Method for determining dispersibility of a slurry-making material

Abstract

The present application belongs to the technical field of battery, and particularly relates to a method for judging dispersibility of slurry mixing material, comprising the following steps: S21. Taking a sample with a certain length from a positive electrode diaphragm and / or a negative electrode diaphragm which has not been rolled, and recording as a non-rolled sample; S22. Rolling the diaphragm from which the sample is taken in step S21 according to a certain compaction density; S23. Taking a diaphragm sample with the same length as the non-rolled sample from the diaphragm after rolling in step S22 on one side of the position where the sample is taken in step S21, and recording as a rolled sample; S24. Selecting N detection points from the non-rolled sample and the rolled sample, and N is greater than or equal to 3; S25. Testing the diaphragm resistance of the detection points obtained in step S24, and recording the resistance value; S26. Judging the dispersibility of the conductive agent and the binder in the slurry mixing material according to the resistance value. The method of the present application can quickly judge the conductive agent in the prepared positive electrode diaphragm and negative electrode diaphragm, and truly reflect the dispersion state of the binder and the conductive agent in the slurry.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a method for judging the dispersibility of slurry mixing material of a lithium battery. BACKGROUND

[0002] An important preparation process of a lithium battery includes steps such as slurry mixing, coating and rolling. Among them, the slurry mixing is to mix active materials, binders, conductive agents and the like to prepare a uniform slurry. In the slurry mixing step, the distribution of the conductive agent and the binder greatly affects the conductivity of the pole piece. The uniform distribution of the conductive agent can make the conductivity of the pole piece better. After the pole piece is assembled into a battery, the internal resistance of the battery is relatively small, and the electrochemical polarization is relatively small. The uneven dispersion of the conductive agent causes the local conductive agent content of the pole piece to be relatively high. Such a battery will increase the risk of lithium precipitation during the charging and discharging process. The internal resistance of the area without conductive agent will become larger, and the internal resistance of the area with more conductive agent will become smaller, which will cause the polarization of the battery to become larger, and the heat generation of the battery will increase. The role of the binder is to bond the active material and the conductive agent. The binder is a non-conductive high polymer. The uneven dispersion of the binder will cause the internal resistance of the pole piece to become larger, thereby increasing the internal resistance of the battery and causing a large polarization.

[0003] At present, the existing technologies about the detection of the material dispersibility in the battery slurry are as follows.

[0004] CN112067664A discloses a method for evaluating the material dispersibility in a lithium ion battery pole piece. After the slurry is coated on the surface of the foil and baked, the baking process of the lithium ion battery pole piece is simulated. The dispersion state of each component in the powder on the pole piece after drying is similar to the actual situation. The powder abrasion rate of the sample A slurry coating side and the powder abrasion rate of the sample B foil after being separated are tested, and then the distribution of the binder in the powder at different positions on the pole piece is judged. A friction and wear testing machine is also used to characterize the adhesion between the pole piece powder and the powder. The operation and equipment are simple, the testing is fast, the data is quantifiable, and the safety risk is extremely low. In addition, after the pole piece powder is peeled off by a peeling device, the powder abrasion rate close to the current collector side is tested and compared with the powder abrasion rate on the surface of the pole piece, so as to evaluate the dispersion of the binder in the powder at different positions of the pole piece. The method is simple, and the result is intuitive and reliable.

[0005] The above method evaluates the dispersion of the binder by the powder abrasion rate. However, in fact, the factors affecting the powder abrasion rate are not single factors of the binder. The evaluation is not real, and the dispersion of the conductive agent cannot be evaluated at the same time.

[0006] CN108519407A discloses a method for evaluating the dispersion of conductive paste of lithium ion battery, which comprises the following steps: uniformly coating a first solid content of polymer emulsion on an insulating film, drying to form a modified insulating film containing a second solid content of polymer emulsion layer; preparing a conductive paste with a certain proportion, coating the conductive paste on the modified insulating film to prepare a test sample; fully baking the test sample, measuring the thickness of the conductive paste layer of the test sample; setting the correction coefficient of the four-probe instrument according to the thickness of the conductive paste layer, repeatedly measuring the resistivity of different regions of the test sample, and evaluating the dispersion of the conductive paste. The method overcomes the influence of the conductive property of the coated substrate on the measurement results, and can simply, conveniently, accurately and intuitively evaluate the dispersion of the conductive paste of lithium ion battery.

