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Solid-state electrolytes (SSE) are one of the fundamental components of the upcoming generation of batteries since they increase the operational safety and efficiency. In this work, composite solid electrolytes (CSE) based on Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 and a (PEO 2 -LiTFSI) polymer matrix are obtained via the pioneering Cold Sintering Process (CSP), with a drastic reduction of the conventional sintering temperature. The CSP is performed at only 150 °C and 700 MPa, for 90 min of sintering time, by using a 3 m acetic acid solution as the transient liquid phase (TLP). Here, the effect of the LATP particle size (d 50) is studied to tailor the final microstructure, which enables the fine-tuning of the ultimate electrical properties of the electrolyte. An optimum d 50 of 0.415 μm produces CSEs with 91 % of relative density, an ionic conductivity of 0.169 mS/cm, activation energy of 0.293 eV and electrical stability under 0.1 mA/cm2, thus leading to competitive properties. [Display omitted] [ABSTRACT FROM AUTHOR]

An innovative sintering technique, the Cold Sintering Process (CSP), has been employed to obtain dense Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 (LATP) Solid-State Electrolytes (SSE) by optimising the particle size (d 50) 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 d 50 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 d 50 , 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. [Display omitted] • Cold Sintering Process method to sinter LATP Solid Electrolyte. • Combination of 3 cornerstones: particle size, CSP and in operando impedance. • Effect of particle size on microstructure and electrical properties. • Dissolution-precipitation mechanisms involving the Cold Sintering Process. [ABSTRACT FROM AUTHOR]

A disruptive sintering technique, Cold Sintering Process (CSP), has been used to produce cold-sintered samples of Bi 2 O 3 -doped Li 1.3 Al 0.3 Ti 1.7 (PO 4) 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, Bi 2 O 3 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% Bi 2 O 3 (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 CO 2 emissions. [ABSTRACT FROM AUTHOR]

A NASICON-type Li 1+x Al x Ti 2-x(PO 4) 3 (LATP) cold-sintered solid electrolyte is reported with a dense structure, as a possible alternative the commonly recognized liquid organic electrolytes. A low-temperature sintering technology (below 200 °C) with a sintering additive, aid of acid solvent and high pressure is originally developed for preparing the solid electrolyte. In addition, the setup has been designed using in operando impedance technique simultaneously, the Cold Sintering Process (CSP) is monitored in order to explore the mechanism are taking place during the densification. As a result, an ionic conductivity as high as 4.48·10−5 S·cm−1, with a relative density of ∼82% has been achieved for 2 wt% Bi 2 O 3 and 25 wt% 3 m acid acetic solution, LATP powder, and sintered under 700 MPa and at 150 °C, reaching the highest value in published peer-reviewed literature. The cold-sintered ceramics without post-annealing high temperature treatments present kinetics limitations due to intergranular regions. Therefore, this bottleneck must be studied and overcome to achieve higher ionic conductivities at low temperatures. [Display omitted] • Modification strategies of ceramic electrolytes sintering are focused on. • Cold Sintering Process method to sinter x-Bi2O3:LATP solid electrolyte. • Combination of 3 cornerstones: sintering aid, CSP and in operando impedance. [ABSTRACT FROM AUTHOR]

In the present work, a Polymer-In-Ceramics (PIC) solid electrolyte based on Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 (LATP) and PEO n -LiTFSI (poly(ethylene oxide) - lithium bis(trifluoromethanesulfonyl)imide) is obtained via Cold Sintering Process (CSP), at a temperature of 150 °C without any post-heat treatment, this is 900 °C below the traditional sintering temperature. This novel study demonstrates the effect of the Transient Liquid Phase content (TLP) and the composition of the polymeric active filler on the final Composite Solid Electrolyte (CSE) properties, with the sintering process being monitored by in-operando Electrochemical Impedance Spectroscopy (EIS). Firstly, the 15 wt% of TLP is stated as the optimal liquid content based on the electrical answer and workability. Then, the (EO:Li+) molar ratio is studied from (1:1) to (8:1). The highest ionic conductivity of 1.04·10−4 S cm−1 and a relative density above 98% are achieved at room temperature when the TLP content is 15 wt% and the molar ratio (2:1), with the LATP content set in 90 wt%. Moreover, the activation energy (Ea) is drastically reduced, from 0.388 eV (LATP ceramic electrolyte) to 0.298 eV (PIC electrolyte), with a lithium transference number (t Li +) close to 1. Therefore, this research work proposes a potential solid electrolyte to substitute the traditional liquid electrolytes. • Modification strategies of ceramic electrolytes sintering are focused on. • Cold Sintering Process method to sinter LATP-based Composite Solid Electrolyte. • The future of ASSLBs using Polymer-in-Ceramic electrolytes is discussed. • PEO n -LiTFSI doping of ceramic electrolytes to improve the ionic conductivity. [ABSTRACT FROM AUTHOR]