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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.

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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.

By subjecting amorphous titanium dioxide (TiO 2 ) colloidal spheres as scaffold to a two-step external template-free hydrothermal treatment, anatase TiO 2 hollow spheres with an average diameter of 410nm and shell thickness of 65 nm were successfully yielded. Such hollow TiO 2 nanostructures possessed 10 large surface area, abundant active sites and reduced Li ion diffusion path, and thus was highly favorable for use in TiO 2 -based lithium ion battery (LIB). Electrochemical measurements revealed that asprepared TiO 2 hollow spheres exhibited specific discharge capacities of 296, 185, 118, 66 and 37mAhg -1 at 0.1C, 1C, 2C, 5C and 10C, respectively. This is in sharp contrast to those much lower values obtained in TiO 2 solid nanoparticles (i.e., 182, 119, 81, 43 18 mAhg -1 at discharge rates of 15 0.1C, 1C, 2C, 5C and 10C, respectively). Interestingly, TiO 2 hollow spheres showed a large irreversible capacity loss and relatively low cycling performance due to the residual chemisorbed water in TiO 2 and hydroxyl groups present on the TiO 2 surface. A solid electrolyte interface (SEI) layer composed primarily of Li 2 CO 3 , lithium alkyl carbonates and organic phosphates was thus formed on the surface of hollow TiO 2 spheres, thereby leading to an increased internal cell 20 impedance and the decreased rate and cycling performance. The subsequent high-temperature annealing effectively removed chemisorbed water and hydroxyls on the TiO 2 surface. As a consequence, annealed TiO 2 hollow spheres rendered markedly improved rate stability and cycle performance in the resulting TiO 2 -based LIBs. The specific discharge capacities at rates of 5C and 10C were 77mAhg -1 and 50mAhg -1 , which are much larger than those obtained from as-prepared TiO 2 hollow 25 spheres. Moreover, compared to only 42.1% for as-prepared hollow TiO 2 spheres, a capacity retention as high as 93.5% over 200 cycles at 1C was achieved for annealed hollow TiO 2 spheres. 60

Fabrication and applications of lightweight, high load-bearing, thermally stable composite materials would benefit greatly from leveraging the high mechanical strength of ceramic nanowires (NWs) over conventional particles or micrometer-scale fibers. However, conventional synthesis routes to produce NWs are rather expensive. Recently we discovered a novel method to directly convert certain bulk bimetallic alloys to metal-organic NWs at ambient temperature and pressure. This method was demonstrated by a facile transformation of polycrystalline aluminum-lithium (AlLi) alloy particles to aluminum alkoxide NWs, which can be further transformed to mechanically robust aluminum oxide (AlO) NWs. However, the transformation mechanisms have not been clearly understood. Here, we conducted advanced materials characterization (via electron microscopy and nuclear magnetic resonance spectroscopies) and chemo-mechanical modeling to elucidate key physical and chemical mechanisms responsible for NWs formation. We further demonstrated that the content of Li metal in the AlLi alloy could be reduced to about 4 wt % without compromising the success of the NWs synthesis. This new mechanistic understanding may open new avenues for large-scale, low-cost manufacturing of NWs and nanofibers for a broad range of composites and flexible ceramic membranes.

In article number https://doi.org/10.1002/aenm.201700971, Oleg Borodin, Gleb Yushin, and co‐workers prepare the lithium hydroxyl chloride and deprotonated lithium hydroxychlorides to reveal the influence of the proton of the hydroxyl group on the Li ion conductivities in these types of compounds. Born‐Oppenheimer molecular dynamics simulations show an excellent agreement with experimental results and reveal an unexpected mechanism, which involves the rotation of the hydroxyl group. Rotating doors in buildings may serve as simple mechanical analogies for Li+ motion.

Technologically important composites with enhanced thermal and mechanical properties rely on the reinforcement by the high specific strength ceramic nanofibers or nanowires (NWs) with high aspect ratios. However, conventional synthesis routes to produce such ceramic NWs have prohibitively high cost. Now, direct transformation of bulk Mg‐Li alloys into Mg alkoxide NWs is demonstrated without the use of catalysts, templates, expensive or toxic chemicals, or any external stimuli. This mechanism proceeds through the minimization of strain energy at the boundary of phase transformation front leading to the formation of ultra‐long NWs with tunable dimensions. Such alkoxide NWs can be easily converted in air into ceramic MgO NWs with similar dimensions. The impact of the alloy grain size and Li content, synthesis temperature, inductive and steric effects of alkoxide groups on the diameter, length, composition, ductility, and oxidation of the produced NWs is discussed.