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Electrochemical properties of Li-excess electrode materials, Li1.2Co0.13Ni0.13Mn0.54O2, with different primary particle sizes are studied in Li cells, and phase transition behavior on continuous electrochemical cycles is systematically examined. Although the nanosize (<100 nm) sample delivers a large reversible capacity of 300 mAh g–1 at the initial cycle, capacity retention is not sufficient as a positive electrode material. Moreover, unfavorable phase transition, gradual enrichment of trivalent manganese ions, and lowering structural symmetry is not avoidable on electrochemical cycles for a nanosize sample, which is confirmed by combined techniques of synchrotron X-ray diffraction, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. A submicrosize sample also delivers a large reversible capacity of 250 mAh g–1 even though a slow activation process is observed accompanied with partial oxygen loss and migration oxide ions in the crystal lattice coupled with transition metal migration on the initial charge process. Such an unfavorable phase transition at room temperature is effectively suppressed by the use of a submicrosize sample with low surface area. However, suppression of the phase transition is found to be a kinetically controlled phenomena and is, therefore, unavoidable at elevated temperatures.

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Here we show the first observation of an unusual intermolecular magnetic interaction in the liquid-crystalline (LC) state of an all-organic radical compound at 73 C on water; the magnetic interaction actually allows the LC droplet on water to be attracted by a weak permanent magnet, whereas the crystalline phase did not respond to the magnet.

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Paramagnetic, calamitic, chiral liquid crystals (LCs) have attracted great interest due to their following characteristics: i) unwinding of the helical superstructure of chiral smectic C (SmC*) and cholesteric (N*) phases upon the application of weak magnetic fields; [1] ii) expected orientation control of ferroelectric liquid crystals (FLCs) by the application of weak magnetic fields, making use of the magnetoelectric effect, i.e., the influence of the internal electric field on the magnetic properties and vice versa; [2][3][4] and iii) the direct observation and characterization of microscopic molecular movement in FLCs (and SmC* phases), as well as in N* phases, by electron paramagnetic resonance (EPR) spectroscopy. We have been particularly interested in the observation of magnetoelectric interactions in paramagnetic FLCs, which may lead to an increase in the molecular paramagnetic susceptibility anisotropy (Dv para ), and thereby may enable the orientation control of FLCs by weak magnetic fields. [2][3][4] Thus far, several ferroelectric and paramagnetic chiral metallomesogens (SmC*) have been prepared. However, the intrinsic high viscosity of these molecules, brought about by the ligand-coordinated metal-complex structure, results in a slow response or no response to applied electric fields, and seems to render their orientation control by weak magnetic fields difficult, even in bulk mesophases. [5,6] With a view to obtaining a series of paramagnetic, all-organic, calamitic chiral mesogens that exhibit stable LC phases with low viscosity, we have successfully prepared prototype LC materials 1a-d containing a chiral five-membered cyclic nitroxide unit within the rigid core (Scheme 1). These molecules show a N or N* phase over a wide temperature range between 60 and 100°C. [7] It is noteworthy that the orientation of the N phases of 1a-d can be affected by a very weak magnetic field of 0.05 T or less during both the heating and cooling processes. Here, we report that enantiomerically enriched compounds 2a-e with longer side chains show desired SmC* (and N*) phases which are thermally stable over a wide temperature range between 50 and 90°C (Scheme 1). The spontaneous polarization and the optical response time of bistable switching upon the application of an electric field have been measured and evaluated for these chiral LC materials, along with their tilt angle. The C 1 -symmetric (2S,5S)-2,5-dimethyl-2-alkoxyphenyl-5-[4-(4-alkoxybenzenecarbonyloxy)phenyl]pyrrolidine-1-oxy derivatives 2a-e exhibit LC phases; (2S,5S)-2a shows the monotropic SmC* phase upon cooling from the isotropic (I) phase, (2S,5S)-2b,c show enantiotropic SmC* and N* phases, and (2S,5S)-2d,e only show an enantiotropic SmC* phase ( Fig. 1 and Table 1). Upon observation by hot-stage polarizing microscopy, the SmC* phases typically show a Schlieren texture with fourfold brushes under homeotropic boundary conditions, and a broken fan-shaped texture in a thin sandwich cell (4 lm thickness) under homogeneous planar boundary conditions (Figs...

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