About the Compatibility between High Voltage Spinel Cathode Materials and Solid Oxide Electrolytes as a Function of...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• High voltage spinel cathode materials (Li$_{2}$NiMn$_{3}$O$_{8}$, Li$_{2}$FeMn$_{3}$O$_{8}$, LiCoMnO$_{4}$) are crucial for advanced energy storage.
• Oxide electrolytes, such as Li$_{1.5}$Al$_{0.5}$Ti$_{1.5}$(PO$_{4}$)$_{3}$ and Li$_{6.6}$La$_{3}$Zr$_{1.6}$Ta$_{0.4}$O$_{12}$, are promising for solid-state batteries.
• Understanding interfacial reactions during co-sintering is vital for developing stable solid-state battery composites.

Purpose of the Study:

• To investigate the reactivity between high voltage spinel cathode materials and solid oxide electrolytes during co-sintering.
• To identify decomposition products and reaction mechanisms at elevated temperatures.
• To assess the impact of these reactions on interfacial properties relevant to solid-state battery performance.

Main Methods:

• Thermal analysis techniques including X-ray diffraction (XRD), differential thermal analysis (DTA), and thermogravimetry coupled with mass spectrometry (TG-MS).
• First-principles calculations to predict and validate decomposition reactions.
• Analysis of mixtures of spinel cathodes with Li$_{1.5}$Al$_{0.5}$Ti$_{1.5}$(PO$_{4}$)$_{3}$ and Li$_{6.6}$La$_{3}$Zr$_{1.6}$Ta$_{0.4}$O$_{12}$ electrolytes.

Main Results:

• Mixtures decompose at temperatures as low as 600 °C, lower than individual component decomposition temperatures.
• Reactions with Li$_{6.6}$La$_{3}$Zr$_{1.6}$Ta$_{0.4}$O$_{12}$ form stable, insulating phases (e.g., La$_{2}$Zr$_{2}$O$_{7}$, La$_{2}$O$_{3}$) increasing interfacial impedance.
• Reactions with Li$_{1.5}$Al$_{0.5}$Ti$_{1.5}$(PO$_{4}$)$_{3}$ lead to Mn oxidation and lithium transfer, forming phosphates (e.g., Li$_{3}$PO$_{4}$, AlPO$_{4}$).
• First-principles calculations accurately identified decomposition pathways and products.

Conclusions:

• High-temperature co-sintering of spinel cathodes with oxide electrolytes generates detrimental interfacial products.
• These interfacial products, often insulating and stable, significantly increase impedance.
• The findings highlight challenges in manufacturing dense, high-performance solid-state battery cathodes using current co-sintering methods.