Development of an energy-efficient and environmentally friendly manufacturing process for electrode foils in lithium-ion batteries

Motivation

Conventional solvent-based electrode production delivers very good results, but is characterized by high resource and energy consumption. The scientists at Fraunhofer ISIT are working on how production can be carried out more cost-effectively and in a more environmentally friendly manner, focusing on solvent-free electrode manufacturing. This is because cost-effective and at the same time environmentally friendly production methods are a must for future battery cell production in order to serve the numerous fields of application.

Established production process: good, but high energy and resource consumption.

As a rule, electrode foils are produced in larger quantities in a roll-to-roll process. In coating plants, the substrate material, which is on large rolls, is unwound over rollers and continuously coated with the electrode material. In this process, a suspension of solvent, active material and a binder, which ensures the adhesion of the material, is applied to a metal foil. The coated electrode foil then passes through a drying oven before being rewound. These lines are very large; they can be up to a hundred meters long, depending on the duration of the drying process.

This production process has several disadvantages: the preparation of the suspension takes a very long time, the solvent used for cathode production is mostly harmful to the environment, and because of the long drying time in the oven, the process itself is very energy-intensive.

Dry coating process reduces resource and cost requirements

For this reason, the ISIT scientists relied on a solvent-free dry coating process. They produced a powder mixture of active material, conductive additives and a suitable binder. In order to produce as uniform an application as possible and precisely defined layer thicknesses, this powder mixture is applied to the substrate material using a special spreading process. The amount of powder applied can be precisely adjusted by the spreading parameters and by the speed at which the carrier film passes through the machine. The material is then fixed to the carrier in a short temperature process.

The new solvent-free dry coating process patented by ISIT is promising. With comparable electrochemical properties to electrodes from established production, this new process will not only enable significantly more compact production lines in the future, but also primary energy savings of up to 50 %, since the long and energy-intensive drying sections during production are eliminated. Both the time savings in producing the powder mixture and the significantly reduced energy requirements for coating, due to the elimination of drying, offer optimum conditions for reducing resource consumption and costs.
Dry coating technology has the potential to significantly reduce the costs and emissions of electrode production compared to the processes commonly used today. The process developed at ISIT thus makes a direct contribution to the development of economical and environmentally friendly storage technologies for mobile and stationary applications.