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

TLDR

The study examined the reactivity of high‑voltage spinel cathodes (Li₂NiMn₃O₈, Li₂FeMn₃O₈, LiCoMnO₄) cosintered with Li₁.₅Al₀.₅Ti₁.₅(PO₄)₃ and Li₆.₆La₃Zr₁.₆Ta₀.₄O₁₂ electrolytes by thermal analysis (XRD, DTA, TG‑MS) and matched the observed decomposition reactions with first‑principles predictions, achieving high‑fidelity identification. Decomposition of the cathode–electrolyte mixtures starts at 600 °C, producing stable insulating phases such as La₂Zr₂O₇, La₂O₃, La₃TaO₇, TiO₂, LaMnO₃, and Li₃PO₄ that raise interfacial impedance, indicating that high‑temperature cosintering of high‑voltage spinel cathodes with Li₁.₅Al₀.₅Ti₁.₅(PO₄)₃ or Li₆.₆La₃Zr₁.₆Ta₀.₄O₁₂ electrolytes will hinder solid‑state battery performance.

Abstract

The reactivity of mixtures of high voltage spinel cathode materials Li2NiMn3O8, Li2FeMn3O8, and LiCoMnO4 cosintered with Li1.5Al0.5Ti1.5(PO4)3 and Li6.6La3Zr1.6Ta0.4O12 electrolytes is studied by thermal analysis using X-ray-diffraction and differential thermoanalysis and thermogravimetry coupled with mass spectrometry. The results are compared with predicted decomposition reactions from first-principles calculations. Decomposition of the mixtures begins at 600 °C, significantly lower than the decomposition temperature of any component, especially the electrolytes. For the cathode + Li6.6La3Zr1.6Ta0.4O12 mixtures, lithium and oxygen from the electrolyte react with the cathodes to form highly stable Li2MnO3 and then decompose to form stable and often insulating phases such as La2Zr2O7, La2O3, La3TaO7, TiO2, and LaMnO3 which are likely to increase the interfacial impedance of a cathode composite. The decomposition reactions are identified with high fidelity by first-principles calculations. For the cathode + Li1.5Al0.5Ti1.5(PO4)3 mixtures, the Mn tends to oxidize to MnO2 or Mn2O3, supplying lithium to the electrolyte for the formation of Li3PO4 and metal phosphates such as AlPO4 and LiMPO4 (M = Mn, Ni). The results indicate that high temperature cosintering to form dense cathode composites between spinel cathodes and oxide electrolytes will produce high impedance interfacial products, complicating solid state battery manufacturing.