Slurry defoaming method and device

Abstract

The invention belongs to the technical field of batteries, and discloses a slurry defoaming method and device. The slurry defoaming method comprises the following steps: (1) vacuumizing a container containing slurry to a first pressure, and continuously stirring the slurry for a first time; (2) injecting air flow into the container from top to bottom to reach a second pressure, and keeping the second pressure for a second time; and (3) repeating the steps (1) to (2) for 10-30 times. The slurry defoaming method is simple to operate, the defoaming efficiency can be greatly improved, and the defoaming time can be shortened.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a method and apparatus for degassing slurry. Background Technology Batteries are widely used in energy storage, electric vehicles, and portable electronic products, and the positive and negative electrodes are the core components of batteries. The main processes for preparing positive and negative electrodes include preparing battery slurry, coating, drying, rolling, and slitting (die-cutting). Among these, preparing the battery slurry mainly involves mixing active materials, binders, conductive agents, and solvents, followed by degassing, iron removal, and filtration. Degassing, as one of the core steps, significantly affects the preparation of positive and negative electrodes.

[0002] Specifically, the preparation of battery slurry generates a large number of small bubbles that are distributed throughout the slurry. If degassing is incomplete, meaning a large number of bubbles remain, it can lead to pits on the electrodes during subsequent coating, resulting in low electrode yield and increasing the risk of lithium plating during battery charging and discharging. Currently, battery slurry degassing primarily involves floating the bubbles to the surface of the slurry under vacuum conditions, allowing them to break down on their own. However, this degassing method is inefficient. Therefore, developing a highly efficient battery slurry degassing method is currently one of the challenges. Summary of the Invention

[0003] This application aims to at least partially solve one of the technical problems in the related art. To this end, this application proposes a method and apparatus for degassing slurry, which is simple to operate and can greatly improve degassing efficiency and shorten degassing time.

[0004] The first aspect of this application proposes a method for degassing slurry, comprising: (1) Vacuum the container containing the slurry to the first pressure while continuously stirring the slurry for the first time; (2) Inject airflow into the container from top to bottom to the second pressure and maintain the second pressure for a second time; (3) Repeat steps (1) to (2) above 10 to 30 times.

[0005] The degassing method of this application first expands the bubbles in the slurry under vacuum conditions, which increases the buoyancy of the bubbles. Under stirring conditions, the bubbles in the slurry will quickly float to the surface of the slurry. Then, airflow is injected into the container from top to bottom. The strong impact force of the airflow can quickly break the bubbles on the surface of the slurry, greatly improving the degassing efficiency.

[0006] In addition, the slurry degassing method according to the above embodiments of this application may also have the following additional technical features: In some embodiments, the slurry degassing method satisfies at least one of the following conditions: The pressure difference between the first pressure and the second pressure is 35 kPa to 106 kPa; The first pressure is -85 kPa to -100 kPa; The stirring speed is 10 rpm to 20 rpm; The first time is 10s to 600s. This helps to allow the air bubbles inside the slurry to rise fully to the surface of the slurry.

[0007] In some embodiments, the slurry degassing method satisfies at least one of the following conditions: The second time is 5s~180s; The second pressure is -50 kPa to 6 kPa. This helps to efficiently and fully break up air bubbles on the surface of the slurry.

[0008] In some embodiments, during the degassing process, the temperature of the slurry is maintained at 20°C to 26°C. Within this temperature range, the viscous resistance of the slurry is at a moderate level, allowing the vacuum-expanded bubbles to overcome resistance and rise smoothly without causing excessive dispersion of bubbles in the slurry due to excessively low viscosity.

[0009] In some embodiments, the airflow includes at least one of dry air and dry nitrogen, and the relative humidity of the airflow is <30%. The dry airflow itself is free of impurities, which can prevent moisture from mixing into the slurry and ensure the performance of the battery.

[0010] A second aspect of this application provides a slurry degassing device, comprising: The tank body defines the space for holding the slurry; A can lid is placed on top of the can body, and the can lid is provided with an air inlet and a negative pressure outlet; A stirring paddle is disposed on the tank lid and located in the containing space; A vacuum assembly, connected to the negative pressure port, is used to evacuate the containment space. This degassing device can efficiently remove air bubbles from the slurry, significantly shortening the degassing time.

