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Abstract All‐solid‐state potassium batteries emerge as promising alternatives to lithium batteries, leveraging their high natural abundance and cost‐effectiveness. Developing potassium solid electrolytes (SEs) with high room‐temperature ionic conductivity is critical for realizing efficient potassium batteries. In this study, we present the synthesis of K_2.98Sb_0.91S_3.53Cl_0.47, showcasing a room‐temperature ionic conductivity of 0.32 mS/cm and a low activation energy of 0.26 eV. This represents an increase of over two orders of magnitude compared to the parent compound K₃SbS₄, marking the highest reported ionic conductivity for non‐oxide potassium SEs. Solid‐state³⁹K magic‐angle‐spinning nuclear magnetic resonance on K_2.98Sb_0.91S_3.53Cl_0.47reveals an increased population of mobile K⁺ions with fast dynamics. Ab initio molecular dynamics (AIMD) simulations further confirm a delocalized K⁺density and significantly enhanced K⁺diffusion. This work demonstrates diversification of the anion sublattice as an effective approach to enhance ion transport and highlights K_2.98Sb_0.91S_3.53Cl_0.47as a promising SE for all‐solid‐state potassium batteries. 

Abstract Polyanion rotations are often linked to cation diffusion, but the study of multiple polyanion systems is scarce due to the complexities in experimentally determining their dynamic interactions. This work focuses on BH₄‐based argyrodites, synthesized to achieve a high conductivity of 11 mS cm⁻¹. Advanced tools, including high‐resolution X‐ray diffraction, neutron pair distribution function analysis, and mutinuclear magic‐angle‐spinning nuclear magnetic resonance (NMR) spectroscopy and relaxometry, along with theoretical calculations, are employed to unravel the dynamic intricacies among the dual polyanion lattice and active charge carriers. The findings reveal that the anion sublattice of Li_5.07PS_4.07(BH₄)_1.93affords an even temporal distribution of Li among PS₄³⁻and BH₄⁻, suggesting minimal trapping of the charge carriers. Moreover, the NMR relaxometry unveils rapid BH₄⁻rotation on the order of ∼GHz, affecting the slower rotation of neighboring PS₄³⁻at ∼100 MHz. The PS₄³⁻rotation synchronizes with Li⁺motion and drives superionic transport. Thus, the PS₄³⁻and BH₄⁻polyanions act as two‐staged dual motors, facilitating rapid Li⁺diffusion. 

Abstract Localized atomistic disorder in halide‐based solid electrolytes (SEs) can be leveraged to boost Li⁺mobility. In this study, Li⁺transport in structurally modified Li₃HoCl₆, via Br⁻introduction and Li⁺deficiency, is explored. The optimized Li_3‐3yHo_1+yCl_6‐xBr_xachieves an ionic conductivity of 3.8 mS cm⁻¹at 25 °C, the highest reported for holmium halide materials.^6,7Li nuclear magnetic resonance and relaxometry investigations unveil enhanced ion dynamics with bromination, attaining a Li⁺motional rate neighboring 116 MHz. X‐ray diffraction analyses reveal mixed‐anion‐induced phase transitions with disproportionate octahedral expansions and distortions, creating Ho‐free planes with favorable energetics for Li⁺migration. Bond valence site energy analysis highlights preferred Li⁺transport pathways, particularly in structural planes devoid of Ho³⁺blocking effects. Molecular dynamics simulations corroborate enhanced Li⁺diffusion with Br⁻introduction into Li₃HoCl₆. Li‐Ho electrostatic repulsions in the (001) plane presumably drive Li⁺diffusion into the Ho‐free (002) layer, enabling rapid intraplanar Li⁺motion and exchange between the 2d and 4h sites. Li_3‐3yHo_1+yCl_6‐xBr_xalso demonstrates good battery cycling stability. These findings offer valuable insights into the intricate correlations between structure and ion transport and will help guide the design of high‐performance fast ion conductors for all‐solid‐state batteries. 

