A slurry stability evaluation device and evaluation method

Abstract

A slurry stability evaluation device includes a bracket, pulleys are fixed on both sides of the bracket, a lead is connected between the two pulleys, the two ends of the lead are respectively connected to a shaft and a weight plate, a test rod is arranged on the shaft, and convex points are distributed on the surface of the test rod; a measuring cup is placed under the shaft; the mass of the weight plate is equal to the mass of the shaft and the test rod; the combined force of the gravity of the shaft and the test rod is greater than the buoyancy of the test rod when it is completely immersed in the slurry. The present invention has a simple structure, simple operation, and is extremely convenient to assemble, disassemble, replace and clean, and can be used repeatedly; the test rod structure absorbs agglomerates or gels in the suspended slurry, and the mass of the agglomerates is intuitively displayed by accumulating the total mass of the weights. The stability curve of the slurry can be obtained through multiple tests, and then the stability of the slurry system can be judged, and the evaluation test efficiency, reliability and accuracy all meet the requirements.

Description

Technical Field

[0001] The present invention relates to the field of slurry stability evaluation, and in particular to a slurry stability evaluation device and an evaluation method. Background Art

[0002] The stability of lithium battery slurry is a basic indicator that affects the performance of electrodes and batteries. The slurry suspension system with good consistency, high uniformity, good dispersibility and good stability directly affects the consistency of slurry coating surface density, pole piece compaction flexibility, pole piece porosity richness, membrane resistivity, peel strength, as well as the battery's DCR resistance, rate temperature rise, electrode heating and long-term cycle life.

[0003] The evaluation method and equipment for slurry stability are crucial. In general, the current technology has the following shortcomings: (1) The viscometer equipment is expensive, which increases the cost pressure of the enterprise; (2) The viscometer has high precision requirements, high maintenance costs, and is difficult to repair; (3) The viscometer has a single function and can only characterize the change in slurry viscosity, but cannot see the agglomeration phenomenon caused by the van der Waals force and excessive surface energy between the fine particles in the slurry; (4) The operation method and steps are relatively complicated, making it difficult to achieve rapid evaluation and for the experimenter to master the skills.

[0004] Therefore, there is an urgent need for a low-cost, simple and practical device to test and evaluate the slurry stability and dispersion effect. Summary of the invention

[0005] According to the problems raised in the background technology, the present invention provides a slurry stability evaluation device and an evaluation method to solve the problems, and the present invention will be further explained below.

[0006] The present invention provides a slurry stability evaluation device, which utilizes the fixed pulley transmission and interaction force balance principle to not only quantify the agglomeration and sedimentation of slurry particles as a gravity change index, but also can intuitively see the severity and appearance of particle molecular agglomeration inside the slurry system, thereby providing important data basis for formula optimization of lithium battery homogenization process and identification of slurry stability and uniformity, thereby ensuring excellent manufacturing process of electrode processing.

[0007] A slurry stability evaluation device comprises a bracket, pulleys are fixed on both sides of the bracket, a lead is connected between the two pulleys, both ends of the lead are respectively connected to a shaft and a weight plate, a test rod is arranged on the shaft, and holes are densely distributed in the test rod; a measuring cup is placed under the shaft; the mass of the weight plate is equal to the sum of the masses of the shaft and the test rod; the combined force of the gravity of the shaft and the test rod is greater than the buoyancy of the test rod when it is completely immersed in the slurry.

[0008] Preferably, the bracket includes a chassis, a column fixedly connected to the chassis, and a crossbeam fixedly connected to the column, and the pulleys are fixed on both sides of the crossbeam.

[0009] Preferably, a slide groove is provided on the crossbeam, a slider is provided in the slide groove, and the lead is divided into two sections connected on both sides of the slider; a limiting protrusion extending into the slide groove is provided on the crossbeam, and a stop groove is formed between the limiting protrusion and the crossbeam; when the test rod is immersed in the slurry, the slider falls into the stop groove.

[0010] Preferably, a raised guide cylinder is provided at the bottom of the measuring cup, and the axis of the guide cylinder coincides with the axis of the shaft rod in the free state; the inner diameter of the guide cylinder is consistent with the diameter of the shaft rod, and there is always a section of the lower end of the shaft rod located inside the guide cylinder; the guide cylinder has a radial limiting effect and a vertical guiding effect on the shaft rod, thereby ensuring measurement accuracy.

