The automotive industry has traditionally been at the forefront of engineering applications for fiber laser systems. The new demands made by the breakthrough of e-mobility has placed even more requirements on fiber lasers in reducing costs, improving performance, and creating new composite materials and components. Read on to learn more about how fiber lasers support the inevitable breakthrough of e-mobility

1. How Fiber Lasers Supportthe Breakthroughof e-mobility (SlideShare)
The automotive industry has traditionally been at the forefront of engineering applications for
fiber laser systems. The new demands made by the breakthrough of e-mobility has placed
even more requirements on fiber lasers in reducing costs, improving performance, and
creating new composite materials and components.
The major challenges facing the continued expansion of e-mobility are the high costs of e-
vehicles, in particular, e-vehicle batteries; “range anxiety”, in other words, fear of running out
of power before arriving at one’s destination, and the currently inadequate e-mobility
charging network. These problems suggest an urgent need for improved battery
technologies, more efficient lighter drive trains, and improved e-mobility infrastructures.
Here we will focus mainly on how fiber lasers are supporting new developments in batteries
and drive trains, including electric motor technologies, new composite materials, and
lightweight construction processes.
Contents
How Fiber Lasers Support the Breakthrough of e-mobility .......................................................1
E-vehicle batteries..................................................................................................................2
What are the requirements of e-vehicle batteries?............................................................2
How do e-vehicle batteries work? ......................................................................................2
Cathode materials and construction...................................................................................2
The anatomy of an e-vehicle battery and the need for fiber lasers ...................................3
Fiber laser joining of e-vehicle battery components ..........................................................3
Fiber laser welding is the only practical solution................................................................4
Fiber laser bus bar welding ................................................................................................4
Fiber laser cutting metal foils for e-vehicle batteries..........................................................4

2. Solid-state technology - the next stage in e-vehicle battery development............................5
Fiber laser cutting of lithium metal foils ..............................................................................5
Electric motors for e-vehicles.................................................................................................6
Fiber laser hairpin ablation for stator manufacture ............................................................6
Fiber laser hairpin stator welding .......................................................................................7
E-mobility drivetrain weight reduction....................................................................................7
Conclusions............................................................................................................................8
Contact information................................................................................................................9
E-vehicle batteries
The global e-vehicle battery market is expected to reach £84 billion by 2025 and will be
dominated by lithium-ion batteries, though other technologies such as supercapacitor power
sources and fuel cells are likely to play an increasingly important role. Currently, battery
technologies fall significantly short of what is required.
What are the requirements of e-vehicle batteries?
Ideally, e-vehicle batteries should store a large amount of energy, deliver it quickly, and
charge in the amount of time it takes to enjoy a cup of coffee at a Motorway Service Station.
Arguably, we can almost achieve that now, if you just need a quick top-up charge but a full
charge takes several hours.
Achieving improved performance and reduced cost aren’t the only goals demanded by e-
vehicle manufacturers. Long lifetimes are also vital. New generation e-vehicle batteries
should last for at least 10 years; a big ask given the extreme operating conditions they must
endure, including high vibration levels and intensive thermal cycles.
How do e-vehicle batteries work?
Let’s take a closer look at how e-vehicle batteries work. Invariably these are lithium-ion
batteries and generate current from the movement of electrons and ions. When the battery
delivers power, lithium ions move from the anode electrode to the cathode electrode through
the electrolyte. As the ions collect on the cathode, they create a positive charge which
attracts electrons, which carry a negative charge. The electrons move through an external
circuit, providing the current that powers the electric motor. When we recharge the battery,
the reverse happens.
Cathode materials and construction
The cathode is the most crucial component in this process. It is usually made of lithium
cobalt nickel oxide. Nickel is used as it is cheaper than cobalt and has an even higher
energy density, but there is a significant problem: lithium cobalt nickel oxide can release
oxygen even at only slightly elevated temperatures, thus increasing the risk of fire. To
overcome this, an additional stabilisation metal such as manganese or aluminium is added
to the mix. Alternatively, cathodes may be lithium iron phosphate or lithium nickel
manganese cobalt oxide. Anodes are usually graphite.
However, one solution doesn’t fit all. Different kinds of e-vehicle require different properties
from their batteries.
 All-electric vehicles demand a high storage capacity to maximise the driving range. This
can be achieved by increasing the nickel content but doing so increases the fire risk;
finding a safe compromise is challenging.

