Put simply, a battery consists of four main components: cathode (negative pole), anode (positive pole), separator and electrolytes. The liquid electrolytes between the two poles ensure that the ions move back and forth between the anode and the cathode – depending on whether the battery is being charged or discharged. Electric vehicle batteries, also referred to as traction batteries, are composed of several interconnected individual batteries that in turn consist of battery cells or cell blocks connected in parallel and in series. The traction batteries of most electric vehicles supply a voltage of 400 volts, while the Porsche Taycan has an 800-volt system.
Batteries for electric vehicles must be as light and small as possible, but at the same time powerful and durable. Modern electric vehicles therefore mainly use lithium-ion batteries and rarely lithium-polymer ones, and electrolyte liquid is used for lithium-ion batteries and polymer gel for lithium-polymer ones. In relation to other batteries, they have the highest energy density, and can store the most energy per kilogram of net weight. They also have a low self-discharge rate if a vehicle is not driven for an extended period, for example.
The nickel-cadmium battery is considered the predecessor of the lithium-ion battery. While the former is robust, deals better with temperature fluctuations and charges faster, it is no longer used in vehicles because of its poor environmental performance. Cadmium is a heavy metal and is toxic to the environment. On top of this, nickel-cadmium batteries should only be charged when completely empty, which is an unsuitable characteristic for electric vehicles. In addition, the self-discharge rate of nickel-cadmium batteries is relatively high.
As in any car with a combustion engine, an electric vehicle still has a small 12-volt battery installed, helping to start the electric motor and providing power for the central locking, interior lights, instruments and power steering. In many electric vehicles, manufacturers use exactly the same lead batteries as in models with combustion engines. However, lighter lithium-iron-phosphate batteries are increasingly being used instead of lead batteries in higher-class electric vehicles.
The pros and cons of the lithium-ion battery at a glance:
+ high energy density
+ long service life
+ low weight
– high production costs
– complex battery management
– cooling required
– questionable raw material production
Mobility will always have a certain impact on the environment. The goal, however, is to reduce the burden on people and the environment and keep it as low as possible. Vehicle production requires energy and raw materials. When it comes to electric vehicles, the focus is above all on the production of batteries, which require cobalt and lithium in addition to nickel and manganese. Around two thirds of the world’s cobalt – a lustrous, silver-grey metal that is hard and strong – is mined in the Democratic Republic of the Congo (DRC), partly under inhumane conditions and by children. Around 95 000 tonnes of cobalt came from the DRC in 2020. The second largest producer by a wide margin was Russia with 6300 tonnes, ahead of Australia with 5700.
Sustainable mining in the developing country of the DRC is a long-term challenge. Throughout the value chain, the Volkswagen Group participates in sustainability initiatives such as the Responsible Minerals Initiative (RMI) and the World Economic Forum’s Global Battery Alliance. On top of this come internal targets and checks along the supply chain, which are simplified by increased transparency thanks to the direct sourcing of materials.
The RMI is in the process of developing a certification system for cobalt smelting to improve mining conditions and ensure traceability. With this aim in mind, the Drive Sustainability working group is working on standardised monitoring instruments and sustainability training for suppliers.
Achieving a significant reduction in the cobalt content of the lithium-ion battery is also extremely important, with the target being a drop in the share of raw material in the cathode’s weight from 12 or 14 per cent to 5 per cent by 2023/2025. Volkswagen is also working on the development of battery cells that do not need any cobalt at all.
Maximilian Fichtner, professor and expert in battery technology at the University of Ulm and the Karlsruhe Institute of Technology, believes that a complete phaseout of cobalt is both feasible and necessary: “Not only because of the human rights issue, but also because of the limited reserves.” A good alternative is already available, he says: lithium iron phosphate. “This material is cost-effective, sustainable and non-toxic,” he continues. Galaxite, also known as mangan-spinel, could also be an option.
Lithium is extracted primarily from salt lakes in South America – Chile, Argentina and Bolivia in particular – by means of evaporation. This process is not without its drawbacks: groundwater is needed for lithium production, which may result in drying out the surrounding landscape. This is an issue that affects many indigenous peoples. For many experts, however, it is unclear whether and to what extent the drought is actually related to lithium mining. What is clear is that drinking water is not needed for lithium extraction. For Maximilian Fichtner, no convincing replacement for lithium has emerged as yet. “However, I also see this situation as much less critical, because global lithium reserves will last considerably longer than those of cobalt,” he explains. There are alternatives to lithium extraction from salt lakes – ore mining, for example – and all of Volkswagen’s lithium suppliers are contractually obliged to observe high environmental and social standards.