[0007] The above method can only test the dispersion of the conductive paste as a whole, and cannot distinguish the dispersion of different components (such as the binder and the conductive agent) in the conductive paste.

[0008] CN102207479A discloses a method for detecting the dispersion uniformity of lithium ion battery paste, which comprises the following steps: sampling the paste at different positions and detecting the conductivity of the sample, evaluating the dispersion uniformity of the paste according to the difference in the conductivity of the sample. The conductivity is the conductivity of the sample: after sampling the paste at different positions, the sample is dried and pressed into a sample sheet, the resistance R of the sample sheet is detected under the same compaction density, and then the conductivity of the sample sheet is calculated according to the formula σ=R*S / L, and the dispersion uniformity of the paste is determined according to the difference in the resistivity of the paste at different positions.

[0009] The above method detects the resistance of the sample obtained by drying and pressing the paste, and cannot truly reflect the dispersion of the paste, and cannot distinguish the dispersion of different materials in the paste. SUMMARY

[0010] In order to quickly and effectively detect the dispersion of the conductive agent and the binder in the pole piece, the present application provides a method for judging the dispersion of the mixed paste material.

[0011] The present application adopts the following technical scheme:

[0012] The first aspect of the present disclosure provides a method for judging the dispersion of the mixed paste material, which comprises the following steps:

[0013] S11. Rolling the positive electrode film piece and / or the negative electrode film piece according to a certain compaction density;

[0014] S12. Taking a sample with a certain length from the film piece in step S11, which is recorded as a rolled sample;

[0015] S13. Take N detection sites from the roller-pressed sample, N is greater than or equal to 3;

[0016] S14. Test the sheet resistance of the detection sites obtained in step S13, and record the resistance value;

[0017] S15. Determine the dispersibility of the conductive agent and the binder in the slurry material according to the resistance value.

[0018] The above scheme takes detection sites for resistance value testing after the positive electrode sheet and / or the negative electrode sheet is roller-pressed according to a certain compaction thickness. The dispersion of the slurry is determined according to the relationship between the resistance value and the average resistance value of the N detection sites.

[0019] The positive electrode sheet and / or the negative electrode sheet that is not compacted, the part of the detection sites due to the point-like dispersion of the binder, is not sufficient to cause a large difference in resistance, resulting in the inability to obtain or the real resistance difference. The compacted sheet, the binder is flattened, the area is expanded, and the resistance is increased, which can more truly reflect the dispersion of the slurry material.

[0020] In step S15, the determination method is:

[0021] The difference between the resistance value of each roller-pressed sample of the positive electrode sheet and the average resistance value is within the range of -5 to 5 mΩ, indicating that the conductive agent is uniformly dispersed. The difference between the resistance value of any roller-pressed sample of the positive electrode sheet and the average resistance value is greater than 5 mΩ, indicating that the binder is agglomerated.

[0022] The difference between the resistance value of each roller-pressed sample of the negative electrode sheet and the average resistance value is within the range of -0.05 to 0.05 mΩ, indicating that the conductive agent is uniformly dispersed. The difference between the resistance value of any roller-pressed sample of the negative electrode sheet and the average resistance value is greater than 0.1 mΩ, indicating that the binder is not well dispersed or the binder is floating.

[0023] The resistance value of the positive electrode sheet is greater than that of the negative electrode sheet. In the actual test and judgment standard process, combined with the optimized sampling method, when judging the dispersibility of the conductive agent, the standard is limited to the range of -5 to 5 mΩ, which can more accurately determine the real dispersion of the conductive agent. If it is greater than this range, the unevenly dispersed conductive agent will be misjudged as uniformly dispersed. The judgment standard for the dispersibility of the binder is that the difference between the resistance value of any roller-pressed sample and the average resistance value is greater than 5 mΩ. If the set value is greater than or less than 5 mΩ, the real dispersion effect of the binder will be misjudged.

[0024] In the actual test judgment standard process, in combination with the optimized sampling mode, when judging the dispersion of the conductive agent of the negative electrode film, the standard is limited to the range of -0.05 to 0.05 mΩ, which can more accurately determine the real dispersion of the conductive agent. If it is greater than the range, the conductive agent with uneven dispersion will be misjudged as uniformly dispersed; the judgment standard for the dispersion of the binder is that the difference between the resistance value of any rolled sample and the average resistance value is greater than 0.1 mΩ. If the set value is greater than or less than 0.1 mΩ, the real dispersion effect of the binder will be misjudged.

