In 2024, China’s production and sales of new energy vehicles (NEVs) reached 12.888 million and 12.866 million units respectively, marking a year-on-year growth of 34.4% and 35.5%. With the increasing penetration of electric vehicles globally, the demand for lithium batteries has surged.

During lithium battery production, the electrode coating process is one of the critical stages, with the drying process accounting for a significant portion of energy consumption (approximately 50%-70% of the total energy usage in electrode manufacturing). Therefore, optimizing energy consumption in the drying process of lithium battery electrode coating has become a key factor in reducing costs and improving efficiency across the industry chain.

Lithium Battery Manufacturing Process

Coating Process

The substrate passes through the unwinding mechanism, and the die evenly applies the slurry onto the substrate. After drying, high temperatures remove the moisture from the electrode sheet. As a critical step in the coating process, the effectiveness of the baking directly impacts the quality of lithium battery products.

The traditional oven heating solution has many drawbacks

The conventional electrode drying process uses oven heating, where heated air evaporates the solvent through convection. However, this convection drying method has several pain points:

• Low Energy Utilization: Traditional hot air drying relies on convective heat transfer, which has low thermal efficiency. This issue is exacerbated as coating thickness increases, limiting the diffusion rate of internal solvents and prolonging drying time.

• Low Production Efficiency: Differences in solvent evaporation rates between the coating surface and interior can cause surface cracking, binder migration, or uneven porosity, negatively impacting battery performance (e.g., ion conductivity, adhesion strength) and reducing production efficiency.

• Difficult Maintenance: Organic solvents like NMP require condensation recovery, which involves high energy consumption and complex maintenance for recovery equipment.

• Large Equipment Footprint: Traditional ovens are bulky, with uneven heat distribution that further aggravates energy consumption issues.

Laser Heating Drying Solution

The use of direct diode lasers combined with large-format rectangular spot lenses to replace traditional convection drying can effectively address these issues!

direct diode lasers combined with large-format rectangular spot lenses

• High Production Efficiency: After homogenizing and shaping, the laser directly irradiates the electrode sheet, drying the solvent in the slurry in an extremely short time.

• High Energy Utilization: Direct diode lasers have an electro-optical conversion efficiency of over 55%, offering high energy utilization and greater energy savings.

• Compact Equipment Footprint: The equipment has a small footprint, effectively saving factory space.

• Simple Operation and Maintenance: The laser can be turned on and off as needed, allowing for easy maintenance without the need for preheating when powered on.

Practical Application Case

In lithium battery drying, using laser drying to directly replace oven convection drying yields good results, but the cost is relatively high. In practical applications, a hybrid method of laser drying + oven convection drying is often used. This involves retrofitting existing production equipment to achieve cost reduction and efficiency improvement. For example, in the case of an existing 70-meter oven convection drying production line:

Hybrid Laser Drying Process

After retrofitting the original production line, the hybrid laser drying process can reduce the battery electrode drying operation costs (including labor maintenance, etc.) by nearly 30%. The hybrid laser drying process can also reduce the footprint of the battery electrode drying process by almost 50% (for the same output).

Due to the low equipment footprint and efficient energy input (energy consumption) of the laser-based drying system, approximately 20% of capital expenditure can be saved. By integrating large-area and uniform direct diode laser spot patterns, the quality of electrode drying can be improved.

Laser Heating: Broad Industry Application Prospects

In addition to the new energy industry, high-power laser heating/drying offers significant advantages such as high efficiency, low energy consumption, high space utilization, precise control, and uniform heating. These advantages present enormous application potential and market opportunities in various industries, including aerospace, coating, and textiles.

Aerospace Industry

With the advent of the industrial lightweight era, industries like aerospace and automotive are increasingly turning to high-stability, high-strength, and lighter composite materials as the preferred choice for manufacturing product components. Among these, the use of thermoplastic composites has become a major trend in the aerospace industry's lightweight movement.

Laser heating technology can play a critical role in efficiently processing these advanced materials, offering high precision in curing and shaping, which is essential for manufacturing aerospace components with optimized performance and minimal weight.

High-Performance Thermoplastic Prepreg Drying: The carbon fiber reinforced thermoplastic prepreg production line mainly consists of the following components: unwinding device, impregnation device, drying device, and winding device.

• Unwinding Device: Responsible for unrolling the carbon fiber fabric.

• Impregnation Device: Uniformly applies thermoplastic resin onto the carbon fiber fabric.

• Drying Device: Uses methods such as laser heating/drying to evaporate the solvent from the prepreg material.

• Winding Device: Rolls up the finished prepreg material.

These devices work in coordination to achieve the efficient production of carbon fiber thermoplastic prepreg.

Stamping Forming Preheating: In the stamping forming of thermoplastic composites, issues such as high preheating temperatures and uneven heating inside and outside the material often arise. Laser heating, with its high energy density and excellent heating uniformity, can address these issues. The laser heating system, when combined with temperature sensors and PID control, enables constant surface temperature heating, ensuring uniform heating of both the inner and outer layers of the material.

Coating and Textile Industry

The drying of paints, fabrics, paper, and other materials can fully leverage the advantages of laser technology. Due to the strong penetrability of lasers, they can effectively penetrate into the drying material, enabling drying from the inner layers to the outer layers. The matching of the laser wavelength allows for the evaporation of moisture and solvents from within the material first, resulting in better drying effects. This method can significantly improve the surface quality of paints and fabrics, ensuring more uniform drying and enhanced product finish.

A wide range of products is available to enhance laser heating, improving both quality and efficiency

To meet the demand for laser heating, Everbright has launched a series of 12KW, 20KW, and 32KW direct diode laser products, equipped with matching optical lenses. These lasers provide uniform heating, offering high efficiency, low energy consumption, high space utilization, precise control, and even heating. This product range is designed to enhance laser heating, improving both quality and efficiency, helping manufacturers optimize their processes and achieve better results.