Oil prices rise, lithium batteries increase, laser cleaning the second spring?

Power battery sales continue to grow

On March 11 this year, the China Automotive Power Battery Industry Innovation Alliance released the monthly data of power batteries in February 2022. In the data, the output growth rate of power batteries increased by 236.2% year-on-year, which was more obvious than the increase in sales of new energy vehicles.

Power battery production in the first two months of this year increased tenfold compared with 2020 and 2021. Not only the output, the battery loading volume also increased by 145.1% year-on-year, showing a rapid growth momentum.

Battery Alliance February data

Mainland China is currently the country with the largest demand for new energy vehicle batteries. In the future, according to the "New Energy Vehicle Industry Development Plan 2021-2035" issued by the Ministry of Industry and Information Technology, the mainland will continue to reduce the production of gasoline and diesel vehicles, enhance the basic capabilities of industries such as power batteries, and further increase and optimize the construction of the new energy vehicle industry.

As one of the core components of new energy vehicles, power batteries are the main source of cost composition of new energy vehicles, and their connection quality and service life directly affect the performance indicators of electric vehicles, which is crucial for the development of electric vehicles.

Laser cleaning in the power battery application market status

The production of lithium batteries is a "roll-to-roll" process, whether it is lithium iron phosphate batteries, sodium-ion batteries or ternary batteries, they all need to go through the processing process from thin films to individual batteries and then to the installation of battery systems. The preparation process of lithium batteries can be roughly divided into three stages: electrode production, cell synthesis, and encapsulation.

Lithium battery process flow

In these three large processes, there are several key processes, which will directly affect the battery's power storage capacity, product safety and service life. Therefore, the performance of batteries produced by different production processes varies greatly. In these links, laser cleaning can currently participate in more than a dozen preparation processes, which can greatly improve the premium rate of lithium batteries.

Laser cleaning is used in power batteries

As the demand for power batteries continues to increase, the demand for laser cleaning equipment will also rise. Next, we will focus on several of these application processes and comparative advantages.

01

Copper-aluminum foil laser cleaning before pole sheet coating

The positive and negative electrode sheets of lithium batteries are made by coating the positive and negative electrode materials of lithium batteries on aluminum foil copper foil, and the polar plate coating is of great significance to the safety of the battery. If the coating process is mixed with particles, debris, dust and other media, it will cause a micro-short circuit inside the battery, which will cause the battery to catch fire and explode in severe cases.

Therefore, the foil needs to be cleaned before coating to obtain a completely clean, oxide-free surface.

The existing battery poles are generally ultrasonically cleaned, and the ethanol solution is used as a cleaning agent as a cleaning process before coating. This approach has the following drawbacks:

1. When ultrasonic cleaning of metal foil parts, especially workpieces made of aluminum alloy materials, affected by frequency, cleaning time and power, the cavitation effect of ultrasonic waves is easy to corrode the aluminum foil, resulting in fine holes, the longer the action time, the larger the holes.

The foil used in the pole sheet of lithium batteries is generally a single zero foil with a thickness of 10 μm, which is more susceptible to tearing into holes due to cleaning process problems.

2. Using ethanol solution as a cleaning agent is not only easy to cause damage to other parts of lithium batteries, but also prone to the phenomenon of "hydrogen embrittlement", which affects the mechanical properties of aluminum foil.

3. Although the cleaning effect is better than the traditional wet chemical cleaning, the cleanliness is still not as good as the laser cleaning, and there will still be contaminants on the surface occasionally, resulting in the coating and foil detachment or shrinkage holes.

When the pole piece is slitted, the coating is detached from the foil

There are contaminant particles on the surface of the foil, and the low surface tension causes the liquid film to migrate to the emitting pattern around the particles to form a shrinkage dot defect

Laser cleaning as a dry-type non-consumable cleaning, in the aluminum foil surface treatment of cleanliness and hydrophilic and other indicators are close to zero defects, to maximize the effect of pole plate sizing coating.

The use of laser cleaning metal foil can not only improve the efficiency of the cleaning process, 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 mass production of pole pieces.

The following is the test data of the water drop laser:

02

Laser cleaning before electrode ear welding of the battery cell

The polar ear is a metal strip that draws the positive and negative poles out of the battery, and is the contact point when the battery is charged and discharged. Surface contaminants such as grease, corrosion inhibitors and other compounds in processing can cause problems such as poor welding, cracks and porosity at the weld.

In the factory process, the polar ear often appears uneven, bent or even twisted, and the welding strength of the polar ear and the battery cell is weak, so that the phenomenon of virtual welding, false welding, short connection and so on occurs during welding, resulting in a decrease in the conductivity of the welded joint, and ultimately limiting the overall performance of the battery pack.

Whether the surface of this contact point is clean or not will greatly affect the reliability and durability of the electrical connection.

The existing polar ear cleaning mostly uses manual cleaning, wet chemical cleaning or plasma cleaning:

Manual cleaning is inefficient and costly;

Although the wet assembly line improves the efficiency, the length of the assembly line is longer, the factory area is large, and the chemical agent is also easy to damage other lithium battery parts;

Although plasma cleaning does not require liquid media, but also requires process gas as a consumable, and gas ionization will cause the positive and negative poles of the battery to be easily turned on, and the application often has to flip the positive and negative pole ears separately for cleaning, and the actual efficiency is not high.

