Laser cleaning is known as "the earliest green cleaning technology with development potential in the 21st century". It can change the grain structure and orientation of the substrate surface without damaging its body surface, and can control the roughness of the substrate surface, thus enhancing the comprehensive performance of the substrate surface.
 

With the acceleration of industrialization and "double carbon" The goal has been steadily advanced, gradually replacing the traditional cleaning process in many fields, and gradually becoming an indispensable equipment manufacturing technology in high-end manufacturing fields such as industry, military industry, shipbuilding, aerospace and so on.

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 high energy density, controllable direction and strong convergence ability, to make the laser interact with the oil, rust, dust, coating, oxide layer or film layer attached to the workpiece substrate, and separate it 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, vibration of substrate surface and pollutant separation. At present, there are laser ablation cleaning method, liquid film-assisted laser cleaning method and laser shock wave cleaning method, which can stably and effectively clean various regular substrate surfaces, including metals, alloys, glass and various composite materials.

Application of laser cleaning in lithium battery manufacturing

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, electrode manufacturing, cell manufacturing and battery assembly. By adopting laser, cleaning head and control software and computer integrated control, the battery manufacturing technology level has been greatly improved.

1.Pole laser cleaning

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

Traditional mixed ethanol cleaning is easy to cause damage to other parts of lithium battery. Using laser to clean metal foil can not only improve the efficiency of the cleaning process and save cleaning resources, but also establish real-time monitoring of cleaning process data and quantitative determination of cleaning results, which can effectively improve the consistency of the production of polar plates.

2.Laser cleaning before battery welding

In recent years, laser welding has become the standard equipment of power battery production line, and is widely used in the welding of power battery lug, sealing pin, bus bar, battery module, etc. Clean and uniform surface is the basic prerequisite for successful and durable welding and bonding. Therefore, before welding, surface treatment shall be carried out for 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 the sealing nail and adapter piece of the cell section, the bar pole of the module section, the blue film of the single cell, the silica gel of the single cell, and the coating of the single cell. It can effectively remove the dirt and dust on each end face, make preparations for the battery welding in advance, and reduce the welding defects.

3.Laser cleaning during battery assembly

In order to prevent safety accidents of lithium batteries, the lithium battery cells are often externally glued to play the role of insulation, prevent the occurrence of short circuits, protect the lines and prevent scratches.

Laser cleaning shall be carried out for the CMT weld of the battery pack tray, the electrophoretic paint on the cover of the battery pack, the oxide layer of the sealant track of the battery pack box, and the oxide layer of the protective base plate before welding to improve the adhesion of the adhesive or the adhesive coating. After cleaning, no harmful pollutants will be generated. Under the circumstance of high attention to environmental protection, this green and environmental protection cleaning method will become more and more important.

Electrophoretic paint endows the cover plate with certain decorative properties and provides anti-corrosion protection, such as rust prevention, impact prevention, corrosion resistance, etc. However, due to some special requirements, it is necessary to remove the electrophoretic paint film.

At present, the metal stamping method is mainly used for the mass production of the top cover sheet. The stamping oil will be used in the production process, and the stamping oil needs to be cleaned after the production. The metal stamping method will inevitably produce a metal edge. When the top cover sheet of the power battery has a metal wire, burr and other edge, at the junction of the top cover sheet and the pole, it will cause a short circuit fault of the power battery, and there is an explosion risk. Therefore, the cover plate cleaning process needs to solve all the above problems.

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 machine, measurement and automation production lines, and smart factory construction to provide overall solutions for intelligent manufacturing.