The global battery manufacturing capacity by 2030 is set to be around 4700 GWh. Currently, the most common way of manufacturing the battery cells is by using the wet slurry process which involves the use of NMP [N-Methyl-2-pyrrolidone] as a solvent is giving excellent results in the quality of the slurry and its homogeneity, which is very important for the coating process.
The main purpose of NMP is to activate the binders so the active material can adhere to the current collector.
In 2020, the EU implemented a restriction on the use of NMP under REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals) regulations. This restriction aims to protect workers’ health and the environment from the potential risks associated with NMP exposure.
Today electrode manufacturing is a more energy-intensive and high capex process, the wet slurry is made and then the paste is coated on the electrode foils using the slot die and doctor blades and later sent for a drying process to remove the solvent.
In the traditional electrode manufacturing process, the dryers are tens of meters long which takes a lot of space and energy as it includes heaters, heat exchangers, mechanical rollers, and even a system outside the cell factory for solvent recovery. It is estimated that 42 KWh of Energy is required to evaporate the NMP per kWh of the batteries produced, Imagine the amount of energy spent for evaporating the NMP for 4700 GWh of batteries that would be produced by 2030. To overcome this challenge researchers and industry experts are working on the elimination of the use of solvent which eliminated the drying and solvent recovery process.
Currently, Tesla and Volkswagen-Power Co are working seriously on the dry electrode manufacturing process.
How does the Dry Electrode Production work?
The active materials, conductive carbon black, binders (PVDF) are dry mixed and one of the ways is the Electrostatic spraying method.
Electrostatic Spraying method:
The dry mixed materials are charged positively they are sprayed on the foil (Cu/Al), and the foils are charged negatively, and this is results in electromagnetic attraction to occur. Now this sprayed electrode is calendared through heated rollers in which the PVDF is melted which helps in adhering the binder to the active materials to the current collectors.
With this type of process, it is difficult to achieve the same level of adhesion throughout the process which NMP is successful in doing it. Even the heated calendared rollers can degrade the active materials or even the binders, which can ultimately reduce overall cell performance.
The benefits if Dry electrode production is feasible for Mass Production:
- Equipment Foot Print cut down: Baglino and Musk at the Tesla battery day went on to describe a coating system that reduces the factory space required to make the electrodes to one-tenth of its former size, decreases the necessary energy that goes into battery production by the same amount, and cuts the battery’s cost by about 10%. But Tesla is working on this.
- Energy savings: Ten times in reduction of Energy costs due to complete elimination of Drying and Solvent recovery systems.
- Save 19% of manufacturing cost for coating/drying/solvent recovery