Innovative and efficient production lines for electrodes and further battery components – tailor-made solutions from a single source

Press, Engineering
©Matthews International GmbH
©Matthews International GmbH

Since Olbrich GmbH, the Saueressig Group, and the Polytype Converting brand joined forces as part of Matthews Engineering, it is not only the core business area of “classic” coating and converting that has experienced noticeable synergy effects, but also the Energy division, which serves the rapidly growing market for renewable energies and advanced storage solutions and is positioned with a broad-based but customer-centric portfolio.

“We are convinced that we need to be extremely innovative to strengthen the capabilities in the battery sector in order to reach the necessary climate targets – that’s why we are dedicated to empowering the pioneers of tomorrow through the development and delivery of cutting-edge machinery and equipment,” states Brandon Babe, Senior Vice President and Business Head, Matthews Engineering. Based on decades of experience as a leading manufacturer of machines and systems for the processing of web-shaped materials, the company has successfully transferred its core competencies into the area of Renewable Energies. “With the combined capacities and competencies of all three brands, the portfolio in the battery sector – as well as in the field of fuel cells – has undergone a decisive expansion”, Esa-Matti Aalto, Senior Vice President/General Manager Coating & Converting Industries, Matthews Engineering, sums up. “We are ideally positioned to serve the needs of the growing market comprehensively – including key issues such as scalability and efficiency in the production of battery components.”

Comprehensive portfolio for the production of battery components

A battery is a highly complex product whose production is based on a differentiated process chain. In most cases, there are several different processes and technologies for the production of the individual components – with a wide variety of challenges and advantages, that can have immense effects on the quality and performance of the end product “battery”. Briefly outlined, the structure of a battery cell looks like this: It consists of a positively and a negatively charged electrode (anode and cathode), which are electrically isolated from each other by a separator. After cell assembly, an electrolyte solution is injected into the battery cell which saturates it and enables the ion flow. Finally, a cell housing is needed that serves to protect against external influences – mechanical impacts as well as triggers of chemical reactions – and prevents electrolyte leakage.

For most of these components, Matthews Engineering develops and manufactures highly specialized machines and systems, covering the entire process from development, design and manufacturing to installation and commissioning of the production lines. Solutions for the battery industry include electrode production equipment in various processes, including primer coating for optimizing the contact between electrode and electrode arrester (aluminum or copper foil) and lines for separator foil coating. Production lines for battery wrapping applications complete the portfolio.

In detail: Electrode production based on wet coating and dry process

In the widely used conventional process, industrial battery electrode production relies on wet chemical coating. In this process, the so-called slurry – consisting of the active materials, additives, and a solvent – is applied to the respective substrate film (aluminum or copper). After passing through a drying channel, the electrode is compressed to its final density and thickness. Matthews Engineering offers proven calendering production lines for electrode manufacturing based on the wet coating process, both for continuously coated and intermittently coated electrodes. Thanks to a patented gap system with constant gap adjustment, the lines for intermittently coated electrodes enable a thickness accuracy of +/- 1um.

For some time now, the battery industry has been increasingly seeking dry manufacturing processes in electrode production, which do not require solvents and expand the range of active materials that can be considered. The innovative technology developed by Matthews Engineering for the production of electrodes using the dry process allows for powder-to-film and lamination onto a current collector foil with maximum accuracy in a limited number of production steps. This distinguishes it from conventional methods.

This is preceded by the primer coating process, for which Matthews Engineering supplies the equipment for highly efficient production. The substrate (aluminum or copper foil) is coated with a primer to increase the adhesion between the metal foil and the layer of active material – to be applied in the next process step – and to prevent its detachment. With its noticeable effect on the conductivity, stability / safety and energy density of the battery cell, this pre-treatment offers a whole range of advantages. Lines can be customized to a width of up to and beyond 1,500 mm, with possible coating weights of 0,5 – 3 g/m² (dry) and substrate thickness ranging from 6 – 15 μm. Depending on the specification, currently a production speed of up to 300 m/min is achieved – but higher production speeds are already under development. In addition, the coating pattern can be flexibly adapted. The uncoated areas of the stripe coating are crucial in terms of functionality and for the further production steps in cell assembly. Furthermore, this type of coating assures minimum material waste in the cutting process.

