No abstract

Li‐halide hydroxides (Li2OHX) and Li‐oxyhalides (Li3OX) have emerged as new classes of low‐cost, lightweight solid state electrolytes (SSE) showing promising Li‐ion conductivities. The similarity in the lattice parameters between them, careless synthesis, and insufficient rigor in characterization often lead to erroneous interpretations of their compositions. Finally, moisture remaining in the synthesis or cell assembling environment and variability in the equivalent circuit models additionally contribute to significant errors in their properties. Thus, there remains a controversy about the real values of Li‐ion conductivities in such SSEs. Here an ultra‐fast synthesis and comprehensive material characterization is utilized to report on the ionic conductivities of contaminant‐free Li2+xOH1−xCl (x=0‐0.7), and Li2OHBr not exceeding 10‐4 S cm‐1 at 110 °C. Using powerful combination of experimental and numerical approaches, it is demonstrated that the presence of H in these SSEs yields significantly higher Li+ ‐ionic conductivity. Born‐Oppenheimer molecular dynamics simulations show excellent agreement with experimental results and reveal an unexpected mechanism for faster Li+ transport. It involves rotation of a short OH‐group in SSEs, which opens lower‐energy pathways for the formation of Frenkel defects and highly‐correlated Li+ jumps. These findings will reduce the existing confusions and show new avenues for tuning SSE compositions for further improved Li‐ion conductivities.

No abstract

Lithium sulfide (Li2S) cathodes have been viewed as very promising candidates for next-generation lightweight Li and Li-ion batteries.

Low‐melting‐point solid‐state electrolytes (SSE) are critically important for low‐cost manufacturing of all‐solid‐state batteries. Lithium hydroxychloride (Li2OHCl) is a promising material within the SSE domain due to its low melting point (mp < 300 °C), cheap ingredients (Li, H, O, and Cl), and rapid synthesis. Another unique feature of this compound is the presence of Li vacancies and rotating hydroxyl groups which promote Li‐ion diffusion, yet the role of the protons in the ion transport remains poorly understood. To examine lithium and proton dynamics, a set of solid‐state NMR experiments are conducted, such as magic‐angle spinning 7Li NMR, static 7Li and 1H NMR, and spin‐lattice T1(7Li)/T1(1H) relaxation experiments. It is determined that only Li+ contributes to long‐range ion transport, while H+ dynamics is constrained to an incomplete isotropic rotation of the OH group. The results uncover detailed mechanistic understanding of the ion transport in Li2OHCl. It is shown that two distinct phases of ionic motions appear at low and elevated temperatures, and that the rotation of the OH group controls Li+ and H+ dynamics in both phases. The model based on the NMR experiments is fully consistent with crystallographic information, ionic conductivity measurements, and Born–Oppenheimer molecular dynamic simulations.

Lithium-metal fluoride batteries promise significantly higher energy density than the state-ofthe-art lithium-ion batteries and lithium-sulfur batteries. Unfortunately, commercialization of metal fluoride cathodes is prevented by their high resistance, irreversible structural change, and rapid degradation. In this study, we demonstrate substanial boost in metal fluoride (MF) cathode stability by designing nanostructure with two layers of protective shells -one deposited ex-situ and the other in-situ. Such methodology achieves over 90% capacity retention after 300 charge-discharge cycles, This article is protected by copyright. All rights reserved.3 producing the first report on FeF 3 as a cathode material, where a very high capacity utilization in combination with excellent stability is approaching to the level needed for practical applications of FeF 3 . The CEI containing lithium oxalate and B-F bond containing anions is found to effectively protect the cathode material from direct contact with electrolytes, thus greatly suppressing the dissolution of Fe. Quantum chemistry (QC) and molecular dynamics (MD) calculations provide unique insights into the mechanisms of CEI layer formation. As a result, our work not only demonstrates unprecedented performances, but also provides the readers with a better fundamental understanding of electrochemical behavior of MF cathodes and the positive impact observed with the application of a LiBoB salt in the electrolyte.

Free-standing, high-capacity Li2 S electrodes with capacity loadings in the range from 1.5 to 3.8 mA h cm(-2) are produced by using infiltration of active materials into porous carbonized biomass sheets. The proposed electrode design can be effectively utilized for the low-cost fabrication of flexible lithium batteries with high specific energy.

Unconventional superconductivity arising from the interplay between strong spin–orbit coupling and magnetism is an intensive area of research. One form of unconventional superconductivity arises when Cooper pairs subjected to a magnetic exchange coupling acquire a finite momentum. Here, we report on a signature of finite momentum Cooper pairing in the three-dimensional topological insulator Bi2Se3. We apply in-plane and out-of-plane magnetic fields to proximity-coupled Bi2Se3 and find that the in-plane field creates a spatially oscillating superconducting order parameter in the junction as evidenced by the emergence of an anomalous Fraunhofer pattern. We describe how the anomalous Fraunhofer patterns evolve for different device parameters, and we use this to understand the microscopic origin of the oscillating order parameter. The agreement between the experimental data and simulations shows that the finite momentum pairing originates from the coexistence of the Zeeman effect and Aharonov–Bohm flux.