Overview of process optimization
Heated coaters play a key role in the preparation of lithium battery electrodes. By precisely controlling the coating process of the slurry on the metal foil, a uniform coating is achieved. The optimization of this process involves several parameters, including temperature, speed, and coating thickness. Based on domestic and foreign standards and technical discussions, this paper analyzes the process adjustment method of heating coating machine in electrode preparation.
Temperature control adjustment
Temperature is the core parameter of the heating coating machine. The electrode paste is composed of active materials, conductive agents, and binders, and its solvent evaporation rate is directly regulated by temperature. Too low temperature leads to solvent residue and insufficient bonding strength; Too high a temperature can cause the adhesive to break down or crack form. According to relevant research, it is recommended to set the temperature zone of the oven: the first section is about 80°C to gradually remove the solvent, and the back section is increased to 110°C to complete drying. This gradient design helps reduce stress inside the coating.
Coating speed optimization
The coating speed affects the coating thickness and surface morphology. When the speed is too fast, the slurry flow is unstable and easy to produce streaks; Too slow speed reduces production capacity. In experimental debugging, it is key to select a specific combination of gap gap and pump speed according to the viscosity and solids content of the slurry. The typical method is to adjust the 2% increment at a starting speed of 2-5 m/min to observe the uniformity of the coating surface. When the diaphragm density deviation is less than 1.5%, the velocity is a reasonable value.
Coating thickness management
The single-sided coating thickness needs to match the battery energy density and cycle life. Gap coating reduces material waste while keeping edge effects in mind. Table 1 lists the commonly used thickness ranges and corresponding adjustment methods.
| Thickness range (microns) | Adjustment method |
| 50-80 | Reduce clearance clearance or reduce pump speed |
| 80-120 | Increase coating speed or increase solids content |
| 120-160 | Multiple coating methods are used |
Uniformity improvement measures
The uniformity of the electrode coating directly impacts charge distribution and longevity. Consistency can be improved by adjusting the squeegee-to-substrate spacing and monitoring it in real-time with a laser thickness gauge. In addition, the slurry needs to be well dispersed to avoid agglomeration. Vacuum defoaming eliminates air bubbles and reduces coating pinholes. Equation (1) describes the relationship between the thickness of the coating wet film and the slurry density ρ and porosity ε.
h = m / (ρ × (1-ε) × A) (1)
where h is the thickness of the wet film, m is the mass of the active substance, and A is the coating area. With the help of the online monitoring system, the operator can correct the parameters in a timely manner.
Drying curve setting
The drying curve needs to be designed according to the solvent boiling point and heat capacity. If the heating rate is too fast, the solvent evaporates rapidly on the surface, forming a dense layer that hinders internal diffusion and causes air to be hollowed. Multi-stage setting is recommended: maintain a constant temperature for the first 15 seconds, then rise to the target value at a rate of 5°C per minute. This curve has been verified from the relevant technical literature and helps to reduce coating stress.
Summary
The efficiency of the heated coater in electrode preparation is ensured by fine adjustment of temperature, speed and thickness. The above optimization measures are applicable to common slurry systems based on existing standards and experimental data. In the future, it can be combined with an online data feedback system to achieve adaptive process adjustment.
References:
1. Research on Uniformity of Lithium Battery Pole Coating, Chemical Engineering and Technology, 2021, Vol. 42, No. 3.
2. Analysis of the influence of coating process parameters on electrode structure, Power Supply Technology, 2022, Vol. 36, No. 7.
3. Simulation and Optimization of Electrode Drying Process, Journal of Mechanical Engineering, 2020, Vol. 56, No. 15.