Lithium battery coating machine slurry reflux homogenization buffering method and device

Abstract

This invention discloses a method and apparatus for buffering and homogenizing slurry recirculation in a lithium battery coating machine. The method includes: Step A: Installing a pulse damper on the straight pipe section at the outlet of the diaphragm pump, setting the pre-charge pressure to 60%~80% of the slurry working pressure; Step B: Setting a flow guiding structure at the recirculation port of the storage tank to allow the recirculated slurry to smoothly enter below the liquid surface; Step C: Adjusting the output frequency of the diaphragm pump according to the slurry viscosity; Step D: During commissioning, performing pressure resistance tests, pressure fluctuation verification, bubble content verification, and slurry homogenization verification to ensure that the pressure fluctuation amplitude is reduced by ≥80%, the number of bubbles with a diameter ≥50μm is reduced by ≥90%, and the relative standard deviation (RSD) of the slurry particle size distribution is ≤3%; Step E: Regularly inspecting and replenishing the pre-charge pressure during operation, and replacing the buffer membrane; Optional Step F: Dynamic adaptive adjustment. The apparatus includes a pulse damper and an anti-splatter slurry box. This invention can significantly improve coating uniformity, reduce pinhole defects, and extend equipment life.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery manufacturing technology, specifically to a method and apparatus for homogenizing and buffering slurry recirculation in lithium battery coating machines. Background Technology

[0002] In lithium battery electrode coating production, the slurry is typically pumped from the storage tank to the coating die or hopper by a diaphragm pump. Uncoated slurry is returned to the storage tank via a return pipeline, forming a closed-loop circulation system. The stability of this process directly determines the consistency of the coating thickness and the quality of the electrode.

[0003] However, existing methods have the following prominent problems: 1. Pulse fluctuations affect coating quality: The reciprocating motion of the diaphragm pump generates periodic pressure pulses, which cause drastic fluctuations in slurry flow and pressure, resulting in uneven coating thickness, longitudinal streaks, or even missed coating.

[0004] 2. Difficulty in eliminating bubbles: Pulsations and turbulence cause dissolved gases in the slurry to precipitate, forming microbubbles; simultaneously, the backflowing slurry directly impacts the surface of the storage tank, entraining a large amount of air and generating secondary bubbles. These bubbles form pinholes and voids after the electrode coating dries, severely affecting battery safety and cycle life.

[0005] 3. Slurry stratification and deterioration of particle size distribution: Pulse and turbulence disrupt the laminar flow state of the slurry, causing particles of different densities to settle or stratify, resulting in a wider particle size distribution and reduced coating consistency.

[0006] 4. High equipment wear and tear: High-frequency pulses cause vibration in pipelines and joints, accelerating the fatigue failure of vulnerable parts such as diaphragm pump diaphragm and sealing ring, and increasing the frequency of downtime maintenance.

[0007] While some production lines in the existing technology have attempted to install general-purpose pulsation dampers, there is a lack of systematic methodological guidance, resulting in the following shortcomings: 1. The damper is installed in an arbitrary position (such as near a bend), and the pre-charge pressure is not matched with the slurry working conditions; 2. No buffering treatment was performed on the return end, and secondary bubble contamination still exists; 3. Lack of coordinated control with parameters such as slurry viscosity and pump speed; 4. Lack of quantified debugging, verification, and maintenance processes.

[0008] Therefore, developing a systematic, quantifiable, and homogenous buffering method suitable for lithium battery slurry transportation is of significant necessity and engineering value. Summary of the Invention

[0009] The present invention aims to provide a homogenization buffering method for a slurry conveying system of a lithium battery coating machine, in order to solve the following technical problems: 1. Eliminate pressure pulses and flow fluctuations when diaphragm pumps deliver slurry, achieving stable material supply; 2. To suppress the generation and precipitation of bubbles in the slurry and prevent secondary bubble contamination caused by backflow impact; 3. Maintain the homogeneity of the slurry and prevent stratification and deterioration of particle size distribution; 4. Reduce pipeline vibration, extend the life of vulnerable parts of equipment, and reduce downtime for maintenance; 5. Establish a set of standardized process methods that can be quantified, verified, and replicated.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a method and apparatus for homogenizing and buffering slurry recirculation in a lithium battery coating machine.

[0011] The method of this invention adopts a technical approach of "source pulse suppression + pipeline flow stabilization control + backflow impact protection + parameter quantization matching + dynamic maintenance", and includes the following core steps: Method and steps: Step A: Pulse damper installation and pre-charge pressure setting Install a pulse damper in the straight pipe section within 1 meter of the diaphragm pump outlet (existing technology, generally using diaphragm type or airbag structure). Based on the working pressure of the slurry P_work, set the damper pre-charge pressure P_pre = (60%~80%) × P_work; Nitrogen is used for pre-filling to ensure stable pressure and prevent it from reacting with the slurry.

