Control method and system for improving density consistency of coating surface

Abstract

According to the method, the slurry can be accurately and stably supplied during coating, and the problem that the ground coating material is uneven due to fluctuation such as slurry deposition is solved. According to the method, the dressing coated on the base material is ensured to be stable and unchanged from the source from real-time detection of the density of the slurry and control of the volume of the supplied slurry (through pump speed control). And the purpose of high consistency is achieved.

Description

Technical Field

[0001] Lithium-ion battery production and suspension coating production industries. Background Art

[0002] With the rapid development of lithium batteries, the market has higher and higher requirements for lithium batteries, especially cycle life and safety (especially when used in series and parallel). To achieve this goal, there are extremely high requirements for the consistency of the electrode coating of lithium batteries (usually expressed by surface density). Whether it is 3C, power or energy storage, the entire lithium battery industry must improve and break through.

[0003] The existing lithium battery coating control is too simple and extensive. To adjust the appropriate surface density, employees have to modify the coating parameters (such as the number of pumps) over and over again, which requires high skills of employees. It wastes a lot of materials and has a great impact on production efficiency.

[0004] As the slurry is deposited in the tank to varying degrees during the coating process, the same coating parameters will cause the amount of coating to change, that is, the consistency is greatly affected, the pole piece specifications deviate more and more, and ultimately the battery's electrical performance and safety performance are seriously affected. Although there is a β-ray surface density inspection instrument, it can only inspect the dry film. It is too late to inspect after drying, and it cannot be adjusted in time and accurately, and the screw pump speed cannot be accurately adjusted to cope with fluctuations.

[0005] This patent adopts a new coating control method and system to fundamentally solve these problems, improve the consistency of coating surface density and achieve continuous and stable production. Summary of the invention

[0006] The present invention ensures that the slurry is evenly coated on the copper-aluminum foil current collector or other base film through stable quantitative feeding, and does not fluctuate with the fluctuation of the slurry, thereby achieving consistency of the pole piece. The details are as follows: Stable quantitative feed volume W (i.e. W standard) = ρ (slurry density monitored in real time) × V (feed volume updated in real time by the screw pump) × slurry solid content (%, measured when the slurry is shipped).

[0007] W standard = ρ surface density (surface density required by design) × coating speed (m / min) × film width (film width required by design) ρ The slurry density is provided in real time by an online density tester.

[0008] VThe feeding volume updated in real time by the screw pump = screw pump speed × one-way volume of the screw pump (different screw pump models have been determined). Due to pressure reasons, the one-way volume of the screw pump may change slightly. You can make a slight adjustment based on the above calculation results, or collect one-way volume data according to different pressures for correction.

[0009] The required screw pump speed can be inferred from the W standard and slurry density and can be input.

[0010] ρ (slurry density) and V (screw pump feeding volume) are updated in real time to ensure that the value of W = ρ × V × solid content percentage remains unchanged. That is, it is ultimately achieved by monitoring the changes in slurry density to adjust the speed of the screw pump.

[0011] This screw pump can be realized by manually inputting on the coating control panel, or by modifying the coating PLC program, reading relevant data, and calculating and automatically updating the screw pump speed on the coating control panel.

[0012] This method can achieve accurate and stable slurry supply during coating, and solve the problem of uneven coating caused by fluctuations such as slurry deposition. This method ensures that the dressing applied to the substrate is stable from the source through real-time detection of slurry density and control of slurry volume supplied (through pump speed control), achieving the goal of high consistency.

[0013] The control method is simple. It can be realized by directly inputting a single control parameter (screw pump speed) after reading relevant data and calculating. It can also be directly modified on the original coating PLC program to achieve automatic calculation and automatic update on the control panel.

[0014] The existing coating control methods and systems can only achieve a COV of 0.3%-0.5%, with large fluctuations and poor consistency. This method can control the COV within 0.2%.

[0015] The existing coating control method and system need to be debugged to a stable state, and the parameters need to be tried and revised over and over again (the key is the screw pump speed), which is wasteful and the pole piece is scrapped ~0.5%-2.0%. This method can quickly adjust to the required surface density range. The pole piece scrap can be controlled within 0.5%. Based on the calculation of ordinary square shell LFP280AH lithium battery, 1GWh can save more than 50 million per year. The existing coating control methods and systems are highly dependent on the skills of employees, with long employee training cycles, heavy workloads, and poor stability. It is necessary to reserve skilled personnel, and the overall labor cost is high. 1GWh has two coating machines for positive and negative electrodes, and two shifts require 16 people, with an annual pure labor cost of ~960,000 (excluding other training and reserve period costs). This method only requires half of the original staff, that is, the labor cost is only half of the original, and in the later stage, it can also achieve one person multiple machines (1 / 3 of the original labor).

[0016] In addition to being suitable for lithium battery coating, this method and control system are also applicable to suspension slurry coating in other industries.

[0017] Use case: Taking the production of lithium iron phosphate energy storage battery 305AH as an example, the pole piece surface density is 15g / cm2, the coating film width is 580mm, the coating speed is 45 m / min, the screw pump unidirectional volume is 0.3L, the slurry density is 15.17kg / m3, and the slurry solid content is 73%. So to achieve, the calculation is as follows: S pump speed = 15*0.58*2*45 / (0.3*15*73%) = 283rpm The one-way volume will change slightly with the pressure. The actual slurry volume of 5-10S can be collected for correction. After correction, the one-way volume will be slightly larger than the screw pump specification. After correction, the one-way volume of this example is 0.302L, and the screw pump speed is corrected to 281rpm.

[0018] This data can be directly input into the screw pump number of the coating control panel. The COV result is 0.14%, which is much higher than the original method's 0.39%. It takes 14 minutes to adjust once, while the original method took 68 minutes. Description of the drawings: Figure 1 】 is a system schematic diagram.

Claims

1. A method of using a density-controlled volume pump to provide a stable quantitative feed (solid matter in a suspension); 2. A method for obtaining a final accurate and real-time updated screw pump speed based on the coating surface density target value and coating speed, film width, and measured slurry density and solid content.

3. A stable feeding system consisting of an online slurry density detector, a screw pump, a pressure detector, etc.

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