Decomposition failure of Li1.5Al0.5Ge1.5(PO4)3 solid electrolytes induced by electric field: A multi-scenario study using Scanning Probe Microscopy-based techniques

The failure phenomena of the full cell battery based on Li1.5Al0.5Ge1.5(PO4)(3) ceramic electrolytes generally manifests as the macroscopic fading of the capacity, the governing mechanisms in the particular term of electrolytes remain elusive. In this study, Li1.5Al0.5Ge1.5(PO4)(3) electrolytes after cycling are characterized by multiscale techniques, including Scanning Probe Microscopy, to systematically investigate the chemical and structural evolution processes. Secondary phases are proven to exist in the cycled Li1.5Al0.5Ge1.5(PO4)(3). It is demonstrated that the Li1.5Al0.5Ge1.5(PO4)(3) electrolytes suffer from both electrochemical and mechanical deterioration during the cycling processes. The changes in both chemical compositional and inhomogeneous mechanical stress result in the failure of the electrolyte and pose high resistance to lithium-ion transport. Furthermore, the ionic transport process is successfully manipulated by a local electric field with amplitude of 2 V and 4 V from the tiny tip in Scanning Probe Microscopy. Based on the observed electrochemical strain response and contact stiffness variation induced by dynamic Li-ion fluctuation under an applied AC electrical field, the degradation process of the Li1.5Al0.5Ge1.5(PO4)(3) electrolyte is studied. It is determined that the chemo-mechanical degradation originates from the non-uniform Li ion distribution at the boundaries and/or voids in the interior of the electrolyte.