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LiCoPO4 was synthesized by a solid-state and a supercritical solvo-thermal method. In situ X-ray absorption near-edge structure (XANES) experiments were evaluated on the basis of full-cycle experiments confirming the predominantly reversible character of the redox reaction. In situ X-ray diffraction (XRD) measurements were performed to follow structural changes during cycling indicating the existence of an intermediate phase upon cycling. The local phosphorus and lithium environments were studied by ex situ 31P and 7Li NMR at different states of charge proving the existence of an intermediate phase of the composition Li2/3CoPO4. On the basis of these findings, a model of the (de)lithiation process of LiCoPO4 is developed and discussed.

In this work, LiMnTiO4 (a structural analogue of classic spinel LiMn2O4) with a disordered cubic spinel structure (Fd3̅m) has been synthesized by a low-temperature sol–gel route. The as-obtained LiMnTiO4 exhibits excellent cycling stability in a wide voltage range from 1.5 to 4.8 V with high discharge capacities of 290, 250, and 140 mA h g–1 at a C/40, C/19, and 1C rate, respectively. Combined long- and short-range structural characterization techniques are used to reveal the correlation between structure and electrochemical behavior. During cycling, the charge/discharge profiles of LiMnTiO4 evolve from initially two well-separated plateaus into sloping regimes. In the early stage of discharge, LiMnTiO4 undergoes phase transitions from an initial spinel phase to mixtures of predominant rock-salt (Fm3̅m) and tetragonal (I41/amd) structures along with a decrease in crystallite size from 12 nm to 3 to 4 nm. During further cycling, the spinel/rock-salt phase transition was found to be reversible with the cubic framework remaining intact. The presence of the tetragonal phase after the first discharge suggests that the Mn3+ Jahn–Teller distortion is partially involved during lithiation from Li1–y Mn3+y TiO4 to Li1+x Mn3–x TiO4 and the fraction of such a tetragonal phase remains at about 30–40% during subsequent cycling.

Artificial light-harvesting systems have until now not been able to self-assemble into structures with a large photon capture cross-section that upon a stimulus reversibly can switch into an inactive state. Here we describe a simple and robust FLFL-dipeptide construct to which a meso-tetraphenylporphyrin has been appended and which self-assembles to fibrils, platelets or nanospheres depending on the solvent composition. The fibrils, functioning as quenched antennas, give intense excitonic couplets in the electronic circular dichroism spectra which are mirror imaged if the unnatural FDFD-analogue is used. By slightly increasing the solvent polarity, these light-harvesting fibres disassemble to spherical structures with silent electronic circular dichroism spectra but which fluoresce. Upon further dilution with the nonpolar solvent, the intense Cotton effects are recovered, thus proving a reversible switching. A single crystal X-ray structure shows a head-to-head arrangement of porphyrins that explains both their excitonic coupling and quenched fluorescence.