Lasers in EV

As electric vehicles grow in popularity, the use of lasers can help with their production

YOU CAN ALSO LISTEN TO THIS ARTICLE

Electrical vehicles (EVs) are all around us because, these days, it’s not just the tree huggers that are replacing their gasoline engines for battery-powered vehicles. EV popularity is growing with consumers of all stripes based on a variety of factors, including cost-efficiency, performance, technological features, and the desire to align with anticipated automotive trends and government regulations.

In terms of cost-efficiency, EVs generally have lower operating costs per mile compared to their combustion-engine counterparts; charging an electric car is often cheaper than buying gasoline. EVs also have fewer moving parts than traditional vehicles resulting in less maintenance. Top that off with fewer fluids to change and fewer components that can wear out in general, and their popularity becomes even more understandable.

One of the most important parameters for a battery pack is its charge capacity per weight, represented as kWh/kg, which motivates battery and car makers to put in as many “battery cells” as possible while getting rid of everything else.

As far as performance is concerned, consumers are thrilled with the instant torque and quick acceleration EVs provide. They also appreciate their quiet operation, offering a more serene driving experience compared to noisy internal combustion engines. Add a touchscreen display, advanced driver-assistance systems and autonomous driving capabilities and electric cars are here to stay.

Powering the popularity

Powering this popular form of mobility is the lithium-ion (Li-ion) battery pack. One of the most important parameters for a battery pack is its charge capacity per weight, measured in kWh/kg. This means that battery and car makers want to put in as many “battery cells” (the basic Li-ion unit that stores charge) as possible and get rid of anything else, such as metal parts that house together several cells in a “module,” several modules in a pack or even the battery pack entirely.

This includes the concept of going C2V or “cell to vehicle,” floated by Tesla in 2020. Here, cells are integrated directly into the car’s body instead of being contained in a separate, traditional battery pack.

Modern Li-ion battery factories use a roll-to-roll process, where long rolls of foils are processed for coating, drying and cutting before the foils are packed into individual cells.

But what does that have to do with lasers?

Moving away from a modular approach (cells, modules, battery pack) means that servicing or fixing the battery of an EV is almost impossible, and therefore, the reliability, safety and structural integrity of the battery must be very high. That is where laser processes come into play.

There are several processes in the manufacturing of the battery pack in which lasers can be used to improve reliability and throughput. Examples range from cutting and cleaning to welding.

At the cell level

The battery cell is made of three thin foils: anode foil (typically aluminum), separator foil (polypropylene or polyethylene) and cathode foil (typically copper). The anode and cathode foils are coated with a mixture of an active material, conductive agent and binder. The foils are wound together to make the cell, a positive and negative metal tab is attached to the anode and cathode, and a liquid electrolyte is poured into the cell.

High-power nanosecond-pulsed IR and UV lasers are often used​ to cut the foils and clean and weld the tabs to the anode and cathode. These laser processes create smoother edges and surfaces, reducing the risk of lithium dendrite formation, a common cause of Li-ion battery failure.

Modern Li-ion battery factories use a roll-to-roll process, which means processing long rolls of the foils for coating, drying and cutting before the foils are packed into individual cells. High-power (hundreds of watts) nanosecond-pulsed IR and UV lasers are commonly used to cut the foils and clean and weld the tabs to the anode and cathode.

These laser processes have a big advantage over other processes as they create smoother edges and surfaces. This reduces the risk of lithium dendrite formation, which is a common cause of Li-ion battery failure.

Focus on the frame

The EV battery frame holds the cells, modules, coolant lines and power harness. In the C2V concept, this can be a part of the vehicle chassis. Here, laser welding can produce strong and reliable joints. Traditionally, kilowatt-class fiber lasers at a 1-micron wavelength are used.

While efficiently absorbed by aluminum and steel, this wavelength is not absorbed by copper, which is used in the power connections. Recently, green (515-nm to 535-nm frequency-doubled fiber lasers) and blue (450-nm direct-diode laser) high-power lasers made their debut to improve the throughput of copper welding.

Good welding of different metals has always been a challenging pursuit, however. Therefore, a new approach to solving this problem is emerging to control the shape of the laser beam, such as using two beams with different sizes and powers.

In addition to the current laser applications in battery manufacturing, several applications are currently being researched. Let’s consider a few:

  • Tabless Li-ion batteries (patented by Tesla in 2020). In this scenario, a larger battery is used by removing the tab, which allows a shorter electron path length. This leads to a larger energy capacity, more power output and longer range.
  • All solid-state batteries. Here, liquid electrolyte is replaced with a solid electrolyte (usually a ceramic). As the solid electrolyte can also act as a separator (removing the separator foil from the battery construction), it, presumably, offers safer construction as it no longer swells due to a leak or temperature change. This can lead to higher energy capacity.
  • Using high-power ultra-fast lasers for nano structuring and texturing of electrode materials. This approach enables different electrode architectures (3-D, holes, grids, lines, etc.) with improved electrochemical performance, reduced mechanical tension during cycling and improved lifetime.

In conclusion, laser applications are a key ingredient in the higher production rates of EVs today. Lasers provide superior reliability and throughput over other methods and enable new technologies. The successful utilization of laser processes, however, requires precise control of the laser beam parameters, such as laser power and beam profile.

Watch the video to learn about the Ophir BeamWatch integrated industrial laser beam profiler, which was developed to help users avoid deterioration of their laser product’s quality.

For those that are involved in these activities, MKS offers a wide range of Ophir instruments and systems for measuring laser beam parameters and ensuring outstanding performance. BeamWatch, as just one example, offers a simple way for laser users to evaluate their machine’s performance. By providing real-time measurements of multiple profiles along the beam propagation, users can receive Go/No-Go readouts that indicate if corrective actions are required. To cater to growing consumer demand, BeamWatch and Ophir’s range of systems will be key tools for manufacturers moving forward.

MKS Ophir

Get industry news first
Subscribe to our magazines
Your favorite
magazines
under one roof