[0025] In an embodiment, the compaction density in step S12 is that the compaction density of the positive electrode film satisfies 2.0-3.0 g / cc, and the compaction density of the negative electrode film satisfies 1.2-2.0 g / cc.

[0026] In an embodiment, N is any natural number from 10 to 25.

[0027] The second aspect of the present disclosure provides a method for judging the dispersion of the slurry material, comprising the following steps:

[0028] S21. Taking a sample of a certain length from the unrolled positive electrode film and / or negative electrode film, denoted as an unrolled sample;

[0029] S22. Rolling the film with the sample taken in step S21 according to a certain compaction density;

[0030] S23. Taking a film sample of the same length as the unrolled sample from the side of the film of the electrode piece after rolling in step S22 at the sampling position in step S21, denoted as a rolled sample;

[0031] S24. Selecting N detection sites from the unrolled sample and the rolled sample, N is greater than or equal to 3;

[0032] S25. Testing the film resistance of the detection sites obtained in step S24, and recording the resistance value;

[0033] S26. Judging the dispersion of the conductive agent and the binder in the slurry material according to the resistance value.

[0034] The first aspect of the present disclosure tests the resistance of the film after compaction, and judges the dispersion of the conductive agent and the binder in the slurry material according to the resistance value. In the actual evaluation process, the inventors found that although the resistance value of the detection site after rolling is normal, the conductive agent and the binder are judged to be uniformly dispersed according to the judgment method, but in the subsequent quality inspection process of the lithium battery, it is shown to be unqualified. After analysis, there are still cases of uneven dispersion of the conductive agent.

[0035] Therefore, the inventor detects the samples without rolling, and finds that the difference between the resistance value of the part of the samples without rolling and the average resistance value is large, which can prove that the conductive agent is not uniformly dispersed, which matches the actual result.

[0036] The present disclosure samples the membrane before and after rolling respectively, and measures the resistance value, and evaluates the dispersion of the slurry according to the relationship between the resistance value of the membrane before and after rolling and the average resistance value. This way, the dispersion of the slurry is more truly reflected.

[0037] In step S26, the judgment method is:

[0038] If the difference between the resistance value of each unrolled sample of the positive electrode membrane and the average resistance value is within the range of -5 to 5 mΩ and / or the difference between the resistance value of each rolled sample and the average resistance value is within the range of -5 to 5 mΩ, it indicates that the conductive agent is uniformly dispersed; if the difference between the resistance value of any unrolled sample of the positive electrode membrane and the average resistance value is greater than 5 mΩ and / or the difference between the resistance value of any rolled sample and the average resistance value is greater than 5 mΩ, it indicates that the binder is agglomerated.

[0039] If the difference between the resistance value of each unrolled sample of the negative electrode membrane and the average resistance value is within the range of -0.05 to 0.05 mΩ and / or the difference between the resistance value of each rolled sample and the average resistance value is within the range of -0.05 to 0.05 mΩ, it indicates that the conductive agent is uniformly dispersed; if the difference between the resistance value of any unrolled sample of the negative electrode membrane and the average resistance value and / or the difference between the resistance value of any rolled sample and the average resistance value is greater than 0.1 mΩ, it indicates that the binder is not well dispersed or the binder is floating.

[0040] In an embodiment, the compaction thickness in step S22 is: the compaction density of the positive electrode membrane satisfies 2.0-3.0 g / cc, and the compaction density of the negative electrode membrane satisfies 1.2-2.0 g / cc.

[0041] In an embodiment, the number of unrolled samples in step S21 and rolled samples in step S23 is not less than five.

[0042] In an embodiment, N is any natural number from 10 to 25.

[0043] In an embodiment, the test method of the membrane resistance adopts a single probe method, a four-probe method or a double-plane controllable pressure disc electrode resistance method.

[0044] In an embodiment, the slurry material of the positive electrode membrane includes a positive electrode active material, a conductive agent, a binder and a solvent, and the positive electrode active material: conductive agent: binder = (60-90): (5-20): (5-20).

[0045] In an embodiment, the positive active material includes lithium iron phosphate, lithium manganese iron phosphate, ternary material (5-9 ternary material), lithium cobaltate, and other commonly used positive electrode materials in the market.

