How are electric vehicle batteries manufactured? Understanding the assembly process

When people talk about the electric vehicle battery, they often fail to consider the beauty of its design. EV battery design does not end with just each individual cell, but its entirety– how the cells are combined so that overall battery output is capable of powering an entire electric vehicle. 

In order to do so, we must first answer: “How are EV batteries manufactured?” Here, we delve into the manufacturing process of cell components and battery systems or cell contacting systems.

What are EV batteries?

EV batteries are the power sources of an electric vehicle. If you think of EV batteries as a single cell, like those used in everyday gadgets, such as a flashlight or your smartphone, the electric vehicle wouldn’t be able to run.

The term “EV battery” actually refers to the battery pack, since it contains many individual EV battery cells that provide the power needed for the car to run. 

The beauty of EV battery manufacturing lies in how these EV battery cells are combined to form a pack. But more on this in a later section.

What are EV batteries made of?

To better understand what EV batteries are made of, we first need to talk about an EV battery’s cell components.

The electric vehicle battery cell consists of four major components: the negative electrode known as the anode, the positive electrode known as the cathode, the electrolyte, and the separator. 

EV batteries are made of base metals namely aluminum, copper, and iron. However, the types of electric vehicle batteries are distinguished from each other by the materials that can be found in the anode and cathode.

Below are the materials they contain:

BATTERY TYPE	ANODE	CATHODE
Nickel-Cadmium Batteries	Cadmium hydroxide	Nickel hydroxide
Lead-Acid Batteries	Lead	Lead (*electrolyte is mild sulfuring acid)
Nickel-Metal Hydride Batteries	Hydrogen-absorbing alloy	Nickel oxy-hydroxide
Lithium-Ion Batteries	Lithium and graphite	Lithium, nickel, cobalt, manganese

What’s the difference between EV battery cell, module, and pack?

• EV battery cells: the smallest units in the hierarchy, these come in cylindrical, pouch, or prismatic formats. A single lithium-ion battery produces 1-6V of power.
• EV battery modules: composed of single battery cells are connected together in series or in parallel and contained within a sturdy housing
• EV battery packs: the final form of the EV battery. Modules are connected together in series or in parallel to produce the amount of power needed for specific applications in an EV. This is almost always the heaviest part in an electric vehicle.

How long does an EV battery last?

On average, an EV battery, specifically lithium-ion ones, last between 10 and 20 years before they need to be replaced. EV batteries do not just die fully; instead they lose charging capacity slowly over a period of time. For example, the Tesla Model S battery loses 5% of its original capacity after driving for the first 50,000 miles.

What is the assembly process in manufacturing EV batteries?

In manufacturing EV batteries, it is important to take into consideration the design of the battery, including its size, frame, and the power requirements of the electric vehicle. 

The assembly process of EV batteries begins with the single cell. Inside the cell, the anode and cathode are placed inside the housing with a separator that keeps them apart from each other. The fluid electrolyte is then poured inside, immersing the two electrodes. The housing is then sealed. Each cell is first tested for electrolyte leaks which may cause disastrous fires or explosions. The next step is a moisture check to see if moisture from the external environment enters the EV battery cell.

The individual cells are combined into another larger and sturdy housing to form battery modules. Specialized battery collector plates are used to create robust connections to the individual cells and aggregate the power for output from the modules. The housing is necessary to protect the cells from external shocks which may cause damage to both the individual cells and the modules. Similar leak and moisture checks are done to the module to ensure that its structural integrity is retained and can withstand environmental stresses.

A process called ultrasonic welding is used to connect copper foils to tabs in battery cells. Compared to other processes such as resistance welding and laser welding, ultrasonic welding is quick, expends little energy, and does not melt metals.  

The final stage in the assembly process is combining modules into robust battery packs. A technician manually makes the connections to the battery pack, and from it to the various systems in the electric vehicle. However, to make the seals in the pack more secure, robot arms are used to insert and tighten screws and other parts.

Promoting sustainability in manufacturing EV batteries

As an EV battery has a lifespan of between 10 to 20 years, it means that it will take two decades before the battery ultimately “dies”. It does not mean, however, that they are no longer usable once they “die”. In fact, a sustainable EV battery is what makes an electric vehicle more appealing to “green-minded” individuals.

At present, old EV batteries are brought to recycling centers to be shredded to obtain the metals contained therein, specifically aluminum, copper, cobalt, and lithium. In manufacturing EV batteries, these recycled metals can be reused in the making of new ones. 

It is also not true that all EV batteries are completely depleted of their capacity. These batteries can be reused for secondary storage of solar and wind energy.

Because of the fear of depletion of metal resources and the high cost of mining new materials, future EV battery technology is focused on reclaiming the metals that are contained in old batteries and utilizing them in the manufacture of new batteries.