A defoaming method for lithium battery separator slurry

Abstract

The present application relates to a kind of lithium battery separator slurry defoaming method, slurry in slurry tank I is transferred to slurry tank II using siphon device;Siphon device includes discharge pipe II and sequentially closed communication feed pipe, filter box and discharge pipe I;Filter box is provided with ultrasonic emission device for separating gas bubble and slurry in the inside, filter box is located in the discharge port of feed pipe and the feed port of discharge pipe I, the feed port of feed pipe is below low liquid level line of slurry tank I, the discharge port of discharge pipe I is below the liquid level of slurry in slurry tank II, the feed port of discharge pipe II is closed with filter box Communication point is located above ultrasonic emission device;Switch II is installed on discharge pipe II.The device in the present application is simple in structure, slurry is transferred using siphon principle, ultrasonic emission device breaks small gas bubble existing in slurry, and it is guaranteed that the slurry output is bubble-free.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery manufacturing technology and relates to a defoaming method for lithium battery separator slurry. Background Technology

[0002] The purpose of coating the lithium battery separator with ceramic paste is to increase its heat resistance. During the coating process, the paste is stored in a paste tank and pumped at a uniform flow rate to the doctor blade box. The doctor blade box and the gravure roller form a closed space with a certain pressure. A portion of the paste is carried away by the gravure roller and evenly printed onto the lithium battery surface, while the remaining paste flows into the buffer tank and is eventually returned to the paste buffer tank. Because the paste contains some adhesives, a large number of air bubbles are likely to appear during the return process to the paste tank.

[0003] If there are a lot of air bubbles in the slurry, it will cause spot-like missed coating or slurry agglomeration during the coating process of the separator slurry. These problems result in poor uniformity of the coated separator. Since the battery releases a lot of heat when charging and discharging, there will be uneven thermal shrinkage between the areas where the ceramic slurry is coated and the areas where it is missed. When the thermal shrinkage reaches a certain level, it will cause a short circuit between the positive and negative electrodes of the battery, affecting the safety of battery use.

[0004] Most existing degassing methods use vacuum physical degassing and chemical degassing methods:

[0005] The principle of chemical defoaming is to add surfactants of opposite types, adjust the pH value, and add defoamers and other chemical agents to the foam base liquid to change certain properties of the foaming agent and achieve the purpose of defoaming. However, after the bubbles are eliminated by chemical defoaming, the original properties of the base liquid will change and secondary pollution will occur.

[0006] Vacuum defoaming works on the relationship between the size of bubbles inside a liquid and the external pressure. When the external pressure decreases, the bubble volume increases. Once the atmospheric pressure at the liquid surface decreases rapidly (vacuuming), the bubble volume inside the liquid increases rapidly, and the buoyancy naturally increases, causing the bubbles to quickly float to the liquid surface and release their internal gas. As a result, the bubbles disappear more quickly. The dissolved gas inside the liquid also precipitates out due to the reduced solubility caused by the decrease in liquid surface pressure. However, because the slurry has a certain viscosity, the bubbles and liquid are fused together. Within a certain volume, it takes a certain amount of time, pressure, and flow rate to completely separate the bubbles and precipitate them out. The conditions and equipment required are quite demanding.

[0007] Patent CN212166605U discloses a battery slurry bubble elimination device, including a tank with a slurry inlet at the bottom, through which slurry flows in against the tank wall. A stirring shaft is vertically mounted inside the tank, with a stirring paddle mounted on it. A driving mechanism is located at the top of the tank, connected to the stirring shaft, which drives the stirring shaft to rotate the stirring paddle around it. This patent uses a vacuum defoaming principle, but its drawback is that when a fixed volume of slurry is vacuumed, a certain amount of time is required for complete bubble elimination. Although the patent design includes vacuuming, the slurry is in a flowing state during use. When the slurry flow rate in the storage tank is high, the storage time of the bubble-laden liquid in the buffer tank is relatively short, thus failing to completely eliminate the bubbles.

[0008] Therefore, proposing a new defoaming method is of great significance. Summary of the Invention

[0009] The purpose of this invention is to solve the problems existing in the prior art and provide a defoaming method for lithium battery separator slurry.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A defoaming method for lithium battery separator slurry involves using a siphon device to transfer the lithium battery separator slurry from slurry tank I to slurry tank II.