[0011] Preferably, a flow hole is provided on the side wall of the lower end of the guide cylinder, and the shaft rod and the guide cylinder form a column cavity with dynamically changing volume. The flow hole forms a slurry flow passage between the column cavity and the outside of the guide cylinder, so that the external slurry can enter the column cavity and thus smoothly pull the shaft rod.

[0012] Preferably, a filter cloth covering the flow hole is wound around the bottom of the guide cylinder to prevent small particles from entering the column cavity through the flow hole and being deposited in the column cavity after agglomeration for a long time.

[0013] Preferably, the width of the filter cloth is just enough to cover the flow holes, thereby reducing the interference of the filter cloth on the deposition and adsorption of particles.

[0014] Preferably, a positioning groove is provided on the chassis, and the measuring cup has the same diameter as the positioning groove; the axis of the positioning groove is vertical and coincides with the lead-out direction of the pulley; placing the measuring cup on the positioning groove automatically ensures that the shaft rod and the guide cylinder are coaxial.

[0015] The method for evaluating slurry stability comprises the following steps:

[0016] Pull the lead wire until the slider falls into the stop groove. At this time, the test rod is immersed in the slurry. After standing for a preset time, the particles suspended in the slurry aggregate into blocks and adsorb on the test rod.

[0017] Pull the lead wire to pull the slider out of the stop slot until the test rod is suspended on the slurry, and add weights to the weight plate until the lead wire is balanced and still. At this time, the mass of the weight is the mass of the particles agglomerated from the slurry;

[0018] Repeat the above steps to obtain the slurry quality change curve under different standing times, and the slurry stability result can be obtained by evaluating the curve.

[0019] Beneficial effects: Compared with the prior art, the present invention has a simple structure, simple operation, extremely convenient assembly, disassembly, replacement and cleaning, and can be used repeatedly; the test rod structure adsorbs agglomerates or gels in the suspended slurry, and intuitively displays the mass of the agglomerates by accumulating the total mass of the weights. The stability curve of the slurry can be obtained through multiple tests, and then the stability of the slurry system can be judged, and the test efficiency, reliability and accuracy can meet the requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 : A schematic diagram of the structure of the present invention;

[0021] Figure 2 : Figure 1 A schematic diagram of the structure enlargement at the center A;

[0022] In the figure: bracket 1, chassis 11, positioning groove 111, column 12, beam 13, slide groove 131, limiting protrusion 132, stop groove 133, pulley 2, lead 3, shaft 4, weight plate 5, test rod 6, measuring cup 7, guide cylinder 71, flow hole 711, column cavity 72, slider 8, filter cloth 9. DETAILED DESCRIPTION

[0023] Next, a specific embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0024] A slurry stability evaluation device includes a bracket 1 as a main body, the bracket 1 includes a chassis 11, a column 12 fixedly connected to the chassis, and a crossbeam 13 fixedly connected to the column, movable pulleys 2 for changing the direction of the lead are fixed on both sides of the crossbeam 13, a lead 3 is connected between the two pulleys, and both ends of the lead are respectively connected to an axle 4 and a weight plate 5, a test rod 6 is arranged on the axle 4, the test rod has abundant holes, has a large specific surface area, and has a strong adsorption capacity for suspended particles, and the weight plate 5 is used for placing weights; a measuring cup 7 is placed under the axle 4 for containing the slurry to be evaluated.

[0025] The present invention is used to evaluate the stability of slurry. A test stick is immersed in the slurry. When the slurry is left stationary, if the particles inside the suspension are not well dispersed, the conductive agent and the active material are easily agglomerated due to the large surface energy of the conductive agent. Under the combined influence of van der Waals forces, a large amount of adsorption and aggregation occurs between the conductive agent and the active material, and the particles agglomerate into blocks, and then adsorb on the test stick. By measuring the mass of the aggregated particles, the mass of the remaining slurry can be obtained. By multiple measurements at the same time interval, a stability curve of the slurry can be obtained. By comparing the positive and negative electrode slurries, the stability evaluation result of the slurry can be obtained.

[0026] In this embodiment, the mass of the weight added to the weight plate 5 is directly represented by the mass of the particles adsorbed by the slurry agglomeration on the test rod, and the mass of the weight plate is equal to the mass of the shaft and the test rod. Based on this, the evaluation method of the slurry stability is as follows:

[0027] S1, immerse the test rod in the slurry and let it stand for a preset time, so that the particles suspended in the slurry aggregate into blocks and adsorb on the test rod;

[0028] S2, pull the lead wire to suspend the test rod on the slurry, and add weights to the weight plate until the lead wire is balanced and still. At this time, the mass of the weight is the mass of the particles agglomerated from the slurry;

[0029] S3, repeat the above steps to obtain the slurry quality change curve under different standing times, and the slurry stability result can be obtained by evaluating the curve.

