Laser cleaning is known as "the most potential green cleaning technology in the 21st century". It can change the grain structure and orientation of the substrate surface without damaging the substrate surface, and control the surface roughness of the substrate, thus enhancing the comprehensive performance of the substrate surface. With the accelerated industrialization process and the steady progress of the "double carbon" goal, it has gradually replaced the traditional cleaning process in many fields and gradually become an indispensable equipment manufacturing technology in high-end manufacturing fields such as industry, military, shipbuilding, aerospace, etc.

The concept of laser cleaning originated in the mid-1980s. Its principle is to make use of the characteristics of the laser beam, such as large energy density, controllable direction and strong convergence ability, to make the laser interact with the pollutants attached to the workpiece substrate, such as oil, rust, dust residue, coating, oxide layer or film layer, and separate from the workpiece substrate in the form of instant thermal expansion, melting, gas volatilization, etc.

The whole laser cleaning process is complicated, which can be roughly divided into laser gasification decomposition, laser dissection, thermal expansion of pollutant particles, matrix surface vibration and pollutant separation. At present, there are laser ablation cleaning methods, liquid film assisted laser cleaning methods and laser shock wave cleaning methods, which can stably and effectively clean various regular substrate surfaces, including metals, alloys, glasses and various composite materials.

Compared with the traditional cleaning methods of chemical cleaning and mechanical grinding, laser cleaning technology has obvious advantages. First of all, from the perspective of cleaning methods, laser cleaning technology belongs to non-contact technology, while the other two methods will have direct contact with the cleaned materials, so the latter two methods will cause damage to the workpiece. In addition, laser cleaning has high efficiency, good cleaning effect and high cleaning accuracy. It can be used only with power on and will not pollute the environment. However, the chemical cleaning and mechanical grinding methods are inefficient, the cleaning effect is general and uneven, and will also cause pollution to the environment. In addition, the laser cleaning technology is simple to operate and can also realize automation. Although the initial investment cost is high, there are no consumables and the later maintenance cost is low. However, the chemical cleaning method has complex operation process and high operation requirements, and pollution prevention measures should be taken. Although the initial input cost is low, the cost of consumables is very high. Mechanical grinding is time-consuming and labor-intensive, and pollution prevention measures should also be taken. At the same time, the cost of first investment is high, and the cost of consumables and labor is also high.

At present, laser cleaning has become the main means of battery surface treatment, and is widely used in three main power battery production processes, namely, pole sheet manufacturing, cell manufacturing and battery assembly. By using laser, cleaning head and control software, and computer integrated control, the battery manufacturing process level is greatly improved.

1. Pole piece laser cleaning

When the positive and negative collectors are coating electrode materials, the metal ribbon needs to be cleaned. The common positive collector is aluminum foil, and the negative collector is copper foil. In order to ensure the stability of the collector in the battery, the purity of the two is required to be above 98%.

Traditional wet ethanol cleaning is easy to damage other parts of lithium battery. Laser cleaning of metal foil can not only improve the efficiency of cleaning process and save cleaning resources, but also establish real-time monitoring of cleaning process data and quantitative judgment of cleaning results, which can effectively improve the consistency of electrode chip batch production.

2. Laser cleaning before battery welding

In recent years, laser welding has become the standard configuration of power battery production line and is widely used in the welding of power battery lugs, sealing nails, bus bars, battery modules, etc. A clean and uniform surface is a basic prerequisite for successful and durable welding and bonding. Therefore, before welding, surface treatment shall be carried out on each welding part to remove the pollutants at the weld joint, which can effectively improve the welding quality and reduce the cost.

Laser cleaning is applied to the cleaning process of sealing nails, adapter pieces of the cell section, bar pole of the module section, single cell blue film, single cell silica gel, and single cell coating, effectively removing dirt and dust on each end face, preparing for battery welding in advance, and reducing defective welding products.

3. Laser cleaning during battery assembly

In order to prevent the lithium battery from safety accidents, the lithium battery cell is often pasted with glue to play the role of insulation, prevent short circuit, protect the circuit and prevent scratches.

Laser cleaning shall be carried out for CMT weld of battery pack tray, electrophoretic paint of upper cover plate of battery pack, sealant track oxide layer of battery pack box, and oxide layer of protective bottom plate before welding to improve adhesive force of gluing. No harmful pollutants will be produced after cleaning. Under the circumstance of paying close attention to environmental protection, this green and environment-friendly cleaning method will become more and more important.

Current laser cleaning solutions such as pole piece cleaning, sealing nail cleaning, adapter piece cleaning, bar pole pole cleaning, single cell blue film cleaning, single cell silica gel cleaning, single cell coating cleaning, battery pack tray CMT weld cleaning, battery pack upper cover plate electrophoresis paint cleaning, battery pack box sealant track oxide layer cleaning, protective base plate pre welding oxide layer cleaning, etc. are common and widely used in battery industry.

A new round of large-scale manufacturing of lithium batteries has been launched. The new round of manufacturing process requires higher quality consistency and higher precision of process control. Lianying Laser insists on starting from laser welding and intelligent manufacturing, taking customers as the guide, insisting on innovation, wholeheartedly solving customers' welding and cleaning problems, and is committed to providing customers with more perfect intelligent manufacturing solutions for equipment.

About HGTECH: HGTECH is the pioneer and leader of laser industrial application in China, and the authoritative provider of global laser processing solutions. We have comprehensively arranged laser intelligent equipment, measurement and automation production lines, and smart factory construction to provide overall solutions for intelligent manufacturing.