[0046] In an embodiment, the conductive agent includes at least one of acetylene black, carbon nanotube, ketjen black, and graphene.

[0047] In an embodiment, the binder includes polyvinylidene fluoride (PVDF5130, HSV900, kynar761).

[0048] In an embodiment, the solvent includes N-methyl pyrrolidone (NMP).

[0049] In an embodiment, the slurry material of the negative electrode film includes a negative active material, a conductive agent, a binder A, a binder B, and a solvent.

[0050] In an embodiment, the negative active material: conductive agent: binder A: binder B = (55-85): (5-15) (5-15): (5-15).

[0051] In an embodiment, the negative active material includes artificial graphite, mixed graphite (a mixture of two different materials in a certain proportion), and silicon-oxygen graphite negative electrode.

[0052] In an embodiment, the binder A includes sodium carboxymethyl cellulose (CMC2200, CMC2300, CMC2500, MAC500, MAC350, etc.).

[0053] In an embodiment, the binder B includes styrene butadiene rubber (SBR), polyvinyl alcohol (PVA), and polyacrylic acid resin (PAA).

[0054] In an embodiment, the solvent includes deionized water, ultrapure water, etc.

[0055] The present application has the following technical effects:

[0056] 1) The method can quickly determine the conductive agent in the prepared positive electrode film and negative electrode film, and truly reflect the dispersion state of the binder and the conductive agent in the slurry.

[0057] 2) The method is simple to operate, has high accuracy, can detect the quality of the slurry in real time with the production of the electrode film, and thus optimizes the slurry process. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 A flowchart of the method for judging the dispersion of the slurry material of the present application;

[0059] Figure 2A selection mode of detection sites in an embodiment of the present disclosure;

[0060] Figure 3 A selection diagram of detection sites in an embodiment of the present disclosure;

[0061] Figure 4 Resistance detection results of six samples in Embodiment 1 of the present disclosure;

[0062] Figure 5 Resistance detection results of five un-rolled samples in Embodiment 2 of the present disclosure;

[0063] Figure 6 Resistance detection results of five rolled samples in Embodiment 2 of the present disclosure. DETAILED DESCRIPTION

[0064] The present application will be further described in detail with reference to the accompanying drawings and specific embodiments.

[0065] It should be noted that the following embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

[0066] Positive film A: a positive active material lithium iron phosphate, a conductive agent SP, and a binder PVDF are used to prepare a positive film. First, the lithium iron phosphate, the conductive agent SP, and the binder PVDF are dry mixed according to a ratio of 75:5:20, specifically including adding the lithium iron phosphate, the conductive agent SP, and the binder PVDF into a double planetary mixer according to a weight ratio, stirring at a revolution speed of 30 rpm for 30 min, then adding NMP according to a solid content of 68%, stirring at a revolution speed of 50 rpm for 2 h, and finally adding NMP according to a solid content of 64%, stirring at a linear speed of 21 m / s and a revolution of 40 rpm for 4 h, after which the slurry is prepared by adjusting the viscosity and defoaming. Coating on an aluminum foil according to a surface density of 400 g / m 2 after drying, and winding according to a length of 100 meters.

[0067] Positive electrode sheet B: A positive electrode sheet was prepared using a positive electrode active material lithium iron phosphate, a conductive agent SP, and a binder PVDF. First, the lithium iron phosphate, the conductive agent SP, and the binder PVDF were dry-mixed at a ratio of 75:20:5, specifically including adding the lithium iron phosphate, the conductive agent SP, and the binder PVDF into a double planetary mixer at a weight ratio, stirring at a revolution speed of 30 rpm for 30 min, then adding NMP at a solid content of 68%, stirring at a revolution speed of 50 rpm for 2 h, and finally adding NMP at a solid content of 64%, stirring at a linear speed of 21 m / s and a revolution of 40 rpm for 4 h, after which the slurry was completed by adjusting the viscosity and defoaming. The slurry was coated on an aluminum foil at a surface density of 400 g / m 2 after drying, and was wound at a length of 100 m.

