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Fluoride-ion conducting solid materials are applicable as solid electrolytes for sensing devices and next generation rechargeable batteries. Most of the previously reported materials have limited to the single-anion compounds such as fluorite-type, tysonite-type, and perovskite-type structures. These are suffered from further improvements by crystal structure modification which derives a paradigm shift in the material tailoring. Fluoride and sulfide ions prefer respective coordination environments because of the different ionic radii and electronegativity. This feature implies that fluorosulfide mixed-anion compounds have potential to form anion-ordering crystal structures with new fluoride-ion conducting layers. Herein, we have found that the fluorosulfide La2+xSr1−xF4+xS2 exhibits fluoride ion conduction. The presence of multiple anions results in the formation of anion-ordering two-dimensional crystal lattice with triple fluorite layers, which cannot be realized for metal fluorides. Sulfide ions in the crystal structure increases the number of interstitial sites of fluoride ions, forming fluoride ion conduction pathway.

A high anionic conductivity of ∼3.5 × 10–3 S cm–1 at room temperature is achieved for PbxSn2–xF4 (x = 1.21) obtained by annealing a mechanically milled PbF2/SnF2 mixture at 400 °C. The observed syn...

Conversion-type iron trifluoride (FeF3) has attracted considerable attention as a positive electrode material for lithium secondary batteries due to its high energy density and low cost. However, t...

Li-rich type manganese oxides are one of the most promising cathodes for lithium-ion batteries in recent years; thanks to their high energy density. In these cathodes, partial substitution of manga...

Li2MnO3, an electrode material for Li ion batteries, belongs to the C2/m space group and is known to have a cubic-close-packed (ABC...) layered structure, in which the transition-metal layer is supposed to have an ordered atomic arrangement with Li atoms at the 2b site and Mn atoms at the 4g site. However, recently, it has been reported that this compound usually does not exhibit such an ideal structure and instead contains a large number of structural defects, not only stacking faults but also mixing of Li and Mn atoms between the 2b and 4g sites. To elucidate the effect of such structural defects on the electrochemical behavior, we examined the crystal structure of Li2MnO3 synthesized at various temperatures by simultaneously analyzing the stacking faults and cation mixing using FAULTS, a Rietveld code. Our examination showed that the crystals consist of both disordered and ordered domains; the disordered domains contain a large number of stacking faults along the c axis and have considerable Li/Mn atomic mixing within the transition-metal layer, whereas the ordered domains have almost no defects. At low synthesis temperatures, the disordered domains are dominant. However, the ordered domains increase at the expense of the disordered domains above 770 °C and become dominant at higher temperatures. It is also found that the degree of cation mixing in the disordered domains remains almost constant irrespective of synthesis temperature. The crystalline defects such as stacking faults or Li/Mn cation mixing are expected to promote the formation of smooth Li percolation paths. The decreasing of the disordered domains leads to dramatically decreased capacity. This indicates that the observed capacities of Li2MnO3 can be determined by the relative amounts of the ordered/disordered domains in the structure.

We examined the crystal structures of Li2(NixMn1-x)O3(-δ) (x = 0, 1/10, 1/6, and 1/4) to elucidate the relationship between the structure and electrochemical performance of the compounds using neutron and synchrotron X-ray powder diffraction analyses in combination. Our examination revealed that these crystals contain a large number of stacking faults and exhibit significant cation mixing in the transition-metal layers; the cation mixing becomes significant with an increase in the Ni concentration. Charge-discharge measurements showed that the replacement of Mn with Ni lowers the potential of the charge plateau and leads to higher charge-discharge capacities. From a topological point of view with regard to the atomic arrangement in the crystals, it is concluded that substituting Mn in Li2MnO3 with Ni promotes the formation of smooth Li percolation paths, thus increasing the number of active Li ions and improving the charge-discharge capacity.

