Effect of Temperature during Open Vessel Sintering on Li₆PS₅Cl Solid-State Electrolyte Powders for Use in Cathode Composite Electrodes

Abstract

The sulfide solid electrolyte Li 6 PS 5 Cl has been shown to be an ideal candidate for use in composite electrodes for all solid-state lithium-ion batteries due to its high ionic conductivity, low activation energy, and rapid processability in solvents (solution-based processing). Many reports for solution-based processing of Li 6 PS 5 Cl required the electrolyte to be densified or sealed inside of a closed-quartz vessel prior to a final high-temperature sintering step. This pre-sintering step is useful for understanding the full electrochemical properties of the electrolyte but provides little information about usable electrolyte powders for commercialization. Modern applications of solid electrolyte powders require a feedstock of powdered electrolyte, which can be processed by tape-casting, screen-printing, aerosol deposition, electrophoretic deposition, and hot powder rolling. The lack of information regarding the sintering of Li 6 PS 5 Cl powders for bulk processing warrants an investigation into open vessel sintering of solely the Li 6 PS 5 Cl electrolyte powders, which can later be used in composite electrodes. This research uses a solution-based processing technique to synthesize Li 6 PS 5 Cl prior to sintering in open-top borosilicate glass containers. Here we show the effects that sintering temperatures have on Li 6 PS 5 Cl electrolyte powders during open-vessel sintering using X-ray diffraction, scanning electron microscopy, and Raman spectroscopy for morphological analysis. Electrochemical characterization was performed using AC electrical impedance spectroscopy, cyclic voltammetry, and chronoamperometry. Lastly, a full solid-state electrochemical cell was constructed with a cathode composite electrode made from the Li 6 PS 5 Cl to illustrate the functionality of the electrolyte.

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