(Front row, left) Senior researcher Jihee Yoon from KIMS and (Front row, right) Senior Researcher Insung Hwang from KERI successfully manufactured dry electrodes for high-capacity secondary batteries using the spray drying technique. Credit: Korea Electrotechnology Research Institute
Imagine the process that turns liquid coffee into instant granules being used to power the future of energy storage. Researchers at the Korea Electrotechnology Research Institute (KERI) and the Korea Institute of Materials Science (KIMS) have done just that, adapting spray drying, a technique familiar from the food industry, to create high-capacity battery electrodes. This research tackles key challenges in battery manufacturing.
The research was published in Chemical Engineering Journal.
Environmental advantages
First up, there’s the environmentally friendly angle and the potential for higher energy density. Traditional “wet” slurry-casting methods involve mixing battery materials (active material, conductive additive, binder) into a slurry with a solvent. This requires significant energy for drying (around 27% of the total manufacturing energy) and often uses toxic solvents like N-methyl-2-pyrrolidinone (NMP), which necessitates costly recovery systems (adding about 4.6% to manufacturing costs). Furthermore, this wet process suffers from “binder migration” during drying, making it difficult to produce the thick electrodes needed for higher energy density.
While solvent-free “dry” processing eliminates these solvent and drying headaches and allows for thicker electrodes, achieving a perfectly uniform blend of components is tough. Conductive additives like carbon nanotubes tend to clump together (agglomerate) due to strong intermolecular forces (π-π interactions), hindering performance. The KERI-KIMS team adapted spray drying to first create a highly uniform composite powder – named SW-SPD in their study – containing just the active material (LiNi0.8Co0.1Mn0.1O2, or NCM811) and the conductive additive (single-walled carbon nanotubes, or SWCNTs). This near-perfect premix, created using NMP only temporarily as a dispersing liquid before spray drying, is the key to unlocking higher performance in the final dry electrode.
Spray drying meets battery electrodes
Insung Hwang, Ph.D. from KERI is manufacturing dry electrodes for secondary batteries using a process called “calendering,” which involves turning composite powders into film form. Credit: Korea Electrotechnology Research Institute
Spray drying, commonly used to produce instant coffee, involves spraying a liquid mixture into a high-temperature chamber where the solvent evaporates instantly, leaving a dry, uniform powder. KERI and KIMS applied this method to battery electrode production through several key steps:
- Material premixing: Combining the NCM811 active material and SWCNT conductive additive into a liquid slurry.
- Spray drying: Atomizing the slurry into a heated chamber (around 210°C) to rapidly evaporate the liquid and form a highly uniform composite powder (termed SW-SPD in their research).
- Dry electrode formation: Mixing this SW-SPD powder with a PTFE binder, then performing ‘fibrillation’ where the binder is stretched into thread-like structures using specialized equipment to effectively weave the components together.
- Calendering: Pressing the resulting mixture into a thin, dense electrode film ready for battery assembly, as shown by Hwang in the image above.
This dry process entirely circumvents the need for NMP, significantly reducing the environmental footprint and energy consumption associated with electrode manufacturing.
Impressive metrics
The ‘spray drying equipment’ significantly improves the mixing of internal materials for dry electrodes in secondary batteries. Credit: Korea Electrotechnology Research Institute
The potential payoff for this solvent-free process is substantial. Thanks to the highly uniform composite powder created via spray drying, the researchers achieved a world-leading active material content of 98% in the final electrode. This curbs the need for non-storage components, specifically the conductive additives — dropping from the typical 2-5% range reported in other dry electrode literature down to 0.12% using the highly efficient SWCNTs.
More active material directly translates to higher energy storage potential within the same space. The resulting dry electrodes demonstrated an impressive areal capacity of approximately 7 mAh/cm², effectively doubling the performance of conventional electrodes typically rated between 2-4 mAh/cm². The research also showed good cycle stability, retaining 89.4% of its capacity after 100 cycles even at this high capacity loading, and 52.2% after 500 cycles.
Senior Researcher Insung Hwang from KERI highlighted the broader potential, stating the technology “can be applied to next-generation battery fields such as solid-state batteries and lithium-sulfur batteries,” significantly impacting areas from electric vehicles to grid-scale renewable energy storage. Looking ahead, Senior Researcher Jihee Yoon from KIMS added in a press release, “Through follow-up research, we plan to reduce process costs, improve mass production capabilities, and increase technology maturity, with the goal of eventually transferring the technology to companies.” This successful project, funded by NST and MOTIE, underscores the power of collaboration between government-funded research institutions in driving critical energy innovations.