To examine the dynamical origin of high ionic conductivity of (Li2S)70(P2S5)30 glass ceramic obtained by annealing (Li2S)70(P2S5)30 glass, we applied 6/7Li and 31P solid-state NMR. NMR line shapes and spin–lattice relaxation times (T1) were measured as a function of temperature. The results showed that dynamics of the PS4 tetrahedra and P2S7 ditetrahedra units in (Li2S)70(P2S5)30 glass ceramic is not appreciable at temperatures below ca. 310 K, where the ionic conductivity is low. At higher temperatures, however, significant motion especially for the P2S7 ditetrahedra unit is apparent in both of 31P-T1 and 31P MAS line shapes. Further, we applied the 31P–31P dipolar correlation experiment to examine the 31P line width, which is reduced by motion at higher temperatures. It was shown that the line width of the P2S7 unit is attributable to the distribution of local structures of and around the P2S7 ditetrahedra unit. With these, we concluded that the significant motional fluctuation of the P2S7 ditetrahedra ...

Delithiation and lithiation behaviors of ordered spinel LiNi0.5Mn1.5O4 and disordered spinel LiNi0.4Mn1.6O4 were investigated by using in situ (in operando) 7Li NMR and ex situ 6Li MAS NMR spectroscopy. The in situ 7Li monitoring of the ordered spinel revealed a clear appearance and subsequent disappearance of a new signal from the well-defined phase Li0.5Ni0.5Mn1.5O4, suggesting the two-phase reaction processes among Li1.0Ni0.5Mn1.5O4, Li0.5Ni0.5Mn1.5O4, and Li0.0Ni0.5Mn1.5O4. Also, for the disordered spinel, Li0.5Ni0.4Mn1.6O4 was identified with a broad distribution in Li environment. High-resolution 6Li MAS NMR spectra were also acquired for the delithiated and lithiated samples to understand the detailed local structure around Li ions. We suggested that the nominal Li-free phase Li0.0Ni0.5Mn1.5O4 can accommodate a small amount of Li ions in its structure. The tetragonal phases Li2.0Ni0.5Mn1.5O4 and Li2.0Ni0.4Mn1.6O4, which occurred when the cell was discharged down to 2.0 V, were very different in the Li environment from each other. It is found that 6, 7Li NMR is highly sensitive not only to the Ni/Mn ordering in LiNi0.5Mn1.5O4 but also to the valence changes of Ni and Mn on charge-discharge process.

We have studied the structural, electronic, and vibrational properties of potassium amidoborane (KAB, KNH2BH3) using density-functional theory (DFT) calculations. The optimized structural parameters of KAB were found to be in good agreement with the experimental data. The electronic structure calculations suggested the covalent characters of N–H, B–H, and N–B as well as the ionic character of K. Moreover, we computed the 39K NMR parameters of KAB and several K-containing materials by using the gauge-including projector augmented wave (GIPAW) approach, and found that the precise theoretical predictions and assignments of 39K NMR parameters were possible. The DFT-GIPAW calculations were successfully applied to assign the 39K MAS NMR signals of KAB to the crystallographically inequivalent K1 and K2 sites.

The thermal decomposition pathways of ammonia borane (AB, NH3BH3), lithium amidoborane (LiAB, LiNH2BH3), and potassium amidoborane (KAB, KNH2BH3) have been investigated in detail by using solid state 11B MAS NMR spectroscopy. During the first decomposition process of AB, the complex structural entities were observed, which have been attributed to polyaminoborane (PAB, (NH2BH2)n). On the other hand, polyiminoborane (PIB, (NHBH)n) formed in the second process showed a single 3-fold coordination IIIB signal above 125 °C, suggesting a [—B═N—]n network structure. LiAB and KAB did not show the PAB-like structure, and the PIB-like structure was directly formed by the hydrogen desorption. Quantitative analyses of the 11B NMR spectra suggested that the general route of the thermal decomposition of alkali metal amidoboranes (LiAB, NaAB, and KAB) is similar. Also, 39K MAS NMR spectra of KAB and its decomposition products indicated the formation of KH and an amorphous K–N–B–H phase during the hydrogen release.

A composite material of LiAl(NH2)4 and LiH irreversibly releases H2 gas by 6.1 mass% below 130 °C. The H2 desorption mechanism of the composite has been proposed, but it is still controversial beca...

Recently, alkali−metal amidoborane complexes have been highlighted as materials that satisfy many of the criteria required to make hydrogen-storage media. In this paper, ammonia borane was successfully activated by the existence of hybrid alkaline−metal hydrides. The desorption results showed that this activation strategy can significantly decrease the dehydrogenation temperature and, furthermore, can successfully suppress ammonia gas release and volume expansion. These results will be helpful for the design of future hydrogen-storage media.