Project examples in battery research at Fraunhofer

The Fraunhofer Battery Alliance, as part of the Fraunhofer-Gesellschaft, is active with its 19 institutes in every area of battery research. The goal of the initiative and projects is to lower the production costs of batteries, to increase their energy density based on innovative material combinations and new cell designs, and to make batteries and the scenarios for their application safer. Below we will be presenting several projects.

Materials research for higher energy densities

MAVO “LiScell” – Higher energy density using silicon anodes

As part of the MAVO LiScell project, battery cells based on new cathodes, electrolytes and anodes are being developed. As well as developing materials, scalable manufacturing processes are also under consideration. With regard to this point, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has developed a new vacuum coating technology. Coats of silicon with a special microstructure are laid down using the so-called roll-to-roll process on both sides of the copper power collector foil. This innovative anode material provides a significant improvement over standard solutions for both lithium-sulfur and lithium-ion cells. Furthermore, this scalable coating technology is particularly cost effective.

“SePaLiS” – Lithium-sulfur increases energy density

The high energy density of the lithium-sulfur battery compared to the lithium-ion battery makes it an attractive technology, because it provides the potential for greater range for electric vehicles. The use of sulfur as an electrode material also considerably lowers material costs. A particular challenge posed by lithium-sulfur batteries is their short lifespan, which is why they have not yet been introduced. Therefore research into electrolytes, separators and the electrodes, as well as an appropriate cell design, is absolutely essential in order to establish the lithium-sulfur battery in the market. The electrolyte amount and decomposition, the coating of the separators, the sulfur saturation and decomposition of the lithium anodes all play a decisive role here. In the “SePaLiS” project, together with its partners, the Fraunhofer Institute for Material and Beam Technology IWS is working on concepts for separators, cathodes and cell designs with the aim of developing a prototype cell for automobile applications with an energy density of 400 Wh/kg and a lifespan of 500 cycles.

Fraunhofer IWS, Center Battery Research

New battery technology

Production of the bipolar electrode on a pilot scale.
© Photo Fraunhofer IKTS

Production of the bipolar electrode on a pilot scale.

“EMBATT” – Greater energy density and range as a result of stack construction

The Fraunhofer Institute for Ceramic Technologies and Systems IKTS is working together with industrial partners on the “EMBATT” project to develop materials and processes to efficiently manufacture a large-format bipolar battery. The aim is to improve the energy density of batteries by constructing bipolar electrodes. To this end, the battery components are stacked in such a way so as to eliminate the laborious packing and connecting of the individual cells, and resistance within the stack is reduced. This way, the higher energy density at the cell level can be transferred directly to the stack and so to the entire battery system. Cathode materials with defined specifications are required for this stacked construction, and the Fraunhofer IKTS is developing this part of the project. The experts are also currently working on other battery components, such as anodes, electrolytes and conductor foil, as well as seals for the bipolar stack design. It is hoped that the EMBATT technology will deliver a high energy density of 450 Wh/L at the system level, at a planned production cost of <200 €/kWh. In the future, this could allow electric cars to achieve ranges needed for everyday use. This will make an important contribution to the success of electromobility.

“MASAK” – Magnesium sulfide rechargeable battery for energy storage

It is possible to avoid the rare or poisonous (and therefore expensive) materials which typically make up lithium-ion batteries through the use of alternative materials. In the “MASAK” group project, the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM is researching high-performance rechargeable batteries with a high energy density not based on lithium. Instead of lithium, the project researchers are using magnesium as an electrode material and are developing magnesium sulfide batteries. This makes magnesium sulfide batteries a cost effective alternative that is likely to achieve 150 Wh/kg in practical use.

Energy Storage - Research for Energy Transition

Cell production

“Cell-Fi” – Optimized electrolyte filling by simulation

Once battery cells have been assembled, they still have to be filled with electrolytes before they can be charged and discharged. The electrolyte’s purpose is to transport the ions within the cells, so it is crucial for the battery to function. In order to take full advantage of the capacity of the batteries, the electrolyte must be evenly distributed in the cell and connect all of the components. This process depends on the design of the cell and is still not entirely understood. This is why the Fraunhofer Institute for Industrial Mathematics ITWM, in cooperation with the group project “Cell-Fi”, is carrying out simulations of electrolyte filling methods leading to efficient procedures for cell manufacture with a view to saving time and, hence, money in battery manufacturing.

