The role of the LATP particle size as a cornerstone of the cold sintering process

Abstract

An innovative sintering technique, the Cold Sintering Process (CSP), has been employed to obtain dense Li1.3Al0.3Ti1.7(PO4)3 (LATP) Solid-State Electrolytes (SSE) by optimising the particle size (d50) of the starting powder. The CSP is carried out at 700 MPa, 150 ºC, and 90 min of sintering time, using acetic acid solution as Transient Liquid Phase (TLP). The CSP lowers the LATP sintering temperatures almost 1000 ºC. To study the electrical properties, an in operando Electrochemical Impedance Spectroscopy (EIS) technique has been used. The optimum d50 is 0.415 µm, yielding to competitive microstructure and electrical properties (ionic conductivity of 6.93·10−5 S cm−1 at 30 ºC, activation energy of 0.363 eV, and a relative density of 81.2 ± 0.8%). Relative density, ionic conductivity and TLP content must be balanced, because at small d50, although relative density is enhanced the ionic conductivity is reduced. A packing model has been used to understand this behaviour and the mass transfer mechanisms.