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The development of improved solid electrolytes (SEs) plays a crucial role in the advancement of bulk‐type solid‐state battery (SSB) technologies. In recent years, multicomponent or high‐entropy SEs are gaining increased attention for their advantageous charge‐transport and (electro)chemical properties. However, a comprehensive understanding of how configurational entropy affects ionic conductivity is largely lacking. Herein we investigate a series of multication‐substituted lithium argyrodites with the general formula Li6+x[M1aM2bM3cM4d]S5I, with M being P, Si, Ge, and Sb. Structure‐property relationships related to ion mobility are probed using a combination of diffraction techniques, solid‐state nuclear magnetic resonance spectroscopy, and charge‐transport measurements. We present, to the best of our knowledge, the first experimental evidence of a direct correlation between occupational disorder in the cationic host lattice and lithium transport. By controlling the configurational entropy through compositional design, high bulk ionic conductivities up to 18 mS cm−1 at room temperature are achieved for optimized lithium argyrodites. Our results indicate the possibility of improving ionic conductivity in ceramic ion conductors via entropy engineering, overcoming compositional limitations for the design of advanced electrolytes and opening up new avenues in the field. [ABSTRACT FROM AUTHOR]

Crystallization of polymers from entangled melts generally leads to the formation of semicrystalline materials with a nanoscopic morphology consisting of stacks of alternating crystalline and amorphous layers. The factors controlling the thickness of the crystalline layers are well studied; however, there is no quantitative understanding of the thickness of the amorphous layers. We elucidate the effect of entanglements on the semicrystalline morphology by the use of a series of model blends of high-molecular-weight polymers with unentangled oligomers leading to a reduced entanglement density in the melt as characterized by rheological measurements. Small-angle X-ray scattering experiments after isothermal crystallization reveal a reduced thickness of the amorphous layers, while the crystal thickness remains largely unaffected. We introduce a simple, yet quantitative model without adjustable parameters, according to which the measured thickness of the amorphous layers adjusts itself in such a way that the entanglement concentration reaches a specific maximum value. Furthermore, our model suggests an explanation for the large supercooling that is typically required for crystallization of polymers if entanglements cannot be dissolved during crystallization. [ABSTRACT FROM AUTHOR]

Superionic conductors are key components of solid-state batteries (SSBs). Multicomponent or high-entropy materials, offering a vast compositional space for tailoring properties, have recently attracted attention as novel solid electrolytes (SEs). However, the influence of synthetic parameters on ionic conductivity in compositionally complex SEs has not yet been investigated. Herein, the effect of cooling rate after high-temperature annealing on charge transport in the multicationic substituted lithium argyrodite Li 6.5 [P 0.25 Si 0.25 Ge 0.25 Sb 0.25 ]S 5 I is reported. It is demonstrated that a room-temperature ionic conductivity of ∼12 mS cm -1 can be achieved upon cooling at a moderate rate, superior to that of fast- and slow-cooled samples. To rationalize the findings, the material is probed using powder diffraction, nuclear magnetic resonance and X-ray photoelectron spectroscopy combined with electrochemical methods. In the case of moderate cooling rate, favorable structural (bulk) and compositional (surface) characteristics for lithium diffusion evolve. Li 6.5 [P 0.25 Si 0.25 Ge 0.25 Sb 0.25 ]S 5 I is also electrochemically tested in pellet-type SSBs with a layered Ni-rich oxide cathode. Although delivering larger specific capacities than Li 6 PS 5 Cl-based cells at high current rates, the lower (electro)chemical stability of the high-entropy Li-ion conductor led to pronounced capacity fading. The research data indicate that subtle changes in bulk structure and surface composition strongly affect the electrical conductivity of high-entropy lithium argyrodites., (© 2023 The Authors. Small published by Wiley‐VCH GmbH.)