German researchers have found a way of mass manufacturing cathodes that replaces the toxic solvent NMP and the binder mixture PVDF with an aqueous formulation and a fluorine-free binder.
The scientists at the applied research Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) produced nickel-rich cathodes with high specific energy and longevity on a pilot scale.
They assembled the resulting electrodes into type 21700 round cells. They found they retained 80% of their initial capacity after 1,000 charge/discharge cycles, which they reckon makes them suitable for use in battery vehicles.
The team said there has been considerable progress on a laboratory scale in the water-based production of electrodes that contain nickel-rich active materials. But proof of concept for mass manufacturing was missing. ZSW now claims this process’s viability on a factory-like scale.
“Our work targets the improvement of electrodes production for lithium-ion batteries to make it ecofriendly without compromising battery performance,” said Prof. Dr. Markus Hölzle, head of the Electrochemical Energy Technologies Division in Ulm.
They also produced electrodes up to around 100 metres long for the first time to produce cylindrical battery cells in 21700 format. Car manufacturer Tesla uses this cell format in its Model 3.
The active cathode material has 83% nickel by weight and graphite on the anode.
Dr. Margret Wohlfarth-Mehrens, head of the Accumulators Materials Research department, which carried out this work, said: “We are significantly reducing the environmental footprint of lithium-ion batteries with our new production process.
“Water has been used as a solvent for anodes for many years, even on an industrial scale. Now we have succeeded in doing the same for the cathode materials. In addition to eliminating toxic solvents, water also enables the use of non-fluorinated binders, which greatly simplifies battery recycling.”
The work was part of the DigiBatt Pro 4.0 project funded by the German Federal Ministry of Education and Research.