[0012] Step B: Anti-impact flow guiding setting for return port A flow guiding structure (such as an inclined flow guide plate, a porous dispersion box, or a downward extension pipe) is installed at the reflux port of the storage tank to allow the refluxed slurry to flow smoothly into the liquid surface below the liquid level along the tank wall or the flow guiding surface. Avoid direct impact of slurry on the liquid surface to prevent secondary air bubbles from being drawn in due to splashing and violent agitation.

[0013] Step C: Adjusting the slurry viscosity to match the pump speed Measure the viscosity η of the currently conveyed slurry (e.g., the viscosity range of positive electrode slurry is 20.0~300.0 mPa·s). Adjust the reciprocating frequency of the diaphragm pump according to the viscosity to stabilize the pump output flow and work in conjunction with the damper. Matching relationship: When the viscosity is ≥100 mPa·s, the pump frequency is ≤1.2 Hz; when the viscosity is <100 mPa·s, the pump frequency is ≤1.8 Hz.

[0014] Step D: System debugging and quantitative verification Pressure resistance test: Slowly increase the pressure to the working pressure P_work, hold the pressure for 5 to 10 minutes, and check the pipeline and damper sealing connection points for leaks; Pressure fluctuation verification: Run the diaphragm pump and measure the pump outlet pressure fluctuation amplitude. The required pressure fluctuation amplitude should be reduced by ≥80% compared to when the method of this invention is not used. Bubble content verification: Samples were taken downstream of the damper to test the size and number of bubbles in the slurry. The number of bubbles with a diameter ≥50μm was required to be reduced by ≥90%. Slurry homogeneity verification: Take slurry samples and test the particle size distribution. The relative standard deviation (RSD) should be ≤3% and there should be no visible layering. Vibration verification: Measure the vibration acceleration at key points of the pipeline, requiring a reduction in vibration amplitude of ≥60%.

[0015] Step E: Dynamic Maintenance and Stress Compensation Inspect the damper seal every 24 hours and check the pre-charge pressure. If it is lower than the set value, pressurize it. Replace the damper diaphragm every 3 to 6 months or when a significant decrease in pulse absorption capacity is observed (e.g., pressure fluctuations exceed 1.5 times the initial value). Each time the machine is shut down for cleaning, the damper cavity and the return flow guide structure are thoroughly cleaned to remove any slurry residue.

[0016] Step F: Adaptive adjustment under abnormal operating conditions (optional) The system monitors pump outlet pressure fluctuations in real time. When the fluctuation amplitude exceeds the set threshold, it automatically fine-tunes the damper pre-charge pressure or diaphragm pump frequency to quickly restore the system to a stable state.

[0017] Device: A homogenizing buffer device for a lithium battery coating machine slurry conveying system for implementing the above method, comprising: Pulse damper: Installed in the outlet pipeline of the diaphragm pump, it is equipped with an FKM fluororubber buffer membrane inside to absorb pressure pulses and suppress bubble precipitation; Anti-splash material box: Installed at the return port of the storage tank, it guides the return slurry to enter the liquid surface smoothly and eliminates secondary bubble contamination. Compared with the prior art, the beneficial effects of the present invention are: 1. Significantly improved coating quality: pressure fluctuation amplitude reduced by ≥80%, coating thickness variation controlled within ±1.5μm, and electrode pinhole rate reduced from above 3% to below 0.5%.

[0018] 2. Significantly reduced bubble content: The number of ≥50μm bubbles is reduced by ≥90%, significantly reducing the risk of electrode voids and short circuits.

[0019] 3. Maintaining slurry homogeneity: Particle size distribution RSD ≤ 3%, with no stratification during long-term circulating transport.

[0020] 4. Elimination of backflow impact: Through the flow guiding structure, secondary bubble contamination is basically eliminated, and the purity of the slurry is improved.

[0021] 5. Extended equipment lifespan: Pipeline vibration is reduced by ≥60%, and the replacement cycle of vulnerable parts of diaphragm pumps is extended by more than 30%.

