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Thestructure of the nanoporous metal–organic frameworkCu3(BTC)2(BTC = 1,3,5-benzenetricarboxylate)with a variety of molecular guests was studied in situusing single crystal X-ray diffraction. By collecting crystal structuredata for a series of guests within the same host crystal, insightsinto the molecular interactions underpinning guest adsorption processeshave been gained. Adsorption behaviors are influenced strongly byboth enthalpic and entropic thermodynamic, as well as interpore steric(size-exclusion) effects, and we note correlations between guest attributesand these effects. Vapor adsorption measurements revealed a guestuptake capacity inversely proportional to guest size. Correspondingly,structural results show that guests reside in the smallest pores accessibleto them. Interpore steric effects for larger guests cause these tobe excluded from the smallest pores, and this corresponds to lowertotal uptake. Both hydrophilic and lipophilic small guests adsorbfavorably into the 5 Å diameter smallest pore of the material,with the number of guests in these pores dependent on guest size andtheir location, in turn dependent upon both guest–guest interactionsand competition between hydrogen-bonding interactions at the aperturesof the smallest pore and lipophilic interactions at the center ofthe smallest pore. Hydrophilic guests with lone electron pairs interactpreferentially with the coordinatively unsaturated Cu sites of thedesolvated framework, with the number of these depending on stericinteractions between neighboring bound guests and guest flexibility.Guest coordination at the Cu sites has a significant effect on theframework structure, increasing the Cu···Cu distancein the dinuclear unit, with the Cu3(BTC)2unitcell being smaller when guests that do not coordinate with the Cuare present, and in the case of cyclohexane, smaller than for thedesolvated framework. Overall, our comprehensive structural studyreconciles Cu3(BTC)2adsorption properties withthe underlying guest–host and guest–guest interactionsthat gives rise to these. [ABSTRACT FROM AUTHOR]

We used in situ neutron powder diffraction(NPD) to study the migrationof Li in Li4Ti5O12anodes with differentparticle sizes during battery cycling. The motivation of this workwas to uncover the mechanism of the increased capacity of the batterymade with a smaller-particle-sized anode. In real time, we monitoredthe anode lattice parameter, Li distribution, and oxidation stateof the Ti atom, and these suggested an increase in the rate of Liincorporation into the anode rather than a change in the migrationpathway as a result of the particle size reduction. The lattice ofthese anodes during continuous lithiation undergoes expansion followedby a gradual contraction and then expansion again. The measured latticeparameter changes were reconciled with Li occupation at specific siteswithin the Li4Ti5O12crystal structure,where Li migrates from the 8ato 16csites. Despite these similar Li-diffusion pathways, in larger-particle-sizedLi4Ti5O12the population of Li atthe 16csite is accompanied by Li depopulation fromthe 8asite, which is in contrast to the smaller-particle-sizedanode where our results suggest that Li at the 8asite is replenished faster than the rate of transfer of Li to the16csite. Fourier-difference nuclear density mapsof both anodes suggest that 32esites are involvedin the diffusion pathway of Li. NPD is again shown to be an excellenttool for the study of electrode materials for Li-ion batteries, particularlywhen it is used to probe real-time crystallographic changes of thematerials in an operating battery during charge–discharge cycling. [ABSTRACT FROM AUTHOR]

The favorable combination of fast-ionic conductivity and high electrochemical stability of Li-stuffed garnet type Li7La3Zr2O12 (LLZ) makes this material a promising candidate for applications as a solid-state electrolyte in high-energy-density batteries. However, a widespread technical use of LLZ is impeded by difficulty in reliable formation and densification of the pure fast-ion conducting phase. The present study of the phase-formation process enables rational fabrication procedures to be devised based on a thorough understanding of the complex phase formation of LLZ. In situ neutron powder diffraction monitoring of the phase formation revealed an influence of the partial melting of precursors on the formation of the fast-ion conducting phase, indicating that in the typical synthesis route LLZ is not formed in a solid-state reaction but from a partial carbonate melt that decomposes on further heating. The cooling rate critically influences lithium ordering and ionic conductivity. [ABSTRACT FROM AUTHOR]