An essential factor for the effective integration of lithium-ion batteries into a greener energy system is the establishment of a sustainable and eco-friendly manufacturing process for battery components. While the water-based PFAS-binder-free method is well-established for carbon-based anodes, a comparable approach encounters numerous hurdles when applied to cathode materials, particularly those with high nickel content. The primary obstacle is the adverse side reaction occurring between nickel-rich cathode active materials (CAM) and water, yielding hydroxide and carbonate byproducts on the CAM surface. The formation of these byproducts elevates the pH of the aqueous slurry beyond pH = 12 which causes corrosion of the aluminum current-collector foil. These side reactions are additionally favored by lithium species on the CAM surface remaining from synthesis. Moreover, the sub-surface layer of secondary NMC particles undergoes delithiation (Li-leaching), resulting in loss of active lithium and formation of an inactive rock-salt-like phase on the particle surface diminishing the long-term cycling performance. We investigated these side reactions and ageing mechanisms of LiNi0.83Co0.12Mn0.05O2 in contact with water comprehensively.1
Previously we demonstrated the upscaling of an aqueous fluorine-free electrode formulation with Ni-rich LiNi0.83Co0.12Mn0.05O2 from laboratory scale to a roll-to-roll production of double-side Ni-rich positive electrodes with excellent cyclability in pouch- and 21700-type cells.2
The state-of-the-art industrial mixing processes utilizing planetary mixers require several hours for the slurry preparation. Knowing that time is a critical factor in suppressing hydroxide leaching of the CAM, one approach is to use advanced mixing techniques with the goal to reduce the mixing time. In this work, we investigate two different mixing strategies that are not yet well established in the electrode preparation process, but which offer short mixing times.
The first mixing strategy is the extrusion technique. Extrusion stands as a widely recognized method for continuous solvent-free processing. Within the field of lithium-ion batteries, there are many reports investigating dry-extrusion with PTFE as flux, but not many on water-based slurries. In addition to the short mixing time, the extrusion process enables the implementation of back-to-back a continuous electrode coating process immediately following the mixing phase. In this study, we present the first results from aqueous, PFAS-free extrusion of cathode pastes on a kilogram scale and electrochemical characterization in bi-layer pouch cells.
The second mixing strategy explored is the use of resonant acoustic mixing (RAM) technique. This method generates a high level of energy by seeking and operating at the resonant condition of the mechanical system including the materials being mixed. According to the manufacturer Resodyn, the RAM system is asserted to simplify upscaling, as the sound mixing method remains unaffected by vessel size and mass to be mixed. This enables implementation for a roll-to-roll production of electrodes. Energy transfer in RAM systems is more efficient due to the absence of mechanical mixing tools which reduces processing time and costs.4 While it has demonstrated significant potential in the concrete, pharmaceutical, and food sectors, its application in battery production remains relatively new. We present initial findings conducted on a small laboratory scale and electrochemical tests performed in coin half cells.
With the introduced mixing strategies it becomes feasible to reduce the mixing duration from several hours to approximately 5 minutes using the extrusion approach and about 15 minutes with RAM mixing.
References

[1] S. Radloff, Mitigating water-induced surface degradation in water-based Ni-rich Li-ion battery electrodes. Journal of Power Sources 580, 233314 (2023).
[2] S. Radloff, Flourine-free water-based Ni-rich positive electrodes and their performance in pouch- and 21700-typ cells. Journal of Power Sources 553, 232253 (2023).
[3] J. Seeba, Extrusion-based fabrication of electrodes for high-energy Li-ion batteries. Chemical Engineering Journal 402, 125551 (2020).
[4] M. R. Andrews, Resonant Acoustic Mixing: Processing and Safety. Propellants, Explosives, Pyrotechnics 45, 1 (2020).