[0022] 6. Improved production efficiency: The frequency of downtime for adjustment in the coating process is reduced by more than 70%, the effective production time of a single line is increased by ≥10%, and the overall operation and maintenance cost is reduced by 4%~6%. Attached Figure Description

[0023] Figure 1 The present invention provides a process flow for the slurry recirculation homogenization and buffering method for lithium battery coating machines. Figure 1 ; Figure 2 The present invention provides a process flow for the slurry recirculation homogenization and buffering method for lithium battery coating machines. Figure 2 ; Figure 3 The present invention provides a process flow for the slurry recirculation homogenization and buffering method for lithium battery coating machines. Figure 3 ; Figure 4 The present invention provides a process flow for the slurry recirculation homogenization and buffering method for lithium battery coating machines. Figure 4 ; Figure 5 This is a logic diagram of the lithium battery coating machine slurry recirculation homogenization buffering method and device of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] System Working Process Overview During coating machine operation, the diaphragm pump pumps the slurry from the storage tank, which is then regulated by a pulse damper and delivered to the coating die. Uncoated slurry returns to the storage tank via a return pipeline and smoothly enters the liquid surface through the return port guide structure, completing the circulation. When the pump starts or operating conditions change, the damper absorbs the pulse, and the pre-charge pressure is preset according to the working pressure; simultaneously, the pump speed is adjusted according to the slurry viscosity to ensure stable delivery. Commissioning and maintenance are performed according to steps D and E. Optional step F allows for automatic adjustment in case of sudden changes in operating conditions.

[0026] Example 1: Homogenization and buffering method for NCM ternary cathode slurry delivery Operating parameters: Slurry type: NCM622 cathode slurry, solid content 68%. Viscosity: 120.0 mPa·s (25℃) Diaphragm pump operating pressure: 1.5 MPa Coating speed: 25 m / min Implementation steps: Preliminary preparations: Confirm that the damper has a pressure resistance of ≥2.0 MPa and that the interface size matches the pipeline; prepare tools such as nitrogen cylinders, pressure gauges, and torque wrenches. Turn off the diaphragm pump, drain any residual slurry from the pipeline, and clean the pipeline interfaces.

[0027] Damper Installation and Pre-charge (Step A): Install a diaphragm-type pulse damper in series 0.8 meters from the diaphragm pump outlet (straight pipe section, no bends). Calculate the pre-charge pressure: P_pre = 70% × 1.5 MPa = 1.05 MPa, and set it to 1.05 MPa (using nitrogen for pre-charge). Connect the damper to the pipeline using quick-connect clamps to ensure a seal.

[0028] Return port guide setting (step B): Weld a stainless steel guide plate inclined downward at 45° at the return port of the storage tank, with the end of the guide plate extending approximately 50mm below the liquid surface. Ensure that the return slurry flows smoothly along the plate surface without impacting the liquid surface.

[0029] Pump speed matching adjustment (step C): Initially set the diaphragm pump frequency to 1.2 Hz (rated maximum 2.0 Hz), corresponding to a flow rate of approximately 18 L / min. Observe the pump outlet pressure gauge; the pressure fluctuation range is approximately ±0.12 MPa (±0.45 MPa before installing the damper), which meets the requirements.

[0030] Debugging and verification (Step D): Slowly open the valve, increase the pressure to 1.5 MPa, maintain the pressure for 5 minutes, and check for leaks at all connections.

[0031] Start the diaphragm pump and run it continuously for 30 minutes, recording the data: Pressure fluctuation range: ±0.08 MPa (reduced by 82.2%); Bubble sampling and detection: The bubble analyzer showed that the number of bubbles ≥50μm decreased from 180 bubbles / mL to 15 bubbles / mL (a decrease of 91.7%). The particle size analyzer showed an RSD of 2.8%, with no stratification. The vibration sensor showed that the pipeline acceleration decreased from 0.25g to 0.09g (a decrease of 64%).

[0032] Coating verification: After the coating machine ran for 2 hours, the transverse thickness difference of the electrode was ±1.2μm and the pinhole rate was 0.2%.

[0033] Maintenance Plan (Step E): Inspect the damper seal and pressure gauge readings daily, and record the pre-charge pressure.

[0034] Replace the damper diaphragm every 4 months (as a preventative measure, even if it is not damaged).

[0035] Each time production is stopped for more than 8 hours, the damper cavity and return flow guide plate are cleaned with solvent.

[0036] Example 2: Method for use in low-viscosity negative electrode slurry (high solids graphite system) Operating parameters: Slurry type: Graphite anode slurry, solid content 52%. Viscosity: 45.0 mPa·s Working pressure: 1.1 MPa Coating speed: 35 m / min Implementation steps: Step A: The damper is installed in the 0.5-meter straight pipe section at the pump outlet. The pre-charge pressure P_pre = 65% × 1.1 = 0.715 MPa, and we take 0.72 MPa.

[0037] Step B: Use a porous dispersion box (with small holes around the box). The reflux slurry first enters the box and then disperses into the liquid surface through the small holes to avoid direct impact.

[0038] Step C: Set the diaphragm pump frequency to 1.6 Hz.