To come back to the calender systems in electrode manufacturing: Both wet coating and dry process share a common challenge, as very high requirements are placed on the calender rollers used in these processes – in terms of concentricity, cylindrical shape and surface quality – in order to achieve the required performance. Here, too, customers in the battery industry benefit from the company’s broad positioning. For decades, calender rollers and smoothing rollers produced by Saueressig have been used as powerful and precise tools in a wide range of converting applications. Calender rollers for electrode production with high hardness values at extreme hardening depths can even cope with the demanding temperatures and loads in the roller gap, and therefore are able to fulfill the high requirements of the battery industry. At the same time, the rollers are inevitably subject to wear. This is where the comprehensive roller service comes in – with refurbishment services at the Precision Center in Vreden (DE), which is currently being expanded, and at the North American site in San Antonio, Texas (USA), each of which is equipped with state-of-the-art machinery for precision grinding and the required final finishing of the rollers.

In detail: Coating lines for battery separator foil

The separator foil, that is placed between anode and cathode within the battery cell, ideally needs to be thin and perforated in such a way as to allow the permeability for lithium-ions. In the manufacturing of this battery component, this results in certain challenges – to be faced by Polytype Converting with a process and line layout that allows for very low web tensions and copes with the substrate’s high tendency to wrinkling. Solutions lie in the use of engraving rollers with a customized diameter in a system with pressurized chamber doctor blade, in optimized web paths and distances – in particular regarding the flatness of the separator foil in the area of the coating machine – and the optimisation of the drying process, based on a system with driven guide rollers. This ensures an adapted high drying efficiency in terms of heat transfer and low web tensions.

The focus is on two types of the separator foil: Firstly, PE films (made of biaxially oriented polyethylene) with a thickness of 6 – 20 µm and a web width of 1,400 mm are coated continuously on both sides in a single pass. Beyond usual production speeds of 200 m/min, coating speeds of 400 m/min have already been run with stability and consistently high quality. The water-based ceramic coating increases the thermal resistance and ultimately serves to protect the PE film. In addition, and as the second product type, a special set-up is realizable.  Here, which the already treated substrate (following the process described above) additionally receives a dotted polymer pattern and/or a full adhesive coating.

Constant development and maximum efficiency also concern the application of battery separator foil. At the Competence Center in Bocholt, Germany, which offers comprehensive testing facilities for the converting industry along with the company’s site in Fribourg, Swiss, individual customer trials can be run.

In detail: Battery wrapping

While the thermal method (based on extrusion) can also be used to manufacture the flexible cell housing for pouch cells, Polytype Converting relies on the so-called dry method. In a first step, a double-sided primer coating is applied simultaneously to the substrate (aluminum with a thickness of 20 – 50 µm). This coating solution is water-based and reaches a coating weight of 1 – 10 g/m² with a solid content of 1 to 10 percent. The production line is designed for maximum space and energy efficiency: After the double-sided coating, it requires only a single dryer. In a separate line, a direct solvent-based adhesive coating on aluminum and the dry lamination with a PP layer respectively Nylon and PET is performed. Space and investment costs play a decisive role – therefore the line usually includes only one coating station in which lamination is carried out in several steps.

This method offers decisive advantages compared to the thermal method with extruders: The process speed is higher; the product shows good waterproof characteristics and a high-quality appearance with significantly fewer damages like pinholes and fisheyes.

Innovative solution provider for the battery industry

Matthews Engineering is shaping the future of the energy industry based on its expertise in a wide range of web processing technologies, including calendering, embossing, smoothing, coating, laminating, drying, winding and perforating, and by successfully transferring these competencies to the rapidly evolving field of battery research and production. “With our strong portfolio, we cover a broad part of the battery component production value chain. Our customers in the battery industry benefit from decades of experience and tailor-made, scalable solutions,” summarizes Ning Chen, Senior Vice President Business Development, Energy, Matthews Engineering. “At the same time, we will continue to position ourselves as an innovation leader. The effective transformation towards a sustainable energy supply requires holistic solutions and constant innovations.”