Affiliation:
1. Centre for Cooperative Research on Alternative Energies (CIC energiGUNE) Basque Research and Technology Alliance (BRTA) Albert Einstein 48 01510 Vitoria-Gasteiz Spain
2. University of Basque Country (UPV/EHU) Barrio Sarriena, s/n 48940 Leioa Spain
3. ALISTORE-European Research Institute 80039 Amiens France
Abstract
AbstractLi7La3Zr2O12 garnets are among the most promising materials for solid‐state electrolytes thanks to their high electrochemical stability and ionic conductivity. However, they are unstable in air and easily undergo a Li+/H+ exchange reaction, forming a lithiophobic and poorly Li‐conducting surface layer composed of LiOH and Li2CO3 upon further reaction with CO2. Despite a simple reaction mechanism, protonation of LLZO is a complex phenomenon. The thickness and composition of the secondary phases on the surface depend on many parameters both in the LLZO properties and in the storage atmosphere. Due to this complexity, proposing a universal procedure for removing the secondary phases is not simple. However, understanding the role of different parameters and rational selection of characterization techniques makes it possible to find the optimal conditions for removing the LiOH/Li2CO3 layer and further processing each material. This work compares some of the main approaches for cleaning the LLZO surface and describes their advantages and shortcomings. Additionally, the strengths and limitations of the most common characterization techniques for analyzing the (de)protonation of LLZO (XRD, XPS, Raman, NMR, TGA) are explained to help researchers design their experiments more accurately.