[0068] Negative electrode sheet A: A negative electrode sheet was prepared using a negative electrode active material artificial graphite, a conductive agent SP, a binder CMC, and a binder SBR. First, the artificial graphite, the conductive agent SP, the binder CMC, and the binder SBR were dry-mixed at a ratio of 75:15:5:5, specifically including adding the artificial graphite, the conductive agent SP, and the binder CMC into a double planetary mixer at a weight ratio, stirring at a revolution speed of 30 rpm for 30 min, then adding deionized water at a solid content of 65%, stirring at a revolution speed of 50 rpm for 3 h, and finally adding deionized water at a solid content of 60%, stirring at a linear speed of 15 m / s and a revolution of 40 rpm for 2 h, and finally adding SBR at a linear speed of 5 m / s and a revolution of 20 rpm for 30 min. The slurry was completed by adjusting the viscosity and defoaming after which. The slurry was coated on a copper foil at a surface density of 200 g / m 2 after drying, and was wound at a length of 100 m.

[0069] Negative electrode sheet B: A negative electrode sheet was prepared using a negative electrode active material artificial graphite, a conductive agent SP, a binder CMC, and a binder SBR. First, the artificial graphite, the conductive agent SP, the binder CMC, and the binder SBR were dry-mixed at a ratio of 75:5:15:5, specifically including adding the artificial graphite, the conductive agent SP, and the binder CMC into a double planetary mixer at a weight ratio, stirring at a revolution speed of 30 rpm for 30 min, then adding deionized water at a solid content of 65%, stirring at a revolution speed of 50 rpm for 3 h, and finally adding deionized water at a solid content of 60%, stirring at a linear speed of 15 m / s and a revolution of 40 rpm for 2 h, and finally adding SBR at a linear speed of 5 m / s and a revolution of 20 rpm for 30 min. The slurry was completed by adjusting the viscosity and defoaming after which. The slurry was coated on a copper foil at a surface density of 200 g / m 2 after drying, and was wound at a length of 100 m.

[0070] Example 1

[0071] This embodiment takes the positive electrode film A as the detection object, and is operated according to the flow shown in Figure 1 , first, the positive electrode film A is rolled according to the compactness of 2.5 g / cc, and a positive electrode sheet with a thickness of 172 pm is obtained, then sampling is performed every 10 meters, the sampling length is 0.1 m, and six samples are taken. The sampled positive electrode film is stamped into a small piece of 10 cm x 10 cm, and the resistance corresponding to each site (the arrangement of the detection sites is selected according to Figure 3 ) is measured by the double-plane controllable pressure disc electrode resistance method, and the corresponding resistance value is recorded. The resistance detection results of the six samples are shown in Figure 4 .

[0072] Data analysis:

[0073] The average value of all sampling points is 129.99 mΩ, the difference between the largest value 147 mΩ and the average value is 17.01 mΩ, and the difference between 124 mΩ and the average value is -5.99 mΩ, which indicates that the conductive agent is not uniformly dispersed; moreover, the difference between 147 mΩ and the average value is 17.01 mΩ, which is greater than 5 mΩ, indicating that the binder is not uniformly dispersed and agglomeration occurs.

[0074] It is finally determined that the binder of the slurry material of the positive electrode film A is not uniformly dispersed, and the conductive agent is also not uniformly dispersed.

[0075] Example 2

[0076] This embodiment takes the positive electrode film A as the detection object. It is operated according to Figure 2 , first, sampling is performed every 10 meters, the sampling length is 0.1 m, and five unrolled samples are taken, then the remaining samples are rolled according to the compactness of 2.5 g / cc, then the same side sampling is performed at the sampling points before rolling, the sampling length is 0.1 m, and five rolled samples are taken. The unrolled samples and the rolled samples are stamped into small pieces of 10 cm x 10 cm according to Figure 3 , the resistance corresponding to each site is measured by the double-plane controllable pressure disc electrode resistance method, and the corresponding resistance value is recorded. The resistance detection results of the five unrolled samples are shown in Figure 5 , and the resistance detection results of the five rolled samples are shown in Figure 6 .

[0077] Data analysis:

[0078] Unrolled samples: the average value of all sampling points is 104.32 mΩ, the difference between the maximum value 112 mΩ and the average value is 7.68 mΩ, which indicates that the conductive agent is not uniformly dispersed; the difference between 112 mΩ and the average value is greater than 5 mΩ, indicating that the binder agglomerates and is not uniformly dispersed.

