchannel 212 and the center line of the filter device is α, which satisfies the relationship: 3 degrees ≤ α ≤ 25 degrees.

[0089] Among them, the angle α between the busbar of the side wall of the second sub-channel 212 and the center line of the filter device satisfies the relationship: 3 degrees ≤ α ≤ 25 degrees, that is, the angle α between the busbar of the side wall of the second sub-channel 212 and the center line of the filter device can be any value between 3 degrees and 25 degrees. For example, the angle α between the busbar of the side wall of the second sub-channel 212 and the center line of the filter device can be but is not limited to 3 degrees, 14 degrees, 25 degrees, etc. As an example, the angle α between the busbar of the side wall of the second sub-channel 212 and the center line of the filter device is 10 degrees.

[0090] It should be explained that if α is too small, the impact force of the suspension in the second subchannel 212 will be too large, increasing the risk of the filter being destroyed. If α is too large, the potential energy of the suspension in the second subchannel 212 will be too low, which is not conducive to the suspension passing through the filter and affects the filtration efficiency of the filter. By making the angle α between the busbar of the side wall of the second subchannel 212 and the center line of the filter any value between 3 degrees and 25 degrees, the size of the angle between the busbar of the side wall of the second subchannel 212 and the center line of the filter can be set reasonably, taking into account both improving filtration efficiency and reliability.

[0091] In some embodiments, the included angle between the generatrix of the side wall of the fourth subchannel 122 and the center line of the filter device is β, satisfying the relationship: 15 degrees ≤ β ≤ 75 degrees.

[0092] Among them, the angle β between the busbar of the side wall of the fourth sub-channel 122 and the center line of the filter device satisfies the relationship: 15 degrees ≤ β ≤ 75 degrees, that is, the angle β between the busbar of the side wall of the fourth sub-channel 122 and the center line of the filter device can be any value between 15 degrees and 75 degrees. For example, the angle β between the busbar of the side wall of the fourth sub-channel 122 and the center line of the filter device can be but not limited to 15 degrees, 45 degrees, 75 degrees, etc. As an example, the angle β between the busbar of the side wall of the fourth sub-channel 122 and the center line of the filter device is 45 degrees.

[0093] It should be explained that if β is too small, the suspension is at risk of gathering in the first channel 12, which is not conducive to the smooth flow of the suspension through the filter element and affects the filtering performance of the filter device. If β is too large, the suspension flowing out of the filter device is easy to splash and is not easy to collect. By making the angle β between the generatrix of the side wall of the fourth subchannel 122 and the center line of the filter device any value between 15 degrees and 75 degrees, the size of the angle between the generatrix of the side wall of the fourth subchannel 122 and the center line of the filter device can be set reasonably, which can improve the filtering performance of the filter device and facilitate the collection of the suspension flowing out of the filter device.

[0094] In some embodiments, Figure 4 and Figure 5 As shown, the second shell 20 includes: a connecting portion 22 and a shell body 23, the connecting portion 22 is connected to the shell body 23 and is located on the side of the shell body 23 away from the first shell 10, the cross-sectional area of ​​the connecting portion 22 is smaller than the cross-sectional area of ​​the shell body 23, and the connecting portion 22 and the shell body 23 jointly define a second channel 21.

[0095] The connection part 22 is connected to the shell body 23, and the connection method of the connection part 22 and the shell body 23 can be but not limited to welding, bolt connection, etc. As an example, the connection part 22 and the shell body 23 are connected by welding. As an example, the connection part 22 and the shell body 23 are integrally formed.

[0096] The connecting portion 22 is located on the side of the shell body 23 away from the first shell 10, that is, along the axial direction of the filter device (i.e. Figure 2 The shell body 23 has a side close to the first shell 10 and a side away from the first shell 10, and the connecting portion 22 is located on the side of the shell body 23 away from the first shell 10, and the cross-sectional area of ​​the connecting portion 22 is smaller than the cross-sectional area of ​​the shell body 23, that is, the diameter of the connecting portion 22 is smaller than the diameter of the shell body 23. The connecting portion 22 and the shell body 23 together define the second channel 21. As an example, the connecting portion 22 defines part of the first sub-channel 211, and as an example, the connecting portion 22 defines the entire first sub-channel 211.

[0097] By making the second shell 20 include a connecting portion 22 and a shell body 23, and making the cross-sectional area of ​​the connecting portion 22 smaller than the cross-sectional area of ​​the shell body 23, the connecting portion 22 can be easily connected to the connecting pipe described below, which can reduce the difficulty of assembling the filter device with other components, and is conducive to improving the adaptability of the filter device and the assembly efficiency with other components.

