You cannot get far today with electromobiles, because batteries require a lot of space. With the bipolar approach a lot more cells fit in the same car.
Depending on the model, electric cars are equipped with hundreds to thousands of separate battery cells. Each one is surrounded by a housing, connected to the car via terminals and cables, and monitored by sensors. The housing and contacting take up more than 50 percent of the space. Therefore, the cells cannot be densely packed together as preferred. The complex design steals space. A further problem: Electrical resistances, which reduce the power, are generated at the connections of the small-scale cells.
More space for batteries
Under the brand name EMBATT, the Fraunhofer IKTS in Dresden and its partners have transferred the bipolar principle known from fuel cells to the lithium battery. In this approach, individual battery cells are not strung separately side-by-side in small sections; instead, they are stacked directly one above the other across a large area. The entire structure for the housing and the contacting is therefore eliminated. As a result, more batteries fit into the car. Through the direct connection of the cells in the stack, the current flows over the entire surface of the battery. The electrical resistance is thereby considerably reduced. The electrodes of the battery are designed to release and absorb energy very quickly.
The new packaging concept could increase the range of electric cars in the medium term up to 1000 kilometers. The approach is already working in the laboratory.
Battery concept with ceramic materials
The most important component of the battery is the bipolar electrode – a metallic tape that is coated on both sides with ceramic storage materials. As a result, one side becomes the anode, the other the cathode. As the heart of the battery, it stores the energy. Ceramic materials are used as powders. The scientists mix them with polymers and electrically conductive materials to form a suspension and applie the suspension to the tape in a roll-to-roll process.
The next planned step is the development of larger battery cells and their installation in electric cars. The partners are aiming for initial tests in vehicles by 2020.
The EMBATT Project
The new battery concept is registered under the brand name EMBATT. The German Federal Ministry of Education and Research (BMBF) and the Sächsische Aufbaubank (SAB) are funding two projects. The Fraunhofer Institute for Ceramic Technologies and Systems IKTS is developing the electrode and the electrode materials, ThyssenKrupp System Engineering is manufacturing the batteries and IAV Automotive Engineering is integrating them into electric vehicles.