In operando characterization of the ionic conductivity dependence on liquid transient phase and microstructure of cold-sintered Bi2O3-doped Li1.3Al0.3Ti1.7(PO4)3 solid-state electrolyte

Abstract

A disruptive sintering technique, Cold Sintering Process (CSP), has been used to produce cold-sintered samples of Bi2O3-doped Li1.3Al0.3Ti1.7(PO4)3 (LATP) as solid-state electrolyte (SSE). An in operando impedance study has been performed to shed light on this sintering process. In this work, Bi2O3 and 3 m acetic acid solution sintering aids were synergistically added to LATP powders to sinter at low temperature. Effects of Transient Liquid Phase (TLP) content on the sintering behavior, phase composition, microstructure, and electrochemical properties were all investigated for a LATP doped with 2 wt% Bi2O3 (optimal content) solid-state electrolyte (SSE). The data revealed that the final electrical properties, which are the key parameter decisive for their application, are defined by the following sintering parameters: Transient Liquid Phase (TLP) content, temperature, pressure, and dwell time. Using acetic acid 3 m as TLP, LATP-based samples can be cold-sintered at optimized sintering conditions of 150 °C and 700 MPa of uniaxial pressure for 90 min. The resultant SSE shows a high ionic conductivity (4.5·10−5 S cm−1) at room temperature (RT) and relative density (∼95%), which demonstrates the effectiveness of the low-temperature sintering process by optimizing the ionic conductivity of LATP-based SSE, also reducing preparation costs and CO2 emissions.