How Nissan Makes its Electric Car Battery Packs, Part One of Three: On Being Super-Clean

They’re in pretty much every consumer electronics gadget you can think of, have evolved at an astonishing rate in the last ten years, and are so important to the future of the electric car that Tesla Motors is building a $5 billion manufacturing plant outside Reno, Nevada devoted to their construction, development and reprocessing.

This battery pack is nearing completion, but we're going to go right back to the start of making a Nissan LEAF battery pack.

This battery pack is nearing completion

We are of course, talking about lithium-ion batteries, the unseen, under-appreciated super vessels which store the electrochemical energy needed to keep our laptops running, our smartphones charged and of course, our plug-in cars moving.

But how are lithium-ion batteries made, and just what processes must an electric car battery pack go through in order to be ready to provide miles and miles of all-electric use? 

To find out, we were among some of the first journalists in the world to be welcomed to Nissan’s top-secret battery production facility in Sunderland, England, where Nissan manufactures some 60,000 lithium-ion battery cells every year for use in its Nissan LEAF and Nissan e-NV200 electric vehicles.

But in order to describe our experiences — and accurately detail the long and complicated process of making battery cells and battery packs from scratch, we’ve decided to split our report into three separate articles.

Today, we’re going to deal with the physical battery production facility and the extraordinary lengths Nissan goes to keep its battery production facility clean and clear of any contaminants. Tomorrow, We’ll describe how Nissan turns raw sheets of anode and cathode material into functioning battery cells and on Thursday, we’ll describe how those cells make their way into the battery modules and ultimately the battery packs used in every Nissan electric vehicle.

Nissan's battery plants are as clean as a microprocessor factory.

Nissan’s battery plants are as clean as a microprocessor factory or NASA facility.

When we’re done, we think you’ll appreciate electric car batteries just a little more, and understand a little more why we heaped praise on the humble lithium-ion cell at the start of this article. So read on, and be sure to come back later on in the week for parts two and three.

One of Three

Located on the outskirts of Sunderland in the North of England, Nissan’s specialist battery manufacturing facility is one of three Nissan-operated lithium-ion battery manufacturing plants around the world. Like its counterparts in Smyrna, Tennessee and Oppama, Japan, Nissan’s Sunderland battery facility is housed in a specially-constructed high-tech building next to the production lines where Nissan produces the relevant North American, Asian and European LEAF models respectively.

In the case of Sunderland’s battery production facility however, some of the battery cells and modules produced are sent to Barcelona, Spain, where the sealed and tested battery modules are assembled into battery packs for use in Nissan’s e-NV200 electric van.

Staffed by highly-trained workers, Nissan’s battery production facilities are part high-tech, part highly-skilled staff. Split into smaller sections, the battery plants first build the battery cells themselves in contamination-free clean-room conditions. Once each cell has been sealed, it is then passed onto module assembly, where the cells are stacked in groups of four to produce a battery module. The final part of the assembly process takes place on a more conventional-looking production line, where finished modules are assembled in strings, mechanically and electrically connected, and housed in a completed battery pack alongside all the other important electronics that enables the pack to communicate with the car’s on-board computer system and transfer power into and out of the pack.

As Clean as a NASA Facility

Nissan, in order to retain control of every part of the battery manufacturing process, manufactures all of its lithium-ion battery packs from scratch, bringing in the raw materials at one end of the battery facility and finished battery packs out the other.

Not all parts of Nissan's battery facility are in clean-room conditions, but a large portion is.

Once cells have been sealed and built into modules, the factory looks much like another mass-production facility.

In dealing with the raw materials that make up each and every lithium-ion battery cell however, Nissan’s facilities have to go to extreme lengths to ensure that no contaminants enter into the cell production process at either the visible or microscopic level, since impurities in battery cells can cause anything from internal short circuits through to premature ageing and incorrect operation. And everything from moisture to skin, lose fibres and even certain gasses are considered enemy contaminants which must be eliminated and contained appropriately. 

As a consequence, some parts of Nissan’s Lithium-ion battery facilities — namely ones stages before the battery cells are sealed in an air-tight vacuum process — look more like a high-tech NASA facility or the ultra-sensitive production facilities where the likes of Intel, Apple and AMD make computer chips than they do a car production plant. Entry is carefully controlled in and out of the facility, no external devices are allowed within the plant’s various clean rooms, and everything from temperature to humidity is controlled with a degree of accuracy that would make your average surgical theatre look like a barn.

Constructing a clean room facility, we were told, was far more complicated and controlled than a standard factory construction project. After initial ground-work was done, Nissan required its contracted construction crews to slowly increase the use of clean-room practices. While initial groundwork was carried out with the standard hard hats and work boots of any other construction site, construction crews slowly began to adopt the use of clean-room clothing as construction neared completion. By the time Nissan was installing all of the high-tech production equipment used to build the battery cells and battery modules, all of its construction and machine installation crews were following strict clean-room procedures.

