Enabling Porous Ceramic (LLZO) Electrodes for Solid State Batteries through Tapecasting

APPLICATIONS OF TECHNOLOGY:

Solid state battery electrodes
For use in vehicles or consumer electronics
Electrochemical cells with ceramic electrodes

BENEFITS:

The methods are more scalable and lower in cost compared to other approaches
Facilitates further impregnation with active battery materials
Enables the preparation of an integrated electrolyte without merging a separate dense layer

BACKGROUND:

Lithium lanthanum zirconium oxide (Li7La3Zr2O7, or LLZO) is a promising material for use in solid-state electrolytes. This ceramic material has good thermal and mechanical stability as well as high conductivity. However, it is typically difficult to fabricate electrolytes with this material due to its brittleness and sintering challenges.

TECHNOLOGY OVERVIEW:

Researchers at Berkeley Lab have developed the following technologies that facilitate the fabrication of porous ceramic LLZO electrode and dense electrolyte layers, leveraging tapecasting and sintering methods.

Tapecasting is a low-cost, scalable process for preparing electrode layers, but tapecasting inherently produces a structure that is parallel to the layer surface. Additionally, in the case of lithium solid state batteries, the sintering of LLZO to full density is difficult. It is complicated by several factors: the volatility of lithium at LLZO’s sintering temperature; the sensitivity of LLZO’s ionic conductivity to lithium deficiency and lithium surplus; inhomogeneous abnormal grain growth; and reaction of LLZO with a variety of substrates. LLZO parts with too much lithium will exhibit poor ionic conductivity. Furthermore, the lithium source can act as a pore former and reduce the part’s final density.

The following inventions address the above limitations:

Tapecasting of LLZO (2020-061): Researchers have created a composition for LLZO-compatible binder systems. They identified aqueous and solvent-based tapecasting systems (binder, solvent, dispersant, solids loading, etc) that overcome the limitations of conventional tapecasting systems such as reaction with the LLZO particles.

Fabrication methods for LLZO electrodes (2020-117): Researchers created two new processes of fabricating thick porous LLZO based solid state electrodes by using phase inversion (PI) and high shear compaction (HSC) methods. These two approaches create a porous scaffold of the densified solid electrolyte that could improve the energy density of solid state electrodes. For instance, the porosity of the LLZO tapes after sintering was as high as 75.4%. Ultimately, the unique architecture enabled a thin densified electrolyte to be supported on a highly porous scaffold. The technology demonstrates the possibility of cathode filling for full cell assembly.

DEVELOPMENT STAGE: Proven principle

FOR MORE INFORMATION:

https://als.lbl.gov/porous-electrolyte-frameworks-for-all-solid-state-batteries/

PRINCIPAL INVESTIGATORS: