The material cycle of a battery cell

7 min reading time
There are four phases to the life cycle of an electric vehicle battery: development, use in the vehicle, second life and battery recycling. Join us on a journey from development at the BMW Group Battery Cell Competence Center through recycling.

22 September 2020

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Where it all begins for a battery cell

The future is created here. This is where it all begins. There is complete silence, interrupted only by the monotonous noise of the laboratory equipment. 200 scientists and experts, in particular chemists and process engineers, in their blue protective suits and turquoise disposable gloves provide the only bright spots of color at their otherwise clean, ultra-modern workplace: the BMW Group Battery Cell Competence Center in Munich, Germany. The battery cell technology of tomorrow is created on this 130,000 sq. ft. (12,000 m2) site. The technology of the battery cell and electric car battery production processes are further and further refined in these ultra-modern laboratories and research facilities. The BMW Group wants to understand exactly what happens in a battery cell, what the ideal chemical composition and design of a battery cell looks like and how it can be mass-produced while ensuring sustainability. The experts compare this to baking a cake.

The cell chemistry is the recipe, while the ingredients of the cake – which is to say the lithium-ion battery cell – are the four components: the cathode, anode, separator and battery electrolyte. It’s not just a question of getting the right quantities and quality of ingredients, but also of how you combine and prepare them, since not every oven is the same. The make-up of the key raw materials, energy and power density, safety, service life, etc. – all of this is researched at the BMW Group Battery Cell Competence Center. In this way, the laboratory can strengthen existing knowledge, track different trends for the car battery of the future and help shape that development. At the same time the BMW Group is able to lay down what battery cell formats are obtained from suppliers, using what materials, and under what conditions. The BMW Group attaches particular importance to sustainability in respect of the use of these components.

Reducing CO2 emissions

“As a pioneer on sustainability issues, our view also carries great weight among battery cell suppliers – and we do make use of that standing. We have now contractually agreed with our cell manufacturers that they will only use green electricity when producing our fifth battery cell generation. Starting this year, we will be bringing this technology onto the roads through the BMW iX3. We will then be rolling it out across our product range, with the BMW iNEXT and the BMW i4 next year, for instance. With the increasing volume, the use of green electricity will ensure that over 10 million tons of CO2 are saved within the next ten years. For comparison, that’s roughly the amount of CO2 that a metropolis like Munich emits each year,” explains Chairman of BMW’s Board of Management, Oliver Zipse. This is how the Battery Cell Competence Center creates the prototype of an automotive battery cell that will optimally satisfy the requirements of BMW vehicles both now and in the future.

Manufac­turing: the key raw materials

In its in-house laboratory, the BMW Group researches the compositions and proportions of the active materials in a battery cell. The cathode – the positive pole – currently consists of lithium-nickel-manganese-cobalt oxides. Graphite is used for the anode, the negative pole. In the extraction of raw materials – in particular of key raw materials such as lithium and cobalt – the BMW Group gives top priority to compliance with environmental standards and human rights. The company believes that ethically responsible raw material extraction and processing begins at the very beginning of the value chain: in the raw material mines. The BMW Group has therefore restructured its supply chains for the upcoming fifth generation of battery cell and will be purchasing cobalt and lithium directly (without intermediaries) from 2020 and making the raw materials available to its battery cell manufacturers.

In future, BMW will purchase its cobalt directly from mines in Australia and Morocco, along with lithium also from Australia, among other places. This will ensure 100% transparency about the origin of these two key raw materials. In addition, the BMW Group has launched a cross-sector initiative together with BASF SE, Samsung SDI and Samsung Electronics in the Democratic Republic of the Congo with the “Cobalt for Development” pilot project. The initiative aims to improve the working conditions of people in a selected cobalt mine operating small-scale mining. The companies involved have commissioned German development agency GIZ to test out, over a three-year period, how the living and working conditions in a cobalt mine operating small-scale mining and in the surrounding communities can be improved. If the project is a success, the approaches can be transferred to other small, non-industrial mines in the long term.

The life of an auto battery in the vehicle

Now begins the decisive phase in the life of a battery – its use in the vehicle. The BMW Group plans to expand its electric vehicle range to 25 models by 2023 (➜ See also: Electric cars and plug-in hybrids explained), with over half of these slated to be fully electric models. The top priority in this connection is optimizing the EV batteries for new electric cars. However, this isn’t about the size, but the technology, or rather the efficiency. The best electric car range for new vehicles is already up to 375 miles (600 km) on one charge, and the trend is upward. A car battery life span is largely dependent on the driver’s usage behavior: using a fast automotive battery charger, for example, puts more stress on batteries than a conventional auto battery charger.