[0011] In some embodiments, the slurry degassing device further includes: An airflow pipe is disposed on the can lid and located in the accommodating space. One end of the airflow pipe is connected to the air inlet, and the airflow pipe is provided with multiple air outlets.

[0012] In some embodiments, the slurry degassing device further includes: A thermostatic jacket is fitted over the outer surface of the tank to maintain the temperature of the tank.

[0013] In some embodiments, at least one of the following conditions is met: The diameter of the airflow pipe is 20~80mm; The diameter of the air outlet is 10mm~40mm; The straight-line distance between two adjacent air outlets is 20mm to 60mm.

[0014] In some embodiments, the airflow pipe is configured as at least one of annular, arc-shaped, and straight; preferably, when the airflow pipe is configured as straight, it includes at least one straight airflow pipe, and more preferably, the straight airflow pipes are radially distributed around the air inlet.

[0015] This ensures the strength of the airflow at the outlet and the strength of bubble breakage, thereby improving the degassing efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a battery slurry degassing device in one embodiment of this application.

[0017] Figure 2 This is a plan view of the can lid and the arrangement of different airflow pipes in one embodiment of this application.

[0018] Figure 3 This is a state diagram of the battery slurry after degassing in Embodiment 1 of this application.

[0019] Figure 4 This is a state diagram of the battery slurry after degassing in Comparative Example 1 of this application.

[0020] Figure Labels 1. Tank body; 2. Tank lid; 3. Agitator; 4. Vacuum assembly; 5. Gas flow pipe; 6. Thermostatic jacket; 21. Air inlet; 22. Negative pressure port; 51. Air outlet. Detailed Implementation The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0021] With the widespread application of various types of batteries, especially lithium-ion batteries, in the automotive industry, the battery slurry preparation process has also undergone corresponding changes, with the volume of a single slurry preparation continuously increasing. Specifically, the volume of the slurry preparation tank has expanded from the traditional 100L~200L to 300~3000L or even larger, leading to a continuous increase in degassing time. At this point, continuing to use traditional negative pressure degassing (i.e., vacuum degassing) is even less effective and takes even longer, generally requiring 6h~10h, greatly increasing energy and time costs.

[0022] In view of this, the first aspect of this application proposes a method for degassing slurry, comprising: S10: Vacuum the container containing the slurry to a first pressure while continuously stirring the slurry for a first time.

[0023] In this step, the air bubbles in the slurry expand under vacuum conditions, which increases the buoyancy of the air bubbles. Under stirring conditions, the air bubbles in the slurry will quickly float to the surface of the slurry.

[0024] Specifically, under normal pressure, the internal and external pressures of air bubbles in the slurry are balanced (i.e., the pressure inside the bubble equals the pressure outside). Under these conditions, the bubbles will not break up, nor will they float to the surface of the slurry. However, when a vacuum is applied to the container holding the slurry, the pressure inside the container becomes much lower than atmospheric pressure. The air bubbles in the slurry expand due to this pressure difference. Simultaneously, the density of the bubbles is much lower than that of the slurry, and the buoyancy of the expanded bubbles increases significantly. When the buoyancy exceeds the viscous resistance of the slurry to the bubbles, they rise to the surface. With stirring, the bubbles are more easily freed from their internal confinement in the slurry, and they quickly rise to the surface.

[0025] In some embodiments, the first pressure is -85 kPa to -100 kPa, specifically, it can be -100 kPa, -95 kPa, -90 kPa, -85 kPa, or any two of these ranges. When the pressure in the container is within the above range, the pressure inside the container is much lower than atmospheric pressure, which allows the bubbles in the slurry to expand sufficiently due to the internal and external pressure difference. This basically ensures that the buoyancy of the bubbles after their volume increases is sufficient to exceed the viscous resistance, thereby allowing them to float to the surface of the slurry.

[0026] In some embodiments, the stirring speed of the slurry is 10 rpm to 20 rpm, specifically 10 rpm, 12 rpm, 14 rpm, 16 rpm, 18 rpm, 20 rpm, etc. This speed range helps bubbles break free from their confinement within the slurry, allowing the expanded bubbles to quickly rise to the surface. Simultaneous stirring also allows a small number of bubbles located deep within the slurry to rise to the surface, further increasing the bubble rise rate.