[0039] Step D Verification Result: The pressure fluctuation range decreased from ±0.30 MPa to ±0.05 MPa (a reduction of 83.3%). The number of bubbles ≥50μm decreased from 210 bubbles / mL to 12 bubbles / mL (a reduction of 94.3%). Particle size RSD = 2.5%; The coating thickness range is ±1.3μm, and the pinhole rate is 0.15%. The diaphragm replacement cycle for diaphragm pumps has been extended from 3 months to 4.5 months.

[0040] Coating effect: The electrode is free of pinholes, and the coating thickness CPK value is increased from 0.9 to 1.35.

[0041] Example 3: Dynamic Adaptive Adjustment (Step F) Add closed-loop control based on Example 1: A pressure sensor is installed at the outlet of the damper to collect the pressure fluctuation amplitude in real time. When the fluctuation amplitude exceeds ±0.10 MPa, the controller fine-tunes the damper chamber pressure via the solenoid valve (increasing or decreasing by 0.02~0.05 MPa). Simultaneously, the speed of the diaphragm pump motor is adjusted (frequency fine-tuning ±0.1 Hz); The system can restore fluctuations to within ±0.08 MPa within 30 seconds, adapting to disturbances caused by sudden changes in coating speed (such as a step from 25 m / min to 35 m / min).

[0042]

Claims

1. A homogenization buffering method for a slurry conveying system in a lithium battery coating machine, characterized in that, Includes the following steps: Step A: Install a pulse damper on the straight pipe section at the outlet of the diaphragm pump, and set the damper pre-charge pressure P_pre = (60%~80%) × P_work according to the slurry working pressure P_work. Step B: Install a flow guiding structure at the return port of the storage tank to ensure that the returned slurry enters smoothly below the liquid surface and avoids direct impact on the liquid surface; Step C: Adjust the output frequency of the diaphragm pump according to the viscosity of the slurry to stabilize the pumping flow rate and work in conjunction with the damper; Step D: During system commissioning, pressure resistance tests, pressure fluctuation verification, bubble content verification, and slurry homogeneity verification are performed to ensure that the pressure fluctuation amplitude is reduced by ≥80% compared to when the method of this invention is not used, the number of bubbles with a diameter ≥50μm is reduced by ≥90%, and the relative standard deviation (RSD) of the slurry particle size distribution is ≤3%. Step E: During operation, periodically check the pre-charge pressure of the damper and replenish the pressure, and replace the buffer diaphragm if necessary.

2. The homogenization and buffering method for the slurry conveying system of a lithium battery coating machine according to claim 1, characterized in that, In step A, the pulse damper is installed in a straight pipe section within 1 meter of the diaphragm pump outlet, and is far away from turbulent areas such as bends and tees.

3. The homogenization buffering method for the slurry conveying system of a lithium battery coating machine according to claim 1, characterized in that, The flow guiding structure in step B is at least one of the following: an inclined flow guide plate, a porous dispersion box, or a downward extension tube.

4. The homogenization and buffering method for the slurry conveying system of a lithium battery coating machine according to claim 1, characterized in that, In step C, the matching relationship between slurry viscosity and diaphragm pump frequency is as follows: when viscosity ≥ 100 mPa·s, pump frequency ≤ 1.2 Hz; when viscosity < 100 mPa·s, pump frequency ≤ 1.8 Hz.

5. The homogenization buffering method for the slurry conveying system of a lithium battery coating machine according to claim 1, characterized in that, In step D, the pressure test involves pressurizing to P_work and holding the pressure for 5-10 minutes, with no leakage in the pipeline.

6. The homogenization buffering method for the slurry conveying system of a lithium battery coating machine according to claim 1, characterized in that, In step E, the damper precharge pressure inspection cycle is once every 24 hours, and the buffer membrane replacement cycle is 3 to 6 months or when the pressure fluctuation exceeds 1.5 times the initial value.

7. The homogenization buffering method for the slurry conveying system of a lithium battery coating machine according to claim 1, characterized in that, It also includes step F: real-time monitoring of pump outlet pressure fluctuations, and when the fluctuation amplitude exceeds the set threshold, automatically fine-tuning the damper pre-charge pressure or diaphragm pump frequency to achieve dynamic adaptive pressure stabilization.

8. A homogenizing buffer device for a lithium battery coating machine slurry conveying system used to implement the homogenizing buffering method of the lithium battery coating machine slurry conveying system according to any one of claims 1-7, characterized in that, include: The pulse damper is installed in the outlet pipeline of the diaphragm pump. It has an FKM fluororubber buffer membrane inside to absorb pressure pulses and suppress bubble precipitation. The anti-splash material box is installed at the return port of the storage tank to guide the return slurry smoothly into the liquid surface and eliminate secondary bubble contamination.

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