[0098] In some embodiments, Figure 4 and Figure 5 As shown, the shell body 23 includes: a first sub-shell 231 and a second sub-shell 232, the first sub-shell 231 is connected between the second sub-shell 232 and the connecting portion 22, at least a portion of the second sub-shell 232 can be accommodated in the receiving groove 11, and the second sub-shell 232 is threadedly matched with the inner wall of the receiving groove 11.

[0099] The first sub-shell 231 is connected between the second sub-shell 232 and the connecting portion 22. Specifically, along the axial direction of the filter device (i.e. Figure 2 The first sub-housing 231 is connected between the second sub-housing 232 and the connecting portion 22, so that the connecting portion 22, the first sub-housing 231, and the second sub-housing 232 are arranged in sequence. As an example, the connecting portion 22, the first sub-housing 231, and the second sub-housing 232 are integrally formed.

[0100] As an example, part of the second sub-shell 232 can be received in the receiving groove 11 , and as an example, the entire second sub-shell 232 can be received in the receiving groove 11 . In addition, the second sub-shell 232 is threadedly matched with the inner wall of the receiving groove 11 .

[0101] By making at least a portion of the second sub-shell 232 receivable in the receiving groove 11, the second sub-shell 232 can be guided to cooperate with the first shell 10, thereby reducing the difficulty of cooperation between the first shell 10 and the second shell 20; by making the second sub-shell 232 cooperate with the inner wall thread of the receiving groove 11, the first shell 10 and the second shell 20 can be detachably connected, thereby reducing the difficulty of disassembly and assembly of the first shell 10 and the second shell 20, and the first shell 10 and the second shell 20 can be firmly cooperated; in addition, it can also play a certain sealing role, thereby reducing the risk of the suspension flowing out of the gap between the inner wall of the receiving groove 11 and the second sub-shell 23.

[0102] In some embodiments, Figure 2-Figure 5 As shown, the second sub-shell 232 includes a first matching portion 2321 and a second matching portion 2322, the first matching portion 2321 is connected between the second matching portion 2322 and the first sub-shell 231, the cross-sectional area of ​​the first matching portion 2321 is greater than the cross-sectional area of ​​the second matching portion 2322 and has an external thread 23211, the accommodating groove 11 includes a first sub-groove 111 and a second sub-groove 112, the first sub-groove 111 has an internal thread 1111 that can match with the external thread 23211 and the size is adapted to the first matching portion 2321, the size of the second sub-groove 112 is adapted to the second matching portion 2322; the end face of the first matching portion 2321 can abut against the end face of the first sub-groove 111.

[0103] The first matching portion 2321 is connected between the second matching portion 2322 and the first sub-shell 231. Specifically, along the axial direction of the filter device (ie Figure 2 The first mating portion 2321 is connected between the second mating portion 2322 and the first sub-shell 231, so that the first sub-shell 231, the first mating portion 2321, and the second mating portion 2322 are arranged in sequence, the cross-sectional area of ​​the first mating portion 2321 is greater than the cross-sectional area of ​​the second mating portion 2322, and the first mating portion 2321 has an external thread 23211.

[0104] The receiving groove 11 includes a first sub-groove 111 and a second sub-groove 112, which are arranged along the axial direction of the filter device (i.e. Figure 2In the Z direction shown in the figure, the first sub-groove 111 is farther away from the first channel 12 than the second sub-groove 112, and the first sub-groove 111 has an internal thread 1111 that can cooperate with the external thread 23211 of the first matching portion 2321, and the size of the first sub-groove 111 is adapted to the first matching portion 2321, so that the first matching portion 2321 can be threadedly matched with the first sub-groove 111. The size of the second sub-groove 112 is adapted to the second matching portion 2322, so that the sealing performance of the second sub-groove 112 and the second matching portion 2322 is better. It should be explained that the cross-sectional area of ​​the first sub-groove 111 is larger than the cross-sectional area of ​​the second sub-groove 112, and the end face of the first matching portion 2321 can abut against the end face of the first sub-groove 111 to prompt that it is installed in place.

[0105] By making the cross-sectional area of ​​the first matching portion 2321 larger than the cross-sectional area of ​​the second matching portion 2322 and having the external thread 23211, both the second matching portion 2322 and the first matching portion 2321 can be assembled to the receiving groove 11, and the first shell 10 and the second shell 20 can be tightly matched through the thread, which can improve the connection strength between the first shell 10 and the second shell 20. By making the end face of the first matching portion 2321 abut against the end face of the first sub-groove 111, when the end face of the first matching portion 2321 abuts against the end face of the first sub-groove 111, it means that the first shell 10 and the second shell 20 are assembled in place, so that the first shell 10 and the second shell 20 have a fool-proof effect during installation, which can reduce the risk of loose installation and the risk of suspension leakage caused by the first shell 10 and the second shell 20 not being tightened, which is conducive to improving the reliability and convenience of use of the filtering device.

