Performance: Air bubbles in the coating, forming holes after drying.

Cause: The slurry is not degassed, the coating speed is too fast, and the viscosity is abnormal.

Solution:

* Vacuum degassing -0.095MPa (absolute pressure 5kPa), 30 minutes, stirring speed 60rpm, Higher vacuum degassing is more thorough. Add Polyether defoamers should choose models with a silicon content < 0.1%, Avoid silicon residue affecting battery performance.

* Reduce the coating speed to 2-5mm/s to avoid turbulent air entrainment, and let the degassed slurry stand for 10 minutes before use.

Performance: Surface particles protrude or foreign matter.

Cause: The slurry is not filtered clean, environmental dust pollution, equipment wear.

Solution:

* Ultrasonic cleaning of the container (40kHz, 15 minutes), install a 200-mesh online filter on the feed pipe, and replace the filter membrane before the experiment.

* Maintain a Class 10,000 cleanroom in the laboratory (wind speed 0.35m/s), personnel wear dust-proof clothing, and equipment is cleaned regularly.

Performance: Concave-convex wavy texture.

Cause: Low viscosity/fast solvent evaporation, coating too thick, uneven drying.

Solution:

* Increase the slurry viscosity to 3000-3500cps (add 0.3-0.8% HPMC, excessive amount will cause the slurry viscosity to be too high, affecting fluidity), the single-pass coating wet thickness is recommended <180μm, adjust according to the slurry solid content, high solid content slurry needs to be thinner.

* Reduce the inlet temperature of the drying oven by 5-10℃, extend the constant-rate drying stage, and apply the coating twice to achieve the target thickness.

Performance: Cracks inside or at the interface of the coating.

Cause: Poor material compatibility, coating too thick, insufficient ductility of the current collector.

Solution:

Adjust the formula ratio (e.g., increase the conductive agent by 2%), anneal the current collector (300℃, 1 hour), or replace the nickel strip.

Use gradient coating, add a 5-8% soft carbon buffer layer to the bottom layer; too much will significantly reduce the electrode capacity. Single coating wet thickness, NCM system <150μm, LFP system can be relaxed to 180μm.

Performance: Deviates from the design thickness (too thick/thin).

Cause: Incorrect coating head gap, fluctuation in solid content, inaccurate feed rate.

Solution:

Calibrate the coating head gap using the three-point method (left, middle, and right errors < ±5μm), and control the solid content at 50±2% (solvent adjustment ±2%).

Use a laser thickness gauge for closed-loop control, and adjust the feed pump speed in real time (accuracy ±1rpm).

Performance: The coating width is asymmetrical left and right.

Cause: Coating head offset, current collector skew, slurry overflow.

Solution:

Calibrate the coating head position using a photoelectric centering sensor (error <0.1mm), and install baffles on both sides (2-3mm from the edge of the foil).

Adjust the synchronization of the twin-screw feeder speed (difference <0.5rpm), and check the width with a ruler for the first piece (target deviation <0.5mm).

Performance: Irregular cracks after drying.

Cause: Drying rate is too fast, insufficient binder, coating is too thick.

Solution:

Multi-stage gradient drying (40℃→60℃→80℃, total time 120 minutes), add 0.5-1% glycerin plasticizer.

Control the wet thickness of the coating below 150μm, and use a core-shell structure binder (such as SBR@PAA) to enhance flexibility.

Performance: Sticky or solvent odor after drying.

Cause: Insufficient temperature/time, poor ventilation, high solvent boiling point.

Solution:

The drying temperature should be 15-20℃ higher than the solvent boiling point, For example, the boiling point of NMP is 202℃, and the temperature at the tail of the drying oven should be set to 215-220℃. Increase the air exchange frequency to 15 times/hour.

Use vacuum drying -0.09MPa, 120℃, 120 minutes (The boiling point of NMP is reduced to about 150℃ under vacuum), or replace the low-boiling point mixed solvent (such as NMP: ethanol = 7:3).

Performance: Irregular wave patterns or thickness fluctuations.

Solution: The equipment base bolt torque reaches 15N・m, add rubber vibration isolation pads (natural frequency <5Hz), and gear clearance <0.1mm.

Solution: Add 0.3-0.5% bentonite, high-speed shear dispersion (1500rpm, 20 minutes), and reduce the coater speed to 20rpm to match the viscosity.

Solution: Low-speed stirring (50 rpm) with a double-planetary mixer + bottom baffle plate, reversing every 20 minutes. The conductive agent is pre-dispersed into a 15-20% solid content liquid.

Solution: Solvent and binder polarity matching (NMP for PVDF, water-based for CMC/SBR), surface coating of active materials with 0.5-1% Al₂O₃, PVDF (non-polar) for NMP systems, CMC/SBR (polar) for water-based systems.

Solution: Add 3-5% Polyethylene glycol (PEG) pore former Calcine at 600℃ to remove, PEG decomposes without residue. Extend vacuum degassing time to 45 minutes (stirring speed 80 rpm).

Solution: Three-roll mill cycle grinding 3 times (D50 <5μm), add 0.5-1% sodium polyacrylate dispersant, ultrasonic dispersion for 10 minutes.

Solution: Dry the bottom layer to a moisture content <1% (gravimetric method), consistent solvent system for both layers, interval time <1 hour.

Solution: Sandblast the tab surface (Ra 3-5μm), reduce the speed to 1 mm/s 5 cm before the tab during manual coating, and use a mechanical baffle plate to block.

Solution: The flow rate error of the multi-channel feeding system is <±0.5%, and the PLC program sets a gradient curve (e.g., the active material decreases from 80% to 50% within 10 cm).

Solution: Laboratory temperature control 23±0.5℃, humidity 25±2% RH, hygroscopic slurry operation in glove box (humidity <1% RH).

Solution: Equipment grounding resistance <1Ω, install ion wind bar (±5kV, 10cm away from foil), environmental humidity control by scenario, 40-50% RH for non-hygroscopic systems, <1% RH for hygroscopic systems (such as LTO) 。