The energy transition to sustainable technologies confronts us with great challenges but although brings fascinating opportunities. Among these opportunities lies the battery technology, which is considered the heart of electromobility and renewable energy storage. A strategic focus on the future of battery production is essential for progress in these areas and for national value creation.
One leading research center in this field is the Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW) in Ulm. The ZSW has been involved in battery production and process research for many years, with the aim of improving the efficiency and performance of batteries and their production.
The research spectrum of the ZSW in Ulm is unique. ZSW offers all process steps for the development and production of lithium-ion cells in various standard formats. These include 18650 and 21700 round cells, single and multiple stacked pouch cells, and prismatic PHEV-2 cells. Battery manufacturing includes prototype and sample production, from lab scale to near industrial production on the Research Production Line (FPL).
The manufacture of a battery is a multi-step process that requires a high level of expertise and precision. Battery manufacturing is an interdisciplinary field where materials science, electrochemistry, and engineering come together to produce efficient and powerful batteries. But what exactly happens during the production of a battery?
The initial stage of producing a battery is selecting the appropriate materials. Active materials hold a central role in every battery as they facilitate the chemical reactions that store and discharge energy. Yet, merely having active materials does not ensure that the battery will be of good quality. The battery's output and lifespan are considerably influenced by the interaction between the active materials and other components, particularly the electrolyte.
Particle design (also known as particle morphology) and additive selection are crucial factors in producing electrodes. The morphology of the particles determines how effectively chemical reactions can take place within the battery, while additives influence the battery's performance and lifespan. Creating electrodes, therefore, demands a high level of expertise and meticulous control of all variables.
This is then followed by cell design and the actual manufacturing process. Factors such as the quality and speed of the manufacturing process, as well as costs, are crucial. The design of the cell dictates how its components - including electrodes and electrolytes - are assembled to create a working unit. The manufacturing process quality significantly influences the end product's quality, while its speed determines the production rate, which, in turn, affects costs.
Finally, any new material or component utilised in battery manufacturing must undergo qualification and verification in sample runs prior to commercial production. This guarantees that the new material or component will function safely and proficiently, meeting the industry's rigorous standards.
Attaining a high-performance, long-lasting, cost-effective battery is dependent on meticulous planning and precise execution of every step in the manufacturing process. This necessitates a thorough comprehension of all process steps in actual production conditions.
The battery industry has made considerable strides in recent years, mainly due to the evolution of pioneering materials. Advanced materials improve battery efficiency, safety and longevity, reducing costs and conserving resources.
Scientists at the ZSW in Ulm are working on the formulation of innovative material compositions on a laboratory scale and on the development of suitable processing methods to transfer these materials to the scale of industrial battery production. By specifically optimizing the material composition and processing methods, we are able to maximize the outstanding properties of the materials through innovative formulations and thus increase efficiency.
The advantages of innovative material classes become apparent when they are processed into electrodes and complete cells. At the ZSW, the study of the properties and interactions with other cell components is therefore an important area of work, with which we can determine a deeper understanding of the function and its potential applications.
The selection and processing of innovative materials and the resulting electrode and cell properties are carefully analyzed and tested. At the ZSW in Ulm, there are extensive analytical facilities and highly experienced personnel available for this purpose.
The use of new materials also poses new challenges for the production process. For example, the replacement of the organic solvent NMP (N-methyl-2-pyrrolidone), which is harmful to health and the environment, by water requires the use of alternative, water-compatible binders and a new processing method for anode coating. The ZSW in Ulm is up to these challenges and is able to develop innovative solutions. This work is crucial for realizing the full potential of the new materials and developing the next generation of high-performance batteries.
Producing Li-ion cells requires unique electrodes for different applications. To meet these different requirements, ZSW uses specific methods and techniques for electrode development. All the equipment and expertise needed to produce customised electrodes is available at the ZSW in Ulm.
For instance, thinner coatings with a low active mass fraction are typically applied to electrodes for high-power cells because of the greater need for conductivity additives. Conversely, electrodes for high energy applications normally have thicker coatings with minimized amounts of additives in the formula.
The porosity of the electrode is also a vital factor. It determines the kinetics of the charging and discharging process, the energy density, as well as the adhesion and stability.