[0106] In some embodiments, the filtering device also includes: a seal, the inner wall of the second sub-groove 112 has a sealing groove, part of the seal is accommodated in the sealing groove and is clamped between the inner wall of the second sub-groove 112 and the second matching portion 2322, that is, part of the seal is accommodated in the sealing groove, and the seal is clamped between the inner wall of the second sub-groove 112 and the second matching portion 2322. Such a setting can improve the sealing performance of the receiving groove 11, reduce the risk of the suspension flowing out of the gap between the inner wall of the receiving groove 11 and the second sub-shell 23, and can make the seal installed firmly, reducing the risk of the seal moving or even falling off.

[0107] In some embodiments, Figure 2 and Figure 4As shown, the end of the partial structure of the second shell 20 accommodated in the receiving groove 11 is chamfered. As an example, the end edge of the second matching portion 2322 away from the first matching portion 2321 is rounded. As an example, the end edge of the second matching portion 2322 away from the first matching portion 2321 is chamfered. The angle of the chamfer can be but not limited to 30 degrees, 45 degrees, 60 degrees, etc. For example, the angle of the chamfer of the end edge of the second matching portion 2322 away from the first matching portion 2321 is 45 degrees. This arrangement can eliminate burrs at the end of the partial structure of the second shell 20 accommodated in the receiving groove 11, and will not cause the end of the partial structure of the second shell 20 accommodated in the receiving groove 11 to have sharp edges, which can reduce the risk of the second shell 20 scratching the filter element during assembly.

[0108] In some embodiments, Figure 2 and Figure 4 As shown, the outer peripheral wall of the first shell 10 and the outer peripheral wall of the second shell 20 both have an anti-slip portion 24. As an example, the anti-slip portion 24 is configured as an anti-slip protrusion. As an example, the anti-slip portion 24 is configured as an anti-slip groove.

[0109] As an example, the outer peripheral wall of the first shell 10 has a plurality of anti-skid portions 24, and the plurality of anti-skid portions 24 of the outer peripheral wall of the first shell 10 are arranged circumferentially. As an example, the outer peripheral wall of the second shell 20 has a plurality of anti-skid portions 24, and the plurality of anti-skid portions 24 of the outer peripheral wall of the second shell 20 are arranged circumferentially. Such an arrangement can increase the surface roughness of the outer peripheral wall of the first shell 10 and the outer peripheral wall of the second shell 20, facilitate screwing the first shell 10 and the second shell 20, reduce the difficulty of disassembling and assembling the filter device, and reduce the probability of the filter device slipping from the hand.

[0110] In the second aspect of the present application, the present application proposes an analysis device, which adopts the above-mentioned analysis method. Therefore, the analysis device has all the characteristics and advantages of the above-mentioned analysis method, which will not be described in detail here.

[0111] In some embodiments, the analysis device may include a filtering device, a driving member, a connecting pipe, a liquid storage container, and a receiving container. The filtering device is the above-mentioned filtering device, the filtering device is connected to the liquid storage container through a connecting pipe, the driving member is used to transport the suspension in the liquid storage container to the filtering device, and the receiving container is used to receive the suspension flowing out of the filtering device.

[0112] As an example, the driving member is an impeller pump, and the connecting pipe may include a first sub-pipe and a second sub-pipe, the first sub-pipe is connected between the driving member and the filtering device, and the second sub-pipe is connected between the driving member and the liquid storage container, and the driving member is used to transport the suspension in the liquid storage container to the filtering device.

[0113] As an example, the driving member is a peristaltic pump, the connecting pipe is connected between the filtering device and the liquid storage container, and the connecting pipe passes through the driving member to transport the suspension in the liquid storage container to the filtering device through the driving member.

[0114] As an example, in the process of using the analysis device, the filter element is first placed in the receiving groove 11, and then the first shell 10 and the second shell 20 are assembled, and the connecting pipe is connected to the connecting part 22, and then the connecting pipe is passed through the driving member and connected to the liquid storage container, and finally the receiving container is connected to the first channel 12 of the first shell 10, and the filtering operation can be performed. Among them, the receiving container can be directly assembled with the first shell 10, or the receiving container can be placed under the first shell 10 to receive the suspension flowing out of the first channel 12.

[0115] Such an arrangement can make the analysis device reliable to use and easy to assemble and disassemble. Moreover, by making the second shell 20 detachably connected to the first shell 10, the filter device can be conveniently assembled and disassembled. By making a partial structure of the second shell 20 able to be accommodated in the accommodating groove 11 and the filter element clamped between the bottom wall of the accommodating groove 11 and the second shell 20, the filter element can be firmly fixed, reducing the risk of displacement and wrinkling of the filter element during use, which is beneficial to improving the filtering performance of the filtering device, thereby facilitating the separation and filtering operation of impurities.

