Low mechanical pressure on amorphous gold thiolate coordination polymers allows the formation of transparent and red emissive glasses.

Herein, we report a detailed study on the high-energy density nanostructured Li4−xMn2O5–Li2O composite with a high discharge capacity of 355 mA h g−1, constituting the highest value reported to date for a lithium–manganese oxide electrode.

Framework oxides with the capacity to host mobile interstitial oxide anions are of interest as electrolytes in intermediate temperature solid oxide fuel cells (SOFCs). High performance materials of this type are currently limited to the anisotropic oxyapatite and melilite structure types. The langasite structure is based on a corner-shared tetrahedral network similar to that in melilite but is three-dimensionally connected by additional octahedral sites that bridge the layers by corner sharing. Using low-temperature synthesis, we introduce interstitial oxide charge carriers into the La3Ga5–x Ge1+x O14+x/2 langasites, attaining a higher defect content than reported in the lower dimensional oxyapatite and melilite systems in La3Ga3.5Ge2.5O14.75 (x = 1.5). Neutron diffraction and multinuclear solid state 17O and 71Ga NMR, supported by DFT calculations, show that the excess oxygen is accommodated by the formation of a (Ge,Ga)2O8 structural unit, formed from a pair of edge-sharing five-coordinated Ga/Ge square-based pyramidal sites bridged by the interstitial oxide and a strongly displaced framework oxide. This leads to more substantial local deformations of the structure than observed in the interstitial-doped melilite, enabled by the octahedral site whose primary coordination environment is little changed by formation of the pair of square-based pyramids from the originally tetrahedral sites. AC impedance spectroscopy on spark plasma sintered pellets showed that, despite its higher interstitial oxide content, the ionic conductivity of the La3Ga5–x Ge1+x O14+x/2 langasite family is lower than that of the corresponding melilites La1+y Sr1–y Ga3O7+y/2. The cooperative structural relaxation that forms the interstitial-based (Ga,Ge)2O8 units stabilizes higher defect concentrations than the single-site GaO5 trigonal bipyramids found in melilite but effectively traps the charge carriers. This highlights the importance of controlling local structural relaxation in the design of new framework electrolytes and suggests that the propensity of a framework to form extended units around defects will influence its ability to generate high mobility interstitial carriers.

The La1+x AE 1–x Ga3O7+x/2 melilite family (AE = Ca, Sr, and Ba and 0 ≤ x ≤ 0.64) demonstrates remarkable oxide ion conductivity due to the ability of its layered tetrahedral [Ga3O7+x/2] network to accommodate and transport interstitial oxide ions (Oint). Compositions of x > 0.65 with very high Oint concentrations (referred to here as “super-excess” compositions) have the potential to support correspondingly high ionic conductivities but have never before been accessed due to the limitations of conventional solid-state ceramic synthesis. Here, we report that fully substituted La2Ga3O7.5 (x = 1) melilite ceramics can be synthesized by direct crystallization of an under-cooled melt, demonstrating that super-excess compositions are accessible under suitable nonequilibrium reaction conditions. La2Ga3O7.5 is stable up to 830 °C and exhibits an ionic conductivity of 0.01 S·cm–1 at 800 °C, 3 orders of magnitude higher than the corresponding x = 0 end-member LaSrGa3O7 and close to the range exhibited by the current best-in-class La1.54Sr0.46Ga3O7.23 (0.1 S·cm–1). It crystallizes in an orthorhombic √2a × √2a × 2c expansion of the parent melilite cell in the space group Ima2 with full long-range ordering of Oint into chains within the [Ga3O7.5] layers. The emergence of this chain-like (1D) ordering within the 2D melilite framework, which appears to be an incipient feature of previously reported partially ordered melilites, is explained in terms of the underlying hexagonal topology of the structure. These results will enable the exploration of extended compositional ranges for the development of new solid oxide ion electrolytes with high concentrations of interstitial oxide charge carriers.

In this study, we conduct a comprehensive investigation of the effect of grain, grain boundary and interfacial resistance on the total Li-ion conductivity in Li2OHCl1-xBrx antiperovskite solid electrolytes. We highlight...

The irreversible loss of lithium from the cathode material during the first cycles of rechargeable Li‐ion batteries notably reduces the overall cell capacity. Here, a new family of sacrificial cathode additives based on Li2O:Li2/3Mn1/3O5/6 composites synthesized by mechanochemical alloying is reported. These nanocomposites display record (but irreversible) capacities within the Li–Mn–O systems studied, of up to 1157 mAh g−1, which represents an increase of over 300% of the originally reported capacity in Li2/3Mn1/3O5/6 disordered rock salts. Such a high irreversible capacity is achieved by the reaction between Li2O and Li2/3Mn1/3O5/6 during the first charge, where electrochemically active Li2O acts as a Li+ donor. A 13% increase of the LiFePO4 and LiCoO2 first charge gravimetric capacities is demonstrated by the addition of only 2 wt% of the nanosized composite in the cathode mixture. This result shows the great potential of these newly discovered sacrificial additives to counteract initial losses of Li+ ions and improve battery performance.

Single- and multi-shell upconverting nanocrystals, with their increasing numbers of applications, are characterized by core–shell and shell–shell interfaces, which are not yet fully understood. In this contribution, the magnitude of interface disorder in large single- and multi-shell nanocrystals is investigated.

The electrochemical performance of nanostructured Li4Mn2O5 (or rather the 0.93Li3.6–x Mn2.4O5.4–0.07Li2O composite) displaying an outstanding charge capacity of 350 mA h/g was recently reported. Interestingly, the removal of lithium from Li4Mn2O5 is found to take place beyond the oxidation limit of +4 for Mn in an octahedral environment. To characterize the nature of this extra capacity, we have approached the study of the redox chemistry and local structure of manganese in Li4Mn2O5 via a combination of X-ray absorption and emission spectroscopies at the manganese K-edge. To support our results, we have thoroughly characterized the composition of the materials at several potential values by inductively coupled plasma and online electrochemical mass spectrometry. Additionally, operando X-ray absorption near-edge structure studies, in excellent agreement with ex situ data, were carried out for the charge and discharge of the battery. Our results unequivocally rule out the participation of the Mn4+/Mn5+ redox couple and indicate the participation of oxygen in the electrochemistry. After the first charge, the battery cycles reversibly between the charged and discharged states, where the lithium exchange is mainly compensated by anionic redox.