[0027] The direction or operation of stirring in this application is not limited; stirring can be carried out according to actual conditions. For example, stirring can be carried out along the longitudinal direction of the slurry (the direction perpendicular to the upper and lower surfaces of the slurry). This allows the slurry in the lower part of the container to be turned over to the upper part to the maximum extent, thereby enabling air bubbles in the slurry to rise fully to the surface of the slurry.

[0028] In some embodiments, the first time is 10s to 600s, specifically, it can be 10s, 20s, 50s, 100s, 200s, 300s, 400s, 500s, 600s, or any range between two of them. The above time can basically ensure that the air bubbles in the slurry rise to the surface of the slurry, avoiding the impact of residual air bubbles in the slurry on the electrode yield.

[0029] S20: Inject airflow into the container from top to bottom to the second pressure, and maintain the second pressure for a second time.

[0030] In this step, airflow is injected into the container from top to bottom. The powerful impact of the airflow can quickly break up the air bubbles on the surface of the slurry, greatly improving the degassing efficiency.

[0031] In this application, the air bubbles inside the slurry are first made to float to the surface of the slurry. At this time, the air bubbles on the surface are thin film structures formed by the gas being wrapped by the slurry. The impact force of the airflow will disrupt the force balance of the thin film structure, causing the local tension of the thin film structure to exceed the bearing limit, thereby causing it to rupture rapidly.

[0032] Compared to the natural breakage of bubbles in related technologies, the airflow injection method significantly improves the efficiency of bubble breakage. Natural breakage relies on the tension decay of the bubble film itself, which is a relatively slow process; while airflow impact is an active and powerful breakage method that can break a large number of surface bubbles in a short time. In addition, the airflow injection method can make degassing more thorough, and even tiny bubbles can be quickly broken by airflow impact.

[0033] As mentioned above, the airflow is connected to the outside of the containing space (i.e., the outside world), meaning that the airflow pressure is basically the same as the outside atmospheric pressure. Furthermore, the speed and flow rate of the injected airflow are not limited; they can be adjusted according to actual conditions and needs, ensuring that the injected airflow can impact the air bubbles on the surface of the slurry.

[0034] In some embodiments, the pressure difference between the first pressure and the second pressure is 35 kPa to 106 kPa, specifically, it can be 35 kPa, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa, 100 kPa, 106 kPa, etc. A pressure difference within the above range can generally ensure sufficient impact force to disrupt the force balance of the bubble film structure, causing the local tension of the bubble to exceed its bearing limit, thereby leading to rapid rupture.

[0035] In some embodiments, the second pressure is -50 kPa to 6 kPa, specifically -50 kPa, -40 kPa, -30 kPa, -20 kPa, -10 kPa, 1 kPa, 3 kPa, 5 kPa, 6 kPa, etc. These pressures create a sufficient pressure difference, allowing the airflow to have enough impact force to break up bubbles on the slurry surface, while preventing excessive pressure differences that could cause slurry splashing during airflow impact. This helps to make the degassing process efficient and controllable.

[0036] In some embodiments, the second time is 5s to 180s. Specifically, it can be 5s, 10s, 50s, 100s, 120s, 140s, 160s, 180s, etc. The above time range can basically ensure that the bubbles expanding under vacuum are fully broken. The airflow impact time can be controlled according to the actual volume of the slurry and the size of the container.

[0037] In some embodiments, the airflow includes dry air, dry nitrogen, etc., and the relative humidity of both the dry air and dry nitrogen is <30%. Battery slurry (especially lithium battery slurry) is sensitive to moisture, which can affect the electrochemical performance of active materials and lead to subsequent battery gas generation or performance degradation. The dry airflow itself is free of impurities, preventing moisture from mixing into the slurry and ensuring the various performance characteristics of the battery. Dry nitrogen, as an inert gas, does not react with the slurry, further ensuring the quality of the slurry.

[0038] S30: Repeat steps (1) to (2) above 10 to 30 times.

[0039] In this step, steps (1) to (2) are repeated 10 to 30 times. Specifically, the number of cycles can be 10, 15, 20, 25, or 30 times, or any range between the two. The number of cycles within the above range can basically ensure complete degassing of the slurry. Steps S10 and S20 can be repeated here according to actual needs.