[0116] The scheme of the present application is described below by specific examples. It should be noted that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are specified in the examples, the technology or conditions described in the literature in this area or the product instructions are used. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be obtained commercially.

[0117] Example 1

[0118] (1) Weigh 100 g of the positive electrode active material sample and put it into a 1000 mL beaker. Add a stirring bar to the beaker, add 1 L of ultrapure water, place it on a stirrer, and stir at a speed of 600 rpm to obtain a suspension with a solid content of 10%.

[0119] (2) D of positive electrode active material 50 5μm, D 100 The pore size of the filter membrane is 13 μm, and the pore size of the filter membrane is 38 μm. The silicone tubes are installed at both ends of the peristaltic pump and connected to the filter device and the beaker cover respectively. The flow rate of the peristaltic pump is 600 mL / min. The suspension is transported from the beaker to the filter device along the silicone tube. K is 2.1×10 -2 . It is calculated that the flow rate of the suspension is 0.96L / min.

[0120] (3) When the volume of the suspension is reduced to less than 300 mL, add 1 L of ultrapure water and 100 g of the positive electrode active material sample again for suspension aspiration, and repeat this process 5 times. After the suspension aspiration is completed, connect the silicone tube to the glass funnel, use a wash bottle to collect the residual positive electrode active material particles on the funnel, and then rinse the funnel with a wash bottle until no positive electrode active material sample is visible to the naked eye. Turn off the peristaltic pump, and connect the silicone tube connected to the filter device to the faucet, and keep the water flowing in a straight line for 60 seconds. Then remove the filter device, take out the filter membrane, and fix it on the storage table.

[0121] (4) Place the storage table on the positioning film and use an X-ray fluorescence analyzer to test and analyze foreign matter.

[0122] Test results: Figure 6 It is a blocky particle with a size of 0.073 mm and contains 60wt% Fe.

[0123] Example 2

[0124] Example 2 is the same as Example 1, except that R = 25.67 μm + 1.1D 100 , R = 39.97 μm was calculated, and a standard filter membrane with an approximate pore size of 40 μm was used. The flow rate of the suspension was calculated to be 1.008 L / min.

[0125] X-ray fluorescence analyzer was used to test and analyze foreign matter. The test results are as follows: Figure 7 It is a mesh block particle with a size of 0.081 mm, containing 30wt% Fe and 6wt% Cr.

[0126] Comparative Example 1

[0127] Comparative Example 1 is the same as Example 1, except that the flow rate of the suspension is 2 L / min.

[0128] like Figure 8 As shown, there are too many retained materials, the material blocks the filter membrane, and the X-ray fluorescence analyzer cannot be used to test and analyze the foreign matter.

[0129] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for analyzing foreign matter in a positive electrode active material, characterized in that: include: dispersing the positive electrode active material in a solvent to form a suspension; The suspension is transported to a filter device by a driving member to obtain a retentate, wherein the flow rate of the suspension is Lr, in units of L / min, and the filter device includes a filter element; Analyzing the intercepted material to obtain information on the size and element type of the foreign matter; The Lr satisfies: Lr = (K × J × R) / (D 50 ×S), where K is 1×10 -2 -3×10 -2 , J is the pump speed of the driving element, in rpm; R is the pore size of the filter element, in μm; D 50 is the particle size corresponding to when the cumulative particle size distribution percentage of the positive electrode active material reaches 50%, in μm; S is the solid content of the suspension, in %.

2. The analysis method according to claim 1, characterized in that Lr is 0.5L / min-1.5L / min.

3. The analysis method according to claim 1, characterized in that R is greater than D 100 , D 100 It is the particle size corresponding to when the cumulative particle size distribution percentage of the positive electrode active material reaches 100%, in μm.

4. The analysis method according to claim 3, characterized in that R=25.67μm+1.1D 100 。 5. The analysis method according to claim 3 or 4, characterized in that D 100 15μm-30μm.

6. The analysis method according to any one of claims 1 to 4, characterized in that J is 0.2L / min-0.6L / min.

7. The method according to claim 6, characterized in that D 50 is 3μm-10μm; and / or, S is 5%-15%.

8. The method according to any one of claims 1 to 4, characterized in that: After obtaining the retentate, the method further comprises: using a driving member to transport the solvent to the filtering device.

9. The analysis method according to any one of claims 1 to 4, characterized in that: The analysis of the intercepted material comprises at least one of X-ray fluorescence spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, and transmission electron microscopy-energy dispersive X-ray spectroscopy.

10. An analysis device, characterized in that: The analytical method according to any one of claims 1 to 9 is used.

Images