MAN Truck & Bus
MAN Truck & Bus
Giving lithium-ion batteries from vehicles a second life
The number of electric vehicles is substantially increasing. On the one hand this is good for the climate, because it reduces the CO2 emissions caused by road traffic. On the other hand though, it creates a new challenge: there is still no final solution regarding the disposal or recycling of vehicle batteries. Dr Johannes Öhl from the Fraunhofer IWKS gives an overview of the options available so far.
is a manager of the AutoBatRec2020 project and spends his time at the Fraunhofer Research Institution for Materials Recycling and Resource Strategies (IWKS) recycling the batteries from electric vehicles.
Öhl Disposal of the battery components in lithium-ion batteries is in fact seldom required, since they contain valuable materials like cobalt. It’s rather a question of reuse, either of entire components or of individual substances. The challenge here is to disassemble the individual materials by type, because only then can they be reused. This makes the process time-consuming.
Öhl It’s the mixture of substances that makes recovery so difficult, for instance in the active material of lithium, nickel, cobalt and manganese. Some of the materials can pose hazards if they come into contact with water or if dust particles are generated. That is one reason why the batteries can only be shredded under certain conditions. Separation of the individual materials by type is moreover a major challenge due to their nature, such as aluminium and copper foils or the fine powder active materials.
Öhl Until now there is no alternative to using these substances in battery manufacture. There is however a lot of research being conducted into how we can do without some harmful substances in the long term. In Europe, for example, the proportion of potentially carcinogenic cobalt in electric batteries has fallen by around 30 per cent in recent years – also due to cost reasons.
Öhl There are three possible phases here, also known as re-phases. The first phase involves reuse, where batteries still in working order are installed in another vehicle. This is possible if the vehicle is defective, but the battery is intact. Especially in the automobile sector, an electric battery is only ultimately removed from the vehicle if it has less than 80 per cent charging capacity. Current knowledge suggests that this is the case after around ten years on average. But even then it can certainly still be used, for example as part of a battery storage concept. The second phase is second use, also known as re-manufacturing. Only when this is no longer possible is the battery really disassembled into its individual parts and the materials recycled.
Öhl The essential advantage of second use after life in a vehicle is that it significantly delays the point at which the batteries have to be subjected to costly recycling. The most common example of second use is in stationary energy storage units. This involves batteries from electric vehicles being combined into a large-scale storage unit. The fact that a single battery has less charging capacity is then no longer a factor. These batteries can subsequently be used as a power store that compensates for fluctuations in the electricity grid, for example. Once an individual battery is no longer performing adequately, it can be replaced and sent for recycling.
Öhl If a vehicle battery is no longer usable – because its charging capacity is inadequate or because it is damaged – it is disassembled into its constituent parts. At Fraunhofer IWKS, for example, we are developing particularly efficient methods for separating the materials by type. The more pure-grade materials we recover, the greater the proportion of recycled materials that can be reintroduced into battery production. Our long term aim is to return all components to the cycle.
Öhl Should we succeed in extracting the individual components much more effectively than to date, the costs of recycling will reduce over the coming years. Firstly due to time savings and secondly because ultimately more components can be reused. The recycling volume will also increase in the near future due to the rising number of electric vehicles. This means that the respective recycling plants will be better utilised and can work more economically.
Öhl Ultimately every battery will have to be recycled once it has passed through all the re-phases. We can however attempt to delay this step as far as possible by conserving the battery during its use phase. Each charge and discharge process places a mechanical load on the battery that reduces its performance. It can help to never charge the battery to the limit, but rather to around only 80 per cent on each occasion. Charging capacity also has an impact on service life – the more rapidly a battery is charged, the worse that is for its service life.
Together with Verkehrsbetriebe Hamburg-Holstein (VHH) and Volkswagen, MAN is implementing a pioneering pilot project in Hamburg for the reuse of electric batteries. At the VHH bus depot, 50 batteries that were previously installed in VW Passat GTEs were combined to form a stationary battery storage system. For this purpose, they were mounted on racks and interconnected to form a large-scale battery. The storage system is used to test and optimize various scenarios at the bus depot. For example, the battery storage system cushions peak loads when charging electric buses (peak shaving). In addition, the pilot project will provide insights into the aging behavior of the batteries.