[0030] It should be noted that when the test rod is immersed in the slurry, the test rod will inevitably be affected by the buoyancy of the slurry. In order to make the mass of the weight intuitively represent the mass of the particles adsorbed on the test rod by the slurry agglomeration, this embodiment sets the mass of the weight plate to be equal to the mass of the shaft and the test rod. In this way, in the absence of external force intervention, the test rod cannot be completely immersed in the slurry under the buoyancy and the tension of the lead wire, affecting the adsorption effect. In one embodiment, in order to reduce human interference, the combined force of the gravity of the shaft and the test rod is greater than the buoyancy of the test rod when it is completely immersed in the slurry, that is, if the weight plate is removed, the test rod will be immersed in the slurry under its own weight. Therefore, the slurry stability evaluation method also includes step S0 before step S1, removing the weight plate from the lead wire.

[0031] This embodiment is a preferred embodiment. To avoid the complexity of operation, a slide groove 131 is provided on the crossbeam 13, a slider 8 is provided in the slide groove, the lead wire is divided into two sections connected to both sides of the slider, and a limiting protrusion 132 extending into the slide groove is provided on the crossbeam 13, and a stop groove 133 is formed between the limiting protrusion and the crossbeam. When the test rod is immersed in the slurry, the lead wire pulls the slider to slide in the slide groove until it falls into the stop groove 133. The combined force of the gravity of the shaft rod and the test rod is greater than the buoyancy of the test rod when it is completely immersed in the slurry. At this time, the weight plate is always connected to the lead wire without disassembly, and the combined force of the lead wire pulling the slider is offset by the force of the limiting protrusion 132 on the slider, and the slider is stationary in the stop groove, so that the test rod can be stationary and immersed in the slurry.

[0032] In this embodiment, the evaluation method of slurry stability is as follows:

[0033] S1, pull the lead wire until the slider falls into the stop groove, at which time the test rod is immersed in the slurry and left to stand for a preset time. The particles suspended in the slurry aggregate into blocks and are adsorbed on the test rod;

[0034] S2, pull the lead wire to pull the slider out of the stop slot until the test rod is suspended on the slurry, add weights to the weight plate until the lead wire is balanced and still. At this time, the mass of the weight is the mass of the particles agglomerated from the slurry;

[0035] S3, repeat the above steps to obtain the slurry quality change curve under different standing times, and the slurry stability result can be obtained by evaluating the curve.

[0036] When evaluating stability, the present invention uses the stability curve of the obtained slurry as a standard for judgment. For example, in this embodiment, the slurry is measured by the above-mentioned evaluation method after being left to stand for 0h, 4h, 8h, 24h, and 48h. The weight of the agglomerated particles of the slurry is tested by increasing the number of weights, and the sedimentation weight can be calculated. The experimental point data are fitted into a stability curve, and the stability curves of the positive and negative electrode slurries are measured respectively. The stability conclusion can be obtained by analyzing the curves.

[0037] During operation, when the test rod is pulled up and suspended, the suspended test rod shakes, and the measurement accuracy is affected in the shaking state. At this time, it is inconvenient for the operator to manually intervene in the test rod to make it still, because it is easy to shake off the adsorbed particles. In this embodiment, a raised guide cylinder 71 is provided at the bottom of the measuring cup 7, and the axis of the guide cylinder coincides with the axis of the shaft rod 4 in the free state. There is always a section of the lower end of the shaft rod 4 located in the guide cylinder 71, and the guide cylinder has a limiting and guiding effect on the shaft rod. No matter what height the lead wire pulls the shaft rod at, the guide cylinder has a radial limiting effect and a vertical guiding effect on the shaft rod. When suspended, the radial limiting effect of the guide cylinder on the shaft rod avoids the shaking of the test rod and ensures the measurement accuracy.

[0038] When the shaft rod 4 is relatively displaced in the guide cylinder 71, according to common sense, in order to ensure that the guide cylinder has a radial limiting effect on the shaft rod and a vertical guiding effect, the inner diameter of the guide cylinder is consistent with the diameter of the shaft rod, and particles are prevented from falling into the guide cylinder. In this case, the present embodiment is provided with a flow hole 711 on the side wall of the lower end of the guide cylinder 71. When the shaft rod is pulled, the shaft rod and the guide cylinder form a column cavity 72 with a dynamically changing volume. The existence of the flow hole allows the external slurry to enter the column cavity, thereby smoothly pulling the shaft rod.