Fraunhofer ITWM, Department Electrochemistry and Batteries

“FlexJoin” – Flexible production of battery modules

As yet, there is no standard battery for electromobility. Every automobile manufacturer is pursuing its own concept, and is adapting batteries on an individual basis to fit the relevant vehicle. Hence the batteries differ in terms of their size, shape and cell chemistry. This means that for each battery type, different production methods and lines are needed, resulting in the high cost of today’s batteries. The Fraunhofer Institute for Laser Technology ILT is working together with its partners on the “FlexJoin” project, to develop universal manufacturing technology. Here the key to success is the bringing into contact or bonding of the individual cells. By applying laser technology and the relevant software controls, the cells can be individually welded together; this makes the battery manufacturing process very flexible. To apply the process in an industrial setting, both standardization and a catalog of applications will be created as part of the project.

Fraunhofer ILT, FlexJoin

“LoCoTroP” – New production technologies for cost savings

Solvent-based processes represent the state of the art in the production of battery electrodes. Following the coating of the electrodes, the solvent must be evaporated and reclaimed using laborious, costly drying processes. To save on these costs during production, the Fraunhofer Institute for Manufacturing Engineering and Automation IPA, together with its partners, is conducting research as part of the “LoCoTroP” project into dry coating processes for battery electrodes, looking to develop low-cost, energy efficient, environmentally friendly processes.

Battery systems

The redox-flow large-scale battery storage unit has been set up on Fraunhofer ICT land in Pfinztal.
© Photo Fraunhofer ICT

The redox-flow large-scale battery storage unit has been set up as a pilot plant on the Fraunhofer ICT premises in Pfinztal.

In the lab at Fraunhofer ICT, the materials for redox-flow batteries are being researched and developed.
© Photo Fraunhofer ICT

In the lab at Fraunhofer ICT, the materials for redox-flow batteries are being researched and developed.

The new test bench at Fraunhofer LBF combines mechanical vibration and electrothermal stresses to create a realistic stress profile.
© Photo Fraunhofer LBF

The new test bench at Fraunhofer LBF combines mechanical vibration and electrothermal stresses to create a realistic stress profile.

Redox-Flow: Rechargeable batteries with external tank

Redox-flow batteries are of particular interest in stationary energy storage applications. Due to the storage of energy in an external tank, the performance of the battery can be scaled independently of capacity. In addition, the redox-flow batteries are very efficient and potentially last longer than standard rechargeable batteries.

The Fraunhofer Institute for Chemical Technology ICT is involved with the development of redox-flow batteries based on zinc-bromine and hydrogen-bromine. In the context of the “RedoxWind” project, a large-scale redox-flow storage unit was built with 2 MW and up to 20 MWh, coupled with a 2 MW wind turbine in order to store renewable wind energy. In this application center, we are researching the battery periphery and infrastructure for connecting this type of storage unit to the power grid.

“InTeLekt” – Electric cars can never be reliable without power electronics

In an electric vehicle, the power electronic components control the power supply of the battery, the drive unit and the onboard electronics. As such, they are subject to significant mechanical and electrical stresses during day-to-day use in electric vehicles. These can limit the reliability and lifespan of components. That’s why the partners involved in the “InTeLekt” project are working to develop a new, integrated check and test environment for power electronics, with a view to making them both safer and more reliable. To do so, a new simulation environment is being developed, which will mean that the reliability and lifespan of power modules can be evaluated more rapidly. The Fraunhofer Institute for Structural Durability and System Reliability LBF is playing a major part in this project.

“MiBZ” – Intelligent cells for electromobility and stationary storage

As well as electromobility, stationary energy storage is increasingly gaining in importance to guarantee supply security. An interesting approach for a longer useful lifespan for batteries is so-called “second use”. After five years, batteries designed for electromobility no longer offer the energy density needed, but they are still nowhere near being out of order and can normally continue to be used for other applications such as in stationary energy storage. For this kind of purpose the batteries do not require very high energy density. What is much more crucial is that they are still reliable and can safely function for many more years. To research this application concept, the “MiBZ” project looks at the integration of electronics and sensors into the battery cells and the battery systems in order to develop multi-functional, intelligent lithium-ion batteries. This means that the batteries can be continuously monitored, the state of their cells determined, and high levels of safety guaranteed. The Fraunhofer Institute for Integrated Systems and Device Technology IISB is a Partner in this project.

Fraunhofer IISB, Energy Electronics