Interpretation of the resistance of Li7La3Zr2O12 – Li2O–B2O3–SiO2 composite electrolytes for all–solid–state batteries using the distribution of relaxation times technique

Abstract

Solid electrolytes based on Li7La3Zr2O12 are promising membranes for all–solid–state batteries. However, the main parameters of all transport stages in composite and doped Li7La3Zr2O12 could not be determined by conventional impedance fitting. A tremendous assistance in the analysis of impedance spectra over the past few years has become the method of distribution of relaxation times (DRT). In the present study, a composite electrolyte Li7La3Zr2O12 – Li2O–B2O3–SiO2 was investigated by impedance spectroscopy. A detailed analysis of the impedance spectra by DRT showed that the additional peak appears on the DRT function with the introduction of glass; this interfacial resistance is responsible for the transfer of lithium ions across the Li7La3Zr2O12/glass interface. The resistance, capacitance and relaxation frequency of all the transport stages in the composite electrolytes were determined based on the analysis of the DRT functions. It was found that the Li7La3Zr2O12/glass resistance decreases with increasing fraction of glassy additive. It was established that the DRT technique can be successfully used to deeper understanding of the transport stages of lithium ions in composite and doped solid electrolytes for all–solid–state batteries.