[0039] After the particles are aggregated, they will be adsorbed by the test rod. There are small particles that have not aggregated that enter the column cavity through the flow hole. After a long period of aggregation, they are deposited in the column cavity. In this embodiment, a filter cloth 9 is wrapped around the bottom of the guide cylinder 71 to wrap the flow hole 711. Preferably, the width of the filter cloth just covers the flow hole 711 to reduce the interference of the filter cloth on the deposition and adsorption of the particles.

[0040] In this embodiment, a positioning groove 111 is provided on the chassis 11, the measuring cup has the same diameter as the positioning groove, and the axis of the positioning groove is vertical and coincides with the lead-out direction of the pulley, that is, placing the measuring cup on the positioning groove automatically ensures that the shaft rod and the guide cylinder are coaxial.

[0041] The invention has a simple structure, is easy to operate, is extremely convenient to assemble, disassemble, replace and clean, and can be used repeatedly; the test rod structure absorbs agglomerates or gels in the suspended slurry, and intuitively displays the mass of the agglomerates by accumulating the total mass of the weights; the stability curve of the slurry can be obtained through multiple tests, and then the stability of the slurry system can be judged, and the test efficiency, reliability and accuracy can all meet the requirements.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A slurry stability evaluation device, characterized in that include: A bracket (1), pulleys (2) are fixed on both sides of the bracket (1), a lead wire (3) is connected between the two pulleys, and the two ends of the lead wire are respectively connected to a shaft (4) and a weight plate (5), a test rod (6) is arranged on the shaft (4), and the surface of the test rod (6) is densely covered with convex points; a measuring cup (7) is placed under the shaft (4); the mass of the weight plate is equal to the mass of the shaft and the test rod; the combined force of the gravity of the shaft and the test rod is greater than the buoyancy of the test rod when it is completely immersed in the slurry; The bracket (1) comprises a chassis (11), a column (12) fixedly connected to the chassis, and a crossbeam (13) fixedly connected to the column, and the pulley (2) is fixed on both sides of the crossbeam (13); A slide groove (131) is provided on the crossbeam (13), a slider (8) is provided in the slide groove, and the lead wire is divided into two sections connected to two sides of the slider; a limiting protrusion (132) extending into the slide groove is provided on the crossbeam (13), and a stop groove (133) is formed between the limiting protrusion and the crossbeam; when the test rod is immersed in the slurry, the slider falls into the stop groove (133).

2. The slurry stability evaluation device according to claim 1, characterized in that: A guide tube (71) is provided at the bottom of the measuring cup (7), the axis of the guide tube coincides with the axis of the shaft rod (4) in a free state; the inner diameter of the guide tube is consistent with the diameter of the shaft rod, and a certain length of the shaft rod (4) is always located in the guide tube (71).

3. The slurry stability evaluation device according to claim 2, characterized in that: A flow hole (711) is provided on the side wall of the lower end of the guide cylinder (71), the shaft rod and the guide cylinder form a column cavity (72) with a dynamically changing volume, and the flow hole forms a slurry flow passage between the column cavity and the outside of the guide cylinder.

4. The slurry stability evaluation device according to claim 3, characterized in that: The bottom of the guide cylinder (71) is wound with a filter cloth (9) that wraps the flow hole (711).

5. The slurry stability evaluation device according to claim 4, characterized in that: The width of the filter cloth just covers the flow hole (711).

6. The slurry stability evaluation device according to claim 5, characterized in that: A positioning groove (111) is provided on the chassis (11), and the measuring cup has the same diameter as the positioning groove; the axis of the positioning groove is vertical and coincides with the lead-out direction of the pulley.

7. A slurry stability evaluation method based on the slurry stability evaluation device according to claim 6, characterized in that The steps include: S1, pull the lead wire until the slider falls into the stop groove, at which time the test rod is immersed in the slurry and left to stand for a preset time. The particles suspended in the slurry aggregate into blocks and are adsorbed on the test rod; S2, pull the lead wire to pull the slider out of the stop slot until the test rod is suspended on the slurry, add weights to the weight plate until the lead wire is balanced and still. At this time, the mass of the weight is the mass of the particle slurry agglomerated from the slurry; S3, repeat the above steps to obtain the slurry quality change curve under different standing times, and the slurry stability result can be obtained by evaluating the curve.

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