In building the factory, Nissan's construction workers and maintenance staff had to follow clean-room practice.

In building the factory, Nissan’s construction workers and maintenance staff had to follow clean-room practice.

In the case of the Sunderland plant, that included building a specialist annexe airlock on the side of the plant where the large manufacturing equipment — still in their double-layer, hermetically-sealed protective cases — were thoroughly cleaned and decontaminated before entering into the clean-room atmosphere of the factory. Only once the equipment had been installed did final decontamination occur — an arduous process where every corner of the facility from top to bottom and back to front was cleaned from top to bottom — and the facility was ready to produce lithium-ion battery cells.

Even with the facility in full production, Nissan has a dedicated team of specialists whose jobs are specifically to ensure clean-room conditions are maintained at all times — and to pinpoint the source of any which do enter.

The bunny suit

Just as any other person entering into Nissan’s inner-sanctum of the lithium-ion cell clean room, those of us touring the facility had to don an all-over clean room suit, colloquially known as the ‘bunny suit.’ Comprising face mask, hood, overalls, boots and gloves, the clean room suits are not only an unusual social equaliser (you can’t always see who is underneath the hat and mask) but also come in their own specially-sealed, single-use bags.

Yes, even journalists from Transport Evolved have to look silly.

Yes, even journalists from Transport Evolved have to look silly.

To enter the clean locker room, where workers and visitors alike prepare to enter the clean room, you first have to enter into an outer locker room area where external coats, and shoes are left and plastic bags are placed over stockinged feet. From there, a short walk through carefully-controlled corridor leads you into the clean locker room.

Despite its apparent cleanliness, one side of the room is termed the ‘dirty’ side, while other side of the room is the ‘clean’ side. In the middle lies a full-length foot-high bench. Step out of the protective plastic foot covers on one side, and step over the bench to begin the robing process.

First comes the face mask. Like a surgical mask, the face mask covers the nose and mouth, and is tied at the back of the face with two ties. Next comes the hood, a full-face affair which covers hair, ears, nose and neck. With just enough of a space to see out of, this is the only exposed area in the whole of the clean room suit, and is tightened around the wearer’s face with a series of three pull tabs.

With mask and hood on, next comes the full-length coveralls, also sealed into their own sterilised bag. White in order to easily show up any contaminants, the coveralls fit over the wearer’s regular clothes, and provide the majority of body coverage needed to keep the clean room safe from outside contaminants. Before zipping the coveralls shut, the long hood is tucked inside the coveralls to provide seamless coverage from head to ankle. Next comes all-white clean-room boots and one-use latex gloves, which cover both arm and leg cuffs to ensure zero contamination.

If we’re honest, we’d say the experience of putting on the bunny suit wasn’t exactly pleasant. In fact, we can understand how some would find it claustrophobic. Yet Nissan’s specialist battery cell workers don their clean room suits for 8-hour shifts, five times a week like the rest of Nissan’s production staff. In that 8-hour period, workers get two official breaks where they can leave for refreshment and the call of nature.

Air shower

Once all appropriate clothing has been donned, the clean room can be entered via a special airlock. Large enough for three people at a time, the air lock features a high-pressure air shower system which ensures any lose particles on the outside of the clean room suits are carefully removed and captured by the sophisticated air filtration system before entry into the cell production facility.

The reason Nissan's facility has to follow clean-room practices: the raw materials used in cell production must be free from contaminants at all costs.

The reason Nissan’s facility has to follow clean-room practices: the raw materials used in cell production must be free from contaminants at all costs.

Like the rest of the air conditioning system in the facility — including the clean room and the dressing room — Nissan says the air lock system is pretty much self-cleaning, effectively removing any outside contaminants before they have a chance to cause any issues to either battery production or air conditioning operation. Since the air lock is a small, confined space, the air showers are extremely effective in providing a final level of protection between the outside world and the inner sanctum of the facility. Only once the air showers have been run and all contaminants removed does the inner door open and access granted to the facility.

Tomorrow, we’ll cover the basics of the clean room, detailing how the raw anode, cathode and separator materials are cut to the appropriate size and layered to form battery cells before being injected with electrolyte, gassed and sealed, so be sure to come back tomorrow to find the next step in building Nissan’s electric car battery packs.

Nissan provided train fare and  hospitality to enable Transport Evolved to bring you this first-person report. Due to restrictions on bringing external ‘dirty’ equipment into the clean room area, all photographs in this article were taken by official Nissan photographers.



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