Flawless Surface Qualities for a Perfect End Product
With many countries increasingly investing in electromobility, batteries are quickly becoming a central component of future mobility resulting in a boom in the production of lithium-ion and other batteries.
Today batteries usually consist of two metal foils which are connected to each other by an electrolyte. The electrolyte is applied to the foil by calendering as a slurry or directly as a powder in a dry coating process. Efficient machines and flawless rolls are crucial for a faultless production process. In the production of coated carrier foils in particular, the surfaces must be highly accurate, free of defects, showing a homogenous roughness.
Flawless surfaces are crucial when rolling battery foil − because even the smallest scratches or damage to the carrier foil can lead to serious defects in the finished cell, which ultimately result in expensive rejects. Herkules machines score points here primarily with their measuring and inspection technology for immediate detection of defects on the roll surface as well as inside the roll, but also thanks to their stable and robust design. Ralf Klews, Senior Sales Manager at Herkules, who has been working in the industry for many years, explains how important a good machine is for a flawless end product.
What do our customers expect from the end product?
Klews: In the field of battery foil production, the roll surfaces have to meet a variety of requirements, depending on various factors, e.g. the type of battery foil, the coating process, and the desired properties of the foil. In order to guarantee a bond between the carrier foil and the electrode material without delamination, a very homogenous surface is required across the entire width of the foil. This applies to the topography, i.e. the roughness, the structure of the surface and the elasticity, as well as the temperature stability. In addition, the roll surface must also withstand different chemical influences, such as a certain corrosion resistance with respect to the coating processes that are used.
A flawless surface means a better product: What measuring and inspection technologies can be used to ensure the homogeneity of the surface?
Klews: Herkules‘ sensitive measuring and control technology keeps the current, i.e. the pressure of the grinding wheel against the roll, constant within an extremely small tolerance of +/-0.3% during the finishing process − this results in an extremely homogenous surface. The Roughness Scattered Light Detection System (RSLD) uses scattered light to check the roughness of the entire roll barrel. Our Roll Surface Inspection System (RSIS), which uses a reflected laser beam to reliably detect possible surface defects and determines the surface quality of the roll using a threshold analysis, is also essential for perfect homogeneity. Defects are thus efficiently detected in advance and unnecessary roll changes are reduced to a minimum thus increasing the productivity of the rolling mill.
What are the challenges involved in coating battery foils?
Klews: The pre-coated foil should be as thin as possible in order to achieve higher capacities in the battery. At the same time, it must be ensured that the foils are sufficiently insulated from each other − otherwise voltage peaks will occur, which ultimately lead to the risk of fire. Once again, this underlines the importance of a homogenous surface roughness.
How do our machines achieve these required quality standards?
Klews: Thanks to our measuring and control technology, our machines are specifically designed to meet the high demands of battery foil production. For example, our Indian customer Hindalco Industries Limited, the metal flagship of the Aditya Birla Group, decided to purchase a WS 450 L × 4500 CNC Monolith™ for its production site in Mumbai because this machine is able to produce aluminum flat rolled products, foils, and aluminum packaging flawlessly.Our machine enables our customer Hindalco to define and achieve the next level of ultra-fine and absolutely flawless battery foil production. Herkules control and measuring technology is the first choice when producing battery foil. With hundreds of machines in aluminum foil and more than 30 machines in battery foil, Herkules is a top-notch choice for this demanding application. The result: Maximum efficiency and highly precise ground rolls with extremely user-friendly and intuitive operation via the touch panel.
Personal opinion: How will the industry develop and what challenges will arise in the future?
Klews: In my opinion, the course has been set for a battery-electric future. One example: The first battery-electric container ship has just been launched in China − 42 standard containers are fitted with batteries − these are exchanged for freshly charged (battery) containers in the port. If this catches on, immense capacities will have to be created over the next few decades. At the other end of the value chain, namely the recycling of batteries, things are also happening. Primobius, a company belonging to SMS group, advertises that it extracts 96% of the valuable raw materials for reuse. In cooperation with Mercedes-Benz, a pilot plant is currently being built to set new global standards in this area. So it remains exciting and I am grateful that Herkules − and I personally − can make our contribution to this transformation.