[0079] Rolling sample: the average value of all sampling points was 122.2 mΩ, and the difference between each resistance value and the average value was between -5 and 5 mΩ, indicating that the conductive agent was uniformly dispersed; and the difference between each resistance value and the average value was not greater than 5 mΩ, indicating that the binder was uniformly dispersed.

[0080] In this embodiment, the positive electrode film A was detected, and five samples were taken for each of the unrolled and rolled samples, wherein the rolled samples showed that the binder was uniformly dispersed, and the conductive agent was also uniformly dispersed.

[0081] The unrolled sample showed that the binder was not uniformly dispersed, and the conductive agent was also not uniformly dispersed.

[0082] Finally, it was determined that the binder of the positive electrode film A slurry material in this embodiment was not uniformly dispersed, and the conductive agent was also not uniformly dispersed.

[0083] Example 3

[0084] In this embodiment, the positive electrode film A was detected. According to the operation shown in Figure 2 , first, sampling was performed every 10 meters, with a sampling length of 0.2 m, and five unrolled samples were taken. Then, the remaining samples were rolled according to a compaction density of 3.0 g / cc, and then sampling was performed on the same side at the sampling points, with a sampling length of 0.2 m, and five rolled samples were taken. The unrolled samples and the rolled samples were punched into 10 cm x 10 cm pieces in the manner shown in Figure 3 , and the resistance of each site was measured by the double-plane controllable pressure disc electrode resistance method, and the corresponding resistance value was recorded.

[0085] Data analysis:

[0086] Unrolled sample: the average value of all sampling points was 105.05 mΩ, and the difference between each resistance value and the average value was between -5 and 5 mΩ, indicating that the conductive agent was uniformly dispersed; and the difference between each resistance value and the average value was not greater than 5 mΩ, indicating that the binder was uniformly dispersed.

[0087] Rolling sample: the average value of all sampling points was 124.35 mΩ, and the difference between each resistance value and the average value was between -5 and 5 mΩ, indicating that the conductive agent was uniformly dispersed; and the difference between each resistance value and the average value was not greater than 5 mΩ, indicating that the binder was uniformly dispersed.

[0088] In this embodiment, the positive electrode film A was detected, and five samples were taken for each of the unrolled and rolled samples, wherein the rolled samples showed that the binder was uniformly dispersed, and the conductive agent was also uniformly dispersed. The unrolled samples showed that the binder was uniformly dispersed, and the conductive agent was also uniformly dispersed.

[0089] Finally, it was determined that the binder of the positive electrode film A slurry material in this embodiment was uniformly dispersed, and the conductive agent was also uniformly dispersed.

[0090] Example 4

[0091] In this example, the positive electrode film B was detected. According to the procedure shown in Figure 2 , first, sampling was performed every 10 meters with a sampling length of 0.1 m, and then the remaining sample was rolled at a compaction density of 2.5 g / cc to obtain a positive electrode film with a thickness of 172 pm, and then the same side sampling was performed at the sampling points without rolling with a sampling length of 0.1 m. The unrolled positive electrode film and the rolled positive electrode film were punched into small pieces of 10 cm x 10 cm in the manner shown in Figure 3 , and the resistance of each point was measured by the double-plane controllable pressure disc electrode resistance method, and the corresponding resistance value was recorded.

[0092] Data analysis:

[0093] Unrolled sample: the average value of all sampling points was 112.35 mQ, and the difference between each resistance value and the average value was between -5 and 5 mQ, indicating that the conductive agent was uniformly dispersed; the difference between each resistance value and the average value was not greater than 5 mQ, indicating that the binder was uniformly dispersed.

[0094] Rolled sample: the average value of all sampling points was 133.65 mQ, and the difference between each resistance value and the average value was between -5 and 5 mQ, indicating that the conductive agent was uniformly dispersed; the difference between each resistance value and the average value was not greater than 5 mQ, indicating that the binder was uniformly dispersed.

[0095] In this example, the positive electrode film B was detected, and five samples were taken for each of the unrolled and rolled samples, among which the rolled sample showed that the conductive agent was uniformly dispersed and the binder was also uniformly dispersed. The unrolled sample showed that the conductive agent was uniformly dispersed and the binder was also uniformly dispersed.

[0096] It was finally determined that the binder of the positive electrode film B slurry material in this example was uniformly dispersed, and the conductive agent was also uniformly dispersed.

