Water-based Processing of Garnet-Containing Ceramic Composite Cathode for Solid-State Lithium Batteries
YE R. 1,2, IHRIG M. 1, FIGGEMEIER E. 2,3, FINSTERBUSCH M. 1,3
1 Institute of Energy and Climate Research – Materials Synthesis and Processing (IEK-1), Forschungszentrum Jülich GmbH, Jülich, Germany; 2 Institute for Power Electronics and Electrical Drives (ISEA), RWTH Aachen University, Aachen, Germany; 3 Helmholtz Institute Münster (HI MS, IEK-12), Forschungszentrum Jülich GmbH, Münster, Germany
Battery technology is considered to support our transition towards a “green” and environmentally friendly society. In order to achieve this goal, “better”, “green” and sustainable battery technology is required.
Higher energy and power densities, increased safety levels, and wider operational temperatures are achieved in solid-state Li batteries (SSLBs), which is a representative of next-generation battery technology. Among the most promising solid electrolytes is the garnet-type Li7La3Zr2O12 (LLZ). LLZ is suitable for the commercially relevant tape casting process. However, this process relies commonly on hazardous organic chemicals. Thus one prerequisite to consider LLZ-based Li batteries as “green” and sustainable batteries is to omit the hazardous chemicals in the tape casting process. Ideally the tape casting would be water-based.
However a spontaneous Li+/H+ exchange (LHX) reaction occurs when LLZ is exposed to water. The protonated LLZ shows increased sintering activity but impaired Li-ion conductivity. Omitting or reversing the LHX would allow the preparation of LLZ-based Li batteries by water-based and “green” tape casting. Recently the reversibility of the LHX was revealed by exposing protonated LLZ to elevated temperature in the presence of excess Li sources, for instance LiOH and Li2CO3.
Water-based tape casting allows sustainable fabrication of LLZ separators. This work was now extended by us to allow the fabrication of LiCoO2 (LCO)-LLZ composite cathodes. After modifying and optimizing of the water-based tape casting and adjacent sintering process, dense, free-standing and phase-pure composite cathodes were obtained. SSLBs assembled with these composite cathodes provide a high areal capacity of more than 3 mAh cm-2. The high areal capacity was achieved as nearly the entire LCO within the cathode was utilized.
Our developed water-based tape casting might allow the use of more advanced cathode active materials and thus pave the way to “green” and sustainable LLZ-based Li batteries.
 Ye, R.; Ihrig, M.; Imanishi, N.; Finsterbusch, M.; Figgemeier, E., A Review on Li+/H+ Exchange in Garnet Solid Electrolytes: From Instability against Humidity to Sustainable Processing in Water. ChemSusChem 2021, 14 (20), 4397-4407.
 Ye, R.; Tsai, C.-L.; Ihrig, M.; Sevinc, S.; Rosen, M.; Dashjav, E.; Sohn, Y. J.; Figgemeier, E.; Finsterbusch, M., Water-based fabrication of garnet-based solid electrolyte separators for solid-state lithium batteries. Green Chemistry 2020, 22, 4952-4961.