To identify the most effective electrode structure, ZSW employs different exploration methods, such as scanning electron microscopy (SEM), mercury porosimetry and electrochemical analysis. These techniques enable thorough examination of electrode attributes, leading to enhanced development of electrodes customized to specific applications.
ZSW's battery manufacturing facilities in Ulm are world-class in terms of diversity and technologies. The institute is able to develop and manufacture various cell formats, including single-layer pouch cells, 18650 and 21700 round cells, as well as pouch cells and prismatic PHEV-2 cells up to 80 Ah. As a result, customised solutions can be offered for a wide range of applications.
At ZSW, the work does not end with the assembly of the cells. A detailed analysis of the cell components is carried out, which is of great importance for the development or optimization of new cells. This enables us to continuously develop new, more efficient and more powerful battery cells. We take a holistic approach, from the production and characterization of active materials to the construction of complete battery systems and their testing, all the way to battery recycling.
Minister President Winfried Kretschmann visited the research production line (FPL), which has been in operation since 2013 and will be expanded in 2022. It is the only one of its kind in Europe for the near-industrial production of large lithium ion cells, such as those used in electric vehicles today. The ZSW works closely with industrial partners. The common goal is to continuously optimize and research production processes with new materials or improved plant components in order to generate precompetitive production know-how.
We are specialists in the development and manufacture of electrodes and cells in both laboratory and industrial scale. We have all the equipment necessary to perform all the steps in the cell manufacturing process.
In modern battery technology, there are a variety of cell formats that have their own advantages depending on the application. One such format that has recently become increasingly popular is the pouch cell.
A pouch cell is a flexible, flat lithium-ion battery cell housed in a flexible, sealed foil package. Unlike cylindrical or prismatic cells, they do not have a fixed metal casing, making them lighter and often more compact. The main advantage of pouch cells is their flexibility and ability to be manufactured in a variety of sizes and shapes, making them suitable for a wide range of applications, from electric vehicles to portable electronic devices.
Small pouch cells up to 5 Ah at ZSW
Before new battery materials can be used in large commercial cells, they must first be tested and evaluated in small sample cells. Small pouch cells (up to 5 Ah) are produced on a laboratory scale at the ZSW in Ulm. Using a professional stack winding machine, pouch cells with electrodes in the range of 40 mm x 65 mm can be reproducibly produced. In addition, ZSW offers the possibility to develop special formats according to specific customer requirements.
Large pouch cells up to 80 Ah
The research production line (FPL) for the manufacture of large lithium ion cells was established at the ZSW in 2014. It offers comprehensive equipment that is equivalent to the equipment used in commercial production processes. This enables the reproducible production of large lithium-ion cells and sample series at a high quality level in performance classes. New since 2022 is the flexible production of large pouch cells in different formats with a capacity of up to 80 Ah.
The systems cover the entire process from paste production and coating to assembly and cell formation. The conscious decision not to chain these lines together gives us great flexibility. New, advanced manufacturing processes can be easily integrated and tested in pilot production. This approach allows us to continuously develop and optimize our production methods.
In the dynamic world of battery technology, prismatic hard case cells have taken a special place due to their specific characteristics and advantages, especially in the field of electromobility and renewable energy storage.
Prismatic cells are a special type of lithium-ion cell. They are packed in a prismatic, i.e. rectangular or square, aluminum case (hardcase). Unlike cylindrical cells, which are round, prismatic cells allow more efficient use of space and are preferred for use in electric vehicles or stationary storage systems.
How is a prismatic cell made?
For production research, ZSW has been operating a unique research and development platform for the production of large prismatic lithium-ion cells since 2014, called the FPL (Research Production Line). Since 2022, the focus has been on the PHEV-2 format for large cells up to 80 Ah. For this purpose, the entire cell assembly line has been rebuilt and equipped with the newest equipment, including an electrode stacker and a laser cutter, enabling us to offer variable shape battery cell production.
Our assembly processes are automated and take place in a spacious 300-square-meter drying room designed specifically for testing innovative assembly technologies. A dew point of -60°C provides optimal production conditions.
In addition, an oxygen-reduced room is available for fully automated cell formation. It has 240 temperature-controlled cycler positions and a generous 2,016 storage positions on an area of 70 m².
With the establishment of the research production line for the near-industrial production of large lithium-ion cells (FPL), ZSW has taken on a central role in bridging the gap between laboratory development and series production. The platform enables the development, optimization and qualification of all processes up to the finished lithium-ion cell under near-series conditions.
The main goals of ZSW in this area are the demonstration of advanced active materials, the evaluation of new materials and components, the testing and optimization of new production processes, and the further development of crucial process parameters. With the support of the federal and state governments, the ZSW in Ulm has thus set global standards for commercial cell production in Germany.
Round cells are an essential component of modern battery technologies and are used in numerous applications. The ZSW in Ulm has developed special methods and techniques to produce these cells efficiently and with high quality.
A round cell, often referred to as a cylindrical cell, is a battery or accumulator cell with a cylindrical structure. Typical examples are the widely used 18650 cells. They consist of an anode and a cathode separated by a separator and enclosed in a cylindrical case. The name "18650" refers to the dimensions of the cell: 18 mm in diameter and 65 mm in length.
How are round cells made?
The production of round cells at the ZSW in Ulm follows a defined process to ensure that each cell meets the institute's high quality standards. Currently, the focus is on 21700 formats.
The cell assembly occurs in a special drying room with a dew point below -60°C. A vacuum chamber is then used to place the anode and cathode. The anode and cathode are then dried in a vacuum oven according to the ZSW process. A semi-automatic winding machine ensures that the anode and cathode are precisely positioned and aligned in parallel. A separator is inserted between them during the winding process. Especially with very thin separators, it is important to avoid wrinkles and still wind the separator tightly. After winding, more separators are added to form the outer layers of the wrap.
Other production steps include placing the wrap in a cup, folding the cups, welding on the separators, assembling the lid parts, and drying the open cells. Finally, the cell is filled with electrolyte and sealed. This structured process guarantees the reliable function and long service life of every round cell produced at the ZSW in Ulm.
At ZSW in Ulm, Germany, in addition to electrode and cell development, we offer our industrial customers a wide range of services related to the battery cell manufacturing process. We ensure that every step of battery production is carried out with the utmost care and precision to meet our customers' requirements. The staff is always available for questions and further information.
Recipe Development
In this process, the optimal material mix for the electrodes is developed. As this is a multifaceted process, the active material needs to be mixed with various additives to create a dispersion. By making use of rheometers, density meters, and zeta potential meters, ZSW is able to analyse the dispersions and determine the effects of the formulation on the electrochemistry in half or full cells.
Electrode coating
Various processes are utilized at ZSW to apply electrode paste (slurry) coating onto electrodes such as Commabar, wide slot die or roll-to-roll. These processes are capable of handling materials in small quantities during the development stage to create demonstration cells.
Our coating technologies include both an industrial scale coating system as well as a laboratory scale system featuring an 8 m dry channel. The industrial system provides a maximum width of 400mm for coating, permits double-sided coating, operates at a belt speed of 30m/min, and has a dry channel of 20m in length (refer to the figure).
Cutting/Punching
Once calendered, the highly dense electrode strips are cut by state-of-the-art laser cutters to size for larger cells, for example for the pouch and PHEV2 cells with capacities up to 80 Ah, or die-cut for use in smaller cells. If needed, electrodes can be produced with custom dimensions as per client requirements. An advanced laser cutting system is available for the production of battery cells with variable shapes.
Cell Manufacturing
We manufacture high-quality prototypes and sample series utilising revolutionary material classes and innovative, sustainable production methods. These comprise of 18650 and 21700 cylindrical cells, as well as pouch cells and hard case PHEV-2 cells up to 80Ah. Our state-of-the-art facilities encompass a laboratory pilot line and all required equipment to produce large lithium-ion cells under near-production conditions.
Quality Assurance with 3D-CT
At ZSW, 3D computed tomography (CT) technology enables non-destructive visualisation of the internal cell structure. This advanced technique facilitates a comprehensive study of the architecture of diverse cell types, including lithium-ion cells, in various formats. The precise microscopic analysis helps identify and visualise anomalies or defects accurately.