[0097] Example 5

[0098] In this example, the negative electrode film A was detected. According to the procedure shown in Figure 2 , first, sampling was performed every 10 meters with a sampling length of 0.1 m, and then the remaining sample was rolled at a compaction density of 1.5 g / cc to obtain a negative electrode film with a thickness of 139 pm, and then the same side sampling was performed at the sampling points without rolling with a sampling length of 0.1 m. The unrolled sample and the rolled sample were punched into small pieces of 10 cm 2 x 10 cm, and the resistance of each point was measured by the double-plane controllable pressure disc electrode resistance method, and the corresponding resistance value was recorded.

[0099] Data analysis:

[0100] Unrolled sample: The average value of all points is 1.74925mΩ. The difference between the maximum value of 1.85mΩ and the average value is 0.1007mΩ, which is determined to be uneven dispersion of conductive agent. The difference between 1.85mΩ and the average value is greater than 0.1mΩ, indicating that the binder is unevenly dispersed.

[0101] Roller-pressed samples: The average value of all sampling points is 2.035 mΩ. The difference between the maximum value of 2.22 mΩ and the average value is 0.185 mΩ, indicating that the conductive agent is not evenly dispersed. The difference between 2.22 mΩ and the average value is greater than 0.1 mΩ, indicating that the binder is not evenly dispersed.

[0102] Ultimately, it was determined that the binder in the negative electrode film A slurry material of this embodiment was not evenly dispersed, and the conductive agent was also not evenly dispersed.

[0103] Example 6

[0104] This embodiment uses negative electrode membrane B as the detection object. Figure 2 The procedure is as follows: First, samples are taken every 10 meters, with a sampling length of 0.1m, and these are recorded as unrolled samples; six samples are taken. Then, the remaining samples are rolled at a compaction density of 1.5 g / cc to obtain a negative electrode film with a thickness of 139µm. Samples are taken from the same side at the sampling points used in the unrolled samples, with a sampling length of 0.1m, and these are recorded as rolled samples; six samples are taken. The unrolled and rolled samples are then stamped into 10cm pieces. 2 The resistance of each point on the small piece was measured using the dual-plane controllable pressure disk electrode resistance method, and the corresponding resistance value was recorded.

[0105] Data Analysis:

[0106] Unrolled sample: The average value of all points is 1.125 mΩ. The difference between each resistance value and the average value is between -0.05 and 0.05 mΩ, indicating that the conductive agent is uniformly dispersed. The difference between each resistance value and the average value is no greater than 0.1 mΩ, indicating that the binder is uniformly dispersed.

[0107] Roller-pressed samples: The average value of all sampling points was 1.4735 mΩ. The difference between the maximum value of 1.73 mΩ and the average value was 0.2565 mΩ, indicating that the conductive agent was not evenly dispersed. The difference between 1.73 mΩ and the average value was 0.2565 mΩ, indicating that the binder was not evenly dispersed.

[0108] Ultimately, it was determined that the binder and conductive agent in the negative electrode film B slurry material of this embodiment were not evenly dispersed.

[0109] Example 7

[0110] This embodiment uses negative electrode membrane B as the detection object.Figure 2 The shown flow is operated as follows: first, sample every 10 meters, sample length is 0.1 m, recorded as unrolled sample, sample six. Then roll the remaining sample according to the compaction density of 1.5 g / cc, get the negative electrode film with thickness of 139 µm, sample the same side at the sampling point when unrolled, sample length is 0.1 m, recorded as rolled sample, sample six. Punch the unrolled sample and rolled sample into 10 cm 2 small pieces, measure the resistance of each point corresponding to the resistance by double plane controllable pressure disc electrode resistance method and record the corresponding resistance value.

[0111] Data analysis:

[0112] Unrolled sample: the average value of all sampling points is 1.0645 mΩ, the maximum value 1.23 mΩ is 0.1655 mΩ away from the average value, which indicates that the conductive agent is not uniformly dispersed; 1.23 mΩ is more than 0.1 mΩ away from the average value, which indicates that the binder is not uniformly dispersed.

[0113] Rolled sample: the average value of all sampling points is 1.415 mΩ, the difference between each resistance value and the average value is between -0.05 and 0.05 mΩ, which indicates that the conductive agent is uniformly dispersed; the difference between each resistance value and the average value is not more than 0.1 mΩ, which indicates that the binder is uniformly dispersed.

