Investigating\nthe Influence of Transition Metal Substitution\nin Lithium Argyrodites on Structure, Transport, and Solid-State Battery\nPerformance

Lithium\nargyrodites have gained significant attention as candidates\nfor solid electrolytes in solid-state batteries due to their superior\nionic conductivities and favorable mechanical properties. However,\nduring charging, oxidative decomposition reactions occur at the interface\nbetween the solid electrolyte and cathode active material, which impede\ncell performance. In this study, transition metal substitution of\nthe solid electrolyte is investigated with the intention of tuning\nthe composition of the cathode electrolyte interphase (CEI) and thereby\nimproving the cycling performance. Hence, the Li<sub>5.5–2<i>x</i></sub>Zn<i><sub>x</sub></i>PS<sub>4.5</sub>Cl<sub>1.5</sub> (0 ≤ <i>x</i> ≤ 0.15) and Li<sub>6–2<i>x</i></sub>Zn<i><sub>x</sub></i>PS<sub>5</sub>Br (0 ≤ <i>x</i> ≤ 0.15) substitution\nseries are investigated to elucidate how substitution affects structure,\nLi<sup>+</sup> transport, and the performance of the materials as\ncatholytes in solid-state batteries. Corefinement of the neutron and\npowder X-ray diffraction data unveils the occupation of Li<sup>+</sup> positions by Zn<sup>2+</sup>. This leads to blocking of Li<sup>+</sup> transport pathways within the Li<sup>+</sup> cages causing a decrease\nof ionic conductivities along with increasing activation energies\nfor Li<sup>+</sup> transport. By using a combination of cycling experiments,\nimpedance spectroscopy and X-ray photoelectron spectroscopy, the composition\nof the CEI and the state-of-charge dependence of the CEI growth when\nusing Li<sub>5.5–2<i>x</i></sub>Zn<i><sub>x</sub></i>PS<sub>4.5</sub>Cl<sub>1.5</sub>|NCM-83 composites was investigated\nin half-cells, revealing that Zn<sup>2+</sup> substitution leads to\nfaster decomposition kinetics and affects the CEI composition. Overall,\nthis work explores the influence of Li<sup>+</sup> substitution by\nZn<sup>2+</sup> on structure and transport in lithium argyrodites\nand the potential of transition metal substitutions as means to tune\nthe kinetics of CEI growth, the CEI composition, and thereby cell\nperformance.