An artificial pole ear production line

Laser cleaning can effectively remove dirt, dust, etc. from the end face of the cell pole, and prepare the battery for welding in advance.

Because laser cleaning does not require any consumables such as solid liquid gas, compact structure, small footprint, significant cleaning effect, can greatly improve the production cycle, reduce manufacturing costs, can be completely removed organic matter and tiny particles on the basis of roughening the welding surface, improve the reliability of subsequent laser welding. It is one of the best choices for pole ear cleaning.

A kind of battery cell polar ear laser cleaning device

Water drop laser test data on roughness before and after cleaning

03

During assembly, the outer adhesive is cleaned

In order to prevent the safety accident of lithium batteries, it is generally necessary to carry out external adhesive treatment of lithium battery cells to play the role of insulation, prevent short circuits and protect lines and prevent scratches.

At present, many domestic battery companies still rely on manual or low-automation processes to complete this link, most of them are just simple parcel operations, which are not efficient and expensive. There is no effective and comprehensive cleaning of the battery case before the coating, and there is no accurate detection of the effect after the coating.

When CCD detection is performed on unpurged cell outer membranes, there will be undesirable conditions such as wrinkles, bubbles, and scratches, and bubbles with a diameter of ≥ 0.3 mm can often be detected. There is a probability of leakage and water rust corrosion, which reduces battery life and also has safety hazards.

The battery cell is wrapped in blue film

Laser cleaning can reach Sa3 level in the surface cleaning ability of the battery cell, and the cleaning rate is more than 99.9%, and there is no stress effect on the surface of the battery cell.

Compared with other cleaning methods such as ultrasonic cleaning or mechanical grinding, the physical and chemical indicators such as the surface hardness of the battery cell can be guaranteed to the greatest extent and the service life of the battery can be extended.

Laser cleaning of the battery cell before the external adhesive, cleaning the dirty surface of the battery cell, roughening the surface of the battery cell, improving the adhesion of the glue or glue, and no harmful pollutants will be generated after cleaning, which is the guarantee of excellent products.

Laser cleaning in the application of power batteries

In addition to the above examples, laser cleaning also has great alternative advantages in more than a dozen other processes such as battery cover electrophoretic paint removal and foil label cleaning.

However, at the same time, the domestic laser cleaning machine is also facing the dilemma that the laser power is too small, and the existing cleaning efficiency cannot keep up with the manufacturer's production beat.

The maximum power of pulsed lasers used for cleaning on the domestic market still does not reach 2000W, which has caused difficulties in the application of laser cleaning in the actual production process.

Water drop laser composite cleaning solution

As early as 2018, Waterdrop Technology paid great attention to the application of laser cleaning in the lithium battery industry, and continued to invest in technology research and development for the dilemma of low efficiency of laser cleaning machines on the existing market.

In the past two years, the composite laser cleaning process of 6000W continuous + 1000W pulse has been successfully launched, which has made up for the lack of power through process optimization.

The cleaning efficiency of this product is 500% of the 1000W single-pulse laser cleaning machine, which is one of the products with the highest laser cleaning efficiency on the market, and has great advantages in removing thick paint layer, thick rust, oil pollution, etc., and is widely used in high-speed rail wheelset shafts, aircraft skins and other projects. In the field of power batteries, the cleaning application of pallet CMT, protective bottom plate and other processes has a relatively good performance. However, there are also relative shortcomings such as heat generation and micro-melting of substrates that are not suitable for ultra-thin precision cleaning materials.

How to expand the application of composite cleaning on precision parts such as aluminum foil is a technical problem that we will focus on next.

Water drop laser exclusive compound cleaning machine

Laser cleaning in the future application trend of power battery

The most expensive material cost of a powered car is the battery part, followed by the body base and drive system. Power batteries are mainly divided into liquid lithium-ion batteries LIB and polymer lithium-ion batteries LIP, of which most of the battery costs come from cathode materials, and the required nickel, cobalt, lithium and other high-quality mineral resources are mainly distributed in South America and Australia and other countries.

Some mainland enterprises mainly join SQM through war investment and mergers and acquisitions to obtain high-quality lithium ore resources. Affected by the global distribution of salt lakes and lithium mining areas of cathode materials, the main development trend of the mainland in the future may be biased towards lithium iron phosphate batteries, sodium ion batteries and hydrogen fuel cells.

Cost structure of powered vehicles

Whether it is an existing power battery or a new type of battery that may be developed in the future, the demand for industrial cleaning will not change. Even if you want to catch up with foreign leading technologies, the demand for industrial cleaning will only be greater: to develop to higher precision, higher quality standards, and to achieve integrated automation.

In this trend, neither the traditional manual operation nor the chemical acid and alkali agent can meet the needs of the real-time regulation of the whole process, and this is precisely the housekeeping skill of laser cleaning: fully automated integrated system, micron-level controllable precision, green pollution-free cleaning method and the highest level of material surface cleanliness, all highlight the fit between laser cleaning and the power battery industry.

As the impact of the Russo-Ukrainian War expanded, powered cars ushered in new market opportunities for rapid development. The production of power batteries has also doubled. This is the development opportunity of China's power battery industry, and it will also be the blue ocean of the laser cleaning industry.

Source: Water drop laser