[0012] The siphon device includes discharge pipe II and feed pipe, filter box and discharge pipe I connected in sequence in a closed manner. The reason for choosing the siphon device for slurry transfer is that the air pressure used to extract the slurry in slurry tank I can prevent most large air bubbles from entering the filter box (taking advantage of the material characteristics of lighter air bubbles, large air bubbles are generally present on the surface of the liquid).

[0013] The feed inlet of the feed pipe is located below the low liquid level line of slurry tank I; the volume of the part below the low liquid level line in slurry tank I is 3 / 10 of the total volume of slurry tank I; since bubbles are relatively light, they generally exist above the low liquid level line of slurry tank I. The feed pipe being below the low liquid level line ensures that there are fewer large bubbles in the slurry drawn from slurry tank I.

[0014] The outlet of discharge pipe I is located below the liquid surface of the slurry in slurry tank II; this ensures that no air bubbles will be generated in the slurry after it has been cleaned. If the outlet were above the slurry tank, it would cause some air bubbles to appear when it flows into the liquid due to the height of the outlet.

[0015] The filter box is located above the outlet of the feed pipe and the inlet of the discharge pipe I; the filter box is a sealed container; the interior of the filter box is equipped with an ultrasonic emission device for separating air bubbles and slurry.

[0016] When there are no small air bubbles in the slurry, the filter box is completely filled during the slurry flow. When there are small air bubbles in the slurry, due to the certain viscosity of the slurry, the small air bubbles will generally be integrated with the slurry. Without external action, they are not easy to separate. At this time, the ultrasonic emission device located in the filter box will play a role. It will use the destructive characteristics of high-frequency sound vibration to cause the small air bubbles in the slurry flowing through the filter box to burst. The air generated by the bursting small air bubbles will exist in the upper part of the sealed filter box.

[0017] The inlet of discharge pipe II is in a sealed connection with the filter box, and the connection point is located above the ultrasonic transmitting device. This ensures that the air generated by the small bubbles that burst in the filter box can be discharged from discharge pipe II.

[0018] A switch II is installed on the discharge pipe II. When it is necessary to discharge the air generated by the small bubbles in the filter box from the discharge pipe II, switch II is turned on; otherwise, switch II is turned off.

[0019] As a preferred technical solution:

[0020] As described above, a defoaming method for lithium battery separator slurry comprises a feed pipe consisting of a vertical section a, a bent section b, a horizontal section c, a bent section d, a vertical section e, a bent section f, a horizontal section g, a bent section h, and a vertical section i, which are connected in a closed manner from left to right. The horizontal section c is located above the vertical sections a and e, and the horizontal section g is located below the vertical sections e and i. The outlet of the vertical section i is the outlet of the feed pipe. The discharge pipe I is arranged vertically with the inlet at the top and the outlet at the bottom. The feed pipe is located to the left of the discharge pipe I. The discharge pipe II is arranged vertically with the inlet at the top and the outlet at the bottom.

[0021] In the defoaming method for lithium battery separator slurry described above, the outlet of the feed pipe and the inlet of the discharge pipe I are at the same horizontal position.

[0022] As described above, in a defoaming method for lithium battery separator slurry, the inlet of the feed pipe is higher than the outlet of the outlet pipe I; the bottom inner diameter of the slurry tank I is 40cm, the middle inner diameter is 50cm, and the height is 60cm; the distance between the inlet of the feed pipe and the bottom of the slurry tank I is 2cm; the inner diameter of the feed pipe is 20-32mm, and the inner diameter of the outlet pipe I is the same as the inner diameter of the feed pipe.

[0023] The defoaming method for lithium battery separator slurry described above includes a filter layer inside the filter box for separating air bubbles.

[0024] The discharge port of the feed pipe and the feed port of discharge pipe I are both flush with the bottom wall of the filter box;

[0025] The distance between the upper surface of the filter layer and the top wall of the filter box is not less than 15cm, and the lower surface of the filter layer is in contact with the bottom wall of the filter box.