Solid-state batteries are said to have around twice the range and to be much safer than current lithium-ion batteries, which is why they are seen as the future of electric mobility. These are lithium-ion batteries but without the liquid electrolytes, meaning that they do not leak and are highly unlikely to catch fire. This avoids the need for costly fire protection and temperature management, making solid-state batteries lighter and less expensive as a result. Another advantage is that they can be charged much faster than current lithium-ion batteries – in about half the time.
Volkswagen plans to build its own solid-state battery factory in Salzgitter, Germany, with its US partner Quantumscape.
The pros and cons of the solid-state battery:
+ no liquid, not flammable
+ no discharging
– weak current
– lithium is used here too, so the negative environmental aspect continues to apply
On behalf of the German think tank “Agora Verkehrswende”, the Institute for Energy and Environmental Research (ifeu) in Heidelberg conducted a study entitled “Klimabilanz von strombasierten Antrieben und Kraftstoffen” (“The carbon footprint of electricity-based drives and fuels”, available in German only) in 2019. The study involved comparing batteries, fuel cells and e-fuels, and the key findings are as follows:
• In order for the carbon footprints of electricity-based drives and fuels to provide comparable and reliable results, it must be ensured that the same assumptions are made regarding energy supply.
• In the carbon footprint of a fuel cell vehicle powered by electrolytically produced hydrogen from the German electricity mix, the greenhouse gas emissions are 75 per cent higher than those of a battery electric vehicle with 35 kWh battery capacity. When compared with a battery electric vehicle with 60 kWh in pure motorway driving, the emissions are 56 per cent higher.
• Carbon footprint: For a vehicle with a combustion engine that runs on electricity-based liquid fuels from the German electricity mix, the greenhouse gas emissions are around three times higher than for a battery electric vehicle with 35 kWh.
• If hydrogen or electricity-based fuels in transport are to help protect the climate, it must be ensured that only wind or solar power from surplus capacity is used in their production.
The Volkswagen Group offers a warranty of eight years or 160 000 kilometres on the high-voltage battery of an electric vehicle. Most batteries will even outlast the vehicle itself by several years. Should a fault nevertheless occur, the affected components can be diagnosed and replaced individually, thereby avoiding the need to replace the entire battery pack. Work on high-voltage batteries is carried out at special support centres by a high-voltage expert (HVE) in special protective equipment.
Extending the life of a battery plays a central role when it comes to the environmental friendliness of e-mobility. The primary goal must be for batteries to be repaired or reconditioned, or passed on to second-life projects for complete reuse. There is a large number of second-life large-scale storage projects within the Volkswagen Group, for example, where used vehicle batteries are combined and used as one huge battery – both in Volkswagen plants and in cooperation projects with utility companies and towns and cities. The service life of a battery can be extended significantly by such further use.
In addition to reuse, i.e. further use outside the vehicle, remanufacturing is another option: the used batteries are reconditioned for use in electric vehicles by replacing individual components. Alternatively, a battery that has been divided into its individual modules can also be reused in stationary storage systems.
What happens to the batteries when they reach the end of their lives? The Volkswagen Group’s Research and Development department has found a recycling solution, and has worked with Volkswagen Group Components to prepare it for series production. The solution is an innovative and sustainable process for recycling batteries, and is being used for the first time in a pilot facility at the Salzgitter site in Germany. The goal is to recycle more than 90 per cent of the battery and return materials such as cobalt, nickel, manganese and lithium to the cycle. In Switzerland, a national solution may be possible.
Only batteries that can really no longer be used in any other way are recycled. Before this, they are first checked to see whether they are still fit to be given a second life in mobile energy storage systems such as flexible fast charging points and charging robots. This enables their useful life to be significantly extended.
The Paul Scherrer Institute has developed the “Carculator” web tool that makes it possible to compare the life cycle assessment of various cars. The programme determines the life cycle assessments of vehicles with different types of drive, and presents them in the form of comparative graphics. The entire life cycle of passenger cars is taken into account, including the production of the vehicles and the environmentally relevant emissions produced while driving. Any measures and carbon offsets carried out by manufacturers during production – such as Volkswagen Group’s efforts to deliver the ID.3 to customers in a carbon-neutral manner – are not taken into account, however.