Abstract
In the present study, we have successfully synthesized BH4-substituted lithium argyrodites by dry ball milling as well as by wet mechanochemical processing. Simultaneous substitution of BH4 and Cl/Br/I for non-bridging sulfur in the argyrodite structure was also possible by ball milling. The ionic conductivity of these BH4-substituted argyrodite-type electrolytes exhibit a maximum conductivity of up to 16.4 mS/cm at 25°C in their cold-pressed state. We confirmed the composition and distribution of substituted ions in the crystal structure by XRD Rietveld refinement and investigated the movement of lithium ions and the substitution of BH4 by solid-state NMR. The thermal stability and decomposition product at high temperatures have also been analyzed by thermo-gravimetric analysis/mass spectrometry (TGA/MS) and XRD. To characterize the electrochemical properties of BH4-substituted argyrodite-type electrolytes, we have used various analytical tools such as electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Li symmetric cell, c-rate and long-term cycle tests of full cells with LiNbO3-coated NCM811 as a cathode, have also been done. The test results so far have shown very high ionic conductivity, excellent electrochemical stability and much higher critical current density compared with similar cells with commercial Li6PS5Cl as the electrolyte.
Published Version
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