[0026] The filter layer is located below the ultrasonic transmitter.

[0027] The defoaming method for lithium battery separator slurry described above uses a sponge filter layer. The mesh size of the sponge filter layer is 80-120 mesh. When there are bubbles, they are relatively light and will be isolated to the upper part by the sponge filter layer.

[0028] In the defoaming method for lithium battery separator slurry described above, the distance between the ultrasonic transmitter and the filter layer is 1-2 cm, and the frequency of the ultrasonic transmitter is 20±0.5KHZ.

[0029] In the defoaming method for lithium battery separator slurry described above, a portion of the length of the discharge pipe I is an exhaust bladder I, and a switch I is installed on the length between the inlet of the discharge pipe I and the exhaust bladder I.

[0030] The defoaming method for lithium battery separator slurry described above includes a siphon device further comprising a slurry tank III; the outlet of the discharge pipe II is located in the slurry tank III.

[0031] In the defoaming method for lithium battery separator slurry described above, a portion of the length of the discharge pipe II is an exhaust bladder II, which is located above the switch II.

[0032] Beneficial effects:

[0033] The device in this invention draws slurry from the low liquid level line of slurry tank I, ensuring that the drawn slurry can block most large air bubbles; the ultrasonic emission device and filter layer in the filter box destroy small air bubbles in the slurry, and the air generated after the small air bubbles are destroyed is discharged at the filter box; ensuring that the output slurry is free of air bubbles.

[0034] The device in this invention has a simple structure and uses the siphon principle to make the slurry flow from a high place to a low place under the action of gravity. The slurry does not need to provide kinetic energy to flow between slurry tanks, which can save energy compared with traditional equipment. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of the device in this invention;

[0036] Figure 2 This is a schematic diagram of the internal structure of the filter box in this invention;

[0037] Among them, 1-slurry tank I, 2-slurry tank II, 3-feed pipe, 4-filter box, 5-discharge pipe I, 6-filter layer, 7-ultrasonic emission device, 8-discharge pipe II, 9-slurry tank III, 10-switch II, 11-exhaust bag I, 12-switch I, 13-exhaust bag II. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be understood that the terms "upper," "lower," "left," "right," etc., indicate orientation or positional relationships based on the appended figures. Figure 1 The orientations or positional relationships shown are for the convenience of describing the present 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 the present invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0039] A siphon device, such as Figures 1-2 As shown, it includes a feed pipe 3, a filter box 4, a discharge pipe I 5, a discharge pipe II 8, an ultrasonic transmitting device 7, a filter layer 6, and a slurry tank III 9.

[0040] like Figure 1 As shown, the feed pipe 3 consists of a vertical section a, a bend section b, a horizontal section c, a bend section d, a vertical section e, a bend section f, a horizontal section g, a bend section h, and a vertical section i, which are connected in a closed manner from left to right. The horizontal section c is located above the vertical sections a and e, and the horizontal section g is located below the vertical sections e and i. The inner diameter of the feed pipe 3 is 20-32 mm.

[0041] like Figure 1 As shown, filter box 4 is a sealed container;

[0042] like Figure 1 As shown, the discharge pipe I 5 is arranged vertically, with the inlet at the top and the outlet at the bottom. A section of the discharge pipe I 5 is an exhaust bladder I 11. A switch I 12 is installed on the section between the inlet and the exhaust bladder I 11 of the discharge pipe I 5. The inner diameter of the section of the discharge pipe I 5 that is not an exhaust bladder I 11 is the same as the inner diameter of the inlet pipe 3.

[0043] like Figure 1 As shown, the feed pipe 3 is located to the left of the discharge pipe I 5, and the filter box 4 is located above the feed pipe 3 and the discharge pipe I 5. The discharge port of the vertical section i and the feed port of the discharge pipe I 5 are flush with the bottom wall of the filter box 4. The vertical section i, the filter box 4 and the discharge pipe I 5 are sequentially and tightly connected.

[0044] like Figure 2 As shown, the filter layer 6 is disposed inside the filter box 4 (preferably an 80-120 mesh sponge filter layer), the upper surface of the filter layer 6 is at least 15cm away from the top wall of the filter box 4, and the lower surface of the filter layer 6 is in contact with the bottom wall of the filter box 4.

