PolySafe: Making Lithium-Ion Batteries Safer Research project on metal-polymer current collectors to increase the safety of lithium-ion batteries
The aim of PolySafe is to increase the specific energy and safety of lithium-ion batteries by using novel current collectors. The focus is on metal-polymer composites, which significantly reduce the risk of thermal runaway of a cell and thus the risk of fire. In addition to Battery LabFactory Braunschweig of Technische Universität Braunschweig, partners from research and industry are involved in the project, which is funded with almost four million euros.
Current collectors are thin metal foils with good conductivity, which are coated with the electrode components. This also includes the active materials that ensure the electrochemical functionality of the cell. In addition to the weight savings compared to plain metal foils used today, the metal-polymer current collectors are interrupting the circuit when a critical temperature is reached. The current collector melts, interrupting the current flow and thus the short circuit.
The feasibility of manufacturing the metal-polymer electricity collectors has already been demonstrated jointly by VON ARDENNE GmbH and Fraunhofer FEP as part of the Saxon research project PolyCollect. Using the physical vapor deposition process, aluminum layers up to 1 micrometer thick could be produced on polymer substrates with thicknesses up to 8 micrometers. However, there is still insufficient data from prototype cells with this material, which is why the application-oriented evaluation of this technology is still pending. This will be done within the framework of PolySafe. The aim of the research project is to qualify a process chain adapted to the metal-polymer current collectors to produce battery cells in different formats (round cell, pouch cell) and to investigate the safety advantage in different cell designs and chemistries in an application-oriented manner.
In addition to integrating the manufactured metal-polymer current collectors into battery cells, the consortium wants to adapt and optimize aluminum or copper-polymer current collectors to the requirements of the respective cell design. The challenge is to design the polymer substrates and the coating process in such a way that a thickness comparable to that of current metal foils and optimum electrical conductivity of the metal layer are guaranteed. At the same time, the production costs of the current collectors are to be brought to a competitive level.
The Battery LabFactory Braunschweig (BLB) of TU Braunschweig contributes its expertise on the production process and characterization of electrodes and pouch cells for lithium-ion batteries. The metal-polymer current collectors are investigated regarding their suitability for integration into the production processes of lithium-ion batteries and – if necessary – production processes are specifically adapted.
Responsibilities of the partners
VON ARDENNE GmbH will coordinate the PolySafe research project. In addition, the Dresden-based company will – based on the results of the technological development at Fraunhofer FEP – contribute its know-how to the technical conception of a production plant for the deposition of the metal layers that meets both the technological and the economic requirements for a production of metal-polymer electricity collectors.
Brückner Maschinenbau GmbH & Co.KG is working on the development of polymer films that are adapted to the requirements of both metallization and battery applications. The aim is to develop innovative polymer substrates and surface treatments and scale them up to roll scale. The most promising materials will be made available as substrates for metallization.
Fraunhofer FEP scientists are developing a suitable technological process control for the deposition of aluminum and copper layers in a roll-to-roll process. The aim is to holistically understand the influence of parameters of the strip run, substrate pretreatment as well as metal evaporation and to develop optimal process settings to achieve the technological and economic requirements.
The Fraunhofer IST is researching the suitability of metal-polymer current collectors for novel battery cell generations, with a particular focus on the lithium-metal anodes. A particular focus will be on the manufacturing steps of the lithium metal anodes and the resulting cells
VARTA Microbattery is responsible for the integration of the new electrodes with metal-polymer current collectors in full cells and the standard-compliant safety testing. In particular, the processing and safety of round cells with metal-polymer current collectors will be investigated and compared with pure metal foils.
About Battery LabFactory Braunschweig (BLB)
The Battery LabFactory Braunschweig (BLB) of the TU Braunschweig is a transdisciplinary center that links 14 institutes for holistic research and development of battery electric storage technologies and covers the entire value-added cycle from material production to cell manufacturing to recycling to close the material cycle.
In a “Joint Pilot Facility”, the electrode and cell production as well as the cell conditioning will be mapped in technical, automated processes on a pilot to pilot scale (battery technology platform 1000 sqm including 200 sqm drying room, in addition 700 sqm equipment for analytics and post-mortem analysis), so that defined cells can be produced on a large scale for battery demonstrators. The project will specifically incorporate i) the process and product expertise in electrode production that has been established since 2007, ii) the expertise in manufacturing, joining and handling technology in the area of cell assembly, packaging and contacting, iii) methodological expertise for energy-oriented modelling and life cycle assessment, and iv) elaborate procedures for forming and cyclisation for cell conditioning as well as diagnostic methods.
PolySafe is a research project to increase the safety of lithium-ion batteries using metal-polymer composite current collectors and is funded by the German Federal Ministry of Education and Research (BMBF) with around four million euros (funding code 03XP0408E). The project started in August 2021 and will run for three years. In addition to the TU Braunschweig, the following companies are involved: VON ARDENNE GmbH (coordination), Brückner Maschinenbau GmbH & Co. KG, Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, Fraunhofer Institute for Surface Engineering and Thin Films IST, and Varta Microbattery GmbH.