3.  For hybrid vehicles, the aim is to maximise the rate of energy delivery rather than the
storage capacity. Such batteries provide good acceleration. This is best achieved with
porous cathodes made from tiny particles, allowing more diffusion space for the lithium
ions.
The anatomy of an e-vehicle batteryand the need for fiber lasers
Battery assemblies are complex with multiple layers of several metals, including copper,
nickel, aluminium, nickel-plated aluminium, and more. Material thicknesses also vary from as
small as 25 micrometres to several orders of magnitude larger.
A complete battery assembly consists of thousands of individual cells connected in parallel
or in series. At the cell level, the components are negative and positive electrodes,
electrolyte, separators, and the cell case. Cell geometries may be cylindrical, pouch, or
prismatic. At the module level, the cells are connected and assembled in a structure, and at
a pack level, modules are connected along with controllers and sensors and are housed in a
mechanical structure. In each instance, the optimum joining method depends on the type of
cell and electrical, mechanical and thermal requirements.
Fiber laser joining of e-vehicle batterycomponents
Joining such dissimilar metals and components to achieve highly reliable assemblies is
highly demanding. Traditionally a wide range of joining techniques have been employed
including, amongst others, soldering, resistance welding, micro-arc welding, ultrasonic
welding, and laser welding. Some of the advantages of fiber laser welding are their flexibility,
stability, consistent power output, and accuracy.
Various side-by-side studies of these techniques, for example Joining Technologies for
Automotive Battery Systems Manufacturing, show that in many process steps, fiber laser
welding provides the best solution, and in some instances where components are difficult to
reach it is the only solution.
Underneath the bonnet of a Nissan e-NV200 Evalia electric car

4. Fiber laser welding is the only practical solution
Laser welding uses a focused laser beam to provide localised heating for joining these
components. The laser beam has a small cross section and high energy concentration. This
allows it to produce deep narrow welds at high speed. Thus, it creates only a low level of
heat in the assembly. This is a vital property for tab welding as the chemical components of
the cell are highly heat sensitive and easily destroyed by excessive heat. It is crucially
important to control the process parameters accurately, which can be achieved readily with
fiber lasers. Other areas that benefit from fiber laser welding include sealing battery casings
and bus bar joints.
Fiber laser bus bar welding
The next stage in the assembly process is to assemble the modules into battery packs by
connecting the individual cells with bus bars, which are typically constructed from aluminium
or copper. This is more challenging than it initially appears. Both aluminium and copper are
reflective and thermally conductive, and these must be joined to dissimilar metals.
Typically, thousands of individual cells must be joined, and every single join must be highly
reliable and able to withstand ten years of operation in adverse conditions. There must be no
open or partially open circuits; in other words, everything needs to be as close to perfect as
possible.
Developing such processes proved challenging. Initially, methods were developed using
high energy multi-mode lasers, but this proved to be unsatisfactory. The main problem was
this type of laser produced excessive and poorly controlled heat input, poor weld profiles and
unacceptable spatter.
However, trials on welding 300-micron copper tabs using SPIs 100 W nanosecond laser to
form multiple welds provided excellent results. For high throughput and thick metal welds, a
high-power single-mode CW fiber laser with oscillation welding proved ideal. Welds can be
tailored to the job in hand, producing excellent results. The solution is also highly flexible.
Fiber laser cutting metal foils for e-vehicle batteries
In addition to providing a solution for battery component joining challenges, fiber lasers also
play a significant role in manufacturing the metal foils described above. These include lithium
coated copper nickel cobalt cathodes and carbon coated aluminium and copper anodes with
a wide range of thicknesses. It is a huge challenge:
 Traditionally such material is cut using mechanical cutters, though the process is
relatively costly. Cutters quickly blunt and must be replaced regularly to avoid foil
damage and poor quality of cut. Replacing the cutters halts the production further adding
to the cost.
 Close process control is also needed; to achieve the necessary high-reliability standards
already mentioned. The cut foils must be near perfect. If any burs are present, the
probability of short circuits either during manufacturing or later in the field increases
dramatically. The potential costs are enormous.

