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The performance of all‐solid‐state batteries (ASSBs) relies on the Li+ transport and stability characteristics of solid electrolytes (SEs). Li3PS4 is notable for its stability against lithium metal, yet its ionic conductivity remains a limiting factor. This study leverages local structural disorder via O substitution to achieve an ionic conductivity of 1.38 mS cm−1 with an activation energy of 0.34 eV for Li3PS4−xOx (x = 0.31). Optimal O substitution transforms Li+ transport from 2D to 3D pathways with increased ion mobility. Li3PS3.69O0.31 exhibits improvements in the critical current density and stability against Li metal and retains its electrochemical stability window compared with Li3PS4. The practical implementation of Li3PS3.69O0.31 in ASSBs half‐cells, particularly when coupled with TiS2 as the cathode active material, demonstrates substantially enhanced capacity and rate performance. This work elucidates the utility of introducing local structural disorder to ameliorate SE properties and highlights the benefits of strategically combining the inherent strengths of sulfides and oxides via creating oxysulfide SEs. [ABSTRACT FROM AUTHOR]

The performance of all‐solid‐state batteries (ASSBs) relies on the Li+ transport and stability characteristics of solid electrolytes (SEs). Li3PS4 is notable for its stability against lithium metal, yet its ionic conductivity remains a limiting factor. This study leverages local structural disorder via O substitution to achieve an ionic conductivity of 1.38 mS cm−1 with an activation energy of 0.34 eV for Li3PS4−xOx (x = 0.31). Optimal O substitution transforms Li+ transport from 2D to 3D pathways with increased ion mobility. Li3PS3.69O0.31 exhibits improvements in the critical current density and stability against Li metal and retains its electrochemical stability window compared with Li3PS4. The practical implementation of Li3PS3.69O0.31 in ASSBs half‐cells, particularly when coupled with TiS2 as the cathode active material, demonstrates substantially enhanced capacity and rate performance. This work elucidates the utility of introducing local structural disorder to ameliorate SE properties and highlights the benefits of strategically combining the inherent strengths of sulfides and oxides via creating oxysulfide SEs. [ABSTRACT FROM AUTHOR]

The correlation between lattice chemistry and cation migration in high‐entropy Li+ conductors is not fully understood due to challenges in characterizing anion disorder. To address this issue, argyrodite family of Li+ conductors, which enables structural engineering of the anion lattice, is investigated. Specifically, new argyrodites, Li5.3PS4.3Cl1.7−xBrx (0 ≤ x ≤ 1.7), with varying anion entropy are synthesized and X‐ray diffraction, neutron scattering, and multinuclear high‐resolution solid‐state nuclear magnetic resonance (NMR) are used to determine the resulting structures. Ion and lattice dynamics are determined using variable‐temperature multinuclear NMR relaxometry and maximum entropy method analysis of neutron scattering, aided by constrained ab initio molecular dynamics calculations. 15 atomic configurations of anion arrangements are identified, producing a wide range of local lattice dynamics. High entropy in the lattice structure, composition, and dynamics stabilize otherwise metastable Li‐deficient structures and flatten the energy landscape for cation migration. This resulted in the highest room‐temperature ionic conductivity of 26 mS cm−1 and a low activation energy of 0.155 eV realized in Li5.3PS4.3Cl0.7Br, where anion disorder is maximized. This study sheds light on the complex structure–property relationships of high‐entropy superionic conductors, highlighting the significance of heterogeneity in lattice dynamics. [ABSTRACT FROM AUTHOR]

Antiperovskite structure compounds (X3AB, where X is an alkali cation and A and B are anions) have the potential for highly correlated motion between the cation and a cluster anion on the A or B site. This so‐called "paddle‐wheel" mechanism may be the basis for enhanced cation mobility in solid electrolytes. Through combined experiments and modeling, the first instance of a double paddle‐wheel mechanism, leading to fast sodium ion conduction in the antiperovskite Na3−xO1−x(NH2)x(BH4), is shown. As the concentration of amide (NH2−) cluster anions is increased, large positive deviations in ionic conductivity above that predicted from a vacancy diffusion model are observed. Using electrochemical impedance spectroscopy, powder X‐ray diffraction, synchrotron X‐ray diffraction, neutron diffraction, ab initio molecular dynamics simulations, and NMR, the cluster anion rotational dynamics are characterized and it is found that cation mobility is influenced by the rotation of both NH2− and BH4− species, resulting in sodium ion conductivity a factor of 102 higher at x = 1 than expected for the vacancy mechanism alone. Generalization of this phenomenon to other compounds could accelerate fast ion conductor exploration and design. [ABSTRACT FROM AUTHOR]

The correlation between lattice chemistry and cation migration in high‐entropy Li+ conductors is not fully understood due to challenges in characterizing anion disorder. To address this issue, argyrodite family of Li+ conductors, which enables structural engineering of the anion lattice, is investigated. Specifically, new argyrodites, Li5.3PS4.3Cl1.7−xBrx (0 ≤ x ≤ 1.7), with varying anion entropy are synthesized and X‐ray diffraction, neutron scattering, and multinuclear high‐resolution solid‐state nuclear magnetic resonance (NMR) are used to determine the resulting structures. Ion and lattice dynamics are determined using variable‐temperature multinuclear NMR relaxometry and maximum entropy method analysis of neutron scattering, aided by constrained ab initio molecular dynamics calculations. 15 atomic configurations of anion arrangements are identified, producing a wide range of local lattice dynamics. High entropy in the lattice structure, composition, and dynamics stabilize otherwise metastable Li‐deficient structures and flatten the energy landscape for cation migration. This resulted in the highest room‐temperature ionic conductivity of 26 mS cm−1 and a low activation energy of 0.155 eV realized in Li5.3PS4.3Cl0.7Br, where anion disorder is maximized. This study sheds light on the complex structure–property relationships of high‐entropy superionic conductors, highlighting the significance of heterogeneity in lattice dynamics. [ABSTRACT FROM AUTHOR]