Chemical compatibility at the interface of garnet-type Ga-LLZO solid electrolyte and high-energy Li-rich layered...

All-solid-state batteries (ASSBs) with a garnet-type solid electrolyte have been considered promising alternatives to traditional batteries with a liquid organic electrolyte, due to their enhanced safety and ability to accommodate high energy density electrodes. In this study, we conducted a comprehensive investigation of the high-temperature chemical compatibility between the garnet-like Li_6.4Ga_0.2La₃Zr₂O₁₂ (Ga-LLZO) electrolyte and high-energy-density Li-rich layered Li_1.2Ni_0.2Mn_0.6O₂ cathode (LNM). Our findings suggest that a high temperature reaction between the Li-rich cathode and Ga-LLZO occurs at 700-900^oC depending on the form of reactants. This reaction results in the formation of La(Ni, Mn)O₃ and Li₂ZrO₃ as the two main products, as confirmed by powder X-ray diffraction and transmission electron microscopy analysis. Li₂ZrO₃ was discovered for the first time as a reaction product, and its formation in the case of Li-rich layered cathode material was rationalized with DFT + U calculations. The results were also compared with those obtained for a typical layered high-energy-density cathode material LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811).