Search

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]

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, with 17O NMR as a direct probe of O activities, it is demonstrated that stacking faults enhance O redox participation compared with Li2MnO3 domains without stacking faults. This work is concluded by combining both ex situ and in situ 17O NMR to investigate the evolution of O at 4i, 8j sites from monoclinic C2/m and 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 situ 17O 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. [ABSTRACT FROM AUTHOR]

LiNiO2 (LNO) represents the end member in the compositional space of the LiNi1‐x‐yMnxCoyO2 (as x and y approach zero) cathode system. Despite its high theoretical specific capacity (275 mAh/g), LNO suffers from phase transitions with large volume change and unfavorable reactions upon electrochemical cycling, which restricts its practical use in the application of lithium‐ion batteries. While the contributing factor to the structural instability is commonly linked to the undesired volume collapse associated with the H2‐H3 phase transition, detailed analysis of structural evolution following the entire route of phase transitions (H1‐M‐H2‐H3) in real time under battery operating conditions remains a challenging task. In this work, we employ operando neutron diffraction to study the structural changes (crystal lattice, Li/Ni−O bond length, O−Ni−O bond angles, and LiO2/NiO2 layer thickness) of LNO cathode in a home‐built LixNiO2||graphite full cell during Li+ de‐/intercalation. In particular, the anomalous increase(decrease) of Ni−O(Li−O) bond length at high SOC (>∼85 %) in the H3 phase is discussed in the context of O2− (2p)→Ni4+(3d) negative charge transfer. [ABSTRACT FROM AUTHOR]

A thin solid electrolyte with a high Li+ conductivity is used to separate the metallic lithium anode and the cathode in an all‐solid‐state Li‐metal battery. However, most solid Li‐ion electrolytes have a small electrochemical stability window, large interfacial resistance, and cannot block lithium‐dendrite growth when lithium is plated on charging of the cell. Mg2+ stabilizes a rhombohedral NASICON‐structured solid electrolyte of the formula Li1.2Mg0.1Zr1.9(PO4)3 (LMZP). This solid electrolyte has Li‐ion conductivity two orders of magnitude higher at 25 °C than that of the triclinic LiZr2(PO4)3. 7Li and 6Li NMR confirm the Li‐ions in two different crystallographic sites of the NASICON framework with 85% of the Li‐ions having a relatively higher mobility than the other 15%. The anode–electrolyte interface is further investigated with symmetric Li/LMZP/Li cell testing, while the cathode–electrolyte interface is explored with an all‐solid‐state Li/LMZP/LiFePO4 cell. The enhanced performance of these cells enabled by the Li1.2Mg0.1Zr1.9(PO4)3 solid electrolyte is stable upon repeated charge/discharge cycling. [ABSTRACT FROM AUTHOR]

Li+‐conducting oxides are considered better ceramic fillers than Li+‐insulating oxides for improving Li+ conductivity in composite polymer electrolytes owing to their ability to conduct Li+ through the ceramic oxide as well as across the oxide/polymer interface. Here we use two Li+‐insulating oxides (fluorite Gd0.1Ce0.9O1.95 and perovskite La0.8Sr0.2Ga0.8Mg0.2O2.55) with a high concentration of oxygen vacancies to demonstrate two oxide/poly(ethylene oxide) (PEO)‐based polymer composite electrolytes, each with a Li+ conductivity above 10−4 S cm−1 at 30 °C. Li solid‐state NMR results show an increase in Li+ ions (>10 %) occupying the more mobile A2 environment in the composite electrolytes. This increase in A2‐site occupancy originates from the strong interaction between the O2− of Li‐salt anion and the surface oxygen vacancies of each oxide and contributes to the more facile Li+ transport. All‐solid‐state Li‐metal cells with these composite electrolytes demonstrate a small interfacial resistance with good cycling performance at 35 °C. [ABSTRACT FROM AUTHOR]