[0040] Specifically, the presence of dense air bubbles on the surface of the slurry under high negative pressure (less than -90 kPa) can be used to determine whether degassing of the slurry is sufficient. The absence of dense air bubbles on the surface of the slurry indicates that degassing is basically sufficient; if many air bubbles are visible on the surface of the slurry, it indicates that degassing is insufficient.

[0041] In some embodiments, the degassing process maintains the slurry temperature at 20°C to 26°C. Specifically, it can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, etc. Within this temperature range, the viscous resistance of the slurry is at a moderate level, allowing the vacuum-expanded bubbles to overcome resistance and rise smoothly without excessive dispersion due to low viscosity. Furthermore, because the viscosity and dispersibility of the battery slurry (typically containing active materials, binders, etc.) do not fluctuate significantly within the above temperature range, the slurry will not thicken due to excessively low temperatures (increasing bubble rising resistance), nor will the binders and other components react or denature due to excessively high temperatures, thus ensuring the performance of the subsequent battery electrodes.

[0042] This degassing method is applicable to the degassing of various slurries except battery slurries, and the temperature during the degassing process can be adjusted according to actual needs.

[0043] A second aspect of this application proposes a slurry degassing device, referring to... Figure 1 The system includes: a tank body 1, a tank cover 2, a stirring paddle 3, and a vacuum assembly 4. The tank body 1 defines a containment space for holding slurry. The tank cover 2 is positioned above the tank body 1 and has an air inlet 21 and a negative pressure port 22. The stirring paddle 3 is mounted on the tank cover and located within the containment space. Specifically, the distance from the lower beam of the stirring paddle 3 to the bottom of the tank body 1 is 5mm to 10mm. The vacuum assembly 4 is connected to the negative pressure port 22 and is used to evacuate the containment space.

[0044] In some embodiments, refer to Figure 1 The slurry degassing device further includes an airflow pipe 5, which is installed on the tank cover 2 and located in the accommodating space. One end of the airflow pipe 5 is connected to the air inlet 21, and the airflow pipe is provided with multiple air outlets 51. The airflow is evenly injected into the tank 1 through the air inlet 51 to achieve the purpose of breaking up air bubbles.

[0045] In some embodiments, refer to Figure 1 The slurry degassing device also includes a thermostatic jacket 6, which is fitted onto the outer surface of the tank 1 to maintain the temperature of the tank. Thus, by adjusting the temperature of the thermostatic jacket, the slurry inside the tank can be kept at the target temperature.

[0046] The aforementioned battery slurry degassing device uses a vacuum assembly 4 to evacuate the tank 1 containing the slurry. Simultaneously, the slurry is continuously stirred by a stirring paddle 3, causing the air bubbles in the slurry to rise rapidly to the surface. Airflow enters the airflow pipe 5 through the air inlet 21 and then enters the tank 1 through multiple air outlets 51 along the airflow pipe 5, achieving the purpose of breaking up air bubbles in all directions.

[0047] In some embodiments, the diameter of the airflow pipe is 20mm to 80mm, specifically, it can be 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, etc. A diameter within the above range can generally ensure sufficient airflow, thereby guaranteeing the strength of bubble breakage.

[0048] In some embodiments, the diameter of the air outlet is 10mm~40mm (specifically, it can be 10mm, 20mm, 30mm, 40mm, etc.), and the straight-line distance between two adjacent air outlets is 20mm~60mm (specifically, it can be 20mm, 30mm, 40mm, 50mm, 60mm, etc.). This further ensures the intensity of the airflow at the air outlet, further ensures the intensity of bubble breakage, and thus improves the degassing efficiency.

[0049] In some embodiments, refer to Figure 2 , Figure 2 In the diagram, A is a plan view of can lid 2. Figure 2 B, C, and D in the diagram represent different airflow pipe configurations. Specifically, the airflow pipes on the tank lid can be configured in at least one of the following ways: annular, arc-shaped, or straight, with the air outlets radially distributed from the air inlet. When the airflow pipes are straight, they include at least one straight airflow pipe. This radially distributed air outlet configuration, combined with the airflow pipe configuration, allows airflow to evenly cover the slurry area within the tank from different directions, achieving omnidirectional airflow agitation. This helps avoid incomplete degassing caused by localized airflow concentration or blind spots.