5. Fiber lasers are effective in the remote and precise cutting of battery foils
Fiber laser cutting avoids all those problems. A fiber laser is easy to control and provides
essentially bur-free battery foils consistently. The laser requires virtually no maintenance,
preventing the need to shut down the production line. Cutting speeds are also fast, up to 2.5
meters per second.
Solid-state technology - the next stage in e-vehicle battery development
So far, we have addressed electrochemical batteries for e-vehicles, but substantial ongoing
research is investigating solid-state lithium-ion batteries. These use anodes made of pure
lithium and have the potential to achieve substantially higher power densities. Extremely thin
low weight anodes can be made which allow batteries to be constructed with three times the
power density of conventional electrochemical batteries.
Physically they are much smaller too, occupying only a third of the volume, so they are far
easier to integrate into car designs. An additional advantage is improved safety, as there are
no flammable liquid electrolytes.
Fiber laser cutting of lithium metal foils
While such advanced battery technologies are currently confined to the laboratory,
conventional cutting techniques employ traditional die cutting tools. These need cleaning
after each cut has been made, as the lithium adheres to the cutting surface. This results in
cross-contamination, inferior edge definition and ultimately, unreproducible performance.
Also, because of the high reactivity of lithium with water, the whole process must be
conducted in an extremely low humidity environment. Clearly, mechanical die cutting is not
an option for high throughput production.

6. Fiber Laser cutting is now considered to be the enabling technology for producing solid-state
batteries for e-vehicles. A recent study employing a G4 Pulsed Fiber Laser from SPI Lasers
UK showed promising results with easy and safe separation of lithium metal anodes. As the
process is contactless, the cutting-edge quality was highly reproducible.
The research concluded that fiber laser cutting of lithium metal foils is suitable for mass
production. Toyota has brought forward its plans to release solid state e-vehicles by 5 years
to 2020 while Mercedes-Benz is exploring its use in electric busses.
Electric motors for e-vehicles
It isn’t only batteries that are benefiting from new technologies; electric motors are receiving
attention too, with the focus on improved efficiency, reduced size, increased power, and
lower cost. Fiber lasers play a significant role in various stages of electric motor
manufacture, including cutting, ablation and welding.
SPI Lasers and parent TRUMPF will be influential in the future of e-mobility
Fiber laser hairpin ablation for stator manufacture
Crucial to the design and manufacture of electric motors is the stator, the stationary part of
the motor that provides the magnetic field that drives the rotating part of the motor.
Essentially it is an electromagnet consisting of a metal core and copper winding. One
winding design employed in most electric motors for e-vehicles is hairpin stator winding.
Compared with other winding techniques, it can improve maximum torque by up to 44% and
continuous power by 17%.
Hairpin laser ablation is effectively delivered through fiber lasers