The ambient temperature, number of cycles, level of discharge and the age of the battery – regardless of usage – are also factors that influence battery life. Existing expectations for the life span of a BMW battery have already been greatly exceeded. That’s why the BMW Group decided to extend the maximum mileage for its eight-year battery guarantee for a BMW i3 in Europe from 60,000 to 100,000 miles (100,000 to 160,000 km). If the automotive battery in a BMW EV has had its day after many years’ service, that certainly does not mean that it’s time for a final farewell. But what do you know with an electric car battery (➜ See also: Busting 10 myths about electric cars), when it no longer meets the requirements for driving, but still has an energy content of 70 to 80%?

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Across the 130,000 sq. ft. (12,000 m2) facility of the BMW Group Battery Cell Competence Center in Munich, the technology of the electric car battery and its production processes are further and further refined. Here, a lab worker checks the dosing and mixing of the electrode paste.
Across the 130,000 sq. ft. (12,000 m2) facility of the BMW Group Battery Cell Competence Center in Munich, the technology of the electric car battery and its production processes are further and further refined. Here, a lab worker checks the dosing and mixing of the electrode paste.
In a lithium-ion battery for a BMW battery cell, the electrodes must be coated in order to store and release lithium. To that end, a paste of active material is applied to a copper or aluminum electrode sheet.
The next step in battery cell production at the ultra-modern research facility is for the electrode sheets to be coated and dried.
This electrode sheet is then compressed in a rolling mill as the next step in the car battery production process.
Using high-tech robots at the Battery Cell Competence Center, the cell housings are then welded.
For the BMW Group, the environmental friendliness and social sustainability of raw materials, from their mining, through processing and all the way through to their recycling after use, are crucial.
The BMW Group Battery Cell Competence Center in Munich, Germany. Research is carried out here into the lifespan of EV batteries, lithium battery recycling and how to ensure the sustainability of raw materials through re-use.

An 85 x 20 ft. (26 x 6 m) container at the northern German Port of Hamburg demonstrates why you should not judge by appearances. It’s all going on inside. There are 2,600 battery modules that have been given a second life after being used in BMW EV batteries. These battery cells have found a new purpose as stationary energy storage devices. The cumulative power from these cells is available within seconds and keeps the energy grid stable. What does that mean exactly? Well, throughout the day (and night), the amount of electricity fed into the grid is based on the estimated demand from all consumers. A forecast is made every 15 minutes and it is then determined which power generation systems can meet the demand. In many places, priority is given to generation from wind and solar power, but such power is weather-dependent and therefore not 100% predictable.

“That’s where battery storage systems like the Second Life one come into play,” explains Daniel Hustadt, project manager at the energy producer Vattenfall with responsibility for technology development. “They are there to compensate for precisely those fluctuations so as to guarantee a balance between supply and demand. If there is too much electricity in the grid due to fluctuations in production or demand, the batteries store the surplus. If there is a shortage of power, the batteries supply it. And they do it within a few seconds!,” he enthuses. It takes about ten years to completely exhaust the energy content of a battery cell in “second life” use, at which point it is then recycled. The storage farm at the BMW Group plant in the German city of Leipzig similarly demonstrates that around 700 BMW i3 batteries can still enjoy an effective life after they have served their time in a vehicle. As buffer storage for renewable energies, they also help to store electricity and reduce energy costs for sustainable production.

A deafening noise fills the hall. Using milling machines, three workers open up the battery modules in order to penetrate down to the highly valuable layers in which the raw materials are located. Next, the aluminum shell, the electrode material and the separator membrane are ground into tiny fragments in a special shredder. The shredder is operated using the electricity discharged from the battery and can shred up to 1100 lbs (500 kg) of material per hour. We find ourselves at the center of the chemicals firm Duesenfeld in the German state of Lower Saxony. It is one of a number of companies, alongside others including Northvolt and Umicore, that is able to almost completely recycle the lithium-ion EV batteries from the BMW Group’s electric vehicles.

Various methods are used. Alongside shredding, a battery cell can also be heated at very high temperatures in a furnace in a pyrometallurgical process in order to melt and separate out the metals contained inside. Electromobility can only be considered to have achieved sustainability if the batteries used are recycled. The material cycle is closed to the best possible extent through extensive recycling of the raw materials. And that brings us back to where it all began for the battery: the BMW Group Battery Cell Competence Center. Because even when developing a battery cell, BMW is already thinking about sustainability in terms of the re-use of raw materials after the recycling process. The cycle is complete.

Photos: BMW; Illustration: Bratislav Milenkovic; Author: Markus Löblein