[0114] Finally, it is determined that the negative electrode film B of the slurry material of this embodiment is not uniformly dispersed in the binder, and the conductive agent is also not uniformly dispersed.

Claims

1. A method of determining the dispersibility of a cementitious material, characterized by, The method comprises the following steps: S11. rolling the positive electrode film and / or the negative electrode film according to a certain compaction density, wherein the compaction density of the positive electrode film satisfies 2.0-3.0 g / cc, and the compaction density of the negative electrode film satisfies 1.2-2.0 g / cc; S12. taking a sample of a certain length from the film in step S11, and recording the sample as a rolled sample; S13. taking N detection sites from the rolled sample, wherein N is greater than or equal to 3; S14. testing the film resistance of the detection sites obtained in step S13, and recording the resistance value; S15. judging the dispersity of the conductive agent and the binder in the slurry according to the resistance value; In step S15, the judging method is as follows: if the difference between the resistance value of each rolled sample of the positive electrode film and the average resistance value is within the range of -5 to 5 mΩ, it is indicated that the conductive agent is uniformly dispersed, and if the difference between the resistance value of any rolled sample of the positive electrode film and the average resistance value is greater than 5 mΩ, it is indicated that the binder is agglomerated; if the difference between the resistance value of each rolled sample of the negative electrode film and the average resistance value is within the range of -0.05 to 0.05 mΩ, it is indicated that the conductive agent is uniformly dispersed, and if the difference between the resistance value of any rolled sample of the negative electrode film and the average resistance value is greater than 0.1 mΩ, it is indicated that the binder is not well dispersed or the binder is floated.

2. The method of determining the dispersibility of a cementitious material according to claim 1, wherein, N is any natural number within the range of 10 to 25.

3. A method of determining the dispersibility of a cementitious material, characterized by, The method comprises the following steps: S21. taking a sample of a certain length from the unrolled positive electrode film and / or the unrolled negative electrode film, and recording the sample as an unrolled sample; S22. rolling the film from which the sample is taken in step S21 according to a certain compaction density, wherein the compaction density of the positive electrode film satisfies 2.0-3.0 g / cc, and the compaction density of the negative electrode film satisfies 1.2-2.0 g / cc; S23. taking a film sample corresponding to the unrolled sample from the side of the film on which the sample is taken in step S21 after the film is rolled in step S22, and recording the sample as a rolled sample; S24. selecting N detection sites from the unrolled sample and the rolled sample, wherein N is greater than or equal to 3; S25. testing the film resistance of the detection sites obtained in step S24, and recording the resistance value; S26. judging the dispersity of the conductive agent and the binder in the slurry according to the resistance value; In step S26, the judging method is as follows: if the difference between the resistance value of each unrolled sample of the positive electrode film and the average resistance value is within the range of -5 to 5 mΩ, and the difference between the resistance value of each rolled sample of the positive electrode film and the average resistance value is within the range of -5 to 5 mΩ, it is indicated that the conductive agent is uniformly dispersed; if the difference between the resistance value of any unrolled sample of the positive electrode film and the average resistance value is greater than 5 mΩ and / or the difference between the resistance value of any rolled sample of the positive electrode film and the average resistance value is greater than 5 mΩ, it is indicated that the binder is agglomerated; If the difference between the resistance value of each unrolled sample of the negative film sheet resistance and the average resistance value is within -0.05 to 0.05 mΩ, and the difference between the resistance value of each rolled sample and the average resistance value is within -0.05 to 0.05 mΩ, it indicates that the conductive agent is uniformly dispersed; if the difference between the resistance value of any unrolled sample of the negative film sheet and the average resistance value is greater than 0.1 mΩ and / or the difference between the resistance value of any rolled sample and the average resistance value is greater than 0.1 mΩ, it indicates that the binder is not well dispersed or the binder is floating.

4. The method of determining the dispersibility of a cementitious material according to claim 3, wherein, The number of unrolled samples in step S21 and rolled samples in step S23 is not less than five.

5. The method of determining the dispersibility of a cementitious material of claim 3, wherein, N is any natural number from 10 to 25.

6. The method of determining the dispersibility of a cementitious material of claim 3, wherein, The test method of the film sheet resistance adopts a single probe method, a four-probe method or a double-plane controllable pressure disc electrode resistance method.

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