Abstract The performance of all‐solid‐state batteries (ASSBs) relies on the Li⁺transport and stability characteristics of solid electrolytes (SEs). Li₃PS₄is 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⁻¹with an activation energy of 0.34 eV for Li₃PS_4−xO_x(x = 0.31). Optimal O substitution transforms Li⁺transport from 2D to 3D pathways with increased ion mobility. Li₃PS_3.69O_0.31exhibits improvements in the critical current density and stability against Li metal and retains its electrochemical stability window compared with Li₃PS₄. The practical implementation of Li₃PS_3.69O_0.31in ASSBs half‐cells, particularly when coupled with TiS₂as 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 To enhance Li⁺transport in all‐solid‐state batteries (ASSBs), harnessing localized nanoscale disorder can be instrumental, especially in sulfide‐based solid electrolytes (SEs). In this investigation, the transformation of the model SE, Li₃PS₄, is delved into via the introduction of LiBr.³¹P nuclear magnetic resonance (NMR)unveils the emergence of a glassy PS₄³⁻network interspersed with Br⁻.⁶Li NMR corroborates swift Li⁺migration between PS₄³⁻and Br⁻, with increased Li⁺mobility indicated by NMR relaxation measurements. A more than fourfold enhancement in ionic conductivity is observed upon LiBr incorporation into Li₃PS₄. Moreover, a notable decrease in activation energy underscores the pivotal role of Br⁻incorporation within the anionic lattice, effectively reducing the energy barrier for ion conduction and transitioning Li⁺transport dimensionality from 2D to 3D. The compatibility of Li₃PS₄with Li metal is improved through LiBr incorporation, alongside an increase in critical current density from 0.34 to 0.50 mA cm⁻², while preserving the electrochemical stability window. ASSBs with 3Li₃PS₄:LiBr as the SE  showcase robust high‐rate and long‐term cycling performance. These findings collectively indicate the potential of lithium halide incorporation as a promising avenue to enhance the ionic conductivity and stability of SEs. 

Abstract 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, Li_5.3PS_4.3Cl_1.7−xBr_x(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⁻¹and a low activation energy of 0.155 eV realized in Li_5.3PS_4.3Cl_0.7Br, 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 Lattice oxygen redox yields anomalous capacity and can significantly increase the energy density of layered Li‐rich transition metal oxide cathodes, garnering tremendous interest. However, the mechanism behind O redox in these cathode materials is still under debate, in part due to the challenges in directly observing O and following associated changes upon electrochemical cycling. Here, with¹⁷O NMR as a direct probe of O activities, it is demonstrated that stacking faults enhance O redox participation compared with Li₂MnO₃domains without stacking faults. This work is concluded by combining both ex situ and in situ¹⁷O NMR to investigate the evolution of O at 4i, 8j sites from monoclinicC2/mand 6c(1), 6c(2), 6c(3) sites from the stacking faults (P3₁12). These measurements are further corroborated and explained by first‐principles calculations finding a stabilization effect of stacking faults in delithiated Li₂MnO₃. In situ¹⁷O NMR tracks O activities with temporal resolution and provides a quantitative determination of reversible O redox versus irreversible processes that form short covalent OO bonds. This work provides valuable insights into the O redox reactions in Li‐excess layered cathodes, which may inspire new material design for cathodes with high specific capacity. 

Polycrystalline ion conductors are widely used as solid electrolytes in energy storage technologies. However, they often exhibit poor ion transport across grain boundaries and pores. This work demonstrates that strategically tuning the mesoscale microstructures, including pore size, pore distribution, and chemical compositions of grain boundaries, can improve ion transport. Using LiTa₂PO₈as a case study, we have shown that the combination of LiF as a sintering agent with Hf⁴⁺implantation improves grain-grain contact, resulting in smaller, evenly distributed pores, reduced chemical contrast, and minimized nonconductive impurities. A suite of techniques has been used to decouple the effects of LiF and Hf⁴⁺. Specifically, LiF modifies particle shape and breaks large pores into smaller ones, while Hf⁴⁺addresses the chemical mismatches between grains and grain boundaries. Consequently, this approach achieves nearly two orders of magnitude improvement in ion conduction. Tuning mesoscale structures offers a cost-effective method for enhancing ion transport in polycrystalline systems and has notable implications for synthesizing high-performance ionic materials. 

The Cl–S mixed-anion sublattice of Li_1.6AlCl_3.4S_0.6creates face- and edge-shared octahedra that connect to form 3D ion conduction pathways with low activation energy barriers.