[0050] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0051] Example 1 The positive electrode active material, conductive agent, binder and dispersant were mixed in a mass ratio of 96.8:1.5:1.5:0.2 to obtain 500L of battery slurry. The slurry was placed in the slurry degassing device of this application. The inside of the device was evacuated by the vacuum component to make the pressure inside the tank reach -90 kPa and maintain it under vacuum for 200s. Dry nitrogen gas is injected into the tank through the air inlet on the tank lid, so that the pressure inside the tank reaches -10 kPa and lasts for 100 seconds. The above vacuuming and gas injection cycle was repeated 12 times to complete the degassing process, which took 2 hours in total. During the above degassing process, the slurry is continuously stirred (so that the slurry at the bottom of the container is turned over to the top) at a speed of 15 rpm, and the temperature of the slurry is maintained at 25°C.

[0052] Examples 2-13 Same as Example 1, the main differences are shown in Table 1.

[0053] Comparative Example 1 Same as Example 1, the main difference being: no airflow injection. Specifically, the container holding the battery slurry is evacuated to -90 kPa while the slurry is continuously stirred for 8 hours.

[0054] Comparative Example 2 Similar to Comparative Example 1, the main differences are shown in Table 1.

[0055] Test results After degassing, the surface of the slurry was observed visually. The surface condition of the slurry after 2 hours of degassing in Example 1 is shown below. Figure 3 As can be seen, there are no obvious air bubbles on the surface of the slurry, which indicates that degassing is complete; The surface condition of the slurry after degassing for 8 hours in Comparative Example 1 is shown in the figure. Figure 4 As can be seen, there are dense air bubbles on the surface of the slurry, indicating that degassing is not sufficient.

[0056] Table 1

[0057] Conclusion: It can be seen that the degassing method of this application can greatly improve the degassing efficiency and reduce the degassing time.

[0058] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0059] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0060] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0061] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0062] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0063] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for degassing slurry, characterized in that, include: (1) Vacuum the container containing the slurry to the first pressure while continuously stirring the slurry for the first time; (2) Inject airflow into the container from top to bottom to the second pressure and maintain the second pressure for a second time; (3) Repeat steps (1) to (2) above 10 to 30 times.

2. The slurry degassing method according to claim 1, characterized in that, At least one of the following conditions must be met: The pressure difference between the first pressure and the second pressure is 35 kPa to 106 kPa; The first pressure is -85 kPa to -100 kPa; The stirring speed is 10 rpm to 20 rpm; The first time interval is 10s to 600s.

3. The slurry degassing method according to claim 1, characterized in that, At least one of the following conditions must be met: The second time is 5s~180s; The second pressure is -50kPa to 6kPa.

4. The slurry degassing method according to claim 1, characterized in that, During the degassing process, the temperature of the slurry is maintained at 20℃~26℃.

5. The slurry degassing method according to claim 1, characterized in that, The airflow includes at least one of dry air and dry nitrogen, and the relative humidity of the airflow is <30%.

6. A slurry degassing apparatus for use in the slurry degassing method according to any one of claims 1 to 5, characterized in that, include: The tank body defines the space for holding the slurry; A can lid is placed on top of the can body, and the can lid is provided with an air inlet and a negative pressure outlet; A stirring paddle is disposed on the tank lid and located in the containing space; A vacuum assembly, connected to the negative pressure port, is used to evacuate the containment space.

7. The slurry degassing device according to claim 6, characterized in that, Also includes: An airflow pipe is disposed on the can lid and located in the accommodating space. One end of the airflow pipe is connected to the air inlet, and the airflow pipe is provided with multiple air outlets.

8. The slurry degassing device according to claim 7, characterized in that, Also includes: A thermostatic jacket is fitted over the outer surface of the tank to maintain the temperature of the tank.

9. The slurry degassing device according to claim 7, characterized in that, At least one of the following conditions must be met: The diameter of the airflow pipe is 20~80mm; The diameter of the air outlet is 10mm~40mm; The straight-line distance between two adjacent air outlets is 20mm to 60mm.

10. The slurry degassing device according to claim 7, characterized in that, The airflow duct is configured as at least one of annular, arc-shaped, and straight. Preferably, when the airflow pipe is configured as a straight line, it includes at least one straight airflow pipe, and more preferably, the straight airflow pipes are radially distributed with the air inlet as the center.

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