April 7 - 11, 2025
Seattle, Washington
Symposium Supporters
2025 MRS Spring Meeting & Exhibit
EN01.15.09

Printable and Coatable Polymer Composite Separators for Lithium-Ion Battery Manufacturing

When and Where

Apr 11, 2025
11:45am - 12:00pm
Summit, Level 3, Room 327

Presenter(s)

Co-Author(s)

Michelle Katz1,Vinh Nguyen1,Corie Cobb1

University of Washington1

Abstract

Michelle Katz1,Vinh Nguyen1,Corie Cobb1

University of Washington1
Separators serve a critical function in lithium-ion batteries (LIBs) by electrically insulating the anode and cathode while facilitating ion transport through electrolyte-filled pores and adding mechanical integrity to the cell stack. Commercial separators are typically made by extruding a polyolefin melt or solution into a film and then stretching the film to produce a porous microstructure. However, this manufacturing approach prevents the separator from being directly integrated into the large-scale coating processes used for the electrodes, which imposes more discrete processing steps in LIB manufacturing and cell assembly. As a step towards creating a more streamlined manufacturing process, we developed a high viscosity, shear-thinning phase inversion polymer composite separator formula that can be coated directly onto a LIB electrode, resulting in what we call a “direct-on-electrode” separator. We investigated four different separator formulas, using either diethylene glycol (DEG) or triethyl phosphate (TEP) as a non-solvent, and either silica (SiO2) or alumina (Al2O3) as an inorganic additive in a polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) matrix. Through a designed experiment and down-selection process, we found that the TEP-SiO2 formulation yielded the most promising electrochemical, mechanical, and thermal performance. The TEP-SiO2 separator formula had a viscosity of 1540 Pa-s at a 0.1 s-1 shear rate, which dropped to 80 Pa-s at a 10 s-1 shear rate. The strong shape-retention properties prevented the liquid-state separator slurry from infiltrating the electrode pores during direct-on-electrode fabrication, enabling process compatibility with casting, 3D printing, and slot-die coating. When tested in LiFePO4|Li4Ti5O12 (LFP|LTO) coin cells, the direct-on-electrode TEP-SiO2 separator increased the specific discharge capacity of the cell by 58% at a 2C discharge rate relative to a commercial Celgard 2325 separator. Additionally, the TEP-SiO2 separator maintained dimensional stability when heated to 200°C for one hour. As a path towards future manufacturing scale-up and re-thinking LIB manufacturing, we highlight a few manufacturing demonstrations with our polymer composite separator slurries.

Katz, M. E. R.; Cobb, C. L. High-Viscosity Phase Inversion Separators for Freestanding and Direct-on-Electrode Manufacturing in Lithium-Ion Batteries. ACS Appl. Mater. Interfaces 2024, 16 (34), 44863–44878. https://doi.org/10.1021/acsami.4c09342.

Acknowledgement
This work was funded by a Defense Advanced Research Projects Agency (DARPA) Young Faculty Award and Director’s Fellowship under grant number D19AP00038. The views, opinions, and findings expressed in this work are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government, and no official endorsement should be inferred. This is approved for public release and distribution is unlimited.

Keywords

additive manufacturing | composite

Symposium Organizers

Junjie Niu, University of Wisconsin--Milwaukee
Ethan Self, Oak Ridge National Laboratory
Shuya Wei, University of New Mexico
Ling Fei, The University of Louisiana at Lafayette

Symposium Support

Bronze
BioLogic
Neware Technology LLC

Session Chairs

Junjie Niu
Shuya Wei

In this Session