7. To produce the winding, pre-formed pieces of insulated copper wire (known as hairpins) are
mounted on the stator, considerably simplifying traditional stator winding. The hairpins must
be joined both mechanically and electrically to create the coil. Thus, the joining process is
critical as large numbers of contact points need to be produced in a confined space.
While laser welding is the joining method of choice, see below, before welding, insulation
material must be removed from the individual hairpins. The conventional way of achieving
this is mechanical removal using a wire brush or similar technique, but this is fundamentally
unreliable, difficult to control, and requires frequent maintenance.
Recently SPI Lasers has developed a far more reliable process using fiber lasers. Using a
nanosecond pulsed fiber laser, efficient hairpin insulation material ablation can be carried out
rapidly and reliably, leaving a pristine copper surface ready for the next stage – laser
welding.
Fiber laser hairpin stator welding
Depending on the motor design, hairpins of various sizes and shapes are used. A typical
geometry might be 6 mm long with a rectangular cross-section. One approach to welding
these to the stator is to use a high-power CW multimode laser. However, the solution is far
from perfect. Set-up is challenging, and it is difficult to avoid excessive burning of insulation
material a few millimetres away from the welding area. There are also severe problems with
spatter, creating long term reliability concerns.
A far better solution is to use a 2-kW single mode fiber laser, oscillating the beam as we
described in busbar welding. This allows accurate control of the welding zone and heat input
and substantially limits spatter.
E-mobility drivetrain weight reduction
Fiber lasers are contributing to new e-mobility drivetrain weight reduction, creating new ways
to machine and join emerging lightweight materials.
The drive for improved efficiency and safety has led automotive manufacturers to look at
alternative metals such as aluminium and magnesium to reduce vehicle weights. Compared
with combustion engine vehicle powertrains, a typical powertrain on a full e-vehicle with a
100-kW electric motor and 36 kW battery pack is 125% heavier. The main offenders are the
electric motor and battery pack.
All e-vehicle manufacturers are looking to weight saving design approaches that include
multi-material solutions, including metal alloys and composites. One method is to use all
aluminium bodies, but this is significantly more expensive than steel, and there are potential
additional recycling problems at the end of life.
Magnesium is another potential solution. As a structural metal, it is the lightest of all.
Although it is costly and suffers from various metallurgic problems, including high-
temperature creep, given that it is 75% lighter than steel and 33% lighter than aluminium, the
potential weight saving is enormous.

8. The Tesla Model S body structure is a blend of aluminum and high-strength steel
Magnesium’s creep problem may be addressed by incorporating rare earth elements into
magnesium alloys, but this also comes at a significant cost. As a result, there is currently
extensive research into new processing methods that can provide the necessary tensile
strength without the need to do that. In fact, it has the potential to increase strength, stability
and stiffness, delivering a higher yield strength than most other structural materials. It is
currently projected that by 2020 the proportion of magnesium incorporated in chassis and
body parts could be increased to 150 Kg.
Joining these materials is a massive challenge in which fiber laser welding is playing a
significant role. Already they are being used for assembling aluminium doors and joining
dissimilar materials such as aluminium outers and steel inners with far better control than is
possible with traditional joining techniques such as arc and resistance spot welding. Laser
welding also means thinner materials can be used and, as they can be finely focused, flange
size can be reduced or eliminated entirely.
Research into laser welding of the new lightweight alloys such as aluminium/magnesium,
aluminium titanium, and magnesium titanium while avoiding the formation of brittle
intermetallic compounds is ongoing, though considerable progress is being made. There is
little doubt that fiber laser welding will be a significant contributor to drive train weight
reduction breakthroughs for e-mobility.
Conclusions
Fiber lasers are making a considerable contribution to the rapidly improving technologies
required by the continued growth of e-mobility. Better batteries, more efficient electric
motors, and drive train weight reduction are all benefitting from the latest developments in
fiber lasers. Furthermore, confidence that fiber lasers will rise to new and emerging
manufacturing challenges is empowering designers to explore novel solutions.

9. If you are excited by the contribution fiber lasers are making to the breakthrough of e-
mobility, we would be delighted to share our latest thoughts with you, so please get in touch.
Contact information
Contact SPI Lasers at:
SPI Lasers UK Ltd
6 Wellington Park
Tollbar Way, Hedge End
Southampton, SO30 2QU
United Kingdom
Switchboard: +44 (0)1489 779 696 – Option 0
Website: https://www.spilasers.com/
Full contact information: https://www.spilasers.com/our-locations/
Image Credits: Kārlis Dambrāns, SPI Lasers and Wikipedia