Microstrain and electrochemical performance of garnet solid electrolyte integrated in a hybrid battery cell

Abstract

Garnet type solid electrolytes are promising candidates for replacing the flammable liquid electrolytes conventionally used in Li-ion batteries. Al-doped Li₇La₃Zr₂O₁₂ (LLZO) is synthesized using nebulized spray pyrolysis and field assisted sintering technology (FAST), a novel synthesis route ensuring the preparation of samples with a homogeneous elemental distribution and dense ceramic electrolytes. Ceramic preparation utilizing field assisted sintering, in particular the applied pressure, has significant influence on the material structure, i.e. microstrain, and thereby its electrochemical performance. The phenomenon of microstrain enhancement of electrochemical performance might open a new route towards improved garnet solid electrolytes. A detailed mechanism is proposed for the lattice distortion and resulting microstrain during sintering. The charge transfer resistance of Li-ions at the interface between LLZO and Li is characterized using AC impedance spectroscopy and is amongst the best reported values to date. Additionally, the solid electrolyte is integrated in a full hybrid cell, a practical approach combining all the advantages of the solid electrolyte, while maintaining good contact with the cathode material.