[0045] like Figure 2 As shown, the ultrasonic transmitting device 7 is installed inside the filter box 4 and is located 1-2 cm above the filter layer 6; the frequency of the ultrasonic transmitting device 7 is 20±0.5KHZ.

[0046] like Figure 1 As shown, the discharge pipe II 8 is arranged vertically with the inlet at the top and the outlet at the bottom. A switch II 10 is installed on the discharge pipe II 8. A section of the discharge pipe II 8 is an exhaust bladder II 13, which is located above the switch II 10.

[0047] like Figure 1 As shown, the inlet of the discharge pipe II 8 is in sealed connection with the filter box 4, and the connection point is located above the ultrasonic transmitting device 7; the outlet of the discharge pipe II 8 is located in the slurry tank III 9.

[0048] A defoaming device for lithium battery separator slurry, such as Figure 1 As shown, it includes slurry tank I1, slurry tank II 2, and the aforementioned siphon device;

[0049] The bottom inner diameter of slurry tank I1 is 40cm, the middle inner diameter is 50cm, and the height is 60cm.

[0050] The inlet of the vertical section a of the feed pipe 3 is located below the low liquid level line of the slurry tank I1, and the distance between it and the bottom of the slurry tank I1 is 2cm.

[0051] The outlet of the discharge pipe I 5 is located below the liquid level of the slurry in the slurry tank II 2, and is lower than the inlet of the vertical section a of the feed pipe 3.

[0052] A method for defoaming lithium battery separator slurry based on the above-mentioned defoaming device, such as... Figures 1-2 As shown, the lithium battery separator slurry in slurry tank I1 is transferred to slurry tank II2 using a siphon device. The specific steps are as follows:

[0053] (1) Place the vertical section a of the feed pipe 3 into the bottom of the slurry tank I1, place the outlet of the discharge pipe I 5 below the slurry liquid level in the slurry tank II 2, and place the outlet of the discharge pipe II 8 into the slurry tank III 9.

[0054] (2) Close switch I12 and open switch II 10;

[0055] (3) Squeeze the exhaust bladder II 13 to expel the gas in the pipeline. The feed pipe 3 draws slurry from the bottom of the slurry tank I1. The drawn slurry will pass through the filter box 4 and fill the filter box 4 with slurry. When slurry flows out from the discharge pipe II 8 to the slurry tank III 9, turn off the switch II 10.

[0056] (4) Open the ultrasonic transmitting device 7 and switch I12 of filter box 4, squeeze the exhaust bag I11, and when slurry flows out from the discharge pipe I 5, a siphon phenomenon is generated. The slurry will be drawn from the bottom of slurry tank I1, and after ultrasonic defoaming and filtration by filter layer 6 in filter box 4, it flows into slurry tank II 2 through discharge pipe I 5.

[0057] (5) After connecting the device according to the above steps, turn on switch II 10 and squeeze the exhaust bag II 13 to discharge the gas that has been defoamed and appears on the upper part of filter box 4.

[0058] To demonstrate the defoaming effect of this invention, comparative experiments were also conducted:

[0059] Take 40 kg of slurry from below the low liquid level line in slurry tank I and divide it into four groups, which are designated as blank group, experimental group 1, experimental group 2 and experimental group 3 respectively.

[0060] Each group performs the following operations simultaneously:

[0061] Blank group: No action is taken;

[0062] Experimental Group 1: Defoaming was performed using a chemical defoaming method. The defoamer used was an organosilicon-based defoamer. The mass ratio of the defoamer to the slurry in Experimental Group 1 was 3:100. The slurry and defoamer were mixed evenly for defoaming.

[0063] Experimental Group 2: Vacuum defoaming was used for defoaming treatment. The device used for vacuum defoaming was a battery slurry bubble elimination device disclosed in patent CN212166605U. During the defoaming process, the vacuum degree used for vacuuming the slurry was 80KPa and the vacuuming time was 30s.

[0064] Experimental Group 3: Defoaming was performed using the method of the present invention. During the defoaming process, the inner diameter of the feed pipe was 32 mm, the inner diameter of the discharge pipe I was 32 mm, the distance between the upper surface of the filter layer and the top wall of the filter box was 15 cm, the distance between the ultrasonic transmitting device and the filter layer was 2 cm, the frequency of the ultrasonic transmitting device was 20 kHz, and the mesh size of the sponge filter layer was 100 mesh.

[0065] After the above four sets of operations were completed, 5L of the treated slurry was taken out from each group. After the slurry was left to stand for 1 hour, it was weighed. The results were as follows: the blank group was 4.85kg, experimental group 1 was 4.88kg, experimental group 2 was 4.93kg, and experimental group 3 was 4.99kg. The above results show that the defoaming method of the present invention has a better defoaming effect than the prior art.

Claims

1. A method for defoaming lithium battery separator slurry, characterized in that, The lithium battery separator slurry in slurry tank I (1) is transferred to slurry tank II (2) using a siphon device; The siphon device includes a discharge pipe II (8) and a feed pipe (3), a filter box (4) and a discharge pipe I (5) connected in sequence in a closed manner. The inlet of the feed pipe (3) is located below the low liquid level line of the slurry tank I (1); The outlet of the discharge pipe I (5) is located below the liquid level of the slurry in the slurry tank II (2); The filter box (4) is located above the outlet of the feed pipe (3) and the inlet of the discharge pipe I (5); the filter box (4) is a sealed container; the filter box (4) is equipped with an ultrasonic emission device (7) for separating bubbles and slurry. The inlet of the discharge pipe II (8) is in sealed connection with the filter box (4), and the connection point is located above the ultrasonic transmitting device (7); A switch II (10) is installed on the discharge pipe II (8); The feed pipe (3) consists of a vertical section a, a bend section b, a horizontal section c, a bend section d, a vertical section e, a bend section f, a horizontal section g, a bend section h, and a vertical section i, which are connected in a closed manner from left to right. The horizontal section c is located above the vertical sections a and e, and the horizontal section g is located below the vertical sections e and i. The outlet of the vertical section i is the outlet of the feed pipe (3). The discharge pipe I (5) is arranged vertically with the inlet at the top and the outlet at the bottom. The feed pipe (3) is located to the left of the discharge pipe I (5). The discharge pipe II (8) is arranged vertically with the inlet at the top and the outlet at the bottom. The inlet of the feed pipe (3) is higher than the outlet of the discharge pipe I (5); the inner diameter of the feed pipe (3) is 20~32mm, and the inner diameter of the discharge pipe I (5) is the same as the inner diameter of the feed pipe (3); The filter box (4) is equipped with a filter layer (6) for separating air bubbles; the outlet of the feed pipe (3) and the inlet of the discharge pipe I (5) are flush with the bottom wall of the filter box (4); the distance between the upper surface of the filter layer (6) and the top wall of the filter box (4) is not less than 15cm, and the lower surface of the filter layer (6) is in contact with the bottom wall of the filter box (4); the filter layer (6) is located below the ultrasonic transmitting device (7); A section of the discharge pipe I (5) is an exhaust bladder I (11), and a switch I (12) is installed on the section between the inlet of the discharge pipe I (5) and the exhaust bladder I (11). A portion of the length of the discharge pipe II (8) is the exhaust bladder II (13), which is located above the switch II (10).

2. The defoaming method for lithium battery separator slurry according to claim 1, characterized in that, The outlet of the feed pipe (3) is at the same level as the inlet of the discharge pipe I (5).

3. The defoaming method for lithium battery separator slurry according to claim 1, characterized in that, The filter layer (6) is a sponge filter layer; the mesh size of the sponge filter layer is 80-120 mesh.

4. The defoaming method for lithium battery separator slurry according to claim 1, characterized in that, The distance between the ultrasonic transmitter (7) and the filter layer (6) is 1-2 cm, and the frequency of the ultrasonic transmitter (7) is 20±0.5KHZ.

5. The defoaming method for lithium battery separator slurry according to claim 1, characterized in that, The siphon device also includes a slurry tank III (9); the outlet of the discharge